Elevation of Serum KL-6 mucin Levels in Patients with Cholangiocarcinoma

Background/Aims: KL-6 mucin is a type of MUC1 mucin. Previous immunohistochemical studies by the authors revealed that, in liver cancer tissues, KL-6 mucin expressed only in intrahepatic cholangiocarcinoma (CC) but not in hepatocellular carcinoma (HCC). The current study performed serological analysis to evaluate KL-6 mucin levels in sera from various liver cancer patients and healthy individuals. Methodology: Enzyme-linked immunosorbent assay was used to measure KL-6 mucin levels in sera from 8 CC patients, 27 HCC patients, 30 metastatic liver cancer (MC) patients, and 19 healthy individuals. Results: Serum KL-6 mucin levels were significantly higher in CC patients than in healthy individuals (p<0.0001), HCC patients (p<0.0001), and MC patients (p<0.001). Receiver operating characteristic analysis determined the cut-off level of serum KL-6 mucin levels to be 240 U/mL (CC vs. healthy, p<0.001) or 248 U/mL (CC vs. HCC, p<0.001). Using 248 U/mL as a cut-off value, the positive rate for CC patients, healthy individuals, and HCC patients was 100.0%, 15.8%, and 18.5%, respectively. Conclusions: Elevation of serum KL-6 levels was detectable in CC patients. Thus, KL-6 might be a useful serological marker to distinguish CC patients from HCC patients.