Recent studies suggest that metformin, which is commonly used as an oral anti-hyperglycemic agent of the biguanide family, may reduce cancer risk and improve prognosis, but the mechanisms by which metformin affects various cancers, including gastric cancer, remains unknown. The goal of the present study was to evaluate the effects of metformin on human gastric cancer cell proliferation in vitro and in vivo and to study microRNAs (miRNA) associated with antitumor effect of metformin. We used MKN1, MKN45, and MKN74 human gastric cancer cell lines to study the effects of metformin on human gastric cancer cells. Athymic nude mice bearing xenograft tumors were treated with or without metformin. Tumor growth was recorded after 4 weeks, and the expression of cell-cycle-related proteins was determined. In addition, we used miRNA array tips to explore the differences among miRNAs in MKN74 cells bearing xenograft tumors treated with or without metformin in vitro and in vivo. Metformin inhibited the proliferation of MKN1, MKN45, and MKN74 in vitro. Metformin blocked the cell cycle in G 0 -G 1 in vitro and in vivo. This blockade was accompanied by a strong decrease of G 1 cyclins, especially in cyclin D1, cyclin-dependent kinase (Cdk) 4, Cdk6 and by a decrease in retinoblastoma protein (Rb) phosphorylation. In addition, metformin reduced the phosphorylation of epidermal growth factor receptor and insulin-like growth factor-1 receptor in vitro and in vivo. The miRNA expression was markedly altered with the treatment of metformin in vitro and in vivo. Various miRNAs altered by metformin also may contribute to tumor growth in vitro and in vivo. Mol Cancer Ther; 11(3); 549-60. Ó2012 AACR.

Abstract. Metformin is a commonly used oral antihyperglycemic agent of the biguanide family. Recent studies suggest that metformin may reduce cancer risk and improve prognosis. However, the antitumor mechanism of metformin in several types of cancers, including hepatocellular carcinoma (HCC), has not been elucidated. The goal of the present study was to evaluate the effects of metformin on HCC cell proliferation in vitro and in vivo, and to study microRNAs (miRNAs) associated with the antitumor effect of metformin in vitro. We used the cell lines Alex, HLE and Huh7, and normal hepatocytes to study the effects of metformin on human HCC cells. In an in vivo study, athymic nude mice bearing xenograft tumors were treated with metformin or left untreated. Tumor growth was recorded after 4 weeks, and the expression of cell cycle-related proteins was determined. Metformin inhibited the proliferation of Alex, HLE and Huh7 cells in vitro and in vivo. Metformin blocked the cell cycle in G0/G1 in vitro and in vivo. This blockade was accompanied by a strong decrease of G1 cyclins, especially cyclin D1, cyclin E and cyclin-dependent kinase 4 (Cdk4). In addition, microRNA (miRNA) expression was markedly altered by the treatment with metformin in vitro and in vivo. In addition, various miRNAs induced by metformin also may contribute to the suppression of tumor growth. Our results demonstrate that metformin inhibits the growth of HCC, possibly by inducing G1 cell cycle arrest through the alteration of microRNAs.

The OTSC is effective for treating GI bleeding, fistulae as well as perforations, and the OTSC technique proofed effective treatment for perforation after ESD.

Endoscopic submucosal dissection (ESD) is not a common treatment for colorectal neoplasms because of its technical difficulties and has a higher incidence of complication. In particular, perforation is one of the severe complications and these patients require surgical intervention. However, whether prophylactic closure after colorectal ESD prevents perforation and other complications is not known. In the present study, we assessed the efficacy and safety of prophylactic closure for a large mucosal defect after colorectal ESD using a conventional clip and over-the-scope clip (OTSC) system. From April 2010 to December 2012, 68 patients with colorectal tumors were treated with ESD. The prohylactic closure was indicated for patients with excessive coagulation in the muscularis propria or larger resection size. The closure group reduced the peritoneal inflammatory reaction and abdominal symptoms without increasing complications. The closure group also had a significantly lower WBC count (post operative day 1), CRP (post operative day 4) and abdominal pain after colorectal ESD compared to the non-closure group. Perforation occurred in 1 case, and postoperative bleeding in 2 cases, with only 1 bleeding case needing an emergency endoscopy in the non-closure group. One perforation case needed emergency surgery because the endoscopic treatment was ineffective. Without increasing adverse effects, the prophylactic closure efficiently reduced the inflammatory reaction and abdominal symptoms of colorectal ESD in patients with large superficial colorectal neoplasms.

No abstract