Cysteine-rich intestinal protein 1 (CRIP1) is overexpressed in colorectal cancer (CRC) tissues and functions as an oncogene in regulating the migration and invasion of CRC cells. However, the underlying mechanism is unclear. CRIP1 has a role in zinc absorption and functions as an intracellular zinc transport protein. Here, we aimed to focus on the function of zinc and its underlying mechanism in CRC and determine whether CRIP1 promotes invasion and CRC metastasis through excessive zinc-induced epithelial-mesenchymal transition (EMT) by affecting the phosphorylated glycogen synthase kinase (GSK)-3beta. The results showed that ZnSO4 (Zn2+) supplementation in medium increased the labile intracellular zinc content. Furthermore, excessive Zn2+ supplementation activated the GSK3/mTOR signaling pathway in both SW620 and LoVo cells, and excessive Zn2+ supplementation promoted migration, invasion, and EMT of SW620 and LoVo cells. This migration promotion was alleviated by the specific mTOR inhibitor rapamycin, indicating that the GSK3/mTOR signaling pathway was involved in this process. CRIP1 silencing increased the labile intracellular zinc content and inhibited EMT and GSK3/mTOR signaling pathway. CRIP1 silencing alleviated the zinc supplementation effects on migration, invasion, EMT, and GSK3/mTOR signaling pathway. In conclusion, excessive Zn2+ promotes migration and invasion capabilities of SW620 and LoVo cells through GSK3/mTOR signaling pathway-induced EMT.
Keywords: Excessive zinc; cysteine-rich intestinal protein 1; epithelial-mesenchymal transition; migration and invasion capabilities.