Abstract A30: Autotaxin-induced miRNA exportation and associated mechanisms contributing to tumorigenesis and immune modulation

Abstract

Abstract Approximately 30% of tumors from patients with serous ovarian carcinoma show a significant overexpression of the extracellular enzyme, autotaxin. This circulating enzyme is responsible for lipid metabolism, specifically the hydrolysis of a phosphatidylcholine head group from lysophosphatidyl choline (LPC) to yield lysophosphatidic acid (LPA), which is abundantly found in malignant ascites fluid. As a consequence, numerous growth factor-like pathways through LPA receptors (LPARs), which are cell surface G protein-coupled receptors that bind lipid agonists such as LPA, are aberrantly initiated in ovarian cancer cells, and miRNA feedback mechanisms, which normally regulate such signaling, are disregarded. The purpose of our study is to further understand how serous ovarian cancer cells disregard counteracting miRNA feedback mechanisms that could otherwise prevent tumorigenesis and tumor progression. Therefore, we hypothesize that ovarian cancer cells can hijack miRNA feedback mechanisms by exporting miRNA to alter the signaling of surrounding cells in the stroma and tumor microenvironment, allowing the cancer cells to thrive. We further hypothesize that miR-30c-2-3p, the key component of the feedback mechanism that regulates oncogenic transcription mediated by lysophosphatidic acid, is exported packaged in exosomes. From there, it is likely that exosomes containing miR-30c-2-3p are engulfed by other surrounding cells of the immune system, possibly contributing to immune modulation or suppression in ovarian cancer. Our data will present evidence to support this hypothesis. Foremost, we used an in vivo model of disease as one measure of miR-30c-2-3p expression, circulation, and uptake by surrounding cells through comparison of tumor-bearing and non-tumor-bearing transgenic mice with enhanced autotaxin expression. Chiefly, adipocytes vary in their ability to produce autotaxin in vitro, yet these numbers are inconsistent with circulating levels in transgenic mice, suggesting that miR-30c-2-3p is being absorbed by another cell type. Since ovarian cancer is notorious for its multifactorial immune-suppression properties, we investigated the uptake of exosomal miR-30c-2-3p by peripheral blood mononuclear cells (PBMCs), containing monocytes, lymphocytes, and dendritic cells. Coculture of PBMCs and OVCAR-3 cells has demonstrated a significant (p<0.05) increase in extracellular miR-30c-2-3p compared to OVCAR-3 cells alone, suggesting a strong interplay between the immune players and cancer cells. Utilizing OVCAR-3-GFP cells, which stably express palmitoylated GFP on their plasma membrane, in vitro studies can visually observe the transfer of cancer cell-derived exosomes to immune cells, possibly shedding light on an intracellular response related to immune suppression. Further investigation involving the influence of individual immune cell types and cancer cells utilizing OVCAR-3-ATXwt and OVCAR-3-ATXmut cells will also be conducted in search of immune-suppression mechanisms in ovarian cancer. In conclusion, our overall study will provide evidence to show how unappreciated factors like miRNA may play a major role in the molecular mechanisms contributing to tumor progression in serous ovarian cancer. Citation Format: Sudeepti S. Kuppa, Balazs Rada, Mandi M. Murph. Autotaxin-induced miRNA exportation and associated mechanisms contributing to tumorigenesis and immune modulation. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A30.