Telomerase activity of Merkel cell carcinomas and Merkel cell carcinoma-derived cell cultures

Ancient cancers and infection-induced oncogenesis

Cancers have been reported in bone and soft tissue of ancient agricultural populations. Fossilized bones from prehistoric periods provide evidence of tumors but only one example of cancer. Difficulties in diagnosing the causes of lesions in mummified tissue and fossilized bone, and in interpreting the prevalence of cancers from remains, draw attention to the need for complementary approaches to assess the occurrence of cancer in ancient populations. This paper integrates current knowledge about pathogen induction of cancer with phylogenetic analyses of oncogenic pathogens, and concludes that pathogen-induced cancers were probably generally present in ancient historic and prehistoric human populations. Consideration of cancers in extant human populations and wildlife lends credence to this conclusion, with the caveat that the presence of cancers may depend on population-specific exposures to oncogenic parasites and carcinogens.

TERT promoter mutations and gene amplification: promoting TERT expression in Merkel cell carcinoma

Telomerase activation through the induction of its catalytic component TERT is essential in carcinogenesis. The regulatory mechanism and clinical significance underlying cancer-specific TERT expression have been extensively investigated in various human malignancies, but little is known about these in Merkel cell carcinoma (MCC), an aggressive neuroendocrine skin tumor. Here we addressed these issues by determining TERT promoter mutations, gene amplification, mRNA expression and association with clinical variables in MCC. TERT mRNA was expressed in 6/6 MCC cell lines and 41 of 43 tumors derived from 35 MCC patients. Telomerase activity was detectable in all 6 cell lines and 11 tumors analyzed. TERT promoter mutations were identified in 1/6 cell lines and 4/35 (11.4%) MCC cases. The mutation exhibited UV signature and occurred in sun-exposed areas. Increased TERT gene copy numbers were observed in 1/6 cell lines and 11/14 (79%) tumors, and highly correlated with its mRNA expression (r = 0.7419, P = 0.0024). Shorter overall survival was significantly associated with higher TERT mRNA levels in MCC patients (P = 0.032). Collectively, TERT expression and telomerase activity is widespread in MCC, and may be attributable to TERT promoter mutations and gene amplification. Higher TERT expression predicts poor patient outcomes.

Merkel cell carcinoma of the head and neck

Merkel cell carcinoma (MCC) is a rare neuroendocrine neoplasm of the skin. The tumor most frequently affects elderly patients, with a preference for the head and neck. Incidence rates increase with sun exposure and after immunosuppression and organ transplantation. A significant proportion of MCC have been reported to occur in intimate association with malignant epithelial neoplasms. The genetic mechanisms underlying the development and tumor progression of MCC are poorly understood, sharing pathogenetic mechanisms with other neoplasms of neural crest derivation. MCC has a propensity for spreading to regional lymph nodes, either at presentation or as a first site of relapse. Sentinel lymph node positivity is helpful in predicting the risk of recurrence or metastasis in patients with MCC. Complete surgical resection is the mainstay of treatment of the primary tumor. Tumor resections are recommended to include a 2-3-cm tumor-free margin around the primary lesion when possible, but this is often difficult to achieve in the head and neck, where Mohs micrographic surgery has proved to be effective. The role of adjuvant radiation therapy is controversial. The role of adjuvant chemotherapy in diminishing the risk of subsequent systemic recurrence in patients with positive nodes remains undefined. Overall response rates to combination chemotherapy for surgically unresectable distant metastatic disease are generally high, although responses are transient. Overall survival of head and neck MCC at 5 years postoperatively ranks between 40% and 68%. MCC has a high incidence of locoregional recurrences, but even after a locoregional failure, a substantial proportion of patients achieve long-term disease-free survival. Finally, factors generally associated with survival are the stage of disease at presentation, distant recurrence usually being the most adverse predictor of survival.

Telomeres and telomerase: a dual role in hepatocarcinogenesis

Telomere shortening limits the proliferative capacity of primary human cells and restrains the regenerative capacity of organ systems during chronic diseases and aging. Telomere shortening apparently has a dual role in tumor development and progression. On the one hand, it induces chromosomal instability and the initiation of cancer; on the other hand, tumor progression requires stabilization of telomeres. The predominant mechanism of telomere stabilization in tumor cells is the activation of the telomere-synthesizing enzyme telomerase. The potential use of telomerase activators for the treatment of regenerative disorders will ultimately depend on their effects on tumorigenesis. This review focuses on the role of telomere shortening and telomerase in carcinogenesis with a special focus on hepatocellular carcinoma.

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.