PHB2 and colorectal carcinoma: In addition, we determined other multimeric enzymes activities of electron transport chain (ETC) complexes in PHB2-knockdown CRC cells, as shown in Supplementary Fig. S2, the activities of ubiquinone-cytochrome c oxidoreductase (complex III) and cytochrome c oxidase (complex IV) were subsequently reduced, while the activity of succinate dehydrogenase (complex II) had no significant change.