XIAP and neoplasm: In vitro studies have shown that metformin administration enhances the sensitivity of TNBC cell lines to TRAIL receptor agonists.121 TRAIL agonists (TNF-related apoptosis-inducing ligand (TRAIL) are tumour-specific inducers of apoptosis that have strong anti-tumour effects in preclinical models.122 Metformin reduces the levels of XIAP, a negative regulator of TRAIL-induced apoptosis, and provides evidence supporting the combined administration of these drugs.