MDH2 and cancer: To investigate the possible effect of mtGR overexpression on Krebs cycle regulation, during tumor progression, protein levels of citrate synthase, succinate dehydrogenase (SDH), and malate dehydrogenase-2 (MDH 2), an isoform found to be increased in cancer cells [25,26], were analyzed in total extracts from tumors produced in NOD-SCID mice, upon inoculation with 1 × 106 HepG2mtGFPGR or HepG2mtGFP cells (Figure 7A,B).