An adenovirus encoding proapoptotic Bax induces apoptosis and enhances theradiation effect in human ovarian cancer

Overexpression of proapoptotic Bar favors death in cells resistant to ioniz ing radiation. We hypothesized that expression of Bar via adenoviral-mediat ed gene delivery could sensitize radiation-refractory cells to radiotherapy . An inducible Bar recombinant adenovirus (Ad/Bax) had been generated using the Cre/loxp system. Human ovarian cancer cell lines and primary, patient- derived cancer cells from ascites were irradiated and infected with the Ad/ Bar and an expression-inducing vector, Ad/Cre. Cell death was evaluated by crystal violet staining, fluorescence-activated cell sorter analysis of Ann exin V, and colony formation assay (cell lines only). To further characteri ze the mechanism of death, cell morphology was examined by nuclear staining with Hoechst 33258. Lastly, to evaluate the capacity of the combined treat ment to inhibit tumor growth, mice were injected subcutaneously with ovaria n cancer cells exposed to Bar, radiation therapy (RT), or both, and tumor s ize was measured periodically. Infection of the cancer cell lines and prima ry cells with both Ad/Bar and Ad/Cre significantly enhanced sensitivity to ionizing radiation, achieving high levels of cell killing in short-term ass ays. In addition, the combination of Bar and radiotherapy reduced the survi val fraction of cell lines 2 logs in standard colony-forming assays. Invest igation into the involved mechanism suggests that Bar-mediated radiosensiti zation occurs through both apoptosis and necrosis pathways. Further, mice s ubcutaneously injected with ovarian tumor cells previously treated with rad iation, or with radiation and irrelevant viruses, consistently developed tu mor nodules. In addition, approximately 80% of injections were followed by tumor formation after treatment with Ad/Bar and Ad/Cre alone. In contrast, tumor formation was completely inhibited after combined treatment with Ad/B ar and Ad/Cre and radiation. Augmentation of the effect of radiotherapy on human ovarian cancer cells and primary cancer cells from patients via a rec ombinant adenovirus encoding Bar is feasible.