Enhancement of the in vitro cytotoxicity of bouvardin by verapamil alone and combined with hyperthermia in Sarcoma 180 and Ehrlich ascites carcinoma cells.

The cytotoxic effect of bouvardin (BVD) a protein synthesis inhibitor was studied separately and in combination with verapamil (VRP), a vasodilator and hyperthermia (43 degrees C) against Sarcoma 180 (S 180) and Ehrlich ascites carcinoma (EAC) tumour cells in vitro. S 180 cells exhibited natural resistance to hyperthermia and BVD, whereas EAC tumour cells were found to be sensitive. VRP alone did not show cytotoxicity to either tumour cells. A combination of BVD and VRP at an elevated temperature resulted in a greater cell kill in the EAC tumour cell line whereas the natural resistance of S 180 tumour cells to the drug BVD and hyperthermia was circumvented by combination with VRP. Combination of BVD, hyperthermia and VRP resulted in greater cell kill, compared to separate treatment with the single agents. The cytotoxicity was evaluated by comparing the inhibition of incorporation of 3H-thymidine in treated cells to that in untreated cells.