E1B55kDa缺陷型腺病毒对人肝癌细胞的杀伤研究

目的 探讨E1B55kDa缺陷型腺病毒dl1520对肝癌细胞的体内外杀伤作用。方法 用dl1520分别感染p53基因型不同的人肝癌细胞,感染后第4天用染色的方法检测存活细胞。用RT－PCR检测细胞内p53和p21^Waf-1基因表达的改变,通过检测腺病毒衣壳蛋白hexon基因的表达证实腺病毒的感染。在SCID裸鼠瘤体内注射dl1520,观察dl1520对肝癌细胞的体内杀伤作用。结果 p53基因缺失的肝癌细胞Hep3B对dl1520诱导的细胞毒性作用最敏感,超过60％的细菌被杀伤,而不足20％的PLC／PRF／5（p53基因突变型）和HepG2(p53基因野生型）肝癌细胞被杀伤。腺病毒感染后,HepG2细胞内p53和p21^Waf-1基因表达水平均明显升高。瘤体内注射dl1520,可显著抑制Hep3B裸鼠移植瘤的生长,而对PLC／PRF／5和HepG2的裸鼠移植瘤则无明显的生长抑制作用。结论 E1B55kDa缺失的腺病毒可以选择性地杀伤p53基因缺失的肝癌细胞,是一种潜在的肿瘤治疗手段。     

野生基因p53联合TNF-α对Hep3B凋亡作用的研究

  目的 研究补充外源性的野生型p53（wt-p53）基因联合应用小剂量TNF-α对人肝癌Hep3B细胞的凋亡作用。方法 采用lipofectAMINE 和Plus介导的脂质体转染技术将人wt-p53质粒pCEP4wtp53和空载体pCEP4导入人肝癌细胞系Hep3B内, 于转染p53 基因12 h后，在培养基中加入肿瘤坏死因子-α（20 μg／ml）。免疫荧光法检测p53蛋白定位表达。DNA片断分析法、原位末端标记（TUNEL）法观察细胞的凋亡情况。结果 TNF-α可导致细胞凋亡，与阴性对照组比较差异有统计学意义（P＜0.05）；wt-p53组及wt-p53+TNF-α组的Hep3B细胞内有p53表达，并且能促进凋亡；TNF-α与wt-p53二者联用凋亡作用更加显著。结论 wt-p53与小剂量TNF-α联用对Hep3B肿瘤细胞有协同促进凋亡的作用。     

TGF-β1对人肝癌细胞系凋亡的调控作用研究

 目的　本研究旨在明确人肝癌细胞系中TGF β1的作用及其与凋亡的关系。 方法　本研究选用了 3种含有不同 p5 3基因状态的人肝癌细胞系 ,应用TUNEL技术对TGF β1诱导的肝癌细胞的凋亡进行了定量检测。结果　TGF β1仅能诱导HepG2细胞 (野生型p5 3)凋亡 ,这提示凋亡与 p5 3基因的表达具有明确的联系。结论　HepG2细胞系比Huh 7和Hep3B系细胞更易发生TGF β1诱导的凋亡 ,TGF β1通过p5 3依赖性途径诱导肝癌细胞系发生凋亡     

TIP30基因腺病毒载体的构建及体内外抑癌作用

目的 利用缺陷型腺病毒载体表达TIP30基因,观察其体内外抑瘤作用。方法 用Ad-Easy^TM系统,在大肠杆菌同源重组,构建Ad-TIP30腺病毒载体,经在293细胞内成功包装并鉴定后,感染p53基因型不同的肝癌细胞株HepG2(p53-wt)、PLC／PRL／5(p53-mut)和骨肉瘤细胞株Saos-2(p53-null)。用台盼蓝拒染法检测存活细胞,观察TIP30的体外抑瘤作用;用RT-PCR方法检测HepG2细胞p53基因的表达水平;通过裸鼠皮下肝癌移植瘤模型观察Ad-TIP30的体内抑瘤效果。结果 Ad-TIP30对3种肿瘤细胞的增殖均有抑制作用,但对p53基因野生型的肝癌细胞株HepG2抑制作用最明显。经Ad-TIP30感染后,HepG2细胞p53基因表达水平显著升高。Ad-TIP30可显著抑制裸鼠皮下肿瘤的生长,其抑瘤率达62．8％。结论 腺病毒载体表达TIP30基因可通过p53基因依赖性或非依赖性途径抑制肿瘤细胞的增殖,是一种潜在的肿瘤生物治疗手段。     

重组人P53腺病毒增强肝癌细胞放疗的敏感性

摘 要 目的: 探讨重组人P53腺病毒(recombinant human adenovirus P53，rAdP53)对不同P53状态肝癌细胞生长的抑制和放射增敏作用。 方法: 以重组人P53腺病毒分别感染突变型P53肝癌细胞PLC/PRF/5和野生型P53肝癌细胞SMMC7721， Western blotting检测肝癌细胞P53蛋白表达，MTT法检测细胞存活率，台酚蓝染色绘制细胞生长曲线。肝癌细胞感染rAdP53 48 h后照射不同剂量的X射线，克隆形成法检测放射增敏比，TUNEL法检测细胞凋亡。 结果: 50 MOI rAd-P53转染PLC/PRF/5和SMMC7721细胞后转染效率分别为89.37%和87.53%，转染48 h可见P53蛋白高表达，MTT法显示细胞存活率分别为341%和35.44%，细胞生长曲线显示感染后第5天两种细胞生长抑制率分别为41.91%和17.03% (P<0.01)，PLC/PRF/5细胞的凋亡率\[(8.8±1.4)%\]显著高于SMMC7721 [(4.1±1.1)%] (P<0.01)。应用20 MOI的rAd-P53转染细胞48 h后加X射线(4 Gy)照射，PLC/PRF/5细胞的凋亡率为(26.9±5.6)%，显著高于SMMC7721细胞凋亡率(16.4±29)% (P<0.01)；20 MOI的rAdP53转染后加照射PLC/PRF/5和SMMC7721，细胞的放射增敏比SER(Dq)值分别为1.30和1.16；SER(D0)值分别为1.57和1.25。 结论: rAdP53能显著抑制人肝癌细胞生长、诱导细胞凋亡并提高细胞的放射敏感性，其对PLC/PRF/5细胞作用显著强于SMMC7721细胞；表明不同内源性P53状态的肝癌细胞对rAdP53治疗及其协同的放疗敏感性可能不同。     

TGF-β1对人肝癌细胞系凋亡的调控作用研究

目的肝细胞对TGF-β1敏感性的丧失据认为是肝癌重要的致病因素之一。本研究旨在明确人肝肿瘤细胞系中TGF-β1的作用及其与凋亡的关系。方法选用三种含不同p53基因状态的人肝肿瘤细胞系,应用脱氧核糖核苷酸末瑞转移酶介导的dUTP缺口末端标记技术(TUNEL)对TGF-β1诱导的肝肿瘤细胞的凋亡进行定量检测。结果在应用TUNEL检测三个细胞系中,TGF-β1仅能诱导Hep3B细胞(缺失p53)则凋亡较少。这提示凋亡p53基因的表达具有明确的联系。结论HepG2细胞系比Huh-7和Hep3B系细胞更易发生TGF-β1诱导的凋亡,TGF-β1通过p53依赖性途径诱导肝癌细胞系发生凋亡。     

RNAi载体构建及其对PLC/PRF/5细胞突变p53基因抑制作用的实验研究

目的利用RNA干扰(RNA interference，RNAi)技术，以突变p53基因为靶基因，构建干扰载体，并观察载体对肿瘤细胞生长周期的影响，为下一步探索肿瘤基因治疗的新途径奠定基础。方法设计具有小发夹结构的两条DNA序列，经退火成为互补双链，再克隆至干扰载体中，转化TOP10菌株，提取质粒行酶切鉴定，稳定转染PLC／PRF／5细胞，Western blot检测p53蛋白，MTT法观察细胞生长曲线，流式细胞仪分析细胞周期变化。结果成功构建针对突变p53的特异性RNA干扰载体，此干扰载体转染PL／PRF／5细胞后，p53蛋白表达水平降低，肿瘤细胞生长速度减慢，G1期细胞分布明显增多。结论成功构建针对突变p53的RNA干扰载体，此干扰载体可以有效降低p53蛋白表达水平，导致突变p53基因沉默，进而延缓PLC／PRF／5细胞生长速度，阻滞肿瘤细胞停滞于G1期。     

重组人IL-24蛋白诱导肝癌细胞生长抑制和凋亡

目的研究重组人IL-24蛋白（rhIL-24）选择性诱导肝癌细胞生长抑制和凋亡的作用。方法重组由Igk前导肽、IL-24cDNA（不含自身信号肽）和myc—tag组成的融合基因（Igk7m），构建表达载体pcDNA3．1-Igk7m，稳定转染293细胞，表达并粗提分泌性rhIL-24蛋白。以人肝癌细胞株PLC／PRF／5（p53突变型）、SMMC-7721（p53野生型）和正常人肝细胞株WRL-68为靶细胞，用活细胞计数法和TUNEL法分析rhIL-24处理对培养的靶细胞生长和凋亡的影响。结果经测序鉴定，融合基因各片段的核苷酸序列和总阅读框架完全正确。应用Westernblot在筛选的转基因293细胞克隆和其培养上清中均检测到rhIL-24蛋白，分子量分别约为25kDa和35kDa。与WRL-68对照组相比，分泌性rhIL-24蛋白粗提液处理可显著抑制PLC／PRF／5和SMMC-7721肝癌细胞的生长增殖（P〈0．01）。rhIL-24蛋白处理还可显著增加PLC／PRF／5和SMMC-7721的凋亡细胞百分率（P〈0．01），而对正常肝细胞WRL-68无明显影响（P〉0．05）。结论rhIL-24蛋白能选择性诱导培养的肝癌细胞株PLC／PRF／5和SMMC-7721生长抑制和凋亡。     

p53基因对胶质瘤细胞系U251生长抑制作用的研究

背景与目的：肿瘤抑制基因p53是调节多种与细胞周期、凋亡、DNA修复等有关基因表达的转录因子。p53基因在大约30％的胶质瘤中发生突变，在胶质瘤的发生和发展中起重要作用。本文主要探讨野生型p53基因过表达对脑胶质瘤细胞系U251细胞生长抑制的机制。方法：通过p53腺病毒表达载体pAdCMV-p53及空载体pAdCMV-lacZ分别感染U251细胞系，RT-PCR及Westem blot方法检测转染效率；并通过MTT检测生长抑制率、流式细胞仪检测细胞周期及TUNEL检测分析细胞凋亡等指标观察p53基因对U251细胞生长的影响。结果：MOI为100时，野生型p53基因的过表达可引起U251细胞G0、G1期阻滞、诱导U251细胞凋亡以及引起U251细胞生长抑制。结论：p53基因可以通过细胞周期G0、G1期阻滞及诱导细胞凋亡抑制胶质瘤细胞系U251的生长。     

DNA甲基化导致肝细胞癌SYK基因失表达

目的：探讨SYK（Spleen tyrosine kinase，脾酪氨酸激酶）在肝细胞癌中的表达和不表达的机制。方法：分别用逆转录-聚合酶链反应（RT—PCR）方法和甲基化特异性聚合酶链反应（Methylation—specific PCR，MSP）检测SYK基因在肝癌细胞系（HepG2和Hep3B）和34例肝细胞癌组织、癌旁非瘤组织中的表达和甲基化情况。结果：肝癌细胞系Hep3B表达SYKmRNA，而HepG2不表达SYK mRNA、DNA甲基化转移酶抑制剂5-aza-2’-deoxyeytidine处理HepG2后，SYK重新表达．Hep3B细胞SYK甲基化阴性，HepG2细胞SYK甲基化阳性；34例肝细胞癌组织标本中，5例SYKmRNA表达阴性，SYK基因甲基化均阳性；29例SYK mRNA表达阳性，其中3例SYK甲基化阳性．其余26例SYK甲基化阴性。肿瘤组织SYK基因的甲基化率为23．5％（8／34），而瘤旁肝组织中为8．8％（3／34）。结论：SYK基因启动子甲基化导致肝细胞癌SYK mRNA失表达、可能是肝癌发病的机制之一。     

Radiation-induced intercellular signaling mediated by cytochrome-c via a p53-dependent pathway in hepatoma cells

The tumor suppressor p53 has a crucial role in cellular response to DNA damage caused by ionizing radiation, but it is still unclear whether p53 can modulate radiation-induced bystander effects (RIBE). In the present work, three different hepatoma cell lines, namely HepG2 (wild p53), PLC/PRF/5 (mutation p53) and Hep3B (p53 null), were irradiated with γ-rays and then co-cultured with normal Chang liver cell (wild p53) in order to elucidate the mechanisms of RIBE. Results showed that the radiosensitivity of HepG2 cells was higher than that of PLC/PRF/5 and Hep3B cells. Only irradiated HepG2 cells, rather than irradiated PLC/PRF/5 or Hep3B cells, could induce bystander effect of micronuclei (MN) formation in the neighboring Chang liver cells. When HepG2 cells were treated with 20?μM pifithrin-α, an inhibitor of p53 function, or 5?μM cyclosporin A (CsA), an inhibitor of cytochrome-c release from mitochondria, the MN induction in bystander Chang liver cells was diminished. In fact, it was found that after irradiation, cytochrome-c was released from mitochondria into the cytoplasm only in HepG2 cells in a p53-dependent manner, but not in PLC/PRF/5 and Hep3B cells. Interestingly, when 50?μg/ml exogenous cytochrome-c was added into cell co-culture medium, RIBE was significantly triggered by irradiated PLC/PRF/5 and Hep3B cells, which previously failed to provoke a bystander effect. In addition, this exogenous cytochrome-c also partly recovered the RIBE induced by irradiated HepG2 cells even with CsA treatment. Our results provide new evidence that the RIBE can be modulated by the p53 status of irradiated hepatoma cells and that a p53-dependent release of cytochrome-c may be involved in the RIBE.     

Differential regulation of EGF production, EGF receptor-binding, and cellular growth by sodium-butyrate in hep3b and plc/prf/5 human hepatoma-cells

Hep3B and PLC/PRF/5 human hepatoma cells express epidermal growth factor (ECF) mRNA and secret this polypeptide growth factor into the culture medium. The production of EGF was inhibited by sodium butyrate in a dose-dependent manner. EGF receptor numbers in both cell lines were increased after treatment with butyrate for 2 days, In addition, the binding affinity of EGF to its receptor was decreased in butyrate-treated PLC/PRF/5 cells while it did not change in Hep3B cells. EGF-stimulated cell growth in PLC/PRF/5 cells was attenuated by sodium butyrate whereas no significant inhibition df cell growth of Hep3B cells was found in the same condition. Our results suggest that EGF acts as an autocrine growth stimulator in human hepatoma cells and sodium butyrate can differentially regulate the responses of hepatoma cells to EGF by modulating the differentiation states of these cells.     

Induction of apoptosis by cisplatin and its effect on cell cycle-related proteins and cell cycle changes in hepatoma cells.

We investigated cisplatin-induced apoptosis and the effects on cell cycle-related proteins and cell cycle changes. Two human hepatoma cell lines, HepG2 (with wild-type p53) and Hep3B (with deleted p53), were treated with different concentrations of cisplatin. Cisplatin induced apoptosis in both cell lines as assessed by cell morphology, DNA fragmentation analysis,TdT-mediated dUTP nick end labeling assay and flow cytometry. HepG2 cells were more sensitive to cisplatin than Hep3B. Low-dose cisplatin induced a transient G(1) arrest, S phase block and upregulation of p53 and p21(WAF1/CIP1) expression in HepG2, but not in Hep3B cells. With cisplatin at a high dose, both cell lines underwent apoptosis that was accompanied by downregulation of p27(KIP1) and Bcl-x(L). In HepG2, upregulation of p53 and p21(WAF1/CIP1) was observed before apoptosis occurred, suggesting that cisplatin-induced apoptosis in HepG2 might be p53-dependent. Expression of Fas was also increased following cisplatin treatment in HepG2. However, there was no induction of p53, p21(WAF1/CIP1) and Fas observed in Hep3B cells. In conclusion, cisplatin induced apoptosis in hepatoma cells via both p53-dependent and -independent pathways.     

Doxorubicin-induced apoptosis and chemosensitivity in hepatoma cell lines

PURPOSE: Doxorubicin (DOX) is a commonly used anticancer drug which causes DNA damage and kills cancer cells mainly by apoptosis. However, the process leading to killing of cancer cells and the molecular basis of resistance to DOX are not well understood. To evaluate the role of p53 and the cellular effects of DOX on hepatoma cell lines, we examined three hepatoma cell lines with different p53 status--Huh-7 (mutated p53), HepG2 (wild-type p53) and Hep3B (deleted p53). METHODS: The chemosensitivity of the three hepatoma cell lines was assessed using the MTT assay, and cell cycle distribution was evaluated by flow cytometry. Western blotting and immunostaining were employed to examine the protein alterations in response to DOX treatment, and a DNA fragmentation assay was performed to detect apoptosis. RESULTS: Of the three cell lines, HepG2 was found to be most resistant to DOX, followed by Hep3B, and Huh-7 was most sensitive to DOX treatment. HepG2 showed G1 arrest 24 h after drug administration and upregulation of p53 protein level in a time-dependent manner. In Hep3B cells (deleted p53), G2/M phase arrest was observed soon after drug administration, accompanied by induced apoptosis that was p53-independent. In Huh-7 cells (mutated p53), which were most sensitive to DOX, there was neither G1 nor G2 arrest, and the level of p53 mutated protein was downregulated after DOX treatment. MDM2 and p27 proteins were downregulated in all cell lines independently of p53 status. p21 was upregulated following p53 activation at low doses of DOX in HepG2 cells, but at higher doses, p21 was downregulated in Huh-7 and HepG2 cells. CONCLUSION: DOX confers different chemosensitivity on different hepatoma cell lines with different p53 status. The contrasting relationships between chemosensitivity and p53 status and expression suggest that DOX-induced apoptosis and cell death involve pathways that are independent of p53.     

Eicosapentaenoic acid induces Fas-mediated apoptosis through a p53-dependent pathway in hepatoma cells

Eicosapentaenoic acid (EPA) has been demonstrated to induce apoptosis and cell cycle arrest in various cancer cell lines in vitro. In this study, we investigated the anti-tumor effects of EPA on hepatoma cell lines and the mechanisms responsible for induced cell death. Three hepatoma cell lines tested had different p53 status: HepG2 with a wild-type p53; Hep3B, of which the endogenous p53 was deleted; and Huh7 with its p53 mutated. MTT assay showed reduced viability of HepG2 cells after exposure to EPA, and the cytotoxicity of EPA was time and dose dependent. However, EPA had no effect on the viability and cell death in the two other hepatoma cell lines containing dysfunctional p53. DNA fragmentation analysis and TUNEL (terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridine diphosphate [dUTP] nick end labeling) staining showed a typical pattern of DNA laddering and DNA breaks staining, respectively, in wild-type p53-containing HepG2 cells after EPA treatment. We also observed that EPA induced transient nuclear accumulation of P53 protein that subsequently up-regulated the expression of Fas messenger RNA and protein in HepG2 cells. In contrast, these findings were not observed in Hep3B and Huh7 cells exposed to EPA. Most notably, EPA-induced apoptosis in HepG2 cells could be reduced almost completely by treatment with FasL antisense oligonucleotides. We conclude that EPA inhibits the growth of HepG2 cells and mediates its effect, at least in part, via the Fas-mediated apoptosis. It appears that the effects of EPA on hepatoma cells are determined by the status of p53 and that wild-type p53 is a prerequisite for the anticancer effect of EPA.     

Chromosomes of human hepatoma cell lines

The karyotypes of three human hepatoma cell lines Hep G2, Hep 3B and PLC/PRF/5 were investigated by G- and C-banding techniques. In addition to ploidy changes, typical for most carcinoma cell lines, certain markers were found that remained stable throughout passage of these cultures. Chromosome I is involved in multiple translocations, resulting in at least three copies of the chromosome I heterochromatin region in each cell line. Inversion in the 9qh region is also seen. In addition, each of the cell lines consistently contains trisomy of 17q. The rearrangements of chromosome I are most striking in the Hep 3B and PLC/PRF/5 cell lines, which are derived from human hepatocellular carcinomas and contain integrated copies of the hepatitis B viral genome. These two cell lines are characterized by the presence of at least five copies of the I (p13←q21) region that result from multiple deletions and/or translocations; by consistent trisomy and polymorphism of the 9qh region; and by trisomy of chromosome 10 (also involved in rearrangements). The Hep G2 and Hep 38 cell lines behave functionally as highly differentiated liver parenchymal cells and are karyologically distinguishable from PLC/PRF/5 both by the presence of trisomy of 6 (pter←q14) and by the finding that one of the homologues of chromosome 15 is 15q+.     

Inhibition of cell growth and induction of G1-phase cell cycle arrest in hepatoma cells by steroid extract from Meretrix meretrix

In this study, we report that the steroid extract 5alpha, 8alpha-epidioxycholest-6-ene-3beta-ol (MME) from Meretrix meretrix has the ability to inhibit growth of hepatoma cells and to induce G1-phase cell cycle arrest in two human hepatoma cell lines, HepG2 and Hep3B. HepG2 cells were more sensitive than Hep3B to MME. The extract markedly up-regulated the expression of p53 and p21WAF1/CIP1 in HepG2, suggesting that MME-induced G1 phase cell cycle arrest in HepG2 might be p53-dependent. Therefore, the up-regulation of p27KIP1and p16INK4A in both cell lines indicates that a p53-independent pathway might be involved in the mechanism of MME inducing cell cycle arrest. In conclusion, MME induces G1 phase cell cycle arrest via both p53-dependent and p53-independent pathways.     

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.