A monoclonal antibody cytolytic to androgen independent DU145 and PC3 human prostatic carcinoma cells

BACKGROUND. While a range of therapeutic products is available for androgen -dependent prostatic cancer, no specific intervention modality exists for a ndrogen-independent prostatic cancer. The objective of this research was to explore whether epitopes exist on androgen-independent prostatic DU145 can cer cells, which could be susceptible to cytotoxic action of specific antib odies. METHODS. Hybrid cell clones were developed by immunization of mice with DU1 45 cells and rested for immunoreactivity by solid phase EIA and cytotoxicit y in vitro on DU145 in the presence of the complement, employing colorimetr ic quantitation by MTS (3- (4-, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy phenyl)-(4-sulfophenyl). Binding and cytotoxicity studies were also carried out by flow-cytometry. RESULTS. Of 15 stabilized clones immunoreactive with DU145 cells, one monoc lonal antibody (mAb 730) manifested cytotoxicity on DU145 cells. Approximat ely 80% of cells in the DU145 cell line were susceptible to lysis with this antibody at saturating levels. This figure corresponded quantitatively to the number of cells binding with this antibody as determined by Flow-cytome try. Staining with ethidium monoazide bromide (EMA) showed that the cell bi nding the antibody was also the one killed by the antibody in the presence of the complement. MAb 730 was also cytotoxic to PC3, another androgen-inde pendent human prostatic cancer cell line. This antibody is devoid of classi cal autoantibody reactivities and does not react with normal human liver, t hyroid, kidney, pancreas, and adrenal tissues, as determined by immunofluor escence. Also, it shows negative immuno-reactivity to benign glandular tiss ue but is observed to positively react with neoplastic prostate tissue. CONCLUSIONS. Epitopes exist on androgen-independent prostatic cancer cells that are susceptible to cytolysis by monoclonal antibodies and these could be investigated for potential immunotherapy. (C) 2001 Wiley-Liss, Inc.