Leukemia-related Mutations In Gain-of-function Mutant Shp2 Tyrosine Phosphatase May Contribute To Leukocyte Infiltration And Multiple Organ Dysfunction Syndrome

SHP-2 is a two SH2 domain-containing tyrosine phosphatase, widely expressed in various organizations involved in embryonic development, cell proliferation, differentiation, adhesion, migration and other biological behavior of the signal control. Currently, SHP-2 mutation was found in Noonan syndrome and cancer patients. It is the first tyrosine phosphatase that was defined as the oncogene. And tumor-associated gain-of-function mutations of SHP-2 mainly located in the N terminal SH2 domain, the most common were E76K and D61G / Y, these mutations make the the self-combination of the N-SH2 and PTP domain partialy or completely dissociated, leading to the activity of SHP-2 tyrosine phosphatase increasing at different degrees. Gain-of-function mutations in SHP-2 may be closely related to cancer, especially the malignant biological behavior in leukemia cells, such as high sensitivity of proliferation, drug-resistant, easy to invasion, metastasis. Clinical data also found that the presence of SHP-2 gain-of-function mutation in patients was 35% in some children who have Juvenile myelomonocytic leukaemia (JMML), they fell sick very early, develope rapidly. The majority of patients early died due to a large number of leukocyts including leukemia cells infiltration to multiple organs Therefore, the study of mechanisms to control leukocyts infiltration in children with JMML will be greatly significant. In vitro experiments confirmed: high expression of SHP-2 gain-of-function mutant cells, its ability of adhesion and discrete were significantly enhanced.However, apart from phosphatase activity in SHP-2, but also SHP-2 has the function of adapter protein. Overexpress the mutant SHP-2 in human does not match the actual conditon. Benjaming Neel established SHP-2 D61G mutant gene knock-in mouse model, so soluted this problem best. Homozygous mutant mice at the embryonic were died, only 50% of heterozygous mutant mice survived and growed in the natural state which have a typical phenotype resembling to human Noonan syndrome. And caused the proliferation of myeloid disease, but did not find malignant phenotype, such as leukemia.After our research group received the model mice, we mainly work for the following tasks: 1. If there are mice with myeloid proliferative disease, will the leukocyts high proliferative responsive to the existence of IL3? 2. Is the leukocyte adhesion and migration capacity of mice increasing? Are the secretion of inflammatory cytokines on the rise? Namely, whether there is leukocyte infiltration which led to multiple organ injury; 3. Can it happen to leukemia? What is the relation between the biological behavior of malignant and leukemia? Therefore, this study is using of model mice which have SHP-2 D61G gain-of-function mutation to observe the lekucyts which express SHP-2 in physiological level but have gain-of-function mutation. We investigate the cells'change of ability in adhesion, invasion and its effect to organ damage, and the possible preliminary study of molecular mechanisms.The results showed that, SHP-2 D61G / + mutant mice activated leukocyte adhesion, migration compared with the control wild-type mice (WT) significantly increased; in mutant mice, the expression of IL-2 and TNF-αmRNA from leukocyte was significantly higher abundance, IL-2, TNF-αconcentrations increased accordingly in the supernatant; furtherly, we found the levels of aminotransferase (ALT) and cardiac troponin I (CTni) in serum were significantly higher in mutant mouse than the control mice; leukocyte infiltration in the liver, spleen and lung tissue increased, appeared histological changes as inflammatory injury type; the research for mechanism in mutant mice found that the transfer of NF-κB significantly increased in leukocyts. These results prompt SHP-2 gain-of-function mutations may at least through the enhanced NF-κB signaling pathway, then promote leukocyte adhesion, and invasion to various tissues and organs, while enhance the ability of secreting inflammatory factors, mediate to significant tissue damage. The results provide some clues for study the clinical leukemia patients why easily appear the mechanism of multiple organ failure.