Methylation status of homeobox genes in common human cancers

Homeobox and Polycomb target gene methylation in human solid tumors

DNA methylation is an epigenetic mark that plays an important role in defining cancer phenotypes, with global hypomethylation and focal hypermethylation at CpG islands observed in tumors. These methylation marks can also be used to define tumor types and provide an avenue for biomarker identification. The homeobox gene class is one that has potential for this use, as well as other genes that are Polycomb Repressive Complex 2 targets. To begin to unravel this relationship, we performed a pan-cancer DNA methylation analysis using sixteen Illumina HM450k array datasets from TCGA, delving into cancer-specific qualities and commonalities between tumor types with a focus on homeobox genes. Our comparisons of tumor to normal samples suggest that homeobox genes commonly harbor significant hypermethylated differentially methylated regions. We identified two homeobox genes, HOXA3 and HOXD10, that are hypermethylated in all 16 cancer types. Furthermore, we identified several potential homeobox gene biomarkers from our analysis that are uniquely methylated in only one tumor type and that could be used as screening tools in the future. Overall, our study demonstrates unique patterns of DNA methylation in multiple tumor types and expands on the interplay between the homeobox gene class and oncogenesis.

A comprehensive characterisation of phaeochromocytoma and paraganglioma tumours through histone protein profiling, DNA methylation and transcriptomic analysis genome wide

BACKGROUND

Phaeochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours. Pathogenic variants have been identified in more than 15 susceptibility genes; associated tumours are grouped into three Clusters, reinforced by their transcriptional profiles. Cluster 1A PPGLs have pathogenic variants affecting enzymes of the tricarboxylic acid cycle, including succinate dehydrogenase. Within inherited PPGLs, these are the most common. PPGL tumours are known to undergo epigenetic reprograming, and here, we report on global histone post-translational modifications and DNA methylation levels, alongside clinical phenotypes.

RESULTS

Out of the 25 histone post-translational modifications examined, Cluster 1A PPGLs were distinguished from other tumours by a decrease in hyper-acetylated peptides and an increase in H3K4me2. DNA methylation was compared between tumours from individuals who developed metastatic disease versus those that did not. The majority of differentially methylated sites identified tended to be completely methylated or unmethylated in non-metastatic tumours, with low inter-sample variance. Metastatic tumours by contrast consistently had an intermediate DNA methylation state, including the ephrin receptor EPHA4 and its ligand EFNA3. Gene expression analyses performed to identify genes involved in metastatic tumour behaviour pin-pointed a number of genes previously described as mis-regulated in Cluster 1A tumours, as well as highlighting the tumour suppressor RGS22 and the pituitary tumour-transforming gene PTTG1.

CONCLUSIONS

Combined transcriptomic and DNA methylation analyses revealed aberrant pathways, including ones that could be implicated in metastatic phenotypes and, for the first time, we report a decrease in hyper-acetylated histone marks in Cluster 1 PPGLs.

Genome-wide methylation profiling identify hypermethylated HOXL subclass genes as potential markers for esophageal squamous cell carcinoma detection

BACKGROUND

Numerous studies have revealed aberrant DNA methylation in esophageal squamous cell carcinoma (ESCC). However, they often focused on the partial genome, which resulted in an inadequate understanding of the shaped methylation features and the lack of available methylation markers for this disease.

METHODS

The current study investigated the methylation profiles between ESCC and paired normal samples using whole-genome bisulfite sequencing (WGBS) data and obtained a group of differentially methylated CpGs (DMC), differentially methylated regions (DMR), and differentially methylated genes (DMG). The DMGs were then verified in independent datasets and Sanger sequencing in our custom samples. Finally, we attempted to evaluate the performance of these genes as methylation markers for the classification of ESCC.

RESULTS

We obtained 438,558 DMCs, 15,462 DMRs, and 1568 DMGs. The four significantly enriched gene families of DMGs were CD molecules, NKL subclass, HOXL subclass, and Zinc finger C2H2-type. The HOXL subclass homeobox genes were observed extensively hypermethylated in ESCC. The HOXL-score estimated by HOXC10 and HOXD1 methylation, whose methylation status were then confirmed by sanger sequencing in our custom ESCC samples, showed good ability in discriminating ESCC from normal samples.

CONCLUSIONS

We observed widespread hypomethylation events in ESCC, and the hypermethylated HOXL subclass homeobox genes presented promising applications for the early detection of esophageal squamous cell carcinoma.

DNA Methylation Biomarkers in Cancer: Current Clinical Utility and Future Perspectives

Epigenetic alterations are related to inherited but reversible changes in modifications that regulate gene activity beyond the DNA sequence. DNA methylation is the best characterized epigenetic modification, controlling DNA stability, DNA structure, transcription, and regulation, contributing to normal development and differentiation. In this section, we first discuss the cellular functions of DNA methylation and focus on how this fundamental biological process is impaired in cancer. Changes in DNA methylation status in cancer have been heralded as promising targets for the development of diagnostic, prognostic, and predictive biomarkers due to their noninvasive accessibility in bodily fluids (such as blood, urine, stool), reversibility, stability, and frequency. The absence of markers for definitive diagnosis of most types of cancer and, in some cases, DNA methylation biomarkers being more specific and sensitive than commonly used protein biomarkers indicate a strong need for continued research to expand DNA methylation markers. Although the information on changes in DNA methylation status in cancer and research on its clinical relevance is rapidly increasing, the number of DNA methylation biomarkers currently available as commercial tests is very small. Here, we focus on the importance of DNA methylation location and target genes likely to be developed in the future for the development of biomarkers in addition to existing commercial tests. Following a detailed study of possible target genes, we summarize the current clinical application status of the most studied and validated DNA methylation biomarkers, including SEPT9, SDC2, BMP3, NDRG4, SFRP2, TFPI2, VIM and MGMT.

The prediction of tumor and normal tissues based on the DNA methylation values of ten key sites

Abnormal DNA methylation can alter the gene expression to promote or inhibit tumorigenesis in colon adenocarcinoma (COAD). However, the finding important genes and key sites of abnormal DNA methylation which result in the occurrence of COAD is still an eventful task. Here, we studied the effects of DNA methylation in the 12 types of genomic features on the changes of gene expression in COAD, the 10 important COAD-related genes and the key abnormal DNA methylation sites were identified. The effects of important genes on the prognosis were verified by survival analysis. Moreover, it was shown that the important genes were participated in cancer pathways and were hub genes in a co-expression network. Based on the DNA methylation levels in the ten sites, the least diversity increment algorithm for predicting tumor tissues and normal tissues in seventeen cancer types are proposed. The better results are obtained in jackknife test. For example, the predictive accuracies are 94.17 %, 91.28 %, 89.04 % and 88.89 %, respectively, for COAD, rectum adenocarcinoma, pancreatic adenocarcinoma and cholangiocarcinoma. Finally, by computing enrichment score of infiltrating immunocytes and the activity of immune pathways, we found that the genes are highly correlated with immune microenvironment.

An insight into the diagnostic and prognostic value of HOX A13 ’s expression in non‐muscle invasive bladder cancer

Background

Several studies have interrogated the molecular pathways and their interacting genes underlying bladder cancer (BCa) tumorigenesis, yet, the role of homeobox genes is still poorly understood. Specifically, HOXA13, which plays an important role as a major actor in the urogenital tract's development.

Methods

Immunohistochemical (IHC) staining was performed to inspect the differential expression of HOXA13 protein in non‐muscle‐invasive bladder cancer (NMIBC) and non‐tumoral tissues. A semiquantitative scoring system was adopted to evaluate the IHC labeling. Correlation to clinical parameters was performed by descriptive statistics. Overall survival was estimated by the Kaplan–Meier method and Cox regression model. The functional HOX A13 protein association networks (PPI) were obtained using String 11.0 database.

Results

HOX A13 exhibited cytoplasmic and nuclear staining. Its expression levels were lower in high‐grade NMIBC (HG NMIBC) compared to low‐grade ones (LG NMIBC). The expression of HOX A13 was correlated to tumor grade (LG/HG) (p = 0.036) and stage (TA/T1) (p = 0.036). Nevertheless, its expression was not correlated to clinical parameters and was not able to predict the overall survival of patients with HG NMIBC. Finally, PPI analysis revealed that HOX A13 seems to be a part of a molecular network holding mainly PBX1, MEIS, ALDH1A2, HOX A10, and HOX A11.

Conclusion

The deregulation of HOX A13 is not associated with the prognosis of BCa. It seems to be rather implicated in the early initiation of urothelial tumorigenesis and thus may serve as a diagnostic marker in patients with NMIBC. Further experimentations on larger validation sets are mandatory.

Aberrant DNA methylation impacts HOX genes expression in bone marrow mesenchymal stromal cells of myelodysplastic syndromes and de novo acute myeloid leukemia

DNA methylation, a major biological process regulating the transcription, contributes to the pathophysiology of hematologic malignancies, and hypomethylating agents are commonly used to treat myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML). In these diseases, bone marrow mesenchymal stromal cells (MSCs) play a key supportive role through the production of various signals and interactions. The DNA methylation status of MSCs, likely to reflect their functionality, might be relevant to understand their contribution to the pathophysiology of these diseases. Consequently, the aim of our study was to analyze the modifications of DNA methylation profiles of MSCs induced by MDS or AML. MSCs from MDS/AML patients were characterized via 5-methylcytosine quantification, gene expression profiles of key regulators of DNA methylation, identification of differentially methylated regions (DMRs) by methylome array, and quantification of DMR-coupled genes expression. MDS and AML-MSCs displayed global hypomethylation and under-expression of DNMT1 and UHRF1. Methylome analysis revealed aberrant methylation profiles in all MDS and in a subgroup of AML-MSCs. This aberrant methylation was preferentially found in the sequence of homeobox genes, especially from the HOX family (HOXA1, HOXA4, HOXA5, HOXA9, HOXA10, HOXA11, HOXB5, HOXC4, and HOXC6), and impacted on their expression. These results highlight modifications of DNA methylation in MDS/AML-MSCs, both at global and focal levels dysregulating the expression of HOX genes well known for their involvement in leukemogenesis. Such DNA methylation in MSCs could be the consequence of the malignant disease or could participate in its development through defective functionality or exosomal transfer of HOX transcription factors from MSCs to hematopoietic cells.

Functions of lncRNA DUXAP8 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) poses a serious threat to public health due to its significant morbidity and mortality rates. The processes of NSCLC formation and development are quite complex and involve numerous regulatory biomolecules. Long non-coding RNAs (lncRNAs) have attracted attention since they have been found to play critical roles in the tumorigenesis of various human malignancies. Recently, double homeobox A pseudogene 8 (DUXAP8) was identified as an oncogenic lncRNA that is overexpressed in different tumor types. In NSCLC, high expression of DUXAP8 is associated with poor prognosis in patients. The regulatory mechanism underlying the oncogenic effects of DUXAP8 can be divided into transcriptional level and post-transcriptional level. DUXAP8 promotes proliferation, epithelial-mesenchymal transition, and aerobic glycolysis in NSCLC cells. Moreover, DUXAP8 shows potential for the diagnosis and treatment of NSCLC. Herein, we review the molecular mechanisms underlying the DUXAP8-mediated phenotypes of NSCLC as well as its potential clinical applications.

Epigenome-Wide Association Study of Prostate Cancer in African Americans Identifies DNA Methylation Biomarkers for Aggressive Disease

DNA methylation plays important roles in prostate cancer (PCa) development and progression. African American men have higher incidence and mortality rates of PCa than other racial groups in U.S. The goal of this study was to identify differentially methylated CpG sites and genes between clinically defined aggressive and nonaggressive PCa in African Americans. We performed genome-wide DNA methylation profiling in leukocyte DNA from 280 African American PCa patients using Illumina MethylationEPIC array that contains about 860K CpG sties. There was a slight increase of overall methylation level (mean β value) with the increasing Gleason scores (GS = 6, GS = 7, GS ≥ 8, P for trend = 0.002). There were 78 differentially methylated CpG sites with P < 10-4 and 9 sites with P < 10-5 in the trend test. We also found 77 differentially methylated regions/genes (DMRs), including 10 homeobox genes and six zinc finger protein genes. A gene ontology (GO) molecular pathway enrichment analysis of these 77 DMRs found that the main enriched pathway was DNA-binding transcriptional factor activity. A few representative DMRs include HOXD8, SOX11, ZNF-471, and ZNF-577. Our study suggests that leukocyte DNA methylation may be valuable biomarkers for aggressive PCa and the identified differentially methylated genes provide biological insights into the modulation of immune response by aggressive PCa.

HOPX+ injury-resistant intestinal stem cells drive epithelial recovery after severe intestinal ischemia

Intestinal ischemia is a life-threatening emergency with mortality rates of 50%-80% due to epithelial cell death and resultant barrier loss. Loss of the epithelial barrier occurs in conditions including intestinal volvulus and neonatal necrotizing enterocolitis. Survival depends on effective epithelial repair; crypt-based intestinal epithelial stem cells (ISCs) are the source of epithelial renewal in homeostasis and after injury. Two ISC populations have been described: 1) active ISC [aISC; highly proliferative; leucine-rich-repeat-containing G protein-coupled receptor 5 (LGR5+)-positive or sex-determining region Y-box 9 -antigen Ki67-positive (SOX9+Ki67+)] and 2) reserve ISC [rISC; less proliferative; homeodomain-only protein X positive (HOPX+)]. The contributions of these ISCs have been evaluated both in vivo and in vitro using a porcine model of mesenteric vascular occlusion to understand mechanisms that modulate ISC recovery responses following ischemic injury. In our previously published work, we observed that rISC conversion to an activated state was associated with decreased HOPX expression during in vitro recovery. In the present study, we wanted to evaluate the direct role of HOPX on cellular proliferation during recovery after injury. Our data demonstrated that during early in vivo recovery, injury-resistant HOPX+ cells maintain quiescence. Subsequent early regeneration within the intestinal crypt occurs around 2 days after injury, a period in which HOPX expression decreased. When HOPX was silenced in vitro, cellular proliferation of injured cells was promoted during recovery. This suggests that HOPX may serve a functional role in ISC-mediated regeneration after injury and could be a target to control ISC proliferation.NEW & NOTEWORTHY This paper supports that rISCs are resistant to ischemic injury and likely an important source of cellular renewal following near-complete epithelial loss. Furthermore, we have evidence that HOPX controls ISC activity state and may be a critical signaling pathway during ISC-mediated repair. Finally, we use multiple novel methods to evaluate ISCs in a translationally relevant large animal model of severe intestinal injury and provide evidence for the potential role of rISCs as therapeutic targets.

TET2 Drives 5hmc Marking of GATA6 and Epigenetically Defines Pancreatic Ductal Adenocarcinoma Transcriptional Subtypes

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is characterized by advanced disease stage at presentation, aggressive disease biology, and resistance to therapy, resulting in an extremely poor 5-year survival rate of <10%. PDAC is classified into transcriptional subtypes with distinct survival characteristics, although how these arise is not known. Epigenetic deregulation, rather than genetics, has been proposed to underpin progression, but exactly why is unclear and is hindered by the technical limitations of analyzing clinical samples.

METHODS

We performed genome-wide epigenetic mapping of DNA modifications 5-methylcytosine and 5-hydroxymethylcytosine (5hmc) using oxidative bisulfite sequencing from formalin-embedded sections. We identified overlap with transcriptional signatures in formalin-fixed, paraffin-embedded tissue from resected patients, via bioinformatics using iCluster and mutational profiling and confirmed them in vivo.

RESULTS

We found that aggressive squamous-like PDAC subtypes result from epigenetic inactivation of loci, including GATA6, which promote differentiated classical pancreatic subtypes. We showed that squamous-like PDAC transcriptional subtypes are associated with greater loss of 5hmc due to reduced expression of the 5-methylcytosine hydroxylase TET2. Furthermore, we found that SMAD4 directly supports TET2 levels in classical pancreatic tumors, and loss of SMAD4 expression was associated with reduced 5hmc, GATA6, and squamous-like tumors. Importantly, enhancing TET2 stability using metformin and vitamin C/ascorbic acid restores 5hmc and GATA6 levels, reverting squamous-like tumor phenotypes and WNT-dependence in vitro and in vivo.

CONCLUSIONS

We identified epigenetic deregulation of pancreatic differentiation as an underpinning event behind the emergence of transcriptomic subtypes in PDAC. Our data showed that restoring epigenetic control increases biomarkers of classical pancreatic tumors that are associated with improved therapeutic responses and survival.

DeepProg: an ensemble of deep-learning and machine-learning models for prognosis prediction using multi-omics data

Multi-omics data are good resources for prognosis and survival prediction; however, these are difficult to integrate computationally. We introduce DeepProg, a novel ensemble framework of deep-learning and machine-learning approaches that robustly predicts patient survival subtypes using multi-omics data. It identifies two optimal survival subtypes in most cancers and yields significantly better risk-stratification than other multi-omics integration methods. DeepProg is highly predictive, exemplified by two liver cancer (C-index 0.73-0.80) and five breast cancer datasets (C-index 0.68-0.73). Pan-cancer analysis associates common genomic signatures in poor survival subtypes with extracellular matrix modeling, immune deregulation, and mitosis processes. DeepProg is freely available at https://github.com/lanagarmire/DeepProg.

Homeobox gene amplification and methylation in oral squamous cell carcinoma

OBJECTIVES

Investigate the DNA copy number and the methylation profile of the homeobox genes HOXA5, HOXA7, HOXA9, HOXB5, HOXB13, HOXC12, HOXC13, HOXD10, HOXD11, IRX4 and ZHX1, and correlate them with clinicopathological parameters and overall survival.

MATERIAL AND METHODS

DNA from OSCC samples and surgical margins were submitted to DNA amplification by qPCR and to DNA methylation analysis using a DNA Methylation PCR Array System.

RESULTS

HOXA5, HOXB5 and HOXD10 were amplified in surgical margins while HOXA9, HOXB13 and IRX4 were amplified in OSCC. HOXD10 demonstrated hypermethylation in half of the tumor while ZHX1 did not show hypermethylation. No correlation of DNA copy number or methylation with clinicopathological parameters or survival was observed.

CONCLUSION

HOXA9, HOXB13 and IRX4 genes appears to be regulated by amplification and HOXD10 by methylation in OSCC. Further studies are needed to determine the role of these events in OSCC development.

MNX1 Promotes Malignant Progression of Cervical Cancer via Repressing the Transcription of p21cip1

Motor neuron and pancreas homeobox 1 (MNX1) is a development-related genes and has been found to be highly expressed in several cancers. However, its biological function in cervical cancer remains largely unexplored. QRT-PCR, western blot, and IHC showed that MNX1 was abnormally overexpressed in cervical cancer tissues and cell lines. The high expression level of MNX1 correlated with poorer clinicopathologic characteristics in cervical cancer patients. Evaluated by RTCA (Real Time Cellular Analysis) proliferation assay, colony formation assay, EdU assay, transwell assay, and matrigel assay, we found that knockdown of MNX1 inhibited proliferation, migration and invasion of cervical cancer in vitro, while overexpression of MNX1 promoted malignant phenotype of cervical cancer. And subcutaneous xenograft model confirmed the malignant phenotype of MNX1 in vivo. Furthermore, flow cytometry, chromatin immunoprecipitation, and luciferase reporter assay indicated that MNX1 accelerated cell cycle transition by transcriptionally downregulating cyclin-dependent kinases p21^cip1. In summary, our study revealed that MNX1 exerted an oncogenic role in cervical cancer via repressing the transcription of p21^cip1 and thus accelerating cell cycle progression. Our results suggested that MNX1 was a potential diagnostic marker and therapeutic target for cervical cancer patients.

Increased HOXC6 mRNA expression is a novel biomarker of gastric cancer

In this study, we aimed to investigate the molecular biomarkers that are pivotal for the development and progression of gastric cancer (GC). We analyzed clinical specimens using RNA sequencing to identify the target genes. We found that the expression of HOXC6 mRNA was upregulated with the progression of cancer, which was validated by quantitative real time PCR and RNA in-situ hybridization. To compare the protein expression of HOXC6, we evaluated GC and normal gastric tissue samples using western blot analysis and immunohistochemistry. We detected significantly higher levels of HOXC6 in the GC tissues than in the normal controls at both mRNA and protein levels. The expression levels of HOXC6 mRNA in patients with advanced gastric cancer (AGC) were significantly higher than those in patients with early gastric cancer (EGC). Kaplan-Meier curves showed that high expression of HOXC6 mRNA is significantly associated with poor clinical prognosis. Our findings suggest that HOXC6 mRNA may be a novel biomarker and can be potentially valuable in predicting the prognosis of GC patients. Especially, HOXC6 mRNA in-situ hybridization may be a diagnostic tool for predicting prognosis of individual GC patients.

The Impact of Transcription Factor Prospero Homeobox 1 on the Regulation of Thyroid Cancer Malignancy

Transcription factor Prospero homeobox 1 (PROX1) is continuously expressed in the lymphatic endothelial cells, playing an essential role in their differentiation. Many reports have shown that PROX1 is implicated in cancer development and acts as an oncoprotein or suppressor in a tissue-dependent manner. Additionally, the PROX1 expression in many types of tumors has prognostic significance and is associated with patient outcomes. In our previous experimental studies, we showed that PROX1 is present in the thyroid cancer (THC) cells of different origins and has a high impact on follicular thyroid cancer (FTC) phenotypes, regulating migration, invasion, focal adhesion, cytoskeleton reorganization, and angiogenesis. Herein, we discuss the PROX1 transcript and protein structures, the expression pattern of PROX1 in THC specimens, and its epigenetic regulation. Next, we emphasize the biological processes and genes regulated by PROX1 in CGTH-W-1 cells, derived from squamous cell carcinoma of the thyroid gland. Finally, we discuss the interaction of PROX1 with other lymphatic factors. In our review, we aimed to highlight the importance of vascular molecules in cancer development and provide an update on the functionality of PROX1 in THC biology regulation.

Genome-wide DNA methylation analysis in canine gastrointestinal lymphoma

DNA methylation is the covalent modification of methyl groups to DNA mostly at CpG dinucleotides and one of the most studied epigenetic mechanisms that leads to gene expression variability without affecting the DNA sequence. Genome-wide analysis of DNA methylation identified the signatures that could define subtypes of human lymphoma patients. The objective of this study was to conduct the genome-wide analysis of DNA methylation in dogs with gastrointestinal lymphoma (GIL). Genomic DNA was extracted from endoscopic biopsies from 10 dogs with GIL. We performed Digital Restriction Enzyme Assay of DNA Methylation (DREAM) for genome-wide DNA methylation analysis that could provide highly quantitative information on DNA methylation levels of CpG sites across the dog genome. We successfully obtained data of quantitative DNA methylation level for 148,601–162,364 CpG sites per GIL sample. Next, we analyzed 83,132 CpG sites to dissect the differences in DNA methylation between GIL and normal peripheral blood mononuclear cells (PBMCs). We found 383–3,054 CpG sites that were hypermethylated in GIL cases compared to PBMCs. Interestingly, 773 CpG sites including promoter regions of 61 genes were identified to be commonly hypermethylated in more than half of the cases, suggesting conserved DNA methylation patterns that are abnormal in GIL. This study revealed that there was a large number of hypermethylated sites that are common in most of canine GIL. These abnormal DNA methylation could be involved in tumorigenesis of the canine GIL.

HOX genes function in Breast Cancer development

Breast cancer develops in the mammary glands during mammalian adulthood and is considered the second most common type of human carcinoma and the most incident and mortal in the female population. In contrast to other human structures, the female mammary glands continue to develop after birth, undergoing various modifications during pregnancy, lactation and involution under the regulation of hormones and transcription factors, including those encoded by the HOX clusters (A, B, C, and D). Interestingly, HOX gene deregulation is often associated to breast cancer development. Within the HOXB cluster, 8 out of the 10 genes present altered expression levels in breast cancer with an impact in its aggressiveness and resistance to hormone therapy, which highlights the importance of HOXB genes as potential therapeutic targets used to overcome the limitations of tamoxifen-resistant cancer treatments. Here, we review the current state of knowledge on the role of HOX genes in breast cancer, specially focus on HOXB, discussing the causes and consequences of HOXB gene deregulation and their relevance as prognostic factors and therapeutic targets.

DNA hypermethylation is associated with invasive phenotype of malignant melanoma

Tumor cell invasion is one of the key processes during cancer progression, leading to life-threatening metastatic lesions in melanoma. As methylation of cancer-related genes plays a fundamental role during tumorigenesis and may lead to cellular plasticity which promotes invasion, our aim was to identify novel epigenetic markers on selected invasive melanoma cells. Using Illumina BeadChip assays and Affymetrix Human Gene 1.0 microarrays, we explored the DNA methylation landscape of selected invasive melanoma cells and examined the impact of DNA methylation on gene expression patterns. Our data revealed predominantly hypermethylated genes in the invasive cells affecting the neural crest differentiation pathway and regulation of the actin cytoskeleton. Integrative analysis of the methylation and gene expression profiles resulted in a cohort of hypermethylated genes (IL12RB2, LYPD6B, CHL1, SLC9A3, BAALC, FAM213A, SORCS1, GPR158, FBN1 and ADORA2B) with decreased expression. On the other hand, hypermethylation in the gene body of the EGFR and RBP4 genes was positively correlated with overexpression of the genes. We identified several methylation changes that can have role during melanoma progression, including hypermethylation of the promoter regions of the ARHGAP22 and NAV2 genes that are commonly altered in locally invasive primary melanomas as well as during metastasis. Interestingly, the down-regulation of the methylcytosine dioxygenase TET2 gene, which regulates DNA methylation, was associated with hypermethylated promoter region of the gene. This can probably lead to the observed global hypermethylation pattern of invasive cells and might be one of the key changes during the development of malignant melanoma cells.

HOX genes as transcriptional and epigenetic regulators during tumorigenesis and their value as therapeutic targets

Several HOX genes are aberrantly expressed in a wide range of cancers interfering with their development and resistance to treatment. This seems to be often caused by alterations in the methylation profiles of their promoters. The role of HOX gene products in cancer is highly 'tissue specific', relying ultimately on their ability to regulate oncogenes or tumor-suppressor genes, directly as transcriptional regulators or indirectly interfering with the levels of epigenetic regulators. Nowadays, different strategies have been tested the use of HOX genes as therapeutic targets for cancer diagnosis and treatment. Here, we trace the history of the research concerning the involvement of HOX genes in cancer, their connection with epigenetic regulation and their potential use as therapeutic targets.

Effect of the key histone modifications on the expression of genes related to breast cancer

Abnormal histone modifications (HMs) and transcription factors (TFs) can alter the expression of cancer-related genes to promote tumorigenesis. We studied the variations of 11 HMs and 2 TFs in human breast cancer cells (MCF-7) compared to human normal mammary epithelial cells (HMEC), and the effects of HMs/TFs in various regions of the genome on the expression changes of breast cancer-related genes. Based on HMs and TFs signals' differences between MCF-7 and HMEC flanking TSSs, the up- and down-regulated genes in MCF-7 were predicted by Random Forest, and important HMs and regions were found. Results indicate that H3K79me2, H3K27ac, and H3K4me1 are particularly important for the changes of gene expression in MCF-7. Especially, H3K79me2 around the 60-th bin flanking TSSs may be the key for regulating gene expression. Our studies reveal H3K79me2 may be a core HM for breast cancer.

MEIS1 knockdown may promote differentiation of esophageal squamous carcinoma cell line KYSE-30

Background

MEIS1 (Myeloid ecotropic viral integration site 1), as a homeobox (HOX) transcription factor, has a dual function in different types of cancer. Although numerous roles are proposed for MEIS1 in differentiation, stem cell function, gastrointestinal development and tumorigenesis, the involved molecular mechanisms are poor understood. Our aim in this study was to elucidate the functional correlation between MEIS1, as regulator of differentiation process, and the involved genes in cell differentiation in human esophageal squamous carcinoma (ESC) cell line KYSE‐30.

Methods

The KYSE‐30 cells were transduced using recombinant retroviral particles containing specific shRNA sequence against MEIS1 to knockdown MEIS1 gene expression. Following RNA extraction and cDNA synthesis, mRNA expression of MEIS1 and the selected genes including TWIST1, EGF, CDX2, and KRT4 was examined using relative comparative real‐time PCR.

Results

Retroviral transduction caused a significant underexpression of MEIS1 in GFP‐hMEIS1 compared to control GFP cells approximately 5.5‐fold. While knockdown of MEIS1 expression caused a significant decrease in EGF and TWIST1 mRNA expression, nearly ‐8‐ and ‐12‐fold respectively, it caused a significant increase in mRNA expression of differentiation markers including KRT4 and CDX2, approximately 34‐ and 1.14‐fold, correspondingly.

Conclusion

MEIS1 gene silencing in KYSE‐30 cells increased expression of epithelial markers and decreased expression of epithelial‐mesenchymal transition (EMT) marker TWIST1. It may highlight the role of MEIS1 in differentiation process of KYSE‐30 cells. These results may confirm that MEIS1 silencing promotes differentiation and decreases EMT capability of ESC cell line KYSE‐30.

DNA methylation profiling implicates exposure to PCBs in the pathogenesis of B-cell chronic lymphocytic leukemia

OBJECTIVES

To characterize the impact of PCB exposure on DNA methylation in peripheral blood leucocytes and to evaluate the corresponding changes in relation to possible health effects, with a focus on B-cell lymphoma.

METHODS

We conducted an epigenome-wide association study on 611 adults free of diagnosed disease, living in Italy and Sweden, in whom we also measured plasma concentrations of 6 PCB congeners, DDE and hexachlorobenzene.

RESULTS

We identified 650 CpG sites whose methylation correlates strongly (FDR < 0.01) with plasma concentrations of at least one PCB congener. Stronger effects were observed in males and in Sweden. This epigenetic exposure profile shows extensive and highly statistically significant overlaps with published profiles associated with the risk of future B-cell chronic lymphocytic leukemia (CLL) as well as with clinical CLL (38 and 28 CpG sites, respectively). For all these sites, the methylation changes were in the same direction for increasing exposure and for higher disease risk or clinical disease status, suggesting an etiological link between exposure and CLL. Mediation analysis reinforced the suggestion of a causal link between exposure, changes in DNA methylation and disease. Disease connectivity analysis identified multiple additional diseases associated with differentially methylated genes, including melanoma for which an etiological link with PCB exposure is established, as well as developmental and neurological diseases for which there is corresponding epidemiological evidence. Differentially methylated genes include many homeobox genes, suggesting that PCBs target stem cells. Furthermore, numerous polycomb protein target genes were hypermethylated with increasing exposure, an effect known to constitute an early marker of carcinogenesis.

CONCLUSIONS

This study provides mechanistic evidence in support of a link between exposure to PCBs and the etiology of CLL and underlines the utility of omic profiling in the evaluation of the potential toxicity of environmental chemicals.

A Case of Identity: HOX Genes in Normal and Cancer Stem Cells

Stem cells are undifferentiated cells that have the unique ability to self-renew and differentiate into many different cell types. Their function is controlled by core gene networks whose misregulation can result in aberrant stem cell function and defects of regeneration or neoplasia. HOX genes are master regulators of cell identity and cell fate during embryonic development. They play a crucial role in embryonic stem cell differentiation into specific lineages and their expression is maintained in adult stem cells along differentiation hierarchies. Aberrant HOX gene expression is found in several cancers where they can function as either oncogenes by sustaining cell proliferation or tumor-suppressor genes by controlling cell differentiation. Emerging evidence shows that abnormal expression of HOX genes is involved in the transformation of adult stem cells into cancer stem cells. Cancer stem cells have been identified in most malignancies and proved to be responsible for cancer initiation, recurrence, and metastasis. In this review, we consider the role of HOX genes in normal and cancer stem cells and discuss how the modulation of HOX gene function could lead to the development of novel therapeutic strategies that target cancer stem cells to halt tumor initiation, progression, and resistance to treatment.

Roadmap of DNA methylation in breast cancer identifies novel prognostic biomarkers

BACKGROUND

Breast cancer is a highly heterogeneous disease resulting in diverse clinical behaviours and therapeutic responses. DNA methylation is a major epigenetic alteration that is commonly perturbed in cancers. The aim of this study is to characterize the relationship between DNA methylation and aberrant gene expression in breast cancer.

METHODS

We analysed DNA methylation and gene expression profiles from breast cancer tissue and matched normal tissue in The Cancer Genome Atlas (TCGA). Genome-wide differential methylation analysis and methylation-gene expression correlation was performed. Gene expression changes were subsequently validated in the METABRIC dataset. The Oncoscore tool was used to identify genes that had previously been associated with cancer in the literature. A subset of genes that had not previously been studied in cancer was chosen for further analysis.

RESULTS

We identified 368 CpGs that were differentially methylated between tumor and normal breast tissue (∆β > 0.4). Hypermethylated CpGs were overrepresented in tumor tissue and were found predominantly (56%) in upstream promoter regions. Conversely, hypomethylated CpG sites were found primarily in the gene body (66%). Expression analysis revealed that 209 of the differentially-methylated CpGs were located in 169 genes that were differently expressed between normal and breast tumor tissue. Methylation-expression correlations were predominantly negative (70%) for promoter CpG sites and positive (74%) for gene body CpG sites. Among these differentially-methylated and differentially-expressed genes, we identified 7 that had not previously been studied in any form of cancer. Three of these, TDRD10, PRAC2 and TMEM132C, contained CpG sites that showed diagnostic and prognostic value in breast cancer, particularly in estrogen-receptor (ER)-positive samples. A pan-cancer analysis confirmed differential expression of these genes together with diagnostic and prognostic value of their respective CpG sites in multiple cancer types.

CONCLUSION

We have identified 368 DNA methylation changes that characterize breast cancer tumor tissue, of which 209 are associated with genes that are differentially-expressed in the same samples. Novel DNA methylation markers were identified, of which cg12374721 (PRAC2), cg18081940 (TDRD10) and cg04475027 (TMEM132C) show promise as diagnostic and prognostic markers in breast cancer as well as other cancer types.

Deciphering the genomic, epigenomic, and transcriptomic landscapes of pre-invasive lung cancer lesions

The molecular alterations that occur in cells before cancer is manifest are largely uncharted. Lung carcinoma in situ (CIS) lesions are the pre-invasive precursor to squamous cell carcinoma. Although microscopically identical, their future is in equipoise, with half progressing to invasive cancer and half regressing or remaining static. The cellular basis of this clinical observation is unknown. Here, we profile the genomic, transcriptomic, and epigenomic landscape of CIS in a unique patient cohort with longitudinally monitored pre-invasive disease. Predictive modeling identifies which lesions will progress with remarkable accuracy. We identify progression-specific methylation changes on a background of widespread heterogeneity, alongside a strong chromosomal instability signature. We observed mutations and copy number changes characteristic of cancer and chart their emergence, offering a window into early carcinogenesis. We anticipate that this new understanding of cancer precursor biology will improve early detection, reduce overtreatment, and foster preventative therapies targeting early clonal events in lung cancer.

Architects meets Repairers: The interplay between homeobox genes and DNA repair

Homeobox genes are widely considered the major protagonists of embryonic development and tissue formation. For the past decades, it was established that the deregulation of these genes is intimately related to developmental abnormalities and a broad range of diseases in adults. Since the proper regulation and expression of homeobox genes are necessary for a successful developmental program and tissue function, their relation to DNA repair mechanisms become a necessary discussion. However, important as it is, studies focused on the interplay between homeobox genes and DNA repair are scarce, and there is no critical discussion on the subject. Hence, in this work, I aim to provide the first review of the current knowledge of the interplay between homeobox genes and DNA repair mechanisms, and offer future perspectives on this, yet, young ground for new researches. Critical discussion is conducted, together with a careful assessment of each reviewed topic.

Secreted frizzled-related protein 1 (SFRP1) gene methylation changes in the human lung adenocarcinoma cells treated with L-securinine

Lung cancer remains the leading cause of cancer-related death worldwide. It is important to explore the biomarkers of diagnosis and prognosis in lung cancer. To evaluate the cytotoxicity of L-securinine and the expression and methylation of secreted frizzled-related proteins (SFRPs) genes in the human lung adenocarcinoma cells, cell counting kit-8 (CCK-8) assay was used to assess the proliferation of lung adenocarcinoma cells treated with L-securinine. Quantitative real-time PCR (qRT-PCR) and bisulfite sequencing PCR were used to detect the expression and the DNA methylation of SFRPs genes, respectively. L-securinine inhibited the proliferation of lung adenocarcinoma cells and induced the upregulation of SFRP1 gene expression and the methylation changes at CpG sites in the SFRP1 promoter region. L-securinine was a potential agent in the treatment of lung cancer by upregulation of SFRP1 gene expression and changing the SFRP1 gene methylation.

Functional analysis of HOXA10 and HOXB4 in human medulloblastoma cell lines

Medulloblastoma (MB) is a malignant childhood brain tumor which at molecular level is classified into at least four major subtypes: WNT, SHH, group C and group D differing in response to treatment. Previous studies have associated changes in expression levels and activation of certain HOX genes with MB development. In the present study, we investigate the role of HOX genes in two attributes acquired by tumor cells: migration and proliferation potential, as well as, in vivo tumorigenic potential. We analyzed UW402, UW473, DAOY and ONS-76 human pediatric MB cell lines and cerebellum primary cultures. Two-color microarray-based gene expression analysis was used to identify differentially expressed HOX genes. Among the various HOX genes significantly overexpressed in DAOY and ONS-76 cell lines compared to UW402 and UW473 cell lines, HOXA10 and HOXB4 were selected for further analysis. The expression levels of these HOX genes were validated by real-time PCR. A mouse model was used to study the effect of the HOXA10 and HOXB4 genes on the in vivo tumorigenic potential and the in vitro proliferative and migration potential of MB cell lines. Our results show that the inhibition of HOXA10 in DAOY cell line led to increased in vitro cell migration while in vitro cell proliferation or in vivo tumorigenic potential were unaffected. We also observed that induced expression of HOXB4 in the UW473 cell line significantly reduced in vitro cell proliferation and migration capability of UW473 cells with no effect on the in vivo tumorigenicity. This suggests that HOXA10 plays a role in migration events and the HOXB4 gene is involved in proliferation and migration processes of medulloblastoma cells, however, it appears that these genes are not essential for the tumorigenic process of these cells.