SUZ12 Knockdown Suppresses The Human Cervical Cancer Cells And Esophagus Cancer Cells And Its Mechanism

Objective Suppressor of Zeste 12(SUZ12),which is one of the core subunits belonging to polycomb-group proteins(PcG),plays a critical role in promoting cell proliferation,inhibiting cell apoptosis,and stimulating the malignant transformation of cells.This study was aimed to investigate the effects of down-regulation of SUZ12 expression on the proliferation of human cervical cancer cells and esophageal cancer cells and the mechanisms.Methods Small interfering RNA technology was applied to down-regulate SUZ12 expression.Western blot analysis was performed to detect the protein expression in siSUZ12-transfected human cervical cancer cells and esophageal cancer cells.MTT assay and plate clone formation assay were performed to explore the effect of decreases in SUZ12 expression on the proliferation of human cervical cancer cells and esophageal cancer cells.Flow cytometry was performed to determine the impact of siSUZ12 on cell cycle.p-galactosidase staining was performed to detect the inductive effect of siSUZ12 on cell senescence.Overexpressed cell lines and corresponding controls were constructed using lentivirus transfection technology.Results SiSUZ12 effectively blocked cellular SUZ12 expression.Ten-nM siSUZ12 could exert an inhibitory effect on the proliferation of Hela and MS751cell lines,which reached at peak when the concentration of siSUZ12 was 100nM.The cell proliferation was inhibited by 20nM of siSUZ12 in SiHa cell lines.Maximum inhibition efficiency was produced by 50nM of siSUZ12.Compared to the control group,the proliferation rate of Hela cells at Day 5 after transfection with 50nM siSUZ12 was 56.13±7.78%(P<0.01).The proliferation rate of MS751cells and SiHa cells at Day 7 after transfection with 50nM siSUZ12 was 48.01±6.92%(P<0.01),and 38.29±5.70%(P<0.01)respectively.Ten-nM siSUZ12 could suppress the proliferation of hunan esophageal cancer Kyse-150 cells,which reached at peak when the concentration of siSUZ12 increases to 50nM.However,the proliferation rate of Kyse-150 cells reduced to 38.61±5.32%(P<0.01)at Day 6 after transfection.Results obtained from plate clone formation assay showed that the colony formation amounts of control siRNA-transfected Hela cells and siSUZ12-transfected Hela cells were 152.00±16.37 and 112.33±8.08(P<0.05)respectively.The colony formation amounts of control siRNA-transfected MS751 cells and siSUZ12-transfected MS751 cells were 26.00±9.17 and 3.67±1.53(P<0.01)respectively.The colony formation amounts of control siRNA-transfected SiHa cells and siSUZ12-transfected SiHa cells were 48.33±1.15 and 23.33±7.02(P<0.05)respectively.The colony formation amounts of control siRNA-transfected Kyse-150 cells and siSUZ12-transfected Kyse-150 cells were 42.67±3.06 and 9.67±2.89(P<0.01)respectively.Results from cell cycle assay showed an obvious increase in the proportion of Hela cells in G0/G1 phase after 48h siSUZ12 transfection(P<0.05),suggesting that cells were arrested in Gl/S phase.The proportion of SiHa cells in G2/M phase markedly increased after 60h siSUZ12 transfection(P<0.01),implying that cells were arrested in G2/M phase.The proportion of Kyse-150 cells in G0/G1 phase obviously elevated after 96h siSUZ12 transfection(P<0.01),suggesting that cells were arrested in G1/S phase.Both intracellular granules and the proportion of positive cells stained with?-galactosidase increased after SUZ12 decreases,which suggested distinct senescent characteristics.SiSUZ12 transfection significantly decreased the lethality of cisplatin in cervical cancer cells and esophageal cancer cells which was featured by reduced IC50 values,and the combination index(CI)is less than 1,suggesting that siSUZ12 had a synergistic effect with cisplatin.Western blot analyses showed that down-regulation of SUZ12 expression significantly inhibited the expression of cellular CDC25C,while overexpression of CDC25C could effectively antagonize the inhibitory effect of siSUZ12 on cells.Conclusion Down-regulation of SUZ12 expression by siSUZ12 could significantly suppress the proliferation of human cervical cancer cells and esophageal cancer cells.SUZ12 decreased resulted in cell cycle arrest of Hela cells and kyse-150 cells in G1/S phase and arrested SiHa cells in G2/M phase,inducing cell senescence.Decreases in SUZ12 expression could enhance the sensitivity of human cervical cancer cells and esophageal cancer cells to cisplatin.Down-regulation of SUZ12 expression exerted its inhibitory effect on cell proliferation by interfering the expression of CDC25C.