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Thevenin KR, Tieche IS, Di Benedetto CE, Schrager M, Dye KN. The small tumor antigen of Merkel cell polyomavirus accomplishes cellular transformation by uniquely localizing to the nucleus despite the absence of a known nuclear localization signal. Virol J 2024; 21:125. [PMID: 38831469 PMCID: PMC11149282 DOI: 10.1186/s12985-024-02395-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 05/22/2024] [Indexed: 06/05/2024] Open
Abstract
BACKGROUND Merkel Cell Carcinoma (MCC) is an aggressive skin cancer that is three times deadlier than melanoma. In 2008, it was found that 80% of MCC cases are caused by the genomic integration of a novel polyomavirus, Merkel Cell Polyomavirus (MCPyV), and the expression of its small and truncated large tumor antigens (ST and LT-t, respectively). MCPyV belongs to a family of human polyomaviruses; however, it is the only one with a clear association to cancer. METHODS To investigate the role and mechanisms of various polyomavirus tumor antigens in cellular transformation, Rat-2 and 293A cells were transduced with pLENTI MCPyV LT-t, MCPyV ST, TSPyV ST, HPyV7 ST, or empty pLENTI and assessed through multiple transformation assays, and subcellular fractionations. One-way ANOVA tests were used to assess statistical significance. RESULTS Soft agar, proliferation, doubling time, glucose uptake, and serum dependence assays confirmed ST to be the dominant transforming protein of MCPyV. Furthermore, it was found that MCPyV ST is uniquely transforming, as the ST antigens of other non-oncogenic human polyomaviruses such as Trichodysplasia Spinulosa-Associated Polyomavirus (TSPyV) and Human Polyomavirus 7 (HPyV7) were not transforming when similarly assessed. Identification of structural dissimilarities between transforming and non-transforming tumor antigens revealed that the uniquely transforming domain(s) of MCPyV ST are likely located within the structurally dissimilar loops of the MCPyV ST unique region. Of all known MCPyV ST cellular interactors, 62% are exclusively or transiently nuclear, suggesting that MCPyV ST localizes to the nucleus despite the absence of a canonical nuclear localization signal. Indeed, subcellular fractionations confirmed that MCPyV ST could achieve nuclear localization through a currently unknown, regulated mechanism independent of its small size, as HPyV7 and TSPyV ST proteins were incapable of nuclear translocation. Although nuclear localization was found to be important for several transforming properties of MCPyV ST, some properties were also performed by a cytoplasmic sequestered MCPyV ST, suggesting that MCPyV ST may perform different transforming functions in individual subcellular compartments. CONCLUSIONS Together, these data further elucidate the unique differences between MCPyV ST and other polyomavirus ST proteins necessary to understand MCPyV as the only known human oncogenic polyomavirus.
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Affiliation(s)
- Kaira R Thevenin
- Department of Health Sciences, Stetson University, 421 N Woodland Blvd, DeLand, FL, 32723, USA
| | - Isabella S Tieche
- Department of Health Sciences, Stetson University, 421 N Woodland Blvd, DeLand, FL, 32723, USA
| | - Cody E Di Benedetto
- Department of Health Sciences, Stetson University, 421 N Woodland Blvd, DeLand, FL, 32723, USA
| | - Matt Schrager
- Department of Health Sciences, Stetson University, 421 N Woodland Blvd, DeLand, FL, 32723, USA
| | - Kristine N Dye
- Department of Health Sciences, Stetson University, 421 N Woodland Blvd, DeLand, FL, 32723, USA.
- Department of Biology, Stetson University, DeLand, FL, 32723, USA.
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Gambichler T, Schrama D, Käpynen R, Weyer-Fahlbusch SS, Becker JC, Susok L, Kreppel F, Abu Rached N. Current Progress in Vaccines against Merkel Cell Carcinoma: A Narrative Review and Update. Vaccines (Basel) 2024; 12:533. [PMID: 38793784 PMCID: PMC11125734 DOI: 10.3390/vaccines12050533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/09/2024] [Accepted: 05/11/2024] [Indexed: 05/26/2024] Open
Abstract
Merkel cell carcinoma is a rare, aggressive skin cancer that mainly occurs in elderly and immunocompromised patients. Due to the success of immune checkpoint inhibition in MCC, the importance of immunotherapy and vaccines in MCC has increased in recent years. In this article, we aim to present the current progress and perspectives in the development of vaccines for this disease. Here, we summarize and discuss the current literature and ongoing clinical trials investigating vaccines against MCC. We identified 10 articles through a PubMed search investigating a vaccine against MCC. From the international clinical trial database Clinical.Trials.gov, we identified nine studies on vaccines for the management of MCC, of which seven are actively recruiting. Most of the identified studies investigating a vaccine against MCC are preclinical or phase 1/2 trials. The vaccine principles mainly included DNA- and (synthetic) peptide-based vaccines, but RNA-based vaccines, oncolytic viruses, and the combination of vaccines and immunotherapy are also under investigation for the treatment of MCC. Although the management of MCC is changing, when compared to times before the approval of immune checkpoint inhibitors, it will still take some time before the first MCC vaccine is ready for approval.
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Affiliation(s)
- Thilo Gambichler
- Department of Dermatology, Ruhr-University Bochum, 44791 Bochum, Germany; (R.K.); (N.A.R.)
- Department of Dermatology, Dortmund Hospital gGmbH and Faculty of Health, Witten-Herdecke University, 44122 Dortmund, Germany; (S.S.W.-F.); (L.S.)
- Department of Dermatology and Phlebology, Christian Hospital Unna, 59423 Unna, Germany
| | - David Schrama
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, 97080 Würzburg, Germany;
| | - Riina Käpynen
- Department of Dermatology, Ruhr-University Bochum, 44791 Bochum, Germany; (R.K.); (N.A.R.)
| | - Sera S. Weyer-Fahlbusch
- Department of Dermatology, Dortmund Hospital gGmbH and Faculty of Health, Witten-Herdecke University, 44122 Dortmund, Germany; (S.S.W.-F.); (L.S.)
| | - Jürgen C. Becker
- Translational Skin Cancer Research, DKTK Partner Site Essen/Düsseldorf, West German Cancer Center, Department of Dermatology, University Duisburg-Essen, 45122 Essen, Germany;
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Laura Susok
- Department of Dermatology, Dortmund Hospital gGmbH and Faculty of Health, Witten-Herdecke University, 44122 Dortmund, Germany; (S.S.W.-F.); (L.S.)
| | - Florian Kreppel
- Chair of Biochemistry and Molecular Medicine, Center for Biomedical Education and Research (ZBAF), Witten/Herdecke University, 58453 Witten, Germany;
| | - Nessr Abu Rached
- Department of Dermatology, Ruhr-University Bochum, 44791 Bochum, Germany; (R.K.); (N.A.R.)
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Thevenin KR, Tieche IS, Di Benedetto CE, Schrager M, Dye KN. The Small Tumor Antigen of Merkel Cell Polyomavirus Accomplishes Cellular Transformation by Uniquely Localizing to the Nucleus Despite the Absence of a Known Nuclear Localization Signal. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.28.569067. [PMID: 38293082 PMCID: PMC10827104 DOI: 10.1101/2023.11.28.569067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Background Merkel Cell Carcinoma (MCC) is an aggressive skin cancer that is three times deadlier than melanoma. In 2008, it was found that 80% of MCC cases are caused by the genomic integration of a novel polyomavirus, Merkel Cell Polyomavirus (MCPyV), and the expression of its small and truncated large tumor antigens (ST and LT-t, respectively). MCPyV belongs to a family of human polyomaviruses; however, it is the only one with a clear association to cancer. Methods To investigate the role and mechanisms of various polyomavirus tumor antigens in cellular transformation, Rat-2, 293A, and human foreskin fibroblasts were transduced with pLENTI MCPyV LT-t, MCPyV ST, TSPyV ST, HPyV7 ST, or empty pLENTI and assessed through multiple transformation assays, and subcellular fractionations. One-way ANOVA tests were used to assess statistical significance. Results Soft agar, proliferation, doubling time, glucose uptake, and serum dependence assays confirmed ST to be the dominant transforming protein of MCPyV. Furthermore, it was found that MCPyV ST is uniquely transforming, as the ST antigens of other non-oncogenic human polyomaviruses such as Trichodysplasia Spinulosa Polyomavirus (TSPyV) and Human Polyomavirus 7 (HPyV7) were not transforming when similarly assessed. Identification of structural dissimilarities between transforming and non-transforming tumor antigens revealed that the uniquely transforming domain(s) of MCPyV ST are likely located within the structurally dissimilar loops of the MCPyV ST unique region. Of all known MCPyV ST cellular interactors, 62% are exclusively or transiently nuclear, suggesting that MCPyV ST localizes to the nucleus despite the absence of a canonical nuclear localization signal. Indeed, subcellular fractionations confirmed that MCPyV ST could achieve nuclear localization through a currently unknown, regulated mechanism independent of its small size, as HPyV7 and TSPyV ST proteins were incapable of nuclear translocation. Although nuclear localization was found to be important for several transforming properties of MCPyV ST, some properties were also performed by a cytoplasmic sequestered MCPyV ST, suggesting that MCPyV ST may perform different transforming functions in individual subcellular compartments. Conclusions Together, these data further elucidate the unique differences between MCPyV ST and other polyomavirus ST proteins necessary to understand MCPyV as the only known human oncogenic polyomavirus.
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Moens U, Passerini S, Falquet M, Sveinbjørnsson B, Pietropaolo V. Phosphorylation of Human Polyomavirus Large and Small T Antigens: An Ignored Research Field. Viruses 2023; 15:2235. [PMID: 38005912 PMCID: PMC10674619 DOI: 10.3390/v15112235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 11/02/2023] [Accepted: 11/07/2023] [Indexed: 11/26/2023] Open
Abstract
Protein phosphorylation and dephosphorylation are the most common post-translational modifications mediated by protein kinases and protein phosphatases, respectively. These reversible processes can modulate the function of the target protein, such as its activity, subcellular localization, stability, and interaction with other proteins. Phosphorylation of viral proteins plays an important role in the life cycle of a virus. In this review, we highlight biological implications of the phosphorylation of the monkey polyomavirus SV40 large T and small t antigens, summarize our current knowledge of the phosphorylation of these proteins of human polyomaviruses, and conclude with gaps in the knowledge and a proposal for future research directions.
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Affiliation(s)
- Ugo Moens
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Sara Passerini
- Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, 00185 Rome, Italy;
| | - Mar Falquet
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Baldur Sveinbjørnsson
- Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway; (M.F.); (B.S.)
| | - Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, 00185 Rome, Italy;
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Celikdemir B, Houben R, Kervarrec T, Samimi M, Schrama D. Current and preclinical treatment options for Merkel cell carcinoma. Expert Opin Biol Ther 2023; 23:1015-1034. [PMID: 37691397 DOI: 10.1080/14712598.2023.2257603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 09/04/2023] [Accepted: 09/07/2023] [Indexed: 09/12/2023]
Abstract
INTRODUCTION Merkel cell carcinoma (MCC) is a rare, highly aggressive form of skin cancer with neuroendocrine features. The origin of this cancer is still unclear, but research in the last 15 years has demonstrated that MCC arises via two distinct etiologic pathways, i.e. virus and UV-induced. Considering the high mortality rate and the limited therapeutic options available, this review aims to highlight the significance of MCC research and the need for advancement in MCC treatment. AREAS COVERED With the advent of the immune checkpoint inhibitor therapies, we now have treatment options providing a survival benefit for patients with advanced MCC. However, the issue of primary and acquired resistance to these therapies remains a significant concern. Therefore, ongoing efforts seeking additional therapeutic targets and approaches for MCC therapy are a necessity. Through a comprehensive literature search, we provide an overview on recent preclinical and clinical studies with respect to MCC therapy. EXPERT OPINION Currently, the only evidence-based therapy for MCC is immune checkpoint blockade with anti-PD-1/PD-L1 for advanced patients. Neoadjuvant, adjuvant and combined immune checkpoint blockade are promising treatment options.
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Affiliation(s)
- Büke Celikdemir
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Roland Houben
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Thibault Kervarrec
- Department of Pathology, Centre Hospitalier Universitaire De Tours, Tours, France
| | - Mahtab Samimi
- Department of Dermatology, University Hospital of Tours, Tours, France
| | - David Schrama
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
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Merkel Cell Polyomavirus: Infection, Genome, Transcripts and Its Role in Development of Merkel Cell Carcinoma. Cancers (Basel) 2023; 15:cancers15020444. [PMID: 36672392 PMCID: PMC9857234 DOI: 10.3390/cancers15020444] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 01/13/2023] Open
Abstract
The best characterized polyomavirus family member, i.e., simian virus 40 (SV40), can cause different tumors in hamsters and can transform murine and human cells in vitro. Hence, the SV40 contamination of millions of polio vaccine doses administered from 1955-1963 raised fears that this may cause increased tumor incidence in the vaccinated population. This is, however, not the case. Indeed, up to now, the only polyomavirus family member known to be the most important cause of a specific human tumor entity is Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma (MCC). MCC is a highly deadly form of skin cancer for which the cellular origin is still uncertain, and which appears as two clinically very similar but molecularly highly different variants. While approximately 80% of cases are found to be associated with MCPyV the remaining MCCs carry a high mutational load. Here, we present an overview of the multitude of molecular functions described for the MCPyV encoded oncoproteins and non-coding RNAs, present the available MCC mouse models and discuss the increasing evidence that both, virus-negative and -positive MCC constitute epithelial tumors.
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Falquet M, Prezioso C, Ludvigsen M, Bruun JA, Passerini S, Sveinbjørnsson B, Pietropaolo V, Moens U. Regulation of Transcriptional Activity of Merkel Cell Polyomavirus Large T-Antigen by PKA-Mediated Phosphorylation. Int J Mol Sci 2023; 24:ijms24010895. [PMID: 36614338 PMCID: PMC9820997 DOI: 10.3390/ijms24010895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/13/2022] [Accepted: 12/23/2022] [Indexed: 01/06/2023] Open
Abstract
Merkel cell polyomavirus (MCPyV) is the major cause of Merkel cell carcinoma (MCC), an aggressive skin cancer. MCPyV large T-antigen (LTag) and small T-antigen (sTag) are the main oncoproteins involved in MCPyV-induced MCC. A hallmark of MCPyV-positive MCC cells is the expression of a C-terminal truncated LTag. Protein kinase A (PKA) plays a fundamental role in a variety of biological processes, including transcription by phosphorylating and thereby regulating the activity of transcription factors. As MCPyV LTag has been shown to be phosphorylated and acts as a transcription factor for the viral early and late promoter, we investigated whether LTag can be phosphorylayted by PKA, and whether this affects the transcript activity of LTag. Using a phosphorylation prediction algorithm, serine 191, 203, and 265 were identified as putative phosphorylation sites for PKA. Mass spectrometry of in vitro PKA-phosphorylated peptides confirmed phosphorylation of S203 and S265, but not S191. Full-length LTag inhibited early and late promoter activity of MCPyV, whereas the truncated MKL2 LTag variant stimulated both promoters. Single non-phosphorylable, as well as phosphomimicking mutations did not alter the inhibitory effect of full-length LTag. However, the non-phosphorylable mutations abrogated transactivation of the MCPyV promoters by MKL2 LTag, whereas phosphomimicking substitutions restored the ability of MKL2 LTag to activate the promoters. Triple LTag and MKL2 LTag mutants had the same effect as the single mutants. Activation of the PKA signaling pathway did not enhance MCPyV promoter activity, nor did it affect LTag expression levels in MCPyV-positive Merkel cell carcinoma (MCC) cells. Our results show that phosphorylation of truncated LTag stimulates viral promoter activity, which may contribute to higher levels of the viral oncoproteins LTag and sTag. Interfering with PKA-induced LTag phosphorylation/activity may be a therapeutic strategy to treat MCPyV-positive MCC patients.
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Affiliation(s)
- Mar Falquet
- Molecular Inflammation Research Group, Department of Medical Biology, University of Tromsø-The Arctic University of Norway, 9037 Tromsø, Norway
| | - Carla Prezioso
- Microbiology of Chronic Neuro-Degenerative Pathologies, IRCSS San Raffaele, 00163 Rome, Italy
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, 00185 Rome, Italy
| | - Maria Ludvigsen
- Molecular Inflammation Research Group, Department of Medical Biology, University of Tromsø-The Arctic University of Norway, 9037 Tromsø, Norway
| | - Jack-Ansgar Bruun
- Department of Medical Biology, Proteomics Platform, University of Tromsø-The Arctic University of Norway, 9037 Tromsø, Norway
| | - Sara Passerini
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, 00185 Rome, Italy
| | - Baldur Sveinbjørnsson
- Molecular Inflammation Research Group, Department of Medical Biology, University of Tromsø-The Arctic University of Norway, 9037 Tromsø, Norway
- Childhood Cancer Research Unit, Department of Women’s and Children’s Health, Karolinska Institute, 17177 Stockholm, Sweden
| | - Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, 00185 Rome, Italy
- Correspondence: (V.P.); (U.M.)
| | - Ugo Moens
- Microbiology of Chronic Neuro-Degenerative Pathologies, IRCSS San Raffaele, 00163 Rome, Italy
- Correspondence: (V.P.); (U.M.)
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Spurgeon ME, Cheng J, Ward-Shaw E, Dick FA, DeCaprio JA, Lambert PF. Merkel cell polyomavirus large T antigen binding to pRb promotes skin hyperplasia and tumor development. PLoS Pathog 2022; 18:e1010551. [PMID: 35560034 PMCID: PMC9132321 DOI: 10.1371/journal.ppat.1010551] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 05/25/2022] [Accepted: 04/26/2022] [Indexed: 12/14/2022] Open
Abstract
Clear evidence supports a causal link between Merkel cell polyomavirus (MCPyV) and the highly aggressive human skin cancer called Merkel cell carcinoma (MCC). Integration of viral DNA into the human genome facilitates continued expression of the MCPyV small tumor (ST) and large tumor (LT) antigens in virus-positive MCCs. In MCC tumors, MCPyV LT is truncated in a manner that renders the virus unable to replicate yet preserves the LXCXE motif that facilitates its binding to and inactivation of the retinoblastoma tumor suppressor protein (pRb). We previously developed a MCPyV transgenic mouse model in which MCC tumor-derived ST and truncated LT expression were targeted to the stratified epithelium of the skin, causing epithelial hyperplasia, increased proliferation, and spontaneous tumorigenesis. We sought to determine if any of these phenotypes required the association between the truncated MCPyV LT and pRb. Mice were generated in which K14-driven MCPyV ST/LT were expressed in the context of a homozygous RbΔLXCXE knock-in allele that attenuates LT-pRb interactions through LT's LXCXE motif. We found that many of the phenotypes including tumorigenesis that develop in the K14-driven MCPyV transgenic mice were dependent upon LT's LXCXE-dependent interaction with pRb. These findings highlight the importance of the MCPyV LT-pRb interaction in an in vivo model for MCPyV-induced tumorigenesis.
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Affiliation(s)
- Megan E. Spurgeon
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
- * E-mail:
| | - Jingwei Cheng
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, New Hampshire, United States of America
| | - Ella Ward-Shaw
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
| | - Frederick A. Dick
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario, Canada
- Children’s Health Research Institute, London, Ontario, Canada
- London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada
| | - James A. DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Paul F. Lambert
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America
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Krump NA, You J. From Merkel Cell Polyomavirus Infection to Merkel Cell Carcinoma Oncogenesis. Front Microbiol 2021; 12:739695. [PMID: 34566942 PMCID: PMC8457551 DOI: 10.3389/fmicb.2021.739695] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Accepted: 08/09/2021] [Indexed: 11/13/2022] Open
Abstract
Merkel cell polyomavirus (MCPyV) infection causes near-ubiquitous, asymptomatic infection in the skin, but occasionally leads to an aggressive skin cancer called Merkel cell carcinoma (MCC). Epidemiological evidence suggests that poorly controlled MCPyV infection may be a precursor to MCPyV-associated MCC. Clearer understanding of host responses that normally control MCPyV infection could inform prophylactic measures in at-risk groups. Similarly, the presence of MCPyV in most MCCs could imbue them with vulnerabilities that-if better characterized-could yield targeted intervention solutions for metastatic MCC cases. In this review, we discuss recent developments in elucidating the interplay between host cells and MCPyV within the context of viral infection and MCC oncogenesis. We also propose a model in which insufficient restriction of MCPyV infection in aging and chronically UV-damaged skin causes unbridled viral replication that licenses MCC tumorigenesis.
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Affiliation(s)
| | - Jianxin You
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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10
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Spurgeon ME, Liem A, Buehler D, Cheng J, DeCaprio JA, Lambert PF. The Merkel Cell Polyomavirus T Antigens Function as Tumor Promoters in Murine Skin. Cancers (Basel) 2021; 13:cancers13020222. [PMID: 33435392 PMCID: PMC7827793 DOI: 10.3390/cancers13020222] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/05/2021] [Accepted: 01/08/2021] [Indexed: 02/06/2023] Open
Abstract
Simple Summary Merkel cell polyomavirus, a recently discovered human virus, is linked to the development of a rare form of skin cancer called Merkel cell carcinoma. The virus does not replicate in cancer cells, yet there is continued expression of viral proteins known as T antigens. The T antigens are believed to contribute to Merkel cell carcinoma development, yet how they do so remains an active area of research. In this study, we used transgenic mice expressing the viral T antigens in their skin to determine at which stage of skin cancer development these viral proteins function. We discovered that the Merkel cell polyomavirus T antigens function as tumor promoters, rather than tumor initiators, in the skin. These findings suggest that other tumor-initiating events may cooperate with the tumor-promoting activities of the viral T antigens, thus providing important insight into how Merkel cell polyomavirus can cause cancer in human skin. Abstract Merkel cell polyomavirus (MCPyV) causes the majority of human Merkel cell carcinomas (MCC), a rare but highly aggressive form of skin cancer. We recently reported that constitutive expression of MCC tumor-derived MCPyV tumor (T) antigens in the skin of transgenic mice leads to hyperplasia, increased proliferation, and spontaneous epithelial tumor development. We sought to evaluate how the MCPyV T antigens contribute to tumor formation in vivo using a classical, multi-stage model for squamous cell carcinoma development. In this model, two chemical carcinogens, DMBA and TPA, contribute to two distinct phases of carcinogenesis—initiation and promotion, respectively—that are required for tumors to develop. By treating the MCPyV transgenic mice with each chemical carcinogen, we determined how the viral oncogenes contributed to carcinogenesis. We observed that the MCPyV T antigens synergized with the tumor initiator DMBA, but not with the tumor promoter TPA, cause tumors. Therefore, the MCPyV tumor antigens function primarily as tumor promoters, similar to that seen with human papillomavirus (HPV) oncoproteins. These studies provide insight into the role of MCPyV T antigen expression in tumor formation in vivo and contribute to our understanding of how MCPyV may function as a human DNA tumor virus.
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Affiliation(s)
- Megan E. Spurgeon
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA;
- Correspondence: (M.E.S.); (P.F.L.)
| | - Amy Liem
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA;
| | - Darya Buehler
- Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA;
| | - Jingwei Cheng
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA;
| | - James A. DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA;
- Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02215, USA
| | - Paul F. Lambert
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA;
- Correspondence: (M.E.S.); (P.F.L.)
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Abstract
Merkel cell polyomavirus (MCPyV) is the most recently discovered human oncogenic virus. MCPyV asymptomatically infects most of the human population. In the elderly and immunocompromised, however, it can cause a highly lethal form of human skin cancer called Merkel cell carcinoma (MCC). Distinct from the productive MCPyV infection that replicates the viral genome as episomes, MCC tumors contain replication-incompetent, integrated viral genomes. Mutant MCPyV tumor antigen genes expressed from the integrated viral genomes are essential for driving the oncogenic development of MCPyV-associated MCC. In this chapter, we summarize recent discoveries on MCPyV virology, mechanisms of MCPyV-mediated oncogenesis, and the current therapeutic strategies for MCPyV-associated MCCs.
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Affiliation(s)
- Wei Liu
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Jianxin You
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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12
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DeCaprio JA. Molecular Pathogenesis of Merkel Cell Carcinoma. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2020; 16:69-91. [PMID: 33228463 DOI: 10.1146/annurev-pathmechdis-012419-032817] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin with two distinct etiologies. Clonal integration of Merkel cell polyomavirus DNA into the tumor genome with persistent expression of viral T antigens causes at least 60% of all MCC. UV damage leading to highly mutated genomes causes a nonviral form of MCC. Despite these distinct etiologies, both forms of MCC are similar in presentation, prognosis, and response to therapy. At least three oncogenic transcriptional programs feature prominently in both forms of MCC driven by the virus or by mutation. Both forms of MCC have a high proliferative growth rate with increased levels of cell cycle-dependent genes due to inactivation of the tumor suppressors RB and p53, a strong MYC signature due to MYCL activation by the virus or gene amplification, and an attenuated neuroendocrine differentiation program driven by the ATOH1 transcription factor.
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Affiliation(s)
- James A DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA; .,Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.,Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA
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13
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Merkel Cell Polyomavirus Large T Antigen Unique Domain Regulates Its Own Protein Stability and Cell Growth. Viruses 2020; 12:v12091043. [PMID: 32962090 PMCID: PMC7551350 DOI: 10.3390/v12091043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 02/07/2023] Open
Abstract
Merkel cell polyomavirus (MCV) is the only known human oncogenic virus in the polyomaviridae family and the etiological agent of most Merkel cell carcinomas (MCC). MCC is an aggressive and highly metastatic skin cancer with a propensity for recurrence and poor prognosis. Large tumor antigen (LT), is an essential oncoprotein for MCV transcription, viral replication, and cancer cell proliferation. MCV LT is a short-lived protein that encodes a unique domain: MCV LT unique regions (MURs). These domains consist of phosphorylation sites that interact with multiple E3 ligases, thus limiting LT expression and consequently, viral replication. In this study, we show that MURs are necessary for regulating LT stability via multiple E3 ligase interactions, resulting in cell growth arrest. While expression of wild-type MCV LT induced a decrease in cellular proliferation, deletion of the MUR domains resulted in increased LT stability and cell proliferation. Conversely, addition of MURs to SV40 LT propagated E3 ligase interactions, which in turn, reduced SV40 LT stability and decreased cell growth activity. Our results demonstrate that compared to other human polyomaviruses (HPyVs), MCV LT has evolved to acquire the MUR domains that are essential for MCV LT autoregulation, potentially leading to viral latency and MCC.
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14
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Pietropaolo V, Prezioso C, Moens U. Merkel Cell Polyomavirus and Merkel Cell Carcinoma. Cancers (Basel) 2020; 12:E1774. [PMID: 32635198 PMCID: PMC7407210 DOI: 10.3390/cancers12071774] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 06/26/2020] [Accepted: 06/28/2020] [Indexed: 12/12/2022] Open
Abstract
Viruses are the cause of approximately 15% of all human cancers. Both RNA and DNA human tumor viruses have been identified, with Merkel cell polyomavirus being the most recent one to be linked to cancer. This virus is associated with about 80% of Merkel cell carcinomas, a rare, but aggressive cutaneous malignancy. Despite its name, the cells of origin of this tumor may not be Merkel cells. This review provides an update on the structure and life cycle, cell tropism and epidemiology of the virus and its oncogenic properties. Putative strategies to prevent viral infection or treat virus-positive Merkel cell carcinoma patients are discussed.
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Affiliation(s)
- Valeria Pietropaolo
- Department of Public Health and Infectious Diseases, “Sapienza” University, 00185 Rome, Italy; (V.P.); (C.P.)
| | - Carla Prezioso
- Department of Public Health and Infectious Diseases, “Sapienza” University, 00185 Rome, Italy; (V.P.); (C.P.)
- IRCSS San Raffaele Pisana, Microbiology of Chronic Neuro-Degenerative Pathologies, 00166 Rome, Italy
| | - Ugo Moens
- Molecular Inflammation Research Group, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø—The Arctic University of Norway, 9037 Tromsø, Norway
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15
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Longino NV, Yang J, Iyer JG, Ibrani D, Chow IT, Laing KJ, Campbell VL, Paulson KG, Kulikauskas RM, Church CD, James EA, Nghiem P, Kwok WW, Koelle DM. Human CD4 + T Cells Specific for Merkel Cell Polyomavirus Localize to Merkel Cell Carcinomas and Target a Required Oncogenic Domain. Cancer Immunol Res 2019; 7:1727-1739. [PMID: 31405946 DOI: 10.1158/2326-6066.cir-19-0103] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 05/07/2019] [Accepted: 08/06/2019] [Indexed: 12/30/2022]
Abstract
Although CD4+ T cells likely play key roles in antitumor immune responses, most immuno-oncology studies have been limited to CD8+ T-cell responses due to multiple technical barriers and a lack of shared antigens across patients. Merkel cell carcinoma (MCC) is an aggressive skin cancer caused by Merkel cell polyomavirus (MCPyV) oncoproteins in 80% of cases. Because MCPyV oncoproteins are shared across most patients with MCC, it is unusually feasible to identify, characterize, and potentially augment tumor-specific CD4+ T cells. Here, we report the identification of CD4+ T-cell responses against six MCPyV epitopes, one of which included a conserved, essential viral oncogenic domain that binds/disables the cellular retinoblastoma (Rb) tumor suppressor. We found that this epitope (WEDLT209-228) could be presented by three population-prevalent HLA class II alleles, making it a relevant target in 64% of virus-positive MCC patients. Cellular staining with a WEDLT209-228-HLA-DRB1*0401 tetramer indicated that specific CD4+ T cells were detectable in 78% (14 of 18) of evaluable MCC patients, were 250-fold enriched within MCC tumors relative to peripheral blood, and had diverse T-cell receptor sequences. We also identified a modification of this domain that still allowed recognition by these CD4+ T cells but disabled binding to the Rb tumor suppressor, a key step in the detoxification of a possible therapeutic vaccine. The use of these new tools for deeper study of MCPyV-specific CD4+ T cells may provide broader insight into cancer-specific CD4+ T-cell responses.
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Affiliation(s)
- Natalie V Longino
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington.,Department of Pathology, University of Washington, Seattle, Washington
| | - Junbao Yang
- Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington
| | - Jayasri G Iyer
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington
| | - Dafina Ibrani
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington
| | - I-Ting Chow
- Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington
| | - Kerry J Laing
- Department of Medicine, Division of Allergy and Infectious Disease, University of Washington, Seattle, Washington
| | - Victoria L Campbell
- Department of Medicine, Division of Allergy and Infectious Disease, University of Washington, Seattle, Washington
| | - Kelly G Paulson
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington.,Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.,Department of Medicine, Division of Medical Oncology, University of Washington, Seattle, Washington
| | - Rima M Kulikauskas
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington
| | - Candice D Church
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington
| | - Eddie A James
- Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington
| | - Paul Nghiem
- Department of Medicine, Division of Dermatology, University of Washington, Seattle, Washington. .,Department of Pathology, University of Washington, Seattle, Washington
| | - William W Kwok
- Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington
| | - David M Koelle
- Translational Research Program, Benaroya Research Institute at Virginia Mason, Seattle, Washington.,Department of Medicine, Division of Allergy and Infectious Disease, University of Washington, Seattle, Washington.,Department of Laboratory Medicine, University of Washington, Seattle, Washington.,Department of Global Health, University of Washington, Seattle, Washington.,Vaccine and Infectious Diseases Division, Fred Hutchinson Cancer Research Center, Seattle, Washington
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16
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Merkel cell polyomavirus Tumor antigens expressed in Merkel cell carcinoma function independently of the ubiquitin ligases Fbw7 and β-TrCP. PLoS Pathog 2019; 15:e1007543. [PMID: 30689667 PMCID: PMC6366716 DOI: 10.1371/journal.ppat.1007543] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 02/07/2019] [Accepted: 12/19/2018] [Indexed: 02/01/2023] Open
Abstract
Merkel cell polyomavirus (MCPyV) accounts for 80% of all Merkel cell carcinoma (MCC) cases through expression of two viral oncoproteins: the truncated large T antigen (LT-t) and small T antigen (ST). MCPyV ST is thought to be the main driver of cellular transformation and has also been shown to increase LT protein levels through the activity of its Large-T Stabilization Domain (LSD). The ST LSD was reported to bind and sequester several ubiquitin ligases, including Fbw7 and β-TrCP, and thereby stabilize LT-t and several other Fbw7 targets including c-Myc and cyclin E. Therefore, the ST LSD is thought to contribute to transformation by promoting the accumulation of these oncoproteins. Targets of Fbw7 and β-TrCP contain well-defined, conserved, phospho-degrons. However, as neither MCPyV LT, LT-t nor ST contain the canonical Fbw7 phospho-degron, we sought to further investigate the proposed model of ST stabilization of LT-t and transformation. In this study, we provide several lines of evidence that fail to support a specific interaction between MCPyV T antigens and Fbw7 or β-TrCP by co-immunoprecipitation or functional consequence. Although MCPyV ST does indeed increase LT protein levels through its Large-T Stabilization domain (LSD), this is accomplished independently of Fbw7. Therefore, our study indicates a need for further investigation into the role and mechanism(s) of MCPyV T antigens in viral replication, latency, transformation, and tumorigenesis. Merkel cell carcinoma (MCC) is a very aggressive and deadly neuroendocrine skin cancer. Merkel cell polyomavirus (MCPyV) contributes to the development and maintenance of 80% of MCCs through the expression of its truncated large tumor antigen (LT-t) and small tumor antigen (ST). MCPyV ST is thought to be primarily responsible for transformation and tumorigenesis through many mechanisms including stabilization of MCPyV LT-t and other cellular proteins involved in proliferation such as c-Myc. As c-Myc is a known target substrate, and MCPyV LT-t is a proposed target substrate, of the ubiquitin ligase Fbw7, it is currently thought that ST stabilizes these proteins and transforms cells through binding and perturbing the function of Fbw7. However, neither MCPyV LT-t nor ST contain a canonical Fbw7 degron sequence necessary for this interaction. MCPyV LT-t, found in MCCs, does not bind to, nor is targeted by, Fbw7. However, an ill-defined, unidirectional interaction between MCPyV LT, ST, and Fbw7 was observed, but had no functional consequence. Therefore, this study calls for further investigation into the mechanism(s) by which MCPyV ST leads to the development and maintenance of MCC.
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17
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Colunga A, Pulliam T, Nghiem P. Merkel Cell Carcinoma in the Age of Immunotherapy: Facts and Hopes. Clin Cancer Res 2018; 24:2035-2043. [PMID: 29217527 PMCID: PMC5932211 DOI: 10.1158/1078-0432.ccr-17-0439] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 10/12/2017] [Accepted: 12/01/2017] [Indexed: 11/16/2022]
Abstract
Merkel cell carcinoma (MCC) is a rare (∼2,000 U.S. cases/year) but aggressive neuroendocrine tumor of the skin. For advanced MCC, cytotoxic chemotherapy only infrequently (<10% of cases) offers durable clinical responses (>1 year), suggesting a great need for improved therapeutic options. In 2008, the Merkel cell polyomavirus (MCPyV) was discovered and is clonally integrated in approximately 80% of MCC tumors. The remaining 20% of MCC tumors have large numbers of UV-associated mutations. Importantly, both the UV-induced neoantigens in virus-negative tumors and the MCPyV T antigen oncogenes that are required for virus-positive tumor growth are immunogenic. Indeed, antigen-specific T cells detected in patients are frequently dysfunctional/"exhausted," and the inhibitory ligand, PD-L1, is often present in MCC tumors. These findings led to recent clinical trials involving PD-1 pathway blockade in advanced MCC. The combined data from these trials involving three PD-1 pathway blocking agents-avelumab, pembrolizumab, and nivolumab-indicated a high frequency of durable responses in treated patients. Of note, prior treatment with chemotherapy was associated with decreased response rates to PD-1 checkpoint blockade. Over the past year, these striking data led to major changes in advanced MCC therapy, including the first-ever FDA drug approval for this disease. Despite these successes, approximately 50% of patients with MCC do not persistently benefit from PD-1 pathway blockade, underscoring the need for novel strategies to broaden antitumor immune responses in these patients. Here, we highlight recent progress in MCC including the underlying mechanisms of immune evasion and emerging approaches to augment the efficacy of PD-1 pathway blockade. Clin Cancer Res; 24(9); 2035-43. ©2017 AACR.
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Affiliation(s)
- Aric Colunga
- Division of Dermatology, Department of Medicine, University of Washington, Seattle, Washington
| | - Thomas Pulliam
- Division of Dermatology, Department of Medicine, University of Washington, Seattle, Washington
| | - Paul Nghiem
- Division of Dermatology, Department of Medicine, University of Washington, Seattle, Washington.
- Seattle Cancer Care Alliance, Seattle, Washington
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington
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18
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Becker JC, Stang A, Hausen AZ, Fischer N, DeCaprio JA, Tothill RW, Lyngaa R, Hansen UK, Ritter C, Nghiem P, Bichakjian CK, Ugurel S, Schrama D. Epidemiology, biology and therapy of Merkel cell carcinoma: conclusions from the EU project IMMOMEC. Cancer Immunol Immunother 2018; 67:341-351. [PMID: 29188306 PMCID: PMC6015651 DOI: 10.1007/s00262-017-2099-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 11/24/2017] [Indexed: 01/23/2023]
Abstract
Merkel cell carcinoma (MCC) is a highly aggressive, often lethal neuroendocrine cancer. Its carcinogenesis may be either caused by the clonal integration of the Merkel cell polyomavirus into the host genome or by UV-induced mutations. Notably, virally-encoded oncoproteins and UV-induced mutations affect comparable signaling pathways such as RB restriction of cell cycle progression or p53 inactivation. Despite its low incidence, MCC recently received much attention based on its exquisite immunogenicity and the resulting major success of immune modulating therapies. Here, we summarize current knowledge on epidemiology, biology and therapy of MCC as conclusion of the project 'Immune Modulating strategies for treatment of Merkel Cell Carcinoma', which was funded over a 5-year period by the European Commission to investigate innovative immunotherapies for MCC.
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Affiliation(s)
- Jürgen C Becker
- Translational Skin Cancer Research (tscr), German Cancer Consortium (DKTK), University Hospital of Essen, Universitätsstrasse 1, S05 T05 B, 45141, Essen, Germany.
- German Cancer Research Center (DKFZ), Heidelberg, Germany.
- Department of Dermatology, University Hospital of Essen, Essen, Germany.
| | - Andreas Stang
- German Cancer Research Center (DKFZ), Heidelberg, Germany
- Center of Clinical Epidemiology; c/o Institute of Medical Informatics, Biometry and Epidemiology, University Hospital of Essen, Essen, Germany
| | - Axel Zur Hausen
- Department of Pathology, Academisch Ziekenhuis Maastricht, Maastricht, The Netherlands
| | - Nicole Fischer
- Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - James A DeCaprio
- Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | | | - Rikke Lyngaa
- Section for Immunology and Vaccinology, National Veterinary Institute, Technical University of Denmark, Copenhagen, Denmark
| | - Ulla Kring Hansen
- George F. Odland Endowed Chair in Dermatology, University of Washington, Seattle, WA, USA
| | - Cathrin Ritter
- Translational Skin Cancer Research (tscr), German Cancer Consortium (DKTK), University Hospital of Essen, Universitätsstrasse 1, S05 T05 B, 45141, Essen, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Paul Nghiem
- George F. Odland Endowed Chair in Dermatology, University of Washington, Seattle, WA, USA
| | | | - Selma Ugurel
- Department of Dermatology, University Hospital of Essen, Essen, Germany
| | - David Schrama
- Department of Dermatology, University Hospital Wuerzburg, Würzburg, Germany
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19
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Hesbacher S, Pfitzer L, Wiedorfer K, Angermeyer S, Borst A, Haferkamp S, Scholz CJ, Wobser M, Schrama D, Houben R. RB1 is the crucial target of the Merkel cell polyomavirus Large T antigen in Merkel cell carcinoma cells. Oncotarget 2018; 7:32956-68. [PMID: 27121059 PMCID: PMC5078066 DOI: 10.18632/oncotarget.8793] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 03/28/2016] [Indexed: 11/25/2022] Open
Abstract
The pocket protein (PP) family consists of the three members RB1, p107 and p130 all possessing tumor suppressive properties. Indeed, the PPs jointly control the G1/S transition mainly by inhibiting E2F transcription factors. Notably, several viral oncoproteins are capable of binding and inhibiting PPs. Merkel cell polyomavirus (MCPyV) is considered as etiological factor for Merkel cell carcinoma (MCC) with expression of the viral Large T antigen (LT) harboring an intact PP binding domain being required for proliferation of most MCC cells. Therefore, we analyzed the interaction of MCPyV-LT with the PPs. Co-IP experiments indicate that MCPyV-LT binds potently only to RB1. Moreover, MCPyV-LT knockdown-induced growth arrest in MCC cells can be rescued by knockdown of RB1, but not by p107 or p130 knockdown. Accordingly, cell cycle arrest and E2F target gene repression mediated by the single PPs can only in the case of RB1 be significantly reverted by MCPyV-LT expression. Moreover, data from an MCC patient indicate that loss of RB1 rendered the MCPyV-positive MCC cells LT independent. Thus, our results suggest that RB1 is the dominant tumor suppressor PP in MCC, and that inactivation of RB1 by MCPyV-LT is largely sufficient for its growth supporting function in established MCPyV-positive MCC cells.
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Affiliation(s)
- Sonja Hesbacher
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Lisa Pfitzer
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany.,Department of Pharmacy, Center for Drug Research, University of Munich (Ludwigs-Maximilians-Universität), Munich, Germany
| | - Katharina Wiedorfer
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Sabrina Angermeyer
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Andreas Borst
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | | | | | - Marion Wobser
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - David Schrama
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
| | - Roland Houben
- Department of Dermatology, Venereology and Allergology, University Hospital Würzburg, Würzburg, Germany
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20
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Palopoli N, González Foutel NS, Gibson TJ, Chemes LB. Short linear motif core and flanking regions modulate retinoblastoma protein binding affinity and specificity. Protein Eng Des Sel 2018; 31:69-77. [DOI: 10.1093/protein/gzx068] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Accepted: 01/10/2018] [Indexed: 12/11/2022] Open
Affiliation(s)
- Nicolás Palopoli
- Department of Science and Technology, Universidad Nacional de Quilmes, CONICET. Roque Sáenz Peña 352. CP (B1876BXD), Bernal, Buenos Aires, Argentina
- Structural Bioinformatics Unit, Fundación Instituto Leloir and IIBBA-CONICET. Av. Patricias Argentinas 435 CP 1405, Buenos Aires, Argentina
| | - Nicolás S González Foutel
- Protein Structure Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET. Av. Patricias Argentinas 435 CP 1405, Buenos Aires, Argentina
| | - Toby J Gibson
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117, Heidelberg, Germany
| | - Lucía B Chemes
- Protein Structure Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET. Av. Patricias Argentinas 435 CP 1405, Buenos Aires, Argentina
- Instituto de Investigaciones Biotecnológicas IIB-INTECH, Universidad Nacional de San Martín. Av. 25 de Mayo y Francia CP 1650, San Martín, Buenos Aires, Argentina
- Departamento de Fisiología y Biología Molecular y Celular (DFBMC), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA, Argentina
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21
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Vandeven N, Nghiem P. Rationale for immune-based therapies in Merkel polyomavirus-positive and -negative Merkel cell carcinomas. Immunotherapy 2017; 8:907-21. [PMID: 27381685 DOI: 10.2217/imt-2016-0009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Merkel cell carcinoma (MCC) is a rare but often deadly skin cancer that is typically caused by the Merkel cell polyomavirus (MCPyV). Polyomavirus T-antigen oncoproteins are persistently expressed in virus-positive MCCs (˜80% of cases), while remarkably high numbers of tumor-associated neoantigens are detected in virus-negative MCCs, suggesting that both MCC subsets may be immunogenic. Here we review mechanisms by which these immunogenic tumors evade multiple levels of host immunity. Additionally, we summarize the exciting potential of diverse immune-based approaches to treat MCC. In particular, agents blocking the PD-1 axis have yielded strikingly high response rates in MCC as compared with other solid tumors, highlighting the potential for immune-mediated treatment of this disease.
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Affiliation(s)
- Natalie Vandeven
- Department of Medicine (Pathology & Dermatology), University of Washington, USA
| | - Paul Nghiem
- Department of Medicine (Pathology & Dermatology), University of Washington, USA
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22
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Protein-mediated viral latency is a novel mechanism for Merkel cell polyomavirus persistence. Proc Natl Acad Sci U S A 2017; 114:E4040-E4047. [PMID: 28461484 DOI: 10.1073/pnas.1703879114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Viral latency, in which a virus genome does not replicate independently of the host cell genome and produces no infectious particles, is required for long-term virus persistence. There is no known latency mechanism for chronic small DNA virus infections. Merkel cell polyomavirus (MCV) causes an aggressive skin cancer after prolonged infection and requires an active large T (LT) phosphoprotein helicase to replicate. We show that evolutionarily conserved MCV LT phosphorylation sites are constitutively recognized by cellular Fbw7, βTrCP, and Skp2 Skp-F-box-cullin (SCF) E3 ubiquitin ligases, which degrade and suppress steady-state LT protein levels. Knockdown of each of these E3 ligases enhances LT stability and promotes MCV genome replication. Mutations at two of these phosphoreceptor sites [serine (S)220 and S239] in the full viral genome increase LT levels and promote MCV virion production and transmission, which can be neutralized with anti-capsid antibody. Virus activation is not mediated by viral gene transactivation, given that these mutations do not increase late gene transcription in the absence of genome replication. Mechanistic target of rapamycin inhibition by either nutrient starvation or use of an active site inhibitor reduces Skp2 levels and stabilizes LT, leading to enhanced MCV replication and transmission. MCV can sense stresses in its intracellular environment, such as nutrient loss, through SCF E3 ligase activities, and responds by initiating active viral transmission. Protein-mediated viral latency through cellular SCF E3 ligase targeting of viral replication proteins is a unique form of latency that may promote chronic viral persistence for some small DNA and RNA viruses.
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