Date of Award

5-1-2010

Degree Type

Dissertation

University or Center

Clark Atlanta University(CAU)

School

School of Arts and Sciences

Degree Name

Ph.D.

Department

Biology

First Advisor

Dr. Shafiq A. Khan

Second Advisor

Dr. Jaideep Chaudhary

Third Advisor

Dr. Godwin Ananaba

Abstract

The proliferation and differentiation of normal prostate epithelial cells depend upon the action of the androgens, testosterone and dihydrotestosterone. Prostate cancer cells retain the ability to respond to androgens in the initial stages of cancer development but progressively become independent of exogenous androgens in advanced stages of the disease while maintaining the expression of functional androgen receptor (AR). We hypothesized that prostate cancer cells in the advanced stages of the disease acquire capability to synthesize androgens which activate AR in an intracrine manner. To test this hypothesis, we determined the expression of proteins and enzymes involved in cholesterol uptake, transport and its conversion into testosterone in androgen-dependent and androgen-independent prostate cancer cell lines. Established androgen independent prostate cancer cell lines, PC3 and DU145 cells, expressed mRNA and proteins for scavenger receptor type B 1 (SRB 1), steroidogenic acute regulatory (StAR) protein, metastatic lymph node 64 (MLN64), cytochrome P450 cholesterol side chain cleavage (CYP11), and other enzymes involved in androgen biosynthesis. Expression of all these proteins and enzymes was significantly higher in the androgen-independent derivative of LNCaP prostate cancer cells (C81) than in the androgen-dependent cell line (C33). In serum free cultures, the androgen independent cell line C81 secreted ~5 fold higher testosterone than C33 as determined in the conditioned media by specific immunoassays. These cells also converted radioactive cholesterol into testosterone which was identified by thin layer chromatography. To evaluate the effects of endogenous production of testosterone on the survival and growth of prostate cancer cells, C81 cells were treated with either aminoglutethimide to prevent conversion of cholesterol to pregnenolone or the AR antagonist, bicalutamide. Our results demonstrated growth inhibition ofC8l cells and a reduction in expression of the AR regulated genes, PSA and TMPRSS2 in aminoglutethimide and bicalutaniide treated cells which were reversed by exogenous androgens. These results indicate that prostate cancer cells in advanced stages of the disease synthesize androgens from cholesterol. These androgens activate AR in an intracrine maimer to regulate cell survival and proliferation. The ability of the prostate to synthesize androgens may be associated with progression to castration resistant prostate cancer and possibly represents a therapeutic target for advanced disease.