Methyl-CpG Binding Domain Protein 2 Inhibits the Malignant Characteristic of Lung Adenocarcinoma through the Epigenetic Modulation of 10 to 11 Translocation 1 and miR-200s

Crosstalk between miRNAs and DNA Methylation in Cancer

miRNAs are some of the most well-characterized regulators of gene expression. Integral to several physiological processes, their aberrant expression often drives the pathogenesis of both benign and malignant diseases. Similarly, DNA methylation represents an epigenetic modification influencing transcription and playing a critical role in silencing numerous genes. The silencing of tumor suppressor genes through DNA methylation has been reported in many types of cancer and is associated with tumor development and progression. A growing body of literature has described the crosstalk between DNA methylation and miRNAs as an additional layer in the regulation of gene expression. Methylation in miRNA promoter regions inhibits its transcription, while miRNAs can target transcripts and subsequently regulate the proteins responsible for DNA methylation. Such relationships between miRNA and DNA methylation serve an important regulatory role in several tumor types and highlight a novel avenue for potential therapeutic targets. In this review, we discuss the crosstalk between DNA methylation and miRNA expression in the pathogenesis of cancer and describe how miRNAs influence DNA methylation and, conversely, how methylation impacts the expression of miRNAs. Finally, we address how these epigenetic modifications may be leveraged as biomarkers in cancer.

MBD2 facilitates tumor metastasis by mitigating DDB2 expression

Despite past extensive studies, the pathoetiologies underlying tumor metastasis remain poorly understood, which renders its treatment largely unsuccessful. The methyl-CpG-binding domain 2 (MBD2), a "reader" to interpret DNA methylome-encoded information, has been noted to be involved in the development of certain types of tumors, while its exact impact on tumor metastasis remains elusive. Herein we demonstrated that patients with LUAD metastasis were highly correlated with enhanced MBD2 expression. Therefore, knockdown of MBD2 significantly attenuated the migration and invasion of LUAD cells (A549 and H1975 cell lines) coupled with attenuated epithelial-mesenchymal transition (EMT). Moreover, similar results were observed in other types of tumor cells (B16F10). Mechanistically, MBD2 selectively bound to the methylated CpG DNA within the DDB2 promoter, by which MBD2 repressed DDB2 expression to promote tumor metastasis. As a result, administration of MBD2 siRNA-loaded liposomes remarkably suppressed EMT along with attenuated tumor metastasis in the B16F10 tumor-bearing mice. Collectively, our study indicates that MBD2 could be a promising prognostic marker for tumor metastasis, while administration of MBD2 siRNA-loaded liposomes could be a viable therapeutic approach against tumor metastasis in clinical settings.

Epigenetic Regulation of Angiogenesis in Development and Tumors Progression: Potential Implications for Cancer Treatment

Angiogenesis is a multi-stage process of new blood vessel development from pre-existing vessels toward an angiogenic stimulus. The process is essential for tissue maintenance and homeostasis during embryonic development and adult life as well as tumor growth. Under normal conditions, angiogenesis is involved in physiological processes, such as wound healing, cyclic regeneration of the endometrium, placental development and repairing certain cardiac damage, in pathological conditions, it is frequently associated with cancer development and metastasis. The control mechanisms of angiogenesis in carcinogenesis are tightly regulated at the genetic and epigenetic level. While genetic alterations are the critical part of gene silencing in cancer cells, epigenetic dysregulation can lead to repression of tumor suppressor genes or oncogene activation, becoming an important event in early development and the late stages of tumor development, as well. The global alteration of the epigenetic spectrum, which includes DNA methylation, histone modification, chromatin remodeling, microRNAs, and other chromatin components, is considered one of the hallmarks of cancer, and the efforts are concentrated on the discovery of molecular epigenetic markers that identify cancerous precursor lesions or early stage cancer. This review aims to highlight recent findings on the genetic and epigenetic changes that can occur in physiological and pathological angiogenesis and analyze current knowledge on how deregulation of epigenetic modifiers contributes to tumorigenesis and tumor maintenance. Also, we will evaluate the clinical relevance of epigenetic markers of angiogenesis and the potential use of "epi-drugs" in modulating the responsiveness of cancer cells to anticancer therapy through chemotherapy, radiotherapy, immunotherapy and hormone therapy as anti-angiogenic strategies in cancer.

Prognostic role of high TET1 expression in patients with solid tumors: A meta-analysis

BACKGROUND

Recently, increased expression of TET1 has been shown to inhibit tumor development in many studies. Therefore, a meta-analysis was conducted to assess the prognostic role of TET1 in solid tumors.

METHODS

PubMed, Embase, and the Web of Science (last updated on June 13, 2019) were searched and 16 eligible studies involving 3100 patients were eventually taken forward into the meta-analysis.

RESULTS

Pooled results indicated that higher TET1 expression in cancer tissues was associated with improved overall survival (OS) [hazard ratio (HR) = 0.736, 95% confidence interval (95% CI) = 0.542-0.998, P = .049]. In the subgroup analysis, higher TET1 expression in respiratory tumors (HR = 0.778, 95% CI = 0.639-0.946, P = .012) and breast cancer in Asian patients (HR = 0.326, 95% CI = 0.199-0.533, P < .001) were significantly associated with better OS. In addition, the association between high TET1 expression and prolonged OS was also statistically significant in the following subgroups; data source from samples (HR = 0.561, 95% CI = 0.384-0.819, P = .003), reported in text (HR = 0.539, 95% CI = 0.312-0.931, P = .027), TET1 protein (HR = 0.635, 95% CI = 0.409-0.984, P = .042), Asians (HR = 0.563, 95% CI = 0.376-0.844, P = .005).

CONCLUSION

This meta-analysis displays that high expression levels of TET1 in tissues is significantly associated with better survival in patients with solid tumors. This finding can be used as evidence to the tone that TET1 may be a useful target for the treatment of patients with solid tumors in the future.

SMAD-6, -7 and -9 are potential molecular biomarkers for the prognosis in human lung cancer

SMADs, a family of proteins that function as signal transducers and transcriptional regulators to regulate various signaling pathways, including the transforming growth factor-β signaling pathway, are similar to the mothers against decapentaplegic family of genes and the sma gene family in Caenorhabditis elegans. SMADs generate context-dependent modulation by interacting with various sequence-specific transcription factors, such as E2F4/5, c-Fos, GATA3, YY1 and SRF, which have been found to serve a key role in lung carcinoma oncogenesis and progression. However, the prognostic values of the eight SMADs in lung cancer have not been fully understood. In the present study, the expression levels and survival data of SMADs in patients with lung carcinoma from the Oncomine, Gene Expression Profiling Interactive Analysis, Kaplan-Meier plotter and cBioPortal databases were downloaded and analyzed. It was found that the mRNA expression levels of SMAD-6, -7 and -9 were decreased in lung adenocarcinoma and squamous cell carcinoma compared with that in adjacent normal tissues, while there was no significant difference in SMADs 1-5. Survival analysis revealed that not only were low transcriptional levels of SMAD-6, -7 and -9 associated with low overall survival but they also had prognostic role for progression-free survival and post-progression survival (P<0.05) in patients with lung carcinoma. In conclusion, the present study demonstrated that SMAD-6, -7 and -9 are potential biomarkers for the prognosis of patients with lung carcinoma.

Expression and clinical significance of methyl-CpG binding domain protein 2 in high-grade serous ovarian cancer

Platinum resistance is an important cause of clinical recurrence and mortality of patients with high-grade serous ovarian cancer (HGSOC). Methyl-CpG binding domain protein 2 (MBD2) serves an important role in tumor progression; however, its role in HGSOC remains unclear. The aim of the present study was to investigate the expression of MBD2 in HGSOC and its role in drug resistance and prognosis of HGSOC. MBD2 expression was analyzed by immunohistochemical staining and western blotting. The associations between MBD2 expression and clinical pathological features, platinum resistance and patient prognosis were analyzed using a χ² test, Kaplan-Meier analysis and Cox regression analysis. Positive MBD2 expression was detected in 73 (63.5%) of the HGSOC tissue samples, whereas it was undetectable in all 16 normal tissue samples (100%) analyzed, indicating a significantly higher expression level in tumor tissues compared with normal tissues (P<0.001). Additionally, MBD2 expression was significantly higher in platinum-resistant cases compared with that in platinum-sensitive cases (P<0.05). In addition, high expression of MBD2 was negatively associated with relapse-free survival (P<0.05). In conclusion, MBD2 was demonstrated to be a potential drug target and a biomarker for poor prognosis in HGSOC.