Abstract PR09: MicroRNA-24 transferred from platelet-derived microparticles to tumor cells in solid tumors targets mt-Nd2 mRNA and modulates mitochondrial function and tumor growth
Authors: Michael James V. , Wurtzel Jeremy G.T. , Mao Guang Fen , Rao A. Koneti , Hoffman Nicholas E. , Madesh Muniswamy , Prado Fabian J. , Nieman Marvin , Rowley Jesse W. , Weyrich Andrew S. , Goldfinger Lawrence E. 
Published: May 2016

Abstract
The purpose of this study was to evaluate transfer of platelet microRNAs to tumor cells in vivo and to characterize the mechanisms and effects. Platelet-derived microparticles (PMPs) are associated with enhancement of metastasis and poor cancer outcomes. Platelet microparticles in circulating blood have recently been shown to be enriched in platelet-derived microRNAs, and to have the ability to transfer platelet microRNAs to vascular cells as well as some tumor cells when co-incubated in vitro. However, tumor vasculature is highly permeable, allowing the possibility of platelet microparticle-tumor cell interaction. We observed PMP infiltration in the vicinity of blood vessels in grade II/III solid tumors derived from human patients, but not in adjacent normal tissue, including colon carcinoma, lung squamous cell carcinoma, prostate adenocarcinoma, and to a lesser extent in hepatocellular carcinoma; however, we did not observe PMPs in breast invasive ductal carcinoma. To obtain mechanistic insight, we used mouse tumor allograft models, and found that platelet microparticles infiltrated solid tumor allografts, attached to tumor cells, and transferred platelet-derived RNA, including microRNAs, to Lewis lung carcinoma (LLC) tumor cells in vivo, and these effects could be recapitulated by PMP co-incubation in vitro. MiR-24 was not detected in untreated LLC cells but was upregulated following PMP exposure, and in LLC cells isolated from resected tumors. We employed a TU-tagging chemical/genetics approach to selectively tag native platelet RNA, which confirmed transfer of tagged, platelet-derived miR-24 to LLC cells in tumor allografts in vivo. We employed a modified microRNA:mRNA ligation scheme to identify RNA targets of platelet-derived miR-24 in tumor cells, which included mt-Nd2, a mitochondrial mRNA that lacks a 3'-UTR typically targeted by microRNAs, and Snora75, a non-coding small nucleolar RNA, thus representing targeting of one non-coding RNA by another. These RNAs were depleted in platelet microparticle-treated cells, resulting in mitochondrial dysfunction and tumor cell growth inhibition, in a miR-24-dependent manner, as these effects of platelet microparticles were rescued with phosphorothioate LNA antagomiR-24. Blockade of miR-24 in tumor cells accelerated tumor growth in vivo. Thus, transfer of platelet microRNAs including miR-24 to tumor cells via microparticles inhibits tumor cell function and tumor progression. However, global depletion of platelet microRNAs by platelet-specific deletion of Dicer1 inhibited tumor angiogenesis, platelet microparticle infiltration, and resulted in delayed allograft tumor growth in mice, indicating a requirement for platelet miRNAs in tumor angiogenesis. These findings add multiple layers to the regulatory roles of platelet-derived microRNAs and platelet microparticles in tumor progression.
Citation Format: James V. Michael, Jeremy G.T. Wurtzel, Guang Fen Mao, A. Koneti Rao, Nicholas E. Hoffman, Muniswamy Madesh, Fabian J. Prado, Marvin Nieman, Jesse W. Rowley, Andrew S. Weyrich, Lawrence E. Goldfinger. MicroRNA-24 transferred from platelet-derived microparticles to tumor cells in solid tumors targets mt-Nd2 mRNA and modulates mitochondrial function and tumor growth. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr PR09.