HOXA9 and acute myeloid leukemia: Furthermore, we found cAMP signaling, which has a role for cell proliferation, differentiation and migration as well as the homeodomain-containing transcription factor HOXA9, which is implicated in hematopoietic stem cell expansion and acute myeloid leukemia, to be up-regulated in ALK tumors compared with Ctrl thymocytes (36, 37).