Abstract 1448: Disseminated tumor cell formation promoted by lysophosphatidic acid (LPA) involves ZEB1/miR21-dependent activation pathway
Authors: Sahay Debashish , Leblanc Raphaël , Ribeiro Johnny , Clézardin Philippe , Peyruchaud Olivier 
Published: May 2015

Abstract
Lysophosphatidic acid (LPA) is a natural bioactive lipid that promotes metastasis of many types cancer cells. We have shown that blocking LPA receptor type 1 (LPA1) activity inhibits early stage of bone metastasis by inhibiting motility and invasion of breast cancer cells. However, the signaling pathways and gene activation involved in this process have not been well characterized. Micro-ARNs (miR) are well known master regulators of gene expression. Based on the complete miR expression profile in human MDA-MB-231 breast cells stimulated by LPA, we found that miR-21 was one of the most up regulated miR. Using the Taqman RT-QPCR system, we found that LPA induced a rapid increase in miR-21 expression in MDA-MB-231 cells and in their highly osteotropic sub-clone MDA-B02 cells reaching a plateau by two to three folds (EC50 = 0.1μM) after 45 min of stimulation. MiR-21 is well known to act as an oncomiR promoting metastasis in multiple cancers. Also, it is known that miR-21 expression is controlled by several transcription factors. The full transcriptomic analysis of our breast cancer cell lines showed that among those transcription factors, ZEB1, STAT3 and cFos were up regulated by LPA. Interestingly, silencing ZEB1 expression in these cells using synthetic ZEB1-siRNAs abolished LPA-induced miR-21 expression whereas silencing STAT3 or sFos had no effect. Hence, silencing ZEB1 up-regulated the expression of miR-21 target genes PDCD4, PTEN and SPRY2 in MDA-MB-231 cells stimulated by LPA. RT-QPCR analyses also showed that LPA1 was the most abundant LPA receptor in MDA-MB-231 cells (LPA1&gt;LPA2&gt;&gt;LPA6=LPA7&gt;LPA5) whereas LPA3 and LPA4 were not detectable. We found that the treatment of our breast cancer cells with Ki16425, a LPA1/LPA3 antagonist, inhibited LPA-induced miR-21 expression. Silencing LPA1 expression in these cells using synthetic LPA1-siRNAs also abolished LPA-induced miR-21 expression. We showed in animal that Debio0719, another LPA1/LPA3 antagonist, inhibits implantation of disseminated tumor cells (DTC) into the bone marrow. Here, we found that the pretreatment of MDA-B02 cells with a specific blocker of miR-21 (mirVana miR-21 inhibitor) before injection of these cells in BALB/c nude mice decreased the incidence of DTC-positive animals and decreased the number DTCs at the metastatic sites. All together our results demonstrate that miR-21 controls the prometastatic activity of LPA involving LPA1-dependent activation of ZEB1 in breast cancer cells.
Citation Format: Debashish Sahay, Raphaël Leblanc, Johnny Ribeiro, Philippe Clézardin, Olivier Peyruchaud. Disseminated tumor cell formation promoted by lysophosphatidic acid (LPA) involves ZEB1/miR21-dependent activation pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1448. doi:10.1158/1538-7445.AM2014-1448