Epigenetic silencing of miR-483-3p promotes acquired gefitinib resistance in EGFR-mutant NSCLC by targeting integrin beta3

[Speaker] Lu Xu:1
[Co-author] Jinnan Yue:1, Dacheng Lv:1, Caiyun Wang:1, Hongzhuan Chen:1
1:Shanghai Jiao Tong University School of Medicine, China

Background: All patients with EGFR mutant lung cancers eventually develop acquired resistance to EGFR tyrosine kinase inhibitors (TKI). In up to 30% of patients, the mechanism of acquired resistance remains unknown. MicroRNAs (miRNAs) represent a category of small non-coding RNAs commonly dysregulated in human malignancies and have been implicated in therapy resistance. The aim of this study was to understand the role of novel miRNAs in acquired EGFR TKI resistance in EGFR-mutant NSCLC.
Method: The miR-483-3p expression in in vitro and in vivo models of acquired gefitinib resistance was examined by miRNA microarray and real-time RT-PCR. Transient or stable gain- and loss-of-function experiments were conducted in cell lines and nude mice, to evaluate the effects of miR-483-3p on sensitivity to gefitinib, proliferation, apoptosis, EMT and migration/invasion in vitro and in vivo. The molecular pathways affected by miR-483-3p were characterized using in silico target prediction, dual luciferase reporter assays and overexpression rescue experiments. The role of promoter methylation in miR-483-3p silencing was examined by real-time RT-PCR after demethylating agents treatment.
Result: In this study, we reported the silencing of miR-483-3p and evidence for epithelial-to-mesenchymal transition (EMT) in both in vitro and in vivo EGFR-mutant lung cancer models with acquired resistance to gefitinib. In those tumor models, forced expression of miR-483-3p effectively increased sensitivity of gefitinib-resistant lung cancer cells to gefitinib by inhibiting proliferation, promoting apoptosis and reversing EMT phenotype. Mechanistically, miR-483-3p directly targeted integrin beta3, and thus repressed downstream FAK/Erk signaling pathway. In addition, miR-483-3p silencing in gefitinib-resistant NSCLC was due to hypermethylation of its own promoter.
Conclusion: Our study provides a novel mechanism that epigenetic silencing of miR-483-3p promotes acquired EGFR TKI resistance in EGFR-mutant NSCLC by targeting integrin beta3. miR-483-3p may present a promising therapeutic target to overcome acquired resistance.
The work was supported by National Natural Science Foundation of China (81372522 and 81773747), Science and Technology Commission of Shanghai Municipality (12ZR1416000 and 12140901400).

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