[Effects of Down-Regulation of PAK1 on Differentiation and Apoptosis 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.