APE1 shRNA‐loaded cancer stem cell‐derived extracellular vesicles reverse Erlotinib resistance in non‐small cell lung cancer via the IL‐6/STAT3 signalling

OBJECTIVE: Apurinic endonuclease 1 (APE1) has been suggested as an oncogene of lung tumours and our bioinformatics analysis identified the association between Erlotinib resistance and interleukin‐6 (IL‐6). Thus, we performed this work to delineate the mechanistic actions of APE1/IL‐6 signalling in Erlotinib resistance of non‐small cell lung cancer (NSCLC). METHODS: We selected human NSCLC cell lines HCC827 and PC9 to establish Erlotinib‐resistant HCC827R and PC9R cells. Cancer stem cells (CSCs) were isolated from Erlotinib‐sensitive HCC827P and PC9P cells (PCSCs) and from HCC827R and PC9R cells (RCSCs). Further, extracellular vesicles (EVs) were separated from PCSCs (PCSC‐EVs) and RCSCs (RCSC‐EVs) and co‐cultured with RCSCs with or without short hairpin RNA (shRNA)‐targeting APE1 (APE1 shRNA) transduction. In addition, functional assays were conducted to determine the effect of APE1 shRNA on malignant phenotypes of cancer cells in vitro and in vivo and the activation of IL‐6/STAT3 signalling. RESULTS: It was found that NSCLC cells could internalize both RCSC‐EVs and PCSC‐EVs. RCSC‐EVs augmented the resistance of NSCLC cells to Erlotinib. The overexpression of APE1 occurred in NSCLC tissues, and IL‐6 was enriched in serum samples of patients with NSCLC. APE1 shRNA was demonstrated to restrict the Erlotinib resistance of NSCLC cells by inactivating the IL‐6/STAT3 signalling. Additionally, shAPE1‐loaded RCSC‐EVs suppressed the Erlotinib resistance of NSCLC via the IL‐6/STAT3 axis both in vitro and in vivo, as reflected by impeded malignant phenotypes and xenograft tumour formation. CONCLUSIONS: Collectively, these data indicate that APE1 confers Erlotinib resistance by activating the IL‐6/STAT3 signalling, suggesting targeting APE1 as a possible therapeutic target in Erlotinib‐resistant NSCLC.