GLRX2 and carcinoma: However, it was later shown in human carcinoma HeLa [16, 17] and neuroblastoma [18] cells that when the TrxR activity is lost, the glutaredoxin 2 (Grx2) system, playing a backup role, is able to reduce both cytosolic Trx1 and mitochondrial Trx2 using glutathione in the presence of NADPH, indicating the need to consider both systems when evaluating Hg toxicity.