INK4a/ARF locus is the most frequently inactivated loci in human cancer, encoding three tumour suppressors: p15, p14-ARF and p16, which play major roles in cellular senescence, a key physiological barrier restricting tumour growth. E6AP has been implicated in HPV-induced cancer but its role beyond this context remains largely unknown. We have revealed a novel function of E6AP in the regulation of stress- and oncogene-induced senescence. E6AP deficient cells bypass senescence and display accelerated tumourigenesis in transplanted mice. This impairment was correlated with a reduced expression of the tumour suppressors encoded by the INK4a/ARF and attenuated nucleolar localization of ARF. In a search for the underlying mechanism we found that E6AP inhibits E2F1-dependent activation of Cdc6, a known repressor of the INK4/ARF. To apply our finding to a human cancer we decided to examine non small cell lung cancer (NSCLC), in which the p16 gene is frequently silenced. Notably, elevated levels of Cdc6 were linked to aggressive disease and poor clinical outcome in NSCLC patients. Interestingly, we found that low levels of E6AP and p16 inversely correlate with elevated Cdc6 in NSCLC cell lines, and in a subset of resected patient samples. Importantly, reconstitution of E6AP in NSCLC cells, using lentiviral inducible system, resulted in the reduction of Cdc6 levels accompanied by restoration of p16-mediated senescence and significantly delayed tumour growth in a xenograft mouse model. These observations support the role of E6AP-Cdc6 axis in silencing of p16 in lung carcinogenesis. Consistently, patients with E6AP-low/Cdc6-high/p16-low had very low frequency of p16 methylation and had the worst overall survival. Our study explores a new pathway to the silencing of the INK4a/ARF, and provides a rational for a novel therapeutic approach.