Synergistic inhibition of human lung cancer cell growth by adenovirus-mediated wild-type p53 gene transfer in combination with docetaxel and radiation therapeutics in vitro and in vivo

Chemotherapy given sequentially or concurrently with external beam radiation therapy has emerged as a standard for the treatment of locally advanced lung cancer. Gene therapy by adenovirus-mediated wild-type p53 gene transfer has been shown to inhibit lung cancer growth in vitro, in animal models, and in human clinical trials. However, no information is available on the combined effects of p53 gene transfer, chemotherapy, and radiation therapy on lung cancer growth in vitro and in vivo. Therefore, we developed two-dimensional and three-dimensional isobologram modeling and statistical methods to evaluate the synergistic, additive, or antagonistic efficacy among these therapeutic agents in human non-small cell lung cancer cell lines A549, H460, H322, and H1299, at the ID₅₀ and ID₅₀ levels. The combination of these three therapeutic agents exhibited synergistic inhibitory effects on tumor cell growth in all four cell lines at both the ID₅₀ and the ID₈₀ levels in vitro. In mouse models with H1299 and A549 xenografts, combined treatment synergistically inhibited tumor growth in the absence of any apparent increase in toxicity, when compared with other treatment and control groups. Together, our findings suggest that a combination of gene therapy, chemotherapy, and radiation therapy may be an effective strategy for human cancer treatment.