Penalized weighted smoothed quantile regression for high-dimensional longitudinal data.

Quantile regression, known as a robust alternative to linear regression, has been widely used in statistical modeling and inference. In this paper, we propose a penalized weighted convolution-type smoothed method for variable selection and robust parameter estimation of the quantile regression with high dimensional longitudinal data. The proposed method utilizes a twice-differentiable and smoothed loss function instead of the check function in quantile regression without penalty, and can select the important covariates consistently using the efficient gradient-based iterative algorithms when the dimension of covariates is larger than the sample size. Moreover, the proposed method can circumvent the influence of outliers in the response variable and/or the covariates. To incorporate the correlation within each subject and enhance the accuracy of the parameter estimation, a two-step weighted estimation method is also established. Furthermore, we prove the oracle properties of the proposed method under some regularity conditions. Finally, the performance of the proposed method is demonstrated by simulation studies and two real examples.

Development, dilemma and potential strategies for the application of nanocatalysts in wastewater catalytic ozonation: A review.

With the continuous development of nanomaterials in recent years, the application of nanocatalysts in catalytic ozone oxidation has attracted more and more researchers' attention due to their excellent catalytic properties. In this review, we systematically summarized the current research status of nanocatalysts mainly involving material categories, mechanisms and catalytic efficiency. Based on summary and analysis, we found most of the reported nanocatalysts were in the stage of laboratory research, which was caused by the nanocatalysts defects such as easy aggregation, difficult separation, and easy leakage. These defects might result in severe resource waste, economic loss and potentially adverse effects imposed on the ecosystem and human health. Aiming at solving these defects, we further analyzed the reasons and the existing reports, and revealed that coupling nano-catalyst and membrane, supported nanocatalysts and magnetic nanocatalysts had promising potential in solving these problems and promoting the actual application of nanocatalysts in wastewater treatment. Furthermore, the advantages, shortages and our perspectives of these methods are summarized and discussed.

AR imposes different effects on ZFHX3 transcription depending on androgen status in prostate cancer cells.

Both androgen receptor (AR) and the ZFHX3 transcription factor modulate prostate development. While AR drives prostatic carcinogenesis, ZFHX3 is a tumour suppressor whose loss activates the PI3K/AKT signalling in advanced prostate cancer (PCa). However, it is unknown whether ZFHX3 and AR are functionally related in PCa cells and, if so, how. Here, we report that in AR-positive LNCaP and C4-2B PCa cells, androgen upregulates ZFHX3 transcription via androgen-induced AR binding to the androgen-responsive elements (AREs) of the ZFHX3 promoter. Androgen also upregulated ZFHX3 transcription in vivo, as castration dramatically reduced Zfhx3 mRNA and protein levels in mouse prostates, and ZFHX3 mRNA levels correlated with AR activities in human PCa. Interestingly, the binding of AR to one ARE occurred in the absence of androgen, and the binding repressed ZFHX3 transcription as this repressive binding was interrupted by androgen treatment. The enzalutamide antiandrogen prevented androgen from inducing ZFHX3 transcription and caused excess ZFHX3 protein degradation. In human PCa, ZFHX3 was downregulated and the downregulation correlated with worse patient survival. These findings establish a regulatory relationship between AR and ZFHX3, suggest a role of ZFHX3 in AR function and implicate ZFHX3 loss in the antiandrogen therapies of PCa.

Electrochemical Sensor for Directional Recognition and Measurement of Antibiotic Resistance Genes in Water.

The establishment of rapid targeted identification and analysis of antibiotic resistance genes (ARGs) is very important. In this study, an electrochemical sensor, which can detect ARGs was obtained by modifying the sulfhydryl single-stranded DNA probe onto the thin-film gold electrode through self-assembly. The sensor can perform a hybridization reaction with a target sequence to obtain an electrochemical impedance spectroscopy signal. The results showed that when the concentration of the probe used to modify thin-film gold electrodes during preparation was 1 µM, the hybridization time was 1 h, and the hybridization temperature was 35 °C, the self-assembled sensor showed good detection performance for the ARGs encoding ß-lactam hydrolase. The measurement ARG concentration linear range is 6.3-900.0 ng/mL, and the R2 is 0.9992. The sensor shows good specific recognition ability for single-base, double-base, and three-base mismatch DNA. In addition, after 30 days of storage at 4 °C, the accurate identification and analysis of ARGs can still be maintained.

Formation, application, and storage-reactivation of aerobic granular sludge: A review.

It was an important discovery in wastewater treatment that the microorganisms in the traditional activated sludge can form aerobic granular sludge (AGS) by self-aggregation under appropriate water quality and operation conditions. With a typical three-dimensional spherical structure, AGS has high sludge-water separation efficiency, great treatment capacity, and strong tolerance to toxic and harmful substances, so it has been considered to be one of the most promising wastewater treatment technologies. This paper comprehensively reviewed AGS from multiple perspectives over the past two decades, including the culture conditions, granulation mechanisms, metabolic and structural stability, storage, and its diverse applications. Some important issues, such as the reproducibility of culture conditions and the structural and functional stability during application and storage, were also summarized, and the research prospects were put forward. The aggregation behavior of microorganisms in AGS was explained from the perspectives of physiology and ecology of complex populations. The storage of AGS is considered to have large commercial potential value with the increase of large-scale applications. The purpose of this paper is to provide a reference for the systematic and in-depth study on the sludge aerobic granulation process.

The transcription factor ZFHX3 is crucial for the angiogenic function of hypoxia-inducible factor 1α in liver cancer cells.

Angiogenesis is a hallmark of tumorigenesis, and hepatocellular carcinoma (HCC) is hypervascular and therefore very dependent on angiogenesis for tumor development and progression. Findings from previous studies suggest that in HCC cells, hypoxia-induced factor 1α (HIF1A) and zinc finger homeobox 3 (ZFHX3) transcription factors functionally interact in the regulation of genes in HCC cells. Here, we report that hypoxia increases the transcription of the ZFHX3 gene and enhances the binding of HIF1A to the ZFHX3 promoter in the HCC cell lines HepG2 and Huh-7. Moreover, ZFHX3, in turn, physically associated with and was functionally indispensable for HIF1A to exert its angiogenic activity, as indicated by in vitro migration and tube formation assays of human umbilical vein endothelial cells (HUVECs) and microvessel formation in xenograft tumors of HCC cells. Mechanistically, ZFHX3 was required for HIF1A to transcriptionally activate the vascular endothelial growth factor A (VEGFA) gene by binding to its promoter. Functionally, down-regulation of ZFHX3 in HCC cells slowed their tumor growth, and addition of VEGFA to conditioned medium from ZFHX3-silenced HCC cells partially rescued the inhibitory effect of this medium on HUVEC tube formation. In human HCC, ZFHX3 expression was up-regulated, and this up-regulation correlated with both HIF1A up-regulation and worse patient survival, confirming a functional association between ZFHX3 and HIF1A in human HCC. We conclude that ZFHX3 is an angiogenic transcription factor that is integral to the HIF1A/VEGFA signaling axis in HCC cells.

SUMOylation of the transcription factor ZFHX3 at Lys-2806 requires SAE1, UBC9, and PIAS2 and enhances its stability and function in cell proliferation.

SUMOylation is a posttranslational modification (PTM) at a lysine residue and is crucial for the proper functions of many proteins, particularly of transcription factors, in various biological processes. Zinc finger homeobox 3 (ZFHX3), also known as AT motif-binding factor 1 (ATBF1), is a large transcription factor that is active in multiple pathological processes, including atrial fibrillation and carcinogenesis, and in circadian regulation and development. We have previously demonstrated that ZFHX3 is SUMOylated at three or more lysine residues. Here, we investigated which enzymes regulate ZFHX3 SUMOylation and whether SUMOylation modulates ZFHX3 stability and function. We found that SUMO1, SUMO2, and SUMO3 each are conjugated to ZFHX3. Multiple lysine residues in ZFHX3 were SUMOylated, but Lys-2806 was the major SUMOylation site, and we also found that it is highly conserved among ZFHX3 orthologs from different animal species. Using molecular analyses, we identified the enzymes that mediate ZFHX3 SUMOylation; these included SUMO1-activating enzyme subunit 1 (SAE1), an E1-activating enzyme; SUMO-conjugating enzyme UBC9 (UBC9), an E2-conjugating enzyme; and protein inhibitor of activated STAT2 (PIAS2), an E3 ligase. Multiple analyses established that both SUMO-specific peptidase 1 (SENP1) and SENP2 deSUMOylate ZFHX3. SUMOylation at Lys-2806 enhanced ZFHX3 stability by interfering with its ubiquitination and proteasomal degradation. Functionally, Lys-2806 SUMOylation enabled ZFHX3-mediated cell proliferation and xenograft tumor growth of the MDA-MB-231 breast cancer cell line. These findings reveal the enzymes involved in, and the functional consequences of, ZFHX3 SUMOylation, insights that may help shed light on ZFHX3's roles in various cellular and pathophysiological processes.

Robust approach for variable selection with high dimensional longitudinal data analysis.

This article proposes a new robust smooth-threshold estimating equation to select important variables and automatically estimate parameters for high dimensional longitudinal data. A novel working correlation matrix is proposed to capture correlations within the same subject. The proposed procedure works well when the number of covariates pn increases as the number of subjects n increases. The proposed estimates are competitive with the estimates obtained with the true correlation structure, especially when the data are contaminated. Moreover, the proposed method is robust against outliers in the response variables and/or covariates. Furthermore, the oracle properties for robust smooth-threshold estimating equations under "large n, diverging pn " are established under some regularity conditions. Extensive simulation studies and a yeast cell cycle data are used to evaluate the performance of the proposed method, and results show that the proposed method is competitive with existing robust variable selection procedures.

An efficient Gehan-type estimation for the accelerated failure time model with clustered and censored data.

In medical studies, the collected covariates contain underlying outliers. For clustered/longitudinal data with censored observations, the traditional Gehan-type estimator is robust to outliers in response but sensitive to outliers in the covariate domain, and it also ignores the within-cluster correlations. To take account of within-cluster correlations, varying cluster sizes, and outliers in covariates, we propose weighted Gehan-type estimating functions for parameter estimation in the accelerated failure time model for clustered data. We provide the asymptotic properties of the resulting estimators and carry out simulation studies to evaluate the performance of the proposed method under a variety of realistic settings. The simulation results demonstrate that the proposed method is robust to the outliers existing in the covariate domain and lead to much more efficient estimators when a strong within-cluster correlation exists. Finally, the proposed method is applied to two medical datasets and more reliable and convincing results are hence obtained.

CINP is a novel cofactor of KLF5 required for its role in the promotion of cell proliferation, survival and tumor growth.

Krüppel-like factor 5 (KLF5) both suppresses and promotes tumor growth depending on cellular context. The mechanisms underlying tumor promotion could be targetable for therapy. Although a number of transcriptional targets of KLF5 have been identified and implicated in KLF5-mediated tumor growth, how KLF5 regulates these genes remains to be addressed. Here we performed coimmunoprecipitation (co-IP) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the TSU-Pr1 bladder cancer cell line, in which KLF5 is shown to promote tumor growth, to identify KLF5-interacting nuclear proteins that are necessary for KLF5's tumor promoting function. LC-MS/MS revealed 122 potential KLF5 binding proteins in the nuclear proteins precipitated by the KLF5 antibody, and the top nine candidates included AHNAK, TFAM, HSDL2, HNRNPC, CINP, IST1, FBL, PABPC1 and SNRNP40. SRB assays of these nine proteins indicated that silencing CINP had the most potent inhibitory effect on cell growth in KLF5-expressing cells but did not affect parental TSU-Pr1 cells. Further analyses not only confirmed the physical interaction between KLF5 and CINP, also demonstrated that knockdown of CINP attenuated the effects of KLF5 on cell cycle progression, apoptosis and tumorigenesis. Silencing CINP also attenuated the effect of KLF5 on the expression of a number of genes and signaling pathways, including cell cycle regulator Cyclin D1 and apoptosis-related Caspase 7. These results suggest that CINP is a cofactor of KLF5 that is crucial for the promotion of tumor growth, and that the KLF5-CINP interaction could be a novel therapeutic target for inhibiting KLF5-promoted tumor growth.

Zinc Finger Homeodomain Factor Zfhx3 Is Essential for Mammary Lactogenic Differentiation by Maintaining Prolactin Signaling Activity.

The zinc finger homeobox 3 (ZFHX3, also named ATBF1 for AT motif binding factor 1) is a transcription factor that suppresses prostatic carcinogenesis and induces neuronal differentiation. It also interacts with estrogen receptor α to inhibit cell proliferation and regulate pubertal mammary gland development in mice. In the present study, we examined whether and how Zfhx3 regulates lactogenic differentiation in mouse mammary glands. At different stages of mammary gland development, Zfhx3 protein was expressed at varying levels, with the highest level at lactation. In the HC11 mouse mammary epithelial cell line, an in vitro model of lactogenesis, knockdown of Zfhx3 attenuated prolactin-induced ß-casein expression and morphological changes, indicators of lactogenic differentiation. In mouse mammary tissue, knock-out of Zfhx3 interrupted lactogenesis, resulting in underdeveloped glands with much smaller and fewer alveoli, reduced ß-casein expression, accumulation of large cytoplasmic lipid droplets in luminal cells after parturition, and failure in lactation. Mechanistically, Zfhx3 maintained the expression of Prlr (prolactin receptor) and Prlr-Jak2-Stat5 signaling activity, whereas knockdown and knock-out of Zfhx3 in HC11 cells and mammary tissues, respectively, decreased Prlr expression, Stat5 phosphorylation, and the expression of Prlr-Jak2-Stat5 target genes. These findings indicate that Zfhx3 plays an essential role in proper lactogenic development in mammary glands, at least in part by maintaining Prlr expression and Prlr-Jak2-Stat5 signaling activity.

PVT1-derived miR-1207-5p promotes breast cancer cell growth by targeting STAT6.

Accumulating evidence indicates that ectopic expression of non-coding RNAs are responsible for breast cancer progression. Increased non-coding RNA PVT1, the host gene of microRNA-1207-5p (miR-1207-5p), has been associated with breast cancer proliferation. However, how PVT1 functions in breast cancer is still not clear. In this study, we show a PVT1-derived microRNA, miR-1207-5p, that promotes the proliferation of breast cancer cells by directly regulating STAT6. We first confirm the positive correlated expression pattern between PVT1 and miR-1207-5p by observing consistent induced expression by estrogen, and overexpression in breast cancer cell lines and breast cancer patient specimens. Moreover, silence of PVT1 also decreased miR-1207-5p expression. Furthermore, increased miR-1207-5p expression promoted, while decreased miR-1207-5p expression suppressed, cell proliferation, colony formation, and cell cycle progression in breast cancer cell lines. Mechanistically, a novel target of miR-1207-5p, STAT6, was identified by a luciferase reporter assay. Overexpression of miR-1207-5p decreased the levels of STAT6, which activated CDKN1A and CDKN1B to regulate the cell cycle. We also confirmed the reverse correlation of miR-1207-5p and STAT6 expression levels in breast cancer samples. Therefore, our findings reveal that PVT1-derived miR-1207-5p promotes the proliferation of breast cancer cells by targeting STAT6, which in turn controls CDKN1A and CDKN1B expression. These findings suggest miR-1207-5p might be a potential target for breast cancer therapy.

Selection of working correlation structure in generalized estimating equations.

The well-known generalized estimating equations is a very popular approach for analyzing longitudinal data. Selecting an appropriate correlation structure in the generalized estimating equations framework is a key step for estimating parameters efficiently and deriving reliable statistical inferences. We present two new criteria for selecting the best among the candidates with any arbitrary structures, even for irregularly timed measurements. The simulation results demonstrate that the new criteria perform more similarly to EAIC and EBIC as the sample size becomes large. However, their performance is much enhanced when the sample size is small and the number of measurements is large. Finally, three real datasets are used to illustrate the proposed criteria. Copyright © 2017 John Wiley & Sons, Ltd.

Interruption of KLF5 acetylation converts its function from tumor suppressor to tumor promoter in prostate cancer cells.

KLF5 possesses both tumor suppressing and tumor promoting activities, though the mechanism controlling these opposing functions is unknown. In cultured noncancerous epithelial cells, KLF5 converts from proproliferative to antiproliferative activity upon TGFß-induced acetylation, which sequentially alters the KLF5 transcriptional complex and the expression of genes such as p15 and MYC. In this study, we tested whether the acetylation status of KLF5 also determines its opposing functions in tumorigenesis using the PC-3 and DU 145 prostate cancer cell lines, whose proliferation is inhibited by TGFß. KLF5 inhibited the proliferation of these cancer cells, and the inhibition was dependent on KLF5 acetylation. MYC and p15 showed the same patterns of expression change found in noncancerous cells. In nude mice, KLF5 also suppressed tumor growth in an acetylation-dependent manner. Furthermore, deacetylation switched KLF5 to tumor promoting activity, and blocking TGFß signaling attenuated the tumor suppressor activity of KLF5. RNA sequencing and comprehensive data analysis suggest that multiple molecules, including RELA, p53, CREB1, MYC, JUN, ER, AR and SP1, mediate the opposing functions of AcKLF5 and unAcKLF5. These results provide novel insights into the mechanism by which KLF5 switches from antitumorigenic to protumorigenic function and also suggest the roles of AcKLF5 and unAcKLF5, respectively, in the tumor suppressing and tumor promoting functions of TGFß.

Genetic analysis and preliminary function study of miR-423 in breast cancer.

Common genetic variants (single nucleotide polymorphisms SNPs) in microRNA (miRNA) genes may alter their maturation or expression and play a role in the formation of human cancer. Recently, the association between the SNP rs6505162 in pre-miR-423 and cancer risk has been frequently evaluated in diverse populations and in a range of cancers. In this study, we determined the genotypes of SNP rs6505162 in 5 matched cell lines (breast cancer cell lines and their corresponding peripheral blood cell lines) and 114 matched clinical specimens (clinical breast carcinoma specimens and their corresponding normal tissues), compared the processing efficiency of pri-miRNA to mature forms between pre-miR-423-12C (wild-type) and pre-miR-423-12A (mutant-type) expression vectors, and evaluated the function of miR-423 on cell proliferation. Our data showed that two out of five breast cancer cell lines and 8.77 % (10/114) of tumors underwent somatic mutations of the rs6505162 SNP, and somatic mutation state was significantly correlated with the expression of clinicopathologic variables, proliferating cell nuclear antigen (PCNA) and mutant p53. The pre-miR-423-12C SNP blocked the endogenous processing of pri-miR-423 to its two mature miRNAs. Interestingly, selected pre-miR-423-12C stable cell population had lower proliferation ability than pre-miR-423-12A stable cell population. Moreover, miR-423 promoted cell proliferation in breast cancer cell lines through its miR-423-3p strand, not miR-423-5p. Taken together, these results suggest that the SNP rs6505162 in pre-miR-423 affects the mature miR expression, and miR-423 plays a potentially oncogenic role in breast tumorigenesis.

Molecular-level insights into dissolved organic matter and its variations of the full-scale processes in a typical petrochemical wastewater treatment plant.

Petrochemical wastewater (PCWW) treatment poses challenges due to its unique and complex dissolved organic matter (DOM) composition, originating from various industrial processes. Despite the addition of advanced treatment units in PCWW treatment plants to meet discharge standards, the mechanisms of molecular-level sights into DOM reactivity of the upgraded full-scale processes including multiple biological treatments and advanced treatment remain unclear. Herein, we employ water quality indexes, spectra, molecular weight (MW) distribution, and Fourier transform ion cyclotron resonance mass spectrometry to systematically characterize DOM in a typical PCWW treatment plant including influent, micro-oxygen hydrolysis acidification (MOHA), anaerobic/oxic (AO), and micro-flocculation sand filtration-catalytic ozonation (MFSF-CO). Influent DOM is dominated by tryptophan-like and soluble microbial products with MW fractions 〈 1 kDa and 〉 100 kDa, and CHO with lignin and aliphatic/protein structures. MOHA effectively degrades macromolecular CHO (10.86 %) and CHON (5.24 %) compounds via deamination and nitrogen reduction, while AO removes CHOS compounds with MW < 10 kDa by desulfurization, revealing distinct DOM conversion mechanisms. MFSF-CO transforms unsaturated components to less aromatic and more saturated DOM through oxygen addition reactions and shows high CHOS and CHONS reactivity via desulfurization and deamination reactions, respectively. Moreover, the correlation among multiple parameters suggests UV254 combined with AImod as a simple monitoring indicator of DOM to access the chemical composition. The study provides molecular-level insights into DOM for the contribution to the improvement and optimization of the upgraded processes in PCWW.

Aluminum-based ozone catalysts prepared by mixing method: Characteristics, performance and carbon emissions.

Green and low carbon is an essential direction for the development of water treatment technology. Ozone catalysts prepared by the mixing method have advantages in terms of energy consumption and CO2 emissions, but are considered to be insufficient in catalytic efficiency and stability. In this paper, an Mn-Cu-Ce/Al2O3 (MCCA) catalyst was prepared by optimizing the preparation conditions of the mixing method and the types and ratios of active components. Taking petrochemical secondary effluent (PCSE) as the treatment object, the performance of the catalyst and the carbon emission in the preparation process were studied; and compared with the impregnation method. Results showed that compared with catalysts loaded with other components, the MCCA had a higher removal efficiency for TOC (43.04%) and COD (53.18%), which was basically equivalent to the impregnation method, and the treated effluent reached the expected concentration. MCCA promoted the decomposition rate of O3 by ten times, and the main active species generated were found to be •OH and 1O. Similar to the catalytic ozonation by the catalyst prepared by the impregnation method, the adsorption sites and surface hydroxyl groups on the MCCA surface play a significant role in the degradation of pollutants. However, the carbon emission in the catalyst preparation process of the mixing method was 418.68 kg/ton, which was only 44% of the impregnation method (949.67 kg/ton). Under the global low-carbon transition, this study shows that the mixing method aligns more with the concept of green, clean, and efficient ozone catalyst preparation.

First record of well-preserved canid coprolites from Eurasia: New insights into the unique ecological niche of Yuanmou Basin.

This study reconstructs the Early Pleistocene paleoenvironment of the Yuanmou Basin through coproecology of the third member of the Yuanmou Formation. We examined 38 exceptionally well-preserved coprolites from a new fossil locality, and attributed the putative defecating agent to the hypercarnivorous diet canid, Sinocuon yuanmouensis through geochemical and quantitative analyses. A new ichnogenus and ichnospecies, Cuocopros yuanmouensis igen. et. isp. nov., was established based on distinctive characteristics. Multi-disciplinary analysis, including sediment palynology and lithostratigraphy, helped primarily reconstruct a significant climatic event during the early Pleistocene, coinciding with the emergence of Yuanmou Man during the fourth member of the Yuanmou Formation's deposition. The findings provide insights into coexistence between canids, hyaenas, hominoids, and other fauna, revealing a rich paleoecosystem and food chain in the region's history. This study contributes to understanding the complex ecological dynamics during this period in the Yuanmou Basin.

Upregulation of ATBF1 by progesterone-PR signaling and its functional implication in mammary epithelial cells.

Progesterone (Pg) is an essential steroid hormone during mammary gland development and tumorigenesis, including the maintenance of epithelial stem/progenitor cells. Pg functions through interaction with the progesterone receptors (PR) and Pg-PR signaling is thought to be mediated by key transcription factors, which are largely unidentified. In this study, we have identified the ATBF1 transcription factor as a transcriptional target of Pg-PR signaling in mammary epithelial cells. Pg treatment dramatically increased ATBF1 expression at both mRNA and protein levels in cultured cells and mammary tissues. As expected, the induction of ATBF1 was PR-dependent, as it only occurred in PR-positive but not in PR-negative cells, and pretreatment with the Pg antagonist RU-486 or RNAi-mediated knockdown of PR abolished the upregulation of ATBF1 by Pg. Promoter-reporter and ChIP assays further showed that Pg-activated PR directly binds to the ATBF1 promoter to induce its transcription. Prevention of ATBF1 induction inhibited the function of Pg in promoting progenitor cell transition, as indicated by colony formation in a Matrigel culture assay and expression of stem cell markers CD49f and CD44. These findings suggest that ATBF1 plays a crucial role in the Pg-PR signaling pathway in mammary epithelial cells.

Role of ERRF, a novel ER-related nuclear factor, in the growth control of ER-positive human breast cancer cells.

Whereas estrogen-estrogen receptor α (ER) signaling plays an important role in breast cancer growth, it is also necessary for the differentiation of normal breast epithelial cells. How this functional conversion occurs, however, remains unknown. Based on a genome-wide sequencing study that identified mutations in several breast cancer genes, we examined some of the genes for mutations, expression levels, and functional effects on cell proliferation and tumorigenesis. We present the data for C1orf64 or ER-related factor (ERRF) from 31 cell lines and 367 primary breast cancer tumors. Whereas mutation of ERRF was infrequent (1 of 79 or 1.3%), its expression was up-regulated in breast cancer, and the up-regulation was more common in lower-stage tumors. In addition, increased ERRF expression was significantly associated with ER and/or progesterone receptor (PR) positivity, which was still valid in human epidermal growth factor receptor 2 (HER2)-negative tumors. In ER-positive tumors, ERRF expression was inversely correlated with HER2 status. Furthermore, higher ERRF protein expression was significantly associated with better disease-free survival and overall survival, particularly in ER- and/or PR-positive and HER2-negative tumors (luminal A subtype). Functionally, knockdown of ERRF in two ER-positive breast cancer cell lines, T-47D and MDA-MB-361, suppressed cell growth in vitro and tumorigenesis in xenograft models. These results suggest that ERRF plays a role in estrogen-ER-mediated growth of breast cancer cells and could, thus, be a potential therapeutic target.