CircRBM33 promotes migration, invasion and mediates osimertinib resistance in non-small cell lung cancer cell line

BACKGROUND: It has been shown that circular RNAs (circRNAs) are involved in the pathogenesis of non-small cell lung cancer (NSCLC). However, the molecular mechanisms of circRNAs in tumor malignant progression and tyrosine kinase inhibitors (TKI) resistance remain undefined. Hereby, we explored the mechanisms by which circRBM33 promotes NSCLC progression and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) resistance. METHODS: Transcriptome sequencing (RNA-seq) was carried out to obtain the circRBM33 we investigated. Quantitative reverse transcriptase-polymerase chain reaction was performed to detect the expression of circRBM33. Cell counting kit-8 assay was performed to detect cell proliferation as well as flow cytometry to detect cell cycle and apoptosis. Transwell assay was performed to detect cell migration and invasion. In vivo tumourigenesis assays were performed to further validate the function of circRBM33. The transcriptome was sequenced after RNA-pulldown and knockdown of cirRBM33 to identify the proteins bound by cirRBM33 and the downstream mechanisms involved in the regulation of cirRBM33. RESULTS: The sequencing results revealed that cirRBM33 was highly expressed in the cell line of osimertinib resistant H1975. In vitro functional validation demonstrated that knockdown of circRBM33 inhibited H1975 proliferation, migration and invasion, changed cell cycle and promoted apoptosis. In vivo, knockdown of circRBM33 inhibited tumour growth. Mass spectrometry results and sequencing analysis of knockdown circRBM33 suggest that circRBM33 may mediate resistance to osimertinib in H1975-OR cells through regulate the DNMT1/interleukin-6 (IL-6) axis. CONCLUSIONS: CircRBM33 is upregulated in NSCLC and that knockdown of circRBM33 inhibits the progression of NSCLC. CircRBM33 may combine with DNMT1, and regulate the resistance of H1975 osimertinib-resistant cells to osimertinib that mediated by IL6. CircRBM33 is a promising diagnostic and prognostic marker to provide effective treatment strategies for NSCLC patients.