– The protein p53, often called the ‘guardian of the genome,’ is a transcription factor that is activated in response to cellular stress (low oxygen levels, heat shock, DNA damage, etc.) and acts to prevent further proliferation of the stressed cell by promoting cell cycle arrest or apoptosis. Its role as a tumor suppressor is evident by the observation that approximately 50% of human tumors have mutated or non-functional p53. PK7242 is an inducer of reactivation of mutant p53 in cancer cells. In cancer cells carrying the Y220C mutant, PK7242 binds to the p53-Y220C core domain and induces growth inhibition, cell-cycle arrest, and apoptosis.