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Forkhead box proteins (FOXs) play important roles in multiple biological processes; while little is known regarding the role of FOX members in pancreatic adenocarcinoma (PAAD). This study aimed to comprehensively investigate the function of FOX family members in PAAD.Expression and prognostic value of FOXs were analyzed by R language and GEPIA. Genetic alteration and promoter methylation level were analyzed using CBioPortal and UALCAN. Protein-protein interactions and gene functions were analyzed using STRING and DAVID. TIMER and SENESCopedia were utilized to analyze the correlation of FOXs with immune cell infiltration or tumor senescence. Protein levels of FOXs were detected by immunohistochemistry.Expression of 15 of 50 FOXs were significantly elevated in PAAD. Among these 15 differentially expressed FOXs (DE-FOXs), 4 were significantly associated with the clinical cancer stage and 4 were negatively associated with overall survival. Functions of DE-FOXs were related to epithelial tube morphogenesis, nuclear chromatin, and DNA-binding. Promoter methylation and genomic alterations were not major causes of FOX dysregulation. Most DE-FOX was correlated with diverse immune infiltration cells. Seven of the DE-FOXs were positively related to tumor senescence. The protein levels of FOXM1, FOXP1, and FOXN3 were negatively correlated with OS in the collected PAAD patients.FOXM1, FOXP1, and FOXN3 have prognostic value. Seven FOXs were related senescence, whereas most DE-FOXs were related to immune infiltration in PAAD. Our findings are instructive for future research on FOX family and provide novel insights into the selection of FOXs with potential prognostic or therapeutic target value.

More and more college students are going out of school to invest in the talent market. However, the current situation of College Students' entrepreneurship practice is worrying. A systematic support scheme is urgently needed to give necessary support and guidance to college students' entrepreneurial subjects. Based on the analysis of the current situation and existing problems of College Students' entrepreneurship, this paper attempts to build an entrepreneurial support system with contemporary college students as the core, based on the coordination of the society, universities and government, with the ultimate purpose of promoting the healthy and sustainable development of College Students' entrepreneurial activities, so as to promote the healthy and sustainable development of entrepreneurial activities.

Background A simple, rapid and sensitive method coupling ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of malachite green (MG) and crystal violet (CV) in different water samples. Objective In ultrasound-assisted DLLME procedure, several parameters affecting the extraction efficiency, including pH, type and volume of the extraction and dispersive solvents, extraction time, ionic strength, were optimized to improve the accuracy and precision of this method. Methods MG and CV were extracted and preconcentrated using dichloromethane and acetonitrile as the extraction and dispersive solvents, respectively. Results Under the optimum conditions, the proposed method affords good linearity in the range of 0.40–20.0 ng/L, and the limit of detections were 0.21 and 0.32 ng/L for MG and CV, respectively. The recoveries of the method at three spiked levels were in the range of 83.4–94.2% with relative standard deviations lower than 4.7% (n = 3). Conclusions Satisfactorily, no significant matrix effect has been found as the data ranged between 68% and 102%.

Vibrio parahaemolyticus is an important pathogenic bacterium in both food safety management and mariculture. Rapid and accurate detection technologies are critical for effective control of its outbreak and spreading. Conventional technologies and polymerase chain reaction (PCR)-based approaches have limited usage because of the requirement of laboratory instruments and trained personnel. Using the isothermal recombinase polymerase amplification (RPA) technology, several detection assays have been developed with added convenience. Combining the lateral flow strip (LFS) test with RPA can further simplify the detection. In this study, an improved RPA assay using LFS for visual detection of V. parahaemolyticus was developed. Primers were designed targeting the virulence genes and screened for amplification efficiency, nonspecific amplification, and primer-dimer formation. Probes were designed for the best primer pairs, and the weakness of LFS tests, being easily affected by primer-dependent artifacts, was overcome by sequence modifications on primers and probe. The RPA-LFS assay took 25 min at 35 to 45 °C, and showed excellent specificity. It detected as low as one colony forming unit (CFU) of V. parahaemolyticus per reaction without DNA purification, or 10 CFU/10 g spiked food samples with 2 hr of enrichment. The detection limit was better than the currently available RPA-based detection methods. Application of the RPA-LFS assay for simulated samples or real clinical samples showed accurate and consistent detection results compared to bioassay and quantitative PCR. The RPA-LFS assay provided a rapid, accurate, and convenient V. parahaemolyticus detection method suitable for on-site detection in resource-limited conditions. PRACTICAL APPLICATION: This research developed a rapid and visual detection technology for Vibrio parahaemolyticus that is not dependent on complicated equipment. The detection process takes 25 min and the result is read with the naked eye. A detection kit can be developed based on this technology for on-site detection of V. parahaemolyticus in resource-limited regions for food safety management and mariculture.

Background Vibrio alginolyticus is an important pathogen that has to be closely monitored and controlled in the mariculture industry because of its strong pathogenicity, quick onset after infection and high mortality rate in aquatic animals. Fast, simple and specific methods are needed for on-site detection to effectively control outbreaks and prevent economic losses. The detection specificity towards the pathogenic strains has to be emphasized to facilitate pointed treatment and prevention. Polymerase chain reaction (PCR)-based molecular approaches have been developed, but their application is limited due to the requirement of complicated thermal cycling machines and trained personnel. Results A fast, simple and highly specific detection method for V. alginolyticus pathogenic strains was established based on isothermal recombinase polymerase amplification (RPA) and lateral flow dipsticks (LFD). The method targeted the virulence gene toxR, which is reported to have good coverage for V. alginolyticus pathogenic strains. To ensure the specificity of the method, the primer-probe set of the RPA system was carefully designed to recognize regions in the toxR gene that diverge in different Vibrio species but are conserved in V. alginolyticus pathogenic strains. The primer-probe set was determined after a systematic screening of amplification performance, primer-dimer formation and false positive signals. The RPA-LFD method was confirmed to have high specificity for V. alginolyticus pathogenic strains without any cross reaction with other Vibrio species or other pathogenic bacteria and was able to detect as little as 1 colony forming unit (CFU) per reaction without DNA purification, or 170 fg of genomic DNA, or 6.25 × 103 CFU/25 g in spiked shrimp without any enrichment. The method finishes detection within 30 min at temperatures between 35 °C and 45 °C, and the visual signal on the dipstick can be directly read by the naked eye. In an application simulation, randomly spiked shrimp homogenate samples were 100% accurately detected. Conclusions The RPA-LFD method developed in this study is fast, simple, highly specific and does not require complicated equipment. This method is applicable for on-site detection of V. alginolyticus pathogenic strains for the mariculture industry.

Introduction: During breast cancer chemotherapy, the chemoresistance that frequently accompanies the treatment has become a big challenge. Long noncoding RNAs (LncRNAs) have been related to the development of chemoresistance in multiple cancer types. LncRNA DDX11-AS1 has shown a carcinogenic role in lung and colorectal cancer and was reported to enhance oxaliplatin resistance in gastric cancer and Taxol insensitivity in esophageal cancer. But its role in breast cancer chemotherapy drug resistance remains unknown. This study aimed to investigate the function and mechanism of lncRNA DDX11-AS1 in breast cancer chemoresistance. Methods: The relationship between DDX11-AS1 and adriamycin (ADR) resistance was confirmed by qPCR, cell viability tests, and survival analysis. Then, RNA immunoprecipitation was conducted to evaluate the interaction between DDX11-AS1 and RNA-binding protein LIN28A. The regulation effect of LIN28A on autophagy-related genes ATG7 or ATG12 was detected by RNA stability assay and Western blot. Their correlation analysis was evaluated in GEO datasets and further validated by immunohistochemical results. The clinical significance of DDX11-AS1, ATG7, or ATG12 was evaluated by Kaplan-Meier Plotter analysis. Results: Here, we reported DDX11-AS1 was significantly upregulated in chemoresistant breast cancer cells and overexpression of DDX11-AS1 promoted ADR resistance in breast cancer. LIN28A could interact with DDX11-AS1 and was involved in DDX11-AS1-mediated ADR resistance. Interfering with LIN28A reversed DDX11-AS1-induced ADR resistance. LIN28A could increase the protein level of ATG7 and ATG12 by increasing their mRNA stability. Survival analysis showed that ATG12 expression level was negatively correlated with the prognosis of breast cancer patients. Conclusion: This study clarifies the role of DDX11-AS1 in breast cancer chemoresistance and revealed a new mechanism, that is, interacting with LIN28A to stabilize ATG7 and ATG12 and jointly promote chemorefractory. These findings warrant further in vivo investigations to study DDX11-AS1 as a potential target to overcome chemoresistance.

Listeria monocytogenes is an important foodborne pathogenic bacterium that is explicitly threatening public health and food safety. Rapid, simple, and sensitive detection methods for this pathogen are of urgent need for the increasing on-site testing demands. Application of the isothermal recombinase polymerase amplification (RPA) and the lateral flow strip (LFS) in the detection is promising for fast speed, high sensitivity, and little dependency on equipment and trained personnel. However, the simplicity comes with an intrinsic and non-negligible risk, the false-positive signals from primer–dimers. In this study, an improved RPA–LFS system was established for detection of L. monocytogenes that eliminated false-positive signals from primer–dimers. Primer candidates were carefully selected from the entire L. monocytogenes genome sequence and rigorously screened for specific amplifications in PCR and RPA reactions. For the optimal primer pairs, probes that matched the targeted fragment sequences, although had the smallest chance to form cross-dimers with the primers, were designed and screened. The intelligent use of the probe successfully linked the positive signal to the actual amplification product. This RPA–LFS system was highly specific to L. monocytogenes and was able to detect as low as 1 colony-forming unit of the bacterium per reaction (50 μl) without DNA purification, or 100 fg of the genomic DNA/50 μl. The amplification could be conducted under the temperature between 37 and 42°C, and the whole detection finished within 25 min. Test of artificially contaminated milk gave 100% accuracy of detection without purification of the samples. Various food samples spiked with 10 colony-forming unit of L. monocytogenes per 25 g or 25 ml were successfully detected after an enrichment time period of 6 h. The RPA–LFS system established in this study is a rapid, simple, and specific detection method for L. monocytogenes that has eliminated false-positive results from primer–dimers. In addition, this study has set a good example of eliminating the false-positive risk from primer–dimers in isothermal amplification-based detection methods, which is applicable to the development of detection technologies for other pathogens.

Additional file 1: Fig. S1 Sequence alignment of the toxR genes of Vibrio species. The name of the corresponding species is indicated on the left of each sequence. GenBank numbers of the toxR genes of the species are EU155543.1, DQ640258.1, AB175481.1, EU727207.1, EU727208.1, AB029907.1, MF100077.1, and AB042547.1 (from top to bottom). Diverged regions are indicated by the black boxes. Fig. S2 Sequence alignment of the toxR genes of V. alginolyticus pathogenic strains. Information of the corresponding strain is indicated on the left of each sequence. GenBank numbers of the toxR genes of the strains are EU155543.1, CP014036.1, AB372531.1, AB372526.1, CP014036.1, and JN188451.1 (from top to bottom). The conserved region is indicated by the black box. Fig. S3. Sequences targeted by primer-probe set F2/Probe 2/R in the toxR genes of Vibrio species and other bacteria. The name of the corresponding species is indicated on the left of each sequence. GenBank numbers of the toxR genes of the species are EU155543.1, HQ452616.1, LT797832.1, NC_002516.2, NC_012214.1, AY751345.1, JX401922.1, HQ318823.1, KU760757.1, KX280762.1, AF414370.1, MF100077.1, NC_006370.1, AM183574.1, and AB042547.1 (from top to bottom). The targeted regions by the forward primer (F), the probe (P) and the reverse primer (R) are indicated by the black boxes. Sequences targeted by primer-probe set F2/Probe 2/R in the toxR genes of Vibrio species and other bacteria. GenBank numbers of the toxR genes of the species are EU155543.1, KT265743.1, HQ452618.1, EU727207.1, AY751346.1, GQ455024.1, AY751359.1, AY751341.1, AY751340.1, AY751337.1, L29053.1, AY247418.1, AF170885.1, UHIH01000001.1, and AF170884.1 (from top to bottom). Sequences targeted by primer-probe set F2/Probe 2/R in the toxR genes of Vibrio species and other bacteria. GenBank numbers of the toxR genes of the species are EU155543.1, EU155587.1, NC_016613.1, FM999823.1, AY751344.1, AY751342.1, AY751343.1, AF170881.1, EU727208.1, KF322110.1, and HQ452617.1 (from top to bottom). Fig. S4. Agarose gel image of the PCR detection of V. alginolyticus in shrimp samples. Sample numbers are indicated on the wells of the gel. The DNA ladder was run in the last lane of each row. The band sizes of the DNA ladder are shown on the right of each row. Table S1. Strain information of bacteria used in this study and RPA-LFD detection results.

Background Recently, increasing evidence shows that long noncoding RNAs (lncRNAs) play a significant role in human tumorigenesis. However, the function of lncRNAs in human gastric cancer remains largely unknown. Results By using publicly available expression profiling data from gastric cancer and integrating bioinformatics analyses, we screen and identify a novel lncRNA, HOXC-AS3. HOXC-AS3 is significantly increased in gastric cancer tissues and is correlated with clinical outcomes of gastric cancer. In addition, HOXC-AS3 regulates cell proliferation and migration both in vitro and in vivo. RNA-seq analysis reveals that HOXC-AS3 knockdown preferentially affects genes that are linked to proliferation and migration. Mechanistically, we find that HOXC-AS3 is obviously activated by gain of H3K4me3 and H3K27ac, both in cells and in tissues. RNA pull-down mass spectrometry analysis identifies that YBX1 interacts with HOXC-AS3, and RNA-seq analysis finds a marked overlap in genes differentially expressed after YBX1 knockdown and those transcriptionally regulated by HOXC-AS3, suggesting that YBX1 participates in HOXC-AS3-mediated gene transcriptional regulation in the tumorigenesis of gastric cancer. Conclusions Together, our data demonstrate that abnormal histone modification-activated HOXC-AS3 may play important roles in gastric cancer oncogenesis and may serve as a target for gastric cancer diagnosis and therapy. Electronic supplementary material The online version of this article (10.1186/s13059-018-1523-0) contains supplementary material, which is available to authorized users.

Listeria monocytogenes is an important foodborne pathogenic bacterium that is explicitly threatening public health and food safety. Rapid, simple, and sensitive detection methods for this pathogen are of urgent need for the increasing on-site testing demands. Application of the isothermal recombinase polymerase amplification (RPA) and the lateral flow strip (LFS) in the detection is promising for fast speed, high sensitivity, and little dependency on equipment and trained personnel. However, the simplicity comes with an intrinsic and non-negligible risk, the false-positive signals from primer–dimers. In this study, an improved RPA–LFS system was established for detection of L. monocytogenes that eliminated false-positive signals from primer–dimers. Primer candidates were carefully selected from the entire L. monocytogenes genome sequence and rigorously screened for specific amplifications in PCR and RPA reactions. For the optimal primer pairs, probes that matched the targeted fragment sequences, although had the smallest chance to form cross-dimers with the primers, were designed and screened. The intelligent use of the probe successfully linked the positive signal to the actual amplification product. This RPA–LFS system was highly specific to L. monocytogenes and was able to detect as low as 1 colony-forming unit of the bacterium per reaction (50 μl) without DNA purification, or 100 fg of the genomic DNA/50 μl. The amplification could be conducted under the temperature between 37 and 42°C, and the whole detection finished within 25 min. Test of artificially contaminated milk gave 100% accuracy of detection without purification of the samples. Various food samples spiked with 10 colony-forming unit of L. monocytogenes per 25 g or 25 ml were successfully detected after an enrichment time period of 6 h. The RPA–LFS system established in this study is a rapid, simple, and specific detection method for L. monocytogenes that has eliminated false-positive results from primer–dimers. In addition, this study has set a good example of eliminating the false-positive risk from primer–dimers in isothermal amplification-based detection methods, which is applicable to the development of detection technologies for other pathogens.

Abnormal expression of long interspersed element-1 (LINE-1) has been implicated in drug resistance, while our previous study showed that chemotherapy drug paclitaxel (PTX) increased LINE-1 level with unknown mechanism. Bioinformatics analysis suggested the regulation of LINE-1 mRNA by drug-induced stress granules (SGs). This study aimed to explore whether and how SGs are involved in drug-induced LINE-1 increase and thereby promotes drug resistance of triple negative breast cancer (TNBC) cells. We demonstrated that SGs increased LINE-1 expression by recruiting and stabilizing LINE-1 mRNA under drug stress, thereby adapting TNBC cells to chemotherapy drugs. Moreover, LINE-1 inhibitor efavirenz (EFV) could inhibit drug-induced SG to destabilize LINE-1. Our study provides the first evidence of the regulation of LINE-1 by SGs that could be an important survival mechanism for cancer cells exposed to chemotherapy drugs. The findings provide a useful clue for developing new chemotherapeutic strategies against TNBCs.

// Xinxin Si 1, 4 , Ruochen Zang 1, 4 , Erbao Zhang 5 , Yue Liu 1, 4 , Xiao Shi 1, 4 , Ershao Zhang 1, 4 , Lipei Shao 1, 4 , Andi Li 1, 4 , Nan Yang 1, 5 , Xiao Han 1, 5 , Beijing Pan 6 , Zhihong Zhang 6 , Luan Sun 1, 4 , Yujie Sun 1, 2, 3, 4 1 Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, Jiangsu, China 2 Collaborative Innovation Center for Cancer Medicine, Jiangsu Key Lab of Cancer Biomarkers, Prevention and Treatment, Nanjing Medical University, Nanjing, Jiangsu, China 3 State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, Jiangsu, China 4 Department of Cell Biology, Nanjing Medical University, Nanjing, Jiangsu, China 5 Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu, China 6 Department of Pathology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China Correspondence to: Yujie Sun, email: yujiesun@njmu.edu.cn Luan Sun, email: carolsun133@hotmail.com Keywords: breast cancer, chemoresistance, lncRNA H19, apoptosis, estrogen receptor Received: May 01, 2016 Accepted: October 21, 2016 Published: November 10, 2016 ABSTRACT Breast cancer is a common malignancy in women. Acquisition of drug resistance is one of the main obstacles encountered in breast cancer therapy. Long non-coding RNA (lncRNA) has been demonstrated to play vital roles in both development and tumorigenesis. However, the relationship between lncRNAs and the development of chemoresistance is not well established. In the present study, the high expression of lncRNA H19 was identified as a powerful factor associated with paclitaxel (PTX) resistance in ERα-positive breast cancer cells, but not in ERα-negative breast cancer cells. LncRNA H19 attenuated cell apoptosis in response to PTX treatment by inhibiting transcription of pro-apoptotic genes BIK and NOXA. H19 was further confirmed to suppress the promoter activity of BIK by recruiting EZH2 and by trimethylating the histone H3 at lysine 27. Interestingly, our data showed that lncRNA H19 was one of the downstream target molecules of ERα. Altered ERα expression may therefore change H19 levels to modulate the apoptosis response to chemotherapy in breast cancer cells. Our data suggest that the ERα-H19-BIK signaling axis plays an important role in promoting chemoresistance.

// Erbao Zhang 1,* , Dandan Yin 2,* , Liang Han 3,* , Xuezhi He 1 , Xinxin Si 1 , Wenming Chen 4 , Rui Xia 1 , Tongpeng Xu 4 , Dongying Gu 5 , Wei De 1 , Renhua Guo 4 , Zhi Xu 5 and Jinfei Chen 5,6 1 Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, Jiangsu, PR China 2 Central Laboratory, the Second Affiliated Hospital of Southeast University, Nanjing, Jiangsu, PR China 3 Department of Oncology, Xuzhou Central Hospital, Affiliated Xuzhou Hospital, College of Medicine, Southeast University, Xuzhou, Jiangsu, PR China 4 Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, PR China 5 Department of Oncology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, PR China 6 Collaborative Innovation Center for Cancer Personalized Medicine, Nanjing Medical University, Nanjing, Jiangsu, PR China 7 Departments of Pathology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, PR China * These authors have contributed equally to this work and should be regarded as joint first authors Correspondence to: Jinfei Chen, email: // Zhi Xu, email: // Renhua Guo, email: // Wei De, email: // Keywords : E2F1, LINC00668, cell cycle, proliferation, gastric cancer Received : March 10, 2015 Accepted : December 12, 2015 Published : December 23, 2015 Abstract Recently, long noncoding RNAs (lncRNAs) have been shown to have important regulatory roles in human cancer biology. By utilizing publicly available lncRNAs expression profiling data and integrating analyses, we screened out LINC00668, whose expression is significantly increased and correlated with outcomes in gastric cancer (GC). Further experiments revealed that LINC00668 knockdown significantly repressed proliferation, both in vitro and in vivo . Mechanistic investigations showed that LINC00668 was a direct transcriptional target of E2F transcription factor 1 (E2F1). We further demonstrated that LINC00668 was associated with PRC2 and that this association was required for epigenetic repression of cyclin-dependent protein kinase inhibitors (CKIs), including p15, p16, p21, p27 and p57, thus contributing to the regulation of the gastric cancer cell cycle. Our results suggest that E2F1-activated LINC00668, as a cell cycle regulator, enriches the mechanistic link between lncRNA and the E2F1-mediated cell cycle regulation pathway and may serve as a candidate prognostic biomarker and target for new therapies in human gastric cancer.

Supplementary Methods. (DOC 44 kb)

Figure S1. (A) HOXC-AS3 expression after ASO-mediated knockdown and plasmid-mediated overexpression in GC cells. (B) Expression of HOXC-AS3 across diverse normal human tissues from GTEx. Figure S2. (A) Western blots were performed to detect YBX1 expression. (B) The altered mRNA levels of genes were confirmed by qRT-PCR for knockdown HOXC-AS3 in BGC-823 and SGC-7901 cells. (C) Based on qRT-PCR assays, the level of YBX1 was upregulated in 60 pairs GC tissues. MTT assays and transwell assays were used to investigate the changes in proliferation and migratory abilities of BGC-823 cells after transfection. (D) Western blots were performed to detect HDAC5 expression after transfection in BGC-823 cells. (DOC 1991 kb)

Estrogen receptors (ER) are expressed in approximately 65% of human breast cancer. Clinical trials and retrospective analyses showed that ER-positive (ER+) tumors were more vulnerable to development of chemotherapy resistance than ER-negative (ER-) tumors. The underlying mechanism is still to be elucidated. Aberrant DNA methylation has been recognized to be associated with cancer chemotherapy resistance. Recently, steroid hormone and their receptors have been found to be involved in the regulation of methyltransferases (DNMTs) and thereby contribute to chemotherapy resistance. The purpose of this study is to explore whether ERα could directly regulate the DNMTs expression. We first analyzed the methylation alterations and its correlation with the expression levels of three types of DNMTs in our established paclitaxel-resistant breast cancer lines, MCF-7(ER+)/PTX and MDA-MB-231(ER-)/PTX cell lines, using qMSP, real-time PCR and Western blot. Then we determined the function of ERα in regulation of DNMT1 using luciferase report gene systems. Our data demonstrated for the first time that ERα could upregulate DNMT1 expression by directly binding to the DNMT1 promoter region in MFC-7(ER+)/PTX cells.

Drug-induced aberrant DNA methylation is the first identified epigenetic marker involved in chemotherapy resistance. Understanding how the aberrant DNA methylation is acquired would impact cancer treatment in theory and practice. In this study we systematically investigated whether and how ERα propelled aberrant global DNA hypermethylation in the context of breast cancer drug resistance. Our data demonstrated that anticancer drug paclitaxel (PTX) augmented ERα binding to the DNMT1 and DNMT3b promoters to activate DNMT1 and DNMT3b genes, enhancing the PTX resistance of breast cancer cells. In support of these observations, estrogen enhanced multi-drug resistance of breast cancer cells by up-regulation of DNMT1 and DNMT3b genes. Nevertheless, the aberrant global DNA hypermethylation was dominantly induced by ERα-activated-DNMT1, since DNMT1 over-expression significantly increased global DNA methylation and DNMT1 knockdown reversed the ERα-induced global DNA methylation. Altering DNMT3b expression had no detectable effect on global DNA methylation. Consistently, the expression level of DNMT1 was positively correlated with ERα in 78 breast cancer tissue samples shown by our immunohistochemistry (IHC) analysis and negatively correlated with relapse-free survival (RFS) and distance metastasis-free survival (DMFS) of ERα-positive breast cancer patients. This study provides a new perspective for understanding the mechanism underlying drug-resistance-facilitating aberrant DNA methylation in breast cancer and other estrogen dependent tumors.