Search

Merkel cell carcinoma (MCC) is a neuroendocrine tumor either induced by integration of the Merkel cell polyomavirus into the cell genome or by accumulation of UV-light-associated mutations (VP-MCC and UV-MCC). Whether VP- and UV-MCC have the same or different cellular origins is unclear; with mesenchymal or epidermal origins discussed. DNA-methylation patterns have a proven utility in determining cellular origins of cancers. Therefore, we used this approach to uncover evidence regarding the cell of origin of classical VP- and UV-MCC cell lines, i.e., cell lines with a neuroendocrine growth pattern (n = 9 and n = 4, respectively). Surprisingly, we observed high global similarities in the DNA-methylation of UV- and VP-MCC cell lines. CpGs of lower methylation in VP-MCC cell lines were associated with neuroendocrine marker genes such as SOX2 and INSM1, or linked to binding sites of EZH2 and SUZ12 of the polycomb repressive complex 2, i.e., genes with an impact on carcinogenesis and differentiation of neuroendocrine cancers. Thus, the observed differences appear to be rooted in viral compared to mutation-driven carcinogenesis rather than distinct cells of origin. To test this hypothesis, we used principal component analysis, to compare DNA-methylation data from different epithelial and non-epithelial neuroendocrine cancers and established a scoring model for epithelial and neuroendocrine characteristics. Subsequently, we applied this scoring model to the DNA-methylation data of the VP- and UV-MCC cell lines, revealing that both clearly scored as epithelial cancers. In summary, our comprehensive analysis of DNA-methylation suggests a common epithelial origin of UV- and VP-MCC cell lines., (© 2021. The Author(s).)

Background: Based on its viral-associated or UV-associated carcinogenesis, Merkel cell carcinoma (MCC) is a highly immunogenic skin cancer. Thus, clinically evident MCC occurs either in immuno-compromised patients or based on tumor-intrinsic immune escape mechanisms. This notion may explain that although advanced MCC can be effectively restrained by treatment with PD-1/PD-L1 immune checkpoint inhibitors (ICIs), a considerable percentage of patients does not benefit from ICI therapy. Biomarkers predicting ICI treatment response are currently not available., Methods: The present multicenter retrospective study investigated clinical and molecular characteristics in 114 patients with unresectable MCC at baseline before treatment with ICI for their association with therapy response (best overall response, BOR). In a subset of 21 patients, pretreatment tumor tissue was analyzed for activation, differentiation and spatial distribution of tumor infiltrating lymphocytes (TIL)., Results: Of the 114 patients, n=74 (65%) achieved disease control (BOR=complete response/partial response/stable disease) on ICI. A Bayesian cumulative ordinal regression model revealed absence of immunosuppression and a limited number of tumor-involved organ systems was highly associated with a favorable therapy response. Unimpaired overall performance status, high age, normal serum lactate dehydrogenase and normal serum C reactive protein were moderately associated with disease control. While neither tumor Merkel cell polyomavirus nor tumor PD-L1 status showed a correlation with therapy response, treatment with anti-PD-1 antibodies was associated with a higher probability of disease control than treatment with anti-PD-L1 antibodies. Multiplexed immunohistochemistry demonstrated the predominance of CD8 + effector and central memory T cells (T CM ) in close proximity to tumor cells in patients with a favorable therapy response., Conclusions: Our findings indicate the absence of immunosuppression, a limited number of tumor-affected organs, and a predominance of CD8 + T CM among TIL, as baseline parameters associated with a favorable response to PD-1/PD-L1 ICI therapy of advanced MCC. These factors should be considered when making treatment decisions in MCC patients., Competing Interests: Competing interests: SU declares research support from Bristol Myers Squibb and Merck Serono; speakers and advisory board honoraria from Bristol Myers Squibb, Merck Sharp & Dohme, Merck Serono, Novartis and Roche, and travel support from Bristol Myers Squibb, and Merck Sharp & Dohme. LZ served as consultant and/or has received honoraria from Roche, Bristol-Myers Squibb, Merck Sharp & Dohme, Novartis, Pierre-Fabre, and Sanofi; Research funding to institution: Novartis; travel support from Merck Sharp & Dohme, Bristol-Myers Squibb, Amgen, Pierre-Fabre, and Novartis, outside the submitted work. PT declares invited speaker's honoraria from Bristol-Myers Squibb, Novartis, MSD, Pierre-Fabre, CureVac, Roche, Kyowa Kirin, Biofrontera, advisory board honoraria from Bristol-Myers Squibb, Novartis, Pierre-Fabre, Merck Serono, Sanofi, Roche, Kyowa Kirin, and travel support from Bristol-Myers Squibb, and Pierre-Fabre. UL declares advisory board honoraria from MSD, Roche, Sanofi, Novartis, Sun Pharma, Almirall Hermal. TE declares consulting fees from BMS, Novartis, Roche, Pierre Fabre, Sanofi; board membership and payment for lectures in speakers bureau from Pierre Fabre, MSD, Roche, BMS, Novartis and Sanofi. CL reports advisory board honoraria from MSD, BMS, Roche, Pierre Fabre, Novartis, Sun Pharma, Sanofi, Kyowa Kirin, Almiral Hermal, Biontech, Merc; speakers fee from MSD, BMS, Roche, Pierre Fabre, Novartis, Sun Pharma, Sanofi, Merck; travel reimbusment from MSD, BMS, Roche, Pierre Fabre, Novartis, Sun Pharma, Sanofi, Kyowa Kirin, Almiral Hermal, Biontech and Merck. JCH declares research support from Bristol Myers Squibb; advisory board honoraria from Pierre Fabre, Sanofi, Sun Pharma and Merck Sharp & Dome; speakers honoraria from Bristol Myers Squibb, Merck Sharp & Dohme, Novartis, Roche, Sanofi and Almirall and travel support from Pierre Fabre. TG reports receiving speakers and/or advisory board honoraria from BMS, Sanofi-Grenzyme, MSD, Novartis Pharma, Roche, Abbvie, Almirall, Janssen Lilly, Pfizer, Pierre Fabre; speakers and/or advisory board honoraria from BMS, Sanofi-Grenzyme, MSD, Novartis, Pharma, Roche, Abbvie, Almirall, Janssen Lillly, Pfizer, Pierre Fabre. SH declares advisory boards honoraria from Pierre Fabre, MSD, BMS, Novartis, Sanofi. PM reports board membership and payment for lectures in speakers bureau from Pierre Fabre, GSK, MSD, Merck Germany, Roche, BMS, Novartis, Sanofi. P. Mohr reports research support (to institution): Bristol-MyersSquibb, Novartis, MSD. Honoraria for lectures (personally): Pierre Fabre, GSK, MSD, Merck Germany, Roche, BMS, Novartis, Sanofi, Amgen, SUN-Pharma, Roche Pharma, Bristol-MyersSquibb, Novartis, MSD, Almirall-Hermal, Amgen, Merck-Serono, Bayer, Pierre-Fabre, Sanofi. Honoraria for advisory boards: Pierre Fabre, GSK, MSD, Merck Germany, Roche, BMS, Novartis, Sanofi, Beiersdorf, Almiral-Hermal, AmgenBayersdorf, Roche Pharma, Bristol-MyersSquibb, Novartis, MSD, Almirall-Hermal, Amgen, Pierre-Fabre, Merck-Serono, SUN-Pharma, SUN, Merck-Serono, Sanofi. CP received honoraria (speaker honoraria or honoraria as a consultant) and travel support from Novartis, BMS, Roche, Merck Serono, MSD, Celgene, AbbVie, AMGEN, SUNPHARMA, Allergy Therapeutics and LEO. LMH served as consultant and/or has received honoraria from Amgen, BMS, Curevac, MSD, Novartis, Pierre-Fabre, Roche, Sanofi and Sun Pharma, outside the submitted work. Research funding to institution: Novartis. R. Gutzmer reports research support from Pfizer, Johnson & Johnson, Novartis, Amgen, MerckSerono, SUN Pharma; honoraria for lectures from Roche Pharma, Bristol-MyersSquibb, Novartis, MSD, Almirall-Hermal, Amgen, Merck-Serono, SUN, Pierre-Fabre, Sanofi, SUN Pharma, Bayer; honoraria for advice from Roche Pharma, Bristol-MyersSquibb, Novartis, MSD, Almirall-Hermal, Amgen, Pierre-Fabre, Merck-Serono, 4SC, Incyte, SUN Pharma, Sanofi, Pfizer. JSU is on the advisory board or has received honoraria and travel support from Amgen, Bristol Myers Squibb, GSK, LeoPharma, Merck Sharp and Dohme, Novartis, Pierre Fabre, Roche, Sanofi outside the submitted work. H-US is an employee of Targos Molecular Pathology Inc. and reports research support from Novartis Oncology and received honoraria from MSD, BMS, Roche Pharma, Novartis Oncology, AstraZeneca, Eisai, Takeda, Molecular Health, outside of the submitted work. DS reports personal fees from Amgen, GSK, BMS, Novartis, Roche, Merck, Astra Zeneca, Merck-Serono, Pfizer, Incyte, Array Pierre Fabre, Sanofi Genzyme, Regeneron, 4Sc, InFlaRx, Neracare, Ultimovacs, SunPharma, Philogen, Immunocore, Sandoz-Hexal outside the submitted work. JCB is receiving speaker's bureau honoraria from Amgen, Pfizer, MerckSerono, Recordati and Sanofi; is a paid consultant/advisory board member/DSMB member for Almirall, Boehringer Ingelheim, InProTher, ICON, MerckSerono, Pfizer, 4SC, and Sanofi/Regeneron. His group receives research grants from Bristol-Myers Squibb, Merck Serono, HTG, IQVIA, and Alcedis., (© Author(s) (or their employer(s)) 2022. 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 neuroendocrine skin cancer characterized by high invasiveness, early metastases, and high mortality. Because of the lack of suitable animal models, most functional studies are performed using cell lines, some of which lack classical neuroendocrine growth characteristics. Here, we scrutinized the molecular characteristics of classical MCC and variant MCC cell lines by differential gene expression and the respective epigenetic regulation by microRNAs and DNA methylation. Cutaneous squamous cell carcinoma cell lines were used for comparison. The most striking observation was a lower expression of epithelial-mesenchymal transition-related genes in classical MCCs, which was accompanied by higher expression of the epithelial-mesenchymal transition-regulating microRNA clusters miR-200c-141 and miR-183-96-182 and hypomethylation of the respective microRNA loci. Experimental expression of the MCC lineage factor ATOH1 in variant MCCs resulted in an increased expression of miR-200c-141 paralleled by a reduction of genes associated with epithelial-mesenchymal transition, thus demonstrating a connection between neuroendocrine characteristics and the lack of epithelial-mesenchymal transition. Together, our observations not only reinforce concerns about the use of variant MCCs as proper MCC representatives, but also suggest variant MCCs as cells locked in an intermediate state between neuroendocrine and epithelial differentiation., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Merkel cell carcinoma (MCC) is a rare, highly aggressive skin cancer for which immune modulation by immune checkpoint inhibitors shows remarkable response rates. However, primary or secondary resistance to immunotherapy prevents benefits in a significant proportion of patients. For MCC, one immune escape mechanism is insufficient for recognition by T cells owing to the downregulation of major histocompatibility complex I surface expression. Histone deacetylase inhibitors have been demonstrated to epigenetically reverse the low major histocompatibility complex I expression caused by the downregulation of the antigen-processing machinery. Domatinostat, an orally available small-molecule inhibitor targeting histone deacetylase class I, is currently in clinical evaluation to overcome resistance to immunotherapy. In this study, we present preclinical data on domatinostat's efficacy and mode of action in MCC. Single-cell RNA sequencing revealed a distinct gene expression signature of antigen processing and presentation, cell-cycle arrest, and execution phase of apoptosis on treatment. Accordingly, functional assays showed that domatinostat induced G2M arrest and apoptosis. In the surviving cells, antigen-processing machinery component gene transcription and translation were upregulated, consequently resulting in increased major histocompatibility complex I surface expression. Altogether, domatinostat not only exerts direct antitumoral effects but also restores HLA class I surface expression on MCC cells, therefore, restoring surviving MCC cells' susceptibility to recognition and elimination by cognate cytotoxic T cells., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Merkel cell carcinoma (MCC) is a highly invasive and metastatic skin cancer. While high expression of miR-375 is a characteristic of MCC, it seems not to contribute to the malignant phenotype of MCC cells. miR-375 enrichment in MCC-derived extracellular vesicles suggests its intercellular signaling function. Here, we demonstrate that horizontally transferred miR-375 causes fibroblast polarization toward cancer-associated fibroblasts (CAFs). The polarization is evidenced by phenotypic changes and induction of α-SMA, CXCL2, and IL-1β. Fibroblast polarization is inhibited by specific antagomirs and mimicked by experimental miR-375 expression. Mechanistically, miR-375 downregulates RBPJ and p53, two key players regulating fibroblast polarization. In clinical MCC samples, in situ hybridization located miR-375 in CAFs, which correlated with high α-SMA protein and low RBPJ and TP53 expression; single-cell RNAseq revealed a disparate fibroblast polarization negatively correlating with p53 pathway-related gene expression. Thus, the functional role of miR-375 in MCC is to generate a pro-tumorigenic microenvironment by inducing fibroblast polarization.

The integrity of the immune system represents a pivotal risk factor and prognostic biomarker for Merkel cell carcinoma. A higher density of tumor-associated T cells correlates with improved Merkel cell carcinoma-specific survival, but the prognostic importance of the T-cell infiltrate reactivity is unknown. We evaluated the T-cell receptor repertoire associated with 72 primary Merkel cell carcinomas and correlated metrics of the T-cell receptor repertoire with clinicopathologic characteristics and patient outcomes. We showed that a high Simpson's Dominance index (SDom) was significantly associated with fewer metastases (P = 0.01), lower stage at presentation (P = 0.02), lower final stage at last follow-up (P = 0.05), and longer time to first lymph node metastasis (P = 0.04). These correlations were mostly preserved in the Merkel cell polyomavirus-negative subgroup. Combining SDom with CD3 + or CD8 + T-cell density revealed three distinct prognostic groups with respect to disease-specific survival. Patients with both high SDom and high CD3 + or CD8 + T-cell density had markedly improved disease-specific survival compared with patients with low SDom and low CD3 + or CD8 + T-cell density (P = 0.002 and P = 0.03, respectively). Patients with either high SDom or high CD3 + or CD8 + had intermediate disease-specific survival. Our findings demonstrate that the quality of the tumor-associated T-cell infiltrate informs patient prognosis in primary Merkel cell carcinoma beyond the T-cell density., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer, which can be effectively controlled by immunotherapy with PD-1/PD-L1 checkpoint inhibitors. However, a significant proportion of patients are characterized by primary therapy resistance. Predictive biomarkers for response to immunotherapy are lacking., Experimental Design: We applied Bayesian inference analyses on 41 patients with MCC testing various clinical and biomolecular characteristics to predict treatment response. Further, we performed a comprehensive analysis of tumor tissue-based immunologic parameters including multiplexed immunofluorescence for T-cell activation and differentiation markers, expression of immune-related genes and T-cell receptor (TCR) repertoire analyses in 18 patients, seven objective responders, and 11 nonresponders., Results: Bayesian inference analyses demonstrated that among currently discussed biomarkers only unimpaired overall performance status and absence of immunosuppression were associated with response to therapy. However, in responders, a predominance of central memory T cells and expression of genes associated with lymphocyte attraction and activation was evident. In addition, TCR repertoire usage of tumor-infiltrating lymphocytes (TILs) demonstrated low T-cell clonality, but high TCR diversity in responding patients. In nonresponders, terminally differentiated effector T cells with a constrained TCR repertoire prevailed. Sequential analyses of tumor tissue obtained during immunotherapy revealed a more pronounced and diverse clonal expansion of TILs in responders indicating an impaired proliferative capacity among TILs of nonresponders upon checkpoint blockade., Conclusions: Our explorative study identified new tumor tissue-based molecular characteristics associated with response to anti-PD-1/PD-L1 therapy in MCC. These observations warrant further investigations in larger patient cohorts to confirm their potential value as predictive markers., (©2020 American Association for Cancer Research.)

Background: Merkel cell carcinoma (MCC) is an aggressive skin cancer in which PD-1/PD-L1 blockade has shown remarkable response rates. However, a significant proportion of patients shows primary or secondary resistance against PD-1/PD-L1 inhibition, with HLA class-I downregulation and insufficient influx of CD8 + T cells into the tumor as possible immune escape mechanisms. Histone deacetylase inhibitors (HDACi) have been demonstrated to reverse low HLA class-I expression caused by epigenetic downregulation of the antigen machinery (APM) in vitro and in pre-clinical models in vivo., Case Presentations: We report four cases of patients with metastatic MCC who did not respond to immunotherapy by PD-1/PD-L1 blockade. Two of the patients received, subsequently, the HDACi panobinostat in combination with PD-1/PD-L1 blockade. Tumor biopsies of the patients were analyzed for cellular and molecular markers of antigen processing and presentation as well as the degree of T-cell infiltration., Results and Conclusion: Low expression of APM-related genes associated with low HLA class-I surface expression was observed in all MCC patients, progressing on PD-1/PD-L1 blockade. In one evaluable patient, of the two treated with the combination therapy of the HDACi, panobinostat and PD-1/PD-L1 blockade, reintroduction of HLA class-I-related genes, enhanced HLA class-I surface expression, and elevated CD8 + T-cell infiltration into the MCC tumor tissue were observed; however, these changes did not translate into a clinical benefit. Our findings suggest that HDACi may be useful to overcome HLA class-I downregulation as a resistance mechanism against anti-PD-1/PD-L1 antibodies in MCC patients. Prospective clinical trials are needed to evaluate this notion.

The majority of Merkel cell carcinoma, a highly aggressive neuroendocrine cancer of the skin, is associated with Merkel cell polyomavirus infection. Polyomavirus binding, internalization, and infection are mediated by glycosphingolipids. Besides receptor function, bioactive sphingolipids are increasingly recognized as potent regulators of several hallmarks of cancer. Merkel cell polyomavirus + and Merkel cell polyomavirus - cells express serine palmitoyl transferase subunits and sphingosine kinase (SK) 1/2 mRNA. Induced expression of Merkel cell polyomavirus-large tumor antigen in human lung fibroblasts resulted in upregulation of SPTLC1-3 and SK 1/2 expression. Therefore, we exploited pharmacological inhibition of sphingolipid metabolism as an option to interfere with proliferation of Merkel cell polyomavirus + Merkel cell carcinoma cell lines. We used myriocin (a serine palmitoyl transferase antagonist) and two SK inhibitors (SKI-II and ABC294640). In MKL-1 and WaGa cells myriocin decreased cellular ceramide, sphingomyelin, and sphingosine-1-phosphate content. SKI-II increased ceramide species but decreased sphingomyelin and sphingosine-1-phosphate concentrations. Aberrant sphingolipid homeostasis was associated with reduced cell viability, increased necrosis, procaspase-3 and PARP processing, caspase-3 activity, and decreased AKT S473 phosphorylation. Myriocin and SKI-II decreased tumor size and Ki-67 staining of xenografted MKL-1 and WaGa tumors on the chorioallantoic membrane. Our data suggest that pharmacological inhibition of sphingolipid synthesis could represent a potential therapeutic approach in Merkel cell carcinoma., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)