Laminaria japonica cyclic peptides exert anti-colorectal carcinoma effects through apoptosis induction in vitro and in vivo.

Laminaria japonica is consumed as a health food and used as a traditional medicine because of its biochemical and pharmacological abilities. However, the anti-tumor effect of L. japonica peptides has not been well explored. In the current study, three novel L. japonica cyclic peptides (LCPs) were isolated using an anti-cancer activity tracking method. LCP-3 [cyclo-(Trp-Leu-His-Val)] significantly induced apoptosis in Caco-2 cells in vitro. LCP-3 increased the Bax/Bcl-2 ratio, activated caspases, and regulated the p53/murine double minute 2 network. LCP-3 blocked Caco-2 cells in G0/G1 phase, which was accompanied by the inhibition of cyclin expression. Furthermore, LCP-3 inhibited colon cancer growth and induced cancer cell apoptosis in tumor-bearing mice. Notably, LCP-3 might be a potential agent for the prevention of colon cancer.