REC8 functions as a tumor suppressor and is epigenetically downregulated in gastric cancer, especially in EBV-positive subtype

Abstract

REC8 meiotic recombination protein (REC8) was found to be preferentially methylated in gastric cancer (GC) using promoter methylation array. We aimed to elucidate the epigenetic alteration and biological function of REC8 in GC. REC8 was downregulated in 100% (3/3) of Epstein–Barr virus (EBV)-positive and 80% (8/10) of EBV-negative GC cell lines by promoter methylation, but the expression could be restored through demethylation treatment. Protein expression of REC8 was significantly lower in human primary gastric tumors than in adjacent non-tumor tissues. A negative correlation between methylation and mRNA expression of REC8 was observed in 223 gastric samples of The Cancer Genome Atlas study (r=−0.7018, P<0.001). The methylation level (%) of the REC8 promoter was significantly higher in EBV-positive gastric tumors than in EBV-negative gastric tumors, as shown by bisulfite genomic sequencing (77.6 (69.3–80.5) vs 51.4 (39.5–62.3), median (interquartile range); P<0.001); methylation levels in both subtypes of tumors were significantly higher than in normal stomach tissues (14.8 (4.2–24.0)) (both P<0.001). Multivariate analysis revealed that REC8 methylation was an independent factor for poor survival in GC patients (hazard ratio=1.68, P<0.05). REC8 expression significantly suppressed cell viability, clonogenicity and cell cycle progression; it induced apoptosis and inhibited migration of AGS-EBV (EBV-positive) and BGC823 (EBV-negative) GC cells, and it suppressed tumorigenicity in nude mice. In contrast, knockdown of REC8 in gastric epithelial immortalized GES-1 cells significantly increased cell viability, clonogenicity and migration ability. The tumor-suppressive effect of REC8 is mediated at least in part by the downregulation of genes involved in cell growth (G6PD, SLC2A1, NOL3, MCM2, SNAI1 and SNAI2), and the upregulation of apoptosis/migration inhibitors (GADD45G and LDHA) and tumor suppressors (PinX1, IGFBP3 and ETS2). In conclusion, REC8 is a novel tumor suppressor that is commonly downregulated by promoter methylation in GC, especially in the EBV-associated subtype. Promoter methylation of REC8 is an independent risk factor for the shortened survival of GC patients.

Regulatory network analysis of LINC00472, a long noncoding RNA downregulated by DNA hypermethylation in colorectal cancer

“…DNA methylation‐mediated silencing of tumor suppressor genes has been shown to be an important mechanism of tumorigenesis . For example, tumor suppressor meiotic recombination protein 8 ( REC8 ) was commonly downregulated by promoter methylation in gastric cancer (GC), and increasing methylation of REC8 was an independent risk factor for shortened survival in GC patients . Besides, a series of studies utilizing the high‐throughput technologies such as MethylCap‐Seq, MBD‐Seq and so on, were carried out in CRC.…”

“…15 For example, tumor suppressor meiotic recombination protein 8 (REC8) was commonly downregulated by promoter methylation in gastric cancer (GC), and increasing methylation of REC8 was an independent risk factor for shortened survival in GC patients. 16 Besides, a series of studies utilizing the high-throughput technologies such as MethylCap-Seq, MBD-Seq and so on, were carried out in CRC. For example, a MethylCap-Seq dataset about CRC was reported previously, which identified 2687 frequently hypermethylated and 468 frequently hypomethylated regions associated with CRC.…”

Gastric cancer: genome damaged by bugs

“…Besides, a resistance factor against DNA methylation namely TET2 was suppressed to contribute to DNA methylation acquisition during EBV infection [144]. Variety of tumor-suppressor genes have been identified to be methylated during EBV infection, such as p16, p14, APC, SSTR1, FHIT, CRBP1, WWOX, DLC-1, AQP3, REC8, TP73, BLU, FSD1, BCL7A, MARK1, SCRN1, and NKX3.1 [129,[145][146][147][148][149][150][151]. The developed high-throughput sequencing makes it possible to reveal the EBV-induced DNA hypermethylation comprehensively.…”

Network-based Approach to Identify Prognosis-related Genes in Tamoxifen-treated Patients With Estrogen Receptor-positive Breast Cancer

“…Moreover, Liu et al reported that REC8 is aberrantly methylated and robustly regulated by the phosphoinositide-3 kinase pathway in thyroid cancer [37]. The tumor-suppressive role of REC8 in gastric carcinogenesis is mediated by important genes implicated in the regulation of the cell cycle, proliferation, migration, and apoptosis [39].…”