BRCA2 and breast cancer: Sporadic studies have reported the association of H2H genes with DNA repair and carcinogenesis, such as a significant enrichment of bidirectional promoters for somatic breast cancer genes including BRCA1, BRCA2, FANCB2, and FANCD (Yang et al., 2007), and stronger selective pressures of methylation and copy number alteration on H2H organization in tumor samples (Thompson et al., 2018).