Radiotherapy is the common treatment of choice for locally advanced lung cancer, but the radioresistance of lung cancer remains a significant therapeutic obstacle. We previously demonstrated that adenovirus-mediated inhibitor of growth 4 (ING4) tumor suppressor gene delivery (AdVING4) can chemosensitize human hepatocarcinoma cells to anticancer drug cisplatin (CDDP). However, its radiosensitizing effects in cancer therapy are largely elusive. In the present study, we investigated the therapeutic efficacy of AdVING4 gene therapy combined with ionizing radiotherapy for SPC-A1 human non-small-cell lung cancer (NSCLC) cells in vitro and in vivo in athymic nude mice, and also elucidated its underlying mechanisms. We found that AdVING4 gene therapy plus radiotherapy induced synergistic tumor suppression and apoptosis in in vitro SPC-A1 human NSCLC cells and in vivo SPC-A1 xenografted tumors s.c. implanted in athymic nude mice. Mechanistically, AdVING4 combined with radiation resulted in a substantial upregulation of Bax, Fas, FasL and Cleaved Caspase-3, and downregulation of Bcl-2 in SPC-A1 human NSCLC xenografted tumors. In addition, AdVING4 plus radiation synergistically reduced the tumor vessel CD34 expression and microvessel density (MVD) in vivo. Most importantly, AdVING4 potentially blocked the radiation-induced enhancement of cyclooxygenase-2 and survivin radioresistant factors, and vascular endothelial growth factor and IL-8 proangiogenic factors. The enhanced antitumor effects elicited by AdVING4 plus radiotherapy were closely associated with the cooperative activation of intrinsic and extrinsic apoptotic pathways, and synergistic inhibition of tumor angiogenesis. Thus, our results suggested that AdVING4 combined with radiotherapy may be a feasible and effective strategy for treatment of radioresistant NSCLC and other cancers.