Characterization of Hepatocellular Carcinoma Patients with FGF19Amplification Assessed by Fluorescence in situ Hybridization: A Large Cohort Study

Background:FGF19amplification is a relatively novel type of genetic aberration that has been proposed to be a driver of hepatocarcinogenesis. Selective inhibitors of FGFR4, a receptor of FGF19, have been developed as targeted therapies for hepatocellular carcinoma (HCC). Despite the role of FGF19in mediating HCC progression, the clinicopathological characterization of patients exhibiting FGF19amplification remains unclear. Immunohistochemical staining is the simplest and most widely used method of identifying aberrations in the FGF19gene, although its specificity is very low. Methods:This study investigated the prognostic significance of FGF19amplification in a large cohort of 989 HCC patients using fluorescence in situ hybridization (FISH), which has a high degree of specificity. In addition, FISH data from formalin-fixed, paraffin-embedded sections were compared with copy number variation (CNV) data obtained from fresh frozen sections to validate the use of FISH as a diagnostic tool. Results:FGF19amplifications were detected by FISH in 51 (5.15%) of the 989 patients, and were independently associated with poor survival and a higher risk of tumor recurrence, as well as with poor prognostic factors such as a high α-fetoprotein level, hepatitis B or C virus infection, a large tumor size, microvascular invasion, and necrosis. In addition, FGF19amplification was associated with TP53mutation, and was mutually exclusive with CTNNB1mutation. The results of the FISH and CNV analyses exhibited a significant concordance rate of 96% (κ = 0.618, p< 0.001). Conclusions:These data indicate that FGF19amplification represents a unique molecular subtype associated with poor prognostic characteristics, which supports the hypothesis that the FGF19-FGFR4signaling pathway plays an important role in hepatocarcinogenesis. We have also demonstrated that FISH is a viable alternative to CNV analysis, offering a number of advantages in the clinical setting.