Anti-oncogenes (also tumour suppressor genes) normally regulate cell growth and division acting as inhibitors. They can stem uncontrolled divisions that takes place in cancer. Thus when improperly function they cause cancer. There are several characterised genes that can be found in mutant form in different tumours. These are for example Rb gene, first discovered in eye cancer retinoblastoma, p53 (mutant p53 gene is found in many cancers) BRCA1 and BRCA2 (connected with breast cancers) genes.