Background: Perihilar cholangiocarcinoma (PHCC) is the most common type of cholangiocarcinoma with the worst prognosis. Radical resection of PHCC is difficult; thus, few effective biomarkers or useful molecular profiles for PHCC have been reported in recent years. Methods: In this study, we screened potential biomarkers for PHCC using exon and transcriptome sequencing with PHCC tissues and paired normal tissues, and confirmed that transcription factor 7(TCF7) was upregulated in PHCC using qRT-PCR, western blotting and immunohistochemistry. The correlations between TCF7 and clinicopathological factors were analyzed with Chi-square test, and the prognostic significance of TCF7 was evaluated with univariate and multivariate analysis in two independent cohorts. Moreover, the functions of TCF7 and its main effectors in PHCC cells proliferation, invasion, and migration were investigated with in vitro and in vivo experiments. Findings: TCF7 expression was upregulated in PHCC and it was an unfavorable prognostic biomarker. c-Myc was a main effector of TCF7 in PHCC cells and responsible for TCF7-induced proliferation, invasion, and migration of PHCC cells. With qRT-PCR screening, FOSL1 was also identified as a downstream target gene of TCF7 and was required in TCF7-induced PHCC proliferation. Triple-positive expression of TCF7, c-Myc, and FOSL1 predicted a much worse prognosis in patients with PHCC than TCF7 expression alone. Interpretation: TCF7 correlated with poor prognosis of PHCC by promoting proliferation, invasion, and migration of PHCC, which required the participation of its target gene c-Myc and FOSL1. Triple-positive expression of TCF7, c-Myc, and FOSL1 was a more sensitive factor to predict prognosis than TCF7 expression alone in patients with PHCC. These results suggested that postoperative detection of TCF7, c-Myc, and FOSL1 may be useful for stratifying patients with a high risk of unfavorable prognosis and that suppressing TCF7 or its downstream effectors may be a promising strategy for the treatment of PHCC. Funding: Our study was supported by National Natural Science Foundation of China (Grant no. 81601668), Shandong Province Major Research and Design Program (Grant No. 2018GSF118169), Jinan City Science and Technology Development Program (Grant No. 201805017, 201805013), and Hengrui Hepatobiliary and Pancreatic Foundation (Grant No.Y-2017-144). Declaration of Interest: We declare no conflicts of interest. Ethical Approval: This study was approved by the Qilu Hospital of Shandong Univeristy. The Laboratory Animal Care and Use Committees of the hospital approved all experimental procedures. Written informed consents were received from all patients.
