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The Journal of Clinical Investigation Apr 2022Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer that frequently carries an integrated Merkel cell polyomavirus (MCPyV) genome and expresses viral...
Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer that frequently carries an integrated Merkel cell polyomavirus (MCPyV) genome and expresses viral transforming antigens (TAgs). MCC tumor cells also express signature genes detected in skin-resident, postmitotic Merkel cells, including atonal bHLH transcription factor 1 (ATOH1), which is required for Merkel cell development from epidermal progenitors. We now report the use of in vivo cellular reprogramming, using ATOH1, to drive MCC development from murine epidermis. We generated mice that conditionally expressed MCPyV TAgs and ATOH1 in epidermal cells, yielding microscopic collections of proliferating MCC-like cells arising from hair follicles. Immunostaining of these nascent tumors revealed p53 accumulation and apoptosis, and targeted deletion of transformation related protein 53 (Trp53) led to development of gross skin tumors with classic MCC histology and marker expression. Global transcriptome analysis confirmed the close similarity of mouse and human MCCs, and hierarchical clustering showed conserved upregulation of signature genes. Our data establish that expression of MCPyV TAgs in ATOH1-reprogrammed epidermal cells and their neuroendocrine progeny initiates hair follicle-derived MCC tumorigenesis in adult mice. Moreover, progression to full-blown MCC in this model requires loss of p53, mimicking the functional inhibition of p53 reported in human MCPyV-positive MCCs.
Topics: Animals; Antigens, Viral; Antigens, Viral, Tumor; Carcinoma, Merkel Cell; Cellular Reprogramming; Merkel cell polyomavirus; Mice; Polyomavirus Infections; Skin Neoplasms; Tumor Virus Infections
PubMed: 35143422
DOI: 10.1172/JCI152069 -
Scientific Reports Aug 2023The pathogenesis of 80% of Merkel cell carcinoma (MCC) cases is associated with Merkel cell polyomavirus (MCPyV). Forkhead helix transcription factor P3 (FOXP3) and the...
The pathogenesis of 80% of Merkel cell carcinoma (MCC) cases is associated with Merkel cell polyomavirus (MCPyV). Forkhead helix transcription factor P3 (FOXP3) and the T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif domains (TIGIT)-CD155 pathway, which are targets for immunotherapy, were assessed as prognostic factors of MCC. We analyzed mRNA expression data of 111 patients with MCC and performed immunohistochemical analysis to detect the expression of programmed death ligand 1 (PD-L1), CD8, FOXP3, TIGIT, and CD155 in 65 cases of MCC. In CD8 and FOXP3 immunostaining, the number of expressing-infiltrating cells was determined by dividing the region into tumor center and invasive front areas. FOXP3 expression was evaluated separately in cells with high and low intensities. Aberrant TIGIT expression and weak CD155 staining were observed in MCC cells. CD8- and FOXP3-positive cell infiltrations were higher in the invasive front than in the tumor center. Multivariate Cox hazard analysis revealed that high infiltration of cells with low-intensity FOXP3 expression in the invasive front is a favorable prognostic factor (p = 0.025). Thus, targeting TIGIT-CD155 signaling and FOXP3 as well as PD-L1 may be a therapeutic strategy for MCC.
Topics: Humans; Carcinoma, Merkel Cell; B7-H1 Antigen; Skin Neoplasms; Clinical Relevance; Receptors, Immunologic; Forkhead Transcription Factors
PubMed: 37573372
DOI: 10.1038/s41598-023-40050-7 -
Journal For Immunotherapy of Cancer Sep 2022Merkel cell carcinoma (MCC) often responds to PD-1 pathway blockade, regardless of tumor-viral status (~80% of cases driven by the Merkel cell polyomavirus (MCPyV))....
BACKGROUND
Merkel cell carcinoma (MCC) often responds to PD-1 pathway blockade, regardless of tumor-viral status (~80% of cases driven by the Merkel cell polyomavirus (MCPyV)). Prior studies have characterized tumor-specific T cell responses to MCPyV, which have typically been CD8, but little is known about the T cell response to UV-induced neoantigens.
METHODS
A patient in her mid-50s with virus-negative (VN) MCC developed large liver metastases after a brief initial response to chemotherapy. She received anti-PD-L1 (avelumab) and had a partial response within 4 weeks. Whole exome sequencing (WES) was performed to determine potential neoantigen peptides. Characterization of peripheral blood neoantigen T cell responses was evaluated via interferon-gamma (IFNγ) ELISpot, flow cytometry and single-cell RNA sequencing. Tumor-resident T cells were characterized by multiplexed immunohistochemistry.
RESULTS
WES identified 1027 tumor-specific somatic mutations, similar to the published average of 1121 for VN-MCCs. Peptide prediction with a binding cut-off of ≤100 nM resulted in 77 peptides that were synthesized for T cell assays. Although peptides were predicted based on class I HLAs, we identified circulating CD4 T cells targeting 5 of 77 neoantigens. In contrast, no neoantigen-specific CD8 T cell responses were detected. Neoantigen-specific CD4 T cells were undetectable in blood before anti-PD-L1 therapy but became readily detectible shortly after starting therapy. T cells produced robust IFNγ when stimulated by neoantigen (mutant) peptides but not by the normal (wild-type) peptides. Single cell RNAseq showed neoantigen-reactive T cells expressed the Th1-associated transcription factor (T-bet) and associated cytokines. These CD4 T cells did not significantly exhibit cytotoxicity or non-Th1 markers. Within the pretreatment tumor, resident CD4 T cells were also Th1-skewed and expressed T-bet.
CONCLUSIONS
We identified and characterized tumor-specific Th1-skewed CD4 T cells targeting multiple neoantigens in a patient who experienced a profound and durable partial response to anti-PD-L1 therapy. To our knowledge, this is the first report of neoantigen-specific T cell responses in MCC. Although CD4 and CD8 T cells recognizing viral tumor antigens are often detectible in virus-positive MCC, only CD4 T cells recognizing neoantigens were detected in this patient. These findings suggest that CD4 T cells can play an important role in the response to anti-PD-(L)1 therapy.
Topics: Female; Humans; Antigens, Viral, Tumor; Carcinoma, Merkel Cell; CD4-Positive T-Lymphocytes; Interferon-gamma; Merkel cell polyomavirus; Programmed Cell Death 1 Receptor; Skin Neoplasms; Transcription Factors
PubMed: 36252564
DOI: 10.1136/jitc-2022-005328 -
BioRxiv : the Preprint Server For... Sep 2023Sensory cells often adopt specific morphologies that aid in the detection of external stimuli. Merkel cells encode gentle touch stimuli in vertebrate skin and adopt a...
Sensory cells often adopt specific morphologies that aid in the detection of external stimuli. Merkel cells encode gentle touch stimuli in vertebrate skin and adopt a reproducible shape characterized by spiky, actin-rich microvilli that emanate from the cell surface. The mechanism by which Merkel cells acquire this stereotyped morphology from basal keratinocyte progenitors is unknown. Here, we establish that dendritic Merkel cells (dMCs) express , extend dynamic filopodial processes, and arise in transient waves during zebrafish skin development and regeneration. We find that dMCs share molecular similarities with both basal keratinocytes and Merkel cells, yet display mesenchymal-like behaviors, including local cell motility and proliferation within the epidermis. Furthermore, dMCs can directly adopt the mature, microvilliated Merkel cell morphology through substantial remodeling of the actin cytoskeleton. Loss of Ectodysplasin A signaling alters the morphology of dMCs and Merkel cells within specific skin regions. Our results show that dMCs represent an intermediate state in the Merkel cell maturation program and identify Ectodysplasin A signaling as a key regulator of Merkel cell morphology.
PubMed: 37745341
DOI: 10.1101/2023.09.14.557830 -
The Anatomical Record. Part A,... Mar 2003Merkel nerve endings are mechanoreceptors in the mammalian skin. They consist of large, pale cells with lobulated nuclei forming synapse-like contacts with enlarged... (Review)
Review
Merkel nerve endings are mechanoreceptors in the mammalian skin. They consist of large, pale cells with lobulated nuclei forming synapse-like contacts with enlarged terminal endings of myelinated nerve fibers. They were first described by F.S. Merkel in 1875. They are found in the skin and in those parts of the mucosa derived from the ectoderm. In mammals (apart from man), the largest accumulation of Merkel nerve endings is found in whiskers. In all vertebrates, Merkel nerve endings are located in the basal layer of the epidermis, apart from birds, where they are located in the dermis. Cytoskeletal filaments consisting of cytokeratins and osmiophilic granules containing a variety of neuropeptides are found in Merkel cells. In anseriform birds, groups of cells resembling Merkel cells, with discoid nerve terminals between cells, form Grandry corpuscles. There has been controversy over the origin of Merkel cells. Results from chick/quail chimeras show that, in birds, Merkel cells are a subpopulation of cells derived from the neural crest, which thus excludes their development from the epidermis. Most recently, also in mammals, conclusive evidence for a neural crest origin of Merkel cells has been obtained. Merkel cells and nerve terminals form mechanoreceptors. Calcium ions enter Merkel cells in response to mechanical stimuli, a process which triggers the release of calcium from intracellular stores resulting in exocytosis of neurotransmitter or neuromodulator. Recent results suggest that there may be glutamatergic transmission between Merkel cell and nerve terminal, which appears to be essential for the characteristic slowly adapting response of these receptors during maintained mechanical stimuli. Thus, we are convinced that Merkel cells with associated nerve terminals function as mechanoreceptor cells. Cells in the skin with a similar appearance as Merkel cells, but without contact to nerve terminals, are probably part of a diffuse neuroendocrine system and do not function as mechanoreceptors. Probably these cells, rather than those acting as mechanoreceptors, are the origin of a highly malignant skin cancer called Merkel cell carcinoma.
Topics: Animals; Epidermal Cells; Epidermis; Humans; Mechanoreceptors; Merkel Cells; Nerve Endings; Neural Crest; Skin
PubMed: 12552639
DOI: 10.1002/ar.a.10029 -
Oncogene Mar 2018Merkel 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... (Review)
Review
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.
Topics: Animals; Carcinoma, Merkel Cell; Cell Transformation, Neoplastic; Cell Transformation, Viral; Humans; Merkel cell polyomavirus; Mice; Polyomavirus Infections; Skin Neoplasms; Tumor Virus Infections
PubMed: 29321666
DOI: 10.1038/s41388-017-0073-3 -
Anatomical Record (Hoboken, N.J. : 2007) Sep 2016Merkel cells (MCs) are specialized cutaneous receptor cells involved with tactile sense. Although the distribution of MCs has been extensively studied in humans and...
Merkel cells (MCs) are specialized cutaneous receptor cells involved with tactile sense. Although the distribution of MCs has been extensively studied in humans and rodents, their precise distribution and density throughout skin in the dog has not previously been determined. Knowledge of their distribution could facilitate understanding of their functions. By using of immunohistochemistry, density, and anatomical mapping of the MCs population in the dog skin was determined. Assessment of the MCs innervation was also achieved. Different patterns were noted in epidermis, hair follicles, or mucosa, including variable-sized clusters, linear or horse-shaped arrangements, and scattered and individualized cells. MCs revealed great variations in density and distribution over the body surface, with the highest numbers in oral mucosa and facial skin. There was no correlation of MCs density with age, sex, type of breed, coat type or pigmentation. Between 41 and 65% of MCs in hairy and glabrous skin and 8-18% of MCs in oral mucosa were in intimate contact with intraepithelial axon terminals. These findings indicate that canine MCs are numerous in sensory receptive areas and may be associated with the tactile sense in the dog. The present article enhances the knowledge of the skin structure in this species. Anat Rec, 299:1157-1164, 2016. © 2016 Wiley Periodicals, Inc.
Topics: Animals; Biomarkers; Dogs; Epidermal Cells; Epidermis; Female; Hair Follicle; Keratin-20; Male; Merkel Cells; Mouth Mucosa; Skin
PubMed: 27341526
DOI: 10.1002/ar.23387 -
Veterinary and Comparative Oncology Jun 2021Merkel cell carcinoma (MCC) is in humans and cats a malignant cutaneous neuroendocrine carcinoma, whereas in dogs it possibly has a more benign behaviour. It may be...
Merkel cell carcinoma (MCC) is in humans and cats a malignant cutaneous neuroendocrine carcinoma, whereas in dogs it possibly has a more benign behaviour. It may be cytologically confused with round cell tumours such as lymphoma because of its striking cytomorphologic similarity. Although MCC is considered to arise from Merkel cells, recent findings indicated that primitive (epi-)dermal stem cells, early B-cells or dermal fibroblasts were the origin of human MCC. The aim of our study was to evaluate a possible lymphoid origin in feline and canine MCCs. Specific analysis of CD3, PAX-5, KIT and PARR assay were performed in 3 feline and 3 canine MCCs. All MCCs (6/6) were negative for CD3 and PAX-5. KIT was expressed in all MCCs (6/6). Assessment of clonality by PARR assay exhibited a polyclonal B- and T-cell receptor rearrangement in all five cases tested. In conclusion, a lymphoid origin of feline and canine MCCs could not be demonstrated. This is in contrast with human MCCs, that often express early B-cell lineage markers.
Topics: Animals; B-Lymphocytes; Carcinoma, Merkel Cell; Cat Diseases; Cats; Dog Diseases; Dogs; Skin Neoplasms
PubMed: 33372715
DOI: 10.1111/vco.12672 -
Cell Apr 2014Sensory systems for detecting tactile stimuli have evolved from touch-sensing nerves in invertebrates to complicated tactile end organs in mammals. Merkel discs are...
Sensory systems for detecting tactile stimuli have evolved from touch-sensing nerves in invertebrates to complicated tactile end organs in mammals. Merkel discs are tactile end organs consisting of Merkel cells and Aβ-afferent nerve endings and are localized in fingertips, whisker hair follicles, and other touch-sensitive spots. Merkel discs transduce touch into slowly adapting impulses to enable tactile discrimination, but their transduction and encoding mechanisms remain unknown. Using rat whisker hair follicles, we show that Merkel cells rather than Aβ-afferent nerve endings are primary sites of tactile transduction and identify the Piezo2 ion channel as the Merkel cell mechanical transducer. Piezo2 transduces tactile stimuli into Ca(2+)-action potentials in Merkel cells, which drive Aβ-afferent nerve endings to fire slowly adapting impulses. We further demonstrate that Piezo2 and Ca(2+)-action potentials in Merkel cells are required for behavioral tactile responses. Our findings provide insights into how tactile end-organs function and have clinical implications for tactile dysfunctions.
Topics: Action Potentials; Animals; Calcium; Gene Knockdown Techniques; Ion Channels; Mechanoreceptors; Mechanotransduction, Cellular; Merkel Cells; Rats; Touch; Vibrissae
PubMed: 24746027
DOI: 10.1016/j.cell.2014.02.026