MiR-200c in extracellular vesicles as a circulating biomarker of EGFR-TKI response and a mediator of EGFR-TKI sensitivity in heterogeneous NSCLC.

Abstract

e20547 Background: Through intercellular transfer of EV(extracellular vesicles) miRNA, tumor cells can confer drug resistance to each other and contribute to tumor heterogeneity. However, the mechanisms why EGFR-TKI can be effective in heterogeneous NSCLC with low abundances of EGFR mutations remain unknown. The aim of the study is to investigate the significance of EV miRNA in mediating the efficacy of EGFR-TKI in heterogeneous NSCLC and serving as the biomarker of response to EGFR-TKI. Methods: We first evaluate if EVs from EGFR mutant cell (PC9) can affect EGFR-TKI sensitivity of EGFR wild type cell (CL1-5, H1299) in vitro co-culture system and i n vivo. We then identified the differential miRNA panel by comparing EVs from PC9 to those from CL1-5. Finally, we verified if the expressions level of these miRNA are different in blood EVs from patient with good response compared to those with poor response to EGFR-TKI. Results: We first verified that CL1-5 can take up labelled EVs from PC9 under time-lapse microscope and EGFR mutant DNA can be detected in recipient EGFR wild-type cell using digital PCR. We found EVs from PC9 enhanced gefitinib sensitivity of CL1-5. And co-culturing PC9 with CL1-5 enhanced CL1-5 gefitinib sensitivity which was reversed by adding GW4789, the inhibitor of exosome secretion. In subcutaneous CL1-5 animal model, in comparison to treating with gefitinib or PC9 EVs alone, only the combination treatment with gefitinib and PC9 EVs delayed cancer growth. Using small RNA sequencing, we identified a unique miRNA profile allowing discriminating EV from PC9 cells to those from CL1-5; MiRNA 200 family including 200a, 200b, 200c and mir429 were up-regulated significantly in PC9 EV. From Aug 2015 to Sep 2017, sixteen patients with good response (PFS > 12M) or poor response (PFS < 6M) to EGFR-TKI were enrolled and blood were collected for EV miRNA isolation. Ten of these blood samples were qualified for miRNA analysis and mir200a and 200c were found up-regulated in good responder to EGFR-TKI. The transfection of mir200c in CL1-5 cells not only inhibited the oncogenic pathway contributing to EGFR-TKI resistance including Stat3, Akt, EMT and BIM pathway but also enhanced gefitinib sensitivity of CL1-5 cells. Conclusions: Our data suggested mir200c from blood EV serve as a biomarker of response to EGFR-TKI and mir200c may mediate EGFR-TKI sensitivity in heterogenous EGFR mutant NSCLC.