Detecting the expression of human endogenous retrovirus E envelope transcripts in human prostate adenocarcinoma

Abstract

BACKGROUND The expression of human endogenous retrovirus (HERV) mRNA and proteins was associated recently with diseases that include human malignancies. The authors report that, in the current study, transcripts encoding the envelope region of an HERV family, HERV‐E, were expressed in human prostate carcinoma. METHODS RNA was isolated from various prostate tissues and was tested for the expression of various HERV envelope (env) genes by reverse transcriptase–polymerase chain reaction (RT‐PCR) analysis, RNA in situ hybridization (ISH), and Northern blot analysis. Variants of HERV that appeared in prostate carcinoma tissues were sequenced, and HERV‐E was expressed in prokaryotic and eukaryotic systems. RESULTS In the current study, the authors found that the mRNA of the env gene of one particular family of HERVs, HERV‐E, was expressed in some prostate carcinoma tissues (38.8% positive; n = 49 specimens) but not in normal prostate tissues using RT‐PCR, RNA ISH, and Northern blot assays. The expression of HERV‐E transcripts in prostate tumor epithelial cells was confirmed further by ISH using an HERV‐E specific antisense probe. Approximately 50% of the cDNA of HERV‐E obtained from prostate carcinoma specimens contained no stop codon and expressed proteins in prokaryotic or eukaryotic expression systems. Furthermore, the expression of both HERV‐E and ERV3 (another class of HERV) was detected in the same prostate carcinoma tissues. CONCLUSIONS The expression and distribution of multiple HERV‐E endogenous retroviral elements in prostate carcinoma, but not in normal control specimens, suggests that they may serve as novel tumor markers for the early diagnosis and immunotherapy of patients with prostate carcinoma. Cancer 2003;98:187–97. © 2003 American Cancer Society. DOI 10.1002/cncr.11451