Mechanistic investigation of synergistic interaction of tocopherol succinate with a quinoline-based inhibitor of mammalian target of rapamycin.

ABSTRACT

OBJECTIVES: Cancer monotherapy is associated with various limitations; therefore, combination chemotherapy is widely explored for optimum drug efficacy. In this study, 4-(N-Phenyl-N'-substituted benzenesulfonyl)-6-(4-hydroxyphenyl) quinoline-based mammalian target of rapamycin (mTOR) inhibitor (IIIM-4Q) was investigated in combination with tocopherol succinate (TOS), and the mechanism of cytotoxicity was elucidated. METHODS: The cytotoxic potential of IIIM-4Q and TOS was evaluated in five cell lines. Further, to understand the mechanism of cytotoxicity of IIIM-4Q, TOS and their combination, various studies including morphological analysis using scanning electron microscopy and 6-diamidino-2-phenylindole (DAPI) staining, estimation of reactive oxygen species (ROS) level, measurement of mitochondrial membrane potential (MMP), in-vitro cell migration assay, Western blotting and staining with acridine orange (AO) for autophagy detection were performed. KEY FINDINGS: Investigated combination was synergistic in nature and exhibited greater oxidative stress and mitochondrial dysfunction in pancreatic cancer cells. The migration potential of MIA PaCa-2 cells was significantly mitigated under the influence of this combination, and morphological changes such as chromatin condensation and nuclear blebbing were observed. Also, poly (adenosine diphosphate-ribose) polymerase cleavage and caspase-3 activation were observed in IIIM-4Q and TOS combination-treated cells. CONCLUSIONS: The investigated combination synergistically inhibited proliferation of MIA PaCa-2 cells through simultaneous induction of autophagy followed by apoptosis, and this combination demonstrated potential for further translational studies.