Abstract 4814: miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and next generation EGFR tyrosine kinase inhibitors (TKIs) in NSCLC
Authors: Zhao Jane , Guerrero Adriana , Kelnar Kevin , Peltier Heidi J. , Bader Andreas G. 
Published: July 2016

Background: miRNAs play a critical role in regulating key biological processes by modulating the expression of up to several hundred genes across multiple cellular pathways. miR-34a, one of the most widely studied miRNAs, is lost or expressed at reduced levels in many tumors, and normally functions as a natural tumor suppressor by down-regulating expression of &gt;30 different oncogenes, as well as genes involved in tumor immune evasion, including PD-L1. MRX34 is a potential first-in-class liposome-encapsulated miR-34a mimic in Phase 1 study (NCT01829971) as monotherapy in patients with advanced malignancies. The ability of miR-34a to regulate the expression of key oncogenes across multiple oncogenic pathways makes MRX34 a rational candidate to combine with other anticancer therapies which are frequently subject to primary and acquired resistance in the clinic. Previous studies showed that miR-34a greatly sensitizes both EGFR wild-type and mutant NSCLC cell lines, as well as hepatocellular carcinoma cell lines, to the first generation EGFR TKI erlotinib. Here we report research combining miR-34a and the next generation EGFR TKIs afatinib (Gilotrif®) and rociletinib (CO-1686) in NSCLC cell lines.

Methods: Combination studies using single-drug ratios (∼IC50 ratio of miR-34a and TKI) and multiple ratios above and below were performed in a panel of EGFR wild-type (A549, H460, H1299, H226) and EGFR mutant (H1975, HCC827 parent and HCC827 erl res) NSCLC cell lines. Cells were transfected with miR-34a and incubated 24 hrs later with afatinib or rociletinib for 72 hrs, with cellular proliferation then determined by AlamarBlue. Synergistic, additive, or antagonistic effects were determined by combination index (CI) values (based on Loewe's concept of additivity), isobolograms, and curve-shift analyses.

Results: Strong synergy was observed between miR-34a and both TKIs in all EGFR-mutant cell lines tested (CI &lt;0.5 at effect levels ≥50%). Synergy was also observed for miR-34a + rociletinib in most EGFR wild-type cell lines (CI &lt;0.6 at effect levels of ∼50-80%), but not for miR-34a + afatinib. Best synergies overall were observed in EGFR-mutant cells with acquired erlotinib resistance. The effects were observed across a range of different dose levels and drug ratios, with maximal synergy providing a high level of inhibition (80%) at doses likely achievable in the clinic and well below those projected to be required for similar inhibition by the single agents alone.

Conclusions: Complementing previous results with miR-34a + erlotinib, the data demonstrate strongly synergistic anticancer effects between miR-34a and next generation EGFR TKIs in combination against a range of EGFR wild-type and mutant NSCLC cell lines. The results support clinical study of MRX34 + EGFR TKI combinations in patients with advanced NSCLC, including those with EGFR-mutant NSCLC that has progressed on EGFR TKI monotherapy.

Citation Format: Jane Zhao, Adriana Guerrero, Kevin Kelnar, Heidi J. Peltier, Andreas G. Bader. miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and next generation EGFR tyrosine kinase inhibitors (TKIs) in NSCLC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4814.