Cancer metastasis refers to the spread of
cancer cells from the primary
neoplasm to distant sites, where secondary
tumors are formed, and is the major cause of death from
cancer. Natural
phytochemicals containing phenolic compounds have been widely demonstrated to have the capability to prevent
cancer metastasis. Among phenolic compounds,
flavonoids are a very large subclass, and they are abundant in food and nutraceuticals. The number of reports demonstrating that
flavonoids are an effective natural inhibitor of
cancer invasion and
metastasis is increasing in the scientific literature.
Catechin derivatives, (−)-epigallocatechin-3-gallate, (−)-
epigallocatechin, (−)-epicatechin-3-gallate,and (−)-
epicatechin, are the most studied compounds in this topic so far;
genistein/
genistin,
silibinin,
quercetin, and
anthocyanin have also been widely investigated for their inhibitory activities on invasion/
metastasis. Other
flavonoids in dietary vegetable foods that are responsible for anti-invasive and anti-metastatic activities of
tumors include
luteolin,
apigenin,
myricetin,
tangeretin,
kaempferol,
glycitein,
licoricidin,
daidzein, and
naringenin. To effectively overcome the metastatic cascade, including cell-cell attachment, tissue barrier degradation, migration, invasion, cell-matrix adhesion,and angiogenesis, it is essential that a bioactive compound prevent
tumor cells from metastasizing. This review summarizes the effects of
flavonoids on the metastatic cascade and the related
proteins, the in vitro anti-invasive activity of
flavonoids against
cancer cells, and the effects of
flavonoids on antiangiogenic and in vivo anti-metastatic models. The available scientific evidence indicates that
flavonoids are a ubiquitous dietary phenolics subclass and exert extensive in vitro anti-invasive and in vivo anti-metastatic activities.