An Antioxidant, Probucol, Induces Anti‐angiogenesis and Apoptosis in Athymic Nude Mouse Xenografted Human Head and Neck Squamous Carcinoma Cells

Probucol is a very strong synthetic antioxidant that was been safely used for the treatment of hyperlipidemia in Japan since 1985. It has been reported that lipid oxidation products can alter growth factor production, which could influence smooth muscle cell proliferation. Oxidized low density lipoprotein can influence smooth muscle cell proliferation by enhancing the expression of platelet‐derived growth factor (PDGF)‐AA gene and PDGF receptor in vascular smooth muscle cell. Further, free radical reactions can cause irreversible alterations of genomic constituents during the initiation phase of carcinogenesis. Antioxidant is considered to protect lipids and low density lipoprotein (LDL) from oxidation, which potentially inhibits angiogenesis, and rapid removal of free radicals by antioxidants could have an anti‐carcinogenic effect. In the present study, we investigated whether antioxidant treatment with probucol had an antitumor effect on KB cells, a human head and neck squamous carcinoma cell line. Probucol did not have any effect on KB cells in vitro, but probucol treatment of KB cells xenografts in mice had a significant antitumor effect through anti‐angiogenic and apoptosis‐inducing actions. These results support the idea that probucol is useful for preventing and/or treating cancer.