Cyclin D1 expression is induced by viral BARF1 and is overexpressed in EBV-associated gastric cancer

Abstract

Approximately 10% of gastric carcinomas (GC) worldwide are associated with Epstein-Barr virus (EBV). GC is one of the most frequent human malignancies associated with EBV. The latent expression of the EBV-oncogene BARF1 is restricted to epithelial malignancies. To investigate the underlying BARF1-related mechanisms of oncogenic epithelial transformation, we analyzed gene expression profiles of a BARF1-transfected epithelial (HaCaT+) and the corresponding BARF1-negative (HaCaT-) cell line by cDNA microarray analysis. Real-time PCR was performed to confirm the cDNA microarray results. In addition, immunohistochemistry and fluorescence in situ hybridization were performed on a tissue microarray of 181 GC including 11 EBV-associated GC. Among other genes cyclin D1 expression was significantly upregulated in HaCaT+ on the transcriptional and protein level. Cyclin D1 protein expression in GC revealed a significant overexpression of cyclin D1 in EBV-associated GC (p<0.012) but not in EBV-negative GC. Cyclin D1 FISH showed that cyclin D1 overexpression was not due to gene amplification in EBV-associated GC. Cyclin D1 is induced in HaCaT+ by BARF1 and is overexpressed in EBV-associated GC indicating an interaction of viral BARF1 and cyclin D1.

Analysis of cell cycle-related proteins in gastric intramucosal differentiated-type cancers based on mucin phenotypes: a novel hypothesis of early gastric carcinogenesis based on mucin phenotype

“…However, although the differences did not reach a significant level, the frequency of cyclin D1 overexpression was higher in the gastric phenotype than in the intestinal and mixed phenotypes. Cyclin D1 was previously studied in several series of gastric cancers, with a reported frequency of 20~56% of overexpression being reported [27-29], different from our results. As a possible reason for these differences of cyclin D1 overexpression, although early differentiated-type cancers, except for gastric phenotype, do not require an increase of cyclin D1, once the tumor has developed, the tumor cells need a high level of cyclin D1 for tumor progression.…”

Epstein-Barr Virus-Encoded BARF1 Promotes Proliferation of Gastric Carcinoma Cells through Regulation of NF-κB

“…The present study showed an increase in NF-B and cyclin D1 expression in BARF1-expressing cells but not in mock-transfected cells. This is consistent with the results of Wiech et al (40). They reported BARF1-induced cyclin D1 upregulation in gastric carcinoma, citing our previous data that cyclin D1 immunostaining was more frequently positive in EBV-positive gastric carcinomas than in EBV-negative gastric carcinomas (9).…”

Expression of BamHI-A Rightward Transcripts in Epstein-Barr Virus-Associated Gastric Cancers

“…For example, BARF1, which is exclusively expressed in EBV-associated GCs, has oncogenic properties in many cell types such as monkey kidney epithelial cell line [6] and human B lymphocytes [7], and human epithelial cell line HBE [8]. In addition, cyclin D1 induced in BARF1-transfected epithelial cells was overexpressed in EBV-associated GCs, indicating an interaction of viral BARF1 and cyclin D1 [9]. However, BARF1 transcripts have never been shown to produce protein in EBV-positive GCs.…”