Selenium (Se) is an essential
micronutrient that functions as a redox gatekeeper through its incorporation into
proteins to alleviate oxidative stress in cells. Although the epidemiological data are somewhat controversial, the results of many studies suggest that inorganic and organic forms of Se negatively affect
cancer progression, and that several
selenoproteins, such as GPXs, also play important roles in
tumor development. Recently, a few scientists have examined the relationship between Se and
metastasis, a late event in
cancer progression, and have evaluated the potential of Se as an anti-angiogenesis or anti-
metastasis agent. In this review, we present the current knowledge about Se compounds and
selenoproteins, and their effects on the development of
metastasis, with an emphasis on cell migration, invasion, and angiogenesis. In the
cancers of breast, prostate, colorectal,
fibrosarcoma,
melanoma, liver, lung,
oral squamous cell carcinoma, and brain
glioma, there is either clinical evidence linking
selenoproteins, such as
thioredoxin reductase-1 to
lymph node metastasis; in vitro studies indicating that Se compounds and
selenoproteins inhibited cell motility, migration, and invasion, and reduced angiogenic factors in some of these
cancer cells; or animal studies showing that Se supplementation resulted in reduced microvessel density and
metastasis. Together, these data support the notion that Se may be an anti-metastastatic
element in addition to being a
cancer preventative agent.