In this study, we investigated androgen metabolism in two different human prostate cancer cell lines, the androgen-responsive LNCaP cells and the nonresponsive PC3 cells. Following 24-h and 72-h incubation with either testosterone (T) or androstenedione (Ad) used as precursor, divergent patterns and rates of androgen metabolism were observed. Given the recent interest in the multiple uses of embryonic and adult stem cells for basic and applied research, we compared the expression of three presumptive stem cell markers (Oct-4, SUZ-12, and Cripto-1), along with connexin 43 (Cx43), Cx32, and androgen receptor (AR), used as cell differentiation gene markers. In anchorage-independent cell growth conditions, the expression levels of candidate markers of cancer stem cells initially increased (days 2-4) but drastically fell thereafter (day 6) in both cell lines. Results of immunocytochemical assay (ICA) largely confirmed those obtained by RT-PCR. Interestingly, both symmetrical and asymmetrical cell divisions were revealed in PC3 cells using Oct-4 immunostaining. Our data suggest that both androgen-responsive and androgen-nonresponsive prostate tumor cell lines contain a presumptive cancer stem cell population that can be identified using a panel of selected gene markers, including Oct-4, SUZ-12, and Cripto-1.