Ceruloplasmin as a prognostic marker in patients with bile duct cancer

Abstract

Background and Aim Bile duct (BD) cancer is one of the lethal cancers, presenting difficulties in early diagnosis and limited treatment modalities. Despite current advances in biomarker research, most studies have been performed in Western populations. Ceruloplasmin (CP), as one of the major copper-carrying protein, has known for a promising biomarker in patients with several malignant diseases. However, there are few studies for CP as biomarker or prognostic factor in patients with BD cancer, especially Korean patients. Therefore, the purpose of this study was to find out the relationship between CP and BD cancer by DNA microarray, to confirm the overexpression of ceruloplasmin in BD cancer tissue by immunohistochemistry, and to test CP as a potential candidate for biomarker or prognostic factor for Korean BD cancer patients. Methods We performed tissue microarray experiment with 79 bile duct cancer tissue samples and 21 normal bile duct tissue samples which obtained from 2003 to 2011. Candidate genes that has positive correlation with T, N stage and perineural invasion which adjusted for age and sex were drawn with multivariate analysis. Genes considered significant were assessed by gene functional classification, gene function and pathway annotation, and data mining to explore the association of each gene with disease. Tissue expression of candidate gene was evaluated with an immunohistochemical study. To confirm clinical impact of tissue expression, clinicopathological analysis including survival rates was performed. Results The mean age of the study population was 65.4 years and the male to female ratio was 1.82 to 1. After curative resection (n= 73, 92.4%), 5-year survival rate (5YSR) was 78.6% for those with tumors limited to bile duct, and 51.8% for those with tumors extending beyond bile duct (p=0.067). Node negative patients had higher 5YSR compared with node positive patients (70.1% vs. 0%, p=0.001). Perineural invasion negative patients had higher 5YSR compared with perineural invasion positive patients (85.0% vs. 43.4%, p=0.004). Comparing cancer and normal bile duct tissue, we identified 29091 differentially expressed genes. CP, SCEL, and MUC16 had positive coefficients with a log2 ratio >1 for advanced T, N stage and perineural invasion cancer tissue. Strong immunohistochemical expression of CP was dominant in tumors with advanced T stage (p>0.999) and perineural invasion (p=0.316). Conclusions Although we found a tendency for increased ceruloplasmin expression in advanced T stage cancer with perineural invasion, that finding did not achieve statistical significance. A larger number of patients will be needed to validate ceruloplasmin as a candidate prognostic marker for bile duct cancer.