GPR43 Suppresses Intestinal Tumor Growth by Modification of the Mammalian Target of Rapamycin Complex 1 Activity in ApcMin/+ Mice

Objective: G protein-coupled receptor 43 (GPR43), a receptor for short-chain fatty acids, plays a role in suppressing tumor growth; however, the detailed underlying mechanism needs to be comprehensively elucidated. In this study, we investigated the role of GPR43 in inhibiting tumor growth using Apc(Min/+), a murine model of intestinal tumors. Materials and Methods: Using GPR43(-/-) Apc(Min/+) and GPR43(+/-) Apc(Min/+) mice, the number of tumors was analyzed at the end of the experimental period. Immunohistochemistry, quantitative polymerase chain reaction, and Western blotting were performed to analyze cellular proliferation and proliferation-associated signal pathways. Results: Our results revealed that GPR43 deficiency resulted in increased tumor numbers in Apc(Min/+) mice. Ki67 was highly expressed in GPR43(-/-) mice (p > 0.05). Increased expression levels of proinflammatory cytokines, including interleu kin-6 and tumor necrosis factor-alpha, and amino acid transporters were not observed in GPR43-deficient mice compared to GPR43-sufficient mice. Furthermore, GPR43-deficient tumor tissues showed enhanced mammalian target of rapamycin-mediated phosphorylated ribosomal protein 56 kinase beta-1 (p > 0.05) and phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (p > 0.05), but not Akt (protein kinase B) phosphorylation (p = 0.7088). Conclusion: Collectively, GPR43 affords protection against tumor growth at least partly through inhibition of the mammalian target of rapamycin complex 1 pathway. (C) 2021 The Author(s). Published by S. Karger AG, Basel