Ginsenoside Rb2 inhibits epithelial-mesenchymal transition of colorectal cancer cells by suppressing TGF-β/Smad signaling

Treating colorectal cancer (CRC) continues to be a clinical challenge. Studies have shown that epithelial-mesenchymal transition (EMT) is a critical step in tumor progression and transforming growth factor-β1 (TGF-β1) signaling has been shown to play a crucial role in EMT. Here, we investigate the inhibition effect of Ginsenoside Rb2, main bioactive component of ginseng, in human colorectal cancer cells via TGF-β1. The current study aims to study the inhibitory effect of Ginsenoside Rb2 on HCT116 and SW620 cells and its anti-tumor mechanism. Histomorphological analysis and western blot analysis were performed to evaluate expression of TGF-β1 in human cancerous colon samples and the adjacent normal samples. The docking simulation assay were performed to explore the potential mode of binding of Ginsenoside Rb2 to the TGF-β1 protein. CCK8, adhesion and invasion assay were used to assess the effects of Ginsenoside Rb2 in HCT116 and SW620 cells. RT-PCR, Western blot and Immunohistochemical staining were employed to detect the TGF-β1-related signaling pathways in the colon cancer cells and/or xenograft mice. The expression of TGF-β1 in human cancerous colon samples was significantly increased compared with the adjacent normal samples. Ginsenoside Rb2 inhibit the growth, adhesion, EMT and metastasis of human colorectal cancer cells. The docking simulation assay confirmed that Ginsenoside Rb2 bound to the hydrophobic pocket of TGF-β1, which partially overlaps with the binding sites on TGF-β1, and thus disrupted TGF-β1 dimerization. Western Blot analysis further confirmed that Ginsenoside Rb2 could inhibit the expression of TGF-β1 in vitro and in vivo. Furthermore, Ginsenoside Rb2 could inhibit the expression of Smad4 and phosphorylated Smad2/3. Ginsenoside Rb2 could inhibit EMT of colorectal cancer cells through the TGF-β1/Smad signaling, and might be a potential candidate for the treatment of colorectal cancer.