Tumour cells can become resistant to the antiproliferative and proapoptotic effects of T-cell effector moleculesthrough mutational or epigenetic inactivation, and enhanced negative feedback regulation of signal transductionpathways. IFN=interferon. IFNGR=interferon-γ receptor. JAK=Janus kinase. STAT=signal transducer and activator oftranscription. SOCS1=suppressor of cytokine signalling 1. PIAS4=protein inhibitor of activated STAT4.Fas=apoptosis antigen 1. FasL=ligand for FAS receptor