PAK1 Inhibition Slows Growth and Partially Promotes Differentiation of AMKL Cells

Abstract

Purpose Acute megakaryoblastic leukaemia is characterized by the expansion of megakaryoblasts, which are hyperproliferative and fail to undergo differentiation or polyploidization. Although recent studies have proposed that inducing immature AMKL cells to undergo differentiation is a good therapeutic strategy, there is still no satisfactory medicine for clinical application because of the unclear enrichment of megakaryoblasts. It has been reported that p21 (RAC1)-activated kinase 1 (PAK1) participates in megakaryoblastic proliferation and differentiation, and its upregulation is related to AML development, but its role in AMKL remains unclear. Method The mRNA level of PAK1 was analyzed according the GSE4119 dataset by calculating the copy numbers of PAK1 to GAPDH. The protein level of PAK1 was detected in primary mouse AMKL cells with overexpression of MPLW515L mutant gene. The biological function was examined in AMKL cells after PAK1 inhibition by EdU staining, western blot, Annexin V/FITC, and flow cytometry assay, respectively.Results Here, we found that the mRNA and protein level of PAK1 was enriched in AMKL patients or cells, and inhibition of PAK1 significantly induced the arrested growth of the AMKL cell line. Further analysis of the protein expression of downstream of PAK1 showed that blocking the activity of PAK1 downregulated the expression of cyclin D1. Two PAK1 inhibitors partially and modestly promoted polyploidy formation in both CHRF and CMK cells. Additionally, these PAK inhibitors consistently promoted cell apoptosis by upregulating cleaved caspase 3. In accordance with the inhibitor effects on AMKL cells, PAK1 knockdown also increased the polyploid DNA content of CHRF and CMK cells and significantly induced cell apoptosis. Conclusions These results suggest that PAK1 might be a critical gene that drives the proliferation and differentiation of AMKL cells, and inhibiting the activity of PAK1 might be an effective method of controlling AMKL.