Chronic and juvenile myelomonocytic leukemias (CMML and JMML) are aggressive myeloproliferative neoplasms that are incurable with conventional chemotherapy.
Unraveling the genetics of JMML has demonstrated that JMML in patients with germ line PTPN11 and CBL mutations often regresses spontaneously, and therapy is seldom indicated.
Somatic PTPN11 mutations contribute to leukemogenesis in children with hematologic malignancies including juvenile myelomonocytic leukemia, acute lymphoblastic leukemia, acute myeloid leukemia, and myelodysplasia.
Although abnormalities in the neurofibromatosis 1 (NF1) gene, which is a gene involved in the ras pathway, have been observed frequently in patients with juvenile chronic myelogenous leukemia, the role of these abnormalities in adult patients with AML or MDS is not clear.
We diagnosed a patient with NF1 at 25 months of age, before any cutaneous stigmata of this disease had appeared, because we decided to screen for the NF1 gene mutation because of his presentation with multiple JXGs and moderate macrocephaly (2.5 standard deviations) at 9 months of age and JMML diagnosed at 20 months of age.
Collectively, the results from molecular genetics study and survival analyses suggested a relatively higher frequency and unfavorable prognostic implication of PTPN11 mutations in Korean patients with JMML.
Finally, we found that primary cells from a patient with KRAS-mutant juvenile myelomonocytic leukemia displayed reduced colony formation in response to JAK2 inhibition.
Here, we report that hematopoietic cells differentiated from human induced pluripotent stem cells (hiPSCs) harboring NS/JMML-causing PTPN11 mutations recapitulated JMML features. hiPSC-derived NS/JMML myeloid cells exhibited increased signaling through STAT5 and upregulation of miR-223 and miR-15a.
We recently demonstrated that somatic PTPN11 mutations are the most frequent lesion in juvenile myelomonocytic leukemia and are observed in a smaller percentage of children with other myeloid malignancies.
Quantitative assessment of PTPN11 or RAS mutations at the neonatal period and during the clinical course in patients with juvenile myelomonocytic leukaemia.
Transduction of the PTPN11 mutation into JMML iPSCs with the wild-type of both genes increased CD34<sup>+</sup> cell production to a level comparable to that obtained with JMML iPSC colonies harbouring the two genetic mutations.
Determination of the catalytic activity of LEOPARD syndrome-associated SHP2 mutants toward parafibromin, a bona fide SHP2 substrate involved in Wnt signaling.
This report describes a juvenile myelomonocytic leukemia (JMML) case with a typical PTPN11 mutation (p.E76K) at different allele frequencies in the bone marrow mononuclear cells, buccal smear cells, and fingernails at diagnosis, which was suggestive of PTPN11 somatic mosaicism; however, the PTPN11 mutation in the buccal smear cells and fingernails was lost after unrelated cord blood transplantation.
Activating mutations of the PTPN11 gene encoding the SHP2 tyrosine phosphatase is the most common genetic abnormality in juvenile myelomonocytic leukemia and is sporadically observed in myelodysplasia (MDS) and acute myeloid leukemia (AML).
The phenotype is variable, and limited genotype phenotype correlation exists with SOS1 mutations often associated with normal cognition and stature, RAF1 mutations entailing a high HCM risk, and certain PTPN11 mutations predisposing to juvenile myelomonocytic leukemia.