MiR-21 overexpression is associated with acquired resistance of EGFR-TKI in non-small cell lung cancer.

With the increasing use of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) in patients with advanced non-small cell lung cancer (NSCLC), its acquired resistance has become a major clinical problem. Recent studies revealed that miR-21 was involved into the resistance of cytotoxic agents. The aim of this study was to investigate its role in the acquired resistance of NSCLC to EGFR-TKI. EGFR-TKI-sensitive human lung adenocarcinoma cell line PC9 and the acquired resistant cell line, PC9R, were used. Lentiviral vectors were used to infect PC9 or PC9R to regulate the miR-21 expression. The expression of targeted proteins PTEN and PDCD4 was controlled by RNA interference. MicroRNA array, RT-PCR and TaqMan MicroRNA Assays were used to detect miR-21 expression. The MTT and Annexin V assays were used to determine proliferation and apoptosis. Western Blot and immunohistochemistry were used to analyze target protein expression (PTEN, PDCD4, Akt, p-Akt). We also constructed PC9R xenograft tumor model to observe the relationship between miR-21 and EGFR-TKI resistance in vivo and validated it in the clinical serum specimens of NSCLC patients treated with EGFR-TKI. MiR-21 was overexpressed in the EGFR-TKI resistant cell line PC9R relative to PC9. The level of miR-21 was reversely correlated with the expression of PTEN and PDCD4 and positive correlated with PI3K/Akt pathway. Inhibiting miR-21 with lentivirus vector induces apoptosis in PC9R cell line and inhibiting miR-21with ASO suppressed tumor growth in nude mice treated with EGFR-TKI. Furthermore, serum miR-21 expression in NSCLC patients treated with EGFR-TKI was significantly higher at the time of acquiring resistance than at baseline (p<0.01). miR-21 is involved in acquired resistance of EGFR-TKI in NSCLC, which is mediated by down-regulating PTEN and PDCD4 and activating PI3K/Akt pathway.

Li B ，Ren S ，Li X ，Wang Y ，Garfield D ，Zhou S ，Chen X ，Su C ，Chen M ，Kuang P ，Gao G ，He Y ，Fan L ，Fei K ，Zhou C ，Schmit-Bindert G ... -  《-》

Notch-1 contributes to epidermal growth factor receptor tyrosine kinase inhibitor acquired resistance in non-small cell lung cancer in vitro and in vivo.

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) occurs in non-small cell lung cancer (NSCLC) patients who initially respond to TKI treatment but whose cancer then progresses. Recent studies have shown that Notch signal is associated with drug resistance. However, the exact mechanism of Notch during acquisition of resistance to EGFR-TKI in human lung cancer remains unclear. In the present study, we showed that the expression of Notch-1 was highly upregulated in EGFR-TKI acquired resistant lung cancer cells. More importantly, Notch-1 contributed to the acquisition of the epithelial-mesenchymal transition (EMT) phenotype, which was critically associated with acquired resistance to EGFR-TKI. Silencing of Notch-1 using siRNA resulted in mesenchymal-epithelial transition (MET), which was associated with impaired invasion and anchorage-independent growth of lung cancer and resensitisation to gefitinib in acquired resistant NSCLC cells. Finally, gefitinib treatment of Balb/c nu/nu with acquired resistant lung cancer xenografts in combination with Notch inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-(S)-phenylglycine t-butyl ester (DAPT) resulted in effective tumour growth retardation, with decreased proliferative activity and increased apoptotic activity. Collectively, these data suggest that Notch-1 might play a novel role in acquired resistance to gefitinib, which could be reversed by inhibiting Notch-1.

Xie M ，He CS ，Wei SH ，Zhang L ... -  《-》

The long non-coding RNA, GAS5, enhances gefitinib-induced cell death in innate EGFR tyrosine kinase inhibitor-resistant lung adenocarcinoma cells with wide-type EGFR via downregulation of the IGF-1R expression.

Dong S ，Qu X ，Li W ，Zhong X ，Li P ，Yang S ，Chen X ，Shao M ，Zhang L ... -  《Journal of Hematology & Oncology》

MicroRNA-34a overcomes HGF-mediated gefitinib resistance in EGFR mutant lung cancer cells partly by targeting MET.

Zhou JY ，Chen X ，Zhao J ，Bao Z ，Chen X ，Zhang P ，Liu ZF ，Zhou JY ... -  《-》

Antitumor activity of combination treatment with gefitinib and docetaxel in EGFR-TKI-sensitive, primary resistant and acquired resistant human non-small cell lung cancer cells.

Wu M ，Yuan Y ，Pan YY ，Zhang Y ... -  《-》