TP53 and Li-Fraumeni syndrome: Table 3 shows that cancer-predisposing genes that conform to the 2-hit model include NF1 (neurofibromatosis type 1), APC (familial adenomatous polyposis), BRCA1 and BRCA2 (hereditary breast and ovarian cancer) and, importantly, p53-encoding TP53 (Li-Fraumeni syndrome).