Inhibitory Effect Of Valproic Acid On Cell Cycle Of Kasumi-1Cell Line In Nude Mice

Objective:It is the key pathogenesis t(8;21) chromosome translocation forming AML1/ETO fusion protein recruiting histone deacetylase to inhibit the transcription of the target genes of AML1.We investigate whether histone deacetylase(HDAC),valproic acid(VPA),can inhibit Kasumi-1cell xenograft tumor proliferation and the influence of factors of cell cycle.Material and method:Kasumi-1cell line model transplanted subcutaneously in nude mice were established, to observe the growth of nude mice xenograft tumors and inhibition rate.Kasumi-1cell of each group cell cycle changes were analyzed by flow cytometry.P21WAF1/CIP and pRb were detected by immunohistochemistry and Western blot. The expression change of mRNA P21WAF1/CIP was detected by RT-PCR.Result:1. The Characteristics of Kasumi-1Xenograft Tumor modelWe established Kasumi-1cell line tumor xenografts. The tumor formation rate of mice is100%. With the prolongation of time, the tumor volume became large markedly and cell growth curve was generated. Semi-quantitation RT-PCR was used to validated the expression of AML1/ETO mRNA.2. VAP inhibited Kasumi-1xenograft tumor growthVPA inhibited the proliferation of the Kasumi-1cell xenograft tumors VPA obviously inhibited the growth of tumor,animals treaed with VPA showed a statistically significant decrease in tumor volume and weight,average tumor weight is (0.46±0.17)g and relative tumor volume is (0.46±0.17) in VPA treated group, average tumor weight is (1.57±0.25)g and relative tumor volume is (1.57±0.25) in control group, up to57.25%growth inhibition as compared with controls.3.The influence of cell cycle in Kasumi-1cell xenograft tumors with VPA treated group.VPA blocked cell in G0/G1phase were detected by flow cytometry.Compared with control group,VPA group showed a statistically significant decrease in G0/G1phase Kasumi-1cell of control group and VPA group scale discern for (60.93±1.18)%、(74.05±3.06)%.significant difference in statistics (P<0.01).4.The influence of P21WAF1/CIP in Kasumi-1cell xenograft tumors VPA treated group.To analyse with semi-quantitation RT-PCR, Western blot and Immunohistochemistry it was found that the mRNA level of P21WAF1/CIP increased obviously. Western blot was used to detect protein expression of P21WAF1/CIP Compared with control group (0.39±0.012), the protein level of P21WAF1/CIP (0.900±0.113) decreased obviously, with statistical significance (P<0.01).Immunohistochemistry was used to detect protein expression of P21WAF1/CIP. Compared with control group (0.1527±0.620), the protein level of P21WAF1/CIP(0.4186±0.1870) increased, with statistical significance (P<0.01).5.The influence of pRb in Kasumi-1cell xenograft tumors VPA treated group.Western blot was used to detect protein expression of pRb. Compared with control group (0.813±0.042), the protein level of pRb (0.342±0.062) decreased obviously, with statistical significance (P<0.01).Immunohistochemistry was used to detect protein expression of pRb. Compared with control group, the protein level of pRb decreased obviously, with statistical significance (P<0.01).Conclusion:VPA is a kind of histone deacetylase, can inhibit the proliferation of Kasumi-1cell xenograft tumorand accumulate cells at G0/G1phase, VPA can cause Rb low phosphorylation state by P21WAF1/CIP increased level of proteins,make the cell block from G0/G1phase.Thus inhibiting leukemia cell growth,hinder the progress of leukemia.This research for VPA treatment of acute leukemia clinical application provides theoretical basis.