GAB2 and acute myeloid leukemia: We noted substantial variation from mouse to mouse and tumor to tumor, likely driven by biological differences between individual tumors, as well as variability in the level of Gab2 inactivation achieved by the library of Gab2 indels created at baseline in tumors with 3 copies of Gab2 (e.g., some frameshift mutations in Gab2 may occur in AML cells that retain 1 or 2 WT copies of Gab2) (Supplemental Figure 6).