FAS-MEDIATED APOPTOSIS IN HUMAN PROSTATIC-CARCINOMA CELL-LINES

Of six prostatic carcinoma cell lines examined (ALVA31, DU145, JCA1, L NCaP, ND1, and PC3) by flow cytometric analysis, all were found to be positive for Fas antigen. Furthermore, of the prostate tissue specimen s studied (six cases), all revealed Fas expression in benign and malig nant epithelial tells. The agonistic anti-Fas monoclonal antibody (IPO -4) induced apoptosis in only two of six cell lines investigated, PC3 and ALVA31. PCR analysis indicated that all cell lines expressed norma l transmembrane and death domains of Fas antigen. Using Western blot a nalysis, we found abundant expression of p53 in the cytoplasm of two F as-resistant cell lines, DU145 and ND1, and did not find p53 in two Fa s-sensitive cell lines, PC3 and ALVA31. Western blot and PCR analysis did not show consistent differences between cell lines examined in the expression of Bcl-2, Bcl-X-L, Bcl-X-S, and Bak. In contrast, Bar prot ein was not detected in two Fas-resistant cell lines, DU145 and ND1. W e also showed that three Fas-resistant cell lines, DU145, ND1, and JCA 1, expressed CD40, whereas the two Fas-sensitive cell lines, PC3 and A LVA31, were CD40 negative. Fas-sensitive cell lines were transfected w ith the cDNA encoding CD40, and the CD40-positive transfectant became more resistant to growth inhibition mediated by treatment with TNF-alp ha and anti-Fas monoclonal antibody. Treatment with cycloheximide conv erted the phenotype of resistant cell lines from Fas resistant to Fas sensitive. Moreover, anti-Fas treatment of both resistant and sensitiv e cell lines induced rapid tyrosine phosphorylation or dephosphorylati on of multiple proteins. These results suggest that the apoptotic mach inery involved in DNA fragmentation is already in place in Fas-resista nt cell lines, and thus, Fas-mediated apoptosis could be a target for therapeutic intervention.