Thioredoxin 1 plays a key role in S-nitrosylation of cell death receptors and apoptosis in Sorafenib-treated hepatocarcinoma cells

Sorafenib is the first line molecular targeted therapy for patients in advanced hepatocarcinoma stage. The aim of the study was the identification of the relationship between redox and antitumoral properties of Sorafenib in liver cancer cells. Sorafenib induces mitochondrial depolarization and superoxide anion production. However, this effect was counteracted by relevant drug-related scavenging activity, determined using fluorescent and EPR approaches, which were associated with a reduced Nrf2-dependent Thioredoxin 1 (Trx1) signaling. The downregulation of Trx1 was associated with NOS3-denitrosylation, low nitric oxide generation and reduction of caspase-8 activity in HepG2. The reduction of S-nitrosylation of Cys199 and Cys304 residues in CD95 was related to low caspase-8 activation in Sorafenib-treated HepG2 cells. Different overexpression and interfering in vitro designs showed that Trx1 regulated S-transnitrosylation between NOS3 and CD95, caspase-8 activation, EGFR tyrosine phosphorylation and cell proliferation. The two in vivo models, thioacetamide-induced HCC and the subcutaneous HepG2-implantation in nude mice, showed that the antitumoral properties of Sorafenib were related to reduced Trx1 expression, CD95 S-nitrosylation and caspase-8 activity in tumors.