CAT and breast carcinoma: Hsieh et al.’s chemo-preventive study found that tocotrienols were able to alter the redox status of MCF-7 and MDA-MB-231 breast cancer cells by selectively increasing the basal levels of antioxidants (anti-thioredoxin) in MDA-MB-231 cells, increasing glutathione peroxidase (Gpx) expression (by δ-tocotrienol) and catalase (CAT) activity [14].