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

Abstract

Background: While a range of therapeutic products is available for androgen-dependent prostatic cancer, no specific intervention modality exists for androgen-independent prostatic cancer. The objective of this research was to explore whether epitopes exist on androgen-independent prostatic DU145 cancer cells, which could be susceptible to cytotoxic action of specific antibodies. Methods: Hybrid cell clones were developed by immunization of mice with DU145 cells and tested for immunoreactivity by solid phase EIA and cytotoxicity in vitro on DU145 in the presence of the complement, employing colorimetric quantitation by MTS (3- (4-, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-(4-sulfophenyl)-2H-tetrazolium). Binding and cytotoxicity studies were also carried out by flow-cytometry. Results: Of 15 stabilized clones immunoreactive with DU145 cells, one monoclonal antibody (mAb 730) manifested cytotoxicity on DU145 cells. Approximately 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-cytometry. Staining with ethidium monoazide bromide (EMA) showed that the cell binding 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-independent human prostatic cancer cell line. This antibody is devoid of classical autoantibody reactivities and does not react with normal human liver, thyroid, kidney, pancreas, and adrenal tissues, as determined by immunofluorescence. Also, it shows negative immuno-reactivity to benign glandular tissue 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.