Effects of diphyllin as a novel V-ATPase inhibitor on gastric adenocarcinoma

The natural compound diphyllin, a cytostatic lignan isolated from Cleistanthus collinus, can dramatically inhibit the proliferation and induce the apoptosis of human gastric cancer cells, SGC7901. Our study found that diphyllin can inhibit the expression of V-ATPases in a dose-dependent manner, decrease the internal pH (pHi) and reverse the transmembrane pH gradient in SGC7901 cells. Changes of the pH gradient were positively correlated with diphyllin concentration. Further study found that diphyllin treatment caused a decrease in phospho-LRP6, but not in LRP6. β-catenin in Wnt/β-catenin signaling and its target genes, c-myc and cyclin-D1, were also decreased with the inhibition of V-ATPases. Therefore, diphyllin could be characterized as a new V-ATPase inhibitor in treating gastric cancer and inhibiting the phosphorylation of LRP6 in Wnt/β-catenin signaling.