APOBEC3A and neoplasm: Analyzing the 4-nucleotide context of 788 WGSs from 27 tumor types with evidence of APOBEC activity enrolled within the PCAWG ICGC consortium, we observed a strong positive association between APOBEC3A/APOBEC3B ratio and APOBEC mutational burden (linear regression p < 0.0001; Fig. 2d, e).