APOBEC3B and cancer: Although the mutation load varied among the 33 cancer types in TCGA, we found that the median value for the C-to-T mutation load correlated positively with expression of A3B (Spearman’s r = 0.7706, P < 0.0001) and of MYBL2 (Spearman’s r = 0.5964, P = 0.0002) (Fig. 5B,C).