The Exchangeable Copper-Zinc Ratio Links Sex Hormones, Tumor Burden, and Epithelial Remodeling in Colorectal Cancer

Copper (Cu)-zinc (Zn) imbalance has been implicated in colorectal cancer (CRC). Exchangeable copper (exCu), the labile circulating Cu fraction, may better reflect functionally relevant metal dysregulation than total Cu. We investigated sex-specific associations between systemic Cu-Zn indices, tumor burden, and epithelial-mesenchymal transition (EMT)-related tissue remodeling in CRC. We studied 152 CRC patients and 140 healthy controls. Serum Cu, Zn, and exCu were measured using validated analytical methods; circulating gonadotropins, sex steroids, and carcinoembryonic antigen were also assessed. EMT-related proteins (E-cadherin, vimentin, fibronectin, vinculin, MEMO1) were quantified by Western blot in paired tumor and adjacent mucosa. Analyses were sex-stratified and age-adjusted. CRC patients exhibited higher serum Cu and exCu and lower Zn than controls, resulting in a marked increase in the exCu:Zn ratio in both sexes. In patients, exCu:Zn was associated with tumor burden and pathological stage, with stronger associations with tumor size and pT stage in women and with metastatic status in men. Serum exCu:Zn was associated with tumor - normal differences in EMT-related proteins, particularly ΔE-cadherin, in both sexes. Systemic Cu-Zn disequilibrium, summarized by the exCu:Zn ratio, was associated with tumor burden and epithelial remodeling in CRC in a sex-specific manner, suggesting its potential as a biologically informative biomarker warranting further validation.