Polycomb chromobox 4 enhances migration and pulmonary metastasis of hepatocellular carcinoma cell line MHCC97L.

Zhu Mei,Ying Xu,Huike Jiao,Jie Li,Guoqiang Chen,Wei Wang

doi:10.1007/s11427-014-4663-9

Abstract

We recently report that the expression of polycomb chromobox 4 (Cbx4) is significantly correlated with the overall survival of a great cohort of hepatocellular carcinoma (HCC) patients and it enhances hypoxia-induced vascular endothelial growth factor (VEGF) expression and angiogenesis in HCC cells through enhancing sumoylation of hypoxia inducible factor-1alpha (HIF-1α). Here we continue to investigate the potential effects of Cbx4 on the migration and metastasis of the metastatic HCC cell line MHCC97L. Our results show that Cbx4 overexpression in the cell line increases the in vitro vessel formation of vascular endothelial cells in its SUMO interaction motifs-dependent manner, and promotes the in vitro migration of the cancer cell, which can be effectively abrogated by anti-VEGF antibody. Although Cbx4 expression does not impact the in vitro growth of MHCC97L cells, it still promotes the progression and metastasis of orthotopically transplanted tumors in nude mice. These results further support the role of Cbx4 as a SUMO E3 ligase in the progression and metastasis of HCC.

Highlights

Polycomb group proteins (PcG), a set of transcriptional repressors which impose the histone H3 lysine 27 tri-methylation for repression of gene expression [1,2], assemble into at least two major classes of multimeric protein polycomb repressive complexes (PRC) in mammal, that is, PRC1 and PRC2
We recently report that the expression of polycomb chromobox 4 (Cbx4) is significantly correlated with the overall survival of a great cohort of hepatocellular carcinoma (HCC) patients and it enhances hypoxia-induced vascular endothelial growth factor (VEGF) expression and angiogenesis in HCC cells through enhancing sumoylation of hypoxia inducible factor-1alpha (HIF-1α)
We detected whether Cbx4 affects the in vitro vessel formation in the co-culture system of HUVEC and MHCC97L cells with or without ectopic stable expression of Flag-tagged wildtype Cbx4 (Cbx4-WT), Cbx4-CDM or Cbx4- SIM1/2 (Figure 1A), in which Cbx4-CDM mutant carries F11A/ W35L double-mutation in its chromodomain of Cbx4 and loses its polycomb function but still presents small ubiquitin-related modifier (SUMO) E3 ligase activity, while Cbx4- SIM1/2 mutant is absent of their two SIMs and lose SUMO E3 ligase activity [17]

Summary

Introduction

Polycomb group proteins (PcG), a set of transcriptional repressors which impose the histone H3 lysine 27 tri-methylation for repression of gene expression [1,2], assemble into at least two major classes of multimeric protein polycomb repressive complexes (PRC) in mammal, that is, PRC1 and PRC2. They are essential for embryonic development and stem cell renewal and contribute widely to a series of biological processes such as cell cycle, DNA repair, cell differentiation, senescence and death [1,3 5]. We continue to investigate the potential effects of Cbx on the migration and metastasis of MHCC97L, a metastatic HCC cell line [19]

Methods

Results

Conclusion