Curcumin inhibits human non-small cell lung cancer xenografts by targeting STAT3 pathway

Human non-small cell lung cancer (NSCLC) is the most common cause of cancer-related death in men. Signal transducers and activators of transcription 3 (STAT3) is a potential molecular target in angiogenesis-mediated cancer therapy. In this study, we subcutaneously injected athymic nude mice with NCI-H460 cells to induce ectopic xenograft model, and treated the animals with curcumin (100 mg/kg) or vehicle by oral gavage. Tumor size and tumor weight were significantly reduced by curcumin treatment. Besides, curcumin significantly decreased hemoglobin content and mRNA expression of CD31 and CD105 in tumor tissue, suggesting that curcumin could inhibit angiogenesis in NSCLC xenograft. Similarly, we intrathoracally injected athymic nude mice with H1975 cells to induce orthotopic xenograft model, in which curcumin significantly reduced tumor weight as well as improved the survival rate of mice. STAT3 pathway was involved in curcumin-induced tumor inhibition, in which phosphorylation of STAT3 and JAK in ectopic xenograft were both declined after curcumin treatment, and the STAT3-regulated promoter activation of VEGF, Bcl-xL, Cyclin D1 was also significantly reduced after treatment. In in vitro assays, curcumin significantly inhibited cell migration and tube formation of NCI-H460 cells, but transfection with pMXs-Stat3C, a dominant active mutant, could abolish the inhibitory effects of curcumin on the cells, suggesting curcumin inhibited tumor angiogenesis of NCI-H460 cells through the inactivation of STAT3. All data showed that curcumin could be a potential drug targeting STAT3 to treat NSCLC.