Methylation of death-associated protein kinase in ovarian carcinomas

Epigenetic Silencing of DAPK1and p16 INK4a Genes by CpG Island Hypermethylation in Epithelial Ovarian Cancer Patients

Transcriptional silencing induced by hypermethylation of CpG islands in the promoter regions of genes is believed to be an important mechanism of carcinogenesis in human cancers including epithelial ovarian cancer (EOC). Previously published data on gene methylation of EOC focused mainly on single gene or on cancer tissues. Objectives of the study were to estimate the promoter hypermethylation status of DAPK1 and p16 ^INK4a genes in circulating blood of EOC patients and to determine their association with clinicopathological features of EOC. This case-control study included 50 EOC patients and 20 apparently healthy and age matched female controls. Isolation of genomic DNA was carried out from peripheral venous blood. Methylation in promoter region of DAPK1 and p16 ^INK4a genes was determined by methylation-specific PCR. Methylation of DAPK1 was occurred in 42 out of 50 cases (84.0%) and methylation of p16 ^INK4a gene was occurred in 34 out of 50 cases (68.0%). Methylation of both genes was occurred in 25 cases (50.0%). Occurrence of methylation in DAPK1 and p16 ^INK4a genes was statistically significant (p < 0.0001) in cases compared to controls. Methylation of both genes was not statistically associated with age at diagnosis, menopausal status, histopathological types and FIGO staging of EOC. Identification of the peculiar promoter hypermethylation of DAPK1 and p16 ^INK4a genes might be a successful approach for ancillary diagnosis of EOC at early stage in blood sample.

Big data-based identification of methylated genes associated with drug resistance and prognosis in ovarian cancer

It is imperative to further the understanding of the drug resistance mechanisms of ovarian cancer (OC) and to identify useful biological markers for prognosis prediction.Cormine, cBioportal, and The Cancer Genome Atlas databases were used to search microarray data of gene methylation related to OC, drug resistance in OC, and prognosis, and to analyze methylated genes potentially inducing the drug resistance in OC. Fifty-five DNA-methylated genes significantly associated with drug resistance in OC were screened, and the regulatory mechanisms underlying changes in methylation levels of these genes were systematically integrated.Enrichment and annotation of biological processes indicated that most of the above DNA-methylated genes were significantly associated with cell proliferation and cell cycle. In addition, pathway enrichment demonstrated that the above DNA-methylated genes were significantly associated with PI3K-AKT and P53 signaling pathways. Among the 55 genes, 4 were significantly associated with OC prognostic disease-free survival, namely bromodomain containing 4, PDZ domain containing 1 (PDZK1), phosphatase and tensin homolog, and TNF receptor superfamily member 10c; 5 were significantly related to overall survival, namely bromodomain containing 4, PDZK1, PIK3C2B, Rh associated glycoprotein, and DYRK; among them, the degree of methylation of TNF receptor superfamily member 10c, PDZK1, and Rh associated glycoprotein genes was significantly correlated with mRNA expression. Furthermore, PDZK1, Rh associated glycoprotein, and TNF receptor superfamily member 10c genes showed significant hypomethylation in drug-resistance tissues of OC, and their mRNAs had significantly high expression.The association between the methylation of these 55 genes and OC and drug resistance in OC, in addition to bioinformatics analyses clarify the important mechanisms of gene methylation in the development, progression, and drug resistance of OC.

Epigenetic Biomarkers in the Management of Ovarian Cancer: Current Prospectives

Ovarian cancer (OC) causes significant morbidity and mortality as neither detection nor screening of OC is currently feasible at an early stage. Difficulty to promptly diagnose OC in its early stage remains challenging due to non-specific symptoms in the early-stage of the disease, their presentation at an advanced stage and poor survival. Therefore, improved detection methods are urgently needed. In this article, we summarize the potential clinical utility of epigenetic signatures like DNA methylation, histone modifications, and microRNA dysregulation, which play important role in ovarian carcinogenesis and discuss its application in development of diagnostic, prognostic, and predictive biomarkers. Molecular characterization of epigenetic modification (methylation) in circulating cell free tumor DNA in body fluids offers novel, non-invasive approach for identification of potential promising cancer biomarkers, which can be performed at multiple time points and probably better reflects the prevailing molecular profile of cancer. Current status of epigenetic research in diagnosis of early OC and its management are discussed here with main focus on potential diagnostic biomarkers in tissue and body fluids. Rapid and point of care diagnostic applications of DNA methylation in liquid biopsy has been precluded as a result of cumbersome sample preparation with complicated conventional methods of isolation. New technologies which allow rapid identification of methylation signatures directly from blood will facilitate sample-to answer solutions thereby enabling next-generation point of care molecular diagnostics. To date, not a single epigenetic biomarker which could accurately detect ovarian cancer at an early stage in either tissue or body fluid has been reported. Taken together, the methodological drawbacks, heterogeneity associated with ovarian cancer and non-validation of the clinical utility of reported potential biomarkers in larger ovarian cancer populations has impeded the transition of epigenetic biomarkers from lab to clinical settings. Until addressed, clinical implementation as a diagnostic measure is a far way to go.

Ser289 phosphorylation activates both DAPK1 and DAPK2 but in response to different intracellular signaling pathways

DAPK1 and DAPK2 are calmodulin (CaM)-regulated protein kinases that share a high degree of homology in their catalytic and CaM regulatory domains. Both kinases function as tumor suppressors, and both have been implicated in autophagy regulation. Over the years, common regulatory mechanisms for the two kinases as well as kinase-specific ones have been identified. In a recent work, we revealed that DAPK2 is phosphorylated on Ser289 by the metabolic sensor AMPK, and that this phosphorylation enhances DAPK2 catalytic activity. Notably, Ser289 is conserved between DAPK1 and DAPK2, and was previously found to be phosphorylated in DAPK1 by RSK. Intriguingly, Ser289 phosphorylation was conversely reported to inhibit the pro-apoptotic activity of DAPK1 in cells. However, as the direct effect of this phosphorylation on DAPK1 catalytic activity was not tested, indirect effects were not excluded. Here, we compared Ser289 phosphorylation of the two kinases in the same cells and found that the intracellular signaling pathways that lead to Ser289 phosphorylation are mutually-exclusive and different for each kinase. In addition, we found that Ser289 phosphorylation in fact enhances DAPK1 catalytic activity, similar to the effect on DAPK2. Thus, Ser289 phosphorylation activates both DAPK1 and DAPK2, but in response to different intracellular signaling pathways.

Epigenomics and ovarian carcinoma

Ovarian cancer is the leading cause of death among gynecological cancers. It is now recognized that in addition to genetic alterations, epigenetic mechanisms, such as DNA methylation, histone modifications and nucleosome remodeling, play an important role in the development and progression of ovarian cancer by modulating chromatin structure, and gene and miRNA expression. Furthermore, epigenetic alterations have been recognized as useful tools for the development of novel biomarkers for diagnosis, prognosis, therapeutic prediction and monitoring of diseases. Moreover, new epigenetic therapies, such as DNA methyltransferase inhibitors and histone deacetylase inhibitors, have been found to be a potential therapeutic option, especially when used in combination with other agents. Here we discuss current developments in ovarian carcinoma epigenome research, the importance of the ovarian carcinoma epigenome for development of diagnostic and prognostic biomarkers, and the current epigenetic therapies used in ovarian cancer.

Regulation of death-associated protein kinase. Stabilization by HSP90 heterocomplexes

Death-associated protein kinase (DAPK) has been found associated with HSP90, and inhibition of HSP90 with 17-alkylamino-17-demethoxygeldanamycin reduced expression of DAPK. These results were extended to determine whether the degradation of DAPK in the absence of HSP90 activity is dependent on the ubiquitin-proteasome pathway. Our results show that treatment of cells with geldanamycin (GA) leads to degradation of DAPK, and this degradation is attenuated by the proteasome inhibitor, lactacystin. GA-induced DAPK degradation is also dependent on phosphorylation of DAPK at Ser(308), and the cellular levels of phospho(Ser(308))-DAPK dramatically increase in response to GA treatment. Expression of two distinct ubiquitin E3 ligases, carboxyl terminus of HSC70-interacting protein (CHIP) or DIP1/Mib1, enhanced DAPK degradation, and conversely, short interfering RNA depletion of either CHIP or DIP1/Mib1 attenuated DAPK degradation. In vitro ubiquitination assays confirmed that DAPK is targeted for ubiquitination by both CHIP and DIP. Consistent with these results, DAPK is found in two distinct immune complexes, one containing HSP90 and CHIP and a second complex containing only DIP1/Mib. Collectively, these results indicate that strict modulation of DAPK activities is critical for regulation of apoptosis and cellular homeostasis.