Published in:
Journal of Cutaneous Pathology, 23 (1996) 2, Seite 109-117
Language:
English
DOI:
10.1111/j.1600-0560.1996.tb01283.x
ISSN:
0303-6987;
1600-0560
Origination:
Footnote:
Description:
The bcl‐2 gene, originally identified in B‐cell lymphomas, encodes for proteins which may assume oncogenic functions by blocking apoptosis. Bcl‐2 proteins are broadly distributed among various tissues, including epithelial ones. Within the skin, bcl‐2 is strongly expressed in melanocytes, but its further distribution is yet unclear. The Merkel cells, neuroendocrine‐epithelial cells of the skin, are present within the epidermis and hair follicles, mostly nerve‐associated, and are believed to be postmitotic and long lived. Possibly they give rise to the malignant Merkel cell carcinomas. In the present study we investigated the bcl‐2 expression on the protein level by means of immunohistochemical techniques including double confocal laser scanning microscopy, as well as on the RNA level by RT‐PCR techniques, in Merkel cells, Merkel cell carcinomas, and cell lines. Merkel cells were identified by double staining for cytokeratins 20 or 8/18. We demonstrate that fetal epidermal and dermal Merkel cells are immunostained for bcl‐2 protein, most of them clearly weaker than melanocytes. Adult Merkel cells also express bcl‐2 protein very heterogeneously, mostly weak. In contrast, Merkel cell carcinomas are visually strongly positive for bcl‐2 protein with some degree of heterogeneity. This is different from malignant melanomas in which bcl‐2 expression is reduced as compared to normal melanocytes. Bcl‐2 gene expression was also shown for Merkel cell carcinoma cell lines on both the mRNA and the protein level. Possibly bcl‐2 protein expression is downregulated during the life span of Merkel cells, arguing that they may succumb to a certain cell turnover. The comparably high bcl‐2 protein level in Merkel cell carcinomas may reflect peculiar biological and clinical characteristics.