HOXA9 and acute myeloid leukemia: PCGF4 is overexpressed in AML cells [131]; Pcgf4 is not needed for leukemia development; oncogenic Hoxa9‐OE Pcgf4−/− cells are able to transform into AML cells [126]; Pcgf4 is needed for the maintenance of leukemic cells; Pcgf4−/− HSCs have reduced proliferative capacity and they fail to repopulate recipients in secondary transplantations [126]