Induction of apoptosis and altered nuclear/cytoplasmic distribution of the androgen receptor and prostate-specific antigen by 1alpha,25-dihydroxyvitamin D3 in androgen-responsive LNCaP cells.

In addition to suppressing prostate cell growth, vitamin D also up-regulates the expression of androgen receptor (AR) and prostate-specific antigen (PSA). To study the mechanism involved in the control of these proteins, LNCaP cells were treated with 10 nM 1alpha,25-dihydroxyvitamin D3 and separated into cytosol and nuclear fractions. AR and PSA were analyzed by western blot analysis. A second approach involved incubating control and treated cells with [3H]R1881, fractionating the cells into the cytosolic and nuclear components, and quantifying the amount of radioactivity associated with the respective fractions. Alternatively, immunohistochemical assays were performed by staining cells with cognate antibodies for AR and PSA. Both biochemical and immunohistochemical analyses show proportionately greater increased presence of AR in the nucleus, accompanied by relatively reduced AR in the cytosol, following treatment of LNCaP cells with vitamin D3. Surprisingly, PSA was found to be present in the nuclear fraction in both control and treated cells. These results suggest that vitamin D3 promotes the translocation of AR from the cytosol to the nucleus. The presence of PSA in the nucleus of LNCaP cells raises the possibility of an autogenous mode of control of PSA gene expression.