AICDA and acute lymphoblastic leukemia: The second signature is characterized by a high proportion of C > G substitutions at TpCpA or TpCpT motifs (Supplementary Figure S5), was predominantly observed in BCP-ALL patients with the t(12;21) subtype, and is known to be induced by increased activity of the AID/APOBEC family of cytidine deaminases [13].