Enzymatic oxidation products of spermine induce greater cytotoxic effects on human multidrug-resistant colon carcinoma cells (LoVo) than on their wild-type counterparts.

The occurrence of resistance to cytotoxic agents in tumor cells, associated with several phenotypic alterations, is one of the major obstacles to successful anticancer chemotherapy. A new strategy to overcome MDR of human cancer cells was studied, using BSAO, which generates cytotoxic products from spermine, H(2)O(2) and aldehyde(s). The involvement of these products in causing cytotoxicity was investigated in both drug-sensitive (LoVo WT) and drug-resistant (LoVo DX) colon adenocarcinoma cells. Evaluation of clonogenic cell survival showed that LoVo DX cells are more sensitive than LoVo WT cells. Fluorometric assay and treatments performed in the presence of catalase demonstrated that the cytotoxicity was due mainly to the presence of H(2)O(2). Cytotoxicity was eliminated in the presence of both catalase and ALDH. Transmission electron microscopic observations showed more pronounced mitochondrial modifications in drug-resistant than in drug-sensitive cells. Mitochondrial functionality studies performed by flow cytometry after JC-1 labeling revealed basal hyperpolarization of the mitochondrial membrane in LoVo DX cells. After treatment with BSAO and spermine, earlier and higher mitochondrial membrane depolarization was found in LoVo DX cells than in drug-sensitive cells. In addition, higher basal ROS production in LoVo DX cells than in drug-sensitive cells was detected by flow-cytometric analysis, suggesting increased mitochondrial activity in drug-resistant cells. Our results support the hypothesis that mitochondrial functionality affects the sensitivity of cells to the cytotoxic enzymatic oxidation products of spermine, which might be promising anticancer agents, mainly against drug-resistant tumor cells.