Many cancer therapies activate the RB and/or p53 tumour suppressors, and in doing so induce a cellular phenotype that resembles cellular senescence. These senescent cancer cells are resistant to nearly all existing cancer therapies and thus form a reservoir of cells that can fuel tumour progression and relapse. In non-cancerous cells, cellular senescence is associated with dramatic alterations in cancer cell metabolism, epigenetic profile, and kinase signalling. However, it is not clear whether these features of classical senescence are recapitulated in tumour cells that have entered. Using a variety of in vitro and in vivo approaches, we are exploring the nature of therapy-induced senescence, searching for changes in cancer cell biology that expose new therapeutic vulnerabilities.