Targeting the mitochondrial pathway to induce apoptosis/necrosis through ROS by a newly developed Schiff's base to overcome MDR in cancer

Multidrug resistance (MDR) in cancer, a major obstacle to successful application of cancer chemotherapy, is often characterized by over-expression of multidrug resistance-related proteins such as MRP1, P-gp or elevated glutathione (GSH) level. Efflux of drugs by functional P-gp, MRP1 and elevated GSH level can confer resistance to apoptosis induced by a range of different stimuli. Therefore, it is necessary to develop new cell death inducers with relatively lower toxicity toward non-malignant cells that can overcome MDR by induction of apoptotic or non-apoptotic cell death pathways. Herein we report the synthesis and spectroscopic characterization of a GSH depleting, redox active Schiff’s base, viz., potassium-N-(2-hydroxy-3-methoxy-benzaldehyde)-alaninate (PHMBA). Cytotoxic potential of PHMBA has been studied in doxorubicin-resistant and -sensitive T lymphoblastic leukemia cells and Ehrlich ascites carcinoma (EAC) cells. PHMBA kills both the cell types irrespective of their drug-resistance phenotype following apoptotic/necrotic pathways. Moreover, PHMBA-induced cell death is associated with oxidative stress mediated mitochondrial pathway as the H₂O₂ inhibitor PEG-Catalase abrogated PHMBA-induced apoptosis/necrosis. PHMBA induces anti-tumor activity in both doxorubicin-sensitive and -resistant EAC-tumor-bearing Swiss albino mice. The non-toxicity of PHMBA was also confirmed through cytotoxicity studies on normal cell lines like PBMC, NIH3T3 and Chang Liver. To summarise, our data provide compelling rationale for future clinical use of this redox active Schiff’s base in treatment of cancer patients irrespective of their drug-resistance status.