IL9 and neoplasm: For instance, decitabine‐mediated DNA methylation inhibition reactivates silenced antitumor immune genes in advanced tumors, thereby augmenting tumor‐infiltrating lymphocytes and attenuating tumor progression.[6] Interleukin‐9 (IL‐9) secretion from leukemia stem cells activates Janus kinase (JAK)‐signal transduction and activator of transcription (STAT) signaling in CD4+ T cells, enhancing histone 3 lysine 4 methylation (H3K4me).