Emodin-induced apoptosis through p53-dependent pathway in human hepatoma cells

Most of the commonly used cytotoxic anticancer drugs have been shown to induce apoptosis in susceptible cells. However, the signaling pathway of their apoptotic effects remains undefined. In this study, the cytotoxic effect of emodin on various human hepatoma cell lines was investigated. Results demonstrated that emodin exhibited strongly suppressing effect on HepG2/C3A, PLC/PRF/5, and SK-HEP-1 cells, with the IC(50) value of 42.5, 46.6, and 53.1 microM, respectively. Furthermore, emodin induced apoptosis in HepG2/C3A cells was clearly verified by the appearance of DNA fragmentation and sub-G(1) accumulation. Besides, HepG2/C3A cells were found to be arrested in G(2)/M phase after the cells were treated with 60 microM emodin for 48 h. Moreover, significant increase in the levels of apoptosis-related signals such as p53 (419.3 pg/ml), p21 (437.4 units/ml), Fas (6.6 units/ml), and caspase-3 (35.4 pmol/min) were observed in emodin treated HepG2/C3A cells. Taken together, emodin displays effective inhibitory effects on the growth of various human hepatoma cell lines and stimulates the expression of p53 and p21 that resulted in the cell cycle arrest of HepG2/C3A cells at G(2)/M phase. Results also suggest that emodin-induced apoptosis in HepG2/C3A cells were mediated through the activation of p53, p21, Fas/APO-1, and caspase-3. It implies that emodin could be a useful chemotherapeutical agent for treatment of hepatocellular carcinoma (HCC).     

Ellipticine induces apoptosis through p53-dependent pathway in human hepatocellular carcinoma HepG2 cells

Ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole), one of the simplest naturally occurring alkaloids, was isolated from the leaves of the evergreen tree Ochrosia elliptica Labill (Apocynaceae). Here, we reported that ellipticine inhibited the cell growth of human hepatocellular carcinoma cell line HepG2 and provided molecular understanding of this effect. The XTT assay results showed that ellipticine decreased the cell viability of HepG2 cells in a dose- and time-dependent manner, and the IC50 value was 4.1 microM. Furthermore, apoptosis induction by ellipticine in HepG2 cells was verified by the appearance of DNA fragmentation and annexin V-FITC/propidium iodide (PI) staining assay. Ellipticine treatment was found to result in the upregulation of p53, Fas/APO-1 receptor and Fas ligand. Besides, ellipticine also initiated mitochondrial apoptotic pathway through regulation of Bcl-2 family proteins expression, alteration of mitochondrial membrane potential (DeltaPsim), and activation of caspase-9 and caspase-3. Taken together, ellipticine decreased the cell growth and induced apoptosis in HepG2 cell.     

CREB represses p53-dependent transactivation of MDM2 through the complex formation with p53 and contributes to p53-mediated apoptosis in response to glucose deprivation

Recently, we have described that CREB (cAMP-responsive element-binding protein) has the ability to transactivate tumor suppressor p53 gene in response to glucose deprivation. In this study, we have found that CREB forms a complex with p53 and represses p53-mediated transactivation of MDM2 but not of p21^WAF1. Immunoprecipitation analysis revealed that CREB interacts with p53 in response to glucose deprivation. Forced expression of CREB significantly attenuated the up-regulation of the endogenous MDM2 in response to p53. By contrast, the mutant form of CREB lacking DNA-binding domain (CREBΔ) had an undetectable effect on the expression level of the endogenous MDM2. During the glucose deprivation-mediated apoptosis, there existed an inverse relationship between the expression levels of MDM2 and p53/CREB. Additionally, p53/CREB complex was dissociated from MDM2 promoter in response to glucose deprivation. Collectively, our present results suggest that CREB preferentially down-regulates MDM2 and thereby contributing to p53-mediated apoptosis in response to glucose deprivation.     

Caspase- and p53-dependent apoptosis in breast carcinoma cells induced by a synthetic selenadiazole derivative

Selenadiazole derivative is one kind of synthetic organoselenium compounds with potent and broad-spectrum antitumor activity. In this study, we showed that anthrax [1,2-c] [1,2,5] selenadiazolo-6,11-dione (ASDO), an novel selenadiazole derivative, induced time- and dose-dependent apoptotic cell death in MCF-7 human breast carcinoma cells, as indicated by accumulation of sub-G1 cell population, DNA fragmentation, nuclear condensation, caspase activation and PARP cleavage. ASDO-induced apoptosis was significantly inhibited by a general caspase inhibitor z-VAD-fmk, demonstrating the important role of caspases in ASDO-induced apoptotic pathway. Treatment of MCF-7 cells with ASDO resulted in a rapid depletion of mitochondrial membrane potential and release of cytochrome c and Smac/Diablo through up-regulation of Bax, Bad and PUMA expression and down-regulation of Bcl-xl expression. Moreover, ASDO treatment up-regulated the expression levels of total p53 and its target gene p21Waf1. Silencing of p53 activation with RNA interference effectively blocked the ASDO-induced cell PARP cleavage, DNA fragmentation and caspase activation. Furthermore, ASDO-induced apoptosis was interestingly found to be independent of reactive oxygen species production. Taken together, we conclude that ASDO induces MCF-7 cell apoptosis through a p53-dependent and mitochondria-mediated pathway.     

Resveratrol- induced apoptosis is mediated by p53-dependent pathway in Hep G2 cells

Resveratrol, a phytoalexin found in many plants, has been reported to possess a wide range of pharmacological properties and is one of the promising chemopreventive agents for cancer. Here, we examined the antiproliferation effect of resveratrol in two human liver cancer cell lines, Hep G2 and Hep 3B. Our results showed that resveratrol inhibited cell growth in p53-positive Hep G2 cells only. This anticancer effect was a result of cellular apoptotic death induced by resveratrol via the p53-dependent pathway. Here we demonstrated that the resveratrol-treated cells were arrested in G1 phase and were associated with the increase of p21 expression. In addition, we also illustrated that the resveratrol-treated cells had enhanced Bax expression but they were not involved in Fas/APO-1 apoptotic signal pathway. In contrast, the p53-negative Hep 3B cells treated with resveratrol did not show the antiproliferation effect neither did they show significant changes in p21 nor Fas/APO-1 levels. In summary, our study demonstrated that the resveratrol effectively inhibited cell growth and induced programmed cell death in Hepatoma cells on a molecular basis. Furthermore, these results implied that resveratrol might also be a new potent chemopreventive drug candidate for liver cancer as it played an important role to trigger p53-mediated molecules involved in the mechanism of p53-dependent apoptotic signal pathway.     

4-Hydroxynonenal induces p53-mediated apoptosis in retinal pigment epithelial cells

4-Hydroxynonenal (4-HNE) has been suggested to be involved in stress-induced signaling for apoptosis. In present studies, we have examined the effects of 4-HNE on the intrinsic apoptotic pathway associated with p53 in human retinal pigment epithelial (RPE and ARPE-19) cells. Our results show that 4-HNE causes induction, phosphorylation, and nuclear accumulation of p53 which is accompanied with down regulation of MDM2, activation of the pro-apoptotic p53 target genes viz. p21 and Bax, JNK, caspase3, and onset of apoptosis in treated RPE cells. Reduced expression of p53 by an efficient silencing of the p53 gene resulted in a significant resistance of these cells to 4-HNE-induced cell death. The effects of 4-HNE on the expression and functions of p53 are blocked in GSTA4-4 over expressing cells indicating that 4-HNE-induced, p53-mediated signaling for apoptosis is regulated by GSTs. Our results also show that the induction of p53 in tissues of mGsta4 (−/−) mice correlate with elevated levels of 4-HNE due to its impaired metabolism. Together, these studies suggest that 4-HNE is involved in p53-mediated signaling in in vitro cell cultures as well as in vivo that can be regulated by GSTs.     

TNF-alpha promotes Doxorubicin-induced cell apoptosis and anti-cancer effect through downregulation of p21 in p53-deficient tumor cells

p53 is a key regulator in cell apoptosis, and cancer cells deficient in p53 expression fail to respond to chemotherapy. Here we show that effective Doxorubicin (DOX)-induced apoptosis is p53-dependent. However, an alternative treatment of DOX/TNF-alpha/DOX restored sensitivity of p53-deficient cells to DOX-induced apoptosis. Treatment of cells with TNF-alpha resulted in a decrease of p21 (waf1/cip1/sdi1) expression following second dose of DOX. In previous work, we demonstrated that p21 suppressed DOX-induced apoptosis via its (cyclin-dependent kinase) CDK-binding and CDK-inhibitory activity. Thus, we propose that TNF-alpha enhances the anti-cancer effect of DOX through suppressing the anti-apoptotic activity of p21, and that a combined treatment TNF-alpha/Dox is an effective chemotherapeutic strategy for p53-deficient cancers.     

CCN1 induces apoptosis in esophageal adenocarcinoma through p53-dependent downregulation of survivin

Many cancer drugs have been developed to control tumor growth by inducing cancer cell apoptosis. However, several intracellular barriers could fail this attempt. One of these barrier is high expression of survivin. Survivin can interfere caspase activation and thereby abort apoptosis. In this study, we found that CCN1 suppressed the survivin expression in tumor cells of esophageal adenocarcinoma (EAC) and thus allowed apoptosis to finish. Furthermore, we demonstrated that this downregulation was dependent on p53 phosphorylation at Ser20, and CCN1 induced EAC cell apoptosis through the activation of p53.     

Nutlin-3 downregulates p53 phosphorylation on serine392 and induces apoptosis in hepatocellular carcinoma cells

Drug-resistance and imbalance of apoptotic regulation limit chemotherapy clinical application for the human hepatocellular carcinoma (HCC) treatment. The reactivation of p53 is an attractive therapeutic strategy in cancer with disrupted-p53 function. Nutlin-3, a MDM2 antagonist, has antitumor activity in various cancers. The post-translational modifications of p53 are a hot topic, but there are some controversy ideas about the function of phospho-Ser³⁹²-p53 protein in cancer cell lines in response to Nutlin-3. Therefore, we investigated the relationship between Nutlin-3 and phospho-Ser³⁹²-p53 protein expression levels in SMMC-7721 (wild-type TP53) and HuH-7 cells (mutant TP53). We demonstrated that Nutlin-3 induced apoptosis through down-regulation phospho-Ser³⁹²-p53 in two HCC cells. The result suggests that inhibition of p53 phosphorylation on Ser³⁹² presents an alternative for HCC chemotherapy. [BMB Reports 2014; 47(4): 221-226]     

The antiproliferative activity of aloe-emodin is through p53-dependent and p21-dependent apoptotic pathway in human hepatoma cell lines

The aim of this study is to investigate the anticancer effect of aloe-emodin in two human liver cancer cell lines, Hep G2 and Hep 3B. We observed that aloe-emodin inhibited cell proliferation and induced apoptosis in both examined cell lines, but with different the antiproliferative mechanisms. In Hep G2 cells, aloe-emodin induced p53 expression and was accompanied by induction of p21 expression that was associated with a cell cycle arrest in G1 phase. In addition, aloe-emodin had a marked increase in Fas/APO1 receptor and Bax expression. In contrast, with p53-deficient Hep 3B cells, the inhibition of cell proliferation of aloe-emodin was mediated through a p21-dependent manner that did not cause cell cycle arrest or increase the level of Fas/APO1 receptor, but rather promoted aloe-emodin induced apoptosis by enhancing expression of Bax. These findings suggest that aloe-emodin may be useful in liver cancer prevention.