Abstract 5182: Activity and clinical relevance of autotaxin and lysophosphatidic acid pathways in high-grade serous carcinoma

Abstract

Abstract Lysophosphatidic acid (LPA) is a bioactive phospholipid with mitogenic and growth factor-like activities affecting cell invasion, cancer progression and drug resistance. It is produced mainly by Autotaxin and acts on six G protein-coupled receptors, LPAR1-6. LPA has recently been implicated as a growth factor present in ascites of ovarian cancer patients. However, mitogenic pathways stimulated by LPA via its receptors are still far uncharacterized. Here we show that three LPA receptors are involved in the progression of the malignancy by the activation of both AKT and ERK pathways. We analyzed a set of 155 samples of high grade serous ovarian carcinoma (HGSC) from the three different anatomic sites of the disease. Results show that LPAR2 mRNA was overexpressed in HGSC cells in effusions compared to solid lesions, with opposite findings for LPAR3 and LPAR6 mRNA and ATX protein that was found mainly in exosomes. LPAR3 levels were significantly higher in pre-chemotherapy effusions compared to post-chemotherapy specimens (p=0.025). Higher expression of LPAR1 (p=0.037), LPAR2 (p=0.025) and LPAR5 (p=0.021) was significantly associated with shorter overall survival. Furthermore, we combined 3D (spheroids) and 2D cell culture models with gene editing using the CRISPR/Cas9 method for LPAR2, LPAR3 and LPAR6 and tested the effects of their silencing in vitro using OVCAR3 and ES2 cell lines. The p-ERK/ERK ratio was significantly elevated in LPAR3KO OVCAR3 cells cultured both in 2D and 3D form. Yet, LPAR2KO OVCAR3 cells expressed low levels of p-ERK/ERK in the 3D form, suggesting that LPAR3 inhibits p-ERK activity downstream, while LPAR2 activates it. ES2 LPAR2KO cells expressed elevated levels of p-AKT/AKT ratio in both the 2D and 3D forms. OVCAR3 LPAR6KO had low p-AKT/AKT ratio when cultured in 2D, but high ratio in the 3D form. LPAR KO further inhibited ovarian cancer invasion and motility.Our results demonstrate, for the first time, significant changes in LPARs' mRNA levels and Autotaxin protein levels with changes in anatomic sites of the disease that correlate to clinic-pathological parameters. Our study identifies a specific molecular machinery triggered by LPA and its' receptors that modulate tumor and can serve as therapeutic targets in this malignancy. Citation Format: Hadil Onallah, Claes G Trope, Thea E. Hetland Falkenthal, Ben Davidson, Reuven Reich. Activity and clinical relevance of autotaxin and lysophosphatidic acid pathways in high-grade serous carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5182.