Glutaredoxin 1 promotes sorafenib resistance in renal cell carcinoma through ferroptosis suppression: Integrative...

Sorafenib resistance has limited the therapeutic efficacy in advanced renal cell carcinoma (RCC). Glutaredoxin 1 (GRX1, also known as GLRX), a redox-regulating oxidoreductase belonging to the thioredoxin superfamily, may mediate this resistance through ferroptosis suppression, but the underlying mechanisms remain incompletely understood.

GRX1 expression and sorafenib sensitivity were analyzed using The Cancer Genome Atlas-Kidney Renal Clear Cell Carcinoma (TCGA-KIRC, n = 601), Gene Expression Omnibus (GEO, n = 14), and Genomics of Drug Sensitivity in Cancer (GDSC, 752 cell lines) datasets. Functional experiments including lentiviral-mediated GRX1 knockdown (shRNA) and overexpression were performed in human RCC cell lines 786-O and Caki-1 and their sorafenib-resistant derivatives established through chronic drug exposure. The expression of ferroptosis-related proteins, including glutathione peroxidase 4 (GPX4), solute carrier family 7 member 11 (SLC7A11), and acyl-CoA synthetase long-chain family member 4 (ACSL4), was assessed by Western blotting. Ferroptosis was further evaluated by measuring lipid reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH), and intracellular Fe2 + levels, and confirmed by pharmacological rescue with ferroptosis-specific inhibitors. BALB/c nude mouse xenograft models (n = 6 per group, four treatment arms per cell line) validated findings in vivo. Three machine learning algorithms, linear regression (LR), random forest (RF, 500 trees), and elastic net (EN, α=0.5), were constructed for exploratory prediction of sorafenib sensitivity.

GRX1 was significantly upregulated in RCC and correlated with advanced stage and grade. A treatment-dependent paradox was observed: high GRX1 was associated with better overall survival in TCGA-KIRC but promoted sorafenib resistance in functional experiments. GRX1 knockdown enhanced sorafenib sensitivity and increased ferroptotic responses, with decreased GPX4 and SLC7A11, increased ACSL4, elevated lipid ROS, MDA, and Fe2 + , and depleted GSH, whereas overexpression conferred resistance. Pharmacological rescue by ferrostatin-1 and deferoxamine, but not by apoptosis or necroptosis inhibitors, identified ferroptosis as the dominant cell death mechanism. In sorafenib-resistant cells, GRX1 was elevated 2.5-3.1-fold, and its knockdown restored sensitivity in vitro and reduced final xenograft tumor weights by approximately 55% in sh-GRX1+sorafenib groups versus sh-NC+sorafenib controls. Random Forest showed modest but reproducible exploratory predictive performance for sorafenib sensitivity (R² = 0.199).

The treatment-dependent role of GRX1, which is protective in untreated tumors but can promote sorafenib resistance in treated cancers, establishes it as a critical ferroptosis-suppressing mediator and a potential therapeutic target for overcoming sorafenib resistance in RCC.