As a result, we explored the influence of NaSH on SpCAT in colorectal cancer cells and M17 human neuroblastoma cells treated with rotenone, which should allow discriminating between a temporarily (CAT–Fe(IV)=O) and an irreversibly (CAT–Fe(III)–sulfheme) inactive state of the enzyme (Fig. 6h,i). Here, CAT is linked to colorectal cancer.