Our previous report showed that
methylseleninic acid (MSA) significantly decreases the expression of
androgen receptor and
prostate-specific antigen (PSA) in LNCaP cells. The present study extended the above observations by showing the universality of this phenomenon and that the inhibitory effect of MSA on
prostate cancer cell growth and
cancer-specific
biomarkers is mediated through
androgen receptor down-regulation. First, MSA decreases the expression of
androgen receptor and PSA in five human
prostate cancer cell lines (LNCaP, LAPC-4, CWR22Rv1, LNCaP-C81, and LNCaP-LN3), irrespective of their
androgen receptor genotype (wild type versus mutant) or sensitivity to
androgen-stimulated growth. Second, by using the ARE-
luciferase reporter gene assay, we found that MSA suppression of
androgen receptor transactivation is accounted for primarily by the reduction of
androgen receptor protein level. Third, MSA inhibition of five
androgen receptor-regulated genes implicated in prostate
carcinogenesis (PSA, KLK2, ABCC4, DHCR24, and GUCY1A3) is significantly attenuated by
androgen receptor overexpression. Fourth, transfection of
androgen receptor in LNCaP cells weakened noticeably the inhibitory effect of MSA on cell growth and proliferation.
Androgen receptor signaling has been documented extensively to play an important role in the development of both
androgen-dependent and -independent
prostate cancer. Our finding that MSA reduces
androgen receptor availability by blocking
androgen receptor transcription provides justification for a mechanism-driven intervention strategy in using
selenium to control
prostate cancer progression.