RRM2 and head and neck squamous cell carcinoma: RRM2 stabilizes ANXA1/activates AKT to confer resistance to sunitinib and PD-1 blockade in renal cancer [46], is linked to docetaxel resistance in prostate cancer [47], activates TGF-β to drive pancreatic cancer progression/metastasis [48], and in Head and Neck Squamous Cell Carcinoma (HNSCC), binds TXNRD1 to regulate PD-L1/redox balance; targeting TXNRD1 enhances immunotherapy-mediated ferroptosis via increased CD8+ T cells and reduced PD-L1 [49].