Sestrins in Carcinogenesis-The Firefighters That Sometimes Stoke the Fire

Sestrins (SESN1-3) are a family of stress-responsive proteins that regulate cellular metabolism and redox balance, both of which are frequently disrupted in cancer. As direct targets of stress-responsive transcription factors, including tumour suppressor p53, Sestrins function as leucine-dependent inhibitors of mTORC1 and potent antioxidants. Their downregulation is widely observed across multiple cancers and is associated with increased tumour growth and poor prognosis. Despite their consistent tumour-suppressive effects through mTORC1 inhibition and promotion of p53-dependent apoptosis, Sestrins exhibit a limited role in tumour initiation, which appears to be context-dependent. Their antioxidant activity reduces oxidative damage, thereby protecting against genomic instability and other cancer-promoting events. However, in certain contexts, Sestrins may promote tumour survival and progression by stimulating pro-survival pathways, such as AKT signalling through mTORC2 activation. This review examines the molecular mechanisms underlying these dual functions, with a particular focus on mTOR signalling and oxidative stress. We also discuss Sestrin expression patterns and functional outcomes in various cancer types, including lung, liver, colon, skin, prostate, and follicular lymphomas, highlighting their potential as diagnostic markers and therapeutic targets.