Identification of guanine nucleotide-binding protein gamma-7 as an epigenetically silenced gene in head and neck cancer by gene expression profiling


Demokan S., Chuang A. Y., Chang X., Khan T., Smith I. M., Pattani K. M., ...More

INTERNATIONAL JOURNAL OF ONCOLOGY, vol.42, no.4, pp.1427-1436, 2013 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 42 Issue: 4
  • Publication Date: 2013
  • Doi Number: 10.3892/ijo.2013.1808
  • Journal Name: INTERNATIONAL JOURNAL OF ONCOLOGY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1427-1436
  • Keywords: guanine nucleotide-binding protein gamma-7, gene expression, silencing, head and neck squamous cell carcinoma, epigenetics, HOMOZYGOUS DELETION REGION, SQUAMOUS-CELL CARCINOMA, TUMOR-SUPPRESSOR GENES, LUNG-CANCER, PROMOTER HYPERMETHYLATION, DNA METHYLATION, FUS1 PROTEIN, GROWTH, THIOREDOXIN, MECHANISMS
  • Istanbul University Affiliated: Yes

Abstract

Silencing of tumor suppressor genes plays a vital role in head and neck carcinogenesis. Aberrant hypermethylation in the promoter region of some known or putative tumor suppressor genes occurs frequently during the development of various types of cancer including head and neck squamous cell carcinoma (HNSCC). In this study we used an expanded mRNA expression profiling approach followed by microarray expression analysis to identify epigenetically inactivated genes in HNSCC. Two HNSCC cell lines were treated with 5-aza-2'-deoxycytidine followed by microarray analysis to identify epigenetically silenced genes in HNSCC. We found 1,960, 614 and 427 genes were upregulated in the HNSCC cell lines JHU-012, JHU-011 and the combination of both cell lines, respectively. HNSCC tumor and normal mucosal samples were used for gene profiling by a 47K mRNA gene expression array and we found 7,140 genes were downregulated in HNSCC tumors compared to normal mucosa, as determined by microarray analysis, and were integrated with cell line data. Integrative analysis defined 126 candidate genes, of which only seven genes showed differential methylation in tumors and no methylation in normal mucosa after bisulfite sequencing. Following validation by QMSP, one gene, guanine nucleotide-binding protein gamma-7 (GNG7), was confirmed to be highly methylated in tumors and unmethylated in normal mucosal and salivary rinse samples demonstrating cancer-specific methylation in HNSCC tissues. TXNIP and TUSC2 were partially methylated in tumors and normal salivary rinses but unmethylated in normal mucosa. We concluded that GNG7 is a highly specific promoter methylated gene associated with HNSCC. In addition, TXNIP and TUSC2 are also potential biomarkers for HNSCC.