Downregulation of miR-506-3p Facilitates EGFR-TKI Resistance through Induction of Sonic Hedgehog Signaling in Non-Small-Cell Lung Cancer Cell Lines

Non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation eventually develop resistance to EGFR-targeted tyrosine kinase inhibitors (TKIs). Treatment resistance remains the primary obstacle to the successful treatment of NSCLC. Although drug resistance mechanisms have been studied extensively in NSCLC, the regulation of these mechanisms has not been completely understood. Recently, increasing numbers of microRNAs (miRNAs) are implicated in EGFR-TKI resistance, indicating that miRNAs may serve as novel targets and may hold promise as predictive biomarkers for anti-EGFR therapy. MicroRNA-506 (miR-506) has been identified as a tumor suppressor in many cancers, including lung cancer; however, the role of miR-506 in lung cancer chemoresistance has not yet been addressed. Here we report that miR-506-3p expression was markedly reduced in erlotinib-resistant (ER) cells. We identified Sonic Hedgehog (SHH) as a novel target of miR-506-3p, aberrantly activated in ER cells. The ectopic overexpression of miR-506-3p in ER cells downregulates SHH signaling, increases E-cadherin expression, and inhibits the expression of vimentin, thus counteracting the epithelial-mesenchymal transition (EMT)-mediated chemoresistance. Our results advanced our understanding of the molecular mechanisms underlying EGFR-TKI resistance and indicated that the miR-506/SHH axis might represent a novel therapeutic target for future EGFR mutated lung cancer treatment.

Abstract 485: Modulation of microRNA expression in EGFR-tyrosine kinase inhibitor-resistant non-small cell lung cancer cell lines

Objectives: Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are now standard of care in lung cancer patients with EGFR mutation. Invariably, these patients develop resistance and require treatment with another EGFR-TKI or chemotherapy. The gatekeeper mutation T790M is responsible for about 50% of resistance. Other mechanisms may also confer resistance in these patients. High expression of microRNA-10b (miRNA-10b) is associated with worse prognosis in resected lung cancer patients with EGFR mutation. Both miRNA-27a and -27b are associated with increased expression of c-met, which is a potential mechanism of resistance to EGFR-TKI. The goal of this study is to determine the optimal treatment and miRNA characteristic of EGFR mutation lung cancer cells resistant to EGFR-TKI. We hypothesized that miRNA-10b, -27a and -27b modulated Erlotinib (ERL) resistance by different EGFR-TKIs and chemotherapeutic agents in EGFR mutant NSCLC cell lines.

Materials and Methods: Lung cancer cell lines with EGFR mutation HCC827 and HCC4006 resistant to ERL were generated. ERL-resistant cells were then treated with 10 nM afatinib (Afa), 0.5 mg/mL pemetrexed (Pem), and combination of 10 nM Afa/0.5mg/mL Pem for 72h. The cells were harvested and microRNA assay was performed by real-time PCR. NCI-H460 cell line without EGFR mutation was used as control.

Results: We observed increased expression of miRNA-10b, miRNA-27a and miRNA-27b in ERL-resistant HCC4006 compared to control cells NCI-H460. There was an upregulation of miRNA-27a and -27b but not of miRNA-10b in ERL-resistant HCC827. Treatment of ERL-resistant cells with Afa, Pem, and combined treatment changed the expression of miRNA-10b, miRNA-27a and miRNA-27b. These miRNAs were downregulated by 2nd-generation EGFR-TKI therapy alone or in combination with Pem. Different treatments had different effects on these miRNAs. There might be differences in miRNA regulation in different cell lines when treated with EGFR-TKI or chemotherapy. Our results suggest that microRNA may be used as targets for developing novel approach to treating patients with EGFR-TKI resistance.

Conclusion: This study may have implications in the management of patients resistant to EGFR TKI. MicroRNA analysis showed upregulation of several microRNAs that should be confirmed in clinical setting.

Citation Format: Inamul Haque, Hannah Motes, Mukut Sharma, Emma Borrego-Diaz Reyes, Andrew K. Godwin, Chao H. Huang. Modulation of microRNA expression in EGFR-tyrosine kinase inhibitor-resistant non-small cell lung cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 485.

Abstract 2430: Treatment sequence and molecular biomarker in EGFR mutant lung cancer cells

Introduction

Lung cancer is the leading cause of cancer related death in the US. A subset of patients with lung cancer has a mutation in the Epidermal Growth Factor Receptor (EGFR) which makes them extremely responsive to EGFR tyrosine kinase inhibitor (TKI) erlotinib. The emergence of EGFR TKI resistance is new challenge in the management of these patients. We conducted a study to determine the best treatment sequence after resistance to EGFR TKI, testing the use of chemotherapy Pemetrexed (P), Afatinib (A), Rociletinib (R) and the combination of these agents in lung cancer cell lines with EGFR mutation that were pretreated with erlotinib.

Material and methods

Lung cancer cell lines with EGFR mutation CRL-2868 (E746 - A750 deletion) and CRL-2871 (L747 - E749 deletion, A750P) mutation were treated with 5 nM erlotinib for 24h and 72 h.

The erlotinib resistance cells were then treated with 10nM of A or 10nM of P, or 21.5 nM of R, or the combination AP or the combination of RP. As control, we used lung cancer HTB-177 which does not have EGFR mutation. MTT proliferation assay was performed after 24, 48, 72 and 144h after the treatment. microRNA profiling was done by real time PCR in all cells after erlotinib treatment to find potential biomarkers as hallmark of erlotinib resistance cells.

Results

Rociletinib induced the maximum inhibition of cell proliferation at 144h in both cell lines with EGFR mutation. The RP also induced decreased cell proliferation in both cell lines with EGFR mutation. RP combination was more effective then R alone in CRL 2871. The use of A alone, P alone or AP combination was not different in CRL2871 but P had antagonistic effect when combined with A or R in CRL 2868. microRNA 10b, 27a and 27b were upregulated in the erlotinib resistant cells.

Conclusion.

EGFR resistance arises after treatment with erlotinib in lung cancer cell lines with EGFR mutation. Treatment with R and the combination of RP induced greater inhibition of proliferation compared to A, P alone. The combination of AP was antagonistic. This may have implications in the management of patients resistant to EGFR TKI. microRNA analysis showed up-regulation of several microRNA that should be tested in clinical setting.

Citation Format: Hannah Motes, Emma Borrego-Diaz Reyes, Jared Kevern, Chao H. Huang, Peter J. Van Veldhuizen. Treatment sequence and molecular biomarker in EGFR mutant lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2430. doi:10.1158/1538-7445.AM2015-2430