A novel human prostate-specific gene-1 (HPG-1): molecular cloning, sequencing, and its potential involvement in prostate carcinogenesis

Abstract

Prostate-specific genes that have a role in normal and abnormal prostate growth are needed for early and specific diagnosis and treatment of prostate cancer. In the present study, the differential display-PCR technique was used to obtain a prostate-specific approximately 339-bp cDNA fragment. On screening the human-prostate lambdagt10 library with this fragment, a full-length 1468-bp human prostate-specific gene (HPG-1) with an open reading frame of 127 amino acids (aa) was retrieved. Extensive database search revealed that the HPG-1 has novel nucleotide/aa sequences. It was localized on Homo sapiens 3q26 chromosomal locus, a region that has been shown to be involved in prostate carcinoma. The computer-generated translated protein has a calculated molecular mass of 14.8 kDa with several potential glycosylation and phosphorylation sites including two N-linked glycosylation, one tyrosine phosphorylation, and one N-myristoylation sites. The in vitro transcription and translation procedures using HPG-1 cDNA yielded a protein of similar molecular mass of approximately 15 kDa. Hydrophilicity analysis of the deduced aa sequence indicated that HPG-1 is a membrane-anchored/attached protein. Analysis for tissue specificity by using the Northern blot and reverse transcription-PCR-Southern blot procedures using 19 different human tissues revealed that HPG-1 is expressed specifically only in prostate tissue. To examine its involvement in prostate carcinogenesis, three prostate cancer epithelial cell lines, one androgen-responsive (LNCaP) and two androgen-nonresponsive (DU-145 and PC-3), were examined for the expression of HPG-1. Using the Northern blot and quantitative reverse transcription-PCR procedures it was found that LNCaP and DU-145 cells and not the PC-3 cells have HPG-1 expression, with LNCaP cells having approximately 2-3-fold higher levels of HPG-1 mRNA transcripts compared with DU-145 cells. In vitro culture of LNCaP cell with antisense and not the sense oligonucleotide decreased the HPG-1 mRNA levels and inhibited the cell growth in a concentration-dependent manner; at 72 h there was an 86% inhibition of cell growth. HPG-1 mRNA expression in LNCaP cells was found to be responsive to androgen. Thus, the novel androgen-responsive HPG-1, which has prostate-specific expression and seems to be involved in carcinogenesis, may have applications in the specific diagnosis and treatment of prostate cancer.