Aberrant Hypermethylation of Non-Promoter Zygote Arrest 1 (Zar1) in Human Brain Tumors

Abstract

Zygote arrest 1 (ZAR1) is a novel maternal-effect gene which is extremely important during the oocyteto-embryo transition. Comprehensive methylation analysis of tumor-specific differentially methylated regions in human malignant melanoma has recently led to the identification of non-promoter hypermethylation of the ZAR1 gene that had never been previously linked to aberrant methylation. Strikingly, ZAR1 hypermethylation was frequently observed in melanomas but was absent in benign nevi, and ZAR1 expression was found to be up-regulated in methylated tumors. The present study searched for non-promoter ZAR1 hypermethylation in 90 primary human brain tumor samples, normal brain tissue from one autopsy case, and 7 glioma cell lines, employing Sequenom MassARRAY, in which bisulfitetreated fragments are quantitatively detected using time-of-flight mass spectroscopy. ZAR1 transcript expression levels were also evaluated by quantitative real-time reverse transcription-polymerase chain reaction in the 7 glioma cell lines. Hypermethylation of ZAR1 was frequently found in diffuse astrocytomas (7/7, 100%), anaplastic astrocytomas (16/17, 94%), glioblastomas (27/29, 93%), oligodendrogliomas (3/3, 100%), anaplastic oligodendrogliomas (3/3, 100%), and pituitary adenomas (9/10, 90%), but not in pilocytic astrocytomas (0/3). Other tumor types showed infrequent ZAR1 hypermethylation: 1 (17%) of 6 vestibular schwannomas and 4 (33%) of 12 meningothelial meningiomas. The normal brain tissue revealed no evidence of ZAR1 methylation. All 7 glioma cell lines displayed aberrant hypermethylation of ZAR1, but none had detectable ZAR1 transcript. Our findings indicate that non-promoter hypermethylation of ZAR1 is extremely frequent in diffuse gliomas and pituitary adenomas, but methylation-related aberrant ZAR1 expression is far less likely to be related to glioma tumorigenesis.

Promoter hypomethylation of RAR-related orphan receptor α 1 is correlated with unfavorable clinicopathological features in patients with colorectal cancer

“…Previously, we performed restriction landmark genomic scanning to identify novel genomic regions of mouse skin tumor-specific differentially methylated regions (DMRs), and found 14 DMRs that were highly conserved between mouse and human (2)(3)(4)(5). Among these, we focused on retinoic acid receptor-related orphan receptor α (RORA), which is frequently downregulated in CRC and is correlated with tumor progression (6).…”

Identification of Frequent Differentially Methylated Region in Sporadic Bladder Cancers

“…The most widely adopted noninvasive urine test is cytology, which has good specificity and sensitivity for the detection of high-grade tumors, but poor sensitivity for low-grade tumors [13] and often takes time to generate results [14]. To discover novel markers that are more specific and sensitive in detecting bladder cancer, we examined the methylation status of ZAR1 , which has been reported to be aberrantly methylated in mouse skin tumors and human tumors such as melanoma, brain tumor, and hepatocellular carcinoma [6,7,8]. …”

“…In these analyses, CpGi in the zygote arrest 1 (ZAR1) exon 1/intron 1 was aberrantly methylated in melanoma, brain tumor, and hepatocellular carcinoma compared with normal tissues [6,7,8]. In particular, in hepatocellular carcinoma, higher methylation levels of ZAR1 exon 1/intron 1 were associated with lower serum albumin levels, which are markers of poor prognosis [8].…”

Identification of novel genomic regions with aberrant cytosine methylation in hematological malignancies

“…Shinojima et al noted a very high frequency of hypermethylation of the ZAR1 intergenic region in human melanomas, in contrast to non-methylation in both normal human epidermal melanocyte cell lines and melanocytic nevus surgical specimens 9) . Watanabe et al reported that hypermethylation of ZAR1 in various types of human brain tumors 25) . Seven candidate aberrantly methylated genomic regions, which have yet to be identified by whole genome scan, were analyzed in this study.…”