GPAT2 expression regulates arachidonic acid induced apoptosis in the breast adenocarcinoma cell line MDA-MB-231.

MAURO ALDO MONTANARO; FERREMI FIORELLA; CATTANEO, ELIZABETH R.; GONZALEZ BARÓ, MR

Congreso; Gordon Research Conference on Molecular and Cellular Biology of Lipids; 2019

GPAT2 expression regulates arachidonic acid induced apoptosis in the breast adenocarcinoma cell line MDA-MB-231.Arachidonic acid -derived eicosanoids and their downstream pathways have been implicated in cell growth control and apoptotic pathways in breast cancer, promoting malignancy in several types of tumors. Glycerol-3-phosphate acyltransferase 2 (GPAT2) is an acyltransferase that, differing from the other GPAT isoforms, exclusively uses arachidonoyl-CoA as a substrate for glycerolipid synthesis. Because high levels of arachidonic acid induce apoptosis, whereas metabolic pathways that diminish the content of unesterified arachidonic acid may prevent it, we focused our studies on the role of GPAT2 on the regulation of apoptosis in breast cancer. Using RNAi technology, we silenced GPAT2 in breast cancer derived MDA-MB-231 cells, which endogenously express high levels of GPAT2. Previously, we had demonstrated that GPAT2 is expressed in several types of human cancers, and the expression in the MDA-MB-231 cell line contributed to the tumor phenotype. Treating these cell lines for 2 days with 100 µM arachidonic acid decreased the cell proliferation rate and promoted apoptosis in MDA-SH (GPAT2-silenced) cells, compared to the GPAT2-expressing MDA-SCR control cells (TUNEL assay), suggesting that GPAT2 prevents apoptosis in MDA cells by sequestering free arachidonic acid. To understand the relationship between GPAT2 expression and the apoptosis induction triggered by arachidonic acid, we measured the mRNA expression levels of genes that are involved in arachidonic acid utilization and eicosanoid biosynthesis, such as AKR1C3 (encoding prostaglandin F synthase), ALOX5 (encoding arachidonate 5-lipoxygenase) and EPHX2 (encoding epoxide hydrolase 2), and used flow cytometry to study the induction of apoptosis triggered by arachidonic acid. Our results clearly show that GPAT2 silencing induces the expression of other arachidonic acid metabolizing enzymes, link GPAT2 with arachidonic acid induced apoptosis, and provide information about the molecular mechanisms through which GPAT2 might contribute to the control of tumor growth. Funding: Universidad Nacional de La Plata 11/M-202, Agencia Nacional de Promoción Científica y Tecnológica PICT-2014 3214 and PICT-2017 3877, Argentina