The Effect And Mechanisms Of Antileukemic Interactions Between Chidamide And Cytarabine Induced Apoptosis In K562and SEM Cell

The specific gene activation induced by chromosomal translocation is a keyfeature of human leukemia. One of the most common chromosomal translocation inacute lymphoblastic leukemia (ALL) is t (4;11)(q21;q23). Chronic myeloid leukemia(CML) occurs as a result of t (9:22)(q34; q11) chromosomal translocation, resultingin a fusion gene encoding the BCR/ABL fusion protein which have tyrosine kinaseactivity, and cells in a highly proliferative state non-depend on the growth factor.As one of the first-line drugs treatment of leukemia, cytarabine often be used bylarge dose to achieve the suppressor purpose, the serious adverse reactions oftenbecome the main reason for treatment failure. One way to reduce the toxicity andenhance the efficacy is to find an effective drug combinated with cytarabine to inhibittumor growth. Chidamide, a selective histone deacetylase inhibitors (HDACi) whichhas independently developed by China, is mainly used in cutaneous T-cell lymphoma(CTCL) and peripheral T cells lymphoid tumor (PTCL), and is undergoing Ⅱ/Ⅲclinical trials in many Chinese hospitals recently.Because the presence of t (4;11)(q21; q23,) chromosomal translocation oftenindicates a poor prognosis, and the presence of BCR/ABL fusion gene easy toproduce drug resistance and then lead to relapse, we select SEM and K562cells as theresearch object. In this study, MTT assay was used to detect the effect of chidamideon the proliferation of SEM and K562cells; drug synergy analysis software Calcusynwas used to analysis the synergies of chidamide and cytarabine. In order to furtherinvestigate the mechanism of chidamide in combination with cytarabine on SEM andK562cells, rhodamine123staining was used to detect cell transmembrane potential,flow cytometry was used to detect cell cycle and apoptosis, and Western blotting wasused to evaluate the related protein expression. The results showed that, the cell growth of SEM and K562cells can be inhibitedby chidamide alone, and chidamide joint cytarabine has a synergistic inhibitory effecton the SEM and K562cells. Observed under the inverted microscope, the cells ofcombined administration group showed that the number of cells was reduced, the sizewas inconsistent, and cell debris was visible compared with the control group andmonotherapy group. After stained by Rhodamine123, the cell’s fluorescence intensityin the combined administration group was significantly decreased compared with thecontrol group and monotherapy group. The flow cytometry detection showed that theratio of SEM and K562cells in G0/G1phase were increased by chidamide, and thejoint administration may further increase the proportion of SEM cells in G0/G1phase,while the joint administration may influence both S phase and G0/G1phase of K562cells. And the apoptosis rate of SEM and of K562cells can be increased by chidamidecombined with cytarabine. Western blotting analysis results show that the expressionof acetylated histone H3was up-regulated by chidamide in SEM and K562cells. Theexpressions of P-p53, p21, Bax and γH2AX were up-regulated while the expression ofBcl-2was down-regulated by chidamide, cytarabine and combined role in SEM cells.The expressions of γH2AX, Bim, Bax, Caspase-3and caspase-9were up-regulatedwhile the expressions of P-AKT and Bcl-2were down-regulated by chidamide,cytarabine and combined role in K562cells.Conclusion:①The cell proliferation of leukemia K562and SEM can beinhibited, and apoptosis can be promoted by chidamide.②Chidamide and cytarabinein combination had a synergistic inhibition of leukemia K562and SEM cellproliferation. The mechanism may be the③Chidamide and cytarabine incombination can promote p53protein phosphorylation and activate the p21signaltransduction pathway and the mitochondrial apoptotic pathway, thereby inhibite theproliferation of SEM cells. The④Chidamide and cytarabine in combination mayaffect the AKT signaling pathway and thus regulate mitochondrial apoptotic pathway,induce the apoptosis of K562cells.