Epithelial-mesenchymal transition (EMT) plays an important role in metastasis of gastric cancer. Our previous study showed that Gastrokine-2 (GKN2) can inhibit the metastasis of SGC-7901 and AGS cells. Herein, we further explored the role of GKN2 in epithelial mesenchymal transition of gastric cancer cells and the underlying mechanisms. We found that overexpression of GKN2 can lower the protein expression level of Snail and markedly elevate E-cadherin protein level in SGC7901 and AGS cells. Further data showed that knockdown of snail can inhibit the migration and invasion of SGC-7901 and AGS cells. It is known that Snail can be phosphorylated by GSK3β, a downstream protein of PI3K/AKT pathway. We then test protein expression of p-GSK3β(Ser-9), the downstream protein of PI3K/AKT, which was significantly decreased under the circumstance of GKN2 overexpression. Moreover, LY294002, a PI3K inhibitor, can reverse the protein expression change of E-cadherin and snail induced by siGKN2. Taken together, these findings suggested that GKN2 suppressed epithelial mesenchymal transition of gastric cancer cells by downregulation of snail through PI3K/AKT/GSK3β signaling pathway.

Abstract. 3'3-Diindolylmethane (DIM) has been proved to exhibit anticancer properties in many solid tumors. In our previous study, we demonstrated that DIM inhibited SGC7901 cell proliferation by inducing apoptosis and delaying cell cycle progression. Herein, we further explored the anti-tumor effect of DIM on SGC-7901 tumor bearing mice. Tumors were excised, weighed, and tested by western blot and TdT-UTP nick-end labeling (TUNEL) assay. Blood samples were collected for biochemical analysis. The expression levels of AhR and cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) protein were evaluated by western-blot assay. Our data show that with the increase of DIM dose (0, 5, 10, 20 mg/kg/day), AhR protein gradually decreased as CYP1A1 protein increased. The weight of the tumors found in the treated animals was significantly lower than that of the control group (0.845±0.096 vs. 1.275±0.236 g, 0.768±0.161 vs. 1.275±0.236 g, 0.607±0.106 vs. 1.275±0.236 g, P<0.05). TUNEL test showed that DIM induced increased apoptosis in the treatment groups in a dose-dependent manner. Blood tests also indicated that DIM showed no toxic effect on animal weight or liver and kidney function. These results indicated that DIM agent could be a safe and potent drug in therapy of gastric cancer. IntroductionGastric cancer (GCa) is one of the most common types of malignancy, and the third leading cause of cancer-associated mortality worldwide, with 951,000 incident cases and 723,000 mortalities in 2012 (1). The overall 5-year survival rate is low due to high recurrence rates, nodal metastasis and poor responses to chemotherapy (2). Differences in lifestyle, environment and diet may also have a role in the high incidence and mortality associated with GCa (3). The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor involved in cell differentiation and carcinogenesis, including in lung cancer (4), breast cancer (5) and prostate cancer (6). There are currently few studies involving the AhR pathway and GCa (7). Our previous study demonstrated there is significant AhR expression in human GCa cells (8), and determined that the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) could inhibit GCa cell growth (9). Thus, AhR maybe a promising target for GCa therapy. Due to the toxic and carcinogenic effects of TCDD in humans, our previous study had suggested that the selective AhR receptor modulator 3'3-diindolylmethane (DIM) could inhibit SGC-7901 human GCa cell proliferation by delaying cell cycle progression and inducing apoptosis (10). DIM is an acid-catalyzed condensation product of indole-3-carbinol, a constituent of cruciferous vegetables (11). DIM has been identified as an anti-cancer agent involved in various solid malignancies, including ovarian (12), prostate (13), colon (14) and pancreatic cancer (15). The anti-cancer effects of DIM include suppressing cancer cell proliferation (16-18) and promoting cancer cell apoptosis (19-21). There have been few reports to date regarding the effects of DIM on GCa...