Epigenetic silencing of the imprinted gene ZAC by DNA methylation is an early event in the progression of human ovarian cancer

Abstract

ZAC is a paternally expressed, imprinted gene located on chromosome 6q24, within a region known to harbor a tumor suppressor gene for several types of neoplasia, including human ovarian cancer (HOC). We have failed to identify genetic mutations in the ZAC gene in tumor material. Many imprinted genes contain differentially allele-specific-methylated regions (DMR) and harbor promoter activity that is regulated by the DNA methylation. Aberrant DNA methylation is a common feature of neoplasia and changes in DNA methylation at the ZAC locus have been reported in some cases of HOC. We investigated the DNA methylation and ZAC mRNA expression levels in a larger sample of primary HOC material, obtained by laser capture microdissection. ZAC mRNA expression was reduced in the majority of samples and this correlated with hypermethylation of the ZAC-DMR. Treatment of hypermethylated cells lines with a demethylating agent restored ZAC expression. Our studies indicate that transcriptional silencing of ZAC is likely to be caused by DNA methylation in HOC. Forced expression of ZAC resulted in a reduction in proliferation and marked induction of apoptotic cell death. The ZAC-mediated apoptosis signal is p53-independent and eliminated by inhibitors of caspase 3, 8 and 9. Reduced expression of ZAC would therefore favor tumor progression. As there were no significant differences in either DNA methylation or expression of ZAC mRNA between localized and advanced tumors, our data indicates that loss of ZAC is a relatively early event in HOC. (Supplementary material for this article can be found on the International Journal of Cancer website at

Modulation of the Cyclin-Dependent Kinase Inhibitor p21WAF1/Cip1 Gene by Zac1 through the Antagonistic Regulators p53 and Histone Deacetylase 1 in HeLa Cells

“…The combined treatment of the demethylating agent 5-aza-2 ¶-deoxycyticidine and TSA increased by 2-fold to 3-fold of Zac1 mRNA expression in HOC cell lines (39). In this study, the simple increase in the amount of Zac1 DNA transfected could not elicit the same effect as TSA on Zac1's coactivator and transactivation functions in HeLa cells.…”

Epigenetics and imprinting in human disease

“…1 (Azzi et al, 2014); 2 (Cassidy et al, 2012, Mabb et al, 2011; 3 (Ankolkar et al, 2013, Docherty et al, 2010, Iglesias-Platas et al, 2013, Kamikihara et al, 2005; 4 (Lecumberri et al, 2010, Linglart et al, 2013, Turan and Bastepe, 2013; 5 (Huang et al, 2007, Jorgensen et al, 2013, Kawakami et al, 2006, Sutton and Shaffer, 2000; 6 (Dowdy et al, 2005, Trouillard et al, 2004, Van den Veyver et al, 2001; 7 (Gao et al, 2010, Tsou et al, 2003; 8 (Kobayashi et al, 1997, Lee andBartolomei, 2013); 9 (Hysi et al, 2010, Takamaru et al, 2012, Tarnowski et al, 2012, Zhu et al, 2013 methylation and biallelic expression of imprinted genes (Kaneda et al, 2004). Through the use of the de novo DNA methyltransferases DNMT3A and DNMT3B and the accessory protein DNMT3L, ICRs and DMRs are specifically methylated in the male or female germline (Bartolomei and Ferguson-Smith, 2011).…”

A Novel 19q13 Nucleolar Zinc Finger Protein Suppresses Tumor Cell Growth through Inhibiting Ribosome Biogenesis and Inducing Apoptosis but Is Frequently Silenced in Multiple Carcinomas

“…Some ZFPs function as oncogenic proteins such as ZNF217 and ZNF639 (1,2), whereas others can act as tumor suppressors, such as ZAC, ST18, and ZNF382 (3)(4)(5). ZFPs bind to promoters with their zinc finger domains and activate or repress gene expression through their association proteins (1,6).…”

“…Several ZFPs including ZAC, ST18, and ZNF382, had been reported as tumor suppressors and frequently inactivated by CpG methylation in human cancers (3)(4)(5). It is well known that the aberrant inactivation of negative mediators of cell proliferation, such as tumor suppressor genes (TSG), through promoter methylation, is frequently involved in multiple tumorigenesis (9).…”