MicroRNAs (miRNAs) are involved in the epithelial-mesenchymal transition (EMT) process and are associated with metastasis in gastric cancer (GC). MiR-338-3p has been reported to be aberrantly expressed in GC. In the present study, we show that miR-338-3p inhibited the migration and invasion of GC cells in vitro. Knocking down miR-338-3p in GC cells led to mesenchymal-like changes. MiR-338-3p influenced the expression of the EMT-associated proteins by upregulating the epithelial marker E-cadherin and downregulating the mesenchymal markers, N-cadherin, fibronectin, and vimentin. In terms of mechanism, miR-338-3p directly targeted zinc finger E-box-binding protein 2 (ZEB2) and metastasis-associated in colon cancer-1 (MACC1). MiR-338-3p repressed the Met/Akt pathway after MACC1 inhibition. Reintroduction of ZEB2 and MACC1 reversed miR-338-3p-induced EMT suppression. Consistently, inverse correlations were also observed between the expression of miR-338-3p and ZEB2 or MACC1 in human GC tissue samples. In conclusion, miR-338-3p inhibited the EMT progression in GC cells by targeting ZEB2 and MACC1/Met/Akt signaling.

Cancer cells mainly metabolize by glycolysis (the Warburg effect) and are better adapted to resist metabolic stress. Metastasis-associated in colon cancer-1 (MACC1) is an oncogene promoting gastric cancer (GC) growth and metastasis, and its expression positively correlates with GC progression. However, it is unknown why MACC1 elevates with GC progression and what is its role in cancer metabolism. In this study, we discovered that MACC1 expression was significantly upregulated via adenosine monophosphate-activated protein kinase signaling in response to glucose deprivation-induced metabolic stress. Clinical observation demonstrates that MACC1 expression was higher in advanced stage GC. MACC1 expression was proved to be positively correlated with the maximum standardized uptake value of (18)F-deoxyglucose in the patients, and MACC1 enhanced (18)F-deoxyglucose uptake in GC cells and the xenografts. The underlying mechanism was that MACC1 promoted the Warburg effect by upregulating the activities and expressions of a series of glycolytic enzymes, including hexokinase, pyruvate dehydrogenase kinase and lactate dehydrogenase, in GC cells. This metabolic shift enhanced cell viability and resistance to apoptosis by facilitating ATP generation, reducing the reactive oxygen species production and stabilizing the mitochondrial membrane potential. In contrast, MACC1-silenced or the Warburg effect-blocked GC cells were more vulnerable to metabolic stress. In conclusion, metabolic stress is one of the mechanisms that elevate MACC1 expression in GC, and MACC1 upregulation compensatively ensures GC growth against metabolic stress by facilitating the Warburg effect.

No abstract