Characterization of the GNMT-HectH9-PREX2 tripartite relationship in the pathogenesis of hepatocellular carcinoma

Chung-Hsien Li; Chia-Hung Yen; Yen-Fu Chen; Kuo-Jui Lee; Cheng-Chieh Fang; Xian Zhang; Chih-Chung Lai; Shiu-Feng Huang; Hui-Kuan Lin; Yi-Ming Arthur Chen

doi:10.1002/ijc.30652

Characterization of the GNMT-HectH9-PREX2 tripartite relationship in the pathogenesis of hepatocellular carcinoma

Int J Cancer. 2017 May 15;140(10):2284-2297. doi: 10.1002/ijc.30652.

Authors

Chung-Hsien Li¹, Chia-Hung Yen^{1

2}, Yen-Fu Chen¹, Kuo-Jui Lee¹, Cheng-Chieh Fang¹, Xian Zhang³, Chih-Chung Lai¹, Shiu-Feng Huang⁴, Hui-Kuan Lin³, Yi-Ming Arthur Chen^{1

5

6}

Affiliations

¹ Center for Infectious Disease and Cancer Research (CICAR), Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
² Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
³ Department of Cancer Biology, Wake Forest Cancer Center, Wake Forest University, Winston-Salem, NC.
⁴ Division of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, 35053, Taiwan.
⁵ Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
⁶ Institute of Biomedical Sciences, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan.

PMID: 28205209
DOI: 10.1002/ijc.30652

Abstract

The pathogenesis of hepatocellular carcinoma (HCC) involves many molecular pathways. Glycine N-methyltransferase (GNMT) is downregulated in almost all HCC and its gene knockout mice developed HCC with high penetrance. We identified PREX2, a novel PTEN inhibitor, as a GNMT-interacting protein. Such interaction enhanced degradation of PREX2 through an E3 ligase HectH9-mediated proteasomal ubiquitination pathway. Depletion of GNMT or HectH9 resulted in AKT activation in a PREX2 dependent manner and enhanced cell proliferation. An elevated PREX2 protein expression accompanied by activation of AKT was observed in the liver of Gnmt knockout mice. PREX2 protein expression was upregulated in 54.9% of human HCC samples, while its mRNA level was comparable in tumor and tumor-adjacent tissue, suggesting a post-translational alteration of PREX2 expression. Higher level of PREX2 in the tumor tissues was associated with poorer survival. These results reveal a novel mechanism in which GNMT participates in AKT signaling and HCC tumorigenesis by promoting HectH9-mediated PREX2 degradation.

Keywords: GNMT; HCC; HectH9; PREX2.

MeSH terms

Animals
Apoptosis
Biomarkers, Tumor / genetics
Biomarkers, Tumor / metabolism*
Blotting, Western
Carcinoma, Hepatocellular / genetics
Carcinoma, Hepatocellular / metabolism
Carcinoma, Hepatocellular / pathology*
Cell Proliferation
Cell Transformation, Neoplastic / genetics
Cell Transformation, Neoplastic / metabolism
Cell Transformation, Neoplastic / pathology*
Female
Follow-Up Studies
Glycine N-Methyltransferase / genetics
Glycine N-Methyltransferase / metabolism*
Guanine Nucleotide Exchange Factors / genetics
Guanine Nucleotide Exchange Factors / metabolism*
Humans
Immunoenzyme Techniques
Immunoprecipitation
Liver Neoplasms / genetics
Liver Neoplasms / metabolism
Liver Neoplasms / pathology*
Male
Mice
Mice, Inbred NOD
Mice, Knockout
Mice, SCID
Middle Aged
Neoplasm Staging
PTEN Phosphohydrolase / genetics
PTEN Phosphohydrolase / metabolism
Prognosis
Proto-Oncogene Proteins c-akt / genetics
Proto-Oncogene Proteins c-akt / metabolism
RNA, Messenger / genetics
Real-Time Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction
Survival Rate
Tumor Cells, Cultured
Tumor Suppressor Proteins
Ubiquitin-Protein Ligases / genetics
Ubiquitin-Protein Ligases / metabolism*
Ubiquitination
Xenograft Model Antitumor Assays

Substances

Biomarkers, Tumor
Guanine Nucleotide Exchange Factors
PREX2 protein, human
RNA, Messenger
Tumor Suppressor Proteins
GNMT protein, human
Glycine N-Methyltransferase
HUWE1 protein, human
Ubiquitin-Protein Ligases
Proto-Oncogene Proteins c-akt
PTEN Phosphohydrolase
PTEN protein, human