Androgen regulation of soluble guanylyl cyclaseα1 mediates prostate cancer cell proliferation

Abstract

The growth and progression of prostate cancer are dependent on androgens and androgen receptor (AR), which act by modulating gene expression. Utilizing a gene microarray approach, we have identified the a1-subunit gene of soluble guanylyl cyclase (sGC) as a novel androgen-regulated gene. A heterodimeric cytoplasmic protein composed of one a and one b subunit, sGC mediates the widespread cellular effects of nitric oxide (NO). We report here that, in prostate cancer cells, androgens stimulate the expression of sGCa1. A cloned human sGCa1 promoter is activated by androgen in an AR-dependent manner, suggesting that sGCa1 may be a direct AR target gene. Disruption of sGCa1 expression severely compromises the growth of both androgendependent and androgen-independent AR-positive prostate cancer cells. Overexpression of sGCa1 alone is sufficient for stimulating prostate cancer cell proliferation. Interestingly, the major growth effect of sGCa1 is independent of NO and cyclic guanosine monophosphate, a major mediator of the sGC enzyme. These data strongly suggest that sGCa1 acts in prostate cancer via a novel pathway that does not depend on sGCb1. Tissue studies show that sGCa1 expression is significantly elevated in advanced prostate cancer. Thus, sGCa1 may be an important mediator of the procarcinogenic effects of androgens.

Expression of a hyperactive androgen receptor leads to androgen-independent growth of prostate cancer cells

“…5C), and western blotting (Fig. 5D), is androgen independent in V94, V134, and V149 cells, mimicking what has been observed in the other androgen-independent prostate cancer cells (Cai et al 2007a;Cai & Shemshedini unpublished results). This androgen-independent expression is not a common feature of all androgenregulated genes, since TMPRSS2 (Lin et al 1999) is androgen induced in both the C14 and VP16-AR cell lines (Fig.…”

“…Stable expression of VP16-AR in prostate cancer cells yielded androgen-independent cell proliferation. Importantly, this androgen-independent growth correlated with androgen-independent expression of soluble guanylyl cyclasea1 (sGCa1), an AR-regulated gene that has been previously implicated in hormone-refractory prostate cancer cell growth (Cai et al 2007a). These data show that mechanisms that elevate AR transcriptional activity can lead to hormone-refractory growth of prostate cancer cells and suggest that androgen-independent expression of sGCa1, and perhaps other AR-regulated genes, may be responsible for the cell growth.…”

“…Since our previous data indicate that sGCa1 is important in the growth of both androgen-dependent and androgen-independent LNCaP cells (Cai et al 2007a), we first measured sGCa1 expression in our VP16-AR-expressing cells. Interestingly, the expression of sGCa1, as measured by semi-quantitative RT-PCR ( Fig.…”

“…In the case of Casodex treatment, 10 mM Casodex were added together with ethanol or R1881. Note that the cells with siRNA transfection were treated with R1881, 24 h after transfection, as described previously (Cai et al 2007a). Fifty nanomolar of control or sGCa1 siRNA were used (Cai et al 2007a).…”

“…For all transfection experiments, cells were transfected with 2 mg pCH110 and enough pTL1 to bring the final plasmid amount to 10 mg per dish (Chen et al 2006b). Whole cell extracts were prepared and subjected to CAT (Bubulya et al 2001) or luciferase assays (Cai et al 2007a). CAT assay results were quantified using the Bio-Rad Molecular Imager FX and Quantify One software (Philadelphia, PA, USA).…”