Characterization of HIV-1 TAT peptide as an enhancer of HSV-TK/GCV cancer gene therapy

Curcumin plays a synergistic role in combination with HSV-TK/GCV in inhibiting growth of murine B16 melanoma cells and melanoma xenografts

Melanoma is a global concern and accounts for the major mortality of skin cancers. Herpes simplex virus thymidine kinase gene with ganciclovir (HSV-TK/GCV) is a promising gene therapy for melanoma. Despite its low efficiency, it is well known for its bystander effect which is mainly mediated by gap junction. In this study, we found that curcumin reduced B16 melanoma cell viability in both time- and dose-dependent manner. Further study showed that curcumin improved the gap junction intercellular communication (GJIC) function, and upregulated the proteins essential to gap junction, such as connexin 32 and connexin 43, indicating the potential role in enhancing the bystander effect of HSV-TK/GCV. By co-culturing the B16^TK cells, which stably expressed TK gene, with wildtype B16 (B16^WT) cells, we found that co-treatment of curcumin and GCV synergistically inhibited B16 cell proliferation, but the effect could be eliminated by the gap junction inhibitor AGA. Moreover, curcumin markedly increased apoptosis rate of B16^WT cells, suggesting its effect in enhancing the bystander effect of HSV-TK/GCV. In the in-vivo study, we established the xenografted melanoma model in 14 days by injecting mixture of B16^TK and B16^WT cell in a ratio of 3:7. The result demonstrated that, co-administration of curcumin and GCV significantly inhibited the xenograft growth, as indicated by the smaller size and less weight. The combinational effect was further confirmed as a synergistic effect. In conclusion, the results demonstrated that curcumin could enhance the killing effect and the bystander effect of HSV-TK/GCV in treating melanoma, which might be mediated by improved gap junction. Our data suggested that combination of HSV-TK/GCV with curcumin could be a potential chemosensitization strategy for cancer treatment.

Suicide gene therapy using reducible poly (oligo-D-arginine) for the treatment of spinal cord tumors

Suicide gene therapy based on a combination of herpes simplex virus-thymidine kinase (HSV-tk) and ganciclovir (GCV) has obstacles to achieving a success in clinical use for the treatment of cancer due to inadequate thymidine kinase (TK) expression. The primary concern for improving anticancer efficacy of the suicide gene therapy is to develop an appropriate carrier that highly expresses TK in vivo. Despite great advances in the development of non-viral vectors, none has been used in cancer suicide gene therapy, not even in experimental challenge. Reducible poly (oligo-D-arginine) (rPOA), one of the effective non-viral carriers working in vivo, was chosen to deliver HSV-tk to spinal cord tumors which are appropriate targets for suicide gene therapy. Since the system exerts toxicity only in dividing cells, cells in the central nervous system, which are non-proliferative, are not sensitive to the toxic metabolites. In the present study, we demonstrated that the locomotor function of the model rat was maintained through the tumor suppression resulting from the tumor-selective suicide activity by co-administration of rPOA/HSV-tk and GCV. Thus, rPOA plays a crucial role in suicide gene therapy for cancer, and an rPOA/HSV-tk and GCV system could help promote in vivo trials of suicide gene therapy.

Not gene therapy, but genetic surgery-the right strategy to attack cancer

In this review, I will suggest to divide all the approaches united now under common term "gene therapy" into two broad strategies of which the first one uses the methodology of targeted therapy with all its characteristics, but with genes in the role of agents targeted at a certain molecular component(s) presumably crucial for cancer maintenance. In contrast, the techniques of the other strategy are aimed at the destruction of tumors as a whole using the features shared by all cancers, for example relatively fast mitotic cell division or active angiogenesis. While the first strategy is "true" gene therapy, the second one is more like genetic surgery when a surgeon just cuts off a tumor with his scalpel and has no interest in knowing delicate mechanisms of cancer emergence and progression. I will try to substantiate the idea that the last strategy is the only right one, and its simplicity is paradoxically adequate to the super-complexity of tumors that originates from general complexity of cell regulation, strongly disturbed in tumor cells, and especially from the complexity of tumors as evolving cell populations, affecting also their ecological niche formed by neighboring normal cells and tissues. An analysis of the most widely used for such a "surgery" suicide gene/prodrug combinations will be presented in some more details.

NT-polyplex: a new tool for therapeutic gene delivery to neuroblastoma tumors

Neurotensin (NT)-polyplex is a nonviral system for the targeted gene delivery to cells that express and internalize the high-affinity NT receptor (NTSR1). In hemiparkinsonian rats, we previously demonstrated the morphological and functional recovery from dopaminergic neurodegeneration using the NT-polyplex as a vehicle to transfect a neurotrophic gene. The main objective of this work was to demonstrate the feasibility of NT-polyplex to transfect reporter or therapeutic genes into neuroblastoma tumors through the blood stream or by intratumoral injection. N1E-115 cells known to express NTSR1 were allografted into athymic mice to generate the neuroblastoma tumor model. Both routes of administration allowed the NT-polyplex to reach and transfect tumoral cells. A low transgene expression was also detected in intestinal tract cells only after the injection into the blood stream. The transfection of the thymidine kinase (HSVTK) suicide gene followed by ganciclovir (GCV) treatment decreased the size and weight of neuroblastoma tumors by 30-50% and increased apoptosis compared to controls. This study shows the potential of the NT-polyplex as specific gene-transfer system for NTSR1 cancer cells.