Effects of Down-Regulation of PAK1 on Differentiation and Apop-tosis of MPN Cells with MPLW515L Gene Mutation and Survival of 6133/MPL Mice
Objective:To investigate the effects of down-regulation of p21 activated kinase 1(PAK1)on the proliferation,differentiation,and apoptosis of myeloproliferative neoplasm(MPN)cells(6133/MPL)with thrombopoietin receptor MPL mutation at codon 515(MPLW515L)and survival of 6133/MPL mice.Methods:Interference with the protein level of PAK1 in 6133/MPL cells was assessed using lentivirus-mediated shRNA transfection technology.CCK-8 assay was used to detect the effect of down-regulation of PAK1 on the proliferation viability of 6133/MPL cells,and colony-forming ability was measured by cell counting.Flow cytometry was used to detect the PAK1 kinase activity on the ability of polyploid DNA formation and cell apoptosis in 6133/MPL cells.The expression of cyclin D1,cyclin D3 and apoptosis-related protein Bax was detected by Western blot.The infiltration of tumor cells in spleen and bone marrow of 6133/MPL mice were detected by HE staining.Results:Down-regulation of PAK1 inhibited the proliferation and reduced the ability of cell colony formation of 6133/MPL cells.After knocking down PAK1,the content of polyploid DNA in 6133/MPL cells increased from 31.8 to 57.5%and 48.0%,and the proportion of apoptosis increased approximately to 10.8%.Down-regulation of PAK1 led to a reduction of infiltration of tumor cells in liver and bone marrow of 6133/MPL mice,thereby prolonging survival time.Conclusion:Down-regulation of PAK1 can significantly inhibit the growth of 6133/MPL cells,promote the formation of polyploid DNA,induce 6133/MPL cell apoptosis,and prolong the survival time of 6133/MPL mice.