Expression of receptor protein tyrosine phosphatase α mRNA in human prostate cancer cell lines

Receptor protein tyrosine phosphatase α (RPTPα) is a transmembrane protein phosphatase, and has been proposed to be involved in the differentiation of the neuronal system. In the present study, we demonstrated the expression of RPTPα mRNA in several normal human tissues. We further investigated the regulation of expression of RPTPα mRNA in epithelial cells utilizing three commercially available human prostate cancer cell lines LNCaP, PC-3 and DU145. This is because these cells exhibit different levels of differentiation, defined by the expression of a tissue-specific differentiation antigen, prostatic acid phosphatase (PAcP), and their androgen sensitivity. LNCaP cells express PAcP and are androgen-sensitive cells, while PC-3 and DU145 cells do not express PAcP and are androgen- insensitive cells. Northern blot analyses revealed that, in LNCaP cells, fetal bovine serum (FBS) and 5α-dihydrotestosterone (DHT) down-regulates RPTPα mRNA expression, similar to the effect on PAcP. Contrarily, FBS up- regulated the RPTPα mRNA level in PC-3 and DU145 cells. In LNCaP cells, sodium butyrate inhibited cell growth and up-regulated RPTPα as well as PAcP mRNA expression. Although, sodium butyrate also inhibited the growth of PC-3 and DU145 cells, the level of RPTPα mRNA was decreased in PC-3, while increased in DU145 cells. Thus, data taken together indicate that the expression of RPTPα is apparently regulated by a similar mechanism to that of PAcP in LNCaP cells.