Jianxiang Chen1,2, Muthukumar Rajasekaran1, Hongping Xia1, Xiaoqian Zhang2, Shiknie Kong1, Karthik Sekar1, Veerabrahma Pratap Seshachalam1, Amudha Deivasigamani1, Brian Goh Kim Poh1, London Lucien Ooi1, Wanjin Hong2 and Kam M. Hui1,2,3,5
1 Laboratory of Cancer Genomics, Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre, Singapore, Singapore;
2 Institute of Molecular and Cell Biology, A*STAR, Biopolis Drive Proteos, Singapore, Singapore;
3 Cancer and Stem Cell Biology Program, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore;
4 Division of Surgery, Singapore General Hospital, Singapore;
5 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Published Online in Gut on 3 March 2016.
Objectives: Hepatocellular carcinoma (HCC) is the second leading cause of cancer mortality worldwide. Alterations in microtubule-associated proteins (MAPs) have been observed in HCC. However, the mechanisms underlying these alterations remain poorly understood. Our aim was to study the roles of the MAP protein regulator of cytokinesis 1 (PRC1) in hepatocarcinogenesis and early HCC recurrence.
Design: PRC1 expression in HCC samples was evaluated by microarray, immunoblotting and immunohistochemistry analysis. Molecular and cellular techniques including siRNA- and lentiviral vector-mediated knockdown were used to elucidate the functions and mechanisms of PRC1.
Results: PRC1 expression was associated with early HCC recurrence and poor patient outcome. In HCC, PRC1 exerted an oncogenic effect by promoting cancer proliferation, stemness, metastasis and tumourigenesis. We further demonstrated that the expression and distribution of PRC1 is dynamically regulated by Wnt3a signalling. PRC1 knockdown impaired TCF transcriptional activity, decreased Wnt target expression, and reduced nuclear β-catenin levels. Mechanistically, PRC1 interacts with the β-catenin destruction complex, regulates Wnt3a-induced membrane sequestration of this destruction complex, inhibits APC stability and promotes β-catenin release from the APC complex. In vivo, high PRC1 expression correlated with nuclear β-catenin and Wnt target expression. PRC1 acted as a master regulator of a set of 48 previously identified Wnt-regulated recurrence-associated genes (WRRAGs) in HCC. Thus, PRC1 controlled the expression and function of WRRAGs such as FANCI, SPC25, KIF11 and KIF23 via Wnt signalling.
Conclusions: We identified PRC1 as a novel Wnt target that functions in a positive feedback loop that reinforces Wnt signalling to promote early HCC recurrence.
A proposed working model of PRC1 functions in the Wnt pathway in HCC. Wnt3a signalling induces the expression and microtubule (MT) enrichment of PRC1, which can promote the membrane sequestration of the destruction complex, suppress APC stability, accelerate active β-catenin release from the APC complex, and promote HCC metastasis and proliferation.
For more information on Wanjin HONG's lab, please click here.
For more information on Kam Man HUI's lab, please click here.