The TP53 gene is the most common gene mutated in cancer, occurring in over 50% of cases. It normally acts as a tumor suppressor, regulating cell growth and DNA repair. However, when mutated, it leads to uncontrolled cell division and growth in cells with damaged DNA. So Dr. Mendeson, what are the genetic mutations that are involved with cancer? The gene that is most commonly mutated is the TP53 gene, which happens in more than 50% of all cancers. The TP53 gene functions as a tumor suppressor gene, controlling cell growth and division, and signals to other genes for DNA repair assistance, and also triggers cell death if damaged DNA cannot be repaired. Once mutated, it causes cells with damaged DNA to grow and divide out of control.