Development of a novel recombinant adenovirus containing gfp–zeocin fusion expression cassette for conditional replication in p53-deficient human tumor cells

Gene Therapy Applications of Viral Vectors

Viral vectors have frequently been applied in gene therapy with the final goal of treating various diseases in the areas of neurology, neurodegeneration, metabolic disease, and cancer. Vectors have been engineered based on AAV, adenoviruses, alphaviruses, herpes simplex viruses, lentiviruses, and retroviruses. Some vectors are suitable for short-term episomal transgene expression, whereas others are integrated into the host cell genome to provide long-term expression. Additionally, hybrid vectors with favorable features from different viruses have been developed. Therapeutic genes of choice have typically been toxic genes such as thymidine kinase, pro-apoptotic genes like Bax, and immunostimulatory genes (for instance, interleukin-12). A large number of animal studies have demonstrated proof of concept of viral gene therapy. Many types of viral vectors have been employed in more than 700 clinical trials that have been carried out or are currently in progress.

Enhanced TRAIL sensitivity by E1A expression in human cancer and normal cell lines: inhibition by adenovirus E1B19K and E3 proteins

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily of cytokines that induces apoptosis in a variety of cancer cells, but not in normal cells. However, more and more tumor cells remain resistant to TRAIL, which limited its application for cancer therapy. Expression of the adenovirus serotype 5 (Ad5) E1A sensitizes tumor cells to apoptosis by TNF-alpha, Fas-ligand, and TRAIL. Here we asked whether E1A overcomes this resistance and enhances TRAIL-induced apoptosis in the tumor cells. Our results revealed that the tumor cell lines, HeLa and HepG2, with infection by Ad-E1A, were highly sensitive to TRAIL-induced apoptosis. Importantly, we found that in normal primary human lung fibroblast cells (HLF) TRAIL is capable of inducing apoptosis in combination with E1A as efficiently as in some tumor cell lines. The adenovirus type 5 encoding proteins, E1B19K and E3 gene products, have been shown to inhibit E1A and TRAIL-induced apoptosis of HLF cells by using the recombinant adenovirus AdDeltaE1B55K, with mutation of E1B55K, containing E1B19K and complete E3 region. Further results demonstrated that the expression of DR5 and TRAIL was down-regulated in the AdDeltaE1B55K co-infected HLF cells. These findings suggest that TRAIL may play an important role in limiting virus infections and the ability of adenovirus to inhibit killing may prolong acute and persistent infections. The results from this study have also suggested the possibility that the combination of E1A with TRAIL could be used in the treatment of human malignancy, or in the selection of the optimal adenovirus mutant as effective delivering vector for cancer therapy.