The cytotoxic effect of E1B 55-kDa mutant adenovirus on human hepatocellular carcinoma cell lines

Recombinant adenovirus IL-24-Bax promotes apoptosis of hepatocellular carcinoma cells in vitro and in vivo

Gene therapy promises to become an alternative choice for the treatment of hepatic cancer. In many cancers, the delivery of chimeric proteins by adenovirus vector has been reported to induce apoptosis. This study was performed to evaluate whether the recombinant adenovirus interleukin (IL)-24-Bax can induce apoptosis in hepatocellular carcinoma cells in vitro and in vivo. Several recombinant adenoviruses were constructed, and the expression of their encoded proteins was measured. The effects of the recombinant adenovirus on hepatocellular carcinoma cells and the normal hepatocyte cell line were investigated through cell viability and apoptosis assays after the cells were treated with Ad.Luc, Ad.IL-24, Ad.Bax or Ad.IL-24-Bax. The mechanism involved was also explored. A tumor-bearing mouse model was used to evaluate the effects of the adenovirus on tumor volume and cell apoptosis in vivo. Ad.IL-24-Bax selectively suppressed growth of hepatocellular carcinoma cells and induced apoptosis, but it had little influence on the normal hepatocytes. The mechanism of this response may include the effect of the 10HRE/VEGF385 promoter and the synergistic effect of IL-24 and Bax. Ad.IL-24-Bax also suppressed tumor growth in nude mice and induced apoptosis. Ad.IL-24-Bax may be a useful tool for gene therapy of hepatic cancer.

TIP30 induces apoptosis under oxidative stress through stabilization of p53 messenger RNA in human hepatocellular carcinoma

Reactive oxygen species (ROS) and cellular oxidant stress have long been associated with cancer. Here, we show that TIP30, also called CC3, regulates p53 mRNA stability and induces apoptosis by sensing of intracellular oxidative stress in human hepatocellular carcinoma (HCC) cells. Introduction of TIP30 induced more cell death in HepG2 cells with a high level of intracellular ROS than that in normal liver cell line, HL7702, which had low level of intracellular ROS. Treatment with an antioxidant agent attenuated TIP30-induced cell death in HepG2 cells, whereas oxidant H(2)O(2) augmented TIP30-induced cell death in HL7702 cells. The conformation of TIP30 was altered with the formation of an intermolecular disulfide bridge under oxidative stress. TIP30 greatly enhanced p53 expression and its transcriptional activity under oxidative stress, which was probably through stabilization of p53 mRNA. TIP30 induced apoptosis and mitochondrial dysfunction were blocked by silencing of p53 expression. The nuclear import of mRNA-binding protein HuR was blocked upon TIP30 introduction, which might be due to the interruption of the association of HuR with importin beta2. The elevated cytoplasmic HuR bound to p53 mRNA 3'-untranslated region, resulting in prolonged half-life of p53 mRNA. Our results suggest that TIP30 is involved in cellular oxidative stress surveillance and induces apoptosis through stabilization of p53 mRNA in HCC cells.

Gene therapy of neoplastic liver diseases

Since advanced liver cancer lacks effective therapy in most cases, a considerable interest has been drawn towards gene therapy. Natural or chimerical genes can be transferred to the tumour itself, the non-tumoral liver, or even distant tissues using a variety of vectors administered by intratumoral or intravascular routes. The desired selectivity in gene expression can be achieved by increasing the specificity of gene delivery or by controlling gene expression with tumour-specific promoters, such as alpha-fetoprotein or carcinoembryonic antigen. There are two main approaches to gene therapy of liver cancer aiming at killing directly malignant cells or at improving the host's defensive systems, respectively. The former include replacing the lost function of tumour suppressor genes, inhibiting the action of activated oncogenes, sensitising tumour cells to prodrugs, or infecting the tumoral tissue with viruses that replicate selectively in cancer cells. Host defences can be improved by stimulating the antitumoral immune response, or by interfering with tumour vessel formation. Progress in gene therapy of liver cancer depends very much on information collected from well-designed clinical trials. This information includes knowledge of whether an efficient gene transfer has been achieved and what is the duration and magnitude of gene expression in the transduced tissues. Hopefully, magnetic resonance or positron emission tomography (PET) may turn out to be reliable procedures for tracing transgene expression in humans. Pre-clinical evidence and early clinical trials strongly suggest that there is a place for gene therapy of liver malignancies.

Toward a new generation of conditionally replicating adenoviruses: pairing tumor selectivity with maximal oncolysis

Conditionally replicating adenoviruses (CRADs) represent a promising new platform for the treatment of cancer. CRADs have been demonstrated to kill tumor cells when other therapies fail, indicating that their antitumor properties are complementary to, and distinct from, those of standard treatments such as chemotherapy and radiation. In clinic trials CRADs have shown encouraging results, demonstrating mild side effects when administered at high doses and via different routes, including intratumorally, intraperitoneally, and intravenously. Tumor-selective replication has been detected, although as a single agent the efficacy appears to be limited. Interestingly, combined treatment with radiation or chemotherapy has been found to enhance CRAD efficacy considerably. To date, the molecular mechanisms underlying adenovirus-mediated oncolysis, and the way in which chemotherapy enhances oncolysis, are not well understood. A fuller knowledge of these processes will open up new strategies to improve the cell-killing potential of CRADs. Here, we discuss several possibilities that may lead to CRADs with enhanced oncolytic activity. These approaches include strategies to functionally couple tumor targeting and optimal oncolytic activity, and ways to further increase tumor cell disruption at later stages of infection to facilitate the spreading of virus throughout the tumor mass. In addition, improved methods to evaluate the efficacy of these agents in animal models, and in the clinic, will be required to systematically test and optimize CRAD efficacy, also taking into account the influence of tumor characteristics and the administration route.

Gene therapy for malignant liver disease

For most patients with advanced or multifocal hepatocellular carcinoma (HCC) or with metastatic malignant liver disease treatment options are limited, resulting in a poor prognosis. Novel therapeutic strategies such as gene therapy are therefore urgently required. Gene therapeutic approaches use gene delivery systems (vectors) to introduce DNA constructs as therapeutic agents into living cells. Antitumour strategies include the reintroduction of tumour suppressor genes into tumour cells, the expression of foreign enzymes to render tumours susceptible to treatment with chemotherapeutic agents and the enhancement of tumour immunogenicity by expressing immunomodulatory genes or by genetic vaccination with tumour antigens. Furthermore, gene therapy may be also used for anti-angiogenesis to reduce tumour growth and metastatic potential. Other novel approaches aim at the development of genetically altered replication competent viruses, which selectively replicate in tumour cells inducing cell lysis. Although most clinical trials of antitumour gene therapy so far have failed to induce strong therapeutic effects, further improvement of antitumour gene therapy may finally result in potent clinical treatment options for patients with malignant liver tumours.