GLRX and neoplasm: Next we showed that depletion of the glutathione pool in tumor cells in vitro and tumors in vivo, using the γ-glutamyl-cysteine synthetase inhibitor buthionine sulfoximine (BSO) (28), led to increased PPP flux and Grx activity and an increased rate of hyperpolarized [1-13C]DHA reduction in two different tumor models, thus demonstrating that the rate does not depend only on the levels of GSH.