Histone methylation in pancreatic cancer and its clinical implications

Pancreatic cancer (PC) is an aggressive human cancer. Appropriate methods for the diagnosis and treatment of PC have not been found at the genetic level, thus making epigenetics a promising research path in studies of PC. Histone methylation is one of the most complicated types of epigenetic modifications and has proved crucial in the development of PC. Histone methylation is a reversible process regulated by readers, writers, and erasers. Some writers and erasers can be recognized as potential biomarkers and candidate therapeutic targets in PC because of their unusual expression in PC cells compared with normal pancreatic cells. Based on the impact that writers have on the development of PC, some inhibitors of writers have been developed. However, few inhibitors of erasers have been developed and put to clinical use. Meanwhile, there is not enough research on the reader domains. Therefore, the study of erasers and readers is still a promising area. This review focuses on the regulatory mechanism of histone methylation, and the diagnosis and chemotherapy of PC based on it. The future of epigenetic modification in PC research is also discussed.

MicroRNA-769-5p Inhibits Pancreatic Ductal Adenocarcinoma Progression by Directly Targeting and Downregulating ETS Proto-Oncogene 1

Purpose

MicroRNA-769-5p (miR-769) is aberrantly expressed and plays crucial roles in non-small cell lung cancer and melanoma. However, the expression pattern, biological role, and mechanisms of action of miR-769 in pancreatic ductal adenocarcinoma (PDAC) are yet to be fully elucidated. Therefore, we attempted to determine the potential regulatory function of miR-769 in PDAC progression and to explore the underlying mechanisms in detail.

Methods

In this study, reverse-transcription quantitative polymerase chain reaction was carried out to determine the expression profile of miR-769 in PDAC. A series of experiments, including a Cell Counting Kit-8 assay, flow-cytometric analysis, Transwell migration and invasion assays, and a xenograft animal model, were applied to test whether miR-769 affects the malignancy of PDAC.

Results

We found that miR-769 was significantly underexpressed in PDAC tissues and cell lines. The low miR-769 expression significantly correlated with the TNM stage and lymph node metastasis. Patients with PDAC harboring low miR-769 expression showed shorter overall survival than did the patients with high miR-769 expression. Forced upregulation of miR-769 suppressed PDAC cell proliferation, migration, and invasion in vitro; promoted apoptosis in vitro; and hindered tumor growth in vivo. Experiments on the mechanism identified ETS proto-oncogene 1 (ETS1) as a direct target gene of miR-769 in PDAC cells. Furthermore, ETS1 turned out to be upregulated in PDAC tissue samples, and the upregulation of ETS1 negatively correlated with miR-769 expression. Moreover, ETS1 knockdown simulated the tumor-suppressive effects of miR-769 overexpression on PDAC cells. Besides, ETS1 reintroduction attenuated the antitumor actions of miR-769 upregulation in PDAC cells.

Conclusion

Our findings indicate that miR-769 performs tumor-suppressive functions in PDAC by directly targeting ETS1, and this miRNA may represent a potential therapeutic target for the development of anticancer therapies.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Epigenetic biomarkers in gastrointestinal cancers: The current state and clinical perspectives

Each year, almost 4.1 million people are diagnosed with gastrointestinal (GI) cancers. Due to late detection of this disease, the mortality is high, causing approximately 3 million cancer-related deaths annually, worldwide. Although the incidence and survival differs according to organ site, earlier detection and improved prognostication have the potential to reduce overall mortality burden from these cancers. Epigenetic changes, including aberrant promoter DNA methylation, are common events in both cancer initiation and progression. Furthermore, such changes may be identified non-invasively with the use of PCR based methods, in bodily fluids of cancer patients. These features make aberrant DNA methylation a promising substrate for the development of disease biomarkers for early detection, prognosis and for predicting response to therapy. In this article, we will provide an update and current clinical perspectives for DNA methylation alterations in patients with colorectal, gastric, pancreatic, liver and esophageal cancers, and discuss their potential role as cancer biomarkers.

Identification of potential target genes in pancreatic ductal adenocarcinoma by bioinformatics analysis

Pancreatic ductal adenocarcinoma (PDAC) is one of the most complicated and fatally pathogenic human malignancies. Therefore, there is an urgent need to improve our understanding of the underlying molecular mechanism that drives the initiation, progression, and metastasis of PDAC. The aim of the present study was to identify the key genes and signaling pathways associated with PDAC using bioinformatics analysis. Four transcriptome microarray datasets (GSE15471, GSE55643, GSE62165 and GSE91035) were acquired from Gene Expression Omnibus datasets, which included 226 PDAC samples and 65 normal pancreatic tissue samples. We screened differentially expressed genes (DEGs) with GEO2R and investigated their biological function by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analysis. The overall survival data was obtained from UALCAN, which calculated the data shared with The Cancer Genome Atlas. In addition, a protein-protein interaction (PPI) network of the DEGs was constructed by STRING and Cytoscape software. The four sets of DEGs exhibited an intersection consisting of 205 genes (142 up-regulated and 63 down-regulated), which may be associated with PDAC. GO analysis showed that the 205 DEGs were significantly enriched in the plasma membrane, cell adhesion molecule activity and the Energy pathways, and glycine, serine, threonine metabolism were the most enriched pathways according to KEGG pathway analysis. Kaplan-Meier survival analysis revealed that 22 of 205 common genes were significantly associated with the overall survival of pancreatic cancer patients. In the PPI network and sub-network, DKK1 and HMGA2 were considered as hub genes with high connectivity degrees. DKK1 and HMGA2 are strongly associated with WNT3A and TP53 separately, which indicates that they may play an important role in the Wnt and P53 signaling pathways. Using integrated bioinformatics analysis, we identified DKK1 and HMGA2 as candidate genes in PDAC, which may improve our understanding of the mechanisms of the pathogenesis and integration; the two genes may be therapeutic targets and prognostic markers for PDAC.

Epigenetic alterations as biomarkers in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) prognosis remains very poor and has only marginally improved during the last decades. Epigenetic alterations have been the focus of many recent studies and offer valuable options for PDAC detection, prognosis and treatment. DNA methylation, histone modifications and microRNA (miR) level changes can be used as biomarkers. These alterations occur early in carcinogenesis and may be specific for PDAC. Additionally, epigenetic alterations can be analyzed from cell-free DNA, free-circulating nucleosomes or shed tumor cells in blood. High-throughput methods are available for miR and DNA methylation level detection. In particular, multiple promising miR level changes have been discovered. No single epigenetic biomarker that offers a sufficient specificity has been discovered yet, but patterns containing multiple independent biomarkers exist.

Aberrant methylation patterns in cancer: a clinical view

Epigenetic mechanisms, such as DNA methylation, DNA hydroxymethylation, post-translational modifications (PTMs) of histone proteins affecting nucleosome remodelling, and regulation by small and large non-coding RNAs (ncRNAs) work in concert with cis and trans acting elements to drive appropriate gene expression. Advances in detection methods and development of dedicated platforms and methylation arrays resulted in an explosion of information on aberrantly methylated sequences linking deviations in epigenetic landscape with the initiation and progression of complex diseases. Here, we consider how DNA methylation changes in malignancies, such as breast, pancreatic, colorectal, and gastric cancer could be exploited for the purpose of developing specific diagnostic tools. DNA methylation changes can be applicable as biomarkers for detection of malignant disease in easily accessible tissues. Methylation signatures are already proving to be an important marker for determination of drug sensitivity. Even more, promoter methylation patterns of some genes, such as MGMT, SHOX2, and SEPT9, have already been translated into commercial clinical assays aiding in patient assessment as adjunct diagnostic tools. In conclusion, the changes in DNA methylation patterns in tumour cells are slowly gaining entrance into routine diagnostic tests as promising biomarkers and as potential therapeutic targets.

Contemporary proteomic strategies for clinical epigenetic research and potential impact for the clinic

Novel proteomic methods are revealing the intricacy of the epigenetic landscape affecting gene regulation and improving our knowledge of the pathogenesis of complex diseases. Despite the enormous amount of data regarding epigenetic modifications present in DNA and histones, deciphering their biological relevance in the context of the disease and health is currently still an ongoing process. Here, we consider the relationship between epigenetic research in tumorigenesis and the prospect of knowledge transfer to clinical use, focusing primarily on the epigenetic histone post-translational modifications, which could be used as biomarkers. We additionally focus on the use of proteomic techniques in research and evaluate their usefulness in clinical setting.

TRIM29 as a novel biomarker in pancreatic adenocarcinoma

Background and Aim. Tripartite motif-containing 29 (TRIM29) is structurally a member of the tripartite motif family of proteins and is involved in diverse human cancers. However, its role in pancreatic cancer remains unclear. Methods. The expression pattern of TRIM29 in pancreatic ductal adenocarcinoma was assessed by immunocytochemistry. Multivariate logistic regression analysis was used to investigate the association between TRIM29 and clinical characteristics. In vitro analyses by scratch wound healing assay and invasion assays were performed using the pancreatic cancer cell lines. Results. Immunohistochemical analysis showed TRIM29 expression in pancreatic cancer tissues was significantly higher  (n = 186) than that in matched adjacent nontumor tissues. TRIM29 protein expression was significantly correlated with lymph node metastasis (P = 0.019). Patients with positive TRIM29 expression showed both shorter overall survival and shorter recurrence-free survival than those with negative TRIM29 expression. Multivariate analysis revealed that TRIM29 was an independent factor for pancreatic cancer over survival (HR = 2.180, 95% CI: 1.324–4.198, P = 0.011). In vitro, TRIM29 knockdown resulted in inhibition of pancreatic cancer cell proliferation, migration, and invasion. Conclusions. Our results indicate that TRIM29 promotes tumor progression and may be a novel prognostic marker for pancreatic ductal adenocarcinoma.

MicroRNA-215 is a potential prognostic marker for cervical cancer

Recently, microRNAs (miRNAs) have been shown to be involved in multiple biological pathways that can influence tumor progression and metastasis and they can serve as prognostic biomarkers in many cancers. The present study examined the prognostic significance of miR-215 in cervical cancer. The paraffin-embedded paired cervical scrape samples and tumor tissue samples from 302 patients with stage II cervical cancer were detected for the expression of miR-215 by using qRT-PCR. A miR-215-based classifier was established by using the Cox regression model. The prognostic and predictive accuracy of this classifier was determined in both the internal testing group of 138 patients, and the external independent group of 280 patients. Moreover, cervical cancer HeLa cells overexpressing miR-215 (HeLa-miR-215) were constructed and subcutaneously injected into the nude mice to examine the effect of miR-215 on tumor growth and metastasis in vivo. The results showed that the expression level of miR-215 was significantly higher in cervical cancer tissues than in paired normal tissues (P<0.0001). When patients were classified into high- and low-risk cancer progression groups according to miR-215 level, the 5-year disease-free survival in high- and low-risk groups were 43% (95% CI: 32.1-51.6) and 67% (95% CI: 48.6-77.3) (hazard ratio [HR] 2.02, 95% CI: 1.16-3.52; P=0.013) respectively. Moreover, the expression level of miR-215 was negatively associated with survival rate in patients at TNM stage T3 (HR: 3.317; 95% CI: 1.18-5.14, P=0.017) and TNM stage T4 (HR: 3.48; 95% CI: 1.49-4.45, P=0.008). Tumor volume in nude mice injected with HeLa-miR-215 cells was significantly larger than that in mice injected with control HeLa cells. It was concluded that the expression level of miR-215 is associated with cervical tumor progression and worse survival rate, suggesting that it may serve as a potential prognostic marker to identify patients at higher risk of recurrence.

Clinical advances in molecular biomarkers for cancer diagnosis and therapy

Cancer diagnosis is currently undergoing a paradigm shift with the incorporation of molecular biomarkers as part of routine diagnostic panel. The molecular alteration ranges from those involving the DNA, RNA, microRNAs (miRNAs) and proteins. The miRNAs are recently discovered small non-coding endogenous single-stranded RNAs that critically regulates the development, invasion and metastasis of cancers. They are altered in cancers and have the potential to serve as diagnostic markers for cancer. Moreover, deregulating their activity offers novel cancer therapeutic approaches. The availability of high throughput techniques for the identification of altered cellular molecules allowed their use in cancer diagnosis. Their application to a variety of body specimens from blood to tissues has been helpful for appreciating their use in the clinical context. The development of innovative antibodies for immunohistochemical detection of proteins also assists in diagnosis and risk stratification. Overall, the novel cancer diagnostic tools have extended their application as prognostic risk factors and can be used as targets for personalized medicine.