丁酸钠对人乳腺癌细胞株MCF-7细胞增殖及p27^kip1蛋白表达影响的研究

目的：通过观察组蛋白去乙酰化酶抑制剂（histon—deacetylase inhibitors，HDACIs）丁酸钠（sodium butyrate，NaB）对人乳腺癌细胞株MCF-7细胞的增殖影响以及p27^kip1蛋白表达改变，探讨NaB调控乳腺癌细胞增殖的分子机制。方法：乳腺癌MCF-7细胞经不同浓度NaB作用后，相差显微镜观察细胞形态变化和细胞增殖情况，流式细胞仪分析细胞周期分布，免疫组化检测p27^kip1蛋白表达。结果：NaB对MCF-7细胞有显著的增殖抑制作用，呈时间剂量依赖性，处理后的MCF-7细胞出现凋亡形态变化；细胞周期阻滞于（G0／G1期，NaB2 mmol／L组G0／G1，期达（62．2±2．2）％，4mmol／L组G0/G1，期达（78．1±3．8）％，空白组G0／C0期达（53．1±2．4）％，P〈0．05；p27蛋白表达水平上调。结论：NaB可抑制乳腺癌细胞的生长，该作用可能与p27蛋白表达增加有关。     

低剂量率照射下肿瘤细胞抑癌基因表达和细胞凋亡研究进展

低剂量率照射能够增强p53、p21等抑癌基因的表达,并可通过肿瘤细胞G2-M期阻滞和bcl-2等基因的改变引起细胞凋亡,从而达到治疗肿瘤的目的.     

低剂量率照射下肿瘤细胞抑癌基因表达和细胞凋亡研究进展

低剂量率照射能够增强p53、p21等抑癌基因的表达,并可通过肿瘤细胞G2-M期阻滞和bcl-2等基因的改变引起细胞凋亡,从而达到治疗肿瘤的目的.     

食管癌细胞照射后细胞周期及相关蛋白表达的变化

目的：探讨食管癌细胞照射后细胞周期、细胞凋亡及其相关蛋白表达的变化。方法：食管癌细胞株TE-1和TE-13照射2、5、10、15Gy后，应用流武细胞仪分别检测照射后6、24和48h细胞周期和凋亡指数变化、Western blot检测细胞周期相关蛋白的表达。结果：2、5、10、15Gy照射0～48h，TE-1和TE-13细胞均出现明显剂量依赖性的G2／M期阻滞和解除变化；5～15Gy照射后48h，TE-13细胞在G2／M期阻滞逐渐解除时伴随着细胞凋亡的明显增加，而TE-1细胞凋亡不增加。2株细胞胞浆CHK2-p68磷酸化水平均呈随照射后时间延长而出现时相性变化，但与照射剂量无关；而CHK1、CHK2、CHK1-p345和CDK1蛋白表达均无明显变化。15Gy照射后24h，TE-13细胞胞浆中eyelin B1表达下降而TE1细胞中无明显变化。结论：病理不同分化的食管癌细胞照射后细胞周期、细胞凋亡以及细胞周期相关蛋白表达变化不尽相同。     

60Coγ射线对肝癌细胞株p27kip1表达及其分布的影响

最近研究表明电离辐射可以改变细胞周期的进程，而且不同的辐射敏感性细胞辐射后存在不同细胞周期变化规律。已有的研究发现^60Coγ射线对于卵巢癌细胞(A2780)和血管平滑肌细胞(VSMCs)主要发生G1阻滞，而对白血病细胞(HL-60)主要是G2 M期阻滞。p27^kip1是一类细胞周期素依赖的蛋白激酶抑制剂，作为细胞周期负性调因子，参与细胞周期调控。最近有研究者发现细胞G2 M期阻滞p21蛋白高表达和p27^kip1蛋白的低表达共同调控，但是p27^kip1蛋白在γ射线引起的细胞周期改变过程中表达和分布的改变并不清楚。     

蛴螬粗提物对人宫颈癌HeLa细胞诱导凋亡作用及其机制

 目的 研究蛴螬粗提物对人宫颈癌HeLa细胞诱导凋亡作用，并探讨其作用机制。方法 采用流式细胞仪检测HeLa细胞的细胞周期分布相和细胞凋亡率；末端脱氧核苷酸转移酶（TdT）介导的脱氧核苷酸缺口末端标记（TdT mediated dUTP nick end labeling）TUNEL法检测凋亡细胞；通过免疫细胞化学SP法测定凋亡相关基因产物p53、Fas、bcl 2、Bax蛋白的表达情况。结果 (1)蛴螬粗提物可以诱导HeLa细胞发生凋亡，加药组出现亚二倍体峰，并且G0/G1期细胞比例显著增加（P＜0.01），而S期和G2/M期细胞比例则明显下降,将细胞阻滞在G0/G1期；（2）蛴螬粗提物作用细胞后凋亡细胞数目随时间延长而增多，凋亡指数与药物处理呈时间依赖性和剂量依赖性；(3)蛴螬粗提物作用后bcl 2、p53蛋白随提取物浓度表达均下降，Bax、Fas蛋白表达上升，四种蛋白表达各组间比较差异均有具有统计学意义（P<0.01）。结论 (1) 蛴螬粗提物对人宫颈癌HeLa细胞具有诱导凋亡作用；(2)蛴螬粗提取物诱导凋亡作用机制可能与细胞周期发生G0/G1期阻滞有关；并且通过下调bcl 2、p53蛋白表达,上调Bax、Fas蛋白表达，经由细胞凋亡的死亡受体通路和线粒体通路完成凋亡的启动和执行。     

电离辐射对肺癌A549细胞凋亡及细胞周期的影响

[目的]阐明电离辐射对肺癌A549细胞凋亡、细胞周期及Fas蛋白的影响。[方法]采用流式细胞术检测X射线照射对A549细胞周期、细胞凋亡及Fas蛋白表达的影响。[结果]1．0-4．0GyX射线照射后,G0／G1期细胞数与对照组相比明显减少（P〈0．05）。0．5～4．0GyX射线照射后,G2／M期细胞数与对照组相比明显增多（P〈0．05）。各照射组细胞凋亡率和Fas蛋白表达与对照组相比均明显增高,其中均以4．0GyX射线照射后增高最为显著。[结论]X射线能诱导A549细胞周期发生G2期阻滞、细胞凋亡,并诱导Fas蛋白表达增高,且在一定范围内存在时间和剂量依赖关系。     

电离辐射对食管癌细胞周期及MDC1、53BP1蛋白表达的影响

目的 观察60Co γ射线照射后食管癌细胞周期、细胞凋亡及其相关蛋白表达的变化,为食管癌放射治疗、靶向治疗提供理论依据。方法 食管癌细胞株TE 13进行不同剂量（0、1、2、5、10、15Gy）照射后,应用流式细胞术分别检测照射后1、2、12、24和48h细胞周期和凋亡指数的变化;同时采用Western blot方法检测MDC1和53BP1蛋白表达情况。结果 TE 13细胞照射后12、24、48h,TE 13细胞的G0/G1期、G2/M期和S期的变化呈现明显剂量依赖性,1Gy和2Gy照射后12h,细胞G2/M期阻滞开始出现;5、10、15Gy照射后24h,细胞G2/M期阻滞最为明显,与对照组（0Gy组）相比,差异具有统计学意义（P<0.05）;15Gy照射后12h、24、48h,TE 13细胞的凋亡增加非常显著（P<0.01）;不同剂量照射后1、2、24h,TE 13细胞MDC1和53BP1蛋白表达未见明显变化（P>0.05）。结论 TE 13细胞经不同剂量放射线照射后,细胞周期出现明显的G2/M期阻滞,细胞凋亡指数明显增加,但对MDC1和53BP1蛋白表达未见明显影响。     

PPARγ的配体15d-PGJ2对人类胃癌细胞生长的影响

目的：探讨过氧化物酶体增殖物激活受体γ（peroxisome proliferator activated receptor γ，PPARγ）的配体15-脱氧前列腺素J2（15-deoxy-Δ^12,14-prostaglandin J2，15d—PGj2）对人类胃癌MGC803细胞生长的影响及其机制。方法：RT—PCR检测PPARγ和survivin mRNA，Western blot检测PPARγ、survivin、S期激酶相关蛋白2（S-phase kinase-assoeiated protein2，Skp2）和p27蛋白;MTT法及流式细胞术检测细胞增殖、凋亡及细胞周期分布；Hoechst33342染色观察细胞凋亡的形态学变化。结果：PPARγmRNA和蛋自在MGC803细胞均表达。15d-PGJ2作用MGC803细胞24h后，5、10、20、30、40μmol／L组的增殖抑制率和凋亡率均高于0μmol／L组（P〈0．001），且随浓度的增加而升高。30μmol／L组的MGC803细胞增殖抑制率和凋亡率，随时间的延长而升高。G0／G1期细胞比例，30μmol／L组明显高于0μmol／L组（P〈0．001）;S和G2／M期细胞比例，30μmol／L组均明显低于0μmol／L组（分别为P〈0．001，P〈0．01）。随15d0PGJ2作用MGC803细胞浓度的增加，survivin mRNA和蛋白及Skp2蛋白的表达均降低，p27蛋白表达升高。结论：15d-PGJz抑制人胃癌MGC803细胞的增殖、诱导其凋亡并将其阻滞在G0／G1期，survivin和Skp2表达下调及p27表达上调在这个过程中起重要作用，提示15d—PGJ2可能对治疗胃癌有效。     

p57^kip2蛋白：晚期肝癌的预后因素

目的：检测细胞周期抑制因子p57^kip在肝癌（HCC）中的表达水平,探讨它与各种临床病理因素、增殖凋亡的关系及其预后价值。方法：用免疫组织化学方法检测40例肝癌组织、40例癌旁组织和15例正常肝脏组织中p57^kip的表达水平;用DNA缺口末端标记技术检测肝癌组织中细胞凋亡水平。结果：p57^kip在肝癌组织中的阳性率42.5%,显著低于癌旁肝组织（72.5%）和正常肝脏组织（93.3%）（P〈0.05）,p57^kip的缺失表达与晚期肝癌和肝外转移有关（P〈0.05）。HCC组织中存在增殖凋亡异常（P〈0.05）。p57^kip的阳性表达与HCC组织低增殖有关（P〈0.05）,与细胞凋亡无关（P〉0.05）。TNM分期、肝外转移,AFP水平与p57^kip蛋白表达与HCC预后有关（P〈0.05）,且p57^kip和临床分期是HCC的独立预后因素（P〈0.05）。结论：p57^kip参与了肝癌的发生发展,可用于预测晚期肝癌预后。     

放射线对鼻咽癌细胞周期阻滞、凋亡和抑癌基因p57Kip2表达的影响

Objective： To study cell cycle retardation, apoptosis and the expression of antioncogene p57^kip2 by radioactive rays in nasopharyngeal carcinoma cells. Methods： Cell cycle retardation, apoptosis and cell survival rate induced by radioactive rays were tested by the methods of flow cytometry and MTT method. The expression of antioncogene p57^kip2 was detected by immunohistochemistry and Western blot. Results： After irradiation, G1 phase had no obvious retardation, S phase showed transient delay. There was a positive correlation between irradiation dosage and retardation strength in G2/M phase （P 〈 0.01）. Peak value appeared at 24 h after 12 Gy irradiation, then decreased. There was a positive correlation between apoptosis incidence and irradiation dosage or after-irradiation time extention （P 〈 0.01）. There was a negative correlation between cell survival rate and irradiation dosage or apoptosis incidence （P〈 0.01）. The expression of p57^kip2 protein was up-regulated along with the prolongation of time and dosage after irradiation （P 〈 0.01）. Conclusion： G2/M phase arrest, apoptosis and the up-regulation of the expression of p57^kip2 protein all can reflect predict the radiosensitivity of nasopharyngeal carcinoma cells.     

放射线对鼻咽癌细胞周期阻滞、凋亡和抑癌基因p57Kip2表达的影响

Objective:To study cell cycle retardation.apoptosis and the expression of antioncogene p57kip2 by radioactive rays in nasopharngeal carcinoma cells.Methods:Cell cycle retardation.apoptosis and cell suwival rate induced by radioactive rays were tested by the methods of flow cytometry and MTT method.The expression of antioncogene p57kip2 was detected bv immunohislochemistry and Western blot.Results:After irradiation,G1 phase had no obvious retardation,S phase showed transient delay.There was a positive correlation between irradiation dosage and retardation strength in G2/M phase(P＜0.01).Peak value appeared at 24 h after 12 Gy irradiation,then decreased.There was a positive correlation between apoptosis incidence and irradiation dosage or after-irradiation time extention(P＜0.01).There was a negative correlation between cell survival rate and irradiation dosage or apoptosis incidence(P＜0.01).The expression of p57 kjP2 protein was up-regulated along with the prolongation of time and dosage after irradiation(P＜0.01).Conclusion:G2/M phase arrest,apoptosis and the up-regulation of the expression of p57kiP2 protein all can reflect predic the radiosensitivity of nasopharyngeal carcinoma cells.     

Research on cell cycle retardation,apoptosis and the expression of antioncogene p57<Superscript>Kip2</Superscript> by radioactive rays in nasopharyngeal carcinoma cell line in vitro

Objective To study cell cycle retardation, apoptosis and the expression of antioncogene p57^kip2 by radioactive rays in nasopharyngeal carcinoma cells. Methods Cell cycle retardation, apoptosis and cell survival rate induced by radioactive rays were tested by the methods of flow cytometry and MTT method. The expression of antioncogene p57^kip2 was detected by immunohistochemistry and Western blot. Results After irradiation, G1 phase had no obvious retardation, S phase showed transient delay. There was a positive correlation between irradiation dosage and retardation strength in G2/M phase (P < 0.01). Peak value appeared at 24 h after 12 Gy irradiation, then decreased. There was a positive correlation between apoptosis incidence and irradiation dosage or after-irradiation time extention (P < 0.01). There was a negative correlation between cell survival rate and irradiation dosage or apoptosis incidence (P < 0.01). The expression of p57^kip2 protein was up-regulated along with the prolongation of time and dosage after irradiation (P < 0.01). Conclusion G2/M phase arrest, apoptosis and the up-regulation of the expression of p57^kip2 protein all can reflect predict the radiosensitivity of nasopharyngeal carcinoma cells.     

抑制ATM表达致鼻咽癌细胞CNE1辐射增敏的细胞周期阻滞研究

背景与目的:细胞周期调控是决定细胞辐射敏感性的决定性因素之一。共济失调毛细血管扩张症突变基因(ataxia-telangiectasia mutant,ATM)功能与细胞DNA损伤修复、细胞周期检查点调控密切相关。我们前期研究通过反义RNA抑制ATM基因表达可增加鼻咽癌细胞系CNE1辐射敏感性,本研究拟探讨其辐射增敏的细胞周期阻滞调控机制。方法:ATM反义组细胞CNE1/pDOR-atm及对照组细胞CNE1/pDOR经2Gy、5GyX线照射后不同时间点(1h、4h、8h、24h、48h)收获,应用流式细胞仪(flowcytometer,FCM)检测各细胞周期百分比及凋亡率。结果:两组细胞X线照射后均未出现明显G1期阻滞和细胞凋亡,但分别在照射后1h、4h、8h出现明显S期阻滞,24h、48h出现明显G2期阻滞,其中反义组S期细胞百分率总均数水平低于对照组(P<0.05),而G2/M期细胞百分率总均数水平高于对照组(P<0.05)。结论:反义RNA抑制ATM表达致CNE1辐射增敏的细胞周期调控机制可能与减少S期细胞比例,增加G2/M期细胞比例有关,与G1期阻滞和细胞凋亡的调控无关。     

蛋白酶体抑制剂MG132诱导HL-60细胞凋亡前G2/M期阻滞及机制

背景和目的:蛋白酶体(proteasome)抑制剂能够诱导多种肿瘤细胞凋亡,是一种潜在的有应用前景的抗肿瘤剂.本研究旨在探讨蛋白酶体抑制剂MGl32(Z-Leu-Leu-Leu-CHO)诱导白血病细胞HL-60凋亡和C2/M期阻滞的机制.方法:采用荧光显微镜观察、流式细胞术和免疫印迹研究测定MG132诱导HL-60细胞凋亡和周期阻滞及机制.结果:2μmol/L的MG132能够有效地诱导HL-60细胞凋亡,用药后24 h就显现有细胞凋亡;在MG132诱导HL-60细胞凋亡出现之前有一个明显的G2/M期阻滞,加MG132后12 h时G2/M期时相百分比为63.42±2.02;24 h时加MG132组细胞凋亡为16.67±1.48,与对照组G2/M期时相百分比为7.29±3.01及细胞凋亡为0相比,两者之间有显著性差别(P＜0.01);咖啡因CAF能够减少MG132诱导HL-60细胞出现的G2/M期阻滞,同时也减少凋亡细胞的比例;细胞周期检查点的负调控因子p21waf/cip1蛋白在加MG132处理后3 h有明显的表达,但并未能检测到p53和p27蛋白.结论:MG132诱导HL-60细胞凋亡之前有一个明显的G2/M期阻滞,p21蛋白表达明显上调提示:是p21waf/cip1而不是p53或其同源蛋白参与了其中的调控.     

p27kip1的过表达对肾癌细胞增殖及凋亡的影响

目的:研究外源性 p27kip1 基因对肾癌细胞周期、细胞凋亡及增殖的影响。方法:将含p27cDNA的质粒在脂质体介导下在体外转染肾癌GRC 1细胞,Western Blot、FCM及MTT检测分析外源性 p27kip1 蛋白在细胞内的表达,观察其对细胞周期、凋亡及细胞增殖的影响。结果:体外转染 GRC 1 细胞 48 h 后, p27 蛋白在p27kip1转染后的 GRC 1 细胞中高表达。FCM检测表明,细胞停滞于 G1 期,实验组 G1 期细胞占66 9%,并出现亚G1 凋亡峰;而空白对照组和转染空载体组 G1 期细胞分别为 32 2% 和33 8%。MTT 法检测表明,转染 p27cDNA 后,实验组细胞增殖明显受抑。结论: p27kip1 基因在体外转染GRC 1细胞并过表达p27kip1蛋白,抑制细胞由G1 期向 S期过渡,从而抑制细胞增殖,诱导细胞凋亡。     

Role of p53 in G2/M cell cycle arrest and apoptosis in response to gamma-irradiation in ovarian carcinoma cell lines

We investigated the cell cycle and apoptotic response to irradiation in 4 human ovarian carcinoma cell lines, i.e., PA-1, Caov-3, SK-OV-3, and ES-2. Cell lines were also analysed for their p53 and Bax expression to address the relationship with cell cycle and apoptotic response. Apoptosis was examined by flow cytometric measurement of annexin V binding and by determination of cytoplasmic histone-associated DNA fragments with a photometric enzyme immunoassay. Cell cycle analyses were performed on the basis of flow cytometry. p53 and Bax protein expression was examined by immunocytochemistry in untreated cells and after irradiation. p53 cDNA sequencing and a functional yeast-based assay (FASAY) were performed to determine the p53 mutational status. All cell lines exhibited a dose-dependent G2/M arrest. No arrest in G1 was seen. A strong correlation was found between the G2/M arrest and the induction of apoptosis. PA-1, the only cell line found to express wild-type p53, showed the highest susceptibility to accumulate in G2/M and the strongest apoptotic response after irradiation. In this cell line irradiation resulted in an unequivocal accumulation of p53 protein and in an increased expression of Bax protein. Caov-3, lacking wild-type p53, showed upregulation of Bax expression after irradiation. Caov-3 proved to be relative sensitive to apoptosis compared to SK-OV-3 and ES-2. These two cell lines were found to be p53 mutated in sequence analysis and irradiation had no effect on the expression of p53. No change in Bax expression was seen in ES-2, while SK-OV-3 exhibited decreased Bax protein levels after irradiation. Our data suggest that the G2/M arrest is an important component of the pathway leading from irradiation-induced DNA damage to apoptosis in the examined cell lines. The G2/M arrest and associated apoptosis found in the examined cell lines does not necessarily require wild-type p53, although wild-type p53 and possibly Bax may contribute to a maximum response to irradiation. Two independent mechanisms, p53-dependent and p53-independent, are suggested in the examined cell lines.     

TgN(p53mt_LMP1)/HT小鼠鼻腔和鼻咽黏膜上皮细胞增殖与凋亡相关基因表达的关系

背景与目的： 探讨TgN(p53mt_LMP1)/HT小鼠鼻腔和鼻咽黏膜上皮癌前病变发生与细胞周期分布,凋亡相关基因bax、bcl_2和增殖相关基因PCNA的表达水平及它们与p53mt基因表达的相关关系。 材料与方法： HE染色法观察G4代12月龄TgN(p53mt_LMP1)/HT转基因阳性和阴性小鼠鼻腔和鼻咽黏膜上皮病理组织学变化,流式细胞术测定细胞周期分布特点,免疫组织化学法检测组织中p53mt、bax、bcl_2和PCNA表达水平,综合分析其相关性。 结果： 转基因阴性小鼠和阳性小鼠鼻腔或鼻咽黏膜上皮癌前病变发生率分别为0和63.64％(P<0.01)。与转基因阴性小鼠比较,转基因阳性小鼠鼻腔和鼻咽黏膜上皮组织G0/G1期细胞数量减少,S期、G2/M期细胞数量增多,细胞增殖指数增高(P均<0.01),p53mt、bcl_2和PCNA表达水平显著增高(P<0.01),bax表达水平显著降低,bcl_2/bax比值升高(P<0.01)。 结论： TgN(p53mt_LMP1)/HT转基因阳性小鼠p53mt的表达可引起bax表达抑制,bcl_2表达水平增高,bcl_2/bax比值升高,PCNA表达增强,由此导致细胞凋亡活性降低,细胞增殖活性升高,细胞转化机率增加,可能与鼻腔或鼻咽黏膜上皮癌前病变有密切关系。     

Schedule-dependent cytotoxicity of SN-38 in p53 wild-type and mutant colon adenocarcinoma cell lines

In this study the effects of SN-38 on colon adenocarcinoma cell lines expressing wild-type p53 (LS174T) or mutant non-functional p53 (HT29) have been investigated. On exposure to SN-38, HT29 cells rapidly progressed through G1 and S and arrested in G2/M. Release and concomitant increase in apoptosis after 48 h was concentration- and time-dependent (P < 0.001), being more rapid at higher concentrations, but reaching plateau at 10 ng ml(-1) with prolonged exposure. LS174T cells showed only a small increase in apoptosis, and only at high concentrations (50-100 ng ml(-1)). The main effect of SN-38 in LS174T cells was prolonged cell cycle arrest, which was independent of concentration. Arrest occurred in all phases of the cell cycle, with the distribution depending on concentration (P < 0.001) and not duration (P > 0.05). With increasing concentration, LS174T cells arrested in G2/M, S and G1. Cell cycle arrest was coincident with increased p53 expression in each phase of the cell cycle. Expression in G1 increased with time and concentration (P < 0.001, P = 0.01 respectively)whereas in S and G2/M p53 expression increased only with time (P< 0.001). Dose-dependent p53-associated G1 arrest, in the absence of DNA synthesis indicates an additional cytotoxic mechanism for SN-38, which requires higher concentrations than the S phase mechanism, and detection of which seems to involve p53. For incubations with the same ED (exposure x duration), apoptosis in HT29 cells was significantly higher for prolonged exposure to lower concentrations, whereas in LS174T cells there was a trend towards increased apoptosis with shorter exposures to higher concentrations, indicating a schedule effect of SN-38. Although expression of wild-type p53 leads to a more rapid induction of apoptosis, SN-38 cytotoxicity was generally greater in cells with mutant p53, as wild-type cells escaped apoptosis by p53 associated prolonged cell cycle arrest. Thus, pulsed schedules with higher doses may be more effective in cells expressing wild-type p53, whereas continued exposure with protracted schedules may be more active in cells expressing mutant p53.     

Quercetin-induced growth inhibition and cell death in nasopharyngeal carcinoma cells are associated with increase in Bad and hypophosphorylated retinoblastoma expressions

Nasopharyngeal carcinoma is a common cancer in South-East Asia, especially among people of Chinese origin. In this report, we investigate the effects of quercetin on the growth of wild-type and mutant p53 nasopharyngeal carcinoma cell lines, HK1 and CNE2 respectively. The wild-type p53 HK1 was more susceptible to growth inhibition by quercetin than the mutant p53 CNE2. The ID50 values for HK1 and CNE2 were 35.0 and 54.5 microM respectively. Cell growth arrest was initiated by the up-regulation of retinoblastoma gene expression, resulting in cell cycle arrest in either the G2/M or G0/G1 phase at 14.8 and 52.1 microM quercetin respectively regardless of the p53 status. Flow cytometry experiments revealed that quercetin-induced apoptosis during the first 24 h followed by necrosis in both HK1 and CNE2. Western blot experiments confirmed that cytotoxic killing of HK1 and CNE2 by quercetin was mediated by the up-regulation of pro-apoptotic protein Bad, caspase-3 and -7, resulting in cell death by apoptosis. Our study demonstrates that quercetin inhibits cell growth of nasopharyngeal carcinoma cell lines HK1 and CNE2 by inhibiting cell cycle progression to S phase. Quercetin is also able to induce apoptosis and necrosis in these cells regardless of the p53 status.