J Cancer 2018; 9(18):3278-3286. doi:10.7150/jca.25775

Research Paper

The Expression of FAP in Hepatocellular Carcinoma Cells is Induced by Hypoxia and Correlates with Poor Clinical Outcomes

Baojia Zou1,#, Xialei Liu1,#, Baimeng Zhang1,#, Yihang Gong1, Chaonong Cai1, Peiping Li1, Jiafan Chen1, Shan Xing2,3, Jianxu Chen1, Siqi Peng4, Bibesh Pokhrel1, Lei Ding1, Linjuan Zeng 4,✉, Jian Li1,✉

1. Department of Hepatobiliary Surgery, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai 519000, China
2. State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China
3. Sun Yat-sen University Cancer Center, Department of Clinical Laboratory, Guangzhou 510060, China
4. Department of Oncology, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai 519000, China
# These authors contributed equally to this work.

Abstract

Fibroblast activation protein (FAP) is a serine protease that has been reported in fibroblasts and some carcinoma cells, which correlates with poor patient outcomes. FAP can be induced under hypoxia which is also vital in the malignant behaviors of cancer cells. However, the role of FAP and its correlation with hypoxia has not been investigated in HCC cancer cells. In tissues from post-surgical HCC patients in our center, we adopted immunohistochemistry staining (IHC), western blot and quantitative RT-PCR to detect the expression levels of FAP and the hypoxia related marker, hypoxia inducible factor 1α (HIF-1α). X-tile software was used for the determination of high and low expression of FAP and HIF-1α after the IHC analysis. Clinicopathological analysis, Kaplan-Meier analysis and Cox regression model were performed. In-vitro experiments were performed to confirm the relationship between FAP and hypoxia in HCC cancer cell lines (HepG2, Huh7 and MHCC97H). Results revealed that expression levels of FAP and HIF-1α were significantly correlated (Pearson r2 = 0.2753, p < 0.0001) in IHC analysis of the 138-patient cohort. Western blot and quantity RT-PCR indicated parallel changes in 11 post-surgical fresh frozen tissues. The HIF-1α and FAP expression were associated with serum AFP, TNM, tumor size and vascular invasion. Cox regression analysis showed that HIF-1α/ FAP combination were the independent predictor for overall survival (OS) and time-to-recurrence (TTR) in post-surgical HCC patients. Kaplan-Meier analyses revealed that the patient with high levels of HIF-1α, FAP and combined HIF-1α/FAP had the shortest OS and TTR. In-vitro experiments showed that FAP was increased in hypoxic HCC cancer cell lines in parallel with that of HIF-1α and three EMT markers (E-cadherin, Snail and TWIST). In conclusion, the up-regulation of FAP in HCC cancer cells under hypoxia can be indicative of poor prognosis in patients.

Keywords: Hepatocellular carcinoma (HCC), prognosis, Fibroblast activation protein (FAP), hypoxia inducible factor 1α (HIF-1α)

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How to cite this article:
Zou B, Liu X, Zhang B, Gong Y, Cai C, Li P, Chen J, Xing S, Chen J, Peng S, Pokhrel B, Ding L, Zeng L, Li J. The Expression of FAP in Hepatocellular Carcinoma Cells is Induced by Hypoxia and Correlates with Poor Clinical Outcomes. J Cancer 2018; 9(18):3278-3286. doi:10.7150/jca.25775. Available from http://www.jcancer.org/v09p3278.htm