Cancer cachexia is a multifactorial metabolic syndrome characterized by progressive skeletal muscle loss, affecting 30–60% of patients with advanced renal cell carcinoma (RCC). It significantly impacts treatment tolerance, quality of life, and prognosis, yet its diagnosis and management remain challenging due to fragmented RCC-specific evidence, particularly in the era of immune checkpoint inhibitor (ICI)-based therapy. The pathogenesis involves persistent systemic inflammation, metabolic reprogramming, and tumor–host interactions. The IL-6/STAT3 and TNF-α/NF-κB pathways are central to muscle catabolism, while tumor-derived mediators such as GDF15 and PTHrP, along with mitochondrial dysfunction, further drive cachexia progression. For prognostic assessment, CT-derived skeletal muscle mass evaluation combined with systemic inflammatory and nutritional biomarkers—including neutrophil-to-lymphocyte ratio (NLR), modified Glasgow Prognostic Score (mGPS), prognostic nutritional index (PNI), and cachexia index (CXI)—has improved risk stratification in advanced RCC. Preclinical and emerging clinical data suggest that targeted therapies may partially attenuate cachexia by modulating inflammatory signaling, while multimodal interventions integrating nutritional support and exercise rehabilitation remain the cornerstone of management. Novel strategies, such as inhibition of the GDF15/GFRAL axis, are under active investigation. Future research should prioritize identification of early biomarkers, standardization of cachexia assessment, and prospective evaluation of cachexia-directed interventions in the immunotherapy era. Integrating cachexia assessment into routine practice may ultimately enable personalized treatment and improve long-term outcomes for patients with advanced RCC.

Bladder cancer is one of the most common malignancies of the urinary system. Identifying new potential therapeutic targets and exploring molecular mechanisms are crucial for improving treatment and prognosis. The hyperpolarization-activated cyclic nucleotide-gated (HCN) channel 2, known to play a key role in various physiological and pathological processes, has an unclear function and mechanism of action in bladder cancer. We employed bioinformatics analysis and immunohistochemistry to assess the role of HCN2 in bladder cancer, integrating in vitro and in vivo models to evaluate the impact of HCN2 on cell behavior. Molecular interactions were characterized using immunoprecipitation, chromatin immunoprecipitation, and dual-luciferase reporter assays. Our investigation revealed a significant upregulation of HCN2 in bladder cancer tissues, which was predictive of a poorer clinical outcome. Functionally, HCN2 knockdown in bladder cancer impeded cell proliferation, induced apoptosis, and curtailed migration and invasion. Mechanistically, the overexpression of HCN2 contributed to the translocation of the REST transcription factor into the nucleus and facilitated its binding to the BGN promoter for transcriptional activation of its expression. This regulatory mechanism was shown to suppress ferroptosis, a form of regulated cell death, thereby enhancing the proliferative and tumorigenesis of bladder cancer cells. This study uncovers the novel mechanism by which HCN2 regulates ferroptosis via the REST-BGN axis, affecting bladder cancer cell behavior, and provides new perspectives and strategies for future clinical treatment.