Copper transporter 1 contributes to the progression of cholangiocarcinoma

Cholangiocarcinoma (CCA) is characterized by poor prognosis and a lack of effective biomarkers and therapeutic targets. Although copper dysregulation has been implicated in CCA, the role of the copper transporter SLC31A1 (CTR1) in its progression remains poorly understood.

The mRNA and protein levels of SLC31A1 in tumor and adjacent non-tumor tissues was evaluated by RT-PCR and enzyme-linked immunosorbent assay, respectively. Tissue copper concentrations were determined using a colorimetric complexation assay. Correlations between SLC31A1 expression, copper accumulation, and clinicopathological parameters were evaluated using Pearson's analysis. Cell proliferation and colony formation were assessed by the cell counting kit 8 and colony formation assays, respectively. Mitochondrial function was assessed by measuring intracellular ATP levels, reactive oxygen species (ROS) production, and the glutathione redox ratio.

Elevated SLC31A1 expression was significantly associated with microvascular invasion, larger tumor size (≥5 cm), and advanced AJCC stage (III-IV). Both SLC31A1 mRNA and protein levels were significantly upregulated in CCA tissues compared with adjacent non-tumor tissues and correlated with copper accumulation. In vitro, SLC31A1 was highly expressed across multiple CCA cell lines. Silencing SLC31A1 in RBE cells impaired cell proliferation and colony formation. Mechanistically, depletion of SLC31A1 increased intracellular ROS, reduced the GSH/GSSG ratio, and decreased ATP production, indicating disruption of mitochondrial function and redox homeostasis.

SLC31A1 promotes cholangiocarcinoma progression by maintaining copper homeostasis, mitochondrial integrity, and redox balance. These findings suggest that SLC31A1 may serve as a potential prognostic biomarker and a candidate therapeutic target.