The increased availability of the substrate (STAT5b) caused by downregulation of miR-150-5p, may enhance the phosphorylation activation of STAT5b caused by the gain of function mutations in the RAS/ERK pathway key genes, such as KRAS, NRAS, NF1 and PTPN11 in JMML. The gene discussed is STAT5B; the disease is juvenile myelomonocytic leukemia.