曲古抑菌素A对肾癌细胞系GRC-1生长的抑制作用

目的 研究组蛋白去乙酰化酶(HDAC)抑制药曲古抑菌素A(TSA)对肾癌GRC-1细胞生长的影响及其作用机制. 方法使用TSA处理GRC-1细胞. 噻唑蓝(MTT)法检测细胞生长;流式细胞仪分析细胞凋亡及细胞周期;Western blot免疫印迹分析p53,p21和bcl-2表达. 结果 TSA能明显抑制GRC-1细胞的增殖,且具有明显的剂量依赖性;TSA处理72 h的GRC-1细胞早期凋亡率明显提高,G0/G1期细胞比例显著升高,S期细胞比例显著降低. TSA能够明显下调bcl-2的表达,上调p21的表达,而对p53的没有显著影响. 结论TSA可以通过诱导肾肿瘤细胞的凋亡和周期阻滞而抑制癌细胞生长;其发生机制可能与下调抗凋亡基因bcl-2和上调肿瘤抑制基因p21的表达有关,TSA可能依赖非p53途径调控p21的表达.     

姜黄素体内外逆转结肠癌的5-氟尿嘧啶耐药研究及机制探讨

摘要：目的 探究姜黄素在体内外对结肠癌5-氟尿嘧啶（5-FU）耐药的逆转作用及其相关机制。 方法 以SW480结肠癌细胞为亲代细胞,构建5-FU耐药细胞株SW480R,采用MTT法检测SW480R细胞的耐药指数以及不同浓度的姜黄素对SW480R细胞增殖能力的影响;流式细胞术检测姜黄素对SW480R细胞周期和凋亡的影响;Western blot检测姜黄素对SW480R细胞上皮-间充质转化（epithelial-mesenchymal transition, EMT）相关蛋白以及Wnt信号通路相关蛋白的影响;采用裸鼠移植瘤模型检测肿瘤体积变化情况,计算姜黄素的体内抑瘤率,Western blot检测肿瘤组织中相关蛋白变化。结果 SW480R的耐药指数为12.16,姜黄素能够剂量依赖性地抑制SW480R细胞的增殖,阻滞SW480R细胞周期于G0/G1期,以及诱导SW480R细胞凋亡;Western blot结果表明姜黄素能够在体内外抑制EMT和Wnt信号通路的活性;体内实验表明姜黄素能够有效抑制裸鼠移植瘤的生长。结论 姜黄素能够在体内外逆转结肠癌的5-FU耐药,其机制可能是通过调控Wnt信号通路从而抑制EMT的发生。     

紫杉醇对U373细胞周期阻滞及增殖抑制的机制研究

目的研究紫杉醇(PTX)诱发神经胶质瘤U373细胞的周期阻滞和增殖抑制的相关机制。方法 MTT检测细胞增殖抑制率,流式细胞术检测细胞周期分布,免疫细胞荧光化学观察细胞形态学变化,RT-PCR和Western blot检测细胞周期相关CyclinB1、CyclinD1、CDK1、CDK2和p53的表达变化。结果 PTX可以明显抑制U373细胞的增殖活性,抑制作用呈时间浓度依赖性;细胞周期分析显示,实验组细胞G2/M期比例增高;细胞免疫荧光检测实验组细胞阻滞于有丝分裂期;RT-PCR和Western blot显示,PTX可以增加CDK1和CyclinB1表达,降低CyclinD1表达(P<0.05),而对CDK2无明显影响。结论 PTX能够抑制神经胶质瘤U373细胞增殖,引起有丝分裂期阻滞,诱导细胞凋亡,与其细胞周期相关蛋白表达水平密切相关。     

二烯丙基二硫抑制SW480细胞系生长增殖的相关蛋白质分子鉴定

目的应用前期比较蛋白质组学筛出的部分差异表达蛋白质分子,进行进一步分析与鉴定。方法采用MTT法,观察不同浓度和作用时间DADS对SW480细胞的生长抑制作用;使用流式细胞仪,分析50 mg.L-1DADS对SW480细胞的周期分布的影响;运用Western blot方法,分析50 mg.L-1DADS处理SW480细胞系后泛肽和FKBP的表达水平。结果MTT法显示,DADS能明显抑制SW480细胞系生长增殖,呈浓度和时间依赖性,SW480细胞系经不同浓度DADS处理后,生长增殖速度明显减慢。流式细胞仪分析结果显示,50 mg.L-1DADS将SW480细胞阻滞在G2/M期。应用Western blot分析结果显示,50 mg.L-1DADS处理SW480细胞48 h,泛肽表达较对照组增强,而FKBP的表达明显降低,差异均为2倍以上。结论DADS抑制SW480细胞系生长增殖,可能与泛肽表达上调,FKBP表达下调,将细胞阻滞在G2/M期有关。     

钠钾泵抑制剂通过调节细胞周期相关蛋白的生成介导肝癌HepG2细胞周期S期阻滞与凋亡

目的研究钠泵抑制剂哇巴因(ouabain)和华蟾毒配基(cinobufogenin)对人肝癌HepG2细胞增殖的抑制作用及细胞周期的改变,初步分析其机制。方法以人肝癌细胞HepG2为靶细胞,MTT比色法检测哇巴因和华蟾毒配基对HepG2细胞增殖的影响;Hoechst 33342荧光染色检测细胞形态学变化;流式细胞术检测细胞周期;实时定量PCR和Western blot检测CyclinA1、CDK2、PCNA和p21CIP1表达的变化。结果哇巴因和华蟾毒配基可明显抑制HepG2细胞增殖,抑制作用呈时间-浓度依赖性。荧光染色显示药物处理24h后,细胞呈现典型的凋亡形态特征;细胞周期分析显示,实验组S期细胞比例升高,实时定量PCR和Western blot结果显示:哇巴因和华蟾毒配基可下调CyclinA1、CDK2和PC-NA的表达(P<0.05),上调p21CIP1的表达(P<0.05)。结论钠泵抑制剂可抑制肝癌HepG2细胞的增殖,引起细胞周期S期阻滞,诱导细胞凋亡,这与其调节细胞周期相关蛋白的生成关系密切。     

Influence of Anti-CD44 mAb A3D8 on Proliferation and Apoptosis in three Sphere-Forming Cells of Ovarian Cancer

目的:探讨抗CD44单克隆抗体(mAb)A3D8对3种卵巢癌球形体形成细胞增殖和凋亡的影响,并探讨其作用机制.方法:用MTS法检测A3D8对细胞增殖的影响;采用PI染色及流式细胞仪检测A3D8对细胞周期的影响;用Annexin V-FITC/PI凋亡检测试剂盒检测A3D8在细胞凋亡中的作用;用罗丹明123试剂盒检测A3D8对细胞线粒体膜电位的影响;并采用Western Blotting法检测A3D8作用于3种卵巢癌球形体形成细胞后,CDK2、cyclinA、Bcl-2和caspase-3的改变.结果:A3D8可抑制3种卵巢癌球形体形成细胞的增殖,且此抑制作用呈现剂量和时间依赖性;A3D8可在阻滞S期的同时降低G0/G1期比例;A3D8可促进3种细胞凋亡,与顺铂(DDP)联用,细胞凋亡率较单独使用DDP增高;A3D8的处理可导致3种细胞的线粒体膜电位损失,CDK2、cyclinA、Bcl-2蛋白表达下调,caspase-3表达上调.结论:A3D8可能是通过影响p21/CDK2/cyclinA途径阻滞细胞周期达到抑制3种卵巢癌球形体形成细胞增殖的结果,并且可通过线粒体途径促进细胞凋亡.     

抗CD44 mAb A3D8对卵巢癌球形体形成细胞增殖和凋亡的影响*

摘要 目的：探讨抗CD44单克隆抗体(mAb)A3D8对3种卵巢癌球形体形成细胞增殖和凋亡的影响,并探讨其作用机制。方法：用MTS法检测A3D8对细胞增殖的影响;采用PI染色及流式细胞仪检测A3D8对细胞周期的影响;用Annexin V-FITC/PI凋亡检测试剂盒检测A3D8在细胞凋亡中的作用;用罗丹明123试剂盒检测A3D8对细胞线粒体膜电位的影响;并采用Western Blotting法检测A3D8作用于3种卵巢癌球形体形成细胞后,CDK2、cyclinA、Bcl-2和caspase-3的改变。结果：A3D8可抑制3种卵巢癌球形体形成细胞的增殖,且此抑制作用呈现剂量和时间依赖性;A3D8可在阻滞S期的同时降低G0/G1期比例;A3D8可促进3种细胞凋亡,与DDP联用,细胞凋亡率较单独使用DDP增高;A3D8的处理可导致3种细胞的线粒体膜电位损失,CDK2、cyclinA、Bcl-2蛋白表达下调,caspase-3表达上调。结论：A3D8可能是通过影响p21/CDK2/cyclinA途径阻滞细胞周期达到抑制3种卵巢癌球形体形成细胞增殖的结果,并且可通过线粒体途径促进细胞凋亡。     

丁酸钠诱导结肠癌HT-29细胞凋亡的信号通路及对AQP3基因表达影响的研究

目的：探讨丁酸钠诱导结肠癌HT-29细胞凋亡过程的分子机理及其对水通道蛋白AQP3基因表达的影响。方法：MTT法检测不同浓度的丁酸钠对结肠癌HT-29细胞生长的影响;RT-PCR检测不同浓度的丁酸钠对细胞周期蛋白Cyclin D1、CDK4、p16和AQP3的基因表达水平,同时使用流式细胞仪检测细胞周期。结果：加入浓度超过2.5mmol/L的丁酸钠后,结肠癌HT-29细胞生长受到抑制,Cyclin D1、CDK4和AQP3的表达水平下降,p16的表达水平上调,细胞阻滞于G1/S期。结论：浓度超过2.5mmol/L的丁酸钠可以诱导结肠癌HT-29细胞凋亡,使其细胞周期阻滞于G1/S期,且这种诱导作用是剂量依赖型的,其分子通路可能是通过p16-Cyclin D1/CDK4这条信号途径,在此过程中,伴随着AQP3的基因表达水平降低。     

鱼藤素诱导肺癌细胞凋亡和细胞周期阻滞的分子机制

目的探究鱼藤素是否能够阻滞细胞周期和细胞迁移,抑制非小细胞肺癌细胞的增殖。方法鱼藤素(1. 5625、3. 125、6. 25、12. 5、25、50μmol·L~(-1))处理H1299细胞不同时间后,CCK-8法检测细胞存活率,划痕实验测定划痕宽度及愈合率;鱼藤素(1. 5、3、6μmol·L~(-1))处理24 h,PI单染测定细胞周期,Annexin V-FITC/PI双染检测凋亡率,q PCR检测药物处理后的H1299细胞中CDK4、CDK6和CCND1的基因表达情况。结果鱼藤素能够降低H1299细胞的存活率,作用24、48、72 h的IC50值分别为(5. 47±0. 97)、(4. 01±0. 45)、(2. 86±0. 19)μmol·L~(-1),并抑制细胞的迁移与愈合能力。PI单染流式细胞术检测到其能阻滞细胞周期,使细胞阻滞在G0/G1期,流式双染实验测得其可诱导细胞的凋亡,q PCR发现鱼藤素可下调CDK4、CDK6和CCND1的基因表达。结论鱼藤素可抑制H1299细胞的增殖,抑制细胞的运动迁移能力,阻滞细胞周期,诱导细胞凋亡,且鱼藤素可通过下调细胞周期调控系统中的CDK4、CDK6、CCND1基因表达来调控细胞周期,达到抗肿瘤作用。     

二烯丙基二硫下调cyclin D1和CDK4的表达诱导人鼻咽癌CNE2细胞G_1期阻滞

目的研究二烯丙基二硫(DADS)对人鼻咽癌CNE2细胞的影响及其分子机制。方法采用MTT法检测DADS对CNE2细胞增殖抑制作用;流式细胞术分析DADS对CNE2细胞周期分布的影响;运用RT-PCR和Western blot方法分析DADS作用CNE2细胞后,cyclin D1和CDK4的表达变化。结果 MTT结果显示,不同浓度DADS(90、140、240、400μmol·L-1)处理CNE2细胞48h后,生长抑制率分别为4.0%、13.8%、25.8%、51.2%;流式细胞术分析显示,DADS阻滞CNE2细胞于G1期,并呈浓度依赖性;RT-PCR和Western blot结果表明,细胞周期调控基因cyclinD1、CDK4表达下调。结论 DADS对CNE2细胞的增殖抑制作用与其阻滞细胞G1期有关,并且可能是通过抑制cyclin D1、CDK4的表达使CNE2细胞阻滞于G1期。     

Mechanism of cell cycle arrest caused by histone deacetylase inhibitors in human carcinoma cells

Inhibitors of histone deacetylase (HDAC) block cell cycle progression at G1 in many cell types. We investigated the mechanism by which trichostatin A (TSA), a specific inhibitor of HDAC, induces G1 arrest in human cervix carcinoma HeLa cells. TSA treatment induced histone hyperacetylation followed by growth arrest in G as well as hypophosphorylation of pRb. The Cdk4 kinase activity was essentially unchanged during the TSA-induced G1 arrest. On the other hand, the arrest was accompanied by down-regulation of kinase activity of Cdk2, although the total protein levels of Cdk2 and its activator Cdc25A were unaffected. Upon TSA treatment, amounts of cyclin E and the CDK inhibitor p21WAF1/Cip1 were markedly increased, while that of cyclin A was reduced. The induction of p21 and down-regulation of cyclin A correlated well with the decreased Cdk2 activity and cell cycle arrest. Furthermore, gel filtration chromatography showed the association of p21 with the cyclin E-Cdk2 complex, suggesting that the activation of Cdk2 by the enhanced expression of cyclin E is blocked by the increased p21. The elevated expression of p2 is also observed in cells treated with trapoxin and FR901228, structurally unrelated histone deacetylase inhibitors. A human colorectal carcinoma cell line lacking both alleles of the p21 gene (p21-/-) was resistant to TSA several times more than the parental line (p21+/+). These results suggest that the suppression of Cdk2 kinase activity due to p21 overexpression play a critical role in HDAC inhibitor-induced growth inhibition.     

Differential roles of p21(Waf1) and p27(Kip1) in modulating chemosensitivity and their possible application in drug discovery studies

In this study, the differential role of the cyclin-dependent kinase (CDK) inhibitors p21(Waf1) and p27(Kip1) in cell cycle regulation was proposed for use in screening natural or synthetic compounds for cell cycle-dependent (particularly M phase-dependent) antineoplastic activity. p21(Waf1) or p27(Kip1) was ectopically expressed with an ecdysone-inducible mammalian expression system in a human colon adenocarcinoma cell line. Induction of p21(Waf1) or p27(Kip1) expression inhibited the activities of CDK2 and completely arrested cells at G(1) phase of the cell cycle by p27(Kip1) and at G(1) and G(2) phases by p21(Waf1). We examined the sensitivity of these cells to several antineoplastic agents known to be cell cycle-dependent or -independent. Substantially increased resistance to cell cycle-dependent antineoplastic agents was found in the cells when the expression of p21(Waf1) or p27(Kip1) was induced. In contrast, only a desensitization to cell cycle-independent antineoplastic agents was found in the cells arrested by p21(Waf1) or p27(Kip1). Because p21(Waf1) induces an additional block at G(2) phase that inhibits cell entry into M phase, we further examined the difference between p21(Waf1)- and p27(Kip1)-induced cells in their sensitivity to D-24851, a novel M phase-dependent compound. We found that induction of p21(Waf1) after exposure of the cells to D-24851 conferred stronger resistance than did induction of p27(Kip1). Taken together, our results suggest that the differential effect of p21(Waf1) and p27(Kip1) on cell cycle regulation may be advantageous for screening chemical libraries for novel antineoplastic candidates that are cell cycle-dependent, and M phase-dependent in particular.     

Bone morphogenetic protein signalling is required for the anti-mitogenic effect of the proteasome inhibitor MG-132 on colon cancer cells

BACKGROUND AND PURPOSE: Inhibition of proteasome has been emerging as a promising approach in pathway-directed cancer therapy. Bone morphogenetic protein (BMP) signalling, which is known to be regulated by the ubiquitin-proteasome pathway in osteoblasts, plays a crucial role in the suppression of gastrointestinal carcinogenesis. Here we sought to elucidate the anti-mitogenic effect of a proteasome inhibitor in relation to BMP signalling in colon cancer. EXPERIMENTAL APPROACH: The effects of the proteasome inhibitor MG-132 on proliferation of SW1116 and HT-29 colon cancer cells were determined by [(3)H]-thymidine incorporation and colony-formation assay. The involvement of BMP signalling in the action of MG-132 was elucidated by western blot, real-time PCR, immunofluorescence and RNA interference. KEY RESULTS: MG-132 significantly suppressed the proliferation of colon cancer SW1116 and HT-29 cells. In this regard, MG-132 activated BMP signalling and this was manifested as an increase in Smad1/5/8 phosphorylation and upregulation of p21(Waf1/Cip1) and p27(Kip1) expression. Knockdown of BMP receptor II abolished Smad1/5/8 phosphorylation, the induction of p21(Waf1/Cip1) and p27(Kip1) and inhibition of cell proliferation induced by MG-132. Further analysis revealed that MG-132 upregulated the expression of BMP1 and BMP2, which are secreted members of the BMP superfamily. Moreover, the expression of Smad6, an intracellular inhibitor of BMP signalling, was suppressed by MG-132. CONCLUSIONS AND IMPLICATIONS: These findings suggest that inhibition of proteasome suppresses the proliferation of colon cancer cells via activation of BMP signalling. They also demonstrate a novel aspect of proteasome function in the regulation of colon cancer cell proliferation.     

Induction of G1 phase arrest in MCF human breast cancer cells by pentagalloylglucose through the down-regulation of CDK4 and CDK2 activities and up-regulation of the CDK inhibitors p27(Kip) and p21(Cip)

Pentagalloylglucose (5GG) is a potent and specific inhibitor of NADPH dehydrogenase or xanthine oxidase. In our previous study, we showed that 5GG was able to induce apoptosis in HL-60 cells in a time- and concentration-dependent manner via the activation of caspase-3. Recently, we found that 5GG was capable of perturbing the cell cycle of the human breast cancer cell line MCF-7. DNA flow cytometric analysis showed that 5GG exhibited the ability of blocking MCF-7 cell cycle progression at the G1 phase. The level of several G1 phase-related cyclins and cyclin-dependent kinases did not change in these cells during a 24-hr exposure to 5GG. However, the activity of cyclin E/CDK2 was decreased in a concentration- and time-dependent manner and the activity of cyclin D/CDK4 was inhibited when serum-starved synchronized cells were released from synchronization. p27(Kip) and p21(Cip), inhibitors of cyclin/CDK complexes in G1-phase, were gradually increased after 5GG treatment in a time-dependent manner and the induction of p21(Cip) was correlated with an increase in p53 levels. These results suggest that the suppression of cell-cycle progression in the G1 phase by 5GG was mediated in MCF-7 cells, at least in part, by either the inhibition of cyclin D/CDK4 and cyclin E/CDK2 activity or the induction of the CDK inhibitors p27(Kip) and p21(Cip).     

Molecular mechanism of cell cycle blockage of hepatoma SK-Hep-1 cells by Epimedin C through suppression of mitogen-activated protein kinase activation and increased expression of CDK inhibitors p21(Cip1) and p27(Kip1).

Reports elsewhere demonstrated that Epimedin C, a constituent isolated from the leaves of Epimedium sagittatum, possessed anti-tumor activity. However, its mechanism of action remains unresolved. Using SK-Hep-1 cells, a poorly-differentiated hepatoma subline, as an experimental model, we present evidence here that the anti-tumor activity of Epimedin C may involve cell cycle blockage. Immunoblotting analyses demonstrated that Epimedin C caused a decreased expression of hyperphosphorylated retinoblastoma (Rb) protein, cyclin D1, c-Myc, and c-Fos. In parallel, we measured the kinase activities and found that CDK2 and CDK4 were suppressed with commensurate increased levels of CDK inhibitors, p21(Cip1) and p27(Kip1). These data suggested that Epimedin C arrested the proliferation of these cells at G0/G1 phase through inhibition of CDK2 and CDK4 activities via an increased induction of p21(Cip1) and p27(Kip1). Alternatively, we investigated whether the anti-proliferative effect of Epimedin C on these cells might involve MAP kinase cascade. Using western blotting technique, we demonstrated that Epimedin C also selectively decreased ERK1/2 phosphorylation. Among the downstream effectors of ERK examined, we found that Epimedin C selectively decreased the expression of c-Fos, but not c-Jun. By EMSA assay, we further demonstrated that decreased c-Fos resulted in the downregulation of AP-1/DNA binding activity. Taken together, the molecular mechanisms of anti-tumor activity of Epimedin C may be proceeded by the combined effects of the cell cycle blockage via either the inhibition of CDK2 and CDK4 activities, with commensurate increase in their inhibitors, p21(Cip1) and p27(Kip1) or negatively modulates the ERK/c-Fos/AP-1 signaling pathway.     

The histone deacetylase inhibitor MS‐275 induces p21WAF1/Cip1 expression in human Hep3B hepatoma cells

MS‐275 is a novel synthetic benzamide derivative histone deacetylase (HDAC) inhibitor, that has demonstrated antiproliferative activity in a variety of in vitro human cancer cell lines including breast, colon, lung, myeloma, ovary, pancreas, prostate, and leukemia. Currently, little information is available concerning the effects of MS‐275 on liver cancer cells. In the current study, MS‐275 was found to have potent actions against human hepatoma Hep3B cells including inhibition of cell proliferation and induction of apoptosis. MS‐275 selectively up‐regulated a cyclin‐dependent kinase inhibitor, p21^WAF1/Cip1 without alteration of p27^WAF1. Expression of p21^WAF1/Cip1 is considered to play a pivotal role in Hep3B cell growth arrest and induction of apoptosis. Induction of p21^WAF1/Cip1 expression was accompanied by an accumulation of acetylated histones H3 and H4 associated specifically with p21^WAF1/Cip1 gene. ChIP analysis revealed remarkable alterations in protein components bound to the promoter region of p21^WAF1/Cip1 gene in response to MS‐275 treatment. These included the degradation of HDAC1, HDAC3, and c‐Myc, and as well as increased p300 and RNA polymerase II. The selective effect of MS‐275 on the up‐regulation of the p21^WAF1/Cip1 gene whose expression was suppressed in the hepatoma cancer cell line indicated that it would be a very attractive approach in clinical liver cancer therapy. Drug Dev Res 68:61–70, 2007. © 2007 Wiley‐Liss, Inc.     

The effects of natural ligands of hormone receptors and their antagonists on telomerase activity in the androgen sensitive prostatic cancer cell line LNCaP

The effects of the 17beta-estradiol, dihydrotestosterone and hormone antagonists tamoxifen and bicalutamide on telomerase activity and expression of cell cycle related proteins in the androgen-sensitive prostatic cancer cell line LNCaP were studied. The cell line was grown in RPMI supplemented with 2.5% charcoal-stripped FBS for 72 hr. The IC(50) of tamoxifen and bicalutamide and the optimal stimulatory concentrations of 17beta-estradiol and dihydrotestosterone were determined by means of the cell-viability assay, the activity of telomerase was measured by the telomere repeat amplification protocol (TRAP) and the expression of proteins was analysed by the Western blot technique. 17beta-estradiol stimulated cell growth more effectively than dihydrotestosterone whereas hormone antagonists tamoxifen and bicalutamide caused a significant decrease in cell viability. The treatment of cells by a combination of low doses of 17 beta-estradiol and dihydrotestosterone stimulated cells stronger than treatment by a single hormone. Only 17beta-estradiol, in concentration of 10nM, increased strongly the expression of p21(Waf1/Cip1) and increased slightly telomerase activity in the LNCaP cells. 50 microM of bicalutamide down-regulated the levels of the androgen receptor, the proliferating cell nuclear antigen and telomerase activity, and up-regulated the expression of p27(Kip1). We hereby describe the first observation of the influence of bicalutamide on telomerase activity and a positive correlation between the effect of 17beta-estradiol and the induction of both the endogenous cyclin-dependent kinase inhibitor, p21(Waf1/Cip1), and telomerase activity in a prostatic cancer cell line LNCaP. These findings can shed a new light on the steroid-signaling pathway in prostate cancer cells.     

Chrysin induces G1 phase cell cycle arrest in C6 glioma cells through inducing p21Waf1/Cip1 expression: involvement of p38 mitogen-activated protein kinase

Flavonoids are a broadly distributed class of plant pigments, universally present in plants. They are strong anti-oxidants that can inhibit carcinogenesis in rodents. Chrysin (5,7-dihydroxyflavone) is a natural and biologically active compound extracted from many plants, honey, and propolis. It possesses potent anti-inflammatory, anti-oxidant properties, promotes cell death, and perturbing cell cycle progression. However, the mechanism by which chrysin inhibits cancer cell growth remains poorly understood. Therefore, we developed an interest in the relationship between MAPK signaling pathways and cell growth inhibition after chrysin treatment in rat C6 glioma cells. Cell viability assay and flow cytometric analysis suggested that chrysin exhibited a dose-dependent and time-dependent ability to block rat C6 glioma cell line cell cycle progression at the G1 phase. Western blotting analysis showed that the levels of Rb phosphorylation in C6 glioma cells exposed to 30 microM chrysin for 24h decreased significantly. We demonstrated the expression of cyclin-dependent kinase inhibitor, p21(Waf1/Cip1), to be significantly increased, but the p53 protein level did not change in chrysin-treated cells. Both cyclin-dependent kinase 2 (CDK2) and 4 (CDK4) kinase activities were reduced by chrysin in a dose-dependent manner. Furthermore, chrysin also inhibited proteasome activity. We further showed that chrysin induced p38-MAPK activation, and using a specific p38-MAPK inhibitor, SB203580, attenuated chrysin-induced p21(Waf1/Cip1) expression. These results suggest that chrysin exerts its growth-inhibitory effects either through activating p38-MAPK leading to the accumulation of p21(Waf1/Cip1) protein or mediating the inhibition of proteasome activity.