Expression of the RNA component of human telomerase in adult testicular germ cell neoplasia

Abstract

During human development, telomerase is repressed in most somatic cells, whereas it is maintained in male germline cells. Reactivation of telomerase has been associated with somatic cancers. To the authors' knowledge, the role of telomerase in germ cell derived malignancies has not previously been evaluated. A radioactive in situ hybridization method was used to study the expression of the RNA component of human telomerase (hTR) in 22 cases of adult testicular germ cell neoplasia encompassing all major histomorphologic types. For precise cell identification, hTR in situ hybridization was combined with immunohistochemistry in select cases. Testicular germ cell tumors showed differential expression of hTR. The highest level of expression was seen in embryonal carcinoma. Seminoma and unclassified intratubular germ cell neoplasia exhibited moderate levels of expression. Yolk sac tumor was characterized by a range of expression, which mirrored its morphologic variation. Immature teratoma recapitulated the down-regulation of telomerase manifested during human embryogenesis. Mature teratoma represented the adult pattern of somatic repression. Notably, choriocarcinoma showed modest expression. The expression of spermatocytic seminoma was intermediate between that of classic seminoma and embryonal carcinoma. No difference in expression was evident between matching intratubular and invasive components. In nonneoplastic testis, hTR expression was down-regulated during spermatogenesis and was absent in spermatozoa. Expression was negligible in rete testis and interstitial Leydig cells, and low in epididymis. Unexpectedly, Sertoli cells, which are testicular accessory somatic cells, displayed the most intense expression observed in this study. In testicular germ cell tumors of young adults (and during spermatogenesis), hTR expression is down-regulated with differentiation, irrespective of the aggressiveness of the tumors. Spermatocytic seminoma, regarded as a low grade malignancy, shows moderately intense expression.