Mutations in tumor suppressor genes were observed in cancer cells with the most frequently mutated tumor suppressor gene is p53 followed by phosphatase and tensin homolog (PTEN), adenomatous polyposis coli (APC), ataxia-telangiectasia mutated (ATM), breast cancer gene2 (BRCA2), Von Hippel-Lindau (VHL), retinoblastoma (RB), cyclin-dependent kinase inhibitor 2A (CDKN2A), breast cancer gene2 (BRCA1) and Wilms tumor (WT1). The gene discussed is ATM; the disease is cancer.