Thioridazine induce phospholipid accumulation and necroptosis in breast cancer cells

An antipsychotic drug, Thioridazine has been shown to inhibit a broad spectrum of cancer cells. However, its molecular mechanism is still not well understood. In the present study, we have shown that thioridazine induces cytostatic effects in both parental and tamoxifen-resistant cancer cells through cell viability, cell count, caspase activation, cell cycle analysis and enhanced p21 levels. Further, using the pharmacometabolomics approach, we identified that thioridazine induces phospholipids accumulation in breast cancer cells. We proved that thioridazine induces only phospholipids accumulation and not neutral lipids in cells by using lipid-specific fluorescent quantification and image analysis. The accumulation of phospholipid induces necroptosis, which was assessed by propidium iodide uptake assay. Thioridazine activates RIP1 and RIP3 signalling and subsequent translocation of pore-forming MLKL to the plasma membrane to initiate necroptosis induction. The MLKL-induced membrane pores were confirmed using a scanning electron microscope cell surface visualization. Further, thioridazine co-treatment enhances the efficacy of tamoxifen in resistant breast cancer cells potentiating its usefulness for combinatorial treatment