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Summary Age-related clonal hematopoiesis is a major risk factor for myeloid malignancy and myeloid skewing is a hallmark of aging. However, while it is known that non-cell-autonomous components of the microenvironment can also influence this risk, there have been few studies of how the spatial architecture of human bone marrow (BM) changes with aging. Here, we show that BM adiposity increases with age, which correlates with increased density of maturing myeloid cells and CD34+ hematopoietic stem/progenitor cells (HSPCs) and an increased proportion of HSPCs adjacent to adipocytes. However, NGFR+ bone marrow stromal cell (NGFR+ BMSC) density and distance to HSPCs and vessels remained stable. Interestingly, we found that, upon aging, maturing myeloid cell density increases in hematopoietic areas surrounding adipocytes. We propose that increased adjacency to adipocytes in the BM microenvironment may influence myeloid skewing of aging HSPCs, contributing to age-related risk of myeloid malignancies., Highlights • Aging increases adipose, myeloid, and CD34+ HSPC density in the human bone marrow • Human CD34+ HSPC niche is reticular, perivascular, and periadipocytic in aging • Aging increases maturing myeloid cell density surrounding adipocytes, In this article, Dick, Flores-Figueroa, and colleagues show that aging alters the spatial organization between CD34+ hematopoietic stem/progenitor cells and adipocytes within human bone marrow. An increased mature myeloid output correlates with these findings, raising the idea that these age-related changes may influence myeloid skewing and the accompanying risk of myeloid malignancy.

Mass cytometry (MC) is a bioanalytical technique that uses metal-tagged antibodies (Abs) for high-dimensional single-cell immunoassays. Currently, this technology can measure over 40 parameters simultaneously on individual cells using metal-chelating polymer (MCP) based reagents. However, MC can in principle detect up to 135 parameters with the development of new elemental mass tags. Here we report the development of a tantalum oxide nanoparticle (NP)-based mass tag for MC immunoassays. Uniform-sized amine-functionalized tantalum oxide NPs (d ∼ 5.7 nm) were synthesized via a one-pot two-step reverse microemulsion method. These amine-functionalized NPs were further modified with azide groups by reacting with azide-PEG2k succinimidyl carboxymethyl ester (NHS-PEG2k-N3) cross-linkers. The Ab-NP conjugates were prepared by reacting azide-functionalized NPs with dibenzocyclooctyne (DBCO)-functionalized primary or secondary Abs (DBCO-Ab) followed by fast protein size exclusion liquid chromatography (FPLC) purification. Three Ab-NP conjugates (TaO2-PEG2k-goat antimouse, TaO2-PEG2k-CD25, TaO2-PEG2k-CD196) were fabricated and tested in MC immunoassays. For the TaO2-PEG2k-goat antimouse conjugate, we showed that it can effectively detect abundant CD20 biomarkers on Ramos cells. For TaO2-PEG2k-CD25 and TaO2-PEG2k-CD196 conjugates, we demonstrated that these Ab-NP conjugates could be integrated into the commercial Ab staining panels for high-dimensional single-cell immune profiling of human peripheral blood mononuclear cells.

We employ imaging mass cytometry (IMC) to investigate in vitro uptake and cellular distribution of DNA-functionalized gold nanoparticles (AuNPs). IMC enables the multiparametric imaging of cell components and allows for the detection of AuNPs in cells with100 times higher sensitivity than conventional confocal fluorescence imaging, as each nanoparticle contains thousands of atoms for signal amplification. Changes in the accumulation of nanoparticles in cells due to oligonucleotide sequence-dependent interactions are exploited to examine a model biomarker for hypoxia-microRNA-210. We find that AuNPs functionalized with microRNA-210-targeting sequence accumulate in hypoxic cells 3 to 4-fold compared to normoxic cells. The work examines the potential use of DNA-AuNP as high-mass probes for the analysis of nonabundant nucleic acids.

In pharmaceutical research, high-content screening is an integral part of lead candidate development. Measuring drug response in vitro by examining over 40 parameters, including biomarkers, signaling molecules, cell morphological changes, proliferation indices, and toxicity in a single sample, could significantly enhance discovery of new therapeutics. As a proof of concept, we present here a workflow for multidimensional Imaging Mass Cytometry™ (IMC™) and data processing with open source computational tools. CellProfiler was used to identify single cells through establishing cellular boundaries, followed by histoCAT™ (histology topography cytometry analysis toolbox) for extracting single-cell quantitative information visualized as t-SNE plots and heatmaps. Human breast cancer-derived cell lines SKBR3, HCC1143, and MCF-7 were screened for expression of cellular markers to generate digital images with a resolution comparable to conventional fluorescence microscopy. Predicted pharmacodynamic effects were measured in MCF-7 cells dosed with three target-specific compounds: growth stimulatory EGF, microtubule depolymerization agent nocodazole, and genotoxic chemotherapeutic drug etoposide. We show strong pairwise correlation between nuclear markers pHistone3S28 , Ki-67, and p4E-BP1T37/T46 in classified mitotic cells and anticorrelation with cell surface markers. Our study demonstrates that IMC data expand the number of measured parameters in single cells and brings higher-dimension analysis to the field of cell-based screening in early lead compound discovery.

Mass cytometry (MC) is a high throughput multiparameter analytical technique for determining biomarker expression in cells., Mass cytometry (MC) is a high throughput multiparameter analytical technique for determining biomarker expression in cells. In MC, antibodies (Abs) are tagged with heavy metal isotopes via conjugation to metal chelating polymers (MCPs). To improve the sensitivity of MC towards low abundance biomarkers, we are developing nanoparticle (NP)-based reagents as mass tags for Abs. We examine the use of silica-coated NaHoF4 NPs (d ∼ 12 nm) decorated with PEG5k conjugated to thiol-modified primary or secondary Abs for MC assays. We compare the sensitivity of NP–Ab conjugates to MCP–Ab conjugates towards seven biomarkers with varying expression levels across six cell lines. We also perform a multi-parameter assay using a cocktail of both NP- and MCP-based reagents to detect seven cellular markers in peripheral blood mononuclear cells (PBMCs). In the case of highly abundant markers, signal enhancements from NP–Ab conjugates offer minimal advantages over MCP–Ab conjugates, which already give strong signals. In the case of biomarkers with lower abundance, the level of signal enhancements depended on the nature of the biomarker being detected, or on the type of detection method used. When comparing the indirect detection of CD14 on THP-1 cells using NPs or MCPs conjugated to secondary Abs, the NP reagents offered little signal enhancements compared to the MCP reagents. However, in the case of direct CD14 detection on THP-1 or U937 cells using NPs or MCPs conjugated to primary Abs, a 30- or 450-fold signal enhancement was seen from the NP-based reagent. In the experiments where both NP–Ab and MCP–Ab conjugates were used together to stain PBMCs, we found that the presence of the NP–Ab conjugates did not affect the function of MCP–Ab conjugates, and the NP–Ab conjugates showed minimal non-specific interaction with cells without the target biomarker (CD14). Furthermore, these NP–Ab conjugates could be used to identify rare CD14+ monocytes from the PBMC mixture with a 20-fold signal increase when compared to the use of only MCP–Ab conjugates. Collectively, the strong signal amplification obtained from NP reagents demonstrate the potential of these reagents to be used in conjunction with MCP-reagents to detect rare cellular markers or cell types that may otherwise be overlooked when using MCP-reagents alone.

A metal containing polymer (MCP) based on a polylysine functionalized by In(III) chelates was synthesized. The chelator is based on a constrained dipicolinate cyclam that forms a highly inert In(III) complex. The MCP was conjugated to anti CD20 antibody using the very strong neutravidin/biotin interaction. Two cell lines, one expressing CD20 the other not, were stained with the modified antibody and analysed by mass cytometry using the In-115 channel. The results showed a specific antigen-antibody recognition and images by mass cytometry imaging could be obtained thanks to In-115 detection. Finally, overtime stability tests of the bioconjugate as well as multiplex experiments using the In-115 channel underline the high potentiel of this new In based MCP.

Mass cytometry is a highly multiplexed single-cell analysis platform that uses metal-tagged reagents to identify multiple cellular biomarkers. The current metal-tagged reagent preparation employs thiol–maleimide chemistry to covalently couple maleimide-functionalized metal-chelating polymers (MCPs) with antibodies (Abs), a process that requires partial reduction of the Ab to form reactive thiol groups. However, some classes of Abs (for example, IgM) as well as biomolecules lacking cysteine residues have been challenging to label using this method. This inherent limitation led us to develop a new conjugation strategy for labeling a wide range of biomolecules and affinity reagents. In this report, we present a metal tagging approach using a new class of azide- or transcyclooctene-terminated MCPs with copper(I)-free strain-promoted alkyne–azide cycloaddition or tetrazine–alkene click chemistry reactions, in which biomolecules with -NH2 functional groups are selectively activated with a dibenzocyclooctyne or ...

Mass cytometry is a novel cell-by-cell analysis technique, which uses elemental tags instead of fluorophores. Sample cells undergo rapid ionization in inductively coupled plasma and the ionized elemental tags are then analyzed by means of time-of-flight mass spectrometry. Benefits of the mass cytometry approach are in no need for compensation, the high number of detection channels (up to 100) and low background noise. In this work, we applied a biotinylated aptamer against human PTK7 receptor for characterization of positive (human acute lymphoblastic leukemia) and negative (human Burkitt's lymphoma) cells by a mass cytometry instrument. Our proof of principal experiments showed that biotinylated aptamers in conjunction with metal-labeled neutravidin can be successfully utilized for mass cytometry experiments at par with commercially available antibodies. Graphical abstract Biotinylated aptamers in conjunction with metal-labeled neutravidin bind to cell biomarkers, and then injected into the inductively coupled plasma (ICP) source, where cells are vaporized, atomized, and ionized in the plasma for subsequent mass spectrometry (MS) analysis of lanthanide metals.

Mass cytometry uniquely enables high-dimensional single-cell analysis of complex populations. This recently developed technology is based on inductively coupled time-of-flight mass spectrometry for multiplex proteomic analysis of more than 40 markers per cell. The ability to characterize the transcriptome is critical for the understanding of disease pathophysiology, medical diagnostics, and drug discovery. Current techniques allowing the in situ detection of transcripts in single cells are limited to a small number of simultaneous targets and are generally tedious and labor-intensive. In this report, we present the development of a multiplex method for targeted RNA detection by combining the mass cytometry and RNAscope® platforms. This novel assay, called Metal In Situ Hybridization (MISH), includes the hybridization of RNA-specific target probes followed by signal amplification achieved through a cascade of hybridization events, ending with the binding of amplifier-specific detector probes. The detector probes are tagged with isotopically pure metal atoms used for detection by mass cytometry. Proof-of-principle experiments show the simultaneous detection of three mRNA targets in Jurkat cells in suspension cell assay mode. The localization of transcripts was also investigated using the imaging mass cytometry platform in Jurkat and KG-1a cells. In addition, we optimized the antibody staining procedure to allow the co-detection of mRNA and cell surface markers. Our data demonstrate that MISH can be used to complement protein detection by mass cytometry as well as to investigate gene transcription and translation in single cells. © 2017 International Society for Advancement of Cytometry.

We are interested in developing lanthanide nanoparticles (NPs) as high sensitivity tagging reagents for antibodies to analyze cells by mass cytometry (MC). Two key prerequisites for this application are that the NPs have to be colloidally stable in phosphate-containing buffers and the free NPs must have very low levels of nonspecific binding to cells. These are the issues we address here. We describe the synthesis of 30 nm diameter NaYF4:Yb,Er nanoparticles, their transfer to aqueous solution via citrate exchange, and their encapsulation in liposomes to minimize their interaction with live cells. The lipid coating consisted of a 2:2:1 mol ratio mixture of dioleoylphosphatidyl choline (DOPC), egg sphingomyelin (ESM), and ovine cholesterol (Chol), referred to as DEC221. Since encapsulating 30 nm NPs in liposomes is an unprecedented challenge, we added varying amounts of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxyPEG-2000] (mPEG2K-DSPE) to the lipid formulation, both to promote curvature of th...

The synthesis of a polylysine polymer functionalized with the previously reported astonishingly inert [In(cb-te2pa)]+ chelate was performed. A biotin end group allowed the conjugation to biotinylated beads by the intermediary of a fluorescein isothiocyanate/neutravidin receptor. High quality imaging mass cytometry trials, based on 115In detection were performed to highlight the behavior of the material. Anti-CD20 antibody was labeled by the so-obtained In(III)-modified polylysine using the biotin/neutravidin interaction. Ramos (CD20[+]) and HL-60 (CD20[-]) cell lines were costained with the In(III)-modified bioconjugate by finding the best staining conditions. Both immunofluorescence microscopy (IF-M) and mass cytometry analyses confirmed the specific binding of anti-CD20 onto Ramos cells. CyTOF histograms constructed on the 115In detection allowed us to define and to separate, with a good signal-to-noise ratio, two populations (Ramos and HL-60). The inertness of In(III)-MCP-NAv over a three-month storage period was proved by performing new functionality tests involving Jurkat cells (CD20[-]) and multiparametric trials involving the 115In channel. The results ensure a promising future use of the previously announced [In(cb-te2pa)]+ complex-based polymers for mass cytometry.

Multiple sclerosis (MS) is characterized by demyelinated and inflammatory lesions in the brain and spinal cord that are highly variable in terms of cellular content. Here, we used imaging mass cytometry (IMC) to enable the simultaneous imaging of 15+ proteins within staged MS lesions. To test the potential for IMC to discriminate between different types of lesions, we selected a case with severe rebound MS disease activity after natalizumab cessation. With post-acquisition analysis pipelines we were able to: (1) Discriminate demyelinating macrophages from the resident microglial pool; (2) Determine which types of lymphocytes reside closest to blood vessels; (3) Identify multiple subsets of T and B cells, and (4) Ascertain dynamics of T cell phenotypes vis-à-vis lesion type and location. We propose that IMC will enable a comprehensive analysis of single-cell phenotypes, their functional states and cell-cell interactions in relation to lesion morphometry and demyelinating activity in MS patients., eLife digest It takes an army of immune cells to defend the body against infection. But sometimes the body’s immune system mistakenly attacks its own cells and chronic inflammatory conditions develop. In multiple sclerosis – also known as “MS” – a horde of immune cells infiltrate the brain and spinal cord, forming lesions which strip nerve cells of their insultation, a protective fatty material called myelin. Nerve cells become damaged, scarred and exposed, and this interferes with messages between the brain and other parts of the body. Advanced imaging techniques have revolutionized the diagnosis of multiple sclerosis by capturing lesions as they develop in the brain and spinal cord. Researchers have also focused their efforts on understanding how immune cells activated in the blood stream invade the central nervous system. To better understand how a mistaken immune response leads to nerve damage in multiple sclerosis, a forensic examination of which immune cells accumulate in brain tissue to form lesions is needed. Standard techniques for analyzing whole tissue samples are however limited by design, capable of detecting only a few cell markers in one section of tissue. Ramaglia et al. have now validated a new imaging technique for looking at an array of cell types in brain tissue in a single sample. The technique – called imaging mass cytometry (or IMC for short) – was used to look at post-mortem brain tissue from a multiple sclerosis patient with an acute form of the illness. The tissue examined had multiple sclerosis lesions present. Different types of immune cells were simultaneously identified and characterized using a panel of antibodies which recognize the signature proteins each immune cell makes when active. The state of the underlying myelin content of the tissue was also characterized. The imaging approach could distinguish between the immune cells of the brain (known as resident microglia) and a type of white blood cell summoned as part of the immune response (infiltrating macrophages). The analysis showed that, in the particular patient examined, microglia are abundant in active lesions in multiple sclerosis; also, different subsets of white blood cells were detected. Measuring how far different immune cells had migrated from nearby blood vessels added insights as to how immune cells move through the brain and which cells may have arrived first. Altogether, Ramaglia et al. have shown that IMC can be used as a discovery tool to gain a deeper understanding of multiple sclerosis lesions and immune cells active in the inflamed brain. Further work will apply this now validated imaging approach to large cohorts of multiple sclerosis patients.

Which antigen-presenting cells are involved in Tfh responses in humans remains unclear. Durand et al. show that human tonsil cDC2 and CD14+ macrophages provide Tfh polarizing signals to CD4+ T cells in distinct locations within tonsil, playing sequential roles in Tfh induction., CD4+ T follicular helper (Tfh) cells are essential for inducing efficient humoral responses. T helper polarization is classically orientated by dendritic cells (DCs), which are composed of several subpopulations with distinct functions. Whether human DC subsets display functional specialization for Tfh polarization remains unclear. Here we find that tonsil cDC2 and CD14+ macrophages are the best inducers of Tfh polarization. This ability is intrinsic to the cDC2 lineage but tissue dependent for macrophages. We further show that human Tfh cells comprise two effector states producing either IL-21 or CXCL13. Distinct mechanisms drive the production of Tfh effector molecules, involving IL-12p70 for IL-21 and activin A and TGFβ for CXCL13. Finally, using imaging mass cytometry, we find that tonsil CD14+ macrophages localize in situ in the B cell follicles, where they can interact with Tfh cells. Our results indicate that human lymphoid organ cDC2 and macrophages play complementary roles in the induction of Tfh responses., Graphical Abstract

Multiple Sclerosis (MS) is characterized by demyelinated and inflammatory lesions in the brain and spinal cord. Lesions contain immune cells with variable phenotypes and functions. Here we use imaging mass cytometry (IMC) to enable the simultaneous imaging of 15+ proteins within 11 staged MS lesions. Using this approach, we demonstrated that the majority of demyelinating macrophage-like cells in active lesions were derived from the resident microglial pool. Although CD8+ T cells predominantly infiltrated the lesions, CD4+ T cells were also abundant but localized closer to blood vessels. B cells with a predominant switched memory phenotype were enriched across all lesion stages and were found to preferentially infiltrate the tissue as compared to unswitched B cells which localized to the vasculature. We propose that IMC will enable a comprehensive analysis of single-cell phenotypes, their functional states and cell-cell interactions in relation to lesion morphometry and demyelinating activity in the MS brain.

International audience; H2cb‐te2pa, a cross‐bridged cyclam functionalized by two picolinate arms, was used for the formation of an incredible inert In(III) chelate. For the first time a bifunctional analogue of H2cb‐te2pa was prepared by C‐functionalization to keep its coordination properties intact. However, this strategy leads to the formation of two diastereoisomers, as evidenced and studied by NMR experiments and DFT calculations. Kinetic studies proved nevertheless that both isomers of the complex are equally inert; they were therefore used without distinction for their covalent grafting on polystyrene beads. The so‐called metal‐encoded beads were tested for Imaging Mass Cytometry. The detection of 115In allows the generation of images with high quality, proving the great potential of the bifunctional [In(cb‐te2pa)]+ derivatives for single‐cell analysis by mass cytometry.; H2cb-te2pa, un cyclam renforcé fonctionnalisé par deux bras picolinate, a été utilisé pour la formation d'un chélate d’indium(III) incroyablement inerte. Pour la première fois, un analogue bifonctionnel de H2cb-te2pa a été préparé par C-fonctionnalisation pour conserver ses propriétés de coordination intactes. Cependant, cette stratégie conduit à la formation de deux diastéréoisomères, comme en témoignent les expériences de RMN et les calculs de DFT. Les études cinétiques ont néanmoins prouvé que les deux isomères du complexe étaient également inertes; ils ont donc été utilisés sans distinction pour leur greffage covalent sur des billes de polystyrène. Les billes obtenues ont été testées pour l’imagerie par cytométrie de masse. La détection de l’115In permet de générer des images de haute qualité, prouvant ainsi le potentiel des dérivés bifonctionnels [In (cb-te2pa)]+ pour l'analyse monocellulaire par cytométrie de masse.

This unit describes protocols for labeling tissue sections using combinations of metal-tagged antibodies and an iridium-containing DNA intercalator for analysis by imaging mass cytometry. Imaging mass cytometry (IMC) allows the labeling of up to 40 individual markers simultaneously using antibody cocktails. We discuss labeling of both cryostat sections and sections from formalin-fixed, paraffin-embedded (FFPE) tissue blocks. The protocols are similar to those used for optical microscopy techniques, while allowing much higher complexity of analysis. © 2017 by John Wiley & Sons, Inc. Keywords: antibodies; FFPE; imaging mass cytometry; mass cytometry; proliferation

Mass cytometry uniquely enables high-dimensional single-cell analysis of complex populations. This recently developed technology is based on inductively coupled time-of-flight mass spectrometry for multiplex proteomic analysis of more than 40 markers per cell. The ability to characterize the transcriptome is critical for the understanding of disease pathophysiology, medical diagnostics, and drug discovery. Current techniques allowing the in situ detection of transcripts in single cells are limited to a small number of simultaneous targets and are generally tedious and labor-intensive. In this report, we present the development of a multiplex method for targeted RNA detection by combining the mass cytometry and RNAscope® platforms. This novel assay, called Metal In Situ Hybridization (MISH), includes the hybridization of RNA-specific target probes followed by signal amplification achieved through a cascade of hybridization events, ending with the binding of amplifier-specific detector probes. The detector probes are tagged with isotopically pure metal atoms used for detection by mass cytometry. Proof-of-principle experiments show the simultaneous detection of three mRNA targets in Jurkat cells in suspension cell assay mode. The localization of transcripts was also investigated using the imaging mass cytometry platform in Jurkat and KG-1a cells. In addition, we optimized the antibody staining procedure to allow the co-detection of mRNA and cell surface markers. Our data demonstrate that MISH can be used to complement protein detection by mass cytometry as well as to investigate gene transcription and translation in single cells. © 2017 International Society for Advancement of Cytometry.

Although of fundamental importance to the treatment of cancer patients, the quantitative study of drug distribution and action in vivo at the single cell level is challenging. We used the recently-developed technique of mass cytometry to measure cisplatin uptake into individual tumor cells (Pt atoms/cell), combined with measurement of the rate of IdU incorporation into DNA (I(127) atoms/cell/min) and tumor hypoxia identified by the 2-nitroimidazole EF5 in cisplatin-treated BxPC-3 and ME-180 xenografts. Pt levels of 10(5) to 10(6) atoms/cell were obtained following a single cisplatin treatment using clinically relevant doses. Cisplatin caused cell cycle arrest in a dose- and time-dependent manner that paralleled effects in vitro, and it readily penetrated into hypoxic tumor regions. Similar levels of Pt/cell were found in xenografts treated with oxaliplatin. Mass cytometry offers the unique capability to study the cellular uptake and anticancer effects of platinum-containing drugs at the single cell level in animal models, and it has the potential for application to samples obtained from cancer patients during treatment.

Mass cytometry (MC) uses antibodies (Abs) labeled with heavy metal isotopes to monitor biomarker expression on individual cells. Metal-chelating polymers (MCPs) conjugated to the Abs increase the number of metal ions carried per Ab, and this increases the signal generated per Ab. Although the MC detector can detect 134 metal isotopes with unique weight simultaneously, in the current literature a maximum of 43 isotopes have been analyzed simultaneously. Currently available MCPs for MC are well-suited for use with lanthanides and bismuth, but are incompatible with other metals of interest. Here we examine a new MCP with deferoxamine pendant groups designed to chelate Zr ions. Zr has 4 isotopes useful for MC. To overcome the limited water solubility of deferoxamine groups, we introduced pendant polyethylene glycol chains. The polymer also included fluorescein pendant groups, along with a biotin terminal end-group. Once loaded with Zr, the polymers were incubated with streptavidin-coated polystyrene microbead and analyzed using epifluorescence microscopy and imaging MC.

Immune monitoring is an essential method for quantifying changes in immune cell population numbers and states over time in health and disease. A cornerstone in translational and clinical research, it is frequently used in the investigation of chronic inflammation, infectious disease, autoimmune diseases, and cancer. The diversity of immune cell populations demands a highparameter approach to more fully and efficiently quantify these changes. Mass cytometry, which utilizes CyTOF® technology, is a single-cell analysis platform that uses metal-tagged antibodies to resolve over 40 markers in a single tube of sample without the need for compensation. It is an ideal solution for routine enumeration of immune cell populations. However, development of a robust, highly multiplexed assay requires panel optimization as well as standardization of instrument setup and an analysis pipeline. We have developed a sample-to-answer solution for human immune profiling using mass cytometry. It includes an optimized 30-marker immune profiling panel provided in a lyophilized, single-tube format, validated SOPs for human whole blood and PBMC staining, an instrument data acquisition template, instructions for data acquisition on a Helios™ system, and automated software for data analysis. The software analyzes FCS 3.0 files generated with the kit; automatically reports cell counts, percentage calculations, and staining intensity; and produces graphical elements such as histograms, dot plots, and a Cen-se′™ (t-SNE variant) graph for 36 immune cell populations. Here we present assay analytical validation data on repeatability, reproducibility, software precision, and software accuracy. We also present a performance comparison of the lyophilized material and a liquid formulation of the same antibodies and clones used in the lyophilized format. This assay provides a robust, complete solution for broad immune profiling using mass cytometry that reduces sources of variability and subjectivity in sample preparation and data analysis. Citation Format: Stephen K. Li, Daniel Majonis, C. Bruce Bagwell, Benjamin C. Hunsberger, Vladimir I. Baranov, Olga I. Ornatsky. A robust human immune profiling assay using CyTOF technology and automated data analysis software [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1667.

Mass cytometry, which utilizes CyTOF® technology, is a single-cell analysis platform that uses metal-tagged antibodies. An advantage of CyTOF is its ability to resolve more than 40 parameters in a single panel without the need for compensation, making mass cytometry an ideal solution for routine enumeration of immune cells. Developing a robust and highly multiplexed assay requires an optimized panel and analysis pipeline, and the analysis of complex panels is time-consuming and difficult to interpret without expertise in immunology. The Maxpar® Direct Immune Profiling Assay™ coupled with Maxpar Pathsetter™ software is a sample-to-answer solution for human immune profiling using mass cytometry. The Maxpar Direct Immune Profiling Assay kit includes an optimized 30-marker panel contained in a lyophilized single-tube format, protocols for human whole blood and PBMC staining, and data acquisition instructions on a Helios™ system. Maxpar Pathsetter is an automated software that accepts FCS 3.0 files and reports cell counts, percentage calculations, and staining intensity. It also produces graphical elements such as histograms, dot plots, and a Cen-se’™ (t-SNE variant) graph for 36 immune cell populations. We present analytical validation data on repeatability and reproducibility for the assay and on the precision and accuracy of Maxpar Pathsetter software. We demonstrate comparative performance between the lyophilized panel and a liquid panel of the same antibodies. Coupling Maxpar Pathsetter software with the Maxpar Direct Immune Profiling Assay reduces variability in sample preparation and subjectivity in data analysis. It allows researchers to have a streamlined solution for broad immune profiling using mass cytometry.

We describe the synthesis and characterization of a family of poly(N-alkylacrylamide) polymers carrying 2-6 fluorescent dye molecules, ∼70 pendant DTPA (diethylenetriaminepentaacetic acid) groups, and an orthogonal maleimide end-group for covalent attachment to an antibody (Ab). These dual-purpose labels were designed for use in multiplexed immunoassays based on both mass cytometry and fluorescent flow cytometry. A challenge in the polymer synthesis was finding conditions for attaching a sufficient number of dye molecules to each polymer chain. Although attachment of a terminal maleimide to the polymers was not as efficient as anticipated, the end-functional polymers were still effective in labeling Abs. Secondary goat antimouse IgG was labeled with the four dual-label polymers as well as a control polymer, and while the resultant antibody-polymer conjugates showed positive performance in mass cytometric and fluorescent assays, some trials showed problems such as low signal and nonspecific adsorption. Four primary antibody conjugates were prepared and used to stain cells in 4-plex assays. The results of both primary assays are bittersweet in that the CD3-FITC and CD45-DyLight 649 conjugates performed well, while the CD13-DyLight 405 and the CD38-DyLight 549 conjugates did not.

Imaging Mass Cytometry (IMC) is an expansion of mass cytometry, but rather than analyzing single cells in suspension, it uses laser ablation to generate plumes of particles that are carried to the mass cytometer by a stream of inert gas. Images reconstructed from tissue sections scanned by IMC have a resolution comparable to light microscopy, with the high content of mass cytometry enabled through the use of isotopically labeled probes and ICP-MS detection. Importantly, IMC can be performed on paraffin-embedded tissue sections, so can be applied to the retrospective analysis of patient cohorts whose outcome is known, and eventually to personalized medicine. Since the original description in 2014, IMC has evolved rapidly into a commercial instrument of unprecedented power for the analysis of histological sections. In this Review, we discuss the underlying principles of this new technology, and outline emerging applications of IMC in the analysis of normal and pathological tissues. © 2017 International Society for Advancement of Cytometry.

To transform the linear fluorescence intensity scale obtained with fluorescent microspheres to an antibody bound per cell (ABC) scale, a biological cell reference material is needed. Optimally, this material should have a reproducible and tight ABC value for the expression of a known clinical reference biomarker. In this study, we characterized commercially available cryopreserved peripheral blood mononuclear cells (PBMCs) and two lyophilized PBMC preparations, Cyto-Trol and PBMC-National Institute for Biological Standard and Control (NIBSC) relative to freshly prepared PBMC and whole blood samples. It was found that the ABC values for CD4 expression on cryopreserved PBMC were consistent with those of freshly obtained PBMC and whole blood samples. By comparison, the ABC value for CD4 expression on Cyto-Trol is lower and the value on PBMC-NIBSC is much lower than those of freshly prepared cell samples using both conventional flow cytometry and CyTOF™ mass cytometry. By performing simultaneous surface and intracellular staining measurements on these two cell samples, we found that both cell membranes are mostly intact. Moreover, CD4(+) cell diameters from both lyophilized cell preparations are smaller than those of PBMC and whole blood. This could result in steric interference in antibody binding to the lyophilized cells. Further investigation of the fixation effect on the detected CD4 expression suggests that the very low ABC value obtained for CD4(+) cells from lyophilized PBMC-NIBSC is largely due to paraformaldehyde fixation; this significantly decreases available antibody binding sites. This study provides confirmation that the results obtained from the newly developed mass cytometry are directly comparable to the results from conventional flow cytometry when both methods are standardized using the same ABC approach.

We describe the synthesis of metal-chelating polymers (MCPs) with four different pendant polyaminocarboxylate ligands (EDTA, DTPA, TTHA, DOTA) and an orthogonal end-group, either a fluorescein molecule or a bismaleimide linker for antibody attachment. Polymer characterization by a combination of (1)H NMR, UV/vis absorption measurements, and thermal gravimetric analysis (TGA) indicated that each chain of the fluorescein-terminated polymers contained one dye molecule. These polymer samples were loaded with three different types of lanthanide ions as well as palladium and platinum ions. The numbers of metal atoms per chain were determined by a combination of UV/vis and conventional ICP-MS measurements. The experiments with lanthanide ions demonstrated that a net anionic charge on the polymer is important for water solubility. These experiments also showed that at least one type of lanthanide ion (La(3+)) is capable of forming a bimetallic complex with pendant DTPA groups. Conditions were developed for loading these polymers with palladium and platinum ions. While these polymers could be conjugated to antibodies, the presence of Pd or Pt ions in the polymer interfered with the ability of the antibody to recognize its antigen. For example, a goat anti-mouse (secondary) antibody labeled with polymers that contain Pd or Pt no longer recognized a primary antibody in a sandwich assay. In mass cytometry assays, these Pd- or Pt-containing MCPs were very effective in recognizing dead cells and provide a new and robust assay for distinguishing live cells from dead cells.

CyTOF® mass cytometry is a highly multiplexed, single-cell analysis platform that uses metal-tagged antibodies. A significant advantage of this technology is its ability to resolve more than 30 markers in a single panel without the need for compensation. Nonetheless, a highly multiplexed panel requires optimization of antibody titers, full panel verification, sample preparation, data acquisition, and analysis. Preparation of a staining cocktail from 30 individual tubes may be prone to errors. Not only is data analysis time-consuming for complex panels, it is difficult to interpret without expertise in immunology. We have developed a lyophilized 30-plex immunphenotyping panel contained in a single tube, an efficient workflow, and an automated software solution for human whole blood analysis using mass cytometry. The panel focuses on T cell lineage while also capturing other relevant immune populations. Blood is added directly to the lyophilized antibody tube, followed by RBC lysis, wash, and fixation steps and finally data acquisition of stained samples on the Helios™ system. The dedicated software tool accepts FCS3.0 files and in under 10 minutes automatically generates reports on the number of live cells, percentage of specific cell populations, staining intensities, histograms, 2D dot plots, and tSNE graphs. The auto-calculated frequencies of populations are comparable to manual gating, with a validated correlation coefficient over 0.9. The panel and software tool enable researchers to streamline immunophenotyping of whole blood while accurately and reproducibly monitoring changes in immune cell subsets in patient samples.

Rapid, sensitive, and quantitative assays for proteases are important for drug development and in the diagnosis of disease. Here an assay for protease activity that uses inductively coupled plasma-mass spectrometry (ICP-MS) detection is described. Peptidic alpha-chymotrypsin substrates were synthesized containing a lanthanide ion chelate at the N terminus to provide a distinct elemental tag. A biotin label was appended to the C terminus of the peptide, allowing separation of uncleaved peptide from the enzymatic digestion. The enzyme activity was determined by quantifying the lanthanide ion signal of the peptide cleavage products by ICP-MS. Biotinylated substrates synthesized include Lu-DTPA-Asp-Leu-Leu-Val-Tyr approximately Asp-Lys(biotin) and Lu-DTPA-betaAla-betaAla-betaAla-betaAla-Gly-Ser-Ala-Tyr approximately Gly-Lys-Arg-Lys(biotin)-amide. Parallel assays with a commercially available fluorogenic substrate (Suc-AAPF-AMC) for alpha-chymotrypsin were performed for comparison. Using the ICP-MS assay, enzyme concentrations as low as 2pM could be readily detected, superior to the detection limit of an assay using the alpha-chymotrypsin fluorogenic substrate (Suc-AAPF-AMC). Furthermore, we demonstrated the use of this approach to detect chymotrypsin activity in HeLa cell lysates.

685 Background: Oxaliplatin plus fluorouracil (FOLFOX) is a standard treatment for CRC pts. One of the most common and dose-limiting side effects of oxaliplatin is PSN. The mechanism of this phenomenon is poorly understood. Previous studies suggested that higher serum platinum levels were related to more severe neuropathy in testicular cancer pts. Methods: CRC pts who completed adjuvant FOLFOX at least 6 months prior to enrollment are eligible. Baseline demographic and treatment information were collected. EORTC CIPN20 (with EORTC QLQ-C30) questionnaire was used for self-reported PSN symptom assessment. Peripheral blood samples were collected for total/free platinum concentrations using high-performance liquid chromatography with tandem mass spectrometry (HPLC/MS-MS). Skin biopsies were obtained from the lower leg of consented pts. Imaging mass cytometry (IMC) was used to visualize platinum deposition (195Pt) and intra-epidermal nerve fiber (IENF) (PGP9.5-154Sm) in formalin-fixed paraffin embedded (FFPE) skin biopsy samples stained with a metal-conjugated antibody cocktail. Results: Nine patients were enrolled. Median age was 51.8 yr (range: 34.5-69.4 yr); male/ female: 5/4; mean cumulative dose of oxaliplatin was 800.7 ± 188.2 mg/m2; median time from last dose of oxaliplatin to enrollment was 48 months (range: 7.2-65.6 months). The mean sensory score from CIPN20 was 15.4 ± 4.3 (range: 10-25). Platinum was undetectable in plasma samples collected from all 9 patients. In skin samples, IMC showed significant platinum depositions and IENF. Conclusions: Severity of PSN was not related to cumulative dose of oxaliplatin or interval from last dose of oxaliplatin. Although platinum was undetectable in plasma in these patients, platinum was readily detectable in skin biopsies up to 65.6 months post completion of FOLFOX. This is the first demonstration of platinum deposition in skin post oxaliplatin treatment and it provides a possible mechanism for oxaliplatin-induced PSN.

76 Background: Perioperative chemotherapy plus surgical resection is a standard of care for locally advanced gastric or gastroesophageal junction (GEJ) cancers. There is a wide range in tumor response following cisplatin-containing preoperative chemotherapy. We investigated the relationship between tumor platinum levels and pathological tumor responses in gastric or GEJ cancer patients following preoperative chemotherapy. Methods: Tumor and adjacent normal tissues were retrieved. Pathological responses were assessed per standard criteria. Tissue platinum concentrations were determined with high-performance liquid chromatography mass spectrometry. Platinum distribution in tissue components was evaluated with imaging mass cytometry. Tissue collagen content was evaluated using trichrome staining. Results: Ten patients were enrolled in this study. Nine patients received 3 cycles of preoperative chemotherapy and 1 received 2 cycles. The median cumulative cisplatin dose was 166.8 mg/m2 (range: 95.9–181.1 mg/m2). Surgery was performed at a median time of 49 days (range: 28–72 days) after the last cycle of chemotherapy. The mean platinum level in tumor tissue in patients with any response was 893 ± 460 pg, significantly higher than in those with no response [38.8 ± 8.8 pg (p = 0.007)]. The collagen content was significantly higher in patients with any response than in those with no response (37.4 ± 6.8% vs. 11.5 ± 8.6%, p < 0.05). Platinum preferentially bound to collagen. Conclusions: Platinum was detectable in surgical specimens up to 72 days after preoperative chemotherapy. Higher tumor platinum concentration correlated with improved pathological response. Collagen binding potentially explained the high interpatient variability in tumor platinum concentrations.

A novel instrument for real time analysis of individual biological cells or other microparticles is described. The instrument is based on inductively coupled plasma time-of-flight mass spectrometry and comprises a three-aperture plasma-vacuum interface, a dc quadrupole turning optics for decoupling ions from neutral components, an rf quadrupole ion guide discriminating against low-mass dominant plasma ions, a point-to-parallel focusing dc quadrupole doublet, an orthogonal acceleration reflectron analyzer, a discrete dynode fast ion detector, and an 8-bit 1 GHz digitizer. A high spectrum generation frequency of 76.8 kHz provides capability for collecting multiple spectra from each particle-induced transient ion cloud, typically of 200-300 micros duration. It is shown that the transients can be resolved and characterized individually at a peak frequency of 1100 particles per second. Design considerations and optimization data are presented. The figures of merit of the instrument are measured under standard inductively coupled plasma (ICP) operating conditions (3% cerium oxide ratio). At mass resolution (full width at half-maximum) M/DeltaM900 for m/z = 159, the sensitivity with a standard sample introduction system of1.4 x 10(8) ion counts per second per mg L(-1) of Tb and an abundance sensitivity of (6 x 10(-4))-(1.4 x 10(-3)) (trailing and leading masses, respectively) are shown. The mass range (m/z = 125-215) and abundance sensitivity are sufficient for elemental immunoassay with up to 60 distinct available elemental tags. When15 elemental tags are used, a higher sensitivity mode at lower resolution (M/DeltaM500) can be used, which provides2.4 x 10(8) cps per mg L(-1) of Tb, at (1.5 x 10(-3))-(5.0 x 10(-3)) abundance sensitivity. The real-time simultaneous detection of multiple isotopes from individual 1.8 microm polystyrene beads labeled with lanthanides is shown. A real time single cell 20 antigen expression assay of model cell lines and leukemia patient samples immuno-labeled with lanthanide-tagged antibodies is presented.

Lectins have been increasingly important in the study of glycoproteins. Here we report a glycoprofiling method based on the covalent attachment of metal-chelating polymers to lectins for use in an ICP-MS-based assays. The labeled lectins are able to distinguish between glycoproteins covalently attached to a microtiter plate and their binding can be directly quantified by ICP-MS. Since each conjugate contains a different lanthanide, the assays can be conducted in a single or multiplex fashion, and may be readily elaborated to many different assay formats.

We describe the preparation and thermal response of aqueous microgels based on poly(N-vinyl caprolactam) containing grafted poly(ethylene glycol) (PEG) chains. These microgels were synthesized by free radical copolymerization of vinyl caprolactam and acetoacetoxyethyl methacrylate in the presence of methoxy-capped poly(ethylene glycol)methacrylate macromonomers. We show that variation of the amount of PEG macromonomer or the length of the PEG chain provides effective control of the microgel diameter in the range 60–220 nm. The presence of the grafted PEG chains improves the colloidal stability of the microgels. The incorporation of the PEG macromonomers into microgel structure decreases the swelling degree and induces a shift of the volume phase transition to higher temperatures.

Various types of nanoobjects such as metal, semiconductor, and polymer particles, various types of hydrogels and polymer micelles have been incorporated into living cells. [1] Many of these experiments were directed to cell imaging or drug delivery whereas others were intended to introduce optical sensors into the cells.[2]

This paper describes the development and application of new metal-tagging reagents and a novel mass spectrometer (MS) detector for a flow cytometer that enables highly multiplexed measurement of many biomarkers in individual cells. A new class of tagging reagents, based on an acrylic polymer backbone that incorporates a reproducible number of lanthanide elements, has been developed. When linked to antibodies that specifically recognize target proteins of interest, determination of the tag elements is diagnostic for the presence and quantification of the antigen. The use of enriched stable isotope tags provides the opportunity for multiparametric assay. The new instrument uses inductively coupled plasma (ICP) to vaporize, atomize, and ionize individual cells that have been probed using the metal-labeled antibodies. The elemental composition, specifically of the metal tags, is recorded simultaneously using a time-of-flight (TOF)-MS that has been specifically designed for high-speed analysis during the short transient corresponding to the individual cell event. The detector provides for well-resolved atomic fingerprints of many elemental and isotopic tags, with little overlap of neighboring signals (high abundance sensitivity) and wide dynamic range both for a single antigen and between antigens.

To identify a rare (e.g., diseased or foreign) cell in a complex mixture, or to understand the proteomic complexity[1,2] of cells, one needs to be able to measure simultaneously and quantitatively a large number of proteins or other biomarkers that may be present in a complex sample. This is a difficult task and is beyond the reach of current capabilities. To address a problem of this complexity, we have begun to develop a high-sensitivity assay[3–6] based upon elemental tags that will enable the simultaneous measurement of many proteins in a single sample. The advantage of this approach lies in the large number of available elements and isotopes (potentially greater than 79) found in low abundance in biological systems, which will allow multiple tags to be used simultaneously. Inductively coupled plasma mass spectrometry (ICP-MS) is an ideal technique for detecting and quantifying these tags, as ICP-MS provides excellent resolution between the tag masses and an exceptional dynamic range (nine orders of magnitude).[7] This method allows one to overcome some of the limitations of currently available fluorescent tagging approaches.[8] These limitations arise from the spectral overlap of different dyes and the difficulty in measuring simultaneously targets that differ in abundance by an order of magnitude or more. Other benefits of ICP-MS detection include the high sensitivity, which is comparable to that of radioimmunoassays or chemiluminescent assays,[3] insensitivity of elemental tags to photobleaching and storage time, as well as the stability of the tagged sample so that it can be stored or shipped for analysis. We discuss herein the development of a new class of elemental tags for ICP-MS detection and their use for tagging of antibodies chosen to allow specific recognition of distinguishing cell surface markers. By using this technique it should be possible to achieve detection limits on the order of parts per billion, which will allow the detection of cell surface markers with copy numbers as low as 100.

Recent progress in the development of massively multiplexed bioanalytical assays using element tags with inductively coupled plasma mass spectrometry detection is reviewed. Feasibility results using commercially available secondary immunolabeling reagents for leukemic cell lines are presented. Multiplex analysis of higher order is shown with first generation tag reagents based on functionalized carriers that bind lanthanide ions. DNA quantification using metallointercalation allows for cell enumeration or mitotic state differentiation. In situ hybridization permits the determination of cellular RNA. The results provide a feasibility basis for the development of a multivariate assay tool for individual cell analysis based on inductively coupled plasma mass spectrometry in a cytometer configuration.

There is a great need in cell biology for the simultaneous detection of many intracellular and extracellular proteins within single cells. Current optical methods based on fluorescence activated flow cytometry are difficult to multiplex. We have developed a novel application of ICP-MS-linked metal-tagged immunophenotyping which has great potential for highly multiplexed proteomic analysis. Expression of intracellular oncogenic kinase BCR/Abl, myeloid cell surface antigen CD33, human stem cell factor receptor c-Kit and integrin receptor VLA-4 were investigated using model human leukemia cell lines. Antigens to which specific antibodies are available and are distinguishably tagged can be determined simultaneously, or multiplexed. Four commercially available tags (Au, Sm, Eu, and Tb) conjugated to secondary antibodies enable a 4-plex assay assuming that the primary antibodies are not cross-reactive. Results obtained by ICP-MS were compared with data from FACS. ICP-MS as an analytical detector possesses several advantages that enhance the performance of immunoassays, which are discussed in detail. Although multiplexing using metal-conjugated reagents is in a very early stage of research and feasibility studies, it is already apparent that more than four antigens could be accurately detected simultaneously using the ICP-MS instrument.

An in-depth study of the reproducibility of data acquired for comparative proteomics analysis using a prototype two-stage heated laminar flow chamber fitted to a commercial high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) instrument was undertaken. The study is based on 24 replicate samples from four independent membrane preparations derived from two matched breast cancer cell lines. Variation and reproducibility in the data were evaluated at several levels highlighting the relative efficiency and variability of the acquisition routines used. Specifically, variation in the number and relative intensities of chromatographic peaks eluted from the LC column, precursor ion selection and sequence identification were evaluated. On average, approximately 6500 chromatographic peaks were generated for each acquisition with a corresponding coefficient of variance (CV) of less than 20%. Precursor ion selection and sequence identification averaged 1380 and 780 events per acquisition sample, respectively, with corresponding CVs of less than 10% for each. The reproducibility in the precursor ion selection was typically better than 60% between similar replicates. Using protein and peptide internal standards, it was found that the CV in retention time across the gradient between two acquisition pairs was typically less than 5%, whereas the average intensity ratio was 1.0 (expected) with a CV approaching 20%. An evaluation of the intensity ratios calculated from endogenous peptide sequences, identified across the acquisition set, indicated a CV of ∼30%. Similarly, the CV associated with the top 1000 peptides indicated a mean and median of 28.4 and 26.95%. For a given acquisition pair it was also found that ∼11% of the chromatographic peaks eluting from the column were linked to a sequence or identified. For these experiments, less than 10% of the peak pairs had absolute ratios greater than 2.0 and of those only ∼10% had sequences linked to them. For each matched acquisition set on average 406 proteins were identified with a CV of less than 10%. Of the proteins that were identified approximately 30% had at least one predicted trans-membrane domain, indicating a four-fold increase over a crude homogenate sample with only minor enrichment. During these experiments it was found that the interface did not significantly alter the relative charge state distribution of ions, nor did it introduce significant interference from background ions. The interface was capable of 24-hour acquisition cycles. Copyright © 2004 John Wiley & Sons, Ltd.

The purpose of this phospho-proteomics study was to demonstrate the broad analysis of cellular protein phosphorylation in cells and tissue as a means to monitor changes in cellular states. As a cancer model, human tumor-derived A431 cells known to express the epidermal growth factor receptor (EGFR) were grown as cell cultures or xenograft tumors in mice. The cells and tumor-bearing animals were subjected to treatments including the EGFR-directed protein kinase inhibitor PK166 and/or EGF stimulation. Whole cell/tissue protein extracts were converted to peptides by using trypsin, and phosphorylated peptides were purified by an affinity capture method. Peptides and phosphorylation sites were characterized and quantified by using a combination of tandem mass spectroscopy (MS) and Fourier transform MS instrumentation (FTMS). By analyzing roughly 106 cell equivalents, 780 unique phosphopeptides from approx 450 different proteins were characterized. Only a small number of these phosphorylation sites have been described previously in literature. Although a targeted analysis of the EGFR pathway was not a specific aim of this study, 22 proteins known to be associated with EGFR signaling were identified. Fifty phosphopeptides were found changed in abundance as a function of growth factor or drug treatment including novel sites of phosphorylation on the EGFR itself. These findings demonstrate the feasibility of using phospho-proteomics to determine drug and disease mechanisms, and as a measure of drug target modulation in tissue.

Results of in vitro drug testing are correlated with clinical response to chemotherapy: Accuracy to predict clinical drug resistance was found to be as high as 90%. The benefit of using in vitro models lies in the ability to probe cellular response in a controlled closed system, where effects of drug concentrations, treatment duration, drug efflux kinetics and multidrug combinations can be assessed by a variety of cell biology techniques. Cisplatin is a widely used chemotherapy drug that targets genomic DNA of the cells, forming both interstrand and intrastrand cross-links that lead to cell death. One limitation of its clinical use is in predicting the development of resistance and severe side effects in patients. Mechanisms of resistance such as reduced drug accumulation, increased detoxification through cisplatin binding to cellular thiols, reduced DNA platination, and increased DNA repair have been reported, however (tamoxifen enhancement of cisplatin). In vitro models of different cancer types (SKOV3, HeLa, A431, MCF-7) were used to study the effects of cisplatin on cell morphology and phenotypic and functional characteristics with a large panel of metal-tagged antibodies and Imaging Mass Cytometry (IMC) at the single-cell level (1). Proteins involved in DNA damage repair (γH2AX, PP2A, pHistone H3), apoptosis (CD98, caspase-3, cleaved PARP), cell proliferation (cyclin B1, Ki-67), metastasis (vimentin, β-catenin, VEGF, CD63, CD9), substrate adhesion (CD29, CD49e, CD49b, CD51, CD54, CD47, CD61), organelle morphology (CD107a, Mito, histone H3), and signaling pathways (STAT3, pERK1/2, pS6), as well as surface receptors (EGFR, HER2, BRCA, MUC1, CD44, EpCAM, CD142, CD59, beta-catenin) and structural markers (CK5, CK8/18, β-actin, β-tubulin), were identified simultaneously in each individual cell with specific metal-conjugated antibodies. S-phase cells were visualized by detection of 127I in 5-iodo-2′-deoxyuridine (IdU) added to culture media. Presence of cisplatin in cell nuclei and cytoplasm was registered by IMC of platinum stable isotopes. Combination therapy of cisplatin and paclitaxel is a standard chemotherapeutic regimen to treat recurrent or metastatic cervical cancer. Cell lines from various tumors may develop resistance to cisplatin. Reduced cisplatin uptake has been observed in cervical cancer cells with cisplatin resistance. The cisplatin-resistant HeLa cells and A431 (A431/Pt) cells show 50% and 77% reduction in cisplatin uptake, respectively, compared with the parental cell lines. Human ovarian cancers (in vitro model SKOV3), for which cisplatin is a mainstay of treatment, develop drug resistance and pose an important clinical challenge. (1) Chang, Q et al. Nature Scientific Reports 6 (2016): 36641 Citation Format: Olga Ornatsky, Alexandre Bouzekri, Bedilu Allo, Jessica Watson. In vitro drug effects on cancer cell morphology and functional state revealed by multiparameter imaging mass cytometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2104. doi:10.1158/1538-7445.AM2017-2104

Investigation of co-distribution of 35 biomarkers simultaneously (major cell type and immune-oncology, stromal and tissue architecture markers, as well as cell proliferation and nuclear markers) in normal lymphoid sections using Imaging Mass Cytometry (Qing et al, Cytometry: Part A, 2017) is presented. Tonsil tissue revealed primary lymph follicles as dense clusters of lymphocytes expressing B-cell markers, surrounded by CD3, CD4, and CD8 T-cells. Secondary lymph follicles could be distinguished by proliferating B-cells with high Ki-67 expression. Strong expression of Bcl-6 was detected in germinal-center B-cells. Tonsillar FoxP3 CD8 T-cells exhibit a Treg phenotype with high CTLA-4 and CD45RO. CD68+ mac/mono were found in germinal centers and rarely in stroma. Squamous epithelium of crypts was beta-catenin positive and infiltrated by PD-L1+ T-cells, while PD-1+ cells were also found within the follicle centers. Images acquired on the Hyperion™ Imaging System (Fluidigm Inc.) were compared to immunofluorescence (IF) of sequential sections stained with the same antibodies (Ab) conjugated to fluorophores (FL). For direct comparison of IF and IMC, dual tagged Abs were created by attaching a metal tag first (Maxpar®, Fluidigm Inc.), then conjugating to FL using click chemistry. CD3 and CD19 were labeled with metals and FL, and tested in combination with the full panel on 8 μm frozen tonsil sections. CD3+ and CD19+ lymphs were identified by IF first, followed by IMC analysis. Results show that IMC is comparable to IF images and allows identification, characterization and localization of cell populations and tissue architecture in the absence of autofluorescence, photobleaching, with low background for acquisition of up to 50 targets.

Background —Estrogen may increase the long-term survival of women who have suffered from a myocardial infarction (MI). We examined the acute and chronic influence of estrogen on MI in the rat left coronary artery ligation model. Methods and Results —Female Sprague-Dawley rats (10 to 12 weeks, n=93), divided into 3 groups (rats with intact ovaries, ovariectomized rats administered 17β-estradiol [17β-E 2 ] replacement, and ovariectomized rats administered placebo 2 weeks before MI), were randomized to left coronary artery ligation (n=66) or sham-operated (n=27) groups. Ten to 11 weeks after MI, rats were randomly assigned to either (1) assessment of left ventricular (LV) function and morphometric analysis or (2) measurement of cardiopulmonary mRNA expression of preproendothelin-1 and endothelin A and B receptors. Acutely, estrogen was associated with a trend toward increased mortality. Infarct size was increased in the 17β-E 2 group compared with the placebo group (42±2% versus 26±3%, respectively; P =0.01). Chronically, wall tension was normalized through a reduction in LV cavity size with estrogen treatment (419±41 mm Hg/mm for 17β-E 2 versus 946±300 mm Hg/mm for placebo, P =0.039). In the LV, there was a 2.5-fold increase in endothelin B mRNA expression after MI in placebo-treated rats ( P =0.004 versus sham-operated rats) that was prevented in the 17β-E 2 group ( P =NS versus sham-operated rats). Conclusions —These results suggest that estrogen is detrimental at the time of MI or early post-MI period, resulting in an increased size of infarct or infarct expansion, but chronically, it can normalize wall tension and inhibit LV dilatation, which may in turn lead to increased long-term survival. Regulation of the endothelin system, particularly the expression of the endothelin B receptor, may contribute to these estrogenic effects.

The Fluidigm® CyTOF system is a mass cytometer that uniquely enables high-dimensional single-cell analysis of complex populations. Mass cytometry is based on inductively coupled plasma time-of-flight mass spectrometry used for multiplex proteomic analysis. In this approach, metal-conjugated affinity reagents are used to tag the components of cells. The cells are nebulized and sent to an argon plasma, ionizing the multi-atom metal tags, which are then analyzed by a time-of-flight mass spectrometer. Gene expression can be finely tuned through the synthesis of RNA and through the control of its stability and location. Misregulation of gene expression can have severe consequences, such as developmental disorders, cancer and autoimmune diseases. The ability to acquire complete spatial-temporal profiles of gene expression is therefore critical for the understanding of disease pathophysiology, medical diagnostics and drug discovery. In this presentation, we discuss the development of a multiplex method for targeted RNA detection using the Fluidigm CyTOF® and Advanced Cell Diagnostics RNAscope® platforms. This novel assay includes the hybridization of RNA-specific target probes, followed by signal amplification and ending with the binding of amplifier-specific metal-labelled probes. Presently, we are able to detect four different mRNA probes in a single-cell analysis setting. The detection of RNA is compatible with Fluidigm products such as Maxpar® antibodies. Future developments will include high-dimensional detection that enables researchers to investigate the simultaneous expression profile of RNA and protein across millions of cells.

Pathology assessment of tissue sections provides prognostic evaluation and helps select optimum treatment regimens. Digital pathology has made significant strides in the analysis of several markers. There is a growing understanding of cell heterogeneity within tumor tissue, role of microenvironment, and the impact of immune cells on cancer development. Sophisticated tools are needed to provide quantitative information for a large number of biomarkers, low-abundance small molecules and chemotherapeutic drugs, while retaining spatial resolution of cells and tissue architecture. Imaging mass cytometry (IMC) is a novel technology that can simultaneously detect and quantitatively measure more than 50 metal-containing reagents in tissue sections at 1 μm resolution. IMC combines laser ablation with the Helios CyTOF®. We will describe in detail technology, workflow, multiplexing protocols, image analysis and show representative data for human and mouse sections. We will demonstrate the use of metal-containing histological stains for tissue architecture, and endogenous element identification [iodine, platinum]. Combined detection of protein targets and transcripts within cells will be presented. Validation will be demonstrated on sequential tissue sections prepared by conventional immunohistochemistry. Precision medicine is based on access to high-density data (proteomics and genomics) which provides accurate diagnosis and information on the best therapeutic approach. IMC is a highly multiparametric, quantitative method for phenotypic, signaling pathway, and cell state protein identification together with spatial information within tissue sections.

Metal-chelating polymers (MCPs) are important reagents for multiplexed immunoassays based on mass cytometry. The role of the polymer is to carry multiple copies of individual metal isotopes, typically as lanthanide ions, and to provide a reactive functionality for convenient attachment to a monoclonal antibody (mAb). For this application, the optimum combination of chain length, backbone structure, end group, pendant groups, and synthesis strategy has yet to be determined. Here we describe the synthesis of a new type of MCP based on anionic ring-opening polymerization of an activated cyclopropane (the diallyl ester of 1,1-cyclopropane dicarboxylic acid) using a combination of 2-furanmethanethiol and a phosphazene base as the initiator. This reaction takes place with rigorous control over molecular weight, yielding a polymer with a narrow molecular weight distribution, reactive pendant groups for introducing a metal chelator, and a functional end group with orthogonal reactivity for attaching the polymer to the mAbs. Following the ring-opening polymerization, a two-step transformation introduced diethylenetriaminepentaacetic acid (DTPA) chelating groups on each pendant group. The polymers were characterized by NMR, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). The binding properties toward Gd(3+) as a prototypical lanthanide (Ln) ion were also studied by isothermal titration calorimetry (ITC). Attachment to a mAb involves a Diels-Alder reaction of the terminal furan with a bismaleimide, followed by a Michael addition of a thiol on the mAb, generated by mild reduction of a disulfide bond in the hinge region. Polymer samples with a number average degree of polymerization of 35, with a binding capacity of 49.5 ± 6 Ln(3+) ions per chain, were loaded with 10 different types of Ln ions and conjugated to 10 different mAbs. A suite of metal-tagged Abs was tested by mass cytometry in a 10-plex single cell analysis of human adult peripheral blood, allowing us to quantify the antibody binding capacity of 10 different cell surface antigens associated with specific cell types.

Lanthanide-encoded polystyrene particles synthesized by dispersion polymerization are excellent candidates for mass cytometry based immunoassays, however they have previously lacked the ability to conjugate biomolecules to the particle surface. We present here three approaches to post-functionalize these particles, enabling the covalent attachment of proteins. Our first approach used partially hydrolyzed poly(N-vinylpyrrolidone) as a dispersion polymerization stabilizer to synthesize particles with high concentration of -COOH groups on the particle surface. In an alternative strategy to provide -COOH functionality to the lanthanide-encoded particles, we employed seeded emulsion polymerization to graft poly(methacrylic acid) (PMAA) chains onto the surface of these particles. However, these two approaches gave little to no improvement in the extent of bioconjugation. In our third approach, seeded emulsion polymerization was subsequently used as a method to grow a functional polymer shell (in this case, poly(glycidyl methacrylate) (PGMA)) onto the surface of these particles, which proved highly successful. The epoxide-rich PGMA shell permitted extensive surface bioconjugation of NeutrAvidin, as probed by an Lu-labeled biotin reporter (ca. 7 × 10(5) binding events per particle with a very low amount of non-specific binding) and analyzed by mass cytometry. It was shown that coupling agents such as EDC were not needed, such was the reactivity of the particle surface. These particles were stable and the addition of a polymeric shell was shown did not affect the narrow lanthanide ion distribution within the particle interior as analyzed by mass cytometry. These particles represent the most promising candidates for the development of a highly multiplexed bioassay based on lanthanide-labeled particles to date.

Flow cytometry is an essential tool for dissecting the functional complexity of hematopoiesis. We used single-cell "mass cytometry" to examine healthy human bone marrow, measuring 34 parameters simultaneously in single cells (binding of 31 antibodies, viability, DNA content, and relative cell size). The signaling behavior of cell subsets spanning a defined hematopoietic hierarchy was monitored with 18 simultaneous markers of functional signaling states perturbed by a set of ex vivo stimuli and inhibitors. The data set allowed for an algorithmically driven assembly of related cell types defined by surface antigen expression, providing a superimposable map of cell signaling responses in combination with drug inhibition. Visualized in this manner, the analysis revealed previously unappreciated instances of both precise signaling responses that were bounded within conventionally defined cell subsets and more continuous phosphorylation responses that crossed cell population boundaries in unexpected manners yet tracked closely with cellular phenotype. Collectively, such single-cell analyses provide system-wide views of immune signaling in healthy human hematopoiesis, against which drug action and disease can be compared for mechanistic studies and pharmacologic intervention.