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.     

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.     

Growth arrest induced by C75, A fatty acid synthase inhibitor, was partially modulated by p38 MAPK but not by p53 in human hepatocellular carcinoma

C75, a well-known fatty acid synthase (FAS) inhibitor, has been shown to possess potent anti-cancer activity in vitro and in vivo. In this study, we reveal that C75 is a cell cycle arrest inducer and explore the potential mechanisms for this effect in hepatocellular carcinoma (HCC) cell lines with abundant FAS expression: HepG2 and SMMC7721 cells with wt-p53, and Hep3B cells with null p53. The results showed FAS protein expression and basal activity levels were higher in HepG2 cells than in the other two HCC cell lines. Treatment with C75 inhibited FAS activity within 30 min of administration and induced G(2) phase arrest accompanied by p53 overexpression in HepG2 and SMMC7721 cells. By contrast, C75 triggered G(1) phase arrest in Hep3B cells, and RNA interference targeting p53 did not attenuate C75-induced G(2) arrest in HepG2 cells. Similarly, p53 overexpression via p53 plasmid transfection did not affect C75-induced G(1) phase arrest in Hep3B cells. However, we observed a clear correlation between p38 MAPK activation triggered by C75 and the induction of cell cycle arrest in all three HCC cells. Furthermore, treatment with the p38 MAPK inhibitor SB203580 reduced p38 MAPK activity and cell cycle arrest, and also partially restored cyclin A, cyclin B1, cyclin D1 and p21 protein levels. Collectively, it was p38 MAPK but not p53 involved in C75-mediated tumor cell growth arrest in HCC cells.     

乙型肝炎病毒X基因经p53依赖性与非依赖性途径对p21WAF1表达的影响

背景与目的:研究表明,在不同情况下乙型肝炎病毒 X基因(HBx)对 p21WAF1的表达具有不同的影响,但作用机制仍不清楚.本研究的目的是探讨 HBx对 p53下游基因 p21WAF1的影响.方法:通过正、反义野生型 p53(wtp53)与 HBx单转染及共转染人肝癌细胞株 SMMC-7721细胞,以及 HBx转染不同内源性 p53状态的肝癌细胞株,检测 p21WAF1启动子荧光素酶基因表达,并用流式细胞仪观察细胞周期的变化 ,Western blot法比较 p53、p21WAF1表达水平的变化.结果:正、反义 wtp53与 HBx 单转染及共转染 SMMC-7721细胞 ,HBx与正义 wtp53共转染组(1.007± 0.098)与单转染正义 wtp53(0.490± 0.012)相比,p21WAF1启动子荧光素酶基因表达明显升高(P< 0.05),其余各组 HBx均可导致 p21WAF1启动子荧光素酶基因表达明显减少(P< 0.05).Western blot法表明 HBx可导致 p53的表达增加,但 p53表达较低的 SMMC-7721细胞转染 HBx后 p21WAF1蛋白的表达减弱 ,p21WAF1启动子荧光素酶基因表达(0.053± 0.010)也较对照组(0.094± 0.013)明显减少(P< 0.05),而 p53表达较强的 HepG2细胞转染 HBx后 p21WAF1蛋白的表达增强、p21WAF1启动子荧光素酶基因的表达(1.252± 0.052)较对照组明显升高(0.767± 0.031)(P< 0.05).细胞周期结果表明瞬时转染 HBx的 SMMC-7721和 Hep3B细胞停滞在 G0-G1期细胞数(42.31%、36.96%)较对照组(47.10%、42.90%)减少,而瞬时转染 HBx的 HepG2细胞(63.62%)停滞在 G0-G1期的细胞数较对照组(57.42%)增加,但稳定筛选后 ,pcDNA3HBxHepG2细胞(57.31%)停滞在 G0-G1期细胞数较对照组(61.49%)减少.结论:HBx一方面可能引起 p53蛋白在细胞内积聚导致 p21WAF1表达升高,另一方面可直接抑制 p21WAF1启动子的转录活性.     

Tumor infiltrating macrophages reduce development of peritoneal colorectal carcinoma metastases

We previously reported that HS-1200, a synthetic chenodeoxycholic acid derivative, has apoptosis-inducing activity in various human cancer cells. The present study was undertaken to examine whether HS-1200 had an anticancer effect on HepG2 (wild-type p53) and Hep3B (p53 deleted) human hepatoma cells. Treatment of both cells with HS-1200 resulted in growth inhibition and induction of apoptosis as measured by MTT assay, nuclear staining, DNA fragmentation and flow cytometry analysis. The increase in apoptosis was associated with the alteration in the ratio of Bcl-2/Bax protein expression. In addition, flow cytometry analysis indicated that HS-1200 induced G1 phase arrest in both cells. When analyzing the expression of cell cycle-related proteins, we found that HS-1200 reduced the expression levels of cyclin D1, cyclin A, and Cdk2. HS-1200 treatment also caused an increase in the expression levels of p21(WAF1/CIP1) in HepG2 cells in a p53-dependent manner and in Hep3B cells in a p53-independent manner. Moreover, the expression level of p27(KIP1) was increased in both cell lines. We also observed that HS-1200 decreased the levels of cyclooxygenase (COX)-2 mRNA and protein expression. Furthermore, HS-1200 treatment markedly induced the Egr-1 expression at an early time point, and the increased expression levels of p53, p21(WAF1/CIP1), p27(KIP1), and COX-2 after treatment with HS-1200 were completely inhibited in HepG2 cells and partially inhibited in Hep3B cells by silencing of Egr-1, respectively. Taken together, these findings provide important new insights into the possible molecular mechanisms of the anticancer activity of the synthetic bile acid derivative, HS-1200, through Egr-1 regulation.     

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。     

不同p53状态的肝癌细胞系DNA损伤修复能力的比较

目的 观察不同p53状态的肝癌细胞在DNA损伤因素存在下，探讨p53在肝细胞癌发生过程中的作用。方法 选用内源性表达野生型p53、突变型p53、p53全基因缺失的HepG2、PLC／PRF／5、Hep3B肝癌细胞系，将含有p53结合序列的CAT报告基因质粒分别转染各细胞，通过ELISA方法检测报告基因CAT活化情况，观察p53功能状态；用细胞生长曲线比较不同p53状态的细胞生长速度的差异；给予一定剂量的紫外线照射，检测各细胞程序外DNA损伤修复(UDS)能力；观察紫外线照射后细胞克隆形成情况，反映不同细胞系在紫外线照射后细胞存活率的不同。结果 报告基因CAT在HepG2细胞表达最强，而在PLC／PRF／5、Hep3B肝癌细胞均处于较低水平，说明HepG2细胞具有功能性的p53表达；HepG2细胞生长速度明显慢于其他两种细胞；紫外线照射后，HepG2具有较好的DNA损伤修复能力以及较高的细胞生存率。结论 野生型p53具有抑制肝癌细胞生长、保持细胞良好的DNA损伤修复的功能。     

Inhibition of proteasome-dependent degradation of Wee1 in G2-arrested Hep3B cells by TGF beta 1

Transforming growth factor beta1 (TGF beta 1)-induced G2 arrest was observed when a proliferation inhibitory function of the retinoblastoma protein (Rb) was compromised, but the mechanism underlying the G2 arrest was poorly characterized compared with that of G1 arrest. In the present study, we characterized G2 arrest induced by TGF beta1 (1 ng/mL) in the Rb-negative hepatoma cell line (Hep3B) and compared with G1 arrest in the Rb-positive hepatoma cell line (Huh7). Activities of cyclin-dependent kinases (CDK) 2 and cell division cycle (CDC) 2 were markedly decreased at 24 h, the time when cell-cycle arrest became apparent in both cell lines. However, considerable amounts of inactive CDC2-cyclinB1 complexes were present in the nucleus of G2-arrested Hep3B but were not present in G1-arrested Huh7. The inhibitory phosphorylation of CDC2 on Tyr-15 was significantly elevated at 12-24 h, and its levels gradually declined during G2 arrest in Hep3B. In particular, augmentation of CDK inhibitors p21cip1 and p27kip1 and Wee1 kinase and diminution of CDC25C phosphatase coincided with induced Tyr-15 phosphorylation and inhibition of CDC2. Wee1 in Hep3B was unstable and was degraded in a proteasome-dependent manner, but it became substantially stabilized within 6 h of TGF beta 1 treatment. Moreover, a Wee1 inhibitor, PD0166285, abrogated the TGF beta 1-induced G2 arrest in Hep3B. These findings suggest that TGF beta 1 induced G2 arrest in Hep3B at least in part through stabilization of Wee1 and subsequent increase in Tyr-15 phosphorylation and inhibition of CDC2.     

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.     

Effects of the protein kinase inhibitors wortmannin and KN62 on cellular radiosensitivity and radiation-activated S phase and G1/S checkpoints in normal human fibroblasts

Wortmannin is a potent inhibitor of phosphatidylinositol (PI) 3-kinase and PI 3-kinase-related proteins (e.g. ATM), but it does not inhibit the activity of purified calmodulin-dependent protein kinase II (CaMKII). In the present study, we compared the effects of wortmannin and the CaMKII inhibitor KN62 on the response of normal human dermal fibroblast cultures to gamma radiation. We demonstrate that wortmannin confers a phenotype on normal fibroblasts remarkably similar to that characteristic of cells homozygous for the ATM mutation. Thus wortmannin-treated normal fibroblasts exhibit increased sensitivity to radiation-induced cell killing, lack of temporary block in transition from G1 to S phase following irradiation (i.e. impaired G1/S checkpoint), and radioresistant DNA synthesis (i.e. impaired S phase checkpoint). Wortmannin-treated cultures display a diminished capacity for radiation-induced up-regulation of p53 protein and expression of p21WAF1, a p53-regulated gene involved in cell cycle arrest at the G1/S border; the treated cultures also exhibit decreased capacity for enhancement of CaMKII activity post-irradiation, known to be necessary for triggering the S phase checkpoint. We further demonstrate that KN62 confers a radioresistant DNA synthesis phenotype on normal fibroblasts and moderately potentiates their sensitivity to killing by gamma rays, without modulating G1/S checkpoint, p53 up-regulation and p21WAF1 expression following radiation exposure. We conclude that CaMKII is involved in the radiation responsive signalling pathway mediating S phase checkpoint but not in the p53-dependent pathway controlling G1/S checkpoint, and that a wortmannin-sensitive kinase functions upstream in both pathways.     

Silibinin efficacy against human hepatocellular carcinoma.

PURPOSE: Hepatocellular carcinoma (HCC) is one of the most common recurrent malignancies, for which, currently, there is no effective therapy. Considering the antihepatotoxic activity of silibinin, a widely used drug and supplement for various liver disorders, together with its strong preventive and anticancer efficacy against various epithelial cancers, we investigated the efficacy of silibin against human HCC cells. EXPERIMENTAL DESIGN: Silibinin effects were examined on growth, cytotoxicity, apoptosis, and cell cycle progression in two different HCC cell lines, HepG2 (hepatitis B virus negative; p53 intact) and Hep3B (hepatitis B virus positive; p53 mutated). At molecular level, cell cycle effects of silibinin were assessed by immunoblotting and in-bead kinase assays. RESULTS: Silibinin strongly inhibited growth of both HepG2 and Hep3B cells with a relatively stronger cytotoxicity in Hep3B cells, which was associated with apoptosis induction. Silibinin also caused G1 arrest in HepG2 and both G1 and G2-M arrests in Hep3B cells. Mechanistic studies revealed that silibinin induces Kip1/p27 but decreases cyclin D1, cyclin D3, cyclin E, cyclin-dependent kinase (CDK)-2, and CDK4 levels in both cell lines. In Hep3B cells, silibinin also reduced the protein levels of G2-M regulators. Furthermore, silibinin strongly inhibited CDK2, CDK4, and CDC2 kinase activity in these HCC cells. CONCLUSION: Together, these results for the first time identify the biological efficacy of silibinin against HCC cells, suggesting the importance of conducting further investigations in preclinical HCC models, especially on in vivo efficacy, to support the clinical usefulness of silibinin against hepatocellular carcinoma in addition to its known clinical efficacy as an antihepatotoxic agent.     

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.     

Involvement of p53, nuclear factor kappaB and Fas/Fas ligand in induction of apoptosis and cell cycle arrest by saikosaponin d in human hepatoma cell lines

In this study, we report the proapoptotic effect of saikosaponin d in two liver cancer cell lines, Hep G2 and Hep 3B cells. Treatment with saikosaponin d decreased the cell proliferation of Hep G2 and Hep 3B cells in a dose dependent manner. In Hep G2, saikosaponin d blocked the progression of cell cycle at G1 phase by inducing p53 expression and further up-regulating p21/WAF1 expression. In addition, an enhancement in Fas/APO-1 and its two form ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as Bax protein, was responsible for the apoptotic effect induced by saikosaponin d. Furthermore, saikosaponin d also inhibited the cell survival signaling by enhancing the amount of IkappaBalpha in cytoplasm and reducing the level and activity of NF-kappaB in the nucleus, and subsequently attenuated the expression of Bcl-XL in Hep G2 and Hep 3B cells. Saikosaponin d therefore decreased the cell proliferation and inducted apoptosis both in p53-positive Hep G2 and p53-negative Hep 3B cells.     

Notch1基因转染对人肝癌细胞Hep3B生长的影响及作用机制的研究

目的：研究逆转录病毒介导的Notch1（ICN）基因转染对人肝癌细胞生长的影响，并对其作用机制进行了探讨。方法： 采用磷酸钙沉淀法质粒共转染293T细胞，制备出表达组成性活化形式的Notch1（ICN）和/或绿色荧光蛋白（GFP）的逆转录病毒载体MSCVICN/GFP及对照逆转录病毒载体MSCVGFP，并检测病毒滴度。用逆转录病毒感染人肝癌细胞Hep3B，观察病毒的感染效率，MTT比色法测定瞬时表达Notch1（ICN）对Hep3B人肝癌细胞生长的影响，利用流式细胞仪分析细胞周期分布的变化，Western blot方法检测细胞周期调控蛋白的变化。结果：通过质粒共转染可获得具有较高滴度的重组逆转录病毒。MTT比色法显示瞬时表达Notch1（ICN）基因可以抑制人肝癌细胞Hep3B的生长，瞬时表达Notch1（ICN）基因可使Hep3B细胞周期停滞在G0/G1期并上调细胞周期调控蛋白P53的表达水平。结论：Notch1基因可通过影响细胞周期分布和P53蛋白的表达水平而抑制人肝癌细胞生长。     

DNA damage-induced cell cycle checkpoints involve both p53-dependent and -independent pathways: role of telomere repeat binding factor 2

Treatment of colon cancer cells with MNNG causes DNA damage with reduced telomeric signals in a p53-dependent manner, but increased cell cycle arrest in S-G(2)/M by both p53-dependent and independent mechanisms. Results also indicate that cellular levels of TRF2 may play a critical role in MNNG-induced cell cycle arrest and apoptosis of colon cancer cells.