Changes of protein expression in prostate cancer having lost its androgen sensitivity.

Abstract

OBJECTIVE: The majority of prostate cancers require androgen hormones for growth, and androgen ablation is an important part of the systemic treatment of advanced prostate cancer. Nevertheless, most of these cancers eventually relapse as they become less sensitive to androgen ablation and anti-androgen treatment. Elucidating the molecular events that are responsible for the conversion of androgen-sensitive cancers to androgen-refractory tumors may reveal new therapeutic opportunities. METHODS: In the present study, we investigated nine androgen-sensitive and nine androgen-refractory prostate cancer samples to evaluate the expression levels of 10 selected proteins that have been implicated in oncogenesis and cancer progression. RESULTS: Our immunohistochemical data show that three of the investigated proteins (i.e., minichromosome maintenance-2, methylguanine-DNA methyltransferase, and androgen receptor) are expressed at significantly different levels in the androgen-refractory cancer samples than in the androgen-sensitive tumors, whereas the expression levels of the seven other studied proteins (i.e., beta-catenin, p27, p21, p16, Ki67, hypoxia-inducible factor 1 alpha, and geminin) are not significantly different regarding the two groups. CONCLUSIONS: Our data suggest that the increased expression of minichromosome maintenance-2 and decreased expression of methylguanine-DNA methyltransferase related to androgen receptor are indicative of the androgen-refractory stage in prostate cancer. Further studies are required to determine whether these expression changes play a causative role in the transition of androgen-sensitive to androgen-refractory prostate cancer.