In laboratory-grown human cancer cells, adding a specific form of selenium reduces DNA damage from a chemical oxidant in one type of cell (mesothelioma) but not in another (colon cancer), showing that different cancer cells respond differently to the same treatment.

In laboratory-grown human cancer cells, adding a small amount of selenite boosts an enzyme that reduces DNA damage caused by hydrogen peroxide, but this does not help the cells survive the stress.

When human colon and mesothelioma cancer cells are exposed to 100 nM selenite, the activity of glutathione peroxidase increases significantly, while catalase activity remains unchanged, indicating a specific effect on one selenium-dependent enzyme.

In human cancer cells exposed to hydrogen peroxide, higher levels of glutathione peroxidase reduce certain types of DNA damage but do not prevent cell death, suggesting that this specific DNA damage is not the main reason cells die under these conditions.

In human cancer cells grown in the lab, hydrogen peroxide and t-butyl hydroperoxide do not produce detectable double-strand breaks or DNA-protein cross-links, indicating that the primary type of DNA damage caused by these substances under these conditions is single-strand breaks.