TP53 and breast carcinoma: However, among all transitions in the probable orders of the breast cancers, TP53→BRCA2 and TP53→BRCA1 were identified as the second and fourth most frequent transitions, respectively, implying that mutations in these two genes tend to occur next to the mutation of TP53. Similarly, the transition of TP53→BRCA1was ranked as the third most frequent in the probable orders in ovarian cancer, supporting the conjecture mentioned above.