ATF4 and acute myeloid leukemia: Furthermore, in vitro studies on FLT-3 mutated AML cells showed a decreased production of IL-15; studies in animals showed that the FLT-3 inhibitor sorafenib increases IL-15 production by FLT-3 AML cells through the inhibition of the transcriptional factor ATF4 causing activation of the IRF7–IL-15 axis in leukemia cells [20].