miR-223 enhances the sensitivity of non-small cell lung cancer cells to erlotinib by targeting the insulin-like growth factor-1 receptor

Lung cancer is the leading cause of cancer-related fatalities worldwide, and non-small cell lung cancer (NSCLC) is the main pathological type. MicroRNAs (miRNAs or miRs) are a class of small non-coding RNAs, which are involved in tumor initiation and progression. miR-223 is a tumor suppressor miRNA that has been reported in various types of cancer, including lung cancer. In the present study, to characterize the biological behavior of miR-223 in NSCLC, we established an miR-223 overexpression model in erlotinib-resistant PC-9 (PC-9/ER) cells by infection with lentivirus to induce the overexpression of miR-223. As a result, miR-223 enhanced the sensitivity of the PC-9/ER cells to erlotinib by inducing apoptosis in vitro. Additionally, in vivo experiments were performed using nude mice which were injected with the cancer cells [either the PC-9 (not resistant), PC-9/ER, or the PC-9/ER cells infected with miR-223)]. We found that the tumor volumes were reduced in the rats injected with the cells infected with miR-223. To further explore the underlying mechanisms, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to identify the target molecules of miR-223. miR-223 was demonstrated to act as a local regulator of insulin-like growth factor-1 receptor (IGF-1R) in the acquired resistance to tyrosine kinase inhibitors (TKIs). Notably, the overexpression of IGF-1R in NSCLC was downregulated by miR-223, and the activation of Akt/S6, the downstream pathway, was also inhibited. The inhibition of IGF-1R by miR-223 was attenuated by exogenous IGF-1 expression. Therefore, miR-223 may regulate the acquired resistance of PC-9/ER cells to erlotinib by targeting the IGF-1R/Akt/S6 signaling pathway. The overexpression of miR-223 may partially reverse the acquired resistance to epidermal growth factor receptor-TKIs, thus, providing a potential therapeutic strategy for TKI-resistant NSCLC.