Fatty acid channelling into triglycerides and oxylipins drives ferroptosis resistance during oncogenic BRAF-induced senescence

Abstract Oncogene-induced senescence (OIS), a cellular programme initiated by activation of oncogenic signalling, provides a barrier to transformation and is accompanied by major reprogramming of cellular metabolism. We show here that induction of OIS by BRAF V600E expression in human diploid fibroblasts led to global changes in the cellular lipidome, characterised by a strong increase in triglycerides (TG) and a marked reduction in membrane phosphoglycerides carrying polyunsaturated fatty acids (PUFA) in their acyl-chains. Induction of BRAF V600E OIS resulted in a marked resistance towards lipid peroxidation and ferroptosis. Inhibition of TG synthesis by blocking diacylglycerol O-acyltransferase 1 (DGAT1) resulted in PUFA re-distribution to membrane lipids and increased ferroptosis sensitivity of senescent cells. Inhibition of DGAT also altered the senescence-associated secretory phenotype (SASP) and enhanced the secretion of oxylipins by BRAF V600E OIS cells. Combined blockade of DGAT1-dependent TG and COX2-dependent oxylipin synthesis fully restored ferroptosis sensitivity in BRAF V600E OIS cells. Together, these findings indicate that channelling of PUFA towards TG synthesis confers protection from oxidative stress and ferroptosis during BRAF V600E OIS but also limits the production of pro-inflammatory lipid mediators, a key feature of the senescent phenotype.