Studies have shown that suppression of both the JAK/STAT3 pathway and epithelial‑mesenchymal transition (EMT) may overturn the resistance of non‑small cell lung cancer (NSCLC) cells to gefitinib. Zoledronic acid (ZA) injection is used to treat and prevent multiple forms of osteoporosis, hypercalcemia and bone metastasis‑related complications of malignancy. Clinical research has shown that ZA may exert antitumour effects and delay the progression of NSCLC. In the present study, we investigated whether ZA combined with gefitinib could re‑sensitise NSCLC cells to gefitinib in vitro and in vivo through inhibition of the JAK/STAT3 signalling pathway and EMT reversal. The results revealed that ZA potently increased the sensitivity of gefitinib‑resistant lung cancer cells to gefitinib. ZA decreased activation of JAK/STAT3 signalling and reversed EMT in the H1975 and HCC827GR cell lines. Furthermore, addition of IL‑6 to ZA‑pretreated gefitinib‑resistant cell lines abrogated the effect of ZA and restored the cellular resistance to tyrosine kinase inhibitors. Finally, ZA‑based combinatorial therapy effectively inhibited the growth of xenografts derived from gefitinib‑resistant cancer cells, which was correlated with the inhibition of the JAK/STAT3 signalling pathway and EMT reversal. In conclusion, ZA re‑sensitised gefitinib‑resistant lung cancer cells through inhibition of the JAK/STAT3 signalling pathway and EMT reversal. The combination of ZA and gefitinib may be a promising therapeutic strategy to reverse gefitinib resistance and prolong the survival of patients with NSCLC.
Keywords: zoledronic acid; NSCLC; non-small cell lung cancer; gefitinib resistance; JAK/STAT3; epithelial-mesenchymal transition.