TP53 and neoplasm: This report investigates the antiproliferative and cytotoxic effect of rML alone and in combination with IR in a murine genetically defined p53+/+ and p53−/− tumour cell system, which has been previously used to determine p53-dependent apoptosis induction (Lowe et al, 1993b,1994), and in human p53-mutated colon adenocarcinoma cells.