Ghrelin Affects Gastric Cancer Progression by Activating AMPK Signaling Pathway

As the endogenous ligand for the GH secretagogue receptor (GHSR), Ghrelin is aberrant expressed in multiple malignant carcinoma, and involved in regulating a number of progression of cancer, especially in metastasis and proliferation. However, the precise role of Ghrelin in tumorigenesis of gastric cancer (GC) is still poorly understood. In this study, we extensively investigated the roles and mechanisms of Ghrelin in human gastric cancer. Ghrelin levels in cancer tissues and cell lines were analyzed by immunohistochemistry, qRT-PCR, and Western blot. Functional studies were performed after Ghrelin overexpressed or knockdown in AGS cell line. Cell proliferation was evaluated in by MTT and clone formation assays. The wound healing and Transwell system were used to assess the cell migration and invasive ability of GC cells. Cell apoptosis was detected by flow cytometry, and metabolic assays were performed to reveal the function of Warburg effect in the process. Ghrelin was lowly expressed in gastric cancer tissues and cell lines. Overexpression of Ghrelin inhibited gastric cancer cell proliferation, migration, invasion, and promoted apoptosis by activating the AMPK pathway, while D-[lys3]-GHRP-6 (a GHSR agonist) treatment relieved the effect, promoting tumorigenesis. Ghrelin knockdown increased the glucose uptake and lactic acid release, suggesting that Ghrelin elicited an anti-Warburg effect via AMPK pathway to inhibit gastric tumorigenesis. Ghrelin inhibits cell proliferation, migration, and invasion by eliciting an anti-Warburg effect via AMPK signaling pathway in gastric cancer cells.