JAK3 and mycosis fungoides: The expression of miR-155 is enhanced in the affected skin of MF patients compared to that in healthy individuals.[8,18] The host gene of miR-155 is BIC, which is transcribed by STAT5.[20] Upregulated miR-155 binds and cleaves its target gene, STAT4, in advanced MF patients skin biopsies.[21] The PI3K/AKT, JAK/STAT, and MAPK signaling pathways negatively regulate signaling through miR-155, directing inositol phosphatase SHIP1 and SOCS1.[22–24] When JAK3 phosphorylates STAT5, it translocates to the nucleus and initiates the transcription of miR-155.