Similar to the embryonic lethal effects in BRCA1/2, homozygous variation in BRCAness genes was not common across different cancer types although homozygous deletions in some BRCAness genes (FANCD2, PTEN, TP53, BRCA2) could be present [45]; (3) promoter methylation was common in many BRCAness genes and caused alterative expression [46]. This evidence concerns the gene TP53 and cancer.