Recombination-deficient breast cancers have elevated APOBEC signature mutagenesis. (A) Position of germline mutations in BRCA1 and BRCA2 present in 560 breast cancers sequences as part of the International Cancer Genome Consortium. (B) Median estimated number of COSMIC SBS2, SBS13, and SBS2 + SBS13 mutations in breast cancers from BRCA-proficient and BRCA-mutant patients. (C) Replication strand bias of SBS13 mutations in tumors from BRCA-proficient and BRCA-deficient patients. (D) Enrichment of A3B-like (RTCA) and A3A-like (YTCA) signature mutations in BRCA-proficient and BRCA-deficient tumors. Increased representation of the A3B-like mutation signature compared with the A3A-like mutation signature among BRCA1/2-mutant tumors was assessed by chi-square test (P = 8.88 × 10−8).
