FosB regulates expression of miR-22 during PMA induced differentiation of K562 cells to megakaryocytes.

Expression of many miRNAs is altered in different cancers and these changes are thought to play a key role in formation and progression of cancer. In chronic myelogenous leukemia (CML) a number of miRNAs are known to be down regulated as compared to normal cells. In this report we have investigated the mechanism of this down regulation by using PMA induced differentiation of CML cell line K562 to megakaryocytes as an experimental system. On treatment with PMA, expression of many down regulated miRNAs including miR-22 is induced. PMA also induces expression of several transcription factors, including FosB, EGR1 and EGR2. Our results using a number of approaches, such as promoter reporter assay, FosB knock down and Chip assay, suggest that the expression of miR-22 is regulated transcriptionally by FosB.