For more than 70 years, it has been believed that a severe reduction of serum androgen levels caused regression of prostate cancer (PCa) and that increasing androgen levels enhanced growth of PCa. However, numerous recent studies have questioned this traditional belief. In our study, LNCaP and MDA PCa 2b PCa cells were treated with various levels of androgens for 10 or 20 days, and the cell growth was measured with crystal violet mitogenic assay. The results indicated that the effect of androgens on the proliferation of PCa cells occurs in a biphasic pattern, with the androgen levels promoting optimal cell growth at approximately 0.23 ng ml−1 for LNCaP cells and between 1 and 2 ng ml−1 for MDA PCa 2b cells. Both of the optimal androgen levels are within the adult men's physiological low range (<2.4 ng ml−1 ). At lower concentrations than the optimal androgen level, increasing androgen concentration promoted the proliferation of PCa cells. However, at the higher concentrations, increasing androgen concentration resulted in a dose-dependent proliferative inhibition. We conclude that physiologically normal levels of androgen inhibit the proliferation of PCa cells in vitro. However, at very low levels androgens are essential for initial growth of PCa cells.

Keywords: androgen; proliferation; prostate cancer; testosterone

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