The evolutionary properties of organisms lead to the issue of targeted drug resistance. Numerous clinical trials have shown that tumor-associated macrophages (TAMs) in patients with lung cancer adversely affect the clinical efficacy of epithelial growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). However, the mechanism by which TAMs influence the tumor cell response to TKIs remains unclear. The aim of the present study was to investigate the influence of TAM-derived exosomes on the sensitivity of PC9 and HCC827 lung adenocarcinoma cells to the EGFR inhibitor gefitinib. Multiple cytokines were used to induce the differentiation of THP-1 human leukemia monocytes into macrophages in vitro. The obtained cells were identified as TAMs by cytomorphology and flow cytometry. Exosomes were extracted from the TAM culture supernatants and identified using electron microscopy and nanoparticle tracking analysis. Flow cytometry was used to examine the apoptosis of lung adenocarcinoma cells when treated with gefitinib and/or TAM-derived exosomes. In addition, western blotting was used to detect the expression of the key proteins of the AKT, ERK1/2 and STAT3 signaling pathways. TAM-derived exosomes were successfully obtained. The TAM-derived exosomes were shown to affect the proliferation and apoptosis of lung adenocarcinoma cells. Furthermore, the killing effect of gefitinib on the tumor cells was attenuated. The mechanism underlying the effects of the TAM-derived exosomes may be associated with reactivation of the AKT, ERK1/2 and STAT3 signaling pathways. In conclusion, the findings indicate that TAM-derived exosomes promote resistance to gefitinib in non-small cell lung cancer (NSCLC), and the mechanism may be associated with reactivation of the AKT, ERK1/2 and STAT3 signaling pathways. This study may serve as a reference in the exploration of alternative strategies for NSCLC following the development of resistance to EGFR-targeted drugs.

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Background Non‐small cell lung cancer (NSCLC) is one of the cancers with a high mortality rate. CircRNAs have emerged as an important regulatory factor in tumorigenesis in recent years. However, the detailed regulatory mechanism of a circular RNA cullin 2 (hsa_circ_0018189; hsa_circ_0018189) is still unclear in NSCLC. Methods RNA levels of hsa_circ_0018189, microRNA (miR)‐656–3p, and Solute carrier family seven member 11 (SLC7A11, xCT) were analyzed by real‐time quantitative reverse transcription‐polymerase chain reaction (RT‐qPCR), and protein level was assessed by Western blot and immunohistochemical assay. Enzyme‐linked immunosorbent assay was conducted to detect cell glutamine metabolism. Effects of hsa_circ_0018189 on cell proliferation, apoptosis, migration, and invasion were analyzed by corresponding assays. Luciferase reporter assay and RNA‐immunoprecipitation assay confirmed the target relationship between miR‐656‐3p and hsa_circ_0018189 or xCT. The in vivo function of hsa_circ_0018189 was verified by xenograft mouse models. Results Hsa_circ_0018189 abundance was overexpressed in NSCLC cells and samples. Deficiency of hsa_circ_0018189 lowered NSCLC cell proliferative, migrating, invading, and glutamine metabolism capacities, and hsa_circ_0018189 silencing inhibited the growth of tumors in vivo. Hsa_circ_0018189 could up‐regulate xCT by sponging miR‐656‐3p. And miR‐656‐3p downregulation or xCT overexpression partly overturned hsa_circ_0018189 knockdown or miR‐656‐3p mimic‐mediated repression of NSCLC cell malignancy. Conclusion Hsa_circ_0018189 drove NSCLC growth by interacting with miR‐656‐3p and upregulating xCT.

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