Angiogenic activities are increased via upregulation of HIF-1α expression in gefitinib-resistant non-small cell lung carcinoma cells

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) have been used to treat patients with non-small cell lung cancer (NSCLC) and activating EGFR mutations; however, the emergence of secondary mutations in EGFR or the acquisition of resistance to EGFR-TKIs can develop and is involved in clinical failure. Since angiogenesis is associated with tumor progression and the blockade of antitumor drugs, inhibition of angiogenesis could be a rational strategy for developing anticancer drugs combined with EGFR-TKIs to treat patients with NSCLC. The signaling pathway mediated by hypoxia-inducible factor-1 (HIF-1) is essential for tumor angiogenesis. The present study aimed to identify the dependence of gefitinib resistance on HIF-1 alpha activity using angiogenesis assays, western blot analysis, colony formation assay, xenograft tumor mouse model and immunohistochemical analysis of tumor tissues. In the NSCLC cell lines, HIF-1 alpha protein expression levels and hypoxia-induced angiogenic activities were found to be increased. In a xenograft mouse tumor model, tumor tissues derived from gefitinib-resistant PC9 cells showed increased protein expression of HIF-1 alpha and angiogenesis within the tumors. Furthermore, inhibition of HIF-1 alpha suppressed resistance to gefitinib, whereas overexpression of HIF-1 alpha increased resistance to gefitinib. The results from the present study provides evidence that HIF-1 alpha was associated with the acquisition of resistance to gefitinib and suggested that inhibiting HIF-1 alpha alleviated gefitinib resistance in NSCLC cell lines.

Automated summary

The study focused on the dependence of gefitinib resistance on HIF-1 alpha activity, showing that HIF-1 alpha was associated with the acquisition of resistance to gefitinib in NSCLC cell lines. Inhibition of HIF-1 alpha alleviated gefitinib resistance, indicating a potential strategy for developing anticancer drugs in combination with EGFR-TKIs for NSCLC patients.