Abstract LB-169: Ovarian cancer cells selectively release exosomes containing tumor suppressor miRNAs to maintain SRC-mediated oncogenic activities

Abstract

Abstract Exosomes have emerged as an important mediator of diverse biological functions including tumor cell progression, invasion, immune escape, and cell-to-cell communication, through the release of molecules such as mRNAs, microRNAs, and proteins. Ovarian cancer (OC) is one of the lethal cancers with extensive local invasion, metastasis, and poor diagnosis. Thus, finding novel targets for OC therapy are urgently needed. Here, we isolated 30-140 nm exosomes from the supernatant of one normal and six different OC cells. In addition, RNAs were isolated from cells and exosomes, and profiles of two miRNA fractions were obtained using affymetrix microarray analysis. By comparing signal intensities of microarray data and validation using RT-PCR analysis, we found that miR-940 was abundant in exosomes from SKOV3IP1, HeyA8, and HeyA8-MDR. Ectopic expression of miR-940 inhibited proliferation, colony formation, invasion, migration, induced G0/G1 cell cycle arrest, and apoptosis in OC. Overexpression of miR-940 also inhibited tumor cell growth in vivo. The target gene of miRNA-940 and the downstream pathway were further investigated using several target prediction algorithms. We identified specific targeting sites for miR-940 in the 3’-untranslated region (3’-UTR) of SRC. We then experimentally validated miR-940 as a direct regulator of SRC using cell transfection and luciferase assays, and showed that miR-940 inhibited SRC expression at mRNA and protein levels. Following this reduction, the activity of proteins downstream of SRC, such as FAK, paxillin and Akt were also reduced. Collectively, our results suggest that OC cells selectively secreted the tumor suppressive miR-940 into the extracellular environment via exosomes, to maintain their invasiveness and tumorigenic phenotype. Citation Format: Mohammed H. Rashed, Pinar Kanlikilicer, Cristian Rodriguez Aguayo, Nashwa N. Kabil, Martin Pichler, Recep Bayraktar, Emine Bayraktar, Cristina Ivan, Rahul Mitra, George A. Calin, Anil K. Sood, Mohamed F. Abd-Ellah, Gouda K. Helal, Gabriel Lopez Berestein. Ovarian cancer cells selectively release exosomes containing tumor suppressor miRNAs to maintain SRC-mediated oncogenic activities. [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 LB-169.