Primary prostate cancer cultures are models for androgen-independent transit amplifying cells

Numerous efforts exist for developing primary prostate cancer cultures for studying the biology of this tumor entity and for evaluation of the effectiveness of novel therapies. However, there is doubt if cultures that represent the fully differentiated phenotype can be established. The aim of the present study was to characterize primary outgrowing prostate epithelial cells due to their basal or luminal characteristics and their potential for serving as androgen-responsible model. From fresh prostate cancer radical prostatectomy specimens, pieces of ≈2-4 mm diameter were placed on top of transwell culture chambers, which were coated with matrigel and cultured in prostate epithelial selection medium with 10% fetal calf serum. The monolayer of outgrowing cells was incubated with a physiological concentration of 1 nM dihydrotestosterone (DHT). One group was additionally cultivated without DHT and another group was treated with the 5-α-reductase-inbitors MK-368 and MK-905. From the monolayer of the outgrowing cells, RNA was isolated and the expression of androgen receptor (AR), prostate-specific antigen (PSA), Kallikrein 2 (KlK2), prostate-specific membrane antigen (PSMA), and prostate stem cell antigen (PSCA), cytokeratin (CK)5, and CK18 was determined by realtime quantitative PCR. The outgrowing cells from the prostate cancer tissue pieces could be characterized as epithelial cells with basal and transit amplifying characteristics as shown by co-expression of CK5 and CK18. In all cultures, a very low expression of the luminal cell marker genes AR, PSA and KLK2 was measured. The levels of PSCA were clearly higher with a broad variation. Upon cultivation without DHT or treatment with α-reductase inhibitors no regulation of AR, PSA and KlK2 was found. Due to the co-expression of basal and luminal marker genes, primary prostate cancer cultures can be charaterized as models of transit amplifying cells of the prostatic epithelium. They do not represent the differentiated secretory androgen-responsive cell phenotype.