Natural products as anti-invasive and anti-metastatic agents.

Invasion and metastasis, the hallmark of malignant tumor, is the main reason for the clinical death of most cancer patients. Tumor invasion and metastasis are complex, multi-step biochemical processes, which involve cell detachment, invasion, migration, intravasation and circulation, implantation, angiogenesis and proliferation. Therefore, how to prevent tumor metastasis has been the biggest challenge in cancer chemotherapy. In recent years, many natural products have been found to have anti-invasive and anti-metastatic activities. In this paper, these natural compounds are classified as polyphenols, terpenoids, alkaloids, steroids and saponins, saccharides, macrolides, amides and others, their anti-invasive and anti-metastatic activities as well as their biological targets are reviewed.