Aberrant DNMT3B7 expression correlates to tissue type, stage, and survival across cancers

CLEC11A methylation is correlated to AML subtypes and cytogenetic risk factors but not patient demographics

Acute myeloid leukemia (AML) is an aggressive and lethal cancer of the blood, which leads to the death of over 11,000 patients in the United States each year. Research on identifying, characterizing, and treating AML is crucial in the fight against this deadly disease. Recent studies have examined the role of CLEC11A in cancer, including AML. However, there have been conflicting reports related to tumor progression and survival. Because survival is based on a variety of factors, including classification of the tumor, genetic risk factors, and demographics, it is imperative that we determine what role CLEC11A may have in cancer survival. Therefore, utilizing data from the Genomic Data Commons, we analyzed CLEC11A methylation in 108 AML patients compared to FAB classification, cytogenetic risk factors, age, race, and gender. Our results show statistically significant correlations between methylation of CLEC11A and FAB classification as well as poor genetic risk factors. However, no difference was observed in CLEC11A methylation when compared to demographic data. Our results, matched with a known biological function of CLEC11A in early hematopoiesis, indicate that CLEC11A may be an important marker for AML diagnosis and prognosis and provide relevant data in the ongoing search for novel therapeutics to improve AML survival.

Expression of DNA Methyltransferase 3B Isoforms Is Associated with DNA Satellite 2 Hypomethylation and Clinical Prognosis in Advanced High-Grade Serous Ovarian Carcinoma

Alterations in DNA methylation are critical for the carcinogenesis of ovarian tumors, especially ovarian carcinoma (OC). DNMT3B, a de novo DNA methyltransferase (DNMT), encodes for fifteen spliced protein products or isoforms. DNMT3B isoforms lack exons for the catalytic domain, with functional consequences on catalytic activity. Abnormal expression of DNMT3B isoforms is frequently observed in several types of cancer, such as breast, lung, kidney, gastric, liver, skin, leukemia, and sarcoma. However, the expression patterns and consequences of DNMT3B isoforms in OC are unknown. In this study, we analyzed each DNMT and DNMT3B isoforms expression by qPCR in 63 OC samples and their association with disease-free survival (DFS), overall survival (OS), and tumor progression. We included OC patients with the main histological subtypes of EOC and patients in all the disease stages and found that DNMTs were overexpressed in advanced stages (p-value < 0.05) and high-grade OC (p-value < 0.05). Remarkably, we found DNMT3B1 overexpression in advanced stages (p-value = 0.0251) and high-grade serous ovarian carcinoma (HGSOC) (p-value = 0.0313), and DNMT3B3 was overexpressed in advanced stages (p-value = 0.0098) and high-grade (p-value = 0.0004) serous ovarian carcinoma (SOC). Finally, we observed that overexpression of DNMT3B isoforms was associated with poor prognosis in OC and SOC. DNMT3B3 was also associated with FDS (p-value = 0.017) and OS (p-value = 0.038) in SOC patients. In addition, the ovarian carcinoma cell lines OVCAR3 and SKOV3 also overexpress DNMT3B3. Interestingly, exogenous overexpression of DNMT3B3 in OVCAR3 causes demethylation of satellite 2 sequences in the pericentromeric region. In summary, our results suggest that DNMT3B3 expression is altered in OC.

DNA Methyltransferases: From Evolution to Clinical Applications

DNA methylation is an epigenetic mark that living beings have used in different environments. The MTases family catalyzes DNA methylation. This process is conserved from archaea to eukaryotes, from fertilization to every stage of development, and from the early stages of cancer to metastasis. The family of DNMTs has been classified into DNMT1, DNMT2, and DNMT3. Each DNMT has been duplicated or deleted, having consequences on DNMT structure and cellular function, resulting in a conserved evolutionary reaction of DNA methylation. DNMTs are conserved in the five kingdoms of life: bacteria, protists, fungi, plants, and animals. The importance of DNMTs in whether methylate or not has a historical adaptation that in mammals has been discovered in complex regulatory mechanisms to develop another padlock to genomic insurance stability. The regulatory mechanisms that control DNMTs expression are involved in a diversity of cell phenotypes and are associated with pathologies transcription deregulation. This work focused on DNA methyltransferases, their biology, functions, and new inhibitory mechanisms reported. We also discuss different approaches to inhibit DNMTs, the use of non-coding RNAs and nucleoside chemical compounds in recent studies, and their importance in biological, clinical, and industry research.

Targeting DNMTs to overcome enzalutamide resistance in prostate cancer

Prostate cancer is the second leading cause of cancer death among men in the United States. The androgen receptor (AR) antagonist enzalutamide is a FDA-approved drug for treatment of patients with late-stage prostate cancer and is currently under clinical study for early-stage prostate cancer treatment. After a short positive response period to enzalutamide, tumors will develop drug resistance. In this study, we uncovered that DNA methylation was deregulated in enzalutamide-resistant cells. DNMT activity and DNMT3B expression were upregulated in resistant cell lines. Enzalutamide induced the expression of DNMT3A and DNMT3B in prostate cancer cells with a potential role of p53 and pRB in this process. The overexpression of DNMT3B3, a DNMT3B variant, promoted an enzalutamide-resistant phenotype in C4-2B cell lines. Inhibition of DNA methylation and DNMT3B knockdown induced a re-sensitization to enzalutamide. Decitabine treatment in enzalutamide-resistant cells induced a decrease of the expression of AR-V7 and changes of genes for apoptosis, DNA repair and mRNA splicing. Combination treatment of Decitabine and enzalutamide induced a decrease of tumor weight, Ki-67 and AR-V7 expression and an increase of cleaved-caspase3 levels in 22Rv1 xenografts. The collective results suggest that DNA methylation pathway is deregulated after enzalutamide resistance onset and that targeting DNA methyltransferases restores the sensitivity to enzalutamide in prostate cancer cells.

E-Cadherin, NFATC3, and PLP2 Are Differentially Methylated in Multiple Cancers

It is well documented that cancer cells have abnormal methylation patterns often caused by faulty methylating machinery. Specifically, E-cadherin, NFATC3, and PLP2 are 3 genes known to be aberrantly methylated in cancer cells. These genes are well documented for their role in signaling pathways involved with cell proliferation, adhesion, migration, and other signs of tumor progression. Therefore, changes in gene expression of CDH1, NFATC3, and PLP2 due to aberrant methylation can lead to profound changes in cellular function and tumor formation. In order to ensure that previous in vitro and in vivo methylation studies match what is observed in the clinic, we utilized a bioinformatics approach to complete an extensive analysis of methylation patterns of these 3 genes, analyzing over 5000 patient samples, across all cancers for which both normal and tumor tissues were available. Specifically, we analyzed overall and site-specific methylation patterns, at CpG islands and shores, of all 3 genes across 14 cancer types. Furthermore, we compared these methylation levels in normal and tumor samples of both matched and unmatched patient samples in order to determine any differences between groups. Finally, we examined whether an aberrant DNA methyltransferase, DNMT3B7, known to be expressed in cancer cells and to alter methylation patterns in vitro correlated with altered overall and site-specific methylation of CDH1, NFATC3, and PLP2 in these patient samples. Our results indicate that methylation patterns of CDH1 and NFATC3 were unexpectedly varied across tumors, contrary to previous studies performed in vitro, while PLP2 showed the expected hypomethylation pattern in tumor tissues. We also observed some correlation between DNMT3B7 expression and methylation patterns of these genes, but patterns were inconsistent. Taken together, these results emphasize the necessity for in vivo and patient studies rather than a complete reliance on in vitro data and provide multiple areas of future research.

De novo methyltransferases: Potential players in diseases and new directions for targeted therapy

Epigenetic modifications govern gene expression by guiding the human genome on 'what to express and what not to'. DNA methyltransferases (DNMTs) establish methylation patterns on DNA, particularly in CpG islands, and such patterns play a major role in gene silencing. DNMTs are a family of proteins/enzymes (DNMT1, 2, 3A, 3B, and 3L), among which, DNMT1 (maintenance methyltransferase) and DNMT3 (de novo methyltransferases) that direct mammalian development and genome imprinting are highly investigated. In recent decades, many studies revealed a strong association of DNA methylation patterns with gene expression in various clinical conditions. Differential expression of DNMT3 family proteins and their splice variants result in changes in methylation patterns and such alterations have been associated with the initiation and progression of various diseases, especially cancer. This review will discuss the aberrant modifications generated by DNMT3 proteins under various clinical conditions, suggesting a potential signature for de novo methyltransferases in targeted disease therapy. Further, this review discusses the possibility of using 'CpG island methylation signatures' as promising biomarkers and emphasizes 'targeted hypomethylation' by disrupting the interaction of specific DNMT-protein complexes as the future of cancer therapeutics.

DNA hypermethylation in disease: mechanisms and clinical relevance

Increasing numbers of studies implicate abnormal DNA methylation in cancer and many non-malignant diseases. This is consistent with numerous findings about differentiation-associated changes in DNA methylation at promoters, enhancers, gene bodies, and sites that control higher-order chromatin structure. Abnormal increases or decreases in DNA methylation contribute to or are markers for cancer formation and tumour progression. Aberrant DNA methylation is also associated with neurological diseases, immunological diseases, atherosclerosis, and osteoporosis. In this review, I discuss DNA hypermethylation in disease and its interrelationships with normal development as well as proposed mechanisms for the origin of and pathogenic consequences of disease-associated hypermethylation. Disease-linked DNA hypermethylation can help drive oncogenesis partly by its effects on cancer stem cells and by the CpG island methylator phenotype (CIMP); atherosclerosis by disease-related cell transdifferentiation; autoimmune and neurological diseases through abnormal perturbations of cell memory; and diverse age-associated diseases by age-related accumulation of epigenetic alterations.

Piperine: role in prevention and progression of cancer

Cancer is among the leading causes of death worldwide. Several pharmacological protocols have been developed in order to block tumor progression often showing partial efficacy and severe counterproductive effects. It is now conceived that a healthy lifestyle coupled with the consumption of certain phytochemicals can play a protective role against tumor development and progression. According to this vision, it has been introduced the concept of "chemoprevention". This term refers to natural agents with the capability to interfere with the tumorigenesis and metastasis, or at least, attenuate the cancer-related symptoms. Piperine (1-Piperoylpiperidine), a main extract of Piper longum and Piper nigrum, is an alkaloid with a long history of medicinal use. In fact, it exhibits a variety of biochemical and pharmaceutical properties, including chemopreventive activities without significant cytotoxic effects on normal cells, at least at doses < of 250 µg/ml. The aim of this review is to discuss the relevant molecular and cellular mechanisms underlying the chemopreventive action of this natural alkaloid.

Polo-Like Kinase 4 (PLK4) Is Overexpressed in Central Nervous System Neuroblastoma (CNS-NB)

Neuroblastoma (NB) is the most common extracranial solid tumor in pediatrics, with rare occurrences of primary and metastatic tumors in the central nervous system (CNS). We previously reported the overexpression of the polo-like kinase 4 (PLK4) in embryonal brain tumors. PLK4 has also been found to be overexpressed in a variety of peripheral adult tumors and recently in peripheral NB. Here, we investigated PLK4 expression in NBs of the CNS (CNS-NB) and validated our findings by performing a multi-platform transcriptomic meta-analysis using publicly available data. We evaluated the PLK4 expression by quantitative real-time PCR (qRT-PCR) on the CNS-NB samples and compared the relative expression levels among other embryonal and non-embryonal brain tumors. The relative PLK4 expression levels of the NB samples were found to be significantly higher than the non-embryonal brain tumors (p-value < 0.0001 in both our samples and in public databases). Here, we expand upon our previous work that detected PLK4 overexpression in pediatric embryonal tumors to include CNS-NB. As we previously reported, inhibiting PLK4 in embryonal tumors led to decreased tumor cell proliferation, survival, invasion and migration in vitro and tumor growth in vivo, and therefore PLK4 may be a potential new therapeutic approach to CNS-NB.