Abstract
Tumor Necrosis Factor Receptor-Associated Protein 1 (TRAP1) is a heat shock protein 90 (HSP90) molecular chaperone overexpressed in 60–70% human colorectal carcinomas (CRCs) and the co-upregulation of TRAP1 and associated 6-related proteins identifies metastatic CRCs with poor prognosis. Since the molecular mechanisms responsible for TRAP1 regulation are still unknown, the significance of TRAP1 gene copy number (CN) and the role of post-transductional protein modifications were addressed. TRAP1 gene aneuploidy accounted for 34.5% of cases in a cohort of 58 human CRCs and TRAP1 CN correlated with its mRNA and protein expression, suggesting that transcriptional mechanisms are responsible for TRAP1 upregulation. Furthermore, the analysis of the National Cancer Institute’s Clinical Proteomic Tumor Analysis Consortium/The Cancer Genome Atlas (CPTAC/TCGA) CRC database showed that TRAP1 polysomy significantly correlates with lymph node involvement. However, a subgroup of tumors showed TRAP1 protein levels independent from its CN. Of note, a direct correlation was observed between TRAP1 protein levels and the expression of S-nitrosoglutathione reductase (GSNOR), a denitrosylase involved in the regulation of protein S-nitrosylation. Furthermore, CRC cell lines exposed to hypoxia or dichloroacetate treatment showed the downregulation of TRAP1 upon GSNOR silencing and this resulted in increased TRAP1 mono/polyubiquitination. These data suggest that transcriptional and post-transductional mechanisms account for TRAP1 expression in human CRCs and GSNOR protects TRAP1 from S-nitrosylation and consequent proteasome degradation mostly in conditions of stress.
Highlights
Colorectal carcinoma (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide [1]
The analysis of The Cancer Genome Atlas (TCGA) database showed that the majority of human CRCs are characterized by a diploid Tumor Necrosis Factor Receptor-Associated Protein 1 (TRAP1) genotype, with a subgroup characterized by gain or loss in TRAP1 copy number (CN) [5], this suggesting that TRAP1 expression may depend on transcriptional mechanisms
In order to establish whether TRAP1 expression in human CRCs depends on gene CN variation, TRAP1 CN was analyzed in a cohort of 58 human CRCs at different Tumor, Nodes, Metastasis (TNM) stages (Table 1)
Summary
Colorectal carcinoma (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide [1]. We recently reported a TRAP1 signature based on the co-upregulation of TRAP1 and associated 6-client/related proteins (i.e., eukaryotic initiation factor 2 subunit Alpha (IF2α), eukaryotic translation elongation factor 1 Alpha (eF1A), proteasome regulatory particle TBP7/Rpt (TBP7), mitotic arrest deficient 2 (MAD2), cyclin-dependent kinase 1 (CDK1) and β-Catenin) that identifies a cohort of metastatic CRCs with a significantly shorter overall survival [5]. In such a context, a major issue is the understanding of the molecular mechanism responsible for TRAP1 upregulation in human malignancies.
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