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

Merkel cell carcinomas are rare malignant tumors of the skin, which are pre dominantly observed in elderly patients (mean age 65-70 years). It is belie ved but not yet proven that these tumors are derived from the Merkel cells of the epidermis and hair follicles. The Merkel cells themselves probably o riginate from an asymmetric cell division of basal keratinocytes and the re sulting differentiated Merkel cells have presumably, at least in humans, lo st their growth potential. The capability of indefinite cell division in ge rm line cells and in the great majority of malignant tumors as well as an i ncreased growth potential in certain somatic cells (such as basal cells of renewable tissues) is correlated with cellular telomerase activity, which i s absent in differentiated somatic cells. In this study the telomerase acti vity in cryostat sections of frozen Merkel cell tumor biopsies and in in vi tro cultivated Merkel cell carcinoma cells was analyzed. We detected telome rase activity in four tumors and three of four cell cultures. These results show that despite their pronounced neuroendocrine differentiation and thei r occurrence in patients of advanced age, Merkel cell carcinomas possess te lomerase activity similar to that of common carcinoma types.