Abstract 4829: miRNA combination therapy: <i>In vitro</i> anticancer synergy between miR-34a mimic and cytotoxic chemotherapy (CT) in NSCLC
Authors: Adriana Guerrero, Jane Zhao, Xiaojie Yu, Alexander Pertsemlidis, Andreas G. Bader
Journal: Cancer Research (2016)

Abstract 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 &amp;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 EGFR tyrosine kinase inhibitor erlotinib. Here we report research combining miR-34a and standard CT drugs in NSCLC cell lines. Methods: Combination studies using single-drug ratios (∼IC50 ratio of miR-34a and CT drug) and multiple ratios above and below were performed in a panel of NSCLC cell lines (A549, H460, H1299, H2073) with varying degrees of intrinsic resistance to CT. Cells were transfected with miR-34a and incubated 24 hrs later with cisplatin, carboplatin, paclitaxel, gemcitabine, or pemetrexed 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: Synergistic interactions were observed between miR-34 and all CT drugs in all NSCLC cell lines tested. Synergy was observed at multiple miR-34a/cytotoxic agent dose ratios and at drug concentrations inducing 50% or greater inhibition (CI &amp;lt;0.6 and dose reduction index &amp;gt;2 at both 50% and 75% effect levels). Stronger synergy was seen in the H2073 cell line which is relatively more resistant to CT. Conclusions: Consistent with other in vitro results with miR-34a-based combinations, the data demonstrate synergistic anticancer effects between miR-34a + CT in a range of NSCLC cell lines with varying degrees of intrinsic resistance to CT. Overall, the data support further exploration of MRX34 in combination with standard anticancer therapies, and we are evaluating the most appropriate combinations for near-term clinical trials. In addition to resistance, other critical oncogenic mechanisms present in the tumor microenvironment (eg, immune evasion, cancer stem cells, metastasis) could potentially also be mitigated to the benefit of patients by a miRNA-based approach to therapy. Citation Format: Adriana Guerrero, Jane Zhao, Xiaojie Yu, Alexander Pertsemlidis, Andreas G. Bader. miRNA combination therapy: In vitro anticancer synergy between miR-34a mimic and cytotoxic chemotherapy (CT) 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 4829.