PTPN11 and juvenile myelomonocytic leukemia: Mutations in KRAS, NRAS, RRAS, or RRAS2 or in their regulators PTPN11 (encoding for SHP2), CBL, or NF1 [1–7] in JMML cells, enhance proliferation and myelomonocytic differentiation upon cytokine stimulation (i.e., GM-CSF) [8].