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In order to improve molecular response for a discontinuation attempt in chronic myeloid leukemia (CML) patients in chronic phase, who had not achieved at least a molecular response IS (MR 4.0) after at least 2 years of imatinib therapy, we prospectively evaluated whether they could attain MR 4.0 after a switch to a combination of nilotinib and 9 months of pegylated interferon-α2b (PegIFN). The primary endpoint of confirmed MR 4.0 at month 12 (a BCR-ABL1 IS level ≤ 0.01% both at 12 and 15 months) was reached by 44% (7/16 patients, 95% confidence interval (CI): 23- 67%) of patients, with 81% (13/16 patients, 95% CI: 57-93%) of patients achieving an unconfirmed MR 4.0. The scheduled combination was completed by 56% of the patients, with premature discontinuations, mainly due to mood disturbances after the introduction of PegIFN, questioning the feasibility of the combination of nilotinib and PegIFN for this patient population and treatment goal. A comprehensive clinical substudy program was implemented to characterize the impact of the treatment changes on the immunological profile. This trial was registered at www.clinicaltrials.gov as #NCT01866553.

The use of single-cell profiling of phenotypes is suggested to inform about chemoresistance and lack of treatment response in cancer. Mass cytometry by time-of-flight (CyTOF) allows high throughput multiparametric analysis at the single-cell level to perform for in-depth characterisation of heterogeneity in leukemia. However, computational identification of cell populations from CyTOF, and utilisation of single-cell data for biomarker discoveries is challenging. Here, we deployed a machine learning-based framework that enables automatic cell population annotation, and systematic exploration of interactions between signalling proteins in a CyTOF antibody panel. We applied the developed framework to analyse a cohort of 45 leukemia patients. We investigated associations between the cellular composition and clinicopathological and genetic features, and reported salient signalling interactions of Multipotent Progenitor-like leukemia cells that were sufficient to predict short-term survival at time of diagnosis. Our findings confirmed that targeting cell type-specific signalling interactions in leukemia might improve existing patient stratification methods with the potential to inform early about more precise treatment options.

High-grade serous ovarian cancer (HGSOC) has poor prognosis and new treatment modalities are needed. Immunotherapy, with checkpoint inhibitors, have demonstrated limited impact. To evaluate the suitability for immunotherapeutics, contextualized preclinical models are required to secure meaningful clinical translation. Therefore, we developed and characterized humanized patient-derived xenograft (hu PDX) murine models of HGSOC, which were established by orthotopic implantation of tumor cell suspensions and intravenous injection of CD34+ cells isolated from umbilical cord blood samples. The developing human immune system in NSG and NSGS mice was followed longitudinally by flow cytometry and characterized by mass cytometry with a panel of 34 surface markers. Molecular imaging of tumor burden, survival analysis, and characterization of tumor-infiltrating immune cells was performed to assess the treatment response to anti-PD-1 (nivolumab) monotherapy. Successful generation of hu PDX models was achieved. Mice treated with nivolumab showed a decrease in tumor burden, however no significant survival benefit was identified when compared to untreated controls. No correlation was seen between PD-L1 expression and CD8 T cell infiltration and response parameters. As the characterization showed an immune infiltration of predominantly myeloid cells, similar to what is observed in HGSOC patients, the models may have the potential to evaluate the importance of myeloid cell immunomodulation as well. publishedVersion

Background: A fundamental hallmark of cancer cells is their ability to sustain proliferative signaling and cell survival, reflected in a cellular chemotherapy response that is poorly understood. We questioned whether chemotherapy modulated phospho-signaling at 4 and 24 h in vivo could provide information about long-term survival in acute myeloid leukemia (AML), and if the signaling response to therapy was more informative than analysis at time of diagnosis. Methods: Peripheral blood was collected from 32 younger AML patients (age 16-74 years), before, 4- and 24 hours after start of induction chemotherapy. Samples were analyzed by 36-dimensional mass cytometry for assessment of alterations in immunophenotypes and intracellular signaling using unsupervised and supervised machine learning approaches. Results were validated by RNA sequencing and mass spectrometry proteomics (Super SILAC). Targeted sequencing was used to characterize patient samples for recurrent AML mutations. Drug sensitivity and resistance testing ex vivo was compared to activation of relevant signal transduction pathways and mutational profile. Findings: 5-year patient survival was accurately predicted in the leukemic cell population at 24 hours after therapy onset by phospho-proteins p-ERK1/2 (T202/Y204) and p-p38 (T180/Y182). RNA sequencing showed induction of MAPK target gene expression and the AP-1 transcription complex in patients with high p-ERK1/2. Super-SILAC proteomics confirmed an increase in the abundance of p38 prime target MAPKAPK2(MK2) 24 hours after start of induction therapy. Ex vivo drug sensitivity testing demonstrated high sensitivity to MEK inhibitors in the patient cells with high p-ERK1/2 measured at diagnosis or 24 hours after start of chemotherapy. Interpretation: Early single cell signaling response to chemotherapy provided precise prognostic information independent of stratification by genetics. We propose that early functional measurement of chemotherapy-potentiated MAPK pathway signaling could identify non-responders to intensive chemotherapy allowing precise treatment adjustment.

Aberrant pro-survival signaling is a hallmark of cancer cells, but the response to chemotherapy is poorly understood. In this study, we investigate the initial signaling response to standard induction chemotherapy in a cohort of 32 acute myeloid leukemia (AML) patients, using 36-dimensional mass cytometry. Through supervised and unsupervised machine learning approaches, we find that reduction of extracellular-signal-regulated kinase (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK) phosphorylation in the myeloid cell compartment 24 h post-chemotherapy is a significant predictor of patient 5-year overall survival in this cohort. Validation by RNA sequencing shows induction of MAPK target gene expression in patients with high phospho-ERK1/2 24 h post-chemotherapy, while proteomics confirm an increase of the p38 prime target MAPK activated protein kinase 2 (MAPKAPK2). In this study, we demonstrate that mass cytometry can be a valuable tool for early response evaluation in AML and elucidate the potential of functional signaling analyses in precision oncology diagnostics.

We describe here a simple and efficient antibody titration approach for cell‐surface markers and intracellular cell signaling targets for mass cytometry. The iterative approach builds upon a well‐characterized backbone panel of antibodies and analysis using bioinformatic tools such as SPADE. Healthy peripheral blood and bone marrow cells are stained with a pre‐optimized “backbone” antibody panel in addition to the progressively diluted (titrated) antibodies. Clustering based on the backbone panel enables the titration of each antibody against a rich hematopoietic background and assures that nonspecific binding and signal spillover can be quantified accurately. Using a slightly expanded backbone panel, antibodies quantifying changes in transcription factors and phosphorylated antigens are titrated on ex vivo stimulated cells to optimize sensitivity and evaluate baseline expression. Based on this information, complex panels of antibodies can be thoroughly optimized for use on healthy whole blood and bone marrow and are easily adaptable to the investigation of samples from for example clinical studies. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

SUMMARYAcute myeloid leukaemia (AML) is a highly heterogeneous disease. Here, we decipher the disease composition of a single AML patient through longitudinal sampling scrutinized by high-resolution genetic and phenotypic approaches, including sequencing, immunophenotyping, ex vivo drug sensitivity testing and establishment of patient-derived xenograft models. Throughout the disease course we identified patterns of both divergent and convergent molecular evolution within the leukemic compartment. We identified at least six discrete leukaemia initiating cell populations, of which five were characterised by known recurrent mutations in AML. These populations partly correlated with immunophenotypically defined cell subsets, drug sensitivity profiles and population-specific potential for engraftment in immunodeficient mice. Our results indicate that the genetic and phenotypic development are closely intertwined, and that diversity in the leukaemic gene-environment likely influences disease trajectories.SIGNIFICANCENovel therapeutic approaches in AML are characterised by targeting molecular mechanisms thought to drive leukemogenesis, but emergent evidence suggests that intra-leukemic composition may be more diverse than previously appreciated. Through in-depth genetic and phenotypic characterization of the disease course of a single AML patient, we demonstrate a high degree of inter-individual complexity that exceeds the prevailing disease conception. The temporal molecular landscape of this patient suggests that leukemogenic transitions may not be categorically monoclonal. Patterns of converging molecular evolution further imply that higher levels of biological organisation than the molecular machinery of single cells may influence leukemogenic trajectories. Disease dynamics, relational properties and causal contribution from several levels of biological organization comes into conflict with the linear monocausal explanatory model on which precision oncology is largely built. This may have implications for current precision oncology oriented prectices, including molecular categorization, molecular therapeutic targeting and predictive models.

Chronic myeloid leukemia (CML) is a stem cell disease of the bone marrow where mechanisms of inter‐leukemic communication and cell‐to‐cell interactions are proposed to be important for optimal therapy response. Tunneling nanotubes (TNTs) are novel intercellular communication structures transporting different cargos with potential implications in therapy resistance. Here, we have investigated TNTs in CML cells and following treatment with the highly effective CML therapeutics tyrosine kinase inhibitors (TKIs) and interferon‐α (IFNα). CML cells from chronic phase CML patients as well as the blast crisis phase cell lines, Kcl‐22 and K562, formed few or no TNTs. Treatment with imatinib increased TNT formation in both Kcl‐22 and K562 cells, while nilotinib or IFNα increased TNTs in Kcl‐22 cells only where the TNT increase was associated with adherence to fibronectin‐coated surfaces, altered morphology, and reduced movement involving β1integrin. Ex vivo treated cells from chronic phase CML patients showed limited changes in TNT formation similarly to bone marrow cells from healthy individuals. Interestingly, in vivo nilotinib treatment in a Kcl‐22 subcutaneous mouse model resulted in morphological changes and TNT‐like structures in the tumor‐derived Kcl‐22 cells. Our results demonstrate that CML cells express low levels of TNTs, but CML therapeutics increase TNT formation in designated cell models indicating TNT functionality in bone marrow derived malignancies and their microenvironment. publishedVersion

Simple Summary High-grade serous ovarian cancer (HGSOC) is the deadliest gynecological malignancy. Despite increasing research on HGSOC, biomarkers for individualized selection of therapy are scarce. In this study, we develop a multiparametric mass cytometry antibody panel to identify differences in the cellular composition of the microenvironment of tumor tissues dissociated to single-cell suspensions. We also investigate how dissociation methods impact results. Application of our antibody panel to HGSOC tissues showed its ability to identify established main cell subsets and subpopulations of these cells. Comparisons between dissociation methods revealed differences in cell fractions for one immune, two stromal, and three tumor cell subpopulations, while functional marker expression was not affected by the dissociation method. The interpatient disparities identified in the tumor microenvironment were more significant than those identified between differently dissociated tissues from one patient, indicating that the panel facilitates the mapping of individual tumor microenvironments in HGSOC patients. Abstract Improved molecular dissection of the tumor microenvironment (TME) holds promise for treating high-grade serous ovarian cancer (HGSOC), a gynecological malignancy with high mortality. Reliable disease-related biomarkers are scarce, but single-cell mapping of the TME could identify patient-specific prognostic differences. To avoid technical variation effects, however, tissue dissociation effects on single cells must be considered. We present a novel Cytometry by Time-of-Flight antibody panel for single-cell suspensions to identify individual TME profiles of HGSOC patients and evaluate the effects of dissociation methods on results. The panel was developed utilizing cell lines, healthy donor blood, and stem cells and was applied to HGSOC tissues dissociated by six methods. Data were analyzed using Cytobank and X-shift and illustrated by t-distributed stochastic neighbor embedding plots, heatmaps, and stacked bar and error plots. The panel distinguishes the main cellular subsets and subpopulations, enabling characterization of individual TME profiles. The dissociation method affected some immune (n = 1), stromal (n = 2), and tumor (n = 3) subsets, while functional marker expressions remained comparable. In conclusion, the panel can identify subsets of the HGSOC TME and can be used for in-depth profiling. This panel represents a promising profiling tool for HGSOC when tissue handling is considered.

Hydrogen sulfide (H2S) is an endogenous gasotransmitter in human physiology and inflammatory disease, however, with limited knowledge of how signal transduction pathways are involved in immune cells. To examine the effects of sulfide on relevant intracellular signaling in human peripheral blood mononuclear cells (PBMCs), we stimulated healthy donor PBMCs with sodium hydrosulfide (NaHS, 1–1000 μM) to mimic H2S stimulation, and analyzed phosphorylation of p38 mitogen activated protein kinase (MAPK) (pT180/pY182), NF-κB p65 (pS529), Akt (pS473) and CREB/ATF1 (pS133/pS63) with flow and mass cytometry. In contrast to transient effects in subsets of lymphocytes, classical monocytes demonstrated sustained phosphorylation of p38, Akt and CREB/ATF1. NaHS induced calcium dependent phosphorylation of p38, Akt and CREB, but not NF-κB, and the phosphorylation of Akt was partly dependent on p38, indicative of p38-Akt crosstalk. Attenuation of these effects by molecules targeting p38 and Hsp90 indicated Hsp90 as a possible target for H2S-induced activation of p38. These results provide a description of a NaHS-induced signal transduction pathway in human primary immune cells that may have relevance for the role of sulfides in inflammation. publishedVersion

Single-cell proteomics in cancer is evolving and promises to provide more accurate diagnoses based on detailed molecular features of cells within tumors. This review focuses on technologies that allow for collection of complex data from single cells, but also highlights methods that are adaptable to routine cancer diagnostics. Current diagnostics rely on histopathological analysis, complemented by mutational detection and clinical imaging. Though crucial, the information gained is often not directly transferable to defined therapeutic strategies, and predicting therapy response in a patient is difficult. In cancer, cellular states revealed through perturbed intracellular signaling pathways can identify functional mutations recurrent in cancer subsets. Single-cell proteomics remains to be validated in clinical trials where serial samples before and during treatment can reveal excessive clonal evolution and therapy failure; its use in clinical trials is anticipated to ignite a diagnostic revolution that will better align diagnostics with the current biological understanding of cancer.

Simple Summary Investigation of protein expression in cancer cells is an important part of the diagnostic process. Increasing knowledge about expression of different proteins has been exploited for prognostic assessments and in some cases also for selection of treatment. The p53 protein has proven important in development of various cancers, and the expression of this protein and its signaling pathway is therefore of interest when examining cancer patient samples. Here, we present mass cytometry as a tool for detection of p53 expression. Mass cytometry allows for measurement of up to 50 parameters per sample with single cell resolution, and we aim to demonstrate its potential for p53-focused research. Abstract Purpose: The p53 protein and its post-translational modifications are distinctly expressed in various normal cell types and malignant cells and are usually detected by immunohistochemistry and flow cytometry in contemporary diagnostics. Here, we describe an approach for simultaneous multiparameter detection of p53, its post-translational modifications and p53 pathway-related signaling proteins in single cells using mass cytometry. Method: We conjugated p53-specific antibodies to metal tags for detection by mass cytometry, allowing the detection of proteins and their post-translational modifications in single cells. We provide an overview of the antibody validation process using relevant biological controls, including cell lines treated in vitro with a stimulus (irradiation) known to induce changes in the expression level of p53. Finally, we present the potential of the method through investigation of primary samples from leukemia patients with distinct TP53 mutational status. Results: The p53 protein can be detected in cell lines and in primary samples by mass cytometry. By combining antibodies for p53-related signaling proteins with a surface marker panel, we show that mass cytometry can be used to decipher the single cell p53 signaling pathway in heterogeneous patient samples. Conclusion: Single cell profiling by mass cytometry allows the investigation of the p53 functionality through examination of relevant downstream signaling proteins in normal and malignant cells. Our work illustrates a novel approach for single cell profiling of p53.

Acute myeloid leukaemia is a disease of the haematopoietic stem and progenitor cells distinguished by an impairment of proliferation, propagation and differentiation of the haematopoietic lineage[1]. AML is a heterogenous disease, where patient stratification and personalised therapeutic strategies are of importance[2]. The transmembrane protein CD37 has been associated with regulation of cell to cell interaction and proliferation in both B and T cells. Mice knockout studies have suggested that CD37 is not crucial for B cell development, however, it is highly expressed in malignant and suboptimal conditions and thus represent a good target for B-cell malignancies[3]. Pereira et al. reported that their anti-CD37 antibody-drug conjugate was a potential therapeutic in AML[4]. Their study revealed anti-leukemic effect in primary AML material and cell lines bothin vivoandin vitro. An investigation of CD37 expression in AML patients is needed to understand the relevance of CD37 immunotherapy. To investigate the relevance of targeted therapy of CD37 the chimeric mAb NNV003 anti-CD37 antibody was evaluated in AML samples. Single-cell time-of-flight mass cytometry (CyTOF), an established tool to analyse the immune signalling in bone marrow and peripheral blood, was used to investigate CD37 expression in 59 AML patient samples. A panel was designed to categorise hierarchical landscape of AML and the leukemic stem cell population (LSCs). CyTOF identified CD37 expression exclusively in the B-cell population of our 59 patients, whereas the AML blast population was negative for CD37 expression. Flow cytometry, however; identified 5/59 patients with CD37 expression in the leukemic blast population. Although previous studies show that an anti-CD37 drug conjugate showed anti-leukemic effectin vivoandin vitro, our results do not support that it is a promising therapeutic biomarker. We have uncovered that malignant expression of CD37 is not a feature of the AML patients investigated. We do not consider CD37 to be a promising and good target for precision therapy of AML. Kayser, S. and M.J. Levis, Advances in targeted therapy for acute myeloid leukaemia. Br J Haematol, 2018. 180(4): p. 484-500.Patel, J.P., et al., Prognostic relevance of integrated genetic profiling in acute myeloid leukemia. N Engl J Med, 2012. 366(12): p. 1079-89.Payandeh, Z., et al., Anti-CD37 targeted immunotherapy of B-Cell malignancies. Biotechnol Lett, 2018. 40(11-12): p. 1459-1466.Pereira, D.S., et al., AGS67E, an Anti-CD37 Monomethyl Auristatin E Antibody-Drug Conjugate as a Potential Therapeutic for B/T-Cell Malignancies and AML: A New Role for CD37 in AML. Mol Cancer Ther, 2015. 14(7): p. 1650-60. Disclosures Heyerdahl: Nordic Nanovector ASA:Current Employment, Current equity holder in publicly-traded company.Dahle:Nordic Nanovector ASA:Current Employment, Current equity holder in publicly-traded company.Gjertsen:Novartis:Consultancy;KinN Therapeutics AS:Current equity holder in private company;Pfizer Inc:Consultancy;BerGenBio AS:Consultancy, Research Funding;Alden Cancer Therapy AS:Current equity holder in private company.Mccormack:KinN Therapeutics AS:Current equity holder in private company.

Summary statementThis study describes the effects of tyrosine kinase inhibitors on tunneling nanotube formation via increased adhesion through β-integrin in chronic myeloid leukemia cells.AbstractThe actin-containing cell-to-cell communicator tunneling nanotube (TNT) is involved in regulation of cell death threshold of leukemic cells, while the mechanism of TNT regulation is mostly unknown. We have investigated TNT formation and its response to treatment in chronic myeloid leukemia (CML) cells with the pathognomonic chimeric fusion kinase BCR-ABL1 after treatment with the tyrosine kinase inhibitor nilotinib and interferon-α. Bone marrow cells of chronic phase CML patients and the CML cell line Kcl-22 formed few or no TNTs. Nilotinib and interferon-α treatment induced TNT formation in Kcl-22 cells and were found to be linked to increased adherence to fibronectin coated surfaces by restoration of β1-integrin function. This suggests modulation of TNT cell-cell communication in CML as a novel mechanism in kinase inhibitor therapy of CML.

Monitoring of single cell signal transduction in leukemic cellular subsets has been proposed to provide deeper understanding of disease biology and prognosis, but has so far not been tested in a clinical trial of targeted therapy. We developed a complete mass cytometry analysis pipeline for characterization of intracellular signal transduction patterns in the major leukocyte subsets of chronic phase chronic myeloid leukemia. Changes in phosphorylated Bcr-Abl1 and the signaling pathways involved were readily identifiable in peripheral blood single cells already within three hours of the patient receiving oral nilotinib. The signal transduction profiles of healthy donors were clearly distinct from those of the patients at diagnosis. Furthermore, using principal component analysis, we could show that phosphorylated transcription factors STAT3 (Y705) and CREB (S133) within seven days reflected BCR-ABL1IS at three and six months. Analyses of peripheral blood cells longitudinally collected from patients in the ENEST1st clinical trial showed that single cell mass cytometry appears to be highly suitable for future investigations addressing tyrosine kinase inhibitor dosing and effect. ©2017 Ferrata Storti Foundation Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or internal use. Sharing published material for non-commercial purposes is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for commercial purposes is not allowed without permission in writing from the publisher.

Treatment with ultrasound and microbubbles (sonoporation) to enhance therapeutic efficacy in cancer therapy is rapidly expanding, but there is still very little consensus as to why it works. Despite the original assumption that pore formation in the cell membrane is responsible for increased uptake of drugs, the molecular mechanisms behind this phenomenon are largely unknown. We treated cancer cells (MOLM-13) and healthy peripheral blood mononuclear cells (PBMCs) with ultrasound at three acoustic intensities (74, 501, 2079 mW/cm2) &plusmn, microbubbles. We subsequently monitored the intracellular response of a number of key signaling pathways using flow cytometry or western blotting 5 min, 30 min and 2 h post-treatment. This was complemented by studies on uptake of a cell impermeable dye (calcein) and investigations of cell viability (cell count, Hoechst staining and colony forming assay). Ultrasound + microbubbles resulted in both early changes (p38 (Arcsinh ratio at high ultrasound + microbubbles: +0.5), ERK1/2 (+0.7), CREB (+1.3), STAT3 (+0.7) and AKT (+0.5)) and late changes (ribosomal protein S6 (Arcsinh ratio at low ultrasound: +0.6) and eIF2&alpha, in protein phosphorylation). Observed changes in protein phosphorylation corresponded to changes in sonoporation efficiency and in viability, predominantly in cancer cells. Sonoporation induced protein phosphorylation in healthy cells was pronounced (p38 (+0.03), ERK1/2 (&minus, 0.03), CREB (+0.0), STAT3 (&minus, 0.1) and AKT (+0.04) and S6 (+0.2)). This supports the hypothesis that sonoporation may enhance therapeutic efficacy of cancer treatment, without causing damage to healthy cells.

Introduction Chemotherapy induced clonal selection and development are major contributors to disease relapse and resistance to therapy in AML. An immediate response to chemotherapy in intracellular signalling networks can be detected within minutes in vivo. (Irish J. et al 2004) We hypothesize that by analyzing the immediate intracellular chemotherapy response we might reveal which cancer clones are resistant to therapy and how they might be targeted. (Anensen N. et al Clin Cancer Res 2006), (Øyan M. et al BMC Cancer 2009) CyTOF combines the principles of conventional flow cytometry with time-of-flight mass spectrometry to allow analyses of multiple parameters simultaneously in single cells. This dramatically increases the numbers of antibodies that can be applied and permits a simultaneous analysis of both intracellular signaling networks and phenotypic characterization of cells. Material and methods We have performed a 36- dimensional mass cytometry analysis (CyTOF), containing 21 surface markers (CD66b, CD16, CD45, CD11b, CD25, CD3, CD4, CD8, CD56, CD20, CD38, CD34, CD117, CD33, CD64, CD14, HLA-DR, Axl-1H12, CD90, CD7, CD123) and 15 intracellular markers (cCaspase-3, p-4EB-P1, p-Stat 5, p-Stat 3, p-Stat 1, p-p38, p- ERK ½, p-Akt, p-NFkB, p-CREB, p-S6, p-Axl, p-Rb, Cyclin B1, p-Histone H3) of over 40 de novo AML patients eligible for intensive chemotherapy. Peripheral blood was sampled at 4 hours and at 18- 24 hours after start of standard "3+7" induction therapy (Lowenberg B. et al Blood 2017). Bone marrow and peripheral blood from healthy donors were also included in the analysis. Results Well-characterized surface markers were used to perform an unsupervised clustering of the high dimensional single cell data from each AML patient before start of induction therapy (Figure 1A). This clustering resulted in 15 unique cell clusters throughout the patient cohort, illustrated by viSNE in Figure 2A. The heatmap in Figure 1A show the expression of surface markers in each cluster. Healthy cells in AML patients clustered together and were recognized by their characteristic phenotype, for example granulocytes in cluster 13 (CD66b+ and CD11b+), CD8 T-cells in cluster 1 (CD3+, CD7+ and CD8+) and monocytes in cluster 11 (CD45+, CD64+, CD38+ and HLA-DR+). Cluster 3 and 4 had high expression of the immature marker CD34 and thereby likely to represent blast populations. Intracellular signaling at time of diagnosis was then compared to 24 hours after start of induction therapy in the same populations. A lasso regression analysis identified intracellular markers that significantly correlated to patient survival, based on their change in expression between pre-treatment and at 24 hours. Figure 1C show a Kaplan-Meier curve of patient survival (24 months) between patients that had high or low expression ratio of an intracellular phosphor-specific antibody in cluster 3 and 15. Both clusters have expression of CD34 and CD117 that are frequently expressed on leukemic cells. The expression ratio of this intracellular marker was significantly correlated to survival (p Conclusions By applying unsupervised clustering analysis of over 40 de novo AML patients we identified leukemic cell subpopulations that had unique patterns of intracellular phospho-specific antibodies during start of induction therapy. Changes in intracellular markers during the first 24 hours of induction therapy could significantly be related to patient survival. By analyzing molecular alterations short time after chemotherapy, we aim to reveal the sub-clonal diversity and the heterogeneous responses to treatment. Identification of cancer cell subsets that are resistant to conventional chemotherapy may in the future be used to guide therapy in AML. Disclosures Gjertsen: Alden Cancer Therapy 2: Patents & Royalties: Alden Cancer Therapy II patent application in relation to CryoIT trial.; BerGenBio: Consultancy; Novartis: Consultancy; Alden Cancer Therapy 2: Membership on an entity's Board of Directors or advisory committees; Alden Cancer Therapy 2: Equity Ownership; Kinn Therapeutics: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Kinn Therapeutics: Equity Ownership; Boehringer Ingelheim: Research Funding.

Clinical diagnostic ultrasound has been known as one of the safest imaging modalities available, yet very little is known about the cellular response to such acoustic conditions. With the increased interest in therapeutic ultrasound it is becoming ever more important to understand the effects of ultrasound on cells.

Axl is a receptor tyrosine kinase that has been shown to have a strong oncogenic potential in many cancer types. Overexpression and activation of Axl is found in many cancers, and is linked to increased proliferation, migration/invasion and resistance to apoptosis. Axl overexpression has been shown to be a poor prognostic marker, and recently overexpression of Axl has also been linked to the acquired resistance to chemotherapy and other anticancer therapies in many malignancies, including AML. BGB324 (BerGenBio AS) is a first-in-class highly specific small molecule inhibitor of Axl. BGB324 has been shown to be safe and well tolerated in a clinical safety trial in healthy volunteers at doses up to 1500 mg/day with a predictable PK profile and long plasma half-life, and is currently in a phase 1b clinical trial in patients with refractory/relapsed AML and MDS (BGBC003, ClinicalTrials.gov Identifier:NCT02488408; Loges S et al. J Clin Oncol 34, 2016 suppl; abstr 2561). 20 AML and 4 MDS patients have been treated at the following dose levels (loading dose/continuation dose): 400/100mg, 600/200mg and 900/300mg. Objective responses were observed in 2/4 MDS patients and 2/20 AML patients including one CR (AML). Enrollment continues to define MTD. The effect of BGB324 on intracellular signaling and the immune profile of leukemic blasts in patients treated in the clinical study was investigated using phospho-flow cytometry. Blasts were identified using surface markers (CD45low, CD66b-, CD38-, and CD117+ and/or CD34+), and the following direct and indirect downstream targets of Axl were explored: phosphorylated (p)-Akt(S473 and T308), pErk(T202/Y204), pp38(T180/Y182), pPLCγ1(Y783), pNFκB(S529), pCREB(S113) and pSTAT1(Y701), 3(Y705), 5(Y694)and 6(Y641). Preliminary analyses of blood samples from six patients show very rapid responses in signaling pathways downstream of Axl (including Akt, Erk, NFκB and PLCγ1) within hours or days of ingestion of the first dose, although the response patterns varies from patient to patient (Figure 1A). Two distinct blast populations were identified: one CD117+/CD34- and one CD117+/CD34+. In most patients the CD117+/CD34- population displayed the most extensive signaling changes during treatment, and this population also decreased during treatment with BGB324. In contrast, the CD117+/CD34+ population expanded during the course of the treatment (Figure 1B). White cell differential counts of peripheral blood from two patients treated with BGB324 for a prolonged period of time (15 weeks or more) showed a decrease in peripheral blast count, and a corresponding increase in granulocyte and monocyte counts, suggesting that Axl inhibition may push the blasts towards differentiation. The clinical trial is ongoing, and the signaling profile of leukemic blasts in blood and bone marrow of treated patients will be further examined by conventional phosphoflow cytometry and mass cytometry searching for signaling profiles with prognostic information. In conclusion, BGB324 has unique pharmacodynamic properties and molecular responses to exposure can be observed in peripheral blood leukemic blasts by phospho-flow cytometry within hours of ingestion of the first treatment dose. Further studies may establish whether single cell signal profiling can discriminate responders from non-responders and provide information about dose-response in a clinically meaningful way. Disclosures Cortes: Astellas: Research Funding; Arog: Research Funding; Teva: Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Ambit: Research Funding. Heuser:Novartis: Consultancy, Research Funding; Tetralogic: Research Funding; BerGenBio: Research Funding; Karyopharm Therapeutics Inc: Research Funding; Bayer Pharma AG: Research Funding; Celgene: Honoraria; Pfizer: Research Funding. Lorens:BerGenBio AS: Employment, Equity Ownership, Research Funding. Gausdal:BerGenBio AS: Employment. Micklem:BerGenBio AS: Employment, Equity Ownership. Gjertsen:BerGenBio AS: Consultancy, Research Funding.

Earlier evaluation of therapy effect in patients with CML would assist in optimal use of available tyrosine kinase inhibitors (TKI). Single cell analysis by mass cytometry has enabled the quantification of up to 46 antibody epitopes, making it ideally suited for exhaustive immunophenotyping of the haematological hierarchy, and evaluation of associated dynamic signal transduction events, in a clinical setting. By integrating time resolved single cell signalling data with clinical parameters, we searched for prognostic and efficacy-response mass cytometry biomarkers within a month of TKI therapy. We report data from experiments used to validate the custom panels of antibodies, highlighting the power of mass cytometry in the analysis of primary patient material obtained on clinical studies. Peripheral Blood (PB) samples were collected before, 3 hours, 7 days and 28 days, after start of nilotinib (300 mg BID) treatment in a subset of patients (n=55) enrolled in the ENEST1st trial. PB cells were stained with two panels of antibodies, allowing a comprehensive immunophenotyping of numerous cellular subsets, and also the evaluation of intracellular phosphorylation status of several epitopes. Moreover, using a straightforward barcoding scheme, the time-resolved samples from each individual patient were pooled after barcoding and stained with the antibody panels to minimize sample variation. In a pilot study, 7 and 10 cell subsets were identified in PB samples from 4 untreated healthy donors and 2 complete sets of 4 patients enrolled in this sub study, respectively. Furthermore, a robust signal was measured for pCrkL, pStat5, pStat3, pCreb, pAbl Y412 and pAbl Y245. The two sets of samples from study patients showed substantial changes in activation status over the course of therapy. Some changes, such as pStat3 alterations are only detectable in neutrophils and monocytes, while the activity of others i.e. pCreb was found to be ubiquitous. CD34+ cells indicated decreased phosphorylation of CrkL, Stat5, and Abl Y412/245. To increase the immunophenotyping resolution of the myeloid lineage, 3 additional cell surface markers were incorporated into the cell surface panel. In 1 healthy donor, and in diagnostic samples from three patients enrolled in this sub study, this allowed the identification of 13 cell subsets: CD3+, CD4+, and CD8+ T cells, regulatory T cells (Tregs), monocytes, dendritic cells (DCs), plasmacytoid dendritic cells (pDC's), neutrophils, basophils, B cells, hematopoietic stem cells (Lin- CD34+ CD38-) and progenitor cells (Lin- CD34+ CD38-) (Figure 1 A,B). With respect to the relative number of cells identified for each cell type, the three diagnosis samples differed from the single healthy control. In the patients, we observed an expansion of the granulocytic compartment, as well as the emergence of CD34+ progenitor and stem cells in the peripheral blood. In conclusion, the here presented developed assay is able to resolve most of the cell subpopulations found in the hematopoietic tree, and also robustly measure the activity of central signalling substrates known to be involved in CML pathogenesis. With the addition of new phospho-specific antibodies, the methodology may facilitate the detailed characterization of CML in an immunological context, and may shed new light on both the disease and therapeutic mechanism. Analysis of variation in signal responses and immune profile are now in progress in the subset of patients (n=55) in the ENEST1st trial. Figure 1. Manually annotated SPADE tree from healthy donor and patient (3581_0002). With the incorporation of additional cell surface markers, the protocol was able to identify 13 cellular subsets in healthy donors (A) and a typical CML patient (B): CD3+, CD4+, and CD8+ T cells, regulatory T cells (Tregs), monocytes, dendritic cells (DCs), plasmacytoid dendritic cells (pDC's), neutrophils, basophils, B cells, hematopoietic stem cells (Lin- CD34+ CD38-) and progenitor cells (Lin- CD34+ CD38-). Figure 1. Manually annotated SPADE tree from healthy donor and patient (3581_0002). With the incorporation of additional cell surface markers, the protocol was able to identify 13 cellular subsets in healthy donors (A) and a typical CML patient (B): CD3+, CD4+, and CD8+ T cells, regulatory T cells (Tregs), monocytes, dendritic cells (DCs), plasmacytoid dendritic cells (pDC's), neutrophils, basophils, B cells, hematopoietic stem cells (Lin- CD34+ CD38-) and progenitor cells (Lin- CD34+ CD38-). Disclosures Thaler: AOP Orphan: Research Funding. Lang:Celgene: Consultancy. Hjorth-Hansen:Bristol-Myers Squibb: Research Funding; Ariad: Honoraria; Novartis: Honoraria; Pfizer: Honoraria, Research Funding. Hellmann:Novartis: Consultancy, Other: funding of travel, accomodations or expenses, Research Funding, Speakers Bureau; BMS: Consultancy, Other: funding of travel, accomodations or expenses, Speakers Bureau. Giles:Novartis: Consultancy, Honoraria, Research Funding. Hochhaus:Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding. Janssen:ARIAD: Consultancy; Bristol Myers Squibb: Consultancy; Pfizer: Consultancy; Novartis: Research Funding. Porkka:Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Ossenkoppele:Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding. Mustjoki:Signe and Ane Gyllenberg Foundation: Research Funding; Finnish Cancer Institute: Research Funding; Sigrid Juselius Foundation: Research Funding; Pfizer: Honoraria, Research Funding; the Finnish Cancer Societies: Research Funding; Academy of Finland: Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Gjertsen:Bergen University Hospital: Research Funding.

Introduction Tyrosine kinase inhibitor (TKI) induced neutropenia and thrombocytopenia may be relieved with G-CSF and trombopoietin analogs. To characterize the signaling response in a CML patient treated with hematopoietic growth factors and TKI, we employed single cell analysis of phosphoproteins in serial samples. Methods We characterized the single cell phosphoprotein responses to treatment with dasatinib, eltrombopag, and pegfilgrastim in CML-like cell lines K562 and KCL-22, normal peripheral blood leukocytes and leukocytes from a patient starting on nilotinib. These data formed a basis for comparison with serial samples (Figure 1) from a CML patients after extensive wash-out before restarted on third-choice TKI, combined with eltrombopag and pegfilgrastim. For characterization of in vivo transformational potential CML patient bone marrow cells were engrafted in duplicate in NOG mice by femoral injection. Basal phosphorylation was determined using 17 phosphorylation specific antibodies: All staining panels contain the same 4 surface antibodies and a live-dead discriminator; CD33(P67.6) PerCP-Cy5.5, CD38(HB7) PE-Cy7, CD34(581) PE, CD45(MEM-28) PE-Dynamics590 and phospho c-PARP(Asp214) AlexaFlour-700. Two phosphospecific antibodies were added to each panel with the respective direct conjugated dye Alexa Flour 488 and Alexa Flour 647. The lowest median signal for each phosphoprotein in CML cells and lymphocytes, respectively, were used as reference value for calculation of basal phosphorylation. Results A 56 y old male was diagnosed with CML (Sokal RR 0.75, Hasford RR 929, karyotype 46,XY,t(9;22)(q34;q11)[20], FISH 9q34 ABL/22q11.2 BCR dual fusion 62% of cells, PCR positive BCR-ABL e13e2/e14a2), developed prolonged thrombocytopenia and neutropenia on various dose levels of imatinib and nilotinib (neutrophile The CML bone marrow engrafted without symptomatic disease in NOG mice over 6 months monitoring, in contrast to engraftment with disseminated disease in an accelerated phase CML patient sample and the KCL-22 cell line. Phosphorylation of patient myeloid cells indicated STAT3(pY705) and STAT5(pY694) phosphorylation 2 and 3 hours after intake of eltrombopag. Dasatinib modestly inhibited SRC(pY418) and STAT3(pY705), but only transiently blunted the effect of eltrombopag. Pegfilgrastim strongly induced STAT3(pY705), STAT3(pS727), and SRC(pY418). Further analyses of cellular subsets and phospho-Abl will be presented. Conclusion Eltrombopag kept stable levels of platelets on dasatinib treatment, and cell phosphorylation reflected persisting signaling induced by eltrombopag after seven days on combination therapy. Pegfilgrastim induced strong phosphorylation of STAT3(pY705) during dasatinib co-therapy. Phosphoprotein signal analysis of patient leukemic cells reflected the hematological response of dasatinib, eltrombopag, and pegfilgrastim and may be used to monitor therapy responses of and growth factors and targeted therapy. Phosphoprotein modulated early after start of treatment. (A) Each day 1-23 is analysed separately with its pretreatment sample as control and signal baseline. (B) Various treatment days are compared, using pretreatment control at day 1 used as baseline. (A) and (B) were analysed by flow cytometry at the same day, using bar code labelling, sample processing and analysis as previously described (Skavland et al. Blood Cancer J 2012). On day 16 dasatinib and eltrombopag is administrated concomitantly. Signalling responses in lymphocytes were distinct different from myeloid cells. Further determination of cellular subsets and their signalling responses will be presented. Disclosures: Popa: KinN Therapeutics AS: Employment.