Until now, very little has been known about the antioxidant capacity of squalene and
its effect on human breast tumourigenesis. In the present work, we investigated squalene's
scavenging properties and its effect on cell proliferation, cell cycle profile, apoptosis,
reactive oxygen species (ROS) level and oxidative DNA damage, using human breast cell
lines. Our results showed that squalene neither possesses scavenging activity nor
significantly alters cell proliferation rates, the cell cycle profile or cell apoptosis
in human mammary epithelial cells (MCF10A), minimally invasive (MDA-MB-231) breast
cancer cells, and highly invasive (MCF7) breast cancer cells. However, we found that
squalene did exert the following effects on MCF10A epithelial cells in a dose-dependent
manner: (a) it decreased intracellular ROS level, (b) it prevented H(2)O(2)-induced
oxidative injury, and (c) it protected against oxidative DNA damage. Interestingly,
squalene did not exert these effects on MCF7 and MDA-MB-231 cancer cells. Therefore,
our data suggest that squalene, found in high amounts in virgin olive oils, could
be partially responsible for the lower incidence of breast cancer in populations that
consume the Mediterranean diet due to its protective activity against oxidative DNA
damage in normal mammary cells.
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