ATBF1 is a potential diagnostic marker of histological grade and functions via WNT5A in breast cancer

BACKGROUND

Histological grade has been demonstrated to be an important factor of breast cancer outcome and is associated with cell differentiation and is currently being evaluated via H&E-stained sections. Molecular biomarkers are essential to improve the accuracy of histological grading. ATBF1, a large transcription factor, has been considered a tumor suppressor gene with frequent mutations or deletions in multiple cancers. In breast cancer, ATBF1 was reported to function in cell differentiation and mammary development. However, its role in the clinic has rarely been reported.

METHODS

Breast cancer tissues (BCTs) and adjacent noncancerous tissues (ANCTs) were collected to analyze the expression of ATBF1 at the mRNA and protein levels. Three anti-ATBF1 antibodies recognizing independent peptides of ATBF1 (N-terminal end, middle region and C-terminal end) were applied for IHC staining. Small interfering RNA (siRNA) was used to silence ATBF1 expression and to investigate the roles of ATBF1 in MCF7 cells. Microarrays were introduced to analyze the differentially expressed genes, enriched GO terms and KEGG terms regulated by ATBF1 and its potential downstream genes, which were further confirmed in vitro and in clinical samples.

RESULTS

The expression of ATBF1 was reduced in BCTs at both the mRNA and protein levels compared with that in ANCTs. ATBF1 protein was predominantly localized in the nucleus of ANCTs but in the cytoplasm of BCTs. Both the mRNA and protein levels of ATBF1 were significantly correlated with histological grade. Consistently, knockdown of ATBF1 increased stemness marker expression and reduced differentiation markers in vitro. Further analysis identified WNT5A as an essential downstream gene of ATBF1 in breast cancer cells. Treatment of WNT5A disrupted cell proliferation induced by ATBF1 silencing. In BCTs, a significant correlation was observed between the expression of WNT5A and ATBF1.

CONCLUSION

The results indicated that ATBF1 expression might be a useful diagnostic marker associated with histological grade and breast cancer malignancy. WNT5A and its signaling pathway are novel mechanisms by which ATBF1 contributes to breast cancer tumorigenesis.

ATBF1 Participates in Dual Functions of TGF-β via Regulation of Gene Expression and Protein Translocalization

TGF-β is a critical cytokine to regulate multiple pathophysiological functions. For tumor development and progression, TGF-β was reported to play dual functions as a tumor suppressor and epithelial-mesenchymal transition (EMT) inducer. The mechanism of the TGF-β signaling pathway is essential for TGF-β/Smad-targeted therapy in clinic. Here, ATBF1 was demonstrated to participate in dual functions of TGF-β via different ways. On one hand, ATBF1 expression level was associated with EMT and migration induced by TGF-β. After TGF-β treatment, ATBF1 expression was reduced in a dose- and time-dependent manner, along with the alteration of cell morphology and EMT marker expression. Knockdown of ATBF1 by siRNA further promoted EMT progression and cell migration. On the other hand, ATBF1 localization was associated with cell proliferation inhibited by TGF-β. The number of cells with nucleus localization of ATBF1 in TGF-β activation group was much higher than that in control group. After that, knockdown of ATBF1 by siRNA rescued the inhibition of cell proliferation affected by TGF-β. These data revealed that ATBF1 is a key gene for the dual roles of TGF-β, which may contribute to future therapy.

Association of ZFHX3 gene variation with atrial fibrillation, cerebral infarction, and lung thromboembolism: An autopsy study

AIM

We aimed to study a single nucleotide polymorphism (SNP), rs2106261, in the transcription factor gene, ZFHX3, in atrial fibrillation (AF) and other related phenotypes by phenome scanning in a Japanese population.

METHOD

We retrieved consecutive autopsy data (n=2433, mean age=80 years) from the Japanese SNP database for geriatric diseases (JG-SNP). Clinical data, including an AF diagnosis, were collected from medical charts. Genotyping was performed with the DNA chip method. We also analyzed 42 pathological and 26 clinical phenotypes, including cerebral infarctions (CIs) and lung thromboembolisms (LTs), diagnosed by macroscopic inspection during the autopsy.

RESULT

Among the 2433 patients with available data, 18.6% had AF, 29.4% had CI, and 4.9% had LT phenotypes. The A allele of the rs2106261 SNP was significantly associated with AF, after adjusting for age, sex, diabetes, hypertension, and smoking (AA+AG/GG, OR=1.51, 95%CI: 1.16-1.97, p=0.002). In the entire cohort, CI was not associated with rs2106261 (p=0.14). However, among patients under 80 years old, rs2106261 was significantly associated with CI (AA+AG/GG, OR=1.57, 95%CI: 1.09-2.26, p=0.01). LT was also associated with rs2106261 (AA+AG/GG, OR=1.99, 95%CI: 1.31-3.01, p=0.001). Associations between rs2106261 and CI and LT remained positive after adjusting for the presence of AF, which indicated that this SNP variant might serve as an independent risk marker.

CONCLUSION

We showed that the ZFHX3 polymorphism, rs2106261 (A allele), was a risk marker for AF and AF-related phenotypes. The roles of this variant in the development of AF and its related phenotypes warrant further investigation.

A diagnostic marker for superficial urothelial bladder carcinoma: lack of nuclear ATBF1 (ZFHX3) by immunohistochemistry suggests malignant progression

Background

Pathological stage and grade have limited ability to predict the outcomes of superficial urothelial bladder carcinoma at initial transurethral resection (TUR). AT-motif binding factor 1 (ATBF1) is a tumor suppressive transcription factor that is normally localized to the nucleus but has been detected in the cytoplasm in several cancers. Here, we examined the diagnostic value of the intracellular localization of ATBF1 as a marker for the identification of high risk urothelial bladder carcinoma.

Methods

Seven anti-ATBF1 antibodies were generated to cover the entire ATBF1 sequence. Four human influenza hemagglutinin-derived amino acid sequence-tagged expression vectors with truncated ATBF1 cDNA were constructed to map the functional domains of nuclear localization signals (NLSs) with the consensus sequence KR[X10-12]K. A total of 117 samples from initial TUR of human bladder carcinomas were analyzed. None of the patients had received chemotherapy or radiotherapy before pathological evaluation.

Results

ATBF1 nuclear localization was regulated synergistically by three NLSs on ATBF1. The cytoplasmic fragments of ATBF1 lacked NLSs. Patients were divided into two groups according to positive nuclear staining of ATBF1, and significant differences in overall survival (P = 0.021) and intravesical recurrence-free survival (P = 0.013) were detected between ATBF1+ (n = 110) and ATBF1− (n = 7) cases. Multivariate analysis revealed that ATBF1 staining was an independent prognostic factor for intravesical recurrence-free survival after adjusting for cellular grading and pathological staging (P = 0.008).

Conclusions

Cleavage of ATBF1 leads to the cytoplasmic localization of ATBF1 fragments and downregulates nuclear ATBF1. Alterations in the subcellular localization of ATBF1 due to fragmentation of the protein are related to the malignant character of urothelial carcinoma. Pathological evaluation using anti-ATBF1 antibodies enabled the identification of highly malignant cases that had been overlooked at initial TUR. Nuclear localization of ATBF1 indicates better prognosis of urothelial carcinoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2845-5) contains supplementary material, which is available to authorized users.

Additive Effect of Zfhx3/Atbf1 and Pten Deletion on Mouse Prostatic Tumorigenesis

The phosphatase and tensin homolog (PTEN) and the zinc finger homeobox 3 (ZFHX3)/AT-motif binding factor 1 (ATBF1) genes have been established as tumor suppressor genes in prostate cancer by their frequent deletions and mutations in human prostate cancer and by the formation of mouse prostatic intraepithelial neoplasia (mPIN) or tumor by their deletions in mouse prostates. However, whether ZFHX3/ATBF1 deletion together with PTEN deletion facilitates prostatic tumorigenesis is unknown. In this study, we simultaneously deleted both genes in mouse prostatic epithelia and performed histological and molecular analyses. While deletion of one Pten allele alone caused low-grade (LG) mPIN as previously reported, concurrent deletion of Zfhx3/Atbf1 promoted the progression to high-grade (HG) mPIN or early carcinoma. Zfhx3/Atbf1 and Pten deletions together increased cell proliferation, disrupted the smooth muscle layer between epithelium and stroma, and increased the number of apoptotic cells. Deletion of both genes also accelerated the activation of Akt and Erk1/2 oncoproteins. These results suggest an additive effect of ZFHX3/ATBF1 and PTEN deletions on the development and progression of prostate neoplasia.

ATBF1 is a novel amyloid-β protein precursor (AβPP) binding protein that affects AβPP expression

The cytoplasmic C-terminal domain of amyloid-β protein precursor (AβPP) binds to several proteins that regulate the trafficking and processing of AβPP and affects amyloid-β (Aβ) production. We previously reported that levels of AT-motif binding factor 1 (ATBF1) are increased in the brains of 17-month-old Tg2576 mice compared with wild-type controls, and that Aβ42 increases ATBF1 expression, inducing death in primary rat cortical neurons. Here, we show that ATBF1 levels are increased in the cytoplasm of hippocampal neurons in Alzheimer's disease (AD) brains compared with non-AD brains. Furthermore, cotransfection of human embryonic kidney (HEK293T) and human neuroblastoma (SH-SY5Y) cells with ATBF1 and AβPP695 increased steady-state levels of AβPP via the binding of ATBF1 to the AβPP cytoplasmic domain (amino acids 666-690), resulting in increased Aβ production and cellular and soluble AβPP (sAβPP) levels without affecting the activity or levels of AβPP processing enzymes (α-, β-, or γ-secretase). Conversely, knockdown of endogenous ATBF1 reduced levels of cellular AβPP, sAβPP, and Aβ in HEK293 cells overexpressing human AβPP695. Our findings provide insight into the dynamics of AβPP processing and Aβ production, and suggest that ATBF1 is a novel AβPP binding protein that may be a suitable therapeutic target for AD.

Down-regulation of ATBF1 activates STAT3 signaling via PIAS3 in pacing-induced HL-1 atrial myocytes

Atrial fibrillation (AF) is progressive and is the most common clinical arrhythmia. It is associated with inflammatory changes characterized by signal transducer and activator of transcription 3 (STAT3) signaling. A zinc finger homeobox 3 (ZFHX3, also named AT-motif binding factor 1, ATBF1) gene variant has been found in patients with AF. However, the mechanism by which the ATBF1 leads to inflammation in AF remains unknown. The aim of this study was to investigate whether tachypacing induces a decrease in ATBF1 expression and then activates STAT3 signaling via protein inhibitor of activated STAT3 (PIAS3). Atrial (HL-1 myocytes) cells were cultured in the presence of rapid electrical stimulations. In tachypaced HL-1 cells, we found that ATBF1 and PIAS3 protein levels were decreased, while the level of phosphorylated STAT3 (p-STAT3) was highly up-regulated compared with that of total STAT3. Knockdown of ATBF1 enhanced this trend, while the overexpression of ATBF1 had the opposite effect. A binary complex of ATBF1 and PIAS3 was formed and then the DNA-binding ability of activated STAT3 was enhanced in tachypaced HL-1 cells. These data indicate that tachypacing decreased ATBF1, leading to enhanced STAT3 DNA-binding activity due to the reduced formation of a binary complex of ATBF1 and PIAS3.

Gene methylation in gastric cancer

Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field.