Menin represses the proliferation of gastric cancer cells by interacting with IQGAP1

The multiple endocrine neoplasia type 1 gene coding the protein menin was originally identified in patients with multiple endocrine tumors, and is mainly expressed in the cell nucleus. Multiple lines of evidence have indicated that menin acts as a tumor suppressor protein interacting with other various proteins. The mechanism of menin inhibiting tumorigenesis remains unclear. The present study analyzed the expression of menin and IQ motif-containing GTPase-activating protein 1 (IQGAP1) proteins in gastric cancer tissues and cell lines, and investigated the association between these two molecules. Western blotting was used to determine the quantity of target proteins. Cell proliferation was measured using MTT assay. It was found that the protein expression of menin was lower in gastric cancer tissues and AGS cells, while the protein expression of IQGAP1 was higher, compared with the levels observed in normal tissues and GES-1 cells. Ectopic expression of IQGAP1 stimulated the proliferation of gastric cancer cells, but did not affect the expression of menin. However, overexpression of menin inhibited the proliferation of gastric cancer cells. The inhibition was partly achieved through inhibiting the expression of IQGAP1, which was accompanied by inhibition of PI3K and NF-κB expression. Taken together, the present results suggest a novel function for menin and IQGAP1 contributing to suppress the proliferation of gastric cancer cells.