Oncolytic viruses show an intrinsic selectivity towards tumour cells, which is mostly due to malignant characteristics such as altered metabolism, defects in anti-viral responses, the loss of p53 or p16 tumour suppressors and the activation of aberrant oncogenic signalling pathways, including RAS–MEK–ERK/MAPK and Wnt [188, 190, 191]. The gene discussed is CDKN2A; the disease is neoplasm.