Molecular analysis of 1p36 breakpoints in two Merkel cell carcinomas

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Downregulation of MHC-I expression is prevalent but reversible in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive, polyomavirus-associated skin cancer. Robust cellular immune responses are associated with excellent outcomes in patients with MCC, but these responses are typically absent. We determined the prevalence and reversibility of major histocompatibility complex class I (MHC-I) downregulation in MCC, a potentially reversible immune-evasion mechanism. Cell-surface MHC-I expression was assessed on five MCC cell lines using flow cytometry as well as immunohistochemistry on tissue microarrays representing 114 patients. Three additional patients were included who had received intralesional IFN treatment and had evaluable specimens before and after treatment. mRNA expression analysis of antigen presentation pathway genes from 35 MCC tumors was used to examine the mechanisms of downregulation. Of note, 84% of MCCs (total n = 114) showed reduced MHC-I expression as compared with surrounding tissues, and 51% had poor or undetectable MHC-I expression. Expression of MHC-I was lower in polyomavirus-positive MCCs than in polyomavirus-negative MCCs (P < 0.01). The MHC-I downregulation mechanism was multifactorial and did not depend solely on HLA gene expression. Treatment of MCC cell lines with ionizing radiation, etoposide, or IFN resulted in MHC-I upregulation, with IFNs strongly upregulating MHC-I expression in vitro, and in 3 of 3 patients treated with intralesional IFNs. MCC tumors may be amenable to immunotherapy, but downregulation of MHC-I is frequently present in these tumors, particularly those that are positive for polyomavirus. This downregulation is reversible with any of several clinically available treatments that may thus promote the effectiveness of immune-stimulating therapies for MCC.

Updated Review of the Pathogenesis and Management of Merkel Cell Carcinoma

Background:

Merkel cell carcinoma is a rare, aggressive, malignant cutaneous tumor of the elderly or immunosuppressed individuals that usually appears on sun-exposed areas of the body. Its pathogenesis is still debated, and, currently, no standardized treatment exists.

Objective:

To provide a current updated review of the most relevant data concerning the pathogenesis and management of Merkel cell carcinoma.

Methods:

Using relevant MeSH terms, we performed a review of the literature on these subjects from 1980 to June 2009.

Results and Conclusion:

The current management of Merkel cell carcinoma is based on surgical excision as the majority of patients present with localized disease, whereas up to 30% have regional lymph node metastases. In these cases, the best outcome is achieved with multidisciplinary management that includes radiotherapy. Chemotherapy is part of the treatment in advanced cases and is mandatory for distant metastatis. Given that a recent work showed the presence of a previously unknown polyomavirus, which the authors called Merkel cell polyomavirus, the therapeutical approach to Merkel cell carcinoma could be reconsidered in the future.

SPOC1: a novel PHD-containing protein modulating chromatin structure and mitotic chromosome condensation

In this study, we characterize the molecular and functional features of a novel protein called SPOC1. SPOC1 RNA expression was previously reported to be highest in highly proliferating tissues and increased in a subset of ovarian carcinoma patients, which statistically correlated with poor prognosis and residual disease. These observations implied that SPOC1 might play a role in cellular proliferation and oncogenesis. Here we show that the endogenous SPOC1 protein is labile, primarily chromatin associated and its expression as well as localization are regulated throughout the cell cycle. SPOC1 is dynamically regulated during mitosis with increased expression levels and biphasic localization to mitotic chromosomes indicating a functional role of SPOC1 in mitotic processes. Consistent with this postulate, SPOC1 siRNA knockdown experiments resulted in defects in mitotic chromosome condensation, alignment and aberrant sister chromatid segregation. Finally, we have been able to show, using micrococcal nuclease (MNase) chromatin-digestion assays that SPOC1 expression levels proportionally influence the degree of chromatin compaction. Collectively, our findings show that SPOC1 modulates chromatin structure and that tight regulation of its expression levels and subcellular localization during mitosis are crucial for proper chromosome condensation and cell division.

A comprehensive review of the treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an uncommon but malignant cutaneous neuroendocrine carcinoma with a high incidence of local recurrence, regional lymph node metastases, and subsequent distant metastases. The etiology of MCC remains unknown. It usually occurs in sun-exposed areas in elderly people, many of whom have a history of other synchronous or metachronous sun-associated skin lesions. The outcome for most patients with MCC is generally poor. Surgery is the mainstay of treatment. The role of adjuvant therapy has been debated. However, data from recent development support a multimodality approach, including surgical excision of primary tumor with adequate margins and sentinel lymph node dissection followed by postoperative radiotherapy in most cases, as current choice of practice with better locoregional control and disease-free survival. Patients with regional nodal involvement or advanced disease should undergo nodal dissection followed by adjuvant radiotherapy and, perhaps, systemic platinum-based chemotherapy in most cases.

Merkel Cell Carcinomas

Merkel cell carcinoma (MCC) is a rare and extremely aggressive skin cancer that arises from primary neural cells. It presents most commonly in the elderly and immunocompromised patients. Pathologically, MCC should be distinguished from extrapulmonary small cell lung cancer or metastatic small cell lung cancer or a small cell variant of melanoma. The prognosis is based largely on the stage of disease at the time of presentation. Therapeutic options for MCC include wide resection with or without adjuvant radiotherapy or chemotherapy. Novel therapies based on the understanding of the molecular aspects of MCC are currently being explored.

Apoptotic DNA fragmentation factor maintains chromosome stability in a P53-independent manner

DNA fragmentation factor (DFF)/caspase-activated DNase (CAD) is responsible for DNA fragmentation, a hallmark event during apoptosis. Although DNA fragmentation is an evolutionarily conserved process across species, its biological function is not clearly understood. In this study, we constructed cell lines expressing a mutant ICAD (inhibitor of CAD) protein that is resistant to caspase cleavage and therefore constantly binds to DFF/CAD and inhibits DNA fragmentation. We found that irradiation of these cells led to increased chromosome aberrations and aneuploidy when compared with their parental controls. The increased chromosome instability is observed irrespective of cellular P53 status, suggesting that the effect of DFF/CAD is independent of P53. Inhibition of apoptotic DNA fragmentation resulted in increased clonogenic survival of irradiated cells and a delay in removal of cells with DNA damages induced by radiation, an effect similar to that in cells with p53 mutations. Consistent with DFF/CAD's effect on clonogenic survival, tumors established from cells deficient in DNA fragmentation showed enhanced growth in nude mice. Therefore, our results suggest that DFF/CAD plays an important and P53-independent role in maintaining chromosome stability and suppressing tumor development.

Merkel cell cancer of the skin

Merkel cell carcinoma (MCC) is a rare malignant cutaneous tumor of the elderly with rapidly growing skin nodules found predominantly on sun-exposed areas of the body. The vast majority of patients present with localized disease, while up to 30% have regional lymph node metastases. Despite local excision and the incidence of local recurrence, regional lymph node metastases and distant metastases is high and usually occurs within 2 years of primary diagnosis. The optimal treatment for patients with MCC remains unclear. The best outcome is achieved with multidisciplinary management including surgical excision of primary tumor with adequate margins and post-operative radiotherapy (RT) to control local and regional disease. Patients with regional nodal metastases should be treated with lymph node dissection plus RT. Adjuvant chemotherapy (CT) should be considered as part of the initial management. In case of metastatic disease CT based on regimens used for small-cell lung cancer is the standard treatment of care.

Merkel cell carcinoma

Background

Merkel cell carcinoma (MCC) is an unusual primary neuroendocrine carcinoma of the skin. MCC is a fatal disease, and patients have a poor chance of survival. Moreover, MCC lacks distinguishing clinical features, and thus by the time the diagnosis is made, the tumour usually have metastasized. MCC mainly affects sun-exposed areas of elderly persons. Half of the tumours are located in the head and neck region.

Methods

MCC was first described in 1972. Since then, most of the cases reported, have been in small series of patients. Most of the reports concern single cases or epidemiological studies. The present study reviews the world literature on MCC. The purpose of this article is to shed light on this unknown neuroendocrine carcinoma and provide the latest information on prognostic markers and treatment options.

Results

The epidemiological studies have revealed that large tumour size, male sex, truncal site, nodal/distant disease at presentation, and duration of disease before presentation, are poor prognostic factors. The recommended initial treatment is extensive local excision. Adjuvant radiation therapy has recently been shown to improve survival. Thus far, no chemotherapy protocol have achieved the same objective.

Conclusion

Although rare, the fatality of this malignancy makes is important to understand the etiology and pathophysiology. During the last few years, the research on MCC has produced prognostic markers, which can be translated into clinical patient care.

UV-induced Skin Cancer: Similarities - Variations. Durch UV-Strahlung induzierte Hauttumore: Gemeinsamkeiten - Unterschiede

Skin cancer, the most common cancer world wide, encompasses different tumor entities, the keratinocyte-derived basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) as well as the neuroectodermal malignant melanoma (MM) and the neuroendocrine Merkel cell carcinomas (MCC). While knowledge is significantly increasing about genetic changes contributing to BCCs and MMs, our understanding for the development and progression of SCCs and MCCs is still fragmentary. This review, thus, aims, on the one hand to summarize the present knowledge without claiming completeness and, on the other hand, to provide information on the HaCaT in vitro skin carcinogenesis model that is used to evaluate the functional consequence of genetic aberrations believed to play a role in skin cancer development and progression.

Skeletrophin, a novel RING molecule controlled by the chromatin remodeling complex, is downregulated in malignant melanoma

Recent experiments have revealed that aberrant functionality of the chromatin remodeling complex is related to tumorigenicity in various malignant tumors. Skeletrophin is an actin-binding cytoskeleton-related molecule, which is induced by the overexpression of truncated human SWI1 (SMARCF1). Human SWI1 is a sub-unit of the chromatin remodeling complex and binds chromatin through its ARID (AT-rich interactive domain). Truncated SWI1 lacks one of the two glucocorticoid-receptor binding domains and inhibits the intact human SWI1 in a dominant negative manner. Skeletrophin, was therefore identified as a candidate molecule for the indication of change to a malignant phenotype due to the aberrant function of the chromatin remodeling complex. Surprisingly, the skeletrophin gene is located in 1p36.32, where the putative tumor suppressor gene of cutaneous malignant melanoma has long been postulated to be on. Cutaneous malignant melanoma is a highly aggressive tumor. To overcome the clinical problem of malignant melanoma and highly invasive and metastatic activity, it is important to unravel the molecular mechanism responsible for melanoma progression. Recent studies including those from our laboratories have elucidated that skeletrophin is a novel RING-HC type ubiquitin ligase and that the ubiquitin ligase pathway mediated by skeletrophin acts to oppose melanoma cell invasion. Here, we summarize the characterization of skeletrophin, with emphasis on its biological activity, the disruption of which is linked with melanoma progression.

Combined karyotyping, CGH and M-FISH analysis allows detailed characterization of unidentified chromosomal rearrangements in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine tumor of the skin. Cytogenetic studies have indicated that deletions and unbalanced translocations involving chromosome 1 short arm material occur in 40% of the investigated cases. Recurrent chromosomal imbalances detected by comparative genomic hybridization (CGH) analysis were loss of 3p, 10q, 13q and 17p and gains of 1q, 3q, 5p and 8q. In order to study genomic aberrations occurring in MCC in further detail, we combined karyotyping, CGH and multiplex-fluorescence in situ hybridization (M-FISH), a strategy that proved to be successful in the analysis of other malignancies. Analysis of 6 MCC cell lines and 1 MCC tumor revealed mostly near-diploid karyotypes with an average of 5 chromosomal rearrangements. The observed karyotypic changes were heterogeneous, with 3-27 breakpoints per case, leading to imbalance of the involved chromosomal regions that was confirmed by CGH. Chromosomal rearrangements involving the short arm of chromosome 1, the long arm of chromosome 3 and gain of 5p material were the most frequently observed abnormalities in our study. In keeping with previous observations, this series of MCCs showed no evidence for high-level amplification. We provid a detailed description of chromosomal translocations occurring in MCC that could be useful to direct future intensive investigation of these chromosomal regions.

The effect of aloe emodin on the proliferation of a new merkel carcinoma cell line

A free-floating cell line has been established from a metastatic lesion of a Merkel cell carcinoma (MCC) patient. The cell line was characterized by immunocytochemical reactions with antibodies against the epithelial and neuroendocrine antigens: cytokeratin 20, neuron-specific enolase, chromogranin A, neurofilament protein, synaptophysin, and calcitonin. Karyotype analysis of the MCC cells showed deletion in chromosomes 3 and 7, loss of chromosome 10, and several translocations in other chromosomes. No mutation was detected in the TP53 gene, after analyzing the complete coding region. Growth factors such as basic fibroblast growth factor, transforming growth factor-beta, and nerve and epidermal growth factors had no effect on the proliferation of the cells. The differentiation-inducing agents sodium butyrate and dimethyl sulfoxide, especially the former, markedly inhibited the proliferation of the MCC cells. Aloe emodin, a natural constituent of aloe vera leaves, significantly inhibited the growth of MCC cells. Aloe emodin has been reported to be nontoxic for normal cells but to possess specific toxicity for neuroectodermal tumor cells. Differentiation-inducing agents, and aloe emodin, merit further investigation as potential agents for treating MCC.

CDKN2A is not the principal target of deletions on the short arm of chromosome 9 in neuroendocrine (Merkel cell) carcinoma of the skin

The majority of small-cell lung cancers (SCLCs) express p16 but not pRb. Given our previous study showing loss of pRb in Merkel cell carcinoma (MCC)/neuroendocrine carcinoma of the skin and the clinicopathological similarities between SCLC and MCC, we wished to determine if this was also the case in MCC. Twenty-nine MCC specimens from 23 patients were examined for deletions at 10 loci on 9p and 1 on 9q. No loss of heterozygosity (LOH) was seen in 9 patients including 2 for which tumour and cell line DNAs were examined. Four patients had LOH for all informative loci on 9p. Ten tumours showed more limited regions of loss on 9p, and from these 2 common regions of deletion were determined. Half of all informative cases had LOH at D9S168, the most telomeric marker examined, and 3 specimens showed loss of only D9S168. A second region (IFNA-D9S126) showed LOH in 10 (44%) cases, and case MCC26 showed LOH for only D9S126, implicating genes centromeric of the CDKN2A locus. No mutations in the coding regions of p16 were seen in 7 cell lines tested, and reactivity to anti-p16 antibody was seen in all 11 tumour specimens examined and in 6 of 7 cell lines from 6 patients. Furthermore, all cell lines examined reacted with anti-p14(ARF) antibody. These results suggest that neither transcript of the CDKN2A locus is the target of deletions on 9p in MCC and imply the existence of tumour-suppressor genes mapping both centromeric and telomeric of this locus.

Frequent allelic loss at 10q23 but low incidence of PTEN mutations in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, highly metastatic skin tumor of neuroectodermal origin. The disease shares clinical and histopathological features with small cell lung carcinoma (SCLC). The genetic mechanisms underlying the development and tumor progression of MCC are poorly understood. We recently showed by comparative genomic hybridization (CGH) that the pattern of chromosomal abnormalities in MCC resembles that of SCLC. One of the most frequently observed losses involved the entire chromosome 10 or partial loss of the chromosome 10 long arm (33% of examined MCC cases). The PTEN tumor-suppressor gene has been mapped to 10q23.3 and was shown to be mutated in a variety of human cancers including SCLC. Germline PTEN mutations have been observed in familial predisposing cancer syndromes including Cowden disease. Interestingly, an association between Cowden syndrome and Merkel cell carcinoma has been reported. To study the possible role of PTEN in MCC oncogenesis, loss of heterozygosity (LOH) analysis for the 10q23 region was performed on 26 MCC tumor samples from 23 MCC patients. The PTEN locus was deleted in 9 of 21 (43%) informative MCC tumor samples [7 of 18 (39%) MCC patients]. Despite this high frequency of LOH at 10q23, mutation and homozygous deletion screening of the PTEN gene revealed only one tumor with a nonsense mutation and a second with a homozygous deletion of exon 9. These data suggest that either alternative mechanisms lead to inactivation of the PTEN gene or that other tumor-suppressor genes at chromosome 10 are implicated in the development of MCC.

Fine-needle aspiration diagnosis of unusual cutaneous neoplasms of the scalp in HIV-infected patients: a report of two cases and review of the literature

We report on two unusual, non-AIDS-defining scalp neoplasms, Merkel-cell carcinoma (MCC) and malignant melanoma, in 2 men with acquired immunodeficiency syndrome (AIDS). In the first patient, metastatic MCC was initially diagnosed by fine-needle aspiration (FNA) of a posterior cervical lymph node, based on the cytomorphology and the characteristic immunohistochemical and ultrastructural features. No skin lesion was initially apparent, but a 0.3-mm scalp primary was found during the ensuing neck dissection. In the second patient, recurrent and metastatic malignant melanoma from a Breslow 1.3-mm scalp primary was diagnosed by FNA. Both patients developed generalized disease in a relatively short time, despite their small primaries. These cases illustrate the occurrence of Merkel-cell carcinoma and melanoma in AIDS patients, and stress the need to consider these unusual cutaneous neoplasms when evaluating lymph node FNA samples from HIV-positive patients, especially since both may present as metastases from clinically occult primaries.

Trisomy 6 in Merkel cell carcinoma: a recurrent chromosomal aberration

We retrospectively investigated 17 cases of primary and metastasizing Merkel cell carcinomas (MCC) from 14 patients using chromosomal in-situ hybridization (CISH) to study the occurrence of trisomy 6 in these lesions.

METHODS AND RESULTS

Histological diagnosis on all tumour samples was obtained on haematoxylin and eosin stained sections. Immunohistochemistry was performed with antibodies against pancytokeratin (CAM 5.2), cytokeratin 20 (CK20), MIC2 antigen (CD99), neuron-specific enolase (NSE), and chromogranin A (chrA). Sections (4 microm) of the paraffin-embedded tumours were analysed with alpha-satellite centromeric probes for chromosome 6 or 17 using CISH. The signal was amplified by the Tyramide Signal Amplification (TSA) assay. Immunohistochemically, the tumours showed the same general epithelial neuro-endocrine pattern: 11/13 expressed cytokeratin 20, and 47% exhibited trisomy 6, with no significant difference between primary and metastatic lesions. Incomplete follow-up data did not allow us to establish a prognostic value of trisomy 6, however, this aberration might be an additional diagnostic tool in distinguishing MCC from other small round blue cell tumours.

CONCLUSIONS

CISH seems to be a promising adjunctive method to diagnose Merkel cell carcinoma. Trisomy 6 should be investigated more closely in these cases, as has been done for chromosomes 1 and 11. Of particular interest would be identification of modifications in proto-oncogene(s) located on chromosome 6.

Mutation analysis of P73 and TP53 in Merkel cell carcinoma

The p73 gene has been mapped to 1p36.33, a region which is frequently deleted in a wide variety of neoplasms including tumours of neuroectodermal origin. The p73 protein shows structural and functional homology to p53. For these reasons, p73 was considered as a positional and functional candidate tumour suppressor gene. Thus far, mutation analysis has provided no evidence for involvement of p73 in oligodendrogliomas, lung carcinoma, oesophageal carcinoma, prostatic carcinoma and hepatocellular carcinoma. In neuroblastoma, two mutations have been observed in a series of 140 tumours. In view of the occurrence of 1p deletions in Merkel cell carcinoma (MCC) and the location of p73 we decided to search for mutations in the p73 gene in five MCC cell lines and ten MCC tumours to test potential tumour suppressor function for this gene in MCC. In view of the possible complementary functions of p73 and TP53 we also examined the status of the TP53 gene. Sequence analysis of the entire coding region of the p73 gene revealed previously reported polymorphisms in four MCCs. In one MCC tumour, a mis-sense mutation located in the NH2-terminal transactivation region of the p73 gene was found. These results show that p73, analogous to neuroblastoma, is infrequently mutated in MCC. This is also the first report in which the role of TP53 in MCC has been investigated by sequencing the entire coding region of TP53. TP53 mis-sense mutations and one non-sense mutation were detected in three of 15 examined MCCs, suggesting that TP53 mutations may play a role in the pathogenesis or progression of a subset of MCCs. Moreover, typical UVB induced C to T mutations were found in one MCC cell line thus providing further evidence for sun-exposure in the aetiology of this rare skin cancer.

Loss of heterozygosity in human skin

Loss of heterozygosity (LOH) is a genetic mechanism by which a heterozygous somatic cell becomes either homozygous or hemizygous because the corresponding wild-type allele is lost. LOH has today been recognized as a major cause of malignant growth. This article gives a comprehensive review of skin disorders in which an origin from LOH has been either documented at the molecular level or postulated on the basis of clinical evidence. LOH has been shown to cause basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, but this mechanism can likewise be taken as an important model to explain the origin of many other skin diseases such as benign hamartomas; type 2 segmental manifestation of autosomal dominant skin disorders; a pronounced segmental manifestation of acquired skin disorders with a polygenic background, superimposed on symmetric lesions of the usual type; paired mutant patches in the form of either allelic or nonallelic twin spotting; and the exceptional familial occurrence of some nevi, reflecting paradominant transmission. completion of this learning activity, readers should be familiar with the mechanism of LOH and its general significance for the biology of plants, animals, and humans. Participants should understand that this mechanism plays a crucial role not only in cutaneous malignant growth but also in the development of benign skin disorders, and they should be able to examine such diseases with a prepared mind to gain a better understanding of their origin.