The results showed that tamoxifen‐induced Prmt1 loss blocked leukemia development (Figure S4C, Supporting Information) and prolonged the survival of CML mice (median survival: Prmt1fl/fl vs Prmt1fl/fl; Cre‐ERT2 was 14.5 days vs not reached after monitoring for 60 days; Figure S4D, Supporting Information). The gene discussed is MAPK3; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.