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Objectives: Multiplex immunohistochemistry and immunofluorescence (mIHC/IF) are emerging technologies that can be used to help define complex immunophenotypes in tissue, quantify immune cell subsets, and assess the spatial arrangement of marker expression. mIHC/IF assays require concerted efforts to optimize and validate the multiplex staining protocols prior to their application on slides. The best practice guidelines for staining and validation of mIHC/IF assays across platforms were previously published by this task force. The current effort represents a complementary manuscript for mIHC/IF analysis focused on the associated image analysis and data management., Methods: The Society for Immunotherapy of Cancer convened a task force of pathologists and laboratory leaders from academic centers as well as experts from pharmaceutical and diagnostic companies to develop best practice guidelines for the quantitative image analysis of mIHC/IF output and data management considerations., Results: Best-practice approaches for image acquisition, color deconvolution and spectral unmixing, tissue and cell segmentation, phenotyping, and algorithm verification are reviewed. Additional quality control (QC) measures such as batch-to-batch correction and QC for assembled images are also discussed. Recommendations for sharing raw outputs, processed results, key analysis programs and source code, and representative photomicrographs from mIHC/IF assays are included. Lastly, multi-institutional harmonization efforts are described., Conclusions: mIHC/IF technologies are maturing and are routinely included in research studies and moving towards clinical use. Guidelines for how to perform and standardize image analysis on mIHC/IF-stained slides will likely contribute to more comparable results across laboratories and pave the way for clinical implementation. A checklist encompassing these two-part guidelines for the generation of robust data from quantitative mIHC/IF assays will be provided in a third publication from this task force. While the current effort is mainly focused on best practices for characterizing the tumor microenvironment, these principles are broadly applicable to any mIHC/IF assay and associated image analysis., Competing Interests: Competing interests: JT—Contracted research: Bristol Myers Squibb, Akoya Biosciences; Consulting fees: Bristol Myers Squibb, Roche/Genentech, Merck, AstraZeneca, Regeneron, Lunaphore, Akoya Biosciences, Compugen; Stock holdings: Akoya Biosciences; JCS—Contracted research: Palleon Pharmaceuticals; MA—Consulting fees: Ionpath; Royalties: Ionpath; GA—Salary and employment: Merck; LLE—Royalties: Akoya Biosciences; CSF—Salary and employment: Roche; Stock ownership: Roche; BG—Consulting fees: Rome Therapeutics, PMV Pharma, Merck; Contracted research: Bristol Myers Squibb; IP rights: Rome Therapeutics; SGn—Contracted research: Regeneron, Boehringer Ingelheim, Janssen R&D, Genentech, Takeda, Bristol Myers Squibb, Celgene; Patents: Named coinventor on an issued patent for multiplex immunohistochemistry to characterize tumors and treatment responses, filed through Icahn School of Medicine at Mount Sinai (ISMMS) and currently unlicensed; CVH—Consulting fees: PathAI; TJH—Salary and employment (current): Bristol Myers Squibb; KK—Salary and employment: F. Hoffman-La Roche AG; AL—Salary and employment: Bristol Myers Squibb; Stock holdings; Bristol Myers Squibb; ERP—Consulting fees: Nucleai, iTeos Belgium SA; MCR—Salary and employment: AstraZeneca; DLR—Consulting fees: AstraZeneca, Cell Signaling Technology, Cepheid, Danaher, Daiichi Sankyo, NextCure, Paige.AI, Regeneron, Sanofi; Royalties: RareCyte; SJR—Consulting fees: Immunitas Therapeutics; Contracted research: Bristol Myers Squibb, Kite/Gilead; JR-C—Salary and employment: Daiichi Sankyo; KAS—Consulting fees: Shattuck Labs, EMD Serono, Clinica Alemana de Santiago, Genmab, Takeda, Merck Sharp & Dohme, Bristol Myers Squibb, AstraZeneca, Agenus, Repertoire; Fees for non-CE services: Bristol Myers Squibb, Fluidigm Corporation, Genmab, Merck, Takeda; Contracted research: Navigate BioPharma, Tesaro/GSK, Moderna, Pierre Fabre, Takeda, Surface Oncology, Merck Sharp & Dohme, Bristol Myers Squibb, AstraZeneca, Ribon Therapeutics, Akoya Biosciences, Boehringer Ingelheim, Eli Lilly; ES—Salary and employment: AstraZeneca; KES—Salary, employment, and ownership: SR Pathology LLC; MJS—Salary and employment: AstraZeneca; Stock holdings: AstraZeneca; IIW—Consulting fees: Genentech/Roche, Bayer, Bristol Myers Squibb, AstraZeneca, Pfizer, Merck, Guardant Health, Flame, Novartis, Sanofi, Daiichi Sankyo, Amgen, Jansen, Merus, AbbVie, Catalyst Therapeutics, Regeneron, Oncocyte; Contracted research; Genentech, Merck, Bristol Myers Squibb, MedImmune, Adaptive, Adaptimmune, EMD Serono, Pfizer, Takeda, Amgen, Karus, Johnson & Johnson, Bayer, Iovance, 4D, Novartis, Akoya; JHY—Salary and employment: Merck; CBB—Ownership: PrimeVax; Consulting fees: Sanofi, Agilent, Roche, Incendia, PrimeVax, BioAI, Lunaphore; Contracted research: Illumina; ME, SGr, NFG, DJ-S, JSR, MTT, ASS—Nothing to disclose; SITC Staff: BL, HS—Nothing to disclose., (© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Merkel cell carcinoma (MCC) is an aggressive cutaneous malignancy with a poor prognosis. One of the major mechanisms of immune evasion in MCC involves downregulation of major histocompatibility complex class I (MHC-I). Anti-PD-1/programmed death ligand 1 checkpoint inhibitors have revolutionized treatment for MCC, producing objective responses in approximately 50% of patients, and are now the standard of care; however, a substantial proportion of patients either fail to respond or develop resistance to checkpoint inhibitors. Given these recent successes, identification of other targetable immune checkpoints in the MCC tumor microenvironment is of great interest. Additionally, γδ T cells may play critical roles in response to MHC-I-deficient cancers; therefore, evaluating γδ T cells as a prognostic biomarker is warranted. We characterized the expression of programmed death ligand 1, PD-1, CD3, CD8, lymphocyte activation gene 3 (LAG-3), MHC-I, and γδ T cells by immunohistochemistry in a preimmunotherapy retrospective cohort of 54 cases of MCC and quantified expression levels and marker density using HALO software. The increased density of LAG-3 and γδ T cells correlated with other markers of an inflamed tumor microenvironment, with significant positive associations across all 6 markers (P < .002). Reflective of their putative role in the response to MHC-I-suppressed cancers, cases with low human leukocyte antigen I density showed a trend toward a higher ratio of γδ T cells:CD3+ T cells (Spearman r = -0.1582; P = .21). Importantly, high CD3 density (hazard ratio [HR], 0.23; P = .002), LAG-3 density (HR, 0.47; P = .037), γδ T-cell density (HR, 0.26; P = .02), and CD8 density (HR, 0.27; P = .03) showed associations with improved progression-free survival. Conditional tree analysis demonstrated that high CD8 and TCRδ expression were nonsignificant predictors of improved progression-free survival and overall survival. Overall, LAG-3 is expressed in MCC infiltrates and is prognostic in preimmunotherapy MCC, suggesting a potential role for LAG-3 inhibition in MCC. Additionally, CD8 and γδ T cells may play a critical role in the response to MCC, and γδ T-cell density may represent a novel biomarker in MCC., (Copyright © 2024. Published by Elsevier Inc.)

Spatial proteomics profiling is an emerging set of technologies that has the potential to elucidate the cell types, interactions, and molecular signatures that make up complex tissue microenvironments, with applications in the study of cancer, immunity, and much more. An emerging technique in the field is CoDetection by indEXing, recently renamed as the PhenoCycler system. This is a highly multiplexed immunofluorescence imaging technology that relies on oligonucleotide-barcoded antibodies and cyclic immunofluorescence to visualize many antibody markers in a single specimen while preserving tissue architecture. Existing PhenoCycler panels are primarily designed for fresh frozen tissues. Formalin-fixed paraffin-embedded blocks offer several advantages in preclinical research, but few antibody clones have been identified in this setting for PhenoCycler imaging. Here, we present a novel PhenoCycler panel of 28 validated antibodies for murine formalin-fixed paraffin-embedded tissues. We describe our workflow for selecting and validating clones, barcoding antibodies, designing our panel, and performing multiplex imaging. We further detail our analysis pipeline for comparing marker expressions, clustering and phenotyping single-cell proteomics data, and quantifying spatial relationships. We then apply our panel and analysis protocol to profile the effects of 3 gene delivery nanoparticle formulations, in combination with systemic anti-PD1, on the murine melanoma tumor immune microenvironment. Intralesional delivery of genes expressing the costimulatory molecule 4-1BBL and the cytokine IL-12 led to a shift toward intratumoral M1 macrophage polarization and promoted closer associations between intratumoral CD8 T cells and macrophages. Delivery of interferon gamma, in addition to 4-1BBL and IL-12, not only further increased markers of antigen presentation on tumor cells and intratumoral antigen-presenting cells but also promoted greater expression of checkpoint marker PD-L1 and closer associations between intratumoral CD8 T cells and PD-L1-expressing tumor cells. These findings help explain the benefits of 4-1BBL and IL-12 delivery while offering additional mechanistic insights into the limitations of interferon gamma therapeutic efficacy., (Copyright © 2024. Published by Elsevier Inc.)

Pathologic response is an endpoint in many ongoing clinical trials for neoadjuvant regimens, including immune checkpoint blockade and chemotherapy. Whole-slide scanning of glass slides generates high-resolution digital images and allows for remote review and potential measurement with image analysis tools, but concordance of pathologic response assessment on digital scans compared with that on glass slides has yet to be evaluated. Such a validation goes beyond previous concordance studies, which focused on establishing surgical pathology diagnoses, as it requires quantitative assessment of tumor, necrosis, and regression. Further, as pathologic response assessment is being used as an endpoint, such concordance studies have regulatory implications. The purpose of this study was 2-fold, which was as follows: first, to determine the concordance between pathologic response assessed on glass slides and that assessed on digital scans, and second, to determine if pathologists benefited from using measurement tools when determining pathologic response. To that end, hematoxylin and eosin-stained glass slides from 64 non-small cell lung carcinoma specimens were visually assessed for percent residual viable tumor (%RVT). The sensitivity and specificity for digital vs glass reads of pathologic complete response (0% RVT) and major pathologic response (≤10% RVT) were all >95%. When %RVT was considered as a continuous variable, the intraclass correlation coefficient of digital vs glass reads was 0.94. The visual assessments of pathologic response were supported by pathologist annotations of residual tumor and tumor bed areas. In a separate subset of hematoxylin and eosin-stained glass slides, several measurement approaches to quantifying %RVT were performed. Pathologist estimates strongly reflected measured %RVT. This study demonstrates the high level of concordance between glass slides evaluated using light microscopy and digital whole-slide images for pathologic response assessments. Pathologists did not require measurement tools to generate robust %RVT values from slide annotations. These findings have broad implications for improving clinical workflows and multisite clinical trials., (Copyright © 2024. Published by Elsevier Inc.)

Poly(β-amino ester) (PBAE) nanoparticles (NPs) show great promise for nonviral gene delivery. Recent studies suggest branched PBAEs (BPBAEs) offer advantages over linear counterparts, but the effect of polymer structure has not been well investigated across many chemical constituents. Here, a library of BPBAEs was synthesized with tri- and tetrafunctional branching. These polymers self-assemble with DNA to form highly cationic, monodisperse NPs with notably small size (∼50 nm). Optimal transfection occurred with polymer structures that featured moderate PBAE branching, enabling complete DNA encapsulation, rapid NP uptake, and robust expression at low DNA doses and polymer amounts. Optimized NPs enabled efficient DNA delivery to diverse cell types in vitro while maintaining high cellular viability, demonstrating significant improvements over a well-performing linear PBAE counterpart. BPBAEs also facilitated efficient mRNA and siRNA delivery, highlighting the versatility of these structures and demonstrating the broad utility of BPBAE NPs as vectors for nucleic acid delivery.

Tertiary lymphoid structures (TLS) are associated with improved response in solid tumors treated with immune checkpoint blockade, but understanding of the prognostic and predictive value of TLS and the circumstances of their resolution is incomplete. Here we show that in hepatocellular carcinoma treated with neoadjuvant immunotherapy, high intratumoral TLS density at the time of surgery is associated with pathologic response and improved relapse-free survival. In areas of tumor regression, we identify a noncanonical involuted morphology of TLS marked by dispersion of the B cell follicle, persistence of a T cell zone enriched for T cell-mature dendritic cell interactions and increased expression of T cell memory markers. Collectively, these data suggest that TLS can serve as both a prognostic and predictive marker of response to immunotherapy in hepatocellular carcinoma and that late-stage TLS may support T cell memory formation after elimination of a viable tumor., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

There is documented sex disparity in cutaneous melanoma incidence and mortality, increasing disproportionately with age and in the male sex. However, the underlying mechanisms remain unclear. While biological sex differences and inherent immune response variability have been assessed in tumor cells, the role of the tumor-surrounding microenvironment, contextually in aging, has been overlooked. Here, we show that skin fibroblasts undergo age-mediated, sex-dependent changes in their proliferation, senescence, ROS levels, and stress response. We find that aged male fibroblasts selectively drive an invasive, therapy-resistant phenotype in melanoma cells and promote metastasis in aged male mice by increasing AXL expression. Intrinsic aging in male fibroblasts mediated by EZH2 decline increases BMP2 secretion, which in turn drives the slower-cycling, highly invasive, and therapy-resistant melanoma cell phenotype, characteristic of the aged male TME. Inhibition of BMP2 activity blocks the emergence of invasive phenotypes and sensitizes melanoma cells to BRAF/MEK inhibition., Competing Interests: Declaration of interests A.T.W. is on the board of reGAIN Therapeutics and the Melanoma Research Foundation. E.M.J. reports other support from Abmeta, personal fees from Genocea, personal fees from Achilles, personal fees from DragonFly, personal fees from Candel Therapeutics, other support from the Parker Institute, grants and other support from Lustgarten, personal fees from Carta, grants and other support from Genentech, grants and other support from AstraZeneca, personal fees from NextCure, and grants and other support from Break Through Cancer outside of the submitted work. D.J.Z. reports grant funding (paid to Johns Hopkins University) from Roche/Genentech. Y.C. and M.E.F. are affiliated with the Cancer Signaling and Microenvironment program, FoxChase Cancer Center, Philadelphia, PA, USA., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Aging is a major driver of diseases in humans. Identifying features associated with aging is essential for designing robust intervention strategies and discovering novel biomarkers of aging. Extensive studies at both the molecular and organ/whole-body physiological scales have helped determined features associated with aging. However, the lack of meso-scale studies, particularly at the tissue level, limits the ability to translate findings made at molecular scale to impaired tissue functions associated with aging. In this work, we established a tissue image analysis workflow - quantitative micro-anatomical phenotyping (qMAP) - that leverages deep learning and machine vision to fully label tissue and cellular compartments in tissue sections. The fully mapped tissue images address the challenges of finding an interpretable feature set to quantitatively profile age-related microanatomic changes. We optimized qMAP for skin tissues and applied it to a cohort of 99 donors aged 14 to 92. We extracted 914 microanatomic features and found that a broad spectrum of these features, represented by 10 cores processes, are strongly associated with aging. Our analysis shows that microanatomical features of the skin can predict aging with a mean absolute error (MAE) of 7.7 years, comparable to state-of-the-art epigenetic clocks. Our study demonstrates that tissue-level architectural changes are strongly associated with aging and represent a novel category of aging biomarkers that complement molecular markers. Our results highlight the complex and underexplored multi-scale relationship between molecular and tissue microanatomic scales., Competing Interests: Conflict of Interest The authors declare no financial/commercial conflicts of interest.

Tumor immunotherapy is a promising anticancer strategy; however, tumor cells may employ resistance mechanisms, including downregulation of major histocompatibility complex (MHC) molecules to avoid immune recognition. Here, we investigate reprogramming nanoparticles (NPs) that deliver immunostimulatory genes to enhance immunotherapy and address defective antigen presentation in skin cancer in vitro and in vivo . We use a modular poly(beta-amino ester) (PBAE)-based NP to deliver DNA encoding 4-1BBL, IL-12, and IFNγ to reprogram human Merkel cell carcinoma (MCC) cells in vitro and mouse melanoma tumors in vivo to drive adaptive antitumor immune responses. Optimized NP formulations delivering 4-1BBL/IL-12 or 4-1BBL/IL-12/IFNγ DNA successfully transfect MCC and melanoma cells in vitro and in vivo , respectively, resulting in IFNγ-driven upregulation of MHC class I and II molecules on cancer cells. These NPs reprogram the tumor immune microenvironment (TIME) and elicit strong T-cell-driven immune responses, leading to cancer cell killing and T-cell proliferation in vitro and slowing tumor growth and improving survival rates in vivo . Based on expected changes to the tumor immune microenvironment, particularly the importance of IFNγ to the immune response and driving both T-cell function and exhaustion, next-generation NPs codelivering IFNγ were designed. These offered mixed benefits, exchanging improved polyfunctionality for increased T-cell exhaustion and demonstrating higher systemic toxicity in vivo . Further profiling of the immune response with these NPs provides insight into T-cell exhaustion and polyfunctionality induced by different formulations, providing a greater understanding of this immunotherapeutic strategy.

While the advent of immune-checkpoint inhibitors has revolutionized cancer therapy, immune-related adverse effects (irAEs) have also been on the rise. Cutaneous toxicities are among the most common irAEs, especially in the context of programmed cell death protein-1 (PD-1) inhibitors like pembrolizumab. Herein, we report a case of anti-PD-1-induced lichen planus pemphigoides (LPP)-a rare autoimmune blistering disorder with characteristics of both lichen planus and bullous pemphigoid. To our knowledge, this is the first reported case of LPP following anti-PD-1 therapy for metastatic adrenocortical cancer. Recognizing that LPP is within the spectrum of irAEs is important, especially as the indications for immunotherapy grow to include rarer malignancies like adrenocortical cancer. In addition to our case presentation, we also provide a comprehensive review of the literature surrounding immunotherapy-induced LPP-highlighting key characteristics towards the early recognition and clinical management of this cutaneous irAE.

Multiplex immunohistochemistry/immunofluorescence (mIHC/mIF) is a developing technology that facilitates the evaluation of multiple, simultaneous protein expressions at single-cell resolution while preserving tissue architecture. These approaches have shown great potential for biomarker discovery, yet many challenges remain. Importantly, streamlined cross-registration of multiplex immunofluorescence images with additional imaging modalities and immunohistochemistry (IHC) can help increase the plex and/or improve the quality of the data generated by potentiating downstream processes such as cell segmentation. To address this problem, a fully automated process was designed to perform a hierarchical, parallelizable, and deformable registration of multiplexed digital whole-slide images (WSIs). We generalized the calculation of mutual information as a registration criterion to an arbitrary number of dimensions, making it well suited for multiplexed imaging. We also used the self-information of a given IF channel as a criterion to select the optimal channels to use for registration. Additionally, as precise labeling of cellular membranes in situ is essential for robust cell segmentation, a pan-membrane immunohistochemical staining method was developed for incorporation into mIF panels or for use as an IHC followed by cross-registration. In this study, we demonstrate this process by registering whole-slide 6-plex/7-color mIF images with whole-slide brightfield mIHC images, including a CD3 and a pan-membrane stain. Our algorithm, WSI, mutual information registration (WSIMIR), performed highly accurate registration allowing the retrospective generation of an 8-plex/9-color, WSI, and outperformed 2 alternative automated methods for cross-registration by Jaccard index and Dice similarity coefficient (WSIMIR vs automated WARPY, P < .01 and P < .01, respectively, vs HALO + transformix, P = .083 and P = .049, respectively). Furthermore, the addition of a pan-membrane IHC stain cross-registered to an mIF panel facilitated improved automated cell segmentation across mIF WSIs, as measured by significantly increased correct detections, Jaccard index (0.78 vs 0.65), and Dice similarity coefficient (0.88 vs 0.79)., (Copyright © 2023 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

Introduction: DNA vaccines containing a fusion of the gene encoding chemokine MIP-3α (CCL20), the ligand for CCR6 on immature dendritic cells (DCs), to melanoma-associated antigen genes have enhanced anti-tumor immunity and efficacy compared to those lacking the chemokine gene. Previous work has shown that type-I interferon (IFNα or IFN) and 5-Aza-2'-deoxycytidine (5Aza) significantly enhance the therapeutic benefit of DNA vaccines as measured by reduced tumor burden and improved mouse survival., Methods: Here, we explored mouse intratumoral immune correlates underlying the therapeutic benefit of this combination regimen (vaccine, IFN, and 5Aza) as compared to vaccine alone and IFN and 5Aza without vaccine, focusing on chemokine mRNA expression by qRT-PCR and inflammatory cellular infiltration into the tumor microenvironment (TME) by flow cytometry and immunohistochemistry (IHC)., Results: The combination group significantly upregulated intratumoral mRNA expression of key immune infiltration chemokines XCL1 and CXCL10. Flow cytometric analyses of tumor suspensions exhibited greater tumor infiltration of CD8+ DCs, CCR7+ DCs, and NK cells in the combination group, as well as reduced levels of myeloid-derived suppressor cells (MDSCs) in vaccinated groups. The mice receiving combination therapy also had greater proportions of effector/memory T-cells (Tem), in addition to showing an enhanced infiltration of Tem and central memory CD8+ T-cells, (Tcm). Tem and Tcm populations both correlated with smaller tumor size. Immunohistochemical analysis of tumors confirmed that CD8+ cells were more abundant overall and especially in the tumor parenchyma with combination therapy., Discussion: Efficient targeting of antigen to immature DCs with a chemokine-fusion vaccine offers a potential alternative approach to classic and dendritic cell-based vaccines. Combining this approach with IFNα and 5Aza treatments significantly improved vaccine efficacy. This treatment creates an environment of increased inflammatory chemokines that facilitates the trafficking of CD8+ DCs, NK cells, and CD8+ T-cells, especially memory cells, while reducing the number of MDSCs. Importantly, in the combination group, CD8+ cells were more able to penetrate the tumor mass in addition to being more numerous. Further analysis of the pathways engaged by our combination therapy is expected to provide additional insights into melanoma pathogenesis and facilitate the development of novel treatment strategies., Competing Interests: Authors RM and JG are inventors on a patent 11419928 for the vaccine that has been issued to Johns Hopkins University. The remaining authors declare that the research was conducted in the absence of any further commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Gordy, Sandhu, Fessler, Luo, Kapoor, Ayeh, Hui, Schill, Chen, Wang, Karanika, Sunshine, Karakousis and Markham.)

We describe an unusual case of posttransplant tuberculosis reactivation in a man who underwent allogeneic hematopoietic cell transplant. Concomitant with disseminated adenovirus infection, reactivation of tuberculosis manifested as disseminated, nonfollicular pustules on day +49. Skin biopsy was obtained on day +50. Initial histopathologic evaluation did not suggest mycobacterial infection, but tissue stain showed acid-fast organisms, which were subsequently identified as Mycobacterium tuberculosis . Shortly after the cutaneous presentation of tuberculosis, the patient died on day +52. Our case is among a paucity of reports describing tuberculosis reactivation in hematopoietic cell transplant patients in the early posttransplant period. It highlights the difficulty of diagnosing contemporaneous systemic infections, and it presents a rare and atypical cutaneous manifestation of tuberculosis in a hematopoietic cell transplant patient. Our case and review of the literature emphasize the need for further research to elucidate risk factors associated with early posttransplant reactivation of tuberculosis, and the importance of remaining vigilant for active tuberculosis in hematopoietic cell transplant patients with epidemiologic risk factors., Competing Interests: Potential conflicts of interest. AHK reports receiving consulting fees from Roche. TJ reports institutional research support from CTI Biopharma, Syneos Health, Incyte; Consultancy with Targeted Healthcare Communications; and advisory board participation with Care Dx, Bristol Myers Squibb, Incyte, Abbvie, and CTI., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: Checkpoint immunotherapy is frequently associated with cutaneous immune-related adverse events (cirAEs), and among those, the most common subtype shows interface reaction patterns that have been likened to lichen planus (LP); however, cutaneous acute graft versus host disease (aGVHD) may be a closer histopathologic comparator. We used quantitative pathology to compare the immunologic composition of anti-PD-1-associated interface reactions to LP and aGVHD to assess for similarities and differences between these cutaneous eruptions., Methods: Immunohistochemistry for CD4, CD8, CD68, PD-1, and PD-L1 was performed on formalin-fixed paraffin-embedded tissue from patients with anti-PD-1 interface cirAEs (n = 4), LP (n = 9), or aGVHD (n = 5). Densities of immune cell subsets expressing each marker were quantified using the HALO image analysis immune cell module. Plasma cell and eosinophil density were quantified on routine H&E slides., Results: Specimens from patients with anti-PD-1 interface cirAEs showed equivalent total cell densities and immune cell composition to those with aGVHD. Patients with LP showed higher total immune cell infiltration, higher absolute T-cell densities, increased CD8 proportion, and reduced histiocytic component. The cases with the highest plasma cell counts were all anti-PD-1 interface cirAEs and aGVHD., Conclusion: The composition of immune cell subsets in anti-PD-1 interface cirAEs more closely resembles the immune response seen in aGVHD than LP within our cohort. This warrants a closer look via advanced analytics and may have implications for shared pathogenesis and potential treatment options., (© 2022 The Authors. Journal of Cutaneous Pathology published by John Wiley & Sons Ltd.)

Background and Objective: Actinic keratoses (AKs) have been described with varying color and morphology; however, no reports have demonstrated associations between color, vasculature, and inflammation. In this retrospective study, we analyze the clinical, dermoscopic, and histopathologic features of AKs to elucidate this relationship., Methods: A retrospective search for patients diagnosed with AK between January 2018 and October 2019 was performed. Clinical and dermoscopic photographs and pathology slides for all included subjects were reviewed., Results: Forty-nine images and histopathology slides were analyzed. Dermoscopy of white AKs demonstrated scale and absence of erythema with corresponding absence of inflammation on histopathology. Dermoscopy of brown AKs revealed pseudonetwork, absent scale, and a variable vessel pattern with pigment incontinence and absence of inflammation on histopathology. Red AKs had a distinct polymorphous vessel pattern and presence of erythema on dermoscopy. On histopathology, about half of samples showed increased vascularity and variable inflammation. Pink AK dermoscopy revealed a presence of erythema with corresponding presence of inflammation on histopathology., Conclusion: This report adds to our understanding of AKs and confirms that, in general, the pinker or redder the AK, the more prominent the inflammatory infiltrate and vasculature, respectively. Dermatologists should continue to use their diagnostic skills to successfully diagnose and triage AKs., (Copyright © 2021 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved.)

Successful systemic gene delivery requires specific tissue targeting as well as efficient intracellular transfection. Increasingly, research laboratories are fabricating libraries of novel nanoparticles, engineering both new biomaterial structures and composition ratios of multicomponent systems. Yet, methods for screening gene delivery vehicles directly in vivo are often low-throughout, limiting the number of candidate nanoparticles that can be investigated. Here, we report a comprehensive, high-throughput method to evaluate a library of polymeric nanoparticles in vivo for tissue-specific gene delivery. The method involves pairing each nanoparticle formulation with a plasmid DNA (pDNA) that harbors a unique nucleotide sequence serving as the identifying "barcode". Using real time quantitative PCR (qPCR) for detection of the barcoded pDNA and quantitative reverse transcription PCR (RT-qPCR) for transcribed barcoded mRNA, we can quantify accumulation and transfection in tissues of interest. The barcode pDNA and primers were designed with sufficient sensitivity and specificity to evaluate multiple nanoparticle formulations per mouse, improving screening efficiency. Using this platform, we evaluated the biodistribution and transfection of 8 intravenously administered poly(beta-amino ester; PBAE) nanoparticle formulations, each with a PBAE polymer of differential structure. Significant levels of nanoparticle accumulation and gene transfection were observed mainly in organs involved in clearance, including spleen, liver, and kidneys. Interestingly, higher levels of transfection of select organs did not necessarily correlate with higher levels of tissue accumulation, highlighting the importance of directly measuring in vivo transfection efficiency as the key barcoded parameter in gene delivery vector optimization. To validate this method, nanoparticle formulations were used individually for luciferase pDNA delivery in vivo. The distribution of luciferase expression in tissues matched the transfection analysis by the barcode qPCR method, confirming that this platform can be used to accurately evaluate systemic gene delivery., (Copyright © 2021. Published by Elsevier B.V.)

Next-generation tissue-based biomarkers for immunotherapy will likely include the simultaneous analysis of multiple cell types and their spatial interactions, as well as distinct expression patterns of immunoregulatory molecules. Here, we introduce a comprehensive platform for multispectral imaging and mapping of multiple parameters in tumor tissue sections with high-fidelity single-cell resolution. Image analysis and data handling components were drawn from the field of astronomy. Using this "AstroPath" whole-slide platform and only six markers, we identified key features in pretreatment melanoma specimens that predicted response to anti-programmed cell death-1 (PD-1)-based therapy, including CD163 + PD-L1 - myeloid cells and CD8 + FoxP3 + PD-1 low/mid T cells. These features were combined to stratify long-term survival after anti-PD-1 blockade. This signature was validated in an independent cohort of patients with melanoma from a different institution., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Abstract: Two distinct studies have shown that RET fusions are found in 3%-4% of Spitz neoplasms. RET fusions have been well described in papillary thyroid cancer, non-small-cell lung cancer, breast cancer, and soft-tissue mesenchymal tumors as well as some other neoplasms. However, there are no comprehensive descriptions to date of the characteristic morphologic, clinical, or genomic findings in RET fusion Spitz neoplasms. In this study, we identified 5 cases of RET fusion Spitz neoplasms. These tumors showed characteristic morphologic features which included plaque-like silhouette and monotonous epithelioid cytology with expansile and dyscohesive nesting. Four of 5 patients including 1 diagnosed as Spitz melanoma had clinical follow-up all of which was uneventful. Furthermore, we describe the genomic sequences in 4 of these cases, 2 of which have previously described KIF5B-RET fusion and 2 of which had a novel LMNA-RET fusion. We believe this report significantly contributes to our current knowledge regarding Spitz neoplasms and describes characteristics features which can help with recognition of the RET subgroup of Spitz., Competing Interests: Lippincott CME Institute has identified and resolved all conflicts of interest concerning this educational activity., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

The presence of a characteristic chimeric fusion as the initiating genomic event is one defining feature of Spitz neoplasms. Characterization of specific subtypes of Spitz neoplasms allows for better recognition facilitating diagnosis. Data on clinical outcomes of the specific tumor types may help in predicting behavior. In this study we present the largest series to date on ROS1 fusion Spitz neoplasms. We present the clinical, morphologic, and genomic features of 17 cases. We compared the morphologic features of these 17 cases to a cohort of 99 other non-ROS1 Spitz neoplasms to assess for features that may have high specificity for ROS1 fusions. These tumors consisted of ten Spitz nevi and seven Spitz tumors. None of the cases met criteria for a diagnosis of Spitz melanoma. Morphologically, the ROS1 fusion tumors of this series were characterized by a plaque-like or nodular silhouette, often densely cellular intraepidermal melanocyte proliferation, frequent pagetosis, tendency toward spindle cell cytomorphology, low grade nuclear atypia, and floating nests with occasional transepidermal elimination. However, there was a significant range in microscopic appearances, including two cases with morphologic features of a desmoplastic Spitz nevus. Different binding partners to ROS1 were identified with PWWP2A and TPM3 being the most common. No case had a recurrence or metastasis. Our findings document that most ROS1 fusion Spitz neoplasms have some typical characteristic microscopic features, while a small proportion will have features overlapping with other genomic subtypes of Spitz neoplasms. Preliminary evidence suggests that they tend to be indolent or low grade neoplasms.

With the advent of better molecular characterization of Spitz melanocytic neoplasms, there has been increasing effort to better understand and describe the relationships between specific driver fusion and/or mutations with the clinical and histomorphological characteristics of the lesions. Structural rearrangements in mitogen activated protein kinase genes have recently been noted to be important in Spitz neoplasms. Only very few reports, however, have described in detail melanocytic tumors with in frame deletions in MAP2K1. Cases in the literature with this aberration have been described as having a diagnosis of Spitz, deep penetrating nevi, or pigmented epithelioid melanocytoma. In this study, we describe a cohort of 6 cases with MAP2K1 activating in frame deletions. The morphologic spectrum of the cases was broad. Common features of these cases include Spitzoid cytomorphology (5/6) cases, prominent melanin pigmentation (4/6) cases, and deep penetrating nevi-like plexiform architecture (3/6) cases. The diagnoses at the time of clinical care of these cases included nevus of Reed (1/6), desmoplastic Spitz tumor (1/6), BAPoma (1/6), deep penetrating melanocytic nevus (2/6), and melanoma (1/6). Clinical follow-up was available in 3 of the 6 cases. None of the patients had a tumor recurrence. This builds on the growing literature to help expand the spectrum of changes associated with Spitzoid melanocytic neoplasms.

Background: Fusions involving the BRAF gene are responsible for 5% of Spitz neoplasms. To better characterize them, we report the clinical, morphological, and genomic findings of six BRAF fusion Spitz tumors., Methods: The morphological, clinical, and molecular findings of six BRAF fusion Spitz neoplasms assessed by next generation sequencing (NGS) were compared to a control set of Spitz without BRAF fusions., Results: BRAF fusion Spitz tumors had frequent predominance of epithelioid morphology (4/6 cases), frequent high-grade nuclear atypia and pleomorphism (5/6 cases), and a frequent desmoplastic base (3/6 cases). Five of six cases were diagnosed as atypical Spitz tumor and one as Spitz nevus. All cases had uneventful clinical follow-up. There were five different fusion partners, with CLIP2 being the most frequent. Secondary pathogenic mutations were frequent and chromosomal copy number changes were seen in three of six cases by an NGS platform., Conclusions: BRAF fusions Spitz usually have epithelioid morphology, high-grade nuclear atypia, and desmoplasia. Chromosomal copy number changes are not infrequent. While our cases had uneventful follow-up, a meta-analysis of the literature suggests that among the fusion subtypes associated with Spitz tumors, they are among the subgroups more likely to develop distant metastasis., (© 2020 John Wiley & Sons A/S . Published by John Wiley & Sons Ltd.)

In the era of immunotherapy for cancer, solid organ transplant patients who go on to develop metastatic or locally advanced melanoma offer particularly difficult challenges. New approaches are needed for these patients. We present a case of in-transit metastatic melanoma in a renal transplant patient. The patient was initially managed with talimogene laherparepvec (T-VEC) injections alone with continued local progression. Addition of topical imiquimod 5% cream to intralesional T-VEC resulted in a rapid and dramatic response, with complete clearance of the cutaneous in-transit metastases and without any sign of organ rejection. In solid organ transplant patients who lack surgical options and are not eligible for treatment with a BRAF inhibitor, and for whom treatment with checkpoint inhibitors present risk of organ rejection, T-VEC either alone or in combination with topical imiquimod should be considered for patients with locally advanced disease. This combination should be a consideration, with close observation, in patients with a history of organ transplantation and immunosuppression.

The progressive growth in nanotechnology approaches to diagnostics and therapeutics, especially for cancer, necessitates training physicians in nanoethics. This article explains why it is critical for medical education to include instruction in nanotechnology, nanomedicine, nanotoxicology, and nanoethics and suggests basic concepts educators can use to infuse curricula with this content., (© 2019 American Medical Association. All Rights Reserved.)

Background: We recently reported a 56% objective response rate in patients with advanced Merkel cell carcinoma (MCC) receiving pembrolizumab. However, a biomarker predicting clinical response was not identified., Methods: Pretreatment FFPE tumor specimens (n = 26) were stained for CD8, PD-L1, and PD-1 by immunohistochemistry/immunofluorescence (IHC/IF), and the density and distribution of positive cells was quantified to determine the associations with anti-PD-1 response. Multiplex IF was used to test a separate cohort of MCC archival specimens (n = 16), to identify cell types expressing PD-1., Results: Tumors from patients who responded to anti-PD-1 showed higher densities of PD-1+ and PD-L1+ cells when compared to non-responders (median cells/mm 2 , 70.7 vs. 6.7, p = 0.03; and 855.4 vs. 245.0, p = 0.02, respectively). There was no significant association of CD8+ cell density with clinical response. Quantification of PD-1+ cells located within 20 μm of a PD-L1+ cell showed that PD-1/PD-L1 proximity was associated with clinical response (p = 0.03), but CD8/PD-L1 proximity was not. CD4+ and CD8+ cells in the TME expressed similar amounts of PD-1., Conclusions: While the binomial presence or absence of PD-L1 expression in the TME was not sufficient to predict response to anti-PD-1 in patients with MCC, we show that quantitative assessments of PD-1+ and PD-L1+ cell densities as well as the geographic interactions between these two cell populations correlate with clinical response. Cell types expressing PD-1 in the TME include CD8+ T-cells, CD4+ T-cells, T regs , and CD20+ B-cells, supporting the notion that multiple cell types may potentiate tumor regression following PD-1 blockade.

There has been growing interest in the use of particles coated with lipids for applications ranging from drug delivery, gene delivery, and diagnostic imaging to immunoengineering. To date, almost all particles with lipid coatings have been spherical despite emerging evidence that non-spherical shapes can provide important advantages including reduced non-specific elimination and increased target-specific binding. We combine control of core particle geometry with control of particle surface functionality by developing anisotropic, biodegradable ellipsoidal particles with lipid coatings. We demonstrate that these lipid coated ellipsoidal particles maintain advantageous properties of lipid polymer hybrid particles, such as the ability for modular protein conjugation to the particle surface using versatile bioorthogonal ligation reactions. In addition, they exhibit biomimetic membrane fluidity and demonstrate lateral diffusive properties characteristic of natural membrane proteins. These ellipsoidal particles simultaneously provide benefits of non-spherical particles in terms of stability and resistance to non-specific phagocytosis by macrophages as well as enhanced targeted binding. These biomaterials provide a novel and flexible platform for numerous biomedical applications., Statement of Significance: The research reported here documents the ability of non-spherical polymeric particles to be coated with lipids to form anisotropic biomimetic particles. In addition, we demonstrate that these lipid-coated biodegradable polymeric particles can be conjugated to a wide variety of biological molecules in a "click-like" fashion. This is of interest due to the multiple types of cellular mimicry enabled by this biomaterial based technology. These features include mimicry of the highly anisotropic shape exhibited by cells, surface presentation of membrane bound protein mimetics, and lateral diffusivity of membrane bound substrates comparable to that of a plasma membrane. This platform is demonstrated to facilitate targeted cell binding while being resistant to non-specific cellular uptake. Such a platform could allow for investigations into how physical parameters of a particle and its surface affect the interface between biomaterials and cells, as well as provide biomimetic technology platforms for drug delivery and cellular engineering., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Merkel cell carcinoma (MCC) is a rare but lethal cancer with the highest case-by-case fatality rate among all skin cancers. Eighty percent of cancers are associated with the Merkel cell polyomavirus (MCPyV). Twenty percent of MCCs are virus negative. Recent epidemiological data suggest that there are important, clinically relevant differences between these two subtypes of MCC. Recent studies in cancer genomics, mouse genetics, and virology experiments have transformed our understanding of MCC pathophysiology. Importantly, dramatic differences in the genetics of these two MCC subtypes suggest fundamental differences in their pathophysiology. We review these recent works and find that they provocatively suggest that MCPyV-positive and MCPyV-negative MCCs arise from two different cells of origin: the MCPyV-negative MCC from epidermal keratinocytes and the MCPyV-positive MCC from dermal fibroblasts. If true, this would represent the first cancer that we are aware of that evolves from cells of origin from two distinct germ layers: MCPyV-negative MCCs from ectodermal keratinocytes and MCPyV-positive MCCs from mesodermal fibroblasts. Future epigenetic experiments may prove valuable in confirming these distinct lineages for these MCC subtypes, especially for the clinical importance the cell of origin has on MCC treatment and prevention.

Therapeutic cancer vaccines require adjuvants leading to robust type I interferon and proinflammatory cytokine responses in the tumor microenvironment to induce an anti-tumor response. Cyclic dinucleotides (CDNs), a potent Stimulator of Interferon Receptor (STING) agonist, are currently in phase I trials. However, their efficacy may be limited to micromolar concentrations due to the cytosolic residence of STING in the ER membrane. Here we utilized biodegradable, poly(beta-amino ester) (PBAE) nanoparticles to deliver CDNs to the cytosol leading to robust immune response at >100-fold lower extracellular CDN concentrations in vitro. The leading CDN PBAE nanoparticle formulation induced a log-fold improvement in potency in treating established B16 melanoma tumors in vivo when combined with PD-1 blocking antibody in comparison to free CDN without nanoparticles. This nanoparticle-mediated cytosolic delivery method for STING agonists synergizes with checkpoint inhibitors and has strong potential for enhanced cancer immunotherapy., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Purpose: PD-L1 expression in the pretreatment tumor microenvironment enriches for response to anti-PD-1/PD-L1 therapies. The purpose of this study was to quantitatively compare the performance of five monoclonal anti-PD-L1 antibodies used in recent landmark publications. Experimental Design: PD-L1 IHC was performed on 34 formalin-fixed paraffin-embedded archival melanoma samples using the 5H1, SP142, 28-8, 22C3, and SP263 clones. The percentage of total cells (including melanocytes and immune cells) demonstrating cell surface PD-L1 staining, as well as intensity measurements/ H -scores, were assessed for each melanoma specimen using a computer-assisted platform. Staining properties were compared between antibodies. Results: Strong correlations were observed between the percentage of PD-L1(+) cells across all clones studied ( R 2 = 0.81-0.96). When present, discordant results were attributable to geographic heterogeneity of the melanoma tissue section rather than differences in PD-L1 antibody staining characteristics. PD-L1 intensity/ H -scores strongly correlated with percentage of PD-L1(+) cells ( R 2 > 0.78, all clones). Conclusions: The 5H1, SP142, 28-8, 22C3, and SP263 clones all demonstrated similar performance characteristics when used in a standardized IHC assay on melanoma specimens. Reported differences in PD-L1 IHC assays using these antibodies are thus most likely due to assay characteristics beyond the antibody itself. Our findings also argue against the inclusion of an intensity/ H -score in chromogenic PD-L1 IHC assays. Clin Cancer Res; 23(16); 4938-44. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Background: Merkel-cell carcinoma is an aggressive skin cancer that is linked to exposure to ultraviolet light and the Merkel-cell polyomavirus (MCPyV). Advanced Merkel-cell carcinoma often responds to chemotherapy, but responses are transient. Blocking the programmed death 1 (PD-1) immune inhibitory pathway is of interest, because these tumors often express PD-L1, and MCPyV-specific T cells express PD-1., Methods: In this multicenter, phase 2, noncontrolled study, we assigned adults with advanced Merkel-cell carcinoma who had received no previous systemic therapy to receive pembrolizumab (anti-PD-1) at a dose of 2 mg per kilogram of body weight every 3 weeks. The primary end point was the objective response rate according to Response Evaluation Criteria in Solid Tumors, version 1.1. Efficacy was correlated with tumor viral status, as assessed by serologic and immunohistochemical testing., Results: A total of 26 patients received at least one dose of pembrolizumab. The objective response rate among the 25 patients with at least one evaluation during treatment was 56% (95% confidence interval [CI], 35 to 76); 4 patients had a complete response, and 10 had a partial response. With a median follow-up of 33 weeks (range, 7 to 53), relapses occurred in 2 of the 14 patients who had had a response (14%). The response duration ranged from at least 2.2 months to at least 9.7 months. The rate of progression-free survival at 6 months was 67% (95% CI, 49 to 86). A total of 17 of the 26 patients (65%) had virus-positive tumors. The response rate was 62% among patients with MCPyV-positive tumors (10 of 16 patients) and 44% among those with virus-negative tumors (4 of 9 patients). Drug-related grade 3 or 4 adverse events occurred in 15% of the patients., Conclusions: In this study, first-line therapy with pembrolizumab in patients with advanced Merkel-cell carcinoma was associated with an objective response rate of 56%. Responses were observed in patients with virus-positive tumors and those with virus-negative tumors. (Funded by the National Cancer Institute and Merck; ClinicalTrials.gov number, NCT02267603.).

In recent years, there have been major advances in the development of novel nanoparticle- and microparticle-based therapeutics. An emerging paradigm is the incorporation of biomimetic features into these synthetic therapeutic constructs to enable them to better interface with biological systems. Through the control of size, shape, and material consistency, particle cores have been generated that better mimic natural cells and viruses. In addition, there have been significant advances in biomimetic surface functionalization of particles through the integration of bio-inspired artificial cell membranes and naturally derived cell membranes. Biomimetic technologies enable therapeutic particles to have increased potency to benefit human health., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Non-spherical nanodimensional artificial antigen presenting cells (naAPCs) offer the potential to systemically induce an effective antigen-specific immune response. In this report it is shown biodegradable ellipsoidal naAPCs mimic the T-Cell/APC interaction better than equivalent spherical naAPCs. In addition, it is demonstrated ellipsoidal naAPCs offer reduced non-specific cellular uptake and a superior pharmacokinetic profile compared to spherical naAPCs., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Successful gene delivery with nonviral particles has several barriers, including cellular uptake, endosomal escape, and nuclear transport. Understanding the mechanisms behind these steps is critical to enhancing the effectiveness of gene delivery. Polyplexes formed with poly(β-amino ester)s (PBAEs) have been shown to effectively transfer DNA to various cell types, but the mechanism of their cellular uptake has not been identified. This is the first study to evaluate the uptake mechanism of PBAE polyplexes and the dependence of cellular uptake on the end group and molecular weight of the polymer. We synthesized three different analogues of PBAEs with the same base polymer poly(1,4-butanediol diacrylate-co-4-amino-1-butanol) (B4S4) but with small changes in the end group or molecular weight. We quantified the uptake and transfection efficiencies of the pDNA polyplexes formulated from these polymers in hard-to-transfect triple negative human breast cancer cells (MDA-MB 231). All polymers formed positively charged (10-17 mV) nanoparticles of ∼200 nm in size. Cellular internalization of all three formulations was inhibited the most (60-90% decrease in cellular uptake) by blocking caveolae-mediated endocytosis. Greater inhibition was shown with polymers that had a 1-(3-aminopropyl)-4-methylpiperazine end group (E7) than the others with a 2-(3-aminopropylamino)-ethanol end group (E6) or higher molecular weight. However, caveolae-mediated endocytosis was generally not as efficient as clathrin-mediated endocytosis in leading to transfection. These findings indicate that PBAE polyplexes can be used to transfect triple negative human breast cancer cells and that small changes to the same base polymer can modulate their cellular uptake and transfection routes.

Previous work developing particle-based acellular, artificial antigen presenting cells (aAPCs) has focused exclusively on spherical platforms. To explore the role of shape, we generated ellipsoidal PLGA microparticles with varying aspect ratios (ARs) and synthesized aAPCs from them. The ellipsoidal biomimetic aAPCs with high-AR showed significantly enhanced in vitro and in vivo activity above spherical aAPCs with particle volume and antigen content held constant. Confocal imaging indicates that CD8+ T cells preferentially migrate to and are activated by interaction with the long axis of the aAPC. Importantly, enhanced activity of high-AR aAPCs was seen in a mouse melanoma model, with high-AR aAPCs improving melanoma survival compared to non-cognate aAPCs (p = 0.004) and cognate spherical aAPCs (p = 0.05). These findings indicate that particle geometry is a critical design criterion in the generation of aAPCs, and may offer insight into the essential role of geometry in the interaction between CD8+ T cells and biological APCs., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Artificial antigen-presenting cells (aAPCs) have shown great initial promise for ex vivo activation of cytotoxic T cells. The development of aAPCs has focused mainly on the choice of proteins to use for surface presentation to T cells when conjugated to various spherical, microscale particles. We review here biomimetic nanoengineering approaches that have been applied to the development of aAPCs that move beyond initial concepts about aAPC development. This article also discusses key technologies that may be enabling for the development of nano- and micro-scale aAPCs with nanoscale features, and suggests several future directions for the field.

Polymeric vectors for gene delivery are a promising alternative for clinical applications, as they are generally safer than viral counterparts. Our objective was to further our mechanistic understanding of polymer structure-function relationships to allow the rational design of new biomaterials. Utilizing poly(β-amino ester)s (PBAEs), we investigated polymer-DNA binding by systematically varying the polymer molecular weight, adding single carbons to the backbone and side chain of the monomers that constitute the polymers, and varying the type of polymer end group. We then sought to correlate how PBAE binding affects the polyplex diameter and ζ potential, the transfection efficacy, and its associated cytotoxicity in human breast and brain cancer cells in vitro. Among other trends, we observed in both cell lines that the PBAE-DNA binding constant is biphasic with the transfection efficacy and that the optimal values of the binding constant with respect to the transfection efficacy are in the range (1-6) × 10(4) M(-1). A binding constant in this range is necessary but not sufficient for effective transfection.

Development of nonviral particles for gene delivery requires a greater understanding of the properties that enable gene delivery particles to overcome the numerous barriers to intracellular DNA delivery. Linear poly(beta-amino) esters (PBAE) have shown substantial promise for gene delivery, but the mechanism behind their effectiveness is not well quantified with respect to these barriers. In this study, we synthesized, characterized, and evaluated for gene delivery an array of linear PBAEs that differed by small changes along the backbone, side chain, and end group of the polymers. We examined particle size and surface charge, polymer molecular weight, polymer degradation rate, buffering capacity, cellular uptake, transfection, and cytotoxicity of nanoparticles formulated with these polymers. Significantly, this is the first study that has quantified how small differential structural changes to polymers of this class modulate buffering capacity and polymer degradation rate and relates these findings to gene delivery efficacy. All polymers formed positively charged (zeta potential 21-29 mV) nanosized particles (∼150 nm). The polymers hydrolytically degraded quickly in physiological conditions, with half-lives ranging from 90 min to 6 h depending on polymer structure. The PBAE buffering capacities in the relevant pH range (pH 5.1-7.4) varied from 34% to 95% protonatable amines, and on a per mass basis, PBAEs buffered 1.4-4.6 mmol of H(+)/g. When compared to 25 kDa branched polyethyleneimine (PEI), PBAEs buffer significantly fewer protons/mass, as PEI buffers 6.2 mmol of H(+)/g over the same range. However, due to the relatively low cytotoxicity of PBAEs, higher polymer mass can be used to form particles than with PEI and total buffering capacity of PBAE-based particles significantly exceeds that of PEI. Uptake into COS-7 cells ranged from 0% to 95% of cells and transfection ranged from 0% to 93% of cells, depending on the base polymer structure and the end modifications examined. Five polymers achieved higher uptake and transfection efficacy with less toxicity than branched-PEI control. Surprisingly, acrylate-terminated base polymers were dramatically less efficacious than their end-capped versions, in terms of both uptake (1-3% for acrylate, 75-94% for end-capped) and transfection efficacy (0-1% vs 20-89%), even though there are minimal differences between acrylate and end-capped polymers in terms of DNA retardation in gel electrophoresis, particle size, zeta potential, and cytotoxicity. These studies further elucidate the role of polymer structure for gene delivery and highlight that small molecule end-group modification of a linear polymer can be critical for cellular uptake in a manner that is largely independent of polymer/DNA binding, particle size, and particle surface charge.

Endothelial cell dysfunction is a critical component of ocular diseases such as age-related macular degeneration and diabetic retinopathy. An important limitation in endothelial cell research is the difficulty in achieving efficient transfection of these cells. A new polymer library was here synthesized and utilized to find polymeric nanoparticles that can transfect macrovascular (human umbilical vein, HUVECs) and microvascular (human retinal, HRECs) endothelial cells. Nanoparticles were synthesized that can achieve transfection efficiency of up to 85% for HRECs and 65% for HUVECs. These nanoparticle systems enable high levels of expression while avoiding problems associated with viral gene delivery. The polymeric nanoparticles also show cell-specific behavior, with a high correlation between microvascular and macrovascular transfection (R(2) = 0.81) but low correlation between retinal endothelial and retinal epithelial transfection (R(2) = 0.21). These polymeric nanoparticles can be used in vitro as experimental tools and potentially in vivo to target and treat vascular-specific diseases., From the Clinical Editor: Polymeric nanoparticles were synthesized with the goal of transfecting endothelial cells, which are commonly considered difficult targets. The authors report excellent transfection efficiency of up to 85% for human retinal and 65% for human umbilical vein endothelial cells. These NPs can be used in vitro as experimental tools and potentially in vivo to target and treat vascular-specific diseases., (Copyright © 2012 Elsevier Inc. All rights reserved.)

A variety of genetic diseases in the retina, including retinitis pigmentosa and leber congenital amaurosis, might be excellent targets for gene delivery as treatment. A major challenge in non-viral gene delivery remains finding a safe and effective delivery system. Poly(beta-amino ester)s (PBAEs) have shown great potential as gene delivery reagents because they are easily synthesized and they transfect a wide variety of cell types with high efficacy in vitro. We synthesized a combinatorial library of PBAEs and evaluated them for transfection efficacy and toxicity in retinal pigment epithelial (ARPE-19) cells to identify lead polymer structures and transfection formulations. Our optimal polymer (B5-S5-E7 at 60 w/w polymer:DNA ratio) transfected ARPE-19 cells with 44±5% transfection efficacy, significantly higher than with optimized formulations of leading commercially available reagents Lipofectamine 2000 (26±7%) and X-tremeGENE HP DNA (22±6%); (p<0.001 for both). Ten formulations exceeded 30% transfection efficacy. This high non-viral efficacy was achieved with comparable cytotoxicity (23±6%) to controls; optimized formulations of Lipofectamine 2000 and X-tremeGENE HP DNA showed 15±3% and 32±9% toxicity respectively (p>0.05 for both). Our optimal polymer was also significantly better than a gold standard polymeric transfection reagent, branched 25 kDa polyethyleneimine (PEI), which achieved only 8±1% transfection efficacy with 25±6% cytotoxicity. Subretinal injections using lyophilized GFP-PBAE nanoparticles resulted in 1.1±1×10(3)-fold and 1.5±0.7×10(3)-fold increased GFP expression in the retinal pigment epithelium (RPE)/choroid and neural retina respectively, compared to injection of DNA alone (p = 0.003 for RPE/choroid, p<0.001 for neural retina). The successful transfection of the RPE in vivo suggests that these nanoparticles could be used to study a number of genetic diseases in the laboratory with the potential to treat debilitating eye diseases.

A new 320-member polymer library of end-modified poly(β-amino ester)s was synthesized. This library was chosen such that small differences to the structures of component backbone, side-chain, and end-group monomers could be systematically and simultaneously evaluated. The in vitro transfection efficacy and cytotoxicity of DNA nanoparticles formed from this library were assessed. This library approach not only enabled us to synthesize and test a large variety of structures rapidly but also provided us with a robust data set to analyze for the effect of small structural permutations to polymer chain structure. Small changes to the side chains, backbones, and end groups within this polymer library produced dramatic results, with transfection efficacy of CMV-Luc varying over 4 orders in a 96-well plate format. Increasing hydrophobicity of the base polymer backbone and side chain tended to increase transfection efficacy, but the most hydrophobic side chains and backbones showed the least requirement for a hydrophobic pair. Optimal PBAE formulations were superior to commercially available nonviral alternatives FuGENE HD and Lipofectamine 2000, enabling ~3-fold increased luminescence (2.2 × 10(6) RLU/well vs 8.1 × 10(5) RLU/well) and 2-fold increased transfection percentage (76.7% vs 42.9%) as measured by flow cytometry with comparable or reduced toxicity.

Glioblastoma (GB) is currently characterized by low survival rates and therapies with insufficient efficacy. Here, we describe biodegradable polymers that can deliver genes to primary GB cells as well as GB tumor stem cells in vitro with low non-specific toxicity and transfection efficiencies of up to 60.6 ± 5% in normal (10%) serum conditions. We developed polymer-DNA nanoparticles that remained more stable in normal serum and could also be stored for at least 3 months in ready-to-use form with no measurable decrease in efficacy, expanding their potential in a practical or clinical setting. A subset of polymers was identified that shows a high degree of specificity to tumor cells compared with healthy astrocytes and human neural stem cells when cultured (separately or in co-culture), yielding higher transfection in GB cells while having little to no apparent effect on healthy cells., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Introduction: Angiogenesis is essential to human biology and of great clinical significance. Excessive or reduced angiogenesis can result in, or exacerbate, several disease states, including tumor formation, exudative age-related macular degeneration (AMD) and ischemia. Innovative drug delivery systems can increase the effectiveness of therapies used to treat angiogenesis-related diseases., Areas Covered: This paper reviews the basic biology of angiogenesis, including current knowledge about its disruption in diseases, with the focus on cancer and AMD. Anti- and proangiogenic drugs available for clinical use or in development are also discussed, as well as experimental drug delivery systems that can potentially improve these therapies to enhance or reduce angiogenesis in a more controlled manner., Expert Opinion: Laboratory and clinical results have shown pro- or antiangiogenic drug delivery strategies to be effective in drastically slowing disease progression. Further research in this area will increase the efficacy, specificity and duration of these therapies. Future directions with composite drug delivery systems may make possible targeting of multiple factors for synergistic effects.

Nonviral systems for nucleic acid delivery offer a host of potential advantages compared with viruses, including reduced toxicity and immunogenicity, increased ease of production and less stringent vector size limitations, but remain far less efficient than their viral counterparts. In this article we review recent advances in the delivery of nucleic acids using polymeric and inorganic vectors. We discuss the wide range of materials being designed and evaluated for these purposes while considering the physical requirements and barriers to entry that these agents face and reviewing recent novel approaches towards improving delivery with respect to each of these barriers. Furthermore, we provide a brief overview of past and ongoing nonviral gene therapy clinical trials. We conclude with a discussion of multifunctional nucleic acid carriers and future directions.

Non-viral gene delivery vectors were developed for efficient gene transfer to hard-to-transfect mouse mammary epithelial cells. Ten modified versions of the same base poly(beta-amino ester), poly(1,4-butanediol diacrylate-co-5-amino-1-pentanol), were tested in both traditional 2-D monolayer and in 3-D organotypic cultures. The polymers self-assembled with plasmid DNA encoding enhanced green fluorescent protein to form nanoparticles (approximately 100 nm) used to transfect the cells. Nanoparticle transfection efficacy was tuned by changes in synthesis and fabrication conditions and the transfection efficacy was analyzed using confocal microscopy and flow cytometry. The best performing polymeric nanoparticles transfected 57 +/- 6% of the cells in 2-D culture and 6 +/- 1% of the cells in 3-D culture. Small modifications to the polymer end-capping molecules and tuning of polymer molecular weight could either significantly enhance the transfection efficacy up to 6-fold or instead abolish efficacy completely. The efficacy of leading polymers was higher than that of the commercial transfection agent FuGENE HD by a factor of 13 in 2-D and 2 in 3-D. These non-viral nanoparticles may be useful as delivery reagents or targeted therapeutics for breast cancer. This gene delivery strategy is also a promising approach for studying the normal development of the mammary gland., (Copyright 2010 Elsevier Ltd. All rights reserved.)