APOBEC3B and neoplasm: Mice in which A3B expression could be temporally separated from EGFRL858R expression (EA3Bi), allowing for induction of A3B expression in a subset of tumor cells within the already proliferating EGFRmut tumor, were generated to mirror subclonal APOBEC induction and to assess if subclonal A3B expression decreased tumor cell death observed at initiation11,12,21,27 (Extended Data Fig. 2a).