In summary, both the non-selective BCL-2/BCL-XL inhibitor ABT737 and the selective BCL-XL inhibitor A1155463 exerted synergism to kill JMML cells in combination with azacitidine, and additionally targeted leukemia-initiating cells better than azacitidine. The gene discussed is BCL2L1; the disease is juvenile myelomonocytic leukemia.