TNFRSF1A and neoplasm: In contrast, the extrinsic apoptosis pathway, activated principally by NK and cytotoxic T lymphocyte populations, involves death-inducing TNF-family ligands TNFα, FASL and TRAIL, which bind TNFR, FAS and DR4/5 TRIAL death receptors, induced on the surface of damaged cells by activated tumour suppressors, such as TP53.