依托泊苷诱导的人小肠类器官衰老模型的构建及鉴定

目的 用依托泊苷(etoposide)诱导类器官发生DNA损伤构建人小肠类器官衰老模型。方法 临床活检小肠组织，体外无菌分离获得小肠隐窝，在培养基中培养成为类器官。类器官用依托泊苷10μmol·L^-1处理7 d，倒置相差显微镜观察类器官表面形态变化，Western印迹法检测DNA损伤标志物磷酸化组蛋白H2AX(γH2AX)水平；衰老相关β半乳糖苷酶(SA-β-gal)活性染色检测类器官SA-β-gal阳性细胞面积百分率，Western印迹法检测衰老标志物p16^INK4A蛋白表达水平。结果 人小肠隐窝体外成功培养成球。依托泊苷诱导的人小肠类器官衰老模型表面皱缩，类器官部分死亡，整体表面积变小；类器官中γH2AX蛋白表达显著上调(P<0.01);SA-β-gal阳性细胞面积百分率显著增加(P<0.01)，约90%细胞呈SA-β-gal阳性；p16^INK4A蛋白表达显著增加(P<0.01)。结论 依托泊苷处理可诱导人小肠类器官发生DNA损伤，从而诱导人小肠类器官衰老。     

太白楤木活性成分竹节参皂苷Ⅳa抗氧化及抗衰老作用研究

目的探讨太白楤木皂苷中的重要成分竹节参皂苷Ⅳa(CHS)抗氧化及抗衰老作用。方法取5~8代的小鼠胚胎成纤维细胞(MEFs),使用过氧化氢(H2O2)诱导细胞氧化应激以及细胞衰老模型。MTT法分别检测不同浓度CHS及H2O2对细胞活力的影响;DCFH-DA染色流式细胞仪检测细胞总活性氧(ROS)水平;Mito SOX染色流式细胞仪检测细胞线粒体ROS水平;衰老相关β-半乳糖苷酶(SA-β-gal)染色检测细胞衰老状态;Western blot法检测衰老标志蛋白p53、p21蛋白表达水平以及关键抗氧化应激Nrf2通路(Nrf2、HO-1、GCLC、GCLM)蛋白表达。结果浓度≤160μg·m L-1的CHS对MEFs细胞无明显毒性作用;H2O2能够显著提高细胞总ROS和线粒体ROS水平,诱导细胞衰老指标SA-β-gal活性增加,提高p53、p21表达水平,提高抗氧化信号通路Nrf2通路表达水平。CHS能够剂量依赖地降低H2O2诱导的细胞总ROS和线粒体ROS水平,减轻H2O2诱导的SA-β-gal活性升高,抑制p53、p21以及Nrf2、HO-1、GCLC、GCLM蛋白表达水平的升高。结论 CHS具有显著的抗氧化应激和抗衰老作用。     

三种GC-1细胞DNA损伤模型的建立及比较分析

目的建立3种小鼠睾丸精原细胞株GC-1细胞DNA损伤模型并分析其异同。方法分别采用UVB辐照、D-半乳糖(D-Galactose,D-Gal)、博来霉素(bleomycin,BLM)刺激GC-1细胞不同时间,Western blot和免疫荧光法检测γ-H2AX表达及定位;免疫荧光法检测8-OHdG表达及定位;Western blot法检测p-p53和p21表达水平。结果UVB辐照和D-Gal处理后,γ-H2AX蛋白表达分别在4 h和6 h达高峰BLM刺激后,γ-H2AX蛋白表达逐渐上升且BLM浓度越高,其达到高峰时间越短。UVB辐照和BLM刺激后,胞核胞质内均有8-OHdG表达,且时间越长,核内表达越多;D-Gal处理后,8-OHdG主要表达在胞质,且在6 h达高峰。UVB辐照后,p-p53和p21蛋白表达不断上升,p21表达较滞后;D-Gal处理后,p-p53和p21表达分别在6 h和12 h达高峰;BLM刺激后,p-p53和p21蛋白表达呈同步上升趋势,BLM浓度越高,其达高峰时间越短。结论成功建立3种GC-1细胞DNA损伤模型,且D-Gal处理GC-1细胞DNA损伤较轻,而UVB辐照和BLM刺激DNA损伤较重。     

博宁霉素引起肿瘤细胞衰老的特征

鉴于细胞衰老是抑制肿瘤的重要步骤,考察博宁霉素引起人肿瘤细胞衰老的特征。采用MTT法和克隆形成率实验检测细胞增殖抑制作用;衰老相关的β-半乳糖苷酶染色检测细胞衰老;流式细胞仪测定细胞周期分布以及细胞内活性氧自由基水平;Western blotting检测蛋白的表达水平。结果表明,博宁霉素对人口腔上皮癌KB细胞的作用,明显强于人非小细胞肺癌A549细胞。与阳性对照药多柔比星的作用相似,博宁霉素可引起这两种细胞均出现衰老特征,这与细胞阻滞在G2/M期、细胞内活性氧自由基增加有关。0.1μmol·L-1博宁霉素可以诱导KB细胞衰老,检测到衰老标志蛋白P21的表达明显增加;而高浓度的博宁霉素激活细胞凋亡通路。本研究结果表明:博宁霉素引起细胞衰老,也是其抑制肿瘤细胞增殖的机制之一。     

藻红蛋白诱导人乳腺癌MCF-7细胞衰老研究

目的:研究藻红蛋白对人乳腺癌MCF-7细胞的诱导衰老作用。方法:采用MTT法检测藻红蛋白对MCF-7细胞的生长抑制作用,采用倒置显微镜观察形态学变化,酸性β-半乳糖苷酶染色法和衰老相关异染色质聚集检测藻红蛋白诱导人乳腺癌MCF-7细胞衰老作用。结果:MTT法结果显示,藻红蛋白对体外培养的人乳腺癌细胞MCF-7具有明显的生长抑制作用,IC50为134.87μg/mL。结果发现藻红蛋白作用72h后,细胞呈现变大变扁平,细胞内形成空泡、颗粒增多等明显衰老形态。在倒置显微镜下观察,酸性β-半乳糖苷酶染色呈阳性;在荧光显微镜下观察,DAPI染色出现衰老相关异染色质聚集现象。结论:藻红蛋白可通过诱导MCF-7细胞衰老达到抗肿瘤作用。     

机械敏感离子通道Piezo1通过激活β-catenin诱导心房成纤维细胞衰老北大核心CSCD

目的 衰老心房成纤维细胞中新型机械敏感离子通道Piezo1的基因表达明显升高,观察其是否通过激活β-catenin参与心房成纤维细胞的衰老进程。方法 通过酶消化法分离培养3~4周龄雄性C57BL/6小鼠原代心房成纤维细胞,给予叔丁基过氧化氢(TBHP)刺激建立衰老模型,检测衰老相关β-半乳糖苷酶(SA-β-Gal)活性。Western blot检测TBHP(100μmol·L^(-1))处理的细胞中Piezo1、β-catenin/p-β-catenin及衰老相关蛋白p53和p21的表达水平。衰老的小鼠心房成纤维细胞(MAFs)分别给予Piezo1通道抑制剂GsMTx4(3、10μmol·L^(-1))或Piezo1 siRNA,以及β-catenin抑制剂XAV939(3、10μmol·L^(-1));年轻的MAFs给予Piezo1特异性激动剂Yoda1(1、10μmol·L^(-1)),观察对细胞中β-catenin和衰老相关蛋白表达和活性的影响。结果 TBHP处理后,MAFs的SA-β-Gal染色阳性率明显增加,提示细胞发生衰老;且细胞中Piezo1、β-catenin/p-β-catenin和p53/p21的蛋白表达明显增加(P<0.05)。分别抑制Piezo1(GsMTx4/Piezo1 siRNA)或β-catenin(XAV939),可明显降低TBHP诱导的MAFs衰老率,以及减少β-catenin/p-β-catenin,p53/p21等蛋白表达和活性的增加(P<0.05)。而Yoda1可促进年轻细胞衰老,且β-catenin活性和衰老相关蛋白表达升高(P<0.05)。结论 机械敏感离子通道Piezo1通过激活β-catenin诱导心房成纤维细胞衰老的病理过程。     

人参皂苷Rg1对细胞衰老过程中p21，cyclin E和CDK2表达的影响

目的探讨p21、细胞周期蛋白E (cyclin E) 和周期蛋白依赖性蛋白激酶2 (cyclin-dependent kinase 2, CDK2) 在人参皂苷Rg1对抗三丁基过氧化氢(t-BHP)诱导WI-38细胞衰老过程中的可能作用。方法细胞超微结构、流式细胞分析和β-半乳糖苷酶细胞化学染色观察衰老细胞，蛋白印迹法检测p21,cyclin E和CDK2蛋白的表达。结果Rg1预处理可明显减弱t-BHP对WI-38细胞衰老的诱导作用，同时p21表达水平明显降低，cyclin E和CDK2表达水平增加。结论人参皂苷Rg1对抗三丁基过氧化氢对细胞衰老的诱导作用可能与其改变p21，cyclin E和CDK2的表达水平有关。     

补肾填精方对D-半乳糖衰老模型大鼠脑细胞周期相关蛋白表达的影响

目的探讨抗衰老中药方剂补肾填精方对D-半乳糖衰老模型大鼠脑细胞周期相关p53、p21和p16蛋白表达的影响。方法采用D半乳糖法诱导衰老大鼠模型。随机分为正常组、模型组、天保宁组、补肾填精方（低剂量组、中剂量组、高剂量组）。免疫组化法检测各组大鼠脑海马CA1区细胞周期相关p53、p21和p16蛋白表达。结果补肾填精方能抑制海马CA1区细胞周期相关p53、p21和p16阳性蛋白的表达（P〈0．05）。结论补肾填精方可降低衰老大鼠海马CA1区p53、p21和p16蛋白表达,提示补肾填精方延缓脑细胞衰老可能与细胞周期相关蛋白表达相关。     

人参皂苷Rg1对细胞光老化模型中p53信号转导途径的影响

目的观察人参皂苷Rg1对光老化p53信号转导途径中相关基因损伤及蛋白表达水平的影响。方法采用8-MOP/UVA(8-methoxypsoralen and subsequent ultraviolet A irradiation)联合处理人皮肤成纤维细胞建立光老化模型,用流式细胞周期分析、SA-β-半乳糖苷酶(senescence associatedβ-galactosidase)化学染色,免疫荧光及Western blot等方法检测人参皂苷Rg1对培养真皮成纤维细胞多项细胞衰老指标及p53信号途径中蛋白表达的影响。结果人参皂苷Rg1可明显抑制细胞和组织老化的指标表达(包括SA-β-Gal表达减少及细胞周期G1阻滞率降低);减少基因氧化应激损伤产物8-oxo-dG及老化相关蛋白p53,p21WAF-1及p16INK-4a的表达。结论人参皂苷Rg1可能通过缓解基因的氧化应激损伤,抑制相关信号转导,从而缓解细胞光老化进程。     

红景天苷对肝癌细胞凋亡的诱导实验研究

目的:以HepA小鼠为实验对象,通过红景天苷对肿瘤细胞凋亡的诱导实验,探讨其在诱导小鼠肝癌细胞凋亡过程中的作用。方法:将小鼠肝癌模型随机分为三组,分别为对照组、环磷酰胺组、红景天苷组,通过一系列细胞生物学实验,观察和测定各组细胞周期的变化及p53、Bcl-2、Bax蛋白表达的程度。结果:与对照组比较,红景天苷组在细胞凋亡指数、G0/G1期肿瘤细胞数量、相关蛋白表达程度等方面,差异有统计学意义(P<0.01),Bax表达水平提高,Bcl-2表达水平降低。结论:红景天苷可干扰细胞周期、抑制肿瘤细胞生长,在肝癌细胞凋亡的诱导实验中,红景天苷可激活线粒体途径,诱导凋亡的过程还受到p53的调节。     

Extrinsic apoptosis and senescence involved in growth kinetics of seminoma to cisplatin

Seminoma is the most common type of testicular germ cell tumour and is highly sensitive to cisplatin therapy, which has not been fully elucidated. In this study, we comprehensively monitored dynamic changes of TCam-2 cells after cisplatin treatment. At an early stage, we found that both low and high concentrations of cisplatin induced the S-phase arrest in TCam-2 cells. By contrast, the G0G1 arrest was caused by cisplatin in teratoma NTERA-2 cells. Afterwards, high concentrations of cisplatin promoted the extrinsic apoptosis and high expressions of related genes (Fas/FasL-caspase-8/-3) in TCam-2 cells. However, when decreasing the cisplatin, the apoptotic cells were significantly reduced, and accompanied by cells showing senescence-like morphology, positive SA-β-gal staining and up-regulation of senescence-related genes (p53, p21 and p16). Furthermore, the cell cycle analysis revealed that most of the senescent TCam-2 cells were irreversibly arrested in the G2M phase. G2M arrest was also observed in NTERA-2 cells treated with a low concentration of cisplatin, while no senescence-related phenotype was discovered. In addition, we detected the γ-H2AX, a DNA damage marker protein, and reactive oxygen species (ROS) and found both of which were elevated with the increase of cisplatin in TCam-2 cells. In conclusion, the extrinsic apoptosis and senescence are involved in the growth kinetics of TCam-2 cells to cisplatin, which provide some implications for studies on cisplatin and seminoma.     

Anti-oxidative and anti-aging activities of 2-O-α-glucopyranosyl-L-ascorbic acid on human dermal fibroblasts

A stable ascorbic acid derivative, 2-O-α-glucopyranosyl-l-ascorbic acid (AA-2G), was evaluated and compared with ascorbic acid for its protective effect against cellular damage and senescence induced by hydrogen peroxide (H(2)O(2)). Pretreatment with AA-2G for 72 h promoted the proliferation of normal human dermal fibroblasts (NHDF) and protected against cell damage induced by H(2)O(2). In contrast, ascorbic acid increased the proliferation and protected against cell damage, only when culture medium containing ascorbic acid was replaced every 24 h during the pretreatment period. These results suggest that the effect of AA-2G is longer-lasting compared to that of ascorbic acid. Senescence associated-β-galactosidase (SA-β-gal) activity, a classical biomarker of cellular senescence, was increased in H(2)O(2)-exposed NHDF cells, but pretreatment or posttreatment with ascorbic acid or AA-2G significantly inhibited the increase in SA-β-gal levels. AA-2G was more potent than ascorbic acid in down-regulating SA-β-gal activity. Expression of SIRT1, which has attracted attention as an anti-aging factor in recent years, was significantly decreased in H(2)O(2)-exposed NHDF cells compared to untreated cells. However, pretreatment NHDF cells with AA-2G before H(2)O(2) exposure significantly inhibited this decrease in SIRT1 expression, whereas ascorbic acid had no effect. After H(2)O(2) exposure, the expression levels of p53 and p21 were increased in NHDF cells and pretreatment with AA-2G inhibited this increase. Together, these results suggest that AA-2G protects dermal fibroblasts from oxidative stress and cellular senescence. These characteristics indicate that AA-2G could become a promising material for its anti-aging properties.     

3D TECA hydrogel reduces cellular senescence and enhances fibroblasts migration in wound healing

This study was designed to investigate the effect of 3D TECA hydrogel on the inflammatory-induced senescence marker, and to assess the influence of the gel on the periodontal ligament fibroblasts (PDLFs) migration in wound healing in vitro. PDLFs were cultured with 20 ng/ml TNF-α to induce inflammation in the presence and absence of 50 µM 3D TECA gel for 14 d. The gel effect on the senescence maker secretory associated-β-galactosidase (SA-β-gal) activity was measured by a histochemical staining. Chromatin condensation and DNA synthesis of the cells were assessed by 4′,6-diamidino-2-phenylindole and 5-ethynyl-2′-deoxyuridine fluorescent staining respectively. For evaluating fibroblasts migration, scratch wound healing assay and Pro-Plus Imaging software were used. The activity of senescence marker, SA-β-gal, was positive in the samples with TNF-α-induced inflammation. SA-β-gal percentage is suppressed (>65%, P < 0.05) in the treated cells with TECA gel as compared to the non-treated cells. Chromatin foci were obvious in the non-treated samples. DNA synthesis was markedly recognized by the fluorescent staining in the treated compared to non-treated cultures. Scratch wound test indicated that the cells migration rate was significantly higher (14.9 µm²/h, P < 0.05) in the treated versus (11 µm²/h) for control PDLFs. The new formula of 3D TECA suppresses the inflammatory-mediated cellular senescence and enhanced fibroblasts proliferation and migration. Therefore, 3D TECA may be used as an adjunct to accelerate repair and healing of periodontal tissues.     

Long-term arsenite exposure induces premature senescence in B cell lymphoma A20 cells

Chronic arsenite exposure induces immunosuppression, but the precise mechanisms remain elusive. Our previous studies demonstrated that arsenite exposure for 24 h induces G0/G1 arrest in mouse B lymphoma A20 cells and the arrest is caused through induction of cyclin-dependent kinase inhibitor p16^INK4a followed by accumulation of an Rb family protein, p130. In this study, we further investigated the consequences of long-term arsenite exposure of A20 cells. The results demonstrated that exposure to 10 μM sodium arsenite up to 14 days induces a great increase in G0/G1 arrest, irreversible cell growth suppression, cellular morphological changes and positive staining for senescence-associated β-galactosidase. The long-term arsenite exposure also induced up-regulation of p16^INK4a followed by robust accumulation of p130 and activation of the p53 pathway. Knockdown experiments with siRNA showed that p130 accumulation is essential for cell cycle arrest by long-term arsenite exposure. Since p16^INK4a and the p53 pathway are known to be activated by DNA damage, we investigated the involvement of DNA damage formation by long-term arsenite exposure. We found that a variety of DNA repair-related genes were significantly down-regulated from 24 h of arsenite exposure and activation-induced cytidine deaminase was greatly up-regulated after long-term arsenite exposure. Consistent with these findings, long-term arsenite exposure increased a DNA double-strand break marker, γ-H2AX and increased mutation frequency in a Bcl6 gene region. These results revealed that long-term arsenite exposure induces premature senescence through DNA damage increase and p130 accumulation in lymphoid cells.     

Inhibitory effects of juglanin on cellular senescence in human dermal fibroblasts

Cellular senescence contributes to tissue and organismal aging, tumor suppression and progress, tissue repair and regeneration, and age-related diseases. Thus, aging intervention might be a promising target for treatment and prevention of diverse age-related diseases. In the present study, we investigated whether juglanin purified from the crude extract of Polygonum aviculare exerted inhibitory activity against cellular senescence in human dermal fibroblasts (HDFs). Juglanin decreased senescence-associated β-galactosidase activity (SA-β-gal) and the level of reactive oxygen species in senescent cells induced by adriamycin treatment. Juglanin also repressed SA-β-gal activity in HDFs under replicative senescence. These results suggest that juglanin represses cellular senescence in HDFs and might be useful for the development of dietary supplements or cosmetics that alleviate tissue aging or age-related diseases.     

M1 macrophages accelerate renal glomerular endothelial cell senescence through reactive oxygen species accumulation in streptozotocin-induced diabetic mice

Cellular senescence is a fundamental aging mechanism leading to tissue dysfunction. Accumulation of senescent cells is observed in the context of diabetes, which plays an important role in the pathogenesis of diabetes and its complications. Macrophages, the most prevalent leucocytes found in diabetic kidney, have been implicated in the modulation of cellular senescence; however, their role and mechanism in cellular senescence of diabetic kidney have not been determined. In this study, we found trends of cellular senescence in the glomeruli of streptozotocin-induced diabetic mice. The onset of glomerular senescence was confirmed by increased SA-β-gal staining, the upregulation of p16INK4a, p21, and p53 protein levels and the increased expression of SASP RNA. The senescent cells in the glomeruli were mainly endothelial cells. We next confirmed that M1 macrophages accumulated in the glomeruli, occurred just shortly before glomerular senescence. Therefore, we examined whether M1 macrophage accumulation is associated with glomerular endothelial cell senescence. Thus, an in vitro co-culture model was established using human renal glomerular endothelial cells (HRGECs) and M1-polarized THP-1 macrophages. Indeed, M1 macrophages induced senescence in HRGECs. Furthermore, intracellular ROS levels and p38 MAPK signalling activation were significantly increased in HRGECs and reducing ROS generation significantly abolished M1 macrophage-mediated endothelial senescence and p38 MAPK activation, suggesting that M1 macrophage-mediated endothelial senescence is largely dependent on ROS. Thus, our results demonstrate that kidney M1 macrophage accumulation is in connection with endothelial cell senescence and strategy to modulate M1 macrophages accumulation is promising to be a new target for immunotherapy for diabetic kidney disease and other age-related diseases.     

5-Methoxyflavanone induces cell cycle arrest at the G2/M phase, apoptosis and autophagy in HCT116 human colon cancer cells

Natural flavonoids have diverse pharmacological activities, including anti-oxidative, anti-inflammatory, and anti-cancer activities. In this study, we investigated the molecular mechanism underlying the action of 5-methoxyflavanone (5-MF) which has a strong bioavailability and metabolic stability. Our results show that 5-MF inhibited the growth and clonogenicity of HCT116 human colon cancer cells, and that it activated DNA damage responses, as revealed by the accumulation of p53 and the phosphorylation of DNA damage-sensitive proteins, including ataxia-telangiectasia mutated (ATM) at Ser1981, checkpoint kinase 2 (Chk2) at Thr68, and histone H2AX at Ser139. 5-MF-induced DNA damage was confirmed in a comet tail assay. We also found that 5-MF increased the cleavage of caspase-2 and -7, leading to the induction of apoptosis. Pretreatment with the ATM inhibitor KU55933 enhanced 5-MF-induced γ-H2AX formation and caspase-7 cleavage. HCT116 cells lacking p53 (p53^−/−) or p21 (p21^−/−) exhibited increased sensitivity to 5-MF compared to wild-type cells. 5-MF further induced autophagy via an ERK signaling pathway. Blockage of autophagy with the MEK inhibitor U0126 potentiated 5-MF-induced γ-H2AX formation and caspase-2 activation. These results suggest that a caspase-2 cascade mediates 5-MF-induced anti-tumor activity, while an ATM/Chk2/p53/p21 checkpoint pathway and ERK-mediated autophagy act as a survival program to block caspase-2-mediated apoptosis induced by 5-MF.     

Induction of cell cycle arrest by GL331 via triggering an ATM-dependent DNA damage response in HepG2 cells

GL331, a topoisomerase II inhibitor, has been found to trigger DNA damage response (DDR) to induce cell cycle arrest. However, the underlying mechanism has not yet been fully understood. This study investigated the molecular mechanism involved in the GL331-induced cell cycle arrest via DDR in human hepatocellular carcinoma HepG2 cells. As a result, GL331 could induce S arrest and up-regulate the phosphorylation of the histone H2AX variant (γ-H2AX). Ataxia telangiectasia mutated protein kinase (ATM) was activated by GL331 through its autophosphorylation at Ser1981, which led to the activation of DNA damage signaling pathways including p53/p21 and Chk2/Cdc25A cascades. The DNA damage cascades triggered by GL331 finally induced the inactivation of cyclin A/Cdk2 complexes to some extent. These phenomena could be reversed by ATM siRNA, followed by a partial disruption of S arrest. The present results suggested that the S arrest induced by GL331 via DDR was in an ATM-dependent manner to some degree.     

Down-regulation of Polη expression leads to increased DNA damage,apoptosis and enhanced S phase arrest in L-02 cells exposed to hydroquinone

DNA polymerase eta (Polη), the product of the xeroderma pigmentosum variant gene, is required for translesion DNA synthesis, and plays a pivotal role in preventing genome instability after DNA damage induced by genotoxic agents. Studies have previously suggested a link between Polη and susceptibility to hydroquinone (HQ)-induced toxicity. To further address the role of Polη in the response of L-02 cells to HQ, we employed RNA interference to silence Polη expression in L-02 cells and examined the susceptibility of these Polη-deficient cells to the toxic effects of HQ. In this study, cell survival rate was determined using the MTT assay, DNA damage was determined by the Comet assay, apoptosis and cell cycle distribution were determined using flow cytometry, the mRNA expression levels of Polη were determined by real-time PCR, and the protein expression levels of Polη and γ-H2AX were determined by Western blot, γ-H2AX foci were visualized by confocal laser scanning fluorescence microscopy after cells were exposed to HQ at various concentrations for 24 h in vitro. The results showed that stable Polη-knockdown cells were successfully constructed and more than 80% inhibition of Polη expression was confirmed. The results also showed that down-regulation of Polη led to a decrease in cell proliferation and an enhanced susceptibility to HQ-induced cytotoxicity. Polη-deficient cells were 2-fold more sensitive to HQ when compared with nonspecific siRNA control cells. Moreover, Polη-silenced L-02 cells treated with HQ displayed an increased level of DNA double-strand breaks as measured by olive tail moment, and an elevated DNA damage response as indicated by the induction of γ-H2AX. In addition, knockdown of Polη resulted in more enhanced apoptosis and more pronounced S phase arrest following HQ treatment. Together, these results show that Polη plays an important role in the response of L-02 cells to HQ-induced DNA damage.