diethyl-maleate and Carcinoma--Transitional-Cell

This study was undertaken to investigate the intracellular induction of reactive oxygen species (ROS) by cis-dichlorodiammineplatinum (CDDP) and the augmentation of their cytotoxicity in bladder cancer cells (KU7) by enhancement of ROS generation by the glutathione (GSH) depletors buthionine sulphoximine (BSO) and diethylmaleate (DEM). CDDP-induced cytotoxicity in KU7 cells and its modulation by GSH depletors were determined using spectrophotometric measurement with crystal violet staining. The effects of GSH depletors on intracellular GSH levels were confirmed using the GSH reductase-DTNB recycling method. Intracellular ROS generation induced by CDDP with or without GSH depletors was estimated from the amount of intracellular dichlorofluorescein (DCF), an oxidized product of dichlorofluorescein (DCFH), which was measured with an anchored cell analysis and sorting system. The cytotoxic effects of CDDP (IC50 15.0 +/- 2.5 microM) were significantly enhanced by BSO (IC50 9.3 +/- 2.6 microM, P < 0.01) and DEM (IC50 10.3 +/- 0.3 microM, P <0.01). BSO and DEM produced a significant depletion in intracellular GSH levels (9.6 +/- 0.4 nmol 10(-6) cells, 17.9 +/- 1.0 nmol 10(-6) cells) compared with the controls (30.5 +/- 0.6 nmol 10(-6) cells). Intracellular DCF production in KU7 cells treated with CDDP (1.35 +/- 0.33 microM) was significantly enhanced by the addition of BSO (4.43 +/- 0.33 microM) or DEM (3.12 +/- 0.22 microM) at 150 min. These results suggest that ROS may play a substantial role in CDDP-induced cytotoxicity and that GSH depletors augment its cytotoxicity through an enhancement of ROS generation in bladder cancer cells.

Topics: Antimetabolites; Antineoplastic Agents; Buthionine Sulfoximine; Carcinoma, Transitional Cell; Cell Survival; Cisplatin; Dose-Response Relationship, Drug; Fluoresceins; Glutathione; Humans; Hydrogen Peroxide; Maleates; Reactive Oxygen Species; Tumor Cells, Cultured; Urinary Bladder Neoplasms

The effect of pretreating the C3H/He mouse MBT-2 tumor with diethyl maleate (DEM), buthionine-S R-sulfoximine (BSO), or misonidazole (MISO) before administration of cyclophosphamide (CTX) was studied with the use of tumor volume-doubling time delay as an endpoint. The kinetics of glutathione (GSH) depletion and regeneration in the tumor and in the host liver were determined after treatment with the thiol-depleting agents. CTX was administered at appropriate time points. MISO was the most effective chemosensitizer at a time point at which tumor GSH content was 80-85% of the control value. Both BSO and DEM were chemosensitizers in relation to the degree they had reduced tumor GSH levels. This chemosensitization was significant at 50% GSH reduction. By combining MISO and BSO at doses lower than previously used for each agent alone, highly effective sensitization of subsequent CTX was obtained.

Topics: Animals; Buthionine Sulfoximine; Carcinoma, Transitional Cell; Cyclophosphamide; Drug Combinations; Drug Resistance; Female; Glutathione; Liver; Maleates; Methionine Sulfoximine; Mice; Mice, Inbred C3H; Misonidazole; Neoplasm Transplantation; Urinary Bladder Neoplasms