Abstract 5985: MiR-329 mimic based nano-therapy inhibits growth and progression of triple negative breast cancer
Authors: Kara Goknur , Kahraman Nermin , Denkbas Emir Baki , Calin George , Ozpolat Bulent 
Published: September 2020

Abstract
Triple-negative breast cancer (TNBC) is an incurable disease with the highest mortality rates among all breast cancer subtypes. Currently, there is no FDA-approved targeted therapies for TNBC. Significant genetic heterogeneity with six genetically defined sub-groups is considered the major reason for treatment failures and high mortality rates in TNBC patients and has been the major limitation in the identification of common molecular targets and development of targeted therapies for this cancer. Recently, interest in the development of non-coding miRNA based therapeutics has increased significantly. miRNA molecules are short, non-coding RNAs that have emerged as critical regulators of gene expression, affecting a multitude of biological processes, including cell proliferation, survival, motility, and tumorigenesis, by acting as oncogenes or tumor suppressors. Recently, first in human miRNA-targeted therapeutics were found safe and well tolerated in phase I clinical trials, suggesting that miRNA based therapeutic interventions may provide novel therapeutic options, especially for TNBC patients. However, successful clinical application of miRNA-based therapeutics requires development of safe and effective nano-delivery systems. To identify potential molecular targets we extensively analyzed miRNA databases and recently discovered that miR-329 expression is associated with significantly longer survival in patients with TNBC. More important, we found that miR-329 expression is lost or significantly reduced in the majority of TNBC cell lines. We demonstrated that in vitro expression of miR-329 significantly suppressed cell proliferation, invasion and migration. To identify molecular mechanism of miR-329 based therapy we utilized 5 different target prediction algorithms and identified that miR-329 has a binding site at 3'-UTR of EF2K gene which encodes Eukaryotic Elongation factor-2 kinase (EF2K). We found that EF2K is significantly upregulated in TNBC patients and is associated with shorter overall survival in TNBC patients. Remarkably, silencing of EF2K by siRNA recapitulated the effects of ectopic expression of miR-329 mimic and successfully suppressed growth and invasion of various TNBC cells. Furthermore, in vivo therapeutic delivery of miR-329 mimic incorporated albumin-based nanoparticles led to significant tumor suppressive effects in multiple TNBC xenograft models (MDA-MB-231 and MDA-MB-436) in mice. Importantly, albumin-based miR-329 nano-therapy in mice did not lead to any detectable side effects during the therapy, suggesting that miR-329 based therapy is safe and clinically feasible approach. Currently, we are conducting luciferase-based gene reporter assay to demonstrate that miR-329 specifically binds to 3'-UTR of EF2K mRNA and inhibits EF2K expression. We are also analyzing the tumors collected after albumin based nanoparticles-miR-329 treatment for miR-329 expression and EF2K downregulation as well as intra-tumoral proliferation markers (Ki67) and apoptosis by TUNEL. Based on clinical significance and our preliminary data, we conclude that miR-329 acts as a tumor suppressor in TNBC, and its reduced expression leads to expression of EF2K signaling. In addition, miR-329-based nano-therapy provides a safe and significant anti-tumor efficacy and may be a potential therapy for TNBC.
Citation Format: Goknur Kara, Nermin Kahraman, Emir Baki Denkbas, George Calin, Bulent Ozpolat. MiR-329 mimic based nano-therapy inhibits growth and progression of triple negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5985.