RNAi沉默Cyr61基因对喉癌细胞增殖、凋亡及侵袭能力的影响

目的：观察RNA干扰技术沉默Cyr61基因表达对人喉癌Hep-2细胞生物学行为的影响。方法：针对Cyr61mRNA的序列设计合成小于扰RNA（siRNA）的DNA模板,构建pRNAT—Cyr61重组质粒,转染人喉癌Hep-2细胞;RT—PCR和Westernblot检测其对Hep-2细胞内源性Cyr61表达的影响;四甲基偶氮唑蓝（MTr）法观察Hep-2细胞体外增殖活性变化;Transwell小室法检测Hep-2细胞体外侵袭能力的改变;流式细胞仪检测Hep-2细胞凋亡。结果：pRNAT—Cyr61重组质粒在mRNA及蛋白水平分别显著抑制Cyr61基因表达,抑制率分别最高达到74．62％和78．43％;Hep-2细胞的体外生长抑制率最高达68．22％,侵袭细胞数下降至（44．00±2．35）个;Hep-2细胞凋亡率最高达52．98％。结论：pRNAT—Cyr61可抑制Cyr61在喉癌Hep-2细胞中的表达,并抑制细胞的增殖活性和侵袭能力,促进细胞凋亡。     

喉癌Hep2细胞凋亡调控中HLA-B的作用机制

目的:探讨人类白细胞抗原B(HLA-B)在喉癌Hep2细胞凋亡调控中的作用机制。方法:免疫共沉淀结合蛋白质印迹技术鉴定HLA-B与S100结合蛋白A8(S100A8)、S100A8与S100A9及HLA-B与S100A9在体外发生相互作用的情况,免疫细胞化学对HLA-B、S100A8和S100A9在Hep2细胞中的表达进行定位,同时验证三者之间可能的关系;进一步应用RNA干涉技术,通过Real-ti mePCR及蛋白质印迹评估相互作用基因的表达情况。结果:Hep2细胞中HLA-B和S100A8蛋白在体外存在相互作用,而S100A8和S100A9并没有以异源二聚体的形式存在。免疫细胞化学结果显示,Hep2细胞中S100A8蛋白主要表达于细胞质中,HLA-B主要定位于细胞质和细胞膜上,而S100A9蛋白主要分布于细胞核中。另外,与转染PBS及无义小分子干扰(si RNA)组相比,RNA干涉HLA-B基因能明显下调S100A8 mRNA和蛋白的表达水平,F值分别为553.024、603.582,P值均为0.000;而RNA干涉S100A8基因对HLA-B mRNA和蛋白表达变化无显著影响,F值分别为1.266、1....     

Ursolic acid induces doxorubicin-resistant HepG2 cell death via the release of apoptosis-inducing factor

Ursolic acid (UA), a triterpenoid compound isolated previously from Oldenlandia diffusa, which is a Traditional Chinese Medicine used to treat cancer, was found to inhibit the proliferation of doxorubicin-resistant human hepatoma cell line (R-HepG2) through apoptosis as shown by externalization of phosphatidyl serine, morphological changes and loss of mitochondrial membrane potential. UA could activate Bak but not Bax, which implied that Bak may play an important role in UA-induced apoptosis. Furthermore, the death of R-HepG2 cells induced by UA was found to be mainly through the caspase-independent apoptosis-inducing factor (AIF) signaling pathway which was evidenced by: (a) the pan-caspase inhibitor and the specific caspase inhibitor had only modest protective effect against UA; (b) UA treatment caused the nuclear translocation of AIF, which is retained in the mitochondria in untreated R-HepG2 cells; (c) cells that had been treated with human AIF-specific siRNA could resist cell death induced by UA. In addition, a further animal study showed that UA was effective against R-HepG2 cells in vivo with negligible body weight loss and damage towards the liver, heart and spleen. Most importantly, immunohistochemical staining in animal tissues also suggested that UA also significantly inhibited the growth of R-HepG2 cells in nude mice through the AIF signaling pathway.     

中期因子诱导肝癌细胞Hep3B抵抗失巢凋亡

目的：探讨肝素结合分子中期因子（midkine,MK）对肝癌细胞Hep3B抵抗失巢凋亡的影响。方法：采用悬浮培养法建立人肝癌来源细胞系Hep3B失巢凋亡模型,以不同质量浓度（10、50、100 ng/ml）MK或PBS（对照组）处理失巢培养的肝癌细胞Hep3B,采用流式细胞术检测Hep3B细胞的凋亡,采用Western blotting检测凋亡相关蛋白Bcl-2和caspase-3的表达。结果：随着悬浮培养时间的延长,肝癌细胞Hep3B失巢凋亡率逐渐升高,培养72 h后悬浮培养的Hep3B细胞凋亡率显著高于贴壁培养的Hep3B细胞凋亡率\[（38.76±4.23）% vs （6.76±1.43）%,P<0.01\]。不同质量浓度MK处理24 h后,悬浮培养Hep3B细胞的凋亡率均明显低于对照组,且与MK的浓度呈负相关关系（r=0.951,P=0.049）;同时,MK处理后Hep3B细胞内抗凋亡蛋白Bcl-2表达明显增加,而促凋亡蛋白caspase-3则明显下降。结论：MK可能通过上调Bcl-2蛋白表达和下调caspase-3蛋白的表达来提高肝癌细胞Hep3B在失巢状态下抵抗凋亡的能力。     

Anti-proliferative effect of apigenin and its apoptotic induction in human Hep G2 cells

Apigenin, a common dietary flavonoid abundantly present in fruits and vegetables, is believed to possess preventive and therapeutic potential against cancers. In this study, the anti-hepatoma property of apigenin was evaluated on three different human hapatoma cells, namely Hep G2, Hep 3B, and PLC/PRF/5 cells. Results showed that apigenin exhibited a significant growth inhibition against the three selected hepatoma cell lines but not the normal murine liver BNL CL.2 cells. Interestingly, it was shown to possess a similar potency as a commercial anti-hepatoma agent 5-flurouracil (5-FU: positive control) against Hep G2 cells, with IC50 value of 8.02+/-1.30 microg/ml. Therefore, we conducted our study further to investigate the cellular mechanism of apigenin effect on Hep G2 cell death. Using DNA ladder and flow cytometric analysis, apigenin was found to induce apoptosis in Hep G2 cells. It also increased the accumulation of p53 and further enhanced the level of p21/WAF1. Together, it was shown that the apoptosis induced by apigenin in Hep G2 cells was possibly mediated through the p53-dependent pathway and the induction of p21 expression, which was probably associated with the cell cycle arrest in G2/M phase. The present study concludes that the anti-hepatoma activity of apigenin is as effective as 5-FU and its apoptotic mechanism might be mediated through the p53-dependent pathway and the induction of p21 expression.     

番茄红素对人肝癌HepG2细胞增殖和凋亡的影响

目的 研究番茄红素(Lycopene,LP)对人肝癌HepG2细胞生长的影响并初探其机制。方法取对数生长期HepG2细胞设空白对照组、LP(5 μg/mL)组、LP(10 μg/mL)组、LP(20 μg/mL)组和顺铂(40 μg/mL)组,每组设10个复孔;各组分别给药干预48 h后,噻唑蓝(MTT)比色法测定细胞增殖抑制率,流式细胞术(FCM)检测细胞周期和细胞凋亡状况,RT-PCR法检测Bax mRNA和Bcl-2 mRNA表达,Western blot法检测Caspase-3蛋白表达。结果 与空白对照组比较,经LP(10 μg/mL、20 μg/mL)或顺铂40 μg/mL干预48 h能够显著提高HepG2细胞增殖抑制率,延长细胞周期中G₀/G₁期而缩短G₂/M期,提高细胞凋亡率,上调促凋亡Bax mRNA表达并下调抑凋亡Bcl-2 mRNA表达,提高Bax/Bcl-2比值,上调Caspase-3蛋白表达,LP上述作用具有一定的剂量依赖性。结论 LP具有抑制人肝癌HepG2细胞增殖并促进其凋亡的作用,其机制可能与LP干预细胞周期分布和调节凋亡相关基因蛋白表达有关。     

Shikonin modulates cell proliferation by inhibiting epidermal growth factor receptor signaling in human epidermoid carcinoma cells

Shikonin isolated from the roots of the Chinese herb Lithospermum erythrorhizon has been associated with anti-inflammatory properties. We evaluated shikonin's chemotherapeutic potential and investigated its possible mechanism of action in a human cutaneous neoplasm in tissue culture. Shikonin preferentially inhibits the growth of human epidermoid carcinoma cells concentration- and time-dependently compared to SV-40 transfected keratinocytes, demonstrating its anti-proliferative effects against this cancer cell line. Additionally, shikonin decreased phosphorylated levels of EGFR, ERK1/2 and protein tyrosine kinases, while increasing phosphorylated JNK1/2 levels. Overall, shikonin treatment was associated with increased intracellular levels of phosphorylated apoptosis-related proteins, and decreased levels of proteins associated with proliferation in human epidermoid carcinoma cells.     

5-Aza-CdR对人喉鳞癌Hep2细胞凋亡及蛋白质表达的影响

目的：探讨5-Aza-CdR对人喉鳞癌Hep2细胞凋亡及蛋白质表达的影响。方法：Hep2细胞分别经10^-7mol/L 5-Aza-CdR和DMSO处理72h,应用Hoechst33258染色及流式细胞仪检测5-Aza-CdR对Hep2细胞凋亡的影响。抽提各组Hep2细胞总蛋白质,行双向电泳,采用PDQuest-7.0.1软件及MALDI-TOF质谱技术筛查5-Aza-CdR对Hep2细胞蛋白表达的影响,并通过Western blot对显著性差异蛋白质进行验证。结果：人喉鳞癌Hep2细胞在10-7mol/L 5-Aza-CdR处理72h后出现明显的细胞核致密浓染,Hep2细胞的凋亡率由对照组的（2.70±0.28）%增加到（13.96±0.41）%,具有统计学意义（P〈0.05）。双向电泳筛查了包括S100A4在内的5种表达显著差异的蛋白质,Western blot进一步验证了5-Aza-CdR能明显上调喉鳞癌Hep2细胞中S100A4的表达,进而证明了双向电泳结果的可信性。结论：5-Aza-CdR介导的Hep2细胞部分蛋白质表达改变,直接或间接地参与了5-Aza-CdR诱导的Hep2细胞凋亡的发生,为5-Aza-CdR在喉鳞癌探讨性治疗中的机制研究奠定基础。     

5-Aza-CdR对人喉鳞癌Hep2细胞凋亡及蛋白质表达的影响

目的:探讨5-Aza-CdR对人喉鳞癌Hep2细胞凋亡及蛋白质表达的影响。方法:Hep2细胞分别经10-7mol/L 5-Aza-CdR和DMSO处理72h,应用Hoechst33258染色及流式细胞仪检测5-Aza-CdR对Hep2细胞凋亡的影响。抽提各组Hep2细胞总蛋白质,行双向电泳,采用PDQuest-7.0.1软件及MALDI-TOF质谱技术筛查5-Aza-CdR对Hep2细胞蛋白表达的影响,并通过Western blot对显著性差异蛋白质进行验证。结果:人喉鳞癌Hep2细胞在10-7mol/L 5-Aza-CdR处理72h后出现明显的细胞核致密浓染,Hep2细胞的凋亡率由对照组的(2.70±0.28)%增加到(13.96±0.41)%,具有统计学意义(P<0.05)。双向电泳筛查了包括S100A4在内的5种表达显著差异的蛋白质,Western blot进一步验证了5-Aza-CdR能明显上调喉鳞癌Hep2细胞中S100A4的表达,进而证明了双向电泳结果的可信性。结论:5-Aza-CdR介导的Hep2细胞部分蛋白质表达改变,直接或间接地参与了5-Aza-CdR诱导的Hep2细胞凋亡的发生,为5-Aza-CdR在喉鳞癌探讨性治疗中的机制研究奠定基础。     

TPA诱发Hep-2和原代喉癌细胞凋亡的对比研究

目的　为初步探讨TPA用于喉癌治疗的可行性 ,对TPA分别诱发Hep 2和原代喉癌细胞的凋亡作用进行了对比观察。方法　应用琼脂糖凝胶电泳及FCM技术分别对两种细胞中的凋亡细胞进行定性、定量及细胞周期检测。结果　① 1nMTPA作用 12h ,Hep 2和原代喉癌细胞的凋亡率分别是 11.8%和 10 .14 %(P >0 .0 5 ) ;10 0nMTPA作用 2 4h ,凋亡率达峰值 ,分别为 2 7.80 %和 2 5 %(P >0 .0 5 ) ,细胞周期阻滞于G1期 ,DNA琼脂糖凝胶电泳可检出梯状带。②TPA诱发两种细胞的凋亡率具有明显的正相关 (r =0 .9674,P <0 .0 1)。结论　TPA在体外对Hep 2和原代喉癌细胞均可诱发凋亡 ,两者的凋亡率具有较好的相关性     

EGCG诱导胃癌和肝癌细胞凋亡及bcl-2表达下调的研究

目的：探讨表没食子儿茶素投食子酸酯[（－）－epigallocatechin-3-gallate,EGCG]诱导胃癌MGC－803细胞和肝癌BEL－7402细胞凋亡的作用及其调亡相关基因bcl-2产物表达的改变。方法：用MTT法、琼脂糖凝胶电泳、流式细胞术检测EGCG处理MGC-803细胞和BEL-7402细胞后,他们在形态学和生化方面的改变以及bcl－2蛋白表达水平的变化。结果：EGCG以剂量依赖的方式抑制MGC－803细胞和BEL－7402细胞的生长,其IC50值分别为188．52和264．53μg／ml。200～300μg／ml的EGCG处理MGC-803细胞和BEL-7402细胞24～36h,在琼脂糖凝胶电泳上可见凋亡细胞特征性的“梯状”带和PI染色流式细胞仪直方图上可见亚二倍体峰;流式细胞术显示EGCG以时间依赖的方式下调bcl-2蛋白的表达。结论：EGCG对胃癌MGC-803细胞和肝癌BEL-7402细胞生长具有抑制作用,其机制之一是诱导这两株肿瘤细胞的凋亡。诱导细胞凋亡的机制可能与其下调bcl-2蛋白的表达水平有关。     

miRNA-24下调S100A8蛋白表达能够抑制人喉鳞癌Hep2细胞侵袭

目的：探讨microRNA-24（miRNA-24）对喉鳞状细胞癌（laryngeal squamous carcinoma,LSCC）Hep2细胞侵袭影响的分子机制。方法：应用miRanda和RNA22靶基因预测软件预测miR-24的靶基因及其结合位点,根据预测结果通过转染miR-24前体上调其在Hep2细胞中的表达,应用荧光定量PCR和Western blot分别检测miR-24过表达对S100钙结合蛋白A8（S100 calcium binding protein A8,S100A8）mRNA和蛋白表达变化的影响。S100A8抗体阻断方法,检测转染miR-24前体后Hep2细胞侵袭能力的变化。结果：S100A83＇非翻译区（3＇-untranslation region,3＇UTR）含有一个miR-24结合位点,而且该位点与大鼠的同源性高达95%;miR-24基因转染的Hep2细胞中miR-24的表达显著升高,S100 A8蛋白的表达显著降低,（P均〈0.05）,而S100A8 mRNA表达变化未见显著性差异,（P〉0.05）。与未阻断组相比,miR-24前体转染能明显降低阻断S100A8组的Hep2细胞侵袭能力,（P〈0.05）。结论：LSCC Hep2细胞中,miR-24可结合到S100A8基因的3＇UTR,在转录后水平上负性调控S100A8基因的表达,从而抑制Hep2细胞侵袭。     

miRNA-24下调S100A8蛋白表达能够抑制人喉鳞癌Hep2细胞侵袭

目的:探讨microRNA-24(miRNA-24)对喉鳞状细胞癌(laryngeal squamous carcinoma,LSCC)Hep2细胞侵袭影响的分子机制。方法:应用miRanda和RNA22靶基因预测软件预测miR-24的靶基因及其结合位点,根据预测结果通过转染miR-24前体上调其在Hep2细胞中的表达,应用荧光定量PCR和Western blot分别检测miR-24过表达对S100钙结合蛋白A8(S100 calcium binding protein A8,S100A8)mRNA和蛋白表达变化的影响。S100A8抗体阻断方法,检测转染miR-24前体后Hep2细胞侵袭能力的变化。结果:S100A83’非翻译区(3’-untranslation region,3’UTR)含有一个miR-24结合位点,而且该位点与大鼠的同源性高达95%;miR-24基因转染的Hep2细胞中miR-24的表达显著升高,S100 A8蛋白的表达显著降低,(P均<0.05),而S100A8 mRNA表达变化未见显著性差异,(P>0.05)。与未阻断组相比,miR-24前体转染能明显降低阻断S100A8组的Hep2细胞侵袭能力,(P<0.05)。结论:LSCC Hep2细胞中,miR-24可结合到S100A8基因的3’UTR,在转录后水平上负性调控S100A8基因的表达,从而抑制Hep2细胞侵袭。     

冈田酸对喉鳞癌细胞系PP2A活性及迁移的影响

目的：探讨冈田酸（OA）对喉鳞癌细胞系（Hep-2）活性和迁移能力的影响及其可能的作用机制。方法：采用四甲基噻唑蓝（MTT）比色实验确定OA作用于Hep-2的最大浓度;酶活性实验检测不同浓度（0、50、100 nmol/L） OA对Hep-2蛋白磷酸酶2A （PP2A）活性的影响;划痕实验检测Hep-2在不同浓度（0、50、100 nmol/L） OA作用下迁移能力的变化。结果：50、100、200 nmol/L OA作用24 h后Hep-2的相对活力分别为96.7%±1.8%、82.9%±12.6%和57.2%±7.7%,与对照组（100%）比较均明显下降（P均<0.05）。50和100 nmol/L OA作用24 h后PP2A的相对活性分别为30.90%±12.01%和8.98%±4.96%,与对照组（100%）相比明显下降（P<0.05）。划痕试验中,经OA作用24及48 h后Hep-2细胞的迁移能力与对照组相比均明显减弱（P<0.05）,并且100 nmol/L OA处理组迁移能力的减弱程度较50 nmol/L OA处理组更明显（P<0.05）。结论：100 nmol/L冈田酸明显抑制Hep-2细胞PP2A活性并降低了细胞的迁移能力。     

Mechanisms of 2-methoxyestradiol-induced apoptosis and G2/M cell-cycle arrest of nasopharyngeal carcinoma cells

2-Methoxyestradiol (2ME2) is an endogenous metabolite of 17beta-estradiol (E(2)). This study aims to examine the anti-tumour activities of 2ME2 on the poorly differentiated HONE-1 NPC cell line. At the concentration of 1muM, 2ME2 was found to induce a short-term reversible G2/M cell-cycle arrest. Further 10-fold increase to 10muM, 2ME2 induced both irreversible G2/M phase cell-cycle arrest and apoptosis. Induction of apoptosis and G2/M cell-cycle arrest was due to oxidative stress as both apoptosis and the proportion of cells arresting at G2/M phase could be reduced by the superoxide dismutase (SOD) mimetic, TEMPO. Induction of apoptosis was accompanied with proteolytic cleavage of caspase-9 and -3, but not caspase-8. Kinetics studies revealed that 2ME2 induced a time-dependent inhibition of extracellular signal-regulated protein kinase (ERK) and an activation of c-jun N-terminal kinases (JNKs). The chemical inhibitor of JNKs, SP600125, was found to reduce 2ME2-induced apoptosis of the HONE-1 cells. Confocal microscopy revealed that the induction of G2/M cell-cycle arrest was associated with the presence of immunoreactivity of p-cdc2 (Tyr15) in the nucleus. The G2/M cell-cycle arrest is also correlated with an increased level of inactive p-cdc25C (Ser216) in 2ME2-treated HONE-1 cells. Results from this study indicate that production of superoxide anions might be involved in 2ME2-induced apoptosis and G2/M cell-cycle arrest of the HONE-1 cells.     

RNAi抑制NF—κB通路相关基因对喉鳞癌凋亡及转移的影响

目的：用RNA干涉方法探讨NF—κB通路参与喉癌发生、发展的可能机制。方法：RT—PCR、West—ern Blot检测喉鳞癌组织中NF—κB通路中相关基因表达，RNA干涉方法抑制p65，p50表达，流式细胞仪，TUNEL方法检测细胞凋亡，Transwell检测细胞侵袭力。结果：36例喉鳞癌组织中21例p65 mRNA表达上调（58．33％）高于癌旁组织（P=0，012），13例出现p50 mRNA表达上调（36.11％），但与癌旁组织比较无显著差异（P=0．602）。喉鳞癌组织的p65蛋白表达明显较癌旁组织增强（P=0．044），而p50蛋白表达无显著差异。特异siRNA转染Hep2细胞明显抑制p50，p65基因表达，该作用可持续10天。RNAi抑制p65基因表达使Hep2细胞凋亡率增加，在转染后第7天最高达29．89％，与对照组比较升高超过10倍（P=0．020）；同时使Hep2细胞侵袭力明显下降（P=0．003），而干涉p50基因对细胞凋亡及细胞侵袭性影响不明显。结论：RNAi抑制p65表达诱导Hep2细胞凋亡、抑制细胞侵袭力，提示抑制p65表达与常规治疗结合可能成为改善喉癌预后的选择。     

单次、分次照射与125I 粒子低剂量率照射对人喉鳞癌 Hep2细胞的抑制作用

目的：探讨125I 粒子持续低剂量率照射与分次照射、单次照射对人喉鳞癌细胞 Hep2的抑制作用及其作用机制。方法实验分为无照射对照组（Ctrl 组）、单次照射组（SDR 组）、分次照射组（FDR 组）和125I 粒子持续低剂量率照射组（125I-CLDR 组）四组。采用细胞克隆形成实验法检测 Hep2细胞在不同照射条件下细胞克隆的形成能力;用流式细胞仪检测细胞凋亡和细胞周期阻滞情况;用蛋白印迹法检测不同照射条件后 Hep2细胞总γ-H2AX、CyclinB1、Caspase3蛋白表达的变化。结果经2 Gy、4 Gy、6 Gy 的剂量照射,125I-CLDR 组 Hep2细胞克隆形成率均低于 SDR 组和 FDR 组。经4 Gy 的剂量照射后,125I-CLDR 组 Hep2细胞出现 G2/M 期阻滞,且阻滞效应较 SDR 组及 FDR 组的细胞强;125I-CLDR 组 Hep2细胞的凋亡比例明显高于 SDR 组及 FDR 组;三个照射组γ-H2AX、CyclinB1、Caspase3、NF-κB、P21和 Cdk1的表达水平上调,125I-CLDR 组 p-Cdc25c 蛋白表达水平低于 SDR 组和 FDR 组。结论在本实验条件下,125I 粒子持续低剂量率照射较单次照射、分次照射能够诱发更多 Hep2细胞出现 DNA 损伤、引起持续的 G2/M 期阻滞、诱导细胞凋亡并抑制细胞的再增殖。     

褪黑素通过促凋亡协同增强顺铂对人喉癌细胞增殖的抑制作用

目的:研究褪黑素(melatonin,MT)对人喉癌细胞增殖与凋亡的影响及MT增强人喉癌细胞对顺铂(cisplatin,DDP)治疗的敏感性.方法:采用不同质量浓度MT和DDP单独或联合处理Hep-2细胞;通过CCK-8法检测细胞增殖,流式细胞术检测细胞凋亡和细胞周期,采用两药相互作用指数(co-efficient of drug interaction,CDI)评估MT是否影响Hep-2细胞对DDP的敏感性.结果:CCK-8检测结果显示,单用MT或DDP可浓度依赖性抑制Hep-2细胞的增殖,MT可协同增强DDP对Hep-2细胞的增殖抑制作用(CDI＜1).流式细胞术检测细胞凋亡和细胞周期结果显示,MT可促进Hep-2细胞凋亡以及增加亚G1期细胞比例(P＜0.01),MT可协同DDP促进Hep-2细胞凋亡[0.5 mmol/L MT联合20μg/ml DDP组的细胞凋亡率显著高于20 μg/ml DDP组,(40.9±3.0)％vs(11.0±0.9)％,P＜0.01]以及亚G1期细胞比例[0.5 mmol/L MT联合20 μg/mlDDP组的亚G1期细胞比例显著高于20 μg/ml DDP组,(73.0±2.4)％vs(40.4±3.0)％,P＜0.01].加入Caspase抑制剂Z-VAD-fmk可逆转MT和/或DDP对Hep-2细胞的增殖抑制作用和凋亡诱导作用(均P＜0.01).结论:MT能以Caspase依赖的方式诱导人喉癌细胞Hep-2的凋亡,从而协同增强DDP对细胞的增殖抑制作用.     

Substituted titanocenes induce caspase-dependent apoptosis in human epidermoid carcinoma cells in vitro and exhibit antitumour activity in vivo

Titanocene compounds are a novel series of agents that exhibit cytotoxic effects in a variety of human cancer cells in vitro and in vivo. In this study, the antiproliferative activity of two titanocenes (Titanocenes X and Y) was evaluated in human epidermoid cancer cells in vitro. Titanocenes X and Y induce apoptotic cell death in epidermoid cancer cells, with IC50 values that are comparable to cisplatin. Characterisation of the cell death pathway induced by titanocene compounds in A431 cells revealed that apoptosis is preceded by cell cycle arrest and the inhibition of cell proliferation. The induction of apoptosis is dependent on the activation of caspase-3 and -7 but not caspase-8. Furthermore, the antitumour activity of Titanocene Y was tested in an A431 xenograft model of epidermoid cancer. Results indicate that Titanocene Y significantly reduced the growth of A431 xenografts with an antitumour effect similar to cisplatin. These results suggest that titanocenes represent a novel series of promising antitumour agents.