Three-dimensional spheroid cultures of human prostate cancer cell lines

BACKGROUND Many of the available human prostate cancer (PC) cell lines have lost androgen sensitivity and no longer secrete prostate‐specific proteins after serial culturing in cell monolayers. Three‐dimensional spheroid cultures have been found to better mimic the in vivo phenotypes of several nonprostatic cell lines. METHODS We analyzed seven PC cell lines to determine if spheroid culturing results in greater sensitivity to androgens and 1α,25(OH)2 vitamin D3 (1,25(OH)2 D3) with regards to their growth, differentiation, and apoptotic potential. RESULTS Only PC‐3 cells showed greater sensitivity to the growth‐inhibitory effects of 1,25(OH)2 D3, while ALVA‐31 showed a diminished response. The regulation of prostate‐specific antigen and prostate‐specific acid phosphatase remained unchanged. However, these studies provided several unique findings not observed in cell monolayers. First, three basic spheroid morphologies were observed with varying degrees of intercellular adhesions. Secondly, the cell lines that formed the tightest spheroids consistently grew at the slowest rates, regardless of their growth rate in monolayers. Lastly, 1,25(OH)2 D3 treatment of ALVA‐31 and PPC‐1 spheroids greatly reduced intercellular adhesions, and rendered ALVA‐31 spheroids resistant to apoptotic induction by Fas ligand expressed via a recombinant adenoviral construct. CONCLUSIONS Our results suggest that spheroid cultures of human PC cells may provide unique insights regarding cell adhesion and apoptotic potential that are diminished or absent in monolayer cultures. Prostate 41:154–165, 1999. © 1999 Wiley‐Liss, Inc.