br Conflict of interest br Acknowledgment This

Conflict of interest
Acknowledgment This work was supported by National Program on Key Basic Research Project of China (No. 2013CB127305); The National Natural Science Foundation of China (No. 314020785); Hubei Provincial Creative Team Project of Agricultural Science and Technology (No. 2007-620); Hubei Provincial Natural Science Foundation (No. 2013CFA010); The Key Technology Research and Development Program of Hubei Province (No. 2014ABB014, No. 2014ABC012).
Introduction Free fatty acids (FFAs) are dietary nutrients and essential energy sources. Fatty acids are classified by the length of carbon chains. Short-chain fatty acids have fewer than 6 carbons, medium-chain fatty acids have 6 to 12 carbons and long-chain fatty acids contain more than 12 carbons [1], [2], [3]. FFAs act as extracellular signaling molecules through binding to FFA receptors (FFARs), which belong to a family of G-protein-coupled transmembrane receptors [3], [4], [5]. Among FFARs, GPR120 and GPR40 are functionally activated by long- and medium-chain FFAs [3], [4], [5]. However, the distribution and biological response of GPR120 and GPR40 are not uniform. High expression of GPR120 is found in gastrointestinal tract, lung, adipocytes and macrophages, suggesting that GPR120 is involved in the regulation of metabolism and immune response [4], [6], [7]. On the other hand, pancreatic beta Sulforaphane highly expressed GPR40 in pancreatic tissues, suggesting that GPR40 stimulates insulin secretion [8]. Moreover, GPR40 expression was highly detected in insulinoma cells, but not in glucagonoma cells [9]. In colorectal carcinoma cells, activated GPR120 increased cell motile activity and angiogenesis process [10]. Recently, we showed that GPR120 enhanced and GPR40 suppressed cell motile activity of liver epithelial cells treated with chemical agents [11], [12]. In the present study, we investigated the roles of GPR120 and GPR40 in cellular functions of pancreatic cancer cells. HPD1NR and HPD2NR cells used in this study were established from hamster pancreatic duct adenocarcinomas [13]. In addition, GPR120 and GPR40 knockdown cells were generated from human pancreatic PANC-1 cells.
Materials and methods
Results and discussion Recently, we indicated that cell motility was regulated by the different induction of GPR120 and GPR40 in liver epithelial WB-F344 cells treated with chemical agents. The cell motility of WB-F344 cells was stimulated by phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) which is a potent tumor promoting agent, correlating with the induction of GPR120 [11]. In contrast, cell motility of WB-F344 cells was suppressed by GPR40 induced by ethionine which is a potent liver carcinogen [12]. These findings suggest that GPR120 acts as a positive regulator and GPR40 as a negative regulator of the cell motility of WB-F344 cells. In the present study, we investigated the effects of GPR120 and GPR40 on cellular functions of three pancreatic cancer cell lines. The expression patterns of GPR120 and GPR40 genes by semi-quantitative RT-PCR analysis are shown in Fig. 1A. HPD1NR cells expressed Gpr40 but did not express Gpr120. While Gpr120 was expressed in HPD2NR cells, Gpr40 expression was undetectable. On the other hand, GPR40 and GPR120 expressions were detected in PANC-1 cells. Based on these findings, to evaluate effects of GPR120 and GPR40 on cell motility of pancreatic cancer cells, cells were pretreated with GW9508 (10 μM) which is an agonist of GPR120 and GPR40 [16], [17], [18]. The cell motile activity of HPD1NR cells were suppressed by GW9508, while GW9508 stimulated the cell motile activity of HPD2NR cells (Fig. 1B). Since PANC-1 cells expressed GPR120 and GPR40 genes, cells were treated with GW1100, a GPR40 antagonist, before cell motility assay [16], [17], [18]. The cell motility of PANC-1 cells was inhibited by GW9508. In contrast, the cell motile activity of PANC-1 cells was markedly enhanced by pretreatment of GW9508 and GW1100 (Fig. 1C). Therefore, these results demonstrated that GPR120 enhanced and GPR40 inhibited the cell motility of pancreatic cancer cells, similar as observed with WB-F344 cells.