Experiments based on murine ALL models showed that in E2a:PBX1 B-ALL, the relapsed cells lost CD19 expression but expressed myeloid antigens post-CD19 CAR T-cell treatment, and the frequency was much lower in Eμ-RET B-ALL, suggesting that lineage switching-mediated CAR T-cell therapy resistance is related to genetic background (47). The gene discussed is RET; the disease is acute lymphoblastic leukemia.