TET1 partially mediates HDAC inhibitor-induced suppression of breast cancer invasion

TET Enzymes and 5hmC Levels in Carcinogenesis and Progression of Breast Cancer: Potential Therapeutic Targets

Breast Cancer (BC) was the most common female cancer in incidence and mortality worldwide in 2020. Similarly, BC was the top female cancer in the USA in 2022. Risk factors include earlier age at menarche, oral contraceptive use, hormone replacement therapy, high body mass index, and mutations in BRCA1/2 genes, among others. BC is classified into Luminal A, Luminal B, HER2-like, and Basal-like subtypes. These BC subtypes present differences in gene expression signatures, which can impact clinical behavior, treatment response, aggressiveness, metastasis, and survival of patients. Therefore, it is necessary to understand the epigenetic molecular mechanism of transcriptional regulation in BC, such as DNA demethylation. Ten-Eleven Translocation (TET) enzymes catalyze the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) on DNA, which in turn inhibits or promotes the gene expression. Interestingly, the expression of TET enzymes as well as the levels of the 5hmC epigenetic mark are altered in several types of human cancers, including BC. Several studies have demonstrated that TET enzymes and 5hmC play a key role in the regulation of gene expression in BC, directly (dependent or independent of DNA de-methylation) or indirectly (via interaction with other proteins such as transcription factors). In this review, we describe our recent understanding of the regulatory and physiological function of the TET enzymes, as well as their potential role as biomarkers in BC biology.

MDM2 Antagonist Nutlin-3 Stimulates Global DNA Hydroxymethylation by Enhancing p53-TET1 Signaling Axis

DNA hydroxymethylation is involved in many biological processes, including nuclear reprogramming, embryonic development, and tumor suppression. In this study, we report that an anticancer agent, nutlin-3, selectively stimulates global DNA hydroxymethylation in TP53 wild-type cancer cells as manifested by the elevation of 5-hydroxymethylcytosine (5hmC) in genomic DNA. In contrast, nutlin 3 fails to enhance DNA hydroxymethylation in TP53-mutated cancer cells. Consistently, nutlin-3 as a MDM2 antagonist only activates wild-type but not mutated TP53. Furthermore, nutlin-3 does not alter the expression of TET1 but slightly reduces the expression of TET2 and TET3 proteins. These TET family proteins are responsible for converting 5-methylcytosine (5mC) to 5hmC. Interestingly, TET1 knockdown could significantly block the nutlin-3-induced DNA hydroxymethylation as well as TP53 and P21 activation. Immunoprecipitation analysis supports that p53 strongly interacts with TET1 proteins. These results suggest that nutlin-3 activates TP53 and promotes p53-TET1 interaction. As positive feedback, the p53-TET1 interaction further enhances p53 activation and promotes apoptosis. Collectively, we demonstrate that nutlin-3 stimulates DNA hydroxymethylation and apoptosis via a positive feedback mechanism.

Targeted DNA Demethylation: Vectors, Effectors and Perspectives

Aberrant DNA hypermethylation at regulatory cis-elements of particular genes is seen in a plethora of pathological conditions including cardiovascular, neurological, immunological, gastrointestinal and renal diseases, as well as in cancer, diabetes and others. Thus, approaches for experimental and therapeutic DNA demethylation have a great potential to demonstrate mechanistic importance, and even causality of epigenetic alterations, and may open novel avenues to epigenetic cures. However, existing methods based on DNA methyltransferase inhibitors that elicit genome-wide demethylation are not suitable for treatment of diseases with specific epimutations and provide a limited experimental value. Therefore, gene-specific epigenetic editing is a critical approach for epigenetic re-activation of silenced genes. Site-specific demethylation can be achieved by utilizing sequence-dependent DNA-binding molecules such as zinc finger protein array (ZFA), transcription activator-like effector (TALE) and clustered regularly interspaced short palindromic repeat-associated dead Cas9 (CRISPR/dCas9). Synthetic proteins, where these DNA-binding domains are fused with the DNA demethylases such as ten-eleven translocation (Tet) and thymine DNA glycosylase (TDG) enzymes, successfully induced or enhanced transcriptional responsiveness at targeted loci. However, a number of challenges, including the dependence on transgenesis for delivery of the fusion constructs, remain issues to be solved. In this review, we detail current and potential approaches to gene-specific DNA demethylation as a novel epigenetic editing-based therapeutic strategy.

Δ9-Tetrahydrocannabinol stimulation of estrogen receptor-positive MCF-7 breast cancer cell migration: Interfering interaction with the estrogenic milieu

PURPOSE

The effects of extended Δ⁹-tetrahydrocannabinol (Δ⁹-THC) exposure on estrogen receptor-positive human breast cancer MCF-7 cells have been investigated; however, the effects of Δ⁹-THC exposure for a shorter duration remain unclear. In this study, we sought to study whether Δ⁹-THC stimulates the migration of MCF-7 cells under both estrogenic and estrogen-deprived conditions over a short period (approximately 6 h).

METHODS

MCF-7 cells were treated with Δ⁹-THC under estrogenic or estrogen-deprived conditions, and cell migration was subsequently analyzed.

RESULTS

Δ⁹-THC-stimulated migration of MCF-7 cells 6 h after exposure was only observed in the estrogen-deprived condition. However, Δ⁹-THC-mediated migration was counteracted under estrogenic conditions without affecting cell proliferation and estrogen receptor expression during this period.

CONCLUSIONS

Δ⁹-THC can stimulate MCF-7 cell migration under estrogen-deprived conditions; however, there is an interfering interaction between Δ⁹-THC and the estrogenic milieu that influences the migration of MCF-7 cells.

miR-646/TET1 mediated demethylation of IRX1 promoter upregulates HIST2H2BE and promotes the progression of invasive ductal carcinoma

BACKGROUND

This study aimed to explore role of miR-646 in breast IDC.

METHODS

miR-646, TET1, IRX1, and HIST2H2BE expression was detected by RT-qPCR and/or Western blot analysis. The methylation status of IRX1 promoter region was evaluated by methylation specific PCR. ChIP assay was used to determine the enrichment of TET1 at IRX1 promoter region. Loss- and gain-of functions were performed to determine the roles of miR-646, TET1, IRX1, and HIST2H2BE in cell proliferation, migration, invasion, and apoptosis. The tumor growth, volume, weight, and apoptosis status were measured.

RESULTS

miR-646 was upregulated while TET1 was downregulated in IDC tissues. miR-646 targeted TET1. Downregulated TET1 impairs demethylation of IRX1 promoter region resulting in reduced expression of IRX1, which subsequently leads to upregulation of HIST2H2BE in IDC. Consequently, elevated HIST2H2BE promotes progression of IDC.

CONCLUSION

Our study has demonstrated that miR-646 facilitates the tumorigenesis of IDC via regulating TET1/IRX1/HIST2H2BE axis.

Downregulation of TET1 Promotes Bladder Cancer Cell Proliferation and Invasion by Reducing DNA Hydroxymethylation of AJAP1

Ten-eleven translocation 1 (TET1) is a member of methylcytosine dioxygenase, which catalyzes 5-methylcytosine (5 mC) to 5-hydroxymethylcytosine (5 hmC) to promote the demethylation process. The dysregulated TET1 protein and 5 hmC level were reported to either suppress or promote carcinogenesis in a cancer type-dependent manner. Currently, the role of TET1 in the development of urinary bladder cancer (UBC) and its underlying molecular mechanisms remain unclear. Herein, we found that TET1 expression was downregulated in UBC specimens compared with normal urothelium and was inversely related to tumor stage and grade and overall survival, suggesting its negative association with UBC progression. TET1 silencing in UBC cells increased cell proliferation and invasiveness while the ectopic expression of wild-type TET1-CD, but not its enzymatic inactive mutant, reversed these effects and suppressed tumorigenicity in vivo. In addition, as a direct regulator of TET1 activity, vitamin C treatment increased 5 hmC level and inhibited the anchorage-independent growth and tumorigenicity of UBC cells. Furthermore, we found that TET1 maintained the hypomethylation in the promoter of the AJAP1 gene, which codes for adherens junction-associated protein 1. The downregulation of AJAP1 reversed TET1-CD-induced nuclear translocation of β-catenin, thus inhibiting the expression of its downstream genes. In human UBC specimens, AJAP1 is frequently downregulated and positively associated with TET1. Notably, low expression levels of both TET1 and AJAP1 predict poor prognosis in UBC patients. In conclusion, we found that the frequently downregulated TET1 level reduces the hydroxymethylation of AJAP1 promoter and subsequently activates β-catenin signaling to promote UBC development. The downregulation of both TET1 and AJAP1 might be a promising prognostic biomarker for UBC patients.

Hydroxyurea promotes TET1 expression and induces apoptosis in osteosarcoma cells

Ten-eleven translocation (TET) proteins are abnormally expressed in various cancers. Osteosarcoma cells were treated with hydroxyurea to investigate the expression pattern of TET proteins in these cells. The expression of TET1 was increased in U2OS cells after treatment with hydroxyurea. In addition, hydroxyurea increased cell apoptosis and altered the cell cycle. TET proteins catalyze the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC); therefore, 5mC and 5hmC levels were evaluated. Increased 5hmC levels were observed after the hydroxyurea treatment. Experiments examining cell apoptosis and the cell cycle after knockdown and overexpression of TET1 were conducted to further investigate whether TET1 expression affected cell growth. The overexpression of TET1 increased cell apoptosis and inhibited cell growth. Taken together, TET1 expression regulated proliferation and apoptosis in U2OS cells, changes that were associated with 5hmC levels.

TET1 suppresses colon cancer proliferation by impairing β-catenin signal pathway

The function of ten-eleven translocation methylcytosine dioxygenase 1 (TET1) in cancer is background dependent and may be involved in the initial step of active DNA demethylation, while there is little research to decipher the role of TET1 in DNA methylation-sensitive colon cancer. Downregulated TET1 expression assayed by quantitative real-time PCR (qRT-PCR) was observed in both colon cancer samples and cancer cell lines of HT29, HCT116, and SW48. Such downregulation could promote colon cancer cells proliferation as indicated by the fact that shTET1 could increase the viability of HT29 and HCT116 cells determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide and cell count assay accompanied with upregulation of β-catenin (CTNNB1) and WNT luciferase activity, which was further confirmed as shTET1 could increase the tumor volume and tumor weight, and decrease the body weight in HT29 cells inoculated BALB/C nude mice. The CTNNB1 transfection could rescue the cell growth diminished by normal expression of TET1. shTET1 could promote axis inhibition protein1 (AXIN1) expression and the cell proliferation effect induced by TET1 short hairpin RNA was attenuated by co-inhibition of AXIN1. All of these indicate that TET1 can suppress colon cancer proliferation and the inhibition of the β-catenin pathway is AXIN1 dependent.

The effect of sodium butyrate and cisplatin on expression of EMT markers

Histone modifications play a key role in the epigenetic regulation of gene transcription in cancer cells. Histone acetylations are regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs are increased in ovarian carcinomas and they are involved in carcinogenesis and resistance to chemotherapeutic agents. In our study we investigated anticancer effect of HDAC inhibitor sodium butyrate (NaBu) on cisplatin-sensitive and cisplatin-resistant ovarian cell lines A2780 and A2780cis. A2780 and A2780cis were treated with NaBu alone or in combination with cisplatin (CP). NaBu inhibited the growth of both cell lines and enhanced cytotoxic effect of CP. Exposure to NaBu for 24 h induced cell cycle arrest. The expressions of EMT-related genes and proteins were further investigated by qPCR and western blot analysis. Loss of E-cadherin has been shown to be crucial in ovarian cancer development. We found that NaBu dramatically induce expression of E-cadherin gene (CDH1) and protein levels in A2780 and A2780cis. We investigated correlation between transcription and methylation of CDH1gene. Methylation level analysis in 32 CpG sites in CDH1 gene (promoter/exon1 regions) was performed using bisulfite NGS (Next Generation Sequencing). We found that cisplatin-resistant cell line A2780cis cells differ from their cisplatin-sensitive counterparts in the CDH1 methylation. Methylation in A2780cis cells is elevated compared to A2780. However, NaBu-induced expression of CDH1 was not accompanied by CDH1 demethylation. NaBu treatment induced changes in expression of EMT-related genes and proteins. Interestingly E-cadherin zinc finger transcriptional repressor SNAIL1 was upregulated in both cell lines. Mesenchymal marker vimentin was downregulated. Matrix metalloproteases (MMPs) are necessary for pericellular proteolysis and facilitate migration and invasion of tumour cells. NaBu induced mRNA expression of MMPs, mild changes in activities of gelatinases MMP2 and MMP9 were detected. Our data demonstrate that NaBu sensitizes cisplatin-resistant ovarian cancer cells, re-established E-cadherin expression, but it was not able to reverse the EMT phenotype completely.

TET1 exerts its anti-tumor functions via demethylating DACT2 and SFRP2 to antagonize Wnt/β-catenin signaling pathway in nasopharyngeal carcinoma cells

BACKGROUND

TET1 is a tumor suppressor gene (TSG) that codes for ten-eleven translocation methyl cytosine dioxygenase1 (TET1) catalyzing the conversion of 5-methylcytosine to 5-hydroxy methyl cytosine as a first step of TSG demethylation. Its hypermethylation has been associated with cancer pathogenesis. However, whether TET1 plays any role in nasopharyngeal carcinoma (NPC) remains unclear. This study investigated the expression and methylation of TET1 in NPC and confirmed its role and mechanism as a TSG.

RESULTS

TET1 expression was downregulated in NPC tissues compared with nasal septum deviation tissues. Demethylation of TET1 in HONE1 and HNE1 cells restored its expression with downregulated methylation, implying that TET1 was silenced by promoter hypermethylation. Ectopic expression of TET1 suppressed the growth of NPC cells, induced apoptosis, arrested cell division in G0/G1 phase, and inhibited cell migration and invasion, confirming TET1 TSG activity. TET1 decreased the expression of nuclear β-catenin and downstream target genes. Furthermore, TET1 could cause Wnt antagonists (DACT2, SFRP2) promoter demethylation and restore its expression in NPC cells.

CONCLUSIONS

Collectively, we conclude that TET1 exerts its anti-tumor functions in NPC cells by suppressing Wnt/β-catenin signaling via demethylation of Wnt antagonists (DACT2 and SFRP2).

Immunity drives TET1 regulation in cancer through NF-κB

Ten-eleven translocation enzymes (TET1, TET2, and TET3), which induce DNA demethylation and gene regulation by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), are often down-regulated in cancer. We uncover, in basal-like breast cancer (BLBC), genome-wide 5hmC changes related to TET1 regulation. We further demonstrate that TET1 repression is associated with high expression of immune markers and high infiltration by immune cells. We identify in BLBC tissues an anticorrelation between TET1 expression and the major immunoregulator family nuclear factor κB (NF-κB). In vitro and in mice, TET1 is down-regulated in breast cancer cells upon NF-κB activation through binding of p65 to its consensus sequence in the TET1 promoter. We lastly show that these findings extend to other cancer types, including melanoma, lung, and thyroid cancers. Together, our data suggest a novel mode of regulation for TET1 in cancer and highlight a new paradigm in which the immune system can influence cancer cell epigenetics.

miR-27a-3p promotes the malignant phenotypes of osteosarcoma by targeting ten-eleven translocation 1

Osteosarcoma has become one of the most common primary malignant tumors affecting children and adolescents. Although increasing evidence has indicated that microRNAs (miRNAs or miRs) play important roles in the development of osteosarcoma, the expression of miR‑27a‑3p and its effects on osteosarcoma are not yet fully understood. In the present study, our data demonstrated that the expression of miR‑27a‑3p in osteosarcoma cell lines was significantly higher than that in the normal human osteoblastic cell line, hFOB 1.19 cell (P<0.01). In order to explore the role of miR‑27a‑3p in the development and progression of osteosarcoma, the expression of miR‑27a‑3p was inhibited by transfection of the MG-63 cells with miR‑27a‑3p inhibitor. The results revealed that the cell proliferative ability significantly decreased (P<0.01), the number of apoptotic cells significantly increased (P<0.01) and the number of cells passing through the Transwell membrane was significantly reduced in the group transfected with the miR‑27a‑3p inhibitor (P<0.01). At the same time, the expression of E-cadherin and α-catenin was significantly upregulated (P<0.01), while the expression of vimentin was significantly downregulated in the group transfected with the miR‑27a‑3p inhibitor (P<0.01). Our results also revealed that the mRNA expression of ten-eleven translocation 1 (TET1) in the osteosarcoma cells was significantly downregulated compared with that in the hFOB 1.19 cells (P<0.01). Luciferase reporter system analysis indicated that miR‑27a‑3p recognized the TET1 3'-UTR. The protein expression of TET1 significantly increased in the group transfected with the miR‑27a‑3p inhibitor. The results from CCK-8 assay, flow cytometric assay and Transwell invasion analysis revealed that TET1 knockdown inhibited the biological effects induced by the downregulation of miR‑27a‑3p. Taken together, the findings of this study indicate that miR‑27a‑3p is upregulated, while TET1 is downregulated in human osteosarcoma cells. miR‑27a‑3p inhibition suppresses the proliferation and invasion of osteosarcoma cells, and promotes cell apoptosis via the negative regulation of TET1. miR‑27a‑3p/TET1 may thus be a potential target for the treatment of osteosarcoma.

Overexpression of Sirt6 is a novel biomarker of malignant human colon carcinoma

Sirt family has been reported playing a significant role in the cancer development, especial its deacetylase activity plays a key function, but whether SIRT6 plays a role in mediating tumor epithelial-mesenchymal transition (EMT) and metastasis in colon cancer has not been explored. Here, the mass spectrometry and co-immunoprecipitation assays were utilized to detect that SIRT6 was physically associated with transcription factor snail. Most important, HCT116 cells transfected with SIRT6 shRNA reversed EMT, while increased the expression of TET1, and the HCT116 cells transfected with SIRT6 displayed the contrary tendency. Transwell invasion assay, soft agar assay, as well as colony formation together showed that SIRT6 promoted cell EMT and tumorigenesis in vitro. We also found SIRT6 is a reader of snail. ChIP as well as qChIP suggested H3K9 binding on the promoter of TET1 dependent on SIRT6. SIRT6 promoted EMT process through two different ways, one is as a reader of snail, and other way was the suppression of TET1 transcription. These two ways are all dependent on its H3K9 deacetylase activity. Further, patient samples collected showed that SIRT6 was significantly increased in colon cancer samples, and its higher expression was correlated with poor prognosis, worse overall survivals. Together, our experiments revealed the mechanism for SIRT6 in facilitating tumorigenesis and metastasis of colon cancer cells, suggesting that SIRT6 might be a potential therapeutic target for treating colon cancer.

Ten-eleven translocation 1 functions as a mediator of SOD3 expression in human lung cancer A549 cells

Superoxide dismutase (SOD) 3, one of the SOD isozymes, plays a pivotal role in extracellular redox homeostasis. The expression of SOD3 is regulated by epigenetics in human lung cancer A549 cells and human monocytic THP-1 cells; however, the molecular mechanisms governing SOD3 expression have not been elucidated in detail. Ten-eleven translocation (TET), a dioxygenase of 5-methylcytosine (5mC), plays a central role in DNA demethylation processes and induces target gene expression. In the present study, TET1 expression was abundant in U937 cells, but its expression was weakly expressed in A549 and THP-1 cells. These results are consistent with the expression pattern of SOD3 and its DNA methylation status in these cells. Moreover, above relationship was also observed in human breast cancer cells, human prostate cancer cells, and human skin fibroblasts. The overexpression of TET1-catalytic domain (TET1-CD) induced the expression of SOD3 in A549 cells, and this was accompanied by the direct binding of TET1-CD to the SOD3 promoter region. Furthermore, in TET1-CD-transfected A549 cells, the level of 5-hydroxymethylcytosine within that region was significantly increased, whereas the level of 5mC was decreased. The results of the present study demonstrate that TET1 might function as one of the key molecules in SOD3 expression through its 5mC hydroxylation in A549 cells.

Dissecting bipolar disorder complexity through epigenomic approach

In recent years, numerous studies of gene regulation mechanisms have emerged in neuroscience. Epigenetic modifications, described as heritable but reversible changes, include DNA methylation, DNA hydroxymethylation, histone modifications and noncoding RNAs. The pathogenesis of psychiatric disorders, such as bipolar disorder, may be ascribed to a complex gene-environment interaction (G × E) model, linking the genome, environmental factors and epigenetic marks. Both the high complexity and the high heritability of bipolar disorder make it a compelling candidate for neurobiological analyses beyond DNA sequencing. Questions that are being raised in this review are the precise phenotype of the disorder in question, and also the trait versus state debate and how these concepts are being implemented in a variety of study designs.

Oncogenic EGFR Represses the TET1 DNA Demethylase to Induce Silencing of Tumor Suppressors in Cancer Cells

Oncogene-induced DNA methylation-mediated transcriptional silencing of tumor suppressors frequently occurs in cancer, but the mechanism and functional role of this silencing in oncogenesis are not fully understood. Here, we show that oncogenic epidermal growth factor receptor (EGFR) induces silencing of multiple unrelated tumor suppressors in lung adenocarcinomas and glioblastomas by inhibiting the DNA demethylase TET oncogene family member 1 (TET1) via the C/EBPα transcription factor. After oncogenic EGFR inhibition, TET1 binds to tumor suppressor promoters and induces their re-expression through active DNA demethylation. Ectopic expression of TET1 potently inhibits lung and glioblastoma tumor growth, and TET1 knockdown confers resistance to EGFR inhibitors in lung cancer cells. Lung cancer samples exhibited reduced TET1 expression or TET1 cytoplasmic localization in the majority of cases. Collectively, these results identify a conserved pathway of oncogenic EGFR-induced DNA methylation-mediated transcriptional silencing of tumor suppressors that may have therapeutic benefits for oncogenic EGFR-mediated lung cancers and glioblastomas.

Selective non-zinc binding MMP-2 inhibitors: Novel benzamide Ilomastat analogs with anti-tumor metastasis

Novel Ilomastat analogs with substituted benzamide groups, instead of hydroxamic acid groups, were designed, synthesized and evaluated against MMP-2 and MMP-9. Among these analogs, the most potent compound 10a exhibited potent inhibitory activity against MMP-2 with IC50 value of 0.19 nM, which is 5 times more potent than that of Ilomastat (IC50=0.94 nM). Importantly, 10a exhibited more than 8300 fold selectivity for MMP-2 versus MMP-9 (IC50=1.58 μM). Molecular docking studies showed that 10a bond to the catalytic active pocket of MMP-2 by a non-zinc-chelating mechanism which was different from that of Ilomastat. Furthermore, the invasion assay showed that 10a was effective in reducing HEY cells invasion at 84.6% in 50 μM concentration. For 10a, the pharmacokinetic properties had been improved and especially the more desirable t1/2z was achieved compared with these of the lead compound Ilomastat.

Forkhead box protein k1 recruits TET1 to act as a tumor suppressor and is associated with MRI detection

OBJECTIVE

Today, more and more evidence suggests that Foxk proteins (Foxk1 and Foxk2) work as transcriptional repressors in different kinds of cancer, but whether Foxk1 has a role in mediating tumorigenesis in breast cancer, the evidence is rare.

METHODS

MCF-7 cells transfected with shFoxk1 displayed a mesenchymal morphology and reduced the expression of E-cadherin, and increased the expression of N-cadherin. Transwell invasion assay and living imaging assay show that the overexpression of Foxk1 could inhibit metastasis in vitro and in vivo. Ribonucleic acid sequencing revealed that the knockdown of Foxk1 resulted in the up-regulation of different oncogenes, which was implicated in metastasis and tumor angiopoiesis. Quantitative chromatin immunoprecipitation, chromatin immunoprecipitation and Luciferase reporter assays suggested that Foxk1 could bind to the promoter of epithelial-mesenchymal transition inducer Twist and vascular endothelial growth factor, VEGF. Mass Spectrometry, co-immunoprecipitation assays and glutathione-S-transferase pull-down assay detected that Foxk1 was physically associated with Ten-eleven translocation 1, TET1, in vivo and in vitro.

RESULTS

We reported that the mean expression level of Foxk1 in breast cancer was significantly lower than the adjacent noncarcinoma tissue. The higher Foxk1 expression was associated with better prognosis. Endothelial tube formation assays indicated that Foxk1 might regulate breast cancer angiogenesis through transcriptional repression of vascular endothelial growth factor. Furthermore, in vivo magnetic resonance imaging revealed the overexpression of Foxk1 could enhance the detection of the tumors. Further, a strong negative correlation was observed between Foxk1 and Twsit or between Foxk1 and vascular endothelial growth factor, and the higher Foxk1 expression is correlated with better over all survivals and better relapse-free survivals.

CONCLUSIONS

Together, our data indicated the function of Foxk1 as a tumor suppressor in facilitating angiogenesis and metastasis in breast cancer.

miR-29b is an indicator of prognosis in breast cancer patients

MicroRNA-29b (miR-29b) targets numerous important genes that mediate carcinogenesis and tumor development in breast cancer in vitro and in vivo. The aim of the present study was to determine the clinical significance of miR-29b expression in primary breast cancer patients. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) of miR-29b and certain target genes of miR-29b, such as DNA methyltransferase 3A (DNMT3A), ten-eleven translocation 1 (TET1) and thymine DNA glycosylase (TDG), was performed in 94 primary breast cancer samples. Low expression of miR-29b in primary tumors was significantly associated with poorer disease-free survival (DFS) (P=0.0075) and overall survival (OS) (p=0.0012). Multivariate analysis indicated that miR-29b expression was an independent prognostic factor for OS [relative risk=15.6 (2.33-348), P=0.0026]. In addition, a significant inverse correlation was identified between the expression levels of DNMT3A and miR-29b in estrogen receptor-positive breast cancer patients (P=0.027). To the best of our knowledge, this is the first study to investigate the clinicopathological significance of miR-29b in breast cancer cases and miR-29b is shown to act as a tumor suppressive microRNA in breast cancer and as a potential marker for recurrence and metastasis in breast cancer patients.