Effects of plant-based medicinal food on postoperative recurrence and lung metastasis of gastric cancer regulated by Wnt/β-catenin-EMT signaling pathway and VEGF-C/D-VEGFR-3 cascade in a mouse model

Abstract

Background: The plant-based medicinal food (PBMF) is a functional compound extracted from 6 medicinal and edible plants: Coix seed, L. edodes, A. officinalis L., H. cordata, Dandelion, and G. frondosa. Our previous studies have confirmed that the PBMF possesses anti-tumor properties in a subcutaneous xenograft model of nude mice. This study aims to further investigate the effects and potential molecular mechanisms of the PBMF on the recurrence and metastasis of gastric cancer (GC). Methods: Postoperative recurrence and metastasis model of GC was successfully established in inbred 615 mice inoculated with mouse forestomach carcinoma (MFC) cells. After tumorectomy, 63 GC mice were randomly divided into five groups and respectively subject to different treatments for 15 days as below: model control group, 5-Fu group, and three doses of PBMF (43.22, 86.44, 172.88 g/kg PBMF in diet respectively). The inhibition rate (IR) of recurrence tumor weights and organ coefficients were calculated. Meanwhile, histopathological changes were examined and the metastasis IR in lungs and lymph node tissues was computed. The mRNA expressions related to the canonical Wnt/β-catenin signaling pathway, epithelial-mesenchymal transition (EMT) and lymphangiogenesis were detected by RT-qPCR in recurrence tumors and/or lung tissues. Protein expressions of β-catenin, p-β-catenin (Ser33/37/Thr41), GSK-3β, p-GSK-3β (Ser9), E-cadherin, and Vimentin in recurrence tumors were determined by Western Blot. LYVE-1, VEGF-C/D, and VEGFR-3 levels in recurrence tumors and/or lung tissues were determined by immunohistochemistry staining. Results: The mRNA, as well as protein expression of GSK-3β were up-regulated and the mRNA expression of β-catenin was down-regulated after PBMF treatment. Meanwhile, the ratio of p-β-catenin (Ser33/37/Thr41) to β-catenin protein was increased significantly and the p-GSK-3β (Ser9) protein level was decreased. And PMBF could effectively decrease the mRNA and protein levels of Vimentin while increasing those of E-cadherin. Furthermore, PBMF markedly reduced lymphatic vessel density (LVD) (labeled by LYVE-1) in recurrence tumor tissues, and mRNA levels of VEGF-C/D, VEGFR-2/3 of recurrence tumors were all significantly lower in the high-dose group. Conclusions: PBMF had a significant inhibitory effect on recurrence and lung metastasis of GC. The potential mechanism may involve reversing EMT by inhabiting the Wnt/β-catenin signaling pathway. Lymphatic metastasis was also inhibited by PBMF via down-regulating the activation of the VEGF-C/D-VEGFR-2/3 signaling cascade.