Metformin inhibits gastric cancer cells metastatic traits through suppression of epithelial-mesenchymal transition in a glucose-independent manner.

Epithelial-mesenchymal transition (EMT), which is mainly recognized by upregulation of mesenchymal markers and movement of cells, is a critical stage occurred during embryo development and spreading cancerous cells. Metformin is an antidiabetic drug used in treatment of type 2 diabetes. EMT inhibitory effect of metformin has been studied in several cancers; however, it remains unknown in gastric cancer. The aim of the present study was to investigate the metformin effects on inhibition of EMT-related genes as well as migration and invasion of AGS gastric cancer cell line. Moreover, to study the effect of glucose on metformin-mediated EMT inhibition, all experiments were performed in two glucose levels, similar to non-fasting blood sugar (7.8 mM) and hyperglycemic (17.5 mM) conditions. The results showed reduction of mesenchymal markers, including vimentin and β-catenin, and induction of epithelial marker, E-cadherin, by metformin in both glucose concentrations. Furthermore, wound-healing and invasion assays showed a significant decrease in cell migration and invasion after metformin treatment in both glucose levels. In conclusion, our results indicated that metformin strongly inhibited EMT of gastric cancer cells in conditions mimicking normo and hyperglycemic blood sugar

Metformin effects on EMT markers in two glucose levels.

<p>(A) The cells were treated with metformin for 72 hours in two glucose concentrations and the desired genes were quantified by real-time qPCR. For normalization, GAPDH was amplified in each sample. Each column shows the mean and SD of three independent experiments, performed in triplicate. (B) Western blot analysis of cells treated with 10 mM metformin for 24 to 72 hours in two different glucose concentrations. The GAPDH band, which is considered as control, confirms the integrity and equal loading of protein.</p

Glucose effects on metformin-inhibited cell invasion.

<p><b>(</b>A & B) AGS cells were treated with metformin for 24 hours and the cell invasion was measured in the Culturex 96 well BME invasion assay kit by counting the number of cells invading underside of BME (*<i>p</i> ≤ 0.01, **<i>p</i> ≤ 0.001 and ***<i>p</i> ≤ 0.0001). (C) Effect of high- and low-glucose media on cell invasion analyzed by JMP and levels not connected by same letter are significantly different (<i>p</i> ≤ 0.05).</p