Spectrum of cell-cycle kinetics of alkylating agent adolezesin in gynecological cancer cell lines: correlation with drug-induced cytotoxicity

Adolezesin is an analog of CC-1065. These compounds are among the most potent alkylating agents known to date. Currently Adolezesin is undergoing phase I clinical trials at several Cancer centers in the USA. While the cytotoxic effects of Adolezesin have been addressed elsewhere, its effects on cell-cycle kinetics have not been reported. Flow cytometry was performed on five human gynecological Cancer cell lines: AN3, AE7, BG1, HEC1A, and SKUT1B. Exposure to Adolezesin (U73975, Upjohn Co.) was done at near confluency at 0, 0.1, 0.2, 0.5, 1 and 5x, with x = 10 pg/ml as reference concentration, for 90 min. Cell samples were taken by trypsinization at 0, 24, 48, 72, 96, and 168 h for flow cytometry. The ATP chemosensitivity assays were performed on the above cell lines to establish dose/response curves. Flow-cytometric analyses revealed that there was a spectrum of cell-cycle perturbations, which included biphasic S and G2 blocks, reverse dose-dependent G2 blocks, and a sequential relationship of S and G2 blocks. This study demonstrated that the cell kinetic response to Adolezesin depended on several variables such as cell lines, drug sensitivity, concentrations, and sampling time. Because of this multivariable dependence and the lack of correlation with cytotoxicity, it would be difficult to use cell kinetic pertubations to predict chemotherapeutic response.