Enhanced MAPK signaling drives ETS1-mediated induction of miR-29b leading to downregulation of TET1 and changes in epigenetic modifications in a subset of lung SCC

Epi-miRNAs: Modern mediators of methylation status in human cancers

Methylation of the fundamental macromolecules, DNA/RNA, and proteins, is remarkably abundant, evolutionarily conserved, and functionally significant in cellular homeostasis and normal tissue/organism development. Disrupted methylation imprinting is strongly linked to loss of the physiological equilibrium and numerous human pathologies, and most importantly to carcinogenesis, tumor heterogeneity, and cancer progression. Mounting recent evidence has documented the active implication of miRNAs in the orchestration of the multicomponent cellular methylation machineries and the deregulation of methylation profile in the epigenetic, epitranscriptomic, and epiproteomic levels during cancer onset and progression. The elucidation of such regulatory networks between the miRNome and the cellular methylation machineries has led to the emergence of a novel subclass of miRNAs, namely "epi-miRNAs" or "epi-miRs." Herein, we have summarized the existing knowledge on the functional role of epi-miRs in the methylation dynamic landscape of human cancers and their clinical utility in modern cancer diagnostics and tailored therapeutics. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Lysine demethylase 5A promotes prostate adenocarcinoma progression by suppressing microRNA-330-3p expression and activating the COPB2/PI3K/AKT axis in an ETS1-dependent manner

Lysine demethylase 5A (KDM5A) is a histone demethylase frequently involved in cancer progression. This research aimed to explore the function of KDM5A in prostate adenocarcinoma (PRAD) and the molecular mechanism. KDM5A was highly expressed in collected PRAD tissues and acquired PRAD cells. High KDM5A expression was correlated with reduced survival and poor prognosis of patients with PRAD. Knockdown of KDM5A suppressed the proliferation, colony formation, migration, and invasiveness of PRAD cells and reduced angiogenesis ability of endothelial cells. Downstream molecules implicated in KDM5A mediation were predicted using integrated bioinformatic analyses. KDM5A enhanced ETS proto-oncogene 1 (ETS1) expression through demethylation of H3K4me2 at its promoter. ETS1 suppressed the transcription activity of miR-330-3p, and either further ETS1 overexpression or miR-330-3p inhibition blocked the functions of KDM5A knockdown in PRAD. miR-330-3p targeted coatomer protein complex subunit β2 (COPB2) mRNA. Downregulation of miR-330-3p restored the expression of COPB2 and activated the PI3K/AKT pathway in PRAD. The results in vitro were reproduced in vivo where KDM5A downregulation suppressed the growth and metastasis of xenograft tumors in nude mice. In conclusion, this study demonstrated that KDM5A promoted PRAD by suppressing miR-330-3p and activating the COPB2/PI3K/AKT axis in an ETS1-dependent manner.

Application of non-negative matrix factorization in oncology: one approach for establishing precision medicine

The increase in the expectations of artificial intelligence (AI) technology has led to machine learning technology being actively used in the medical field. Non-negative matrix factorization (NMF) is a machine learning technique used for image analysis, speech recognition, and language processing; recently, it is being applied to medical research. Precision medicine, wherein important information is extracted from large-scale medical data to provide optimal medical care for every individual, is considered important in medical policies globally, and the application of machine learning techniques to this end is being handled in several ways. NMF is also introduced differently because of the characteristics of its algorithms. In this review, the importance of NMF in the field of medicine, with a focus on the field of oncology, is described by explaining the mathematical science of NMF and the characteristics of the algorithm, providing examples of how NMF can be used to establish precision medicine, and presenting the challenges of NMF. Finally, the direction regarding the effective use of NMF in the field of oncology is also discussed.

The interaction between ETS transcription factor family members and microRNAs: A novel approach to cancer therapy

In cancer biology, ETS transcription factors promote tumorigenesis by mediating transcriptional regulation of numerous genes via the conserved ETS DNA-binding domain. MicroRNAs (miRNAs) act as posttranscriptional regulators to regulate various tumor-promoting or tumor-suppressing factors. Interactions between ETS factors and miRNAs regulate complex tumor-promoting and tumor-suppressing networks. This review discusses the progress of ETS factors and miRNAs in cancer research in detail. We focused on characterizing the interaction of the miRNA/ETS axis with competing endogenous RNAs (ceRNAs) and its regulation in posttranslational modifications (PTMs) and the tumor microenvironment (TME). Finally, we explore the prospect of ETS factors and miRNAs in therapeutic intervention. Generally, interactions between ETS factors and miRNAs provide fresh perspectives into tumorigenesis and development and novel therapeutic approaches for malignant tumors.

Coloured noise induces phenotypic diversity with energy dissipation

Genes integrate many different sources of noise to adapt their survival strategy with energy costs, but how this noise impacts gene phenotype switching is not fully understood. Here, we refine a mechanistic model with multiplicative and additive coloured noise and analyse the influence of noise strength (NS) and autocorrelation time (AT) on gene phenotypic diversity. Different from white noise, we found that in the autocorrelation time-scale plane, increasing the multiplicative noise will broaden the bimodal region of the gene product, and additive noise will induce bimodal region drift from the lower level to the higher level, while the AT will promote this transition. Specifically, the effect of AT on gene expression is similar to a feedback loop; that is, the AT of multiplicative noise will elongate the mean first passage time (MFPT) from the low stable state to the high stable state, but it will reduce the MFPT from the high stable state to the low stable state, and the opposite is true for additive noise. Moreover, these transitions will violate the detailed equilibrium and then consume energy. By effective topology network reconstruction, we found that when the NS is small, the more obvious the bimodality is, the lower the energy dissipation; however, when the NS is large, it will consume more energy with a tendency for bimodality. The overall analysis implies that living organisms will utilize noise strength and its autocorrelation time for better survival in complex and fluctuating environments.

Exosomes from M1‐polarized macrophages promote apoptosis in lung adenocarcinoma via the miR‐181a‐5p/ETS1/STK16 axis

Serine/threonine kinase 16 (STK16) is crucial in on regulating tumor cell proliferation, apoptosis, and prognosis. Activated M1 macrophages regulate lung adenocarcinoma (LUAD) growth by releasing exosomes. This study aims to investigate the role of STK16 and then focus on the possible mechanisms through which exosomes derived from M1 macrophages play their roles in LUAD cells by targeting STK16. Clinical LUAD samples were used to evaluate the expression of STK16 and its association with prognosis. Exosomes were isolated from M0 and M1 macrophages by ultracentrifugation and were then identified by electron microscopy and western blotting. In vitro gain‐ and loss‐of‐function experiments with LUAD cells were performed to elucidate the functions of miR‐181a‐5p, ETS1, and STK16, and mouse xenograft models were used to verify the function of STK16 in vivo. Western blotting, quantitative real‐time PCR, CCK‐8 assay, cell apoptosis, immunohistochemistry staining, luciferase assay, ChIP assay, and bioinformatics analysis were performed to reveal the underlying mechanisms. High expression of STK16 was observed in LUAD tissues and cells, and higher expression of STK16 was associated with worse prognosis. Silencing STK16 expression inhibited cell proliferation and promoted apoptosis via the AKT1 pathway. Exosomes from M1 macrophages inhibited viability and promoted apoptosis by inhibiting STK16. Moreover, miR‐181a‐5p is the functional molecule in M1 macrophage‐derived exosomes and plays a vital role in inhibiting cell proliferation and promoting apoptosis by targeting ETS1 and STK16. Hence, exosomes derived from M1 macrophages were capable of inhibiting viability and promoting apoptosis in LUAD via the miR‐181a‐5p/ETS1/STK16 axis.

Deoxyribonucleic Acid 5-Hydroxymethylation in Cell-Free Deoxyribonucleic Acid, a Novel Cancer Biomarker in the Era of Precision Medicine

Aberrant methylation has been regarded as a hallmark of cancer. 5-hydroxymethylcytosine (5hmC) is recently identified as the ten-eleven translocase (ten-eleven translocase)-mediated oxidized form of 5-methylcytosine, which plays a substantial role in DNA demethylation. Cell-free DNA has been introduced as a promising tool in the liquid biopsy of cancer. There are increasing evidence indicating that 5hmC in cell-free DNA play an active role during carcinogenesis. However, it remains unclear whether 5hmC could surpass classical markers in cancer detection, treatment, and prognosis. Here, we systematically reviewed the recent advances in the clinic and basic research of DNA 5-hydroxymethylation in cancer, especially in cell-free DNA. We further discuss the mechanisms underlying aberrant 5hmC patterns and carcinogenesis. Synergistically, 5-hydroxymethylation may act as a promising biomarker, unleashing great potential in early cancer detection, prognosis, and therapeutic strategies in precision oncology.

Keratin 80 regulated by miR-206/ETS1 promotes tumor progression via the MEK/ERK pathway in ovarian cancer

Introduction: Keratin 80 (KRT80) is a type II epithelial keratin protein that plays an important role in cell differentiation and tumor progression. However, its role and mechanisms in ovarian cancer remain unclear. Methods: The effect of KRT80 on the survival and prognosis of patients with ovarian cancer was determined using immunohistochemistry. Cell lines overexpressing KRT80 and with KRT80 knockdown were established to study its effect on the malignant behavior of ovarian cancer cells. Western blotting was used to detect changes in related molecules, and in the MEK/ERK signal transduction pathway. ChIP assay was used to confirm that ETS1 regulates KRT80 at the transcriptional level. A double luciferase assay was used to confirm the target of miR-206. Results: The expression levels of KRT80 were high in ovarian cancer tissue, and were related to survival and prognosis. KRT80 expression is an independent prognostic factor in patients with ovarian cancer. KRT80 overexpression promotes the proliferation of ovarian cancer cells, the transition from G1 phase to S phase, invasion, and migration. KRT80 overexpression increased the expression of BCL2/BAX, CyclinD1, MMP2, MMP9, and N-cadherin, decreased the expression of E-cadherin, and increased the phosphorylation of MEK and ERK. ETS1 binds to the upstream promoter sequence of KRT80 and regulates KRT80 expression at the transcriptional level. ETS1 is a direct target of miR-206 in ovarian cancer cells. Conclusion: KRT80 regulated by miR-206/ETS1 promotes tumor progression via the MEK/ERK pathway in ovarian cancer, and KRT80 may have applications as a screening biomarker and potential therapeutic target for ovarian cancer.

The Role of miRNA in the Pathophysiology of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) represent a tumor group that is both rare and heterogeneous. Prognosis is largely determined by the tumor grading and the site of the primary tumor and metastases. Despite intensive research efforts, only modest advances in diagnostic and therapeutic approaches have been achieved in recent years. For patients with non-respectable tumor stages, prognosis is poor. In this context, the development of novel diagnostic tools for early detection of NETs and prediction of tumor response to therapy as well as estimation of the overall prognosis would greatly improve the clinical management of NETs. However, identification of novel diagnostic molecules is hampered by an inadequate understanding of the pathophysiology of neuroendocrine malignancies. It has recently been demonstrated that microRNA (miRNA), a family of small RNA molecules with an established role in the pathophysiology of quite different cancer entities, may also play a role as a biomarker. Here, we summarize the available knowledge on the role of miRNAs in the development of NET and highlight their potential use as serum-based biomarkers in the context of this disease. We discuss important challenges currently preventing their use in clinical routine and give an outlook on future directions of miRNA research in NET.

ETS Proto-Oncogene 1 Suppresses MicroRNA-128 Transcription to Promote Osteogenic Differentiation Through the HOXA13/β-Catenin Axis

ETS proto-oncogene 1 (ETS1) has been implicated in osteoporosis (OP), but the exact molecular mechanisms are complex. This work focuses on the impact of ETS1 on the osteogenic differentiation and the molecules involved. A mouse pre-osteoblast cell line MC3T3-E1 was used for in vitro experiments. ETS1 was upregulated during the process of osteogenic differentiation of MC3T3-E1 cells. Overexpression of ETS1 promoted expression of osteogenic markers, alkaline phosphate concentration, and calcareous accumulation in cells. ETS1 was found to specifically bind to miR-128 promoter to suppress its transcription, while miR-128 could target homeobox A13 (HOXA13). Therefore, ETS1 suppressed miR-128 transcription to upregulate HOXA13 expression. Overexpression of HOXA13 promoted the osteogenic differentiation ability of cells and increased the protein level of β-catenin. Either overexpression of miR-128 or downregulation of β-catenin by CWP232228, a β-catenin-specific antagonist, blocked the promoting roles of ETS1 in cells. To conclude, this study provided evidence that ETS1 suppresses miR-128 transcription to activate the following HOXA13/β-catenin axis, therefore promoting osteogenic differentiation ability of MC3T3-E1 cells. This finding may offer novel ideas for OP treatment.

CEA, CA 15-3, and miRNA expression as potential biomarkers in canine mammary tumors

The most often detected tumor in intact bitches is mammary tumors and represents a significant clinical problem throughout the world. Mammary neoplasms in canine have heterogeneous morphology, so the choice of the most appropriate biomarker is the biggest challenge in CMT detection. We performed a retrospective analysis and evaluated the canine cancer antigens and miRNA expression profiles as potential biomarkers. Sixty dogs based on histological examination divided into three groups, viz., dogs with a benign mammary tumor, malignant mammary tumor, and control/healthy. The CA 15-3 was found more sensitive than CEA but detection of both will increase sensitivity. miR-21 expression differed significantly in all three groups. miR-29b expression differed significantly between the control and benign group and control and malignant group. The miR-21 overexpression and miR-29b downregulation with CMT are associated with clinical stage and can be used as non-invasive diagnostic and prognostic biomarkers. Hence, evaluation of CA 15-3 along with CEA would be a non-invasive technique for detecting canine mammary tumors. Evaluation of deregulated circulating miR-21 could be a valuable prognostic marker for early detection of mammary tumors in canines while miR-29b can add sensitivity in the detection of the canine mammary tumors if evaluated with miR-21.

Overexpression of microRNA-29b inhibits epithelial-mesenchymal transition and angiogenesis of colorectal cancer through the ETV4/ERK/EGFR axis

BACKGROUND

Recent studies have reported the involvement of microRNA-29 (miR-29) family members in human cancers through their ability to regulate cellular functions. The present study investigated biological function of miR-29b in colorectal cancer (CRC).

METHODS

CRC tissues and adjacent normal tissues were collected and the expression of ETV4 and miR-29b in the tissues were identified. The relationship between ETV4 and miR-29b or ETV4 expression and the EGFR promoter was identified using dual-luciferase reporter gene and CHIP assays. The proliferation, invasion, migration, and apoptosis of CRC HCT116 cells were assayed using MTT assay, Scratch test, Transwell assay, and flow cytometry, respectively. Also, expression of epithelial-mesenchymal transition (EMT) markers, angiogenic factors, and vasculogenic mimicry formation were evaluated using RT-qPCR and Western blot.

RESULTS

ETV4 was upregulated, while miR-29b expression was decreased in CRC tissues. ETV4 was identified as a target gene of miR-29b, which in turn inactivated the ERK signaling pathway by targeting ETV4 and inhibiting EGFR transcription. Transfection with miR-29b mimic, siRNA-ETV4, or ERK signaling pathway inhibitor U0126 increased expression of E-cadherin and TSP-1, and CRC cell apoptosis, yet reduced expression of ERK1/2, MMP-2, MMP-9, Vimentin, and VEGF, as well as inhibiting EMT, angiogenesis, and CRC cell migration and invasion. The EMT, angiogenesis and cancer progression induced by miR-29b inhibitor were reversed by siRNA-mediated ETV4 silencing.

CONCLUSIONS

miR-29b suppresses angiogenesis and EMT in CRC via the ETV4/ERK/EGFR axis.

Cordycepin Resensitizes T24R2 Cisplatin-Resistant Human Bladder Cancer Cells to Cisplatin by Inactivating Ets-1 Dependent MDR1 Transcription

Tumor cell resistance to anti-cancer drugs is a major obstacle in tumor therapy. In this study, we investigated the mechanism of cordycepin-mediated resensitization to cisplatin in T24R2 cells, a T24-derived cell line. Treatment with cordycepin or cisplatin (2 μg/mL) alone failed to induce cell death in T24R2 cells, but combination treatment with these drugs significantly induced apoptosis through mitochondrial pathways, including depolarization of mitochondrial membranes, decrease in anti-apoptotic proteins Bcl-2, Bcl-xL, and Mcl-1, and increase in pro-apoptotic proteins Bak and Bax. High expression levels of MDR1 were the cause of cisplatin resistance in T24R2 cells, and cordycepin significantly reduced MDR1 expression through inhibition of MDR1 promoter activity. MDR1 promoter activity was dependent on transcription factor Ets-1 in T24R2 cells. Although correlation exists between MDR1 and Ets-1 expression in bladder cancer patients, active Ets-1, Thr38 phosphorylated form (pThr38), was critical to induce MDR1 expression. Cordycepin decreased pThr-38 Ets-1 levels and reduced MDR1 transcription, probably through its effects on PI3K signaling, inducing the resensitization of T24R2 cells to cisplatin. The results suggest that cordycepin effectively resensitizes cisplatin-resistant bladder cancer cells to cisplatin, thus serving as a potential strategy for treatment of cancer in patients with resistance to anti-cancer drugs.

Regulation of cisplatin-resistant head and neck squamous cell carcinoma by the SRC/ETS-1 signaling pathway

BACKGROUND

We investigated the role of the ETS-1 transcription factor in Head and Neck Squamous Cell Carcinoma (HNSCC) in multiple cisplatin-resistant HNSCC cell lines.

METHODS

We examined its molecular link with SRC and MEK/ERK pathways and determined the efficacy of either MEK/ERK inhibitor PD0325901 or SRC inhibitor Dasatinib on cisplatin-resistant HNSCC inhibition.

RESULTS

We found that ETS-1 protein expression levels in a majority of cisplatin-resistant HNSCC cell types were higher than those in their parental cisplatin sensitive partners. High ETS-1 expression was also found in patient-derived, cisplatin-resistant HNSCC cells. While ETS-1 knockdown inhibited cell proliferation, migration, and invasion, it could still re-sensitize cells to cisplatin treatment. Interestingly, previous studies have shown that MER/ERK pathways could regulate ETS-1 through its phosphorylation at threonine 38 (T38). Although almost all cisplatin-resistant HNSCC cells we tested showed higher ETS-1 phosphorylation levels at T38, we found that inhibition of MEK/ERK pathways with the MEK inhibitor PD0325901 did not block this phosphorylation. In addition, treatment of cisplatin-resistant HNSCC cells with the MEK inhibitor completely blocked ERK phosphorylation but did not re-sensitize cells to cisplatin treatment. Furthermore, we found that, consistent with ETS-1 increase, SRC phosphorylation dramatically increased in cisplatin-resistant HNSCC, and treatment of cells with the SRC inhibitor, Dasatinib, blocked SRC phosphorylation and decreased ETS-1 expression. Importantly, we showed that Dasatinib, as a single agent, significantly suppressed cell proliferation, migration, and invasion, in addition to survival.

CONCLUSIONS

Our results demonstrate that the SRC/ETS-1 pathway plays a crucial role and could be a key therapeutic target in cisplatin-resistant HNSCC treatment.

Next-Generation Sequencing Reveals the Role of Epigallocatechin-3-Gallate in Regulating Putative Novel and Known microRNAs Which Target the MAPK Pathway in Non-Small-Cell Lung Cancer A549 Cells

Lung cancer constitutes 85% of non-small cell lung cancer diagnosed cases. MicroRNAs are novel biomarkers that are capable of modulating multiple oncogenic pathways. Epigallocatechin-3-gallate (EGCG) is a potent chemopreventive and chemotherapeutic agent for cancer. We aimed to identify important known and putative novel microRNAs modulated by EGCG in A549 cells using next-generation sequencing and identify their gene targets. Preliminary analysis revealed an IC50 value of 309 μM with G0/G1 phase arrest at 40 μM EGCG treatment. MicroRNA profiling identified 115 known and 4 putative novel microRNAs in 40 μM and 134 known and 3 putative novel microRNAs in 100 μM EGCG-treated A549 cells. The top 10 up-expressed microRNAs were similar between the untreated control and EGCG-treated A549 cells. An up-expression in oncogenic microRNAs, which belong to broadly conserved seed families, were observed in untreated control and EGCG-treated A549 cells. Kyoto Encyclopedia of Genes and Genomes and Protein Analysis Through Evolutionary Relationships pathway analyses of the validated microRNA targeting genes strengthened the hypothesis that EGCG treatment can modulate microRNAs that play a significant role in the MAPK signaling pathway. Expression profile of microRNAs was validation by quantitative real time PCR of randomly selected microRNAs. This study identified signature microRNAs that can be used as novel biomarkers for lung cancer diagnosis.

p53-Suppressed Oncogene TET1 Prevents Cellular Aging in Lung Cancer

The role of transcriptional regulator ten-eleven translocation methylcytosine dioxygenease 1 (TET1) has not been well characterized in lung cancer. Here we show that TET1 is overexpressed in adenocarcinoma and squamous cell carcinomas. TET1 knockdown reduced cell growth in vitro and in vivo and induced transcriptome reprogramming independent of its demethylating activity to affect key cancer signaling pathways. Wild-type p53 bound the TET1 promoter to suppress transcription, while p53 transversion mutations were most strongly associated with high TET1 expression. Knockdown of TET1 in p53-mutant cell lines induced senescence through a program involving generalized genomic instability manifested by DNA single- and double-strand breaks and induction of p21 that was synergistic with cisplatin and doxorubicin. These data identify TET1 as an oncogene in lung cancer whose gain of function via loss of p53 may be exploited through targeted therapy-induced senescence. SIGNIFICANCE: These studies identify TET1 as an oncogene in lung cancer whose gain of function following loss of p53 may be exploited by targeted therapy-induced senescence.See related commentary by Kondo, p. 1751.

Honokiol induces apoptosis of lung squamous cell carcinoma by targeting FGF2-FGFR1 autocrine loop

Lung squamous cell carcinoma (SCC) accounts for a considerable proportion of lung cancer cases, but there is still a lack of effective therapies. FGFR1 amplification is generally considered a promising therapeutic target. Honokiol is a chemical compound that has been proven to be effective against various malignancies and whose analog has been reported to target the mitogen‐activated protein kinase family, members of a downstream signaling pathway of FGFR1. This was an explorative study to determine the mechanism of honokiol in lung SCC. We found that honokiol induced apoptosis and cell cycle arrest in lung SCC cell lines in a time‐ and dose‐dependent manner. Honokiol also restricted cell migration in lung SCC cell lines. Moreover, the expression of FGF2 and the activation of FGFR1 were both downregulated by honokiol. Pharmacological inhibition and siRNA knockdown of FGFR1 induced apoptosis in lung SCC cells. Our in vivo study indicated that honokiol could suppress the growth of xenograft tumors, and this effect was associated with the inhibition of the FGF2‐FGFR1 signaling pathway. In conclusion, honokiol induced cell apoptosis in lung SCC by targeting the FGF2‐FGFR1 autocrine loop.

MiR-532-5p suppresses renal cancer cell proliferation by disrupting the ETS1-mediated positive feedback loop with the KRAS-NAP1L1/P-ERK axis

Background

Despite the fact that miRNAs play pivotal roles in various human malignancies, their molecular mechanisms influencing RCC are poorly understood.

Methods

The expression of miRNAs from RCC and paired normal renal specimens was analysed by a combined computational and experimental approach using two published datasets and qRT-PCR assays. The functional role of these miRNAs was further identified by overexpression and inhibition assays in vivo and in vitro. Western blots, luciferase assays, and chromatin immunoprecipitation were performed to investigate the potential mechanisms of these miRNAs.

Results

Bioinformatics analysis and qRT-PCR revealed that miR-532-5p was one of the most heavily downregulated miRNAs. Overexpression of miR-532-5p inhibited RCC cell proliferation, while knockdown of miR-532-5p promoted cell proliferation. Mechanistic analyses indicated that miR-532-5p directly targets KRAS and NAP1L1. Interestingly, ETS1 suppressed the transcription of miR-532-5p by directly binding a special region of its promoter. Moreover, high levels of ETS1, as an oncogene in RCC, were significantly associated with poor survival in a large cohort of RCC specimens.

Conclusions

Our work presents a road map for the prediction and validation of a miR-532-5p/KRAS-NAP1L1/P-ERK/ETS1 axis feedback loop regulating cell proliferation, which could potentially provide better therapeutic avenues for treating RCC.

miR-29 regulates Tet1 expression and contributes to early differentiation of mouse ESCs

The ten-eleven translocation-1 (Tet1), which converts 5-methylcytosine (5mC) to 5-hydroxymethycytosine (5hmC), plays important roles in many important biological processes, such as mouse embryonic stem cells (ESCs) maintenance. However, the mechanisms for Tet-1 regulation remain largely unknown. Here we showed that miR-29 family (miR-29a, miR-29b and miR-29c) can directly repress Tet1 expression. We found that Tet1 was highly expressed and 5hmC was presented at relatively high levels in mouse ESCs, but the levels of both Tet1 and 5hmC were reduced during the early differentiation of ESCs. On the contrary, miR-29 level was increased in this process. ESCs stably transfecting with miR-29 precursors showed lower levels of Tet1 protein and 5hmC. Furthermore, we demonstrated that miR-29 overexpression selectively affected cell lineage markers and skewed ESC differentiation, which was similar in Tet1 knockdown ESCs. Our results indicate that miR-29 is a direct regulator of Tet1 in mouse ESCs.

Clinical significance of high expression of miR-452-5p in lung squamous cell carcinoma

The role of microRNA (miRNA)-452-5p in lung squamous cell carcinoma (LUSC) remains unclear. Therefore, the present systematic study was performed to investigate the clinical significance and the rudimentary mechanism of the function of miR-452-5p in LUSC. The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were utilized to confirm the expression level and clinical value of miR-452-5p in LUSC. Using online databases and bioinformatic software, gene ontology (GO), pathway and protein-protein interaction (PPI) analyses of miR-452-5p target genes were performed to examine the molecular mechanism of miR-452-5p. The association between the expression of miR-452-5p and that of its hub genes was verified using TCGA. Based on TCGA data on 387 clinical specimens, the expression of miR-452-5p in LUSC was significantly increased compared with adjacent lung tissues (7.1525±1.39063 vs. 6.0885±0.35298; P<0.001). The expression levels of miR-452-5p were significantly correlated with age (P=0.001) and tumor-node metastasis stage (P=0.028). Furthermore, the increased expression of miR-452-5p in LUSC compared with non-cancerous tissue [standard mean deviation (SMD), 0.372; 95% confidence interval (CI), 0.020–0.724; z=2.07; P=0.038] was validated by a meta-analysis of 720 clinical samples. The GO and pathway analyses revealed that miR-452-5p target genes were mainly enriched in the ‘regulation of transcription’, ‘nucleoplasm’, ‘protein binding’ and ‘cell cycle’ pathways. A total of 10 hub genes were identified by PPI analysis, and 5 hub genes (SMAD4, SMAD2, CDKN1B, YWHAE and YWHAB) were significantly enriched in the ‘cell cycle’ pathway. The expression of CDKN1B was negatively correlated with miR-452-5p (P=0.003). It was concluded that miR-452-5p may serve an essential role in the occurrence and progression of LUSC by targeting CDKN1B, which is involved in the cell cycle.

MiR-29b/TET1/ZEB2 signaling axis regulates metastatic properties and epithelial-mesenchymal transition in breast cancer cells

MiR-29b has been reported to be both a suppressor and a promoter in breast cancer (BC) cells proliferation and metastasis. Significant efforts have been made to explain the seemingly contradictory effects of miR-29b on BC, but no answer has yet been clearly verified. In this study, we overexpressed and knocked down miR-29b in BC cell lines, modulated expression of its downstream target gene TET1 and downregulated a downstream target gene of TET1, ZEB2, to explore the regulatory mechanism of miR-29b in BC cell proliferation, migration and epithelial-mesenchymal transition (EMT). Our results showed lower expression of miR-29b in BC samples and cell lines. Functional assays showed that miR-29b overexpression resulted in a higher cell proliferation, greater colony formation, higher migration rate and EMT. A dual luciferase assay identified TET1 as a direct target of miR-29b. As the promoting effects of miR-29b in the proliferation and metastasis of MDA-MB-231 and MCF-7, knockdown of TET1 also led to increased proliferation, colony formation, invasion and EMT. Further, we found that TET1 bound to the promoter of ZEB2, and siTET1 enhanced ZEB2 expression. Disruption of ZEB2 expression inhibited BC cells proliferation, colony formation and invasion. Our results establish the miR-29b/TET1/ZEB2 pathway in BC cell proliferation, migration and provide a theoretical basis for further research on the molecular mechanisms and new clinical treatments for BC.

KRAS-driven miR-29b expression is required for tumor suppressor gene silencing

KRAS activation drives DNA methylation and silencing of specific tumor suppressor genes (TSGs). We previously showed that the ERK pathway induces transcriptional repression of TET1, which results in conversion of TSG promoters from a hydroxymethylated, active state to a hypermethylated and silenced state. Here we identified miR-29b as a KRAS-induced molecule that represses TET1 expression. In KRAS-transformed cells, ectopic miR-29b inhibition restores expression of TET1, thereby reactivating TSGs by reducing methylation and restoring hydroxymethylation. Mining gene expression data of lung cancer cell lines identified additional TSGs suppressed by KRAS signaling whose expression was restored by inhibition of miR-29b and re-expression of TET1. Because KRAS changes TSG promoters from hydroxymethylated to hypermethylated with miR-29b-dependent silencing of TET1, we demonstrate a model in which DNMT1 is present on target promoters prior to KRAS transformation. In addition, we propose miR-29b as a potential circulating biomarker and target for rational treatment of specific malignancies.

Significance of microRNAs in Androgen Signaling and Prostate Cancer Progression

The androgen receptor (AR) plays important roles in prostate cancer development and prostate tumor growth. After binding to androgens, AR functions as a nuclear receptor and translocates to the nucleus to bind to specific AR-binding sites (ARBSs). AR regulates epigenetic factor recruitments to activate its downstream signaling. Although androgen deprivation therapy (ADT) is initially useful for prostate cancer patients, most patients eventually show resistance with hormone-refractory prostate cancers (HRPCs) or castration-resistant prostate cancers (CRPCs). Thus, new therapeutic strategies targeting HRPCs/CRPCs should be very important for clinical medicine as well as prostate cancer biology. Past studies have shown that mechanisms such as AR overexpression, hypersensitivity, variants and reprograming are responsible for developing HRPCs/CRPCs. These findings suggest that AR target genes will be major key factors. In this review article, we focus mainly on the androgen-regulated microRNAs (miRNAs) to summarize the contribution of miRNA-mediated pathways for prostate cancer progression.

Multiple Functions of Ten-eleven Translocation 1 during Tumorigenesis

Objective:

Aberrant expression of ten-eleven translocation 1 (TET1) plays a critical role in tumor development and progression. We systematically summarized the latest research progress on the role and mechanisms of TET1 in cancer biology.

Data Sources:

Relevant articles published in English from 1980 to April 2016 were selected from the PubMed database. The terms “ten-eleven translocation 1,” “5mC,” “5hmC,” “microRNA,” “hypoxia,” and “embryonic stem cell” were used for the search.

Study Selection:

Articles focusing on the role and mechanism of TET1 in tumor were reviewed, including clinical and basic research articles.

Results:

TET proteins, the key enzymes converting 5-methylcytosine to 5-hydroxymethylcytosine, play vital roles in DNA demethylation regulation. Recent studies have shown that loss of TET1 is associated with tumorigenesis and can be used as a potential biomarker for cancer therapy, which indicates that TET1 serves as tumor suppressor gene. Moreover, besides its dioxygenase activity, TET1 could induce epithelial-mesenchymal transition and act as a coactivator to regulate gene transcription, such as developmental regulator in embryonic stem cells (ESCs) and hypoxia-responsive gene in cancer. The regulation of TET1 is also correlated with microRNA in a posttranscriptional modification process. Hence, it is complex but critical to comprehend the mechanisms of TET1 in the biology of ESCs and cancer.

Conclusions:

TET1 not only serves as a demethylation enzyme but also plays multiple roles during tumorigenesis and progression. More studies should be carried out to elucidate the exact mechanisms of TET1 and its associations with cancer before considering it as a therapeutic tool.