Broad strategies into engineering superior targeted gene therapy vectors derived from bacteriophage viruses

Abstract

Chemotherapy is the most commonly used treatment for cancer. While chemotherapeutic drugs such as doxorubicin provide cure in some cases, chemotherapy is toxic and has serious side-effects. Another disadvantage is that some types of cancer develop resistance to chemotherapy. Lowering the doses of these drugs will make them safer but would decrease their efficacy. A solution to this would be to combine low doses of these anticancer drugs with a safe anticancer approach. Cancer gene therapy is an alternative and promising approach of cancer treatment. In our group we are using the adeno-associated virus/phage, named AAVP vector, which is a hybrid vector between AAV and phage genomes. AAVP vector was engineered to display the RGD4C peptide which binds to αv integrin receptors overexpressed in tumors. AAVP vector has been proven to be safe and efficient vector for targeted gene delivery to tumors, upon intravenous administration. The aim of my project was to combine low-dose of doxorubicin with AAVP vector in order to investigate the drug effects on the AAVP-mediated tumor cell killing. We also tested the combination of AAVP with the natural dietary genistein, an isoflavone present in soy, regarded as a phytoestrogen and proven for its anti-cancer activity. Epidemiological studies have shown that a soy-rich diet has cancer-preventive effects. We found that combination of low doses (non-toxic) of doxorubicin or genistein with RGD4C-AAVP-guided gene therapy resulted in greater tumor cell killing than treatment with doxorubicin, genistein or the targeted vector alone. In addition, we uncovered the mechanism that doxorubicin and genistein increased the transduction efficiency of AAVP vectors. In conclusion, our results suggest that the combined treatment of doxorubicin or genistein with targeted RGD4C-AAVP gene therapy is a novel, promising, non-invasive and, importantly, safer treatment approach. Therefore, this combined treatment should be considered for future preclinical studies to assess its efficacy in vivo in tumor-bearing animals.