Androgen concentrations in expressed prostatic secretions: no correlation with tissue levels

Androgens transduce the G alphas-mediated activation of protein kinase A in prostate cells

Androgens regulate the development and function of male reproductive organs and play a crucial role in the onset and progression of prostate cancer. Androgen action is primarily mediated through the nuclear androgen receptor (AR) which acts as a ligand-dependent transcription factor. This mode of androgen action takes hours to manifest and is called the genomic pathway. The androgen-mediated genomic responses require activity of cyclic AMP (cAMP)-dependent protein kinase (PKA). Androgens also act through nongenomic pathways in certain cell types to evoke rapid responses (manifested in minutes) that are mediated through changes in ion currents and second messengers. Here, we show that androgen causes the rapid and cAMP-dependent activation of PKA in prostate cells. The androgen-induced PKA activation is not inhibited by nuclear AR antagonist bicalutamide and can be observed in cells that do not express nuclear AR gene. Reduction of G alphas expression with siRNA attenuates the androgen-mediated activation of PKA, which is required for the androgen-induced prostate cell proliferation. We conclude that androgen actively evokes a nongenomic signaling pathway to activate PKA that is needed for the genomic functioning of nuclear AR. The inhibition of PKA activation, together with standard AR-targeted therapies, may be more efficacious for treatment of patients with prostate cancer.

Androgen receptor protein expression in prostatic tissues in Black and Caucasian men

BACKGROUND

CaP has a higher incidence and mortality in Black men. We hypothesized that subpopulation differences in AR expression may contribute to this phenomenon.

METHOD

AR immunostaining was compared in epithelium and PES of normal, BPH, and CaP tissues from Black African men and UK Caucasian men.

RESULTS

AR expression was similar in normal prostatic epithelium of both groups, but was higher in BPH and CaP epithelium of Black than Caucasian men (P </= 0.0001). Also, AR expression in PES was higher in Caucasian than Black men in normal/atrophic and benign hyperplastic tissues, but there was a similar significant loss of AR expression in PES of CaP tissues of both groups (normal and BPH stroma versus CaP stroma (P </= 0.0001).

CONCLUSIONS

Variations in AR expression between subpopulations may contribute to the phenotypic differences of prostatic diseases in Black and Caucasian men.

Steroid hormones and cancer: IV. Prostate cancer

Over many years, a great deal of attention has focused on the growth regulatory effects of androgens in prostate cells. This, has also prompted widespread interest in the role of these steroid hormones in prostate cancer pathogenesis. Even so, no-one has so far been able to identify the exact relationship between androgenic hormone levels and the risk of these diseases though differences in hormonal patterns amongst racial ethnic groups has been reported to reflect diversities in prostate cancer incidence. One of the difficulties stems from the fact that serum hormone levels do not reflect the changes observed in prostate tissue androgen concentrations as the normal prostate progresses to a disease state. In this article efforts will be directed towards understanding some of the intra-prostate-specific mechanisms responsible for activating and/or repressing the androgen-dependent gene network associated with the gradual transition to a hormone refractive neoplastic state.

Review of the role of androgenic hormones in the epidemiology of benign prostatic hyperplasia and prostate cancer

OBJECTIVE

Examine current knowledge and concepts on the role of androgenic hormones in the epidemiology of benign prostatic hyperplasia (BPH) and prostate cancer (PCa).

METHODS

Review of the clinical and scientific literature on normal androgen physiology, hormonal physiology of BPH and PCa tissue, serum hormone levels in patients with BPH or PCa, and the correlation between serum and tissue androgenic hormones.

RESULTS

BPH and PCa are enormous clinical problems for our health care system; profound changes in the clinical aspects of these diseases are evident in recent years. Early identification or prevention are realistic goals; identification of higher risk groups would be extremely valuable. Androgen stimulation of the prostate is likely to be important in the promotion of BPH or PCa. Tissue hormone measurements have not identified substantial differences in hormone levels, but precise pathologic control of the tissue examined is suspect. Examinations of serum hormone levels in disease states have produced conflicting results, but the presence or absence of BPH or PCa was often based on imprecise clinical observations, making interpretation difficult. There are minimal data confirming that the serum hormones measured previously actually reflect intraprostatic tissue activity.

CONCLUSIONS

The value of serum hormone measurements to identify higher risk groups for BPH or PCa is an area of continuing uncertainty because of substantial flaws in the design of many previous studies based on a failure both to define the presence or absence of BPH or PCa precisely in patients studied and measure the appropriate androgen metabolites. Similarly, it is not possible reliably to implicate differences in androgenic stimulation as a cause for racial differences in PCa. The ability of serum hormone levels to correlate with prostatic tissue androgenic stimulation has not been evaluated. Additional research in the relationships between androgenic stimulation and the development of clinically significant BPH or PCa is needed.