Major histocompatibility complex class I expression impacts on patient survival and type and density of immune cells in biliary tract cancer.

BACKGROUND: Biliary tract cancers (BTC) are rare malignant tumours with a poor prognosis. Previously, we have presented a detailed characterisation of the inflammatory infiltrate in BTC. Here, we analysed the impact of the expression of major histocompatibility complex class I (MHC I) on patient survival and the quantity, as well as the quality of tumour-infiltrating immune cell types in BTC. METHODS: MHC I expression was assessed semi-quantitatively in 334 BTC, including extrahepatic (n=129) and intrahepatic cholangiocarcinomas (n=146), as well as adenocarcinomas of the gallbladder (n=59). In addition, 71 high-grade biliary intraepithelial lesions (BilIN 3) were included. Results were correlated with data on antitumour inflammation and investigated with respect to their association with clinicopathological variables and patient survival. RESULTS: BTC showed a wide spectrum of different MHC I expression patterns ranging from complete negativity in some tumours to strong homogenous expression in others. In BilIN 3, significantly higher MHC I expression levels were seen compared to invasive tumours (P=0.004). Patients with strong tumoural MHC I expression had a significantly higher overall survival probability (median survival benefit: 8 months; P=0.006). MHC I expression strongly correlated with the number of tumour-infiltrating T-lymphocytes (CD4(+) and CD8(+)) and macrophages. CONCLUSIONS: Differences of MHC I expression predict patient outcome and show correlations with specific components of the inflammatory infiltrate in BTC. These findings contribute to a better understanding of immune response and immune escape phenomena in cholangiocarcinogenesis.

BRAF V600E-specific immunohistochemistry reveals low mutation rates in biliary tract cancer and restriction to intrahepatic cholangiocarcinoma.

BRAF mutations have emerged as an important predictive biomarker for metastasized melanoma. Other types of cancer may also benefit from BRAF mutation-targeted therapies. In biliary tract cancer, reported BRAF mutation rates are highly controversial, ranging from 0 to 33% in adenocarcinoma of the gallbladder and 0 to 22% in cholangiocarcinoma. We here analyzed tissue microarrays of a large cohort of biliary tract cancer (n=377) including 159 intrahepatic cholangiocarcinomas, 149 extrahepatic cholangiocarcinomas, and 69 adenocarcinomas of the gallbladder for BRAF V600E mutation using a highly sensitive immunohistochemical screening approach implementing the BRAF V600E protein-specific antibody VE1. All VE1-positive cases as well as 42 VE1-negative cases were additionally analyzed by Sanger sequencing. In total, only 5 VE1-positive cases were detected (5/377; 1%). BRAF V600E mutation was confirmed by direct sequencing in all cases. All 5 mutated cases were intrahepatic cholangiocarcinomas (5/159; 3%). None of the extrahepatic cholangiocarcinomas and adenocarcinomas of the gallbladder were VE1 positive. Apart from the subtype restriction of BRAF V600E mutation to intrahepatic cholangiocarcinoma and a female predominance (4 female, 1 male), no significant correlation with clinicopathological data and patient outcome was detected. In conclusion, we demonstrate that BRAF V600E mutation is a rare event in biliary tract cancer, accounting for only 1% of all subtypes, and is restricted to intrahepatic cholangiocarcinoma. In addition, we demonstrate that VE1 immunohistochemistry is a feasible approach to routinely screen for BRAF V600E mutation in biliary tract cancer patients, thereby facilitating the detection of rare patients who may benefit from BRAF mutation-targeted therapies.