Immune response to fused core protein of hepatitis C virus and truncated tetanus toxin peptides in mice.

Because no vaccine or effective therapy is available, thousands of people with HCV have died in recent years. Cytotoxic T lymphocytes (CTLs) play a critical role in the host cellular immune response against HCV. CTL epitopes in HCV core protein have been identified and used in vaccine development. T helper epitopes could promote cytokine secretion and antibody production to fight HCV. Tetanus toxin, an immunogen with many T helper epitopes, was once used in HBV therapeutic vaccine design. Here, eukaryotic and prokaryotic expression vectors were constructed to express truncated fragments of tetanus toxin and core genes of HCV. HLAA2.1 transgenic mice were inoculated with a recombinant plasmid vehicle with these two heterogenic gene fragments, and this augmented the titres of antibody against HCV. Antigen-specific lymphocyte proliferation, Th1 and Th2 cytokine levels and the number of lysed cells were markedly increased in the combined immunization group compared to controls. These findings provide new insights into a potential role for T helper epitopes from tetanus toxin combined with protein from the HCV core gene, which has numerous CTL epitopes. This design strategy may aid in the development of new vaccines against HCV.

Production and characterization of monoclonal antibody specific for NS3 helicase of hepatitis C virus.

Hepatitis C virus (HCV) infection is the major etiological agent of chronic hepatitis, which leads to liver cirrhosis and hepatocellular carcinomas. HCV NS3 helicase is a promising target of anti-virus therapy. In this report, we discuss a strategy to generate monoclonal antibodies (MAbs) of the HCV NS3 helicase, and investigate its potential characteristic. Our results showed the production of MAbs against NS3 helicase, which could specifically recognize the native NS3 helicase in transiently transfected cells in the immunofluorescence experiment. The resultant MAbs were used as the first antibody in Western blot analyses, and observed the specific band that defines the NS3 helicase. Likewise, one MAb could inhibit the NS3 helicase enzymatic activity distinctly in the NS3 helicase-mediated DNA-unwinding assay. To conclude, these antibodies may be useful to generate specific diagnostic tools for HCV infection and may also be developed for potential therapeutics.

The BH3-only protein PUMA is involved in green tea polyphenol-induced apoptosis in colorectal cancer cell lines.

The green tea polyphenol (GTP) has been shown to possess cancer therapeutic effect through induction of apoptosis, while the underlying molecular mechanism of its anticancer effect is not well understood. PUMA (p53-upregulated modulator of apoptosis) plays an important role in the process of apoptosis induction in a variety of human tumor cells in both p53-dependent and -independent manners. However, whether or not PUMA is involved in the process of GTP-induced apoptosis in cancer cells has not been well reported. In the present study, we treated HT-29 (mutant p53) and LoVo (wild type p53) human colorectal cancer cells with different concentrations of GTP, which led to repression of cell proliferation and induction of apoptosis in both cell lines. Meanwhile, we also observed increased PUMA expression and decreased ERK (extracellular signal-regulated kinase) activity in both of GTP-treated tumor cell lines carrying different genotypes of p53. To determine the role of PUMA in GTP-induced apoptosis, we used stable RNA interference (RNAi) to suppress PUMA expression. As a result, apoptosis was abrogated in response to GTP-treatment. We also found that suppression of ERK activity by either RNAi or its specific inhibitor significantly enhanced GTP-induced PUMA expression. All these results indicate that PUMA plays a critical role in GTP-induced apoptosis pathway in human colorectal cancer cells and can be regulated partly by ERK inactivation. Demonstration of the molecular mechanism involved in the anti-cancer effect of GTP may be useful in the therapeutic target selection for p53 deficient colorectal cancer.

Inducing apoptosis and enhancing chemosensitivity to gemcitabine via RNA interference targeting Mcl-1 gene in pancreatic carcinoma cell.

PURPOSE: Resistance to chemotherapy is a major cause of treatment failure and poor prognosis in pancreatic carcinoma. Myeloid cell leukemia-1 (Mcl-1) is highly up-regulated in pancreatic carcinoma and is associated with the anti-apoptosis and the resistance to chemotherapy drugs. Suppression of Mcl-1 would be an approach to induce apoptosis and enhance the chemosensitivity. METHODS: In this study, three pancreatic cancer cell lines (PANC-1, BxPC-3 and SW1900) stably expressing shRNAs targeting Mcl-1 gene were established and gene expression inhibition was assessed by Real-Time QPCR and Western blotting. The effects of Mcl-1 downregulation mediated by RNAi were explored in vitro and in vivo. RESULTS: We showed that the specific downregulation of Mcl-1 strikingly inhibited cell growth, colony formation, cell cycle arrest and induced apoptosis in pancreatic cancer cells in vitro, and markedly decreased the tumorigenicity in a mouse xenograft model. Moreover, knockdown of Mcl-1 significantly increased the chemosensitivity to Gemcitabine in pancreatic carcinoma cells. CONCLUSIONS: Our data suggests that the specific downregulation of Mcl-1 by RNAi is a promising approach to induce apoptosis and enhance the chemosensitivity for pancreatic carcinoma gene therapy.

Prognostic significance of stathmin expression in correlation with metastasis and clinicopathological characteristics in human ovarian carcinoma.

Stathmin, also called oncoprotein 18, is a founding member of the family of microtubule-destabilizing proteins that play a critical role in the regulation of mitosis. Stathmin is non-expressed in normal tissues, but stathmin gene is expressed at high levels in many human malignancies and the relationships between the levels of this gene expression in tumors and prognosis of the patients have been addressed. In this report, we explored the relationships between stathmin mRNA expression in ovarian carcinoma tissues and clinicopathological parameters. We collected and analyzed paraffin wax-embedded ovarian tumor biopsy tissues from 42 ovarian cancer patients in our hospital. We employed RT-PCR method and performed a densitometric analysis to determine the ratio of stathmin relative to beta-actin as an internal marker. Results showed that the stathmin mRNA expression was detected in all the ovarian carcinoma tissue samples and those samples with metastasis had higher levels of stathmin mRNA expression in initial biopsy specimens (P<0.05). Moreover, the levels of stathmin mRNA expression between samples with and without metastasis showed a statistically significant difference (P<0.05).

Suppression of Bcl-xL expression by a novel tumor-specific RNA interference system inhibits proliferation and enhances radiosensitivity in prostatic carcinoma cells.

Bcl-xL, a novel member of anti-apoptotic Bcl-2 family that play important roles in regulating cell survival and apoptosis, is frequently overexpressed in various kinds of human cancers, including prostatic carcinoma. To explore its possibility as a therapeutic target for prostatic carcinoma, we developed a novel tumor-specific RNA interference system by using survivin promoter and employed it to suppress exogenous reporters (LUC and EGFP) and endogenous gene Bcl-xL expression and analyzed its phenotypes. We found that expression of exogenous reporters (LUC and EGFP) was specifically inhibited in tumor cells but not in normal cells. We also observed that the specific inhibition of Bcl-xL in human prostatic carcinoma cells (PC3) strongly suppressed in vitro cell proliferation and in vivo tumorigenicity. We observed significant apoptosis induction and radiosensitivity enhancement in PC3 cells by the RNA interference-mediated suppression of Bcl-xL expression. All these results indicate that inhibition of Bcl-xL expression can result in potent antitumor activity and radiosensitization in human prostatic carcinoma.

Inhibiting proliferation and enhancing chemosensitivity to taxanes in osteosarcoma cells by RNA interference-mediated downregulation of stathmin expression.

Stathmin (Oncoprotein18), a signal transduction regulatory factor, plays an important role in cell division and malignant tumor development. Stathmin is a ubiquitous intracellular phosphoprotein that is overexpressed in a variety of human malignancies, including osteosarcoma. To investigate the potential use of stathmin as a therapeutic target for human osteosarcomas, we employed RNA interference [small interfering RNA (siRNA)] to reduce stathmin expression in human osteosarcoma cell lines and analyzed their phenotypic changes. Results showed that the downregulation of stathmin expression in human osteosarcoma cells significantly inhibited cell proliferation in vitro and tumorigenicity in vivo. The specific downregulation induced cell arrest in the G(2)/M phase of cell cycle and eventually apoptotic cell death. Taxanes are a group of effective chemotherapeutic agents whose activity is mediated through stabilization of the microtubules of the mitotic spindle. In the present study, we also observed a synergistic enhancement of the cytotoxicity effect by combination use of taxanes and RNA interference-mediated stathmin downregulation. All these experimental data indicate that stathmin downregulation can lead to potent antitumor activity and chemosensitizing activity to taxanes in human osteosarcomas.

The therapeutic potential of survivin promoter-driven siRNA on suppressing tumor growth and enhancing radiosensitivity of human cervical carcinoma cells via downregulating hTERT gene expression.

Human telomerase is a ribonucleoprotein complex composed of two subunits, an RNA component (hTR) and a human telomerase reverse transcriptase component (hTERT). The activation of telomerase, a process regulated by the human telomerase reverse transcriptase (hTERT), is a crucial step during cellular immortalization and malignant transformation. hTERT is overexpressed in most malignant cells but undetectable in most normal somatic cells. To explore its possibility as a therapeutic target for human cervical carcinoma, we developed a novel tumor-specific RNA interference system targeting hTERT by using the survivin promoter and investigated the effects of it on the proliferation, apoptosis and radiosensitivity in human cervical carcinoma cells (HeLa). The treatment of HeLa cells by hTERT gene RNAi not only could inhibit the proliferation of human cervical carcinoma cells (HeLa), but also could enhance the radiosensitivity of those cells via downregulation of their mRNA and protein expression. Therefore, survivin promoter-driven siRNA expression vector targeting hTERT may have potential use in radiosensitization therapy with targeted tumor gene silencing effect in human cervical carcinomas.