Metformin Inhibits Proliferation and Tumor Growth of QGP-1 Pancreatic Neuroendocrine Tumor Cells by Inducing Cell Cycle Arrest and Apoptosis.

Abstract

Pancreatic neuroendocrine tumors (pNETs) are rare pancreatic neoplasms, and therapeutic options for pNETs are limited. Metformin is an anti-hypoglycemic drug that appears to have anticancer effects. However, little is known about the effect of metformin on pNETs. In this study, we investigated the anti-proliferative effect of metformin on a human pNET cell line. The anti-proliferative properties of metformin were evaluated in QGP-1 and NCI-H727 cells using a cell counting kit-8 assay. Xenograft mouse models were used to assess the tumor effect in vivo. Metformin inhibited the proliferation and anti-tumor growth of QGP-1 cells, accompanied by their arrest during the cell cycle at the G0/G1 phase. Immunohistochemical analysis of tumor tissues revealed down-regulation of cyclin D1 and proliferating cell nuclear antigen in the metformin-treated group. Additionally, metformin induced apoptosis, and the expression of survivin and claspin were decreased in metformin-treated QGP-1 cells according to the apoptosis array. Furthermore, the angiogenic related protein TIMP-1 was down-regulated, and its miRNA expression was altered by metformin in QGP-1 cells. Taken together, our study demonstrated the therapeutic potential of metformin and provides molecular mechanistic insights into its anti-tumoral effect on pNETs. This study is the first one describing anti-tumoral effects in pNETs.