The Role Of S100A8on Autophagy And Drug Resistance In Leukemia Cells

Objective To investigate the role of S100calcium-binding protein A8(human S100calcium binding protein A8, S100A8) on autophagy and drug resistance in Leukemia Cells. Methods Firstly, protein expression levels in bone marrow mononuclear cells (BMMCs) and blood plasma were measured by enzyme-linked immuno sorbent assay (ELISA) and Western Blotting (WB) in children with acute leukemia diagnosed during three years nearly. Then3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-etrazolium bromide (MTT) detected the IC50on different leukemia cell lines, through which we got the different degrees of resistance to chemotherapeutic drugs on different leukemia cell lines. We investigated S100A8mRNA and protein levels in different cell lines by Realtime PCR and Western Blotting analysis, for exploring the relationship between the S100S8and chemotherapy resistance on the leukemia cells. Jurkat, HL-60and K562cells were treated with several chemotherapeutic drugs (ADR, VCR). Through gene transfection, RNA interference (RNAi) technology and western blotting etc to detecte whether S100A8affect the sensitivity to chemotherapy by regulating autophagy on the leukemic cells. Result①Expression levels of S100A8in primary/relapse group were much higher than complete continuous remission (CCR) group and normal control group(*P<0.05).②hemotherapy drugs increased the expression of S100A8in leukemia cells (n=3, P<0.05).③xpression of S100A8in leukemia resistant cell lines (HL-60/ADR, K562/AO2) was higher in non-resistant cell lines (K562, HL-60and Jurkat)(n=3, P<0.05);④Inhibited the expression of S100A8in leukemia cells decreased survival rate after chemotherapy and increased the rate of apoptosis. Moreover, inhibited the expression of S100A8in leukemia cells increased the expression of P62but decreased the expression of LC3-I/II, transmission electron microscopy further explained that autophagy was restrained.⑤Up-regulated the expression of S100A8increased LC3-II, Beclinl protein levels and the number of autophagic vesicles, but decreased protein levels of p62. Moreover, silencing of PI3KC3, Beclin1, and Atg7genes which are critical autophagic regulators in mammalian cells inhibited S100A8overexpression-induced LC3-II formation and prevented p62degradation, even made survival rate significantly decreased on the leukemia cell after doxorubicin and vincristine treatment. Conclutions S100A8was involved in the pathogenesis in pediatric AL. The expression of S100A8is closely related to chemoresistance on leukemia cells. These findings supplied further evidence of the role of S100A8on autophagy and chemoresistance of leukemia cells, which will help to establish more efficient chemotherapies for leukemia.