Lipotoxicity,caused by intracellular lipid accumulation,accelerates the degenerative process of cellular senescence,which has implications in cancer development and therapy.Previously,camitine palmi-toyltransferase 1C (CPT1C),a mitochondrial enzyme that catalyzes carnitinylation of fatty acids,was found to be a critical regulator of cancer cell senescence.However,whether loss of CPT1C could induce senescence as a result of lipotoxicity remains unknown.An LC/MS-based lipidomic analysis of PANC-1,MDA-MB-231,HCT-116 and A549 cancer cells was conducted after siRNA depletion of CPT1C.Cellular lipotoxicity was further confirmed by lipotoxicity assays.Significant changes were found in the lipidome of CPT1 C-depleted cells,including major alterations in fatty acid,diacylglycerol,triacylglycerol,oxidative lipids,cardiolipin,phosphatidylglycerol,phosphatidylcholine/phosphatidylethanolamine ratio and sphingomyelin.This was coincident with changes in expressions of mRNAs involved in lipogenesis.Histological and biochemical analyses revealed higher lipid accumulation and increased malondialde-hyde and reactive oxygen species,signatures of lipid peroxidation and oxidative stress.Reduction of ATP synthesis,loss of mitochondrial transmembrane potential and down-regulation of expression of mito-chondriogenesis gene mRNAs indicated mitochondrial dysfunction induced by lipotoxicity,which could further result in cellular senescence.Taken together,this study demonstrated CPT1C plays a critical role in the regulation of cancer cell lipotoxicity and cell senescence,suggesting that inhibition of CPT1C may serve as a new therapeutic strategy through induction of tumor lipotoxicity and senescence.