Effects and possible anti-tumor immunity of electrochemotherapy with bleomycin on human colon cancer xenografts in nude mice

AIM: To evaluate the anti-tumor effects and possible involvement of anti-tumor immunity of electrochemotherapy (ECT) employing electroporation and bleomycin in human colon cancer xenografts in nude mice, and to establish the experimental basis for clinical application of ECT. METHODS: Forty nude mice, inoculated subcutaneously human colon cancer cell line LoVo for 3 wk, were allocated randomly into four groups: B+E+ (ECT), B+E-(administration of bleomycin alone), B-E+(administration of electric pulses alone), and B-E-(no treatment). Tumor volumes were measured daily. The animals were killed on the 7^th d, the weights of xenografts were measured, and histologies of tumors were evaluated. Cytotoxicity of spleen natural killer (NK) and lymphokine-activated killer (LAK) cells was then assessed by lactic dehydrogenase release assay. RESULTS: The mean tumor volume of group B+E+was statistically different from the other three groups after the treatment (F=36.80, P