Effects of combined inhibition of STAT3 and VEGFR2 pathways on the radiosensitivity of non-small-cell lung cancer cells.

Abstract

PurposeThe goals of this study were to determine the effects of combined inhibition of STAT3 and vascular endothelial growth factor receptor 2 (VEGFR2) pathways on the radiosensitivity of non-small-cell lung cancer (NSCLC) cells, and to assess the underlying mechanisms.MethodsThe expressions of VEGFR2, STAT3, related signaling molecules, hypoxia-inducible factor 1-alpha (HIF-1α), and cyclin D1 were determined by Western blotting. Radiosensitivity was assessed using the colony-forming assay, and cell cycle and cell death were analyzed by flow cytometry. A nude mouse xenograft tumor model of Calu-1 cells was established. The hepatorenal toxicity of the above-mentioned treatment on tumor-bearing mice was observed by H&E staining. The expression of STAT3, VEGFR2, HIF-1α, and cyclin D1 of the transplanted tumor tissues was detected by immunohistochemistry. Apoptosis of tumor tissues was evaluated by TUNEL staining.ResultsIn vitro, we selected two cell lines with high expression levels of STAT3, including Calu-1 cells that exhibit high VEGFR2 expression and A549 cells that exhibit low VEGFR2 expression. When apatinib treatment was combined with S3I-201, the expression of VEGFR2, STAT3, and their downstream signaling molecules was significantly decreased (P<0.01). There was an increase in cell death and G2/M phase arrest after treatments, with the most significant changes occurring upon dual inhibition of STAT3 and VEGFR2 (P<0.01). In vivo, combined treatment of radiotherapy and dual inhibition of VEGFR2 and STAT3 was well tolerated and did not deliver additional toxicity. Compared with the control group and the radiation treatment (RT) + apatinib or RT + S3I-201 duplex group, the expression level of STAT3, p-STAT3, VEGFR2, HIF-1α, and cyclin D1 in the triple group (RT + apatinib + S3I-201) was the lowest, and the proportion of apoptotic cells was the highest (P<0.05).ConclusionThe combined inhibition of VEGFR2 and STAT3 is effective in enhancing radiosensitizing effects in NSCLC cells.