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Abstract Tumor spread through air spaces (STAS) is a distinctive metastatic pattern affecting prognosis in lung adenocarcinoma (LUAD) patients. Several challenges are associated with STAS detection, including misdetection, low interobserver agreement, and lack of quantitative analysis. In this research, a total of 489 digital whole slide images (WSIs) were collected. The deep learning-based STAS detection model, named STASNet, was constructed to calculate semi-quantitative parameters associated with STAS density and distance. STASNet demonstrated an accuracy of 0.93 for STAS detection at the tiles level and had an AUC of 0.72–0.78 for determining the STAS status at the WSI level. Among the semi-quantitative parameters, T10S, combined with the spatial location information, significantly stratified stage I LUAD patients on disease-free survival. Additionally, STASNet was deployed into a real-time pathological diagnostic environment, which boosted the STAS detection rate and led to the identification of three easily misidentified types of occult STAS.

ABSTRACT Background Early‐stage non–small cell lung cancer (NSCLC) is being diagnosed increasingly, and in 30% of diagnosed patients, recurrence will develop within 5 years. Thus, it is urgent to identify recurrence‐related markers to optimize the management of patient‐tailored therapeutics. Methods The eligible datasets were downloaded from TCGA and GEO. In the discovery phase, two algorithms, least absolute shrinkage and selector operation and support vector machine‐recursive feature elimination, were used to identify candidate genes. The recurrence‐associated signature was developed by penalized Cox regression. The nomogram was constructed and further tested via other independent cohorts. Results In this retrospective study, 14 eligible datasets and 7 published signatures were included. A 13‐gene based signature was generated by penalized Cox regression categorized training cohort into high‐risk and low‐risk subgroups (HR = 8.873, 95% CI: 4.228–18.480 p

Abstract Super-enhancers (SEs) are regulatory element clusters related to cell identity and disease. While the studies illustrating the function of SE-associated long noncoding RNAs (lncRNAs) in lung adenocarcinoma (LUAD) remains few. In our research, a SE-driven lncRNA, LINC00880, was identified, which showed higher expression in LUAD compared to normal tissues and indicated worse outcomes in stage I LUADs. We found that the transcription factor (TF) FOXP3 could simultaneously occupy the promoter and SE regions of LINC00880 to promote its transcription. The oncogenic function of LINC00880 was validated both in vitro and in vivo. Mechanically, LINC00880 binds to the protein CDK1 to increase its kinase activity, which rely on the phosphorylation state of pT161 in CDK1. LINC00880 also promotes the interaction between CDK1 and PRDX1. Moreover, LINC00880 interacts with PRDX1, which indicates that LINC00880 acts as a protein scaffold between CDK1 and PRDX1 to form a ternary complex, thereby resulting in the activation of PI3K/AKT to promote malignancy. Our results reveal that the SE-associated lncRNA LINC00880 regulates the CDK1/PRDX1 axis to sustain the malignancy of LUAD, providing a novel therapeutic target.

Background: The profile of immune-related adverse events (irAEs) due to programmed death-1 (PD-1) inhibitors-based combination therapy in advanced non-small cell lung cancer (NSCLC) and its relationship with survival have not been fully described. Objective: Designed to capture the spectrum of irAEs and explore the association between irAEs and clinical outcomes in patients with NSCLC. Design: This retrospective single-center study included patients with advanced NSCLC treated with PD-1 inhibitors (mainly in combination with chemotherapy) at Jiangsu Cancer Hospital. Methods: The relationship between irAEs and survival was explored using landmark analysis and time-dependent Cox regression. The subgroup analyses focused on investigating the effects of organ-specific irAE, irAE grade, and steroid dose used to treat irAE. Results: This study included 301 patients, 199 of whom received PD-1 inhibitors plus chemotherapy. The most common irAEs were skin toxicity (19.3%), endocrinopathy (21.3%), and pneumonitis (17.6%). In the entire cohort, the median progression-free survival (PFS) for patients developing and not developing irAE was 12.3 and 10.7 months ( p < 0.001), and the median overall survival (OS) was 23.5 months and 20.1 months ( p = 0.137), respectively. Subgroup analyses indicated that grade 3 or higher irAE, high steroid dose, and immune-related pneumonitis were detrimental to OS, whereas skin toxicity was beneficial to survival. These findings were further corroborated by both landmark analyses and Cox regression models conducted over four time points (1, 3, 6, and 12 months). Conclusion: In the real world, NSCLC patients receiving PD-1 inhibitor-based combination therapy (particularly combined with chemotherapy) experience longer PFS with irAE, though not necessarily OS. Immune-related skin toxicity is associated with a better prognosis, whereas pneumonitis grade ⩾3 irAE and high steroid dose compromise survival. Clinicians should remain cognizant of the organ-specific manifestations of irAE and take proactive measures to mitigate the progression of irAE.

Abstract Lung adenocarcinoma (LUAD) exhibits high heterogeneity and is well known for its high genetic variation. Recently, the understanding of non-genetic variation provides a new perspective to study the heterogeneity of LUAD. Little is known about whether super-enhancers (SEs) may be primarily responsible for the inter-tumor heterogeneity of LUAD. We used super-enhancer RNA (seRNA) levels of a large-scale clinical well-annotated LUAD cohort to stratify patients into three clusters with different prognosis and other malignant characteristics. Mechanistically, estrogen-related receptor alpha (ERRα) in cluster 3-like cell lines acts as a cofactor of BRD4 to assist SE-promoter loops to activate glycolysis-related target gene expression, thereby promoting glycolysis and malignant progression, which confers a therapeutic vulnerability to glycolytic inhibitors. Our study identified three groups of patients according to seRNA levels, among which patients in cluster 3 have the worst prognosis and vulnerability of glycolysis dependency. We also proposed a 3-TF index model to stratify patients with glycolysis-addicted tumors according to tumor SE stratification.

Abstract Tertiary lymphoid structures (TLSs) are considered to have a good prognosis in multiple solid tumors. However, the prognostic value of TLS in esophageal squamous cell carcinoma (ESCC) is unknown. In this study, we retrospectively enrolled 185 ESCC patients who underwent surgical resection. Hematoxylin and eosin staining was performed to investigate the presence, the abundance, the maturation, and the location of TLSs. We explored the cellular composition of TLSs using traditional immunohistochemistry in serial sections. The prognostic value of TLSs was investigated by univariate and multivariate analyses. A nomogram was constructed to predict the prognosis. TLS‐positive tumors were infiltrated with more CD45+ leukocytes, CD20+ B cells, CD4+ and CD8+ T cells, and CD11c+ dendritic cells（DCs） compared with negative tumors. Kaplan–Meier curves showed that the presence and the abundance of TLSs were associated with longer disease‐free survival (DFS) (p = 0.0130) and overall survival (OS) (p = 0.0164). In addition, patients with tumors containing more CD20+ B cell infiltration had longer DFS (p = 0.0105) and OS (p = 0.0341). Multivariate analyses demonstrated that the presence of TLSs was an independent prognostic factor for DFS (hazard ratio [HR] = 0.384, p

Abstract Background Lung adenocarcinoma (LUAD) is the leading cause of death worldwide. However, the roles of long noncoding RNAs (lncRNAs) hijacked by super-enhancers (SEs), vital regulatory elements of the epigenome, remain elusive in the progression of LUAD metastasis. Methods SE-associated lncRNA microarrays were used to identify the dysregulated lncRNAs in LUAD. ChIP-seq, Hi-C data analysis, and luciferase reporter assays were utilized to confirm the hijacking of LINC01977 by SE. The functions and mechanisms of LINC01977 in LUAD were explored by a series of in vitro and in vivo assays. Results We found that LINC01977, a cancer-testis lncRNA, was hijacked by SE, which promoted proliferation and invasion both in vitro and in vivo. LINC01977 interacted with SMAD3 to induce its nuclear transport, which facilitated the interaction between SMAD3 and CBP/P300, thereby regulating the downstream target gene ZEB1. Additionally, SMAD3 up-regulated LINC09177 transcription by simultaneously binding the promoter and SE, which was induced by the infiltration of M2-like tumor-associated macrophages (TAM2), subsequently activating the TGF-β/SMAD3 pathway. Moreover, LINC01977 expression was positively correlated with TAM2 infiltration and SMAD3 expression, especially in early-stage LUAD. Higher chromatin accessibility in the SE region of LINC01977 was observed with high expression of TGF-β. Early-stage LUAD patients with high LIN01977 expression had a shorter disease-free survival. Conclusions TAM2 infiltration induced a rich TGF-β microenvironment, activating SMAD3 to bind the promoter and the SE of LINC01977, which up-regulated LINC01977 expression. LINC01977 also promoted malignancy via the canonical TGF-β/SMAD3 pathway. LINC01977 hijacked by SE could be a valuable therapeutic target, especially for the treatment of early-stage LUAD.

Background It has been reported that smoking history as a predictor of immunotherapy efficacy in patients with advanced lung cancer, however, the underlying mechanisms of this phenomenon remain largely unknown.Methods The patients with lung adenocarcinoma’s (LUAD) cohort and the orthotopical transplanted mouse model were used to explore the correlation between smoking status and tertiary lymphoid structure (TLS) and chemokine CCL21, respectively. Cell adhesion and co-immunoprecipitation assays were performed to explore the interaction between CD4+T cells and CD20+B cells under tobacco exposure. Chromatin immunoprecipitation-PCR was used to dissect the mechanism of upregulated CCL21 secretion in tobacco treatment. Serum CCL21 level was recorded in patients with LUAD treated with immunotherapy.Results Here we observed that individuals with a smoking history exhibit an increased quantity and maturation level of TLS compared with non-smokers, along with higher levels of CCL21 secretion. Tobacco exposure promoted CCL21 expression in an epithelial cell-intrinsic manner, of which BaP, the main component of tobacco, facilitated the nuclear retention of the aryl hydrocarbon receptor that occupied the promoter of CCL21. Additionally, the activated CCL21/CCR7 axis increased the CD11a expression of CD4+T cells, boosting the interaction with CD20+B cells dependent on ICAM1, which potentially induced the TLSs formation. Patients with elevated serum levels of CCL21 benefited more from immunotherapy.Conclusions Patients with a smoking history exhibited higher levels of TLS via the CCL21-dependent mechanism, serum CCL21 was identified as a reliable biomarker for predicting the efficacy of immunotherapy.

Abstract Background This study aimed to develop a reliable immune signature based on B-cell proportion to predict the prognosis and benefit of immunotherapy in LUAD. Methods The proportion of immune cells in the TCGA-LUAD dataset was estimated using MCP-counter. The Least Absolute Shrinkage and Selector Operation was used to identify a prognostic signature and validated in an independent cohort. We used quantitative reverse transcription-polymerase chain reaction (qRT-PCR) data and formalin-fixed paraffin-embedded (FFPE) specimens immunohistochemistry to illustrate the correlation between prognostic signature and leukocyte migration. Results We found that the relative abundance of B lineage positively correlated with overall survival. Then, we identified a 13-gene risk-score prognostic signature based on B lineage abundance in the testing cohort and validated it in a cohort from the GEO dataset. This model remained strongly predictive of prognoses across clinical subgroups. Further analysis revealed that patients with a low-risk score were characterized by B-cell activation and leukocyte migration, which was also confirmed in FFPE specimens by qRT-PCR and immunohistochemistry. Finally, this immune signature was an independent prognostic factor in the composite nomogram of clinical characteristics. Conclusions In conclusion, the 13-gene immune signature based on B-cell proportion may serve as a powerful prognostic tool in LUAD.

Aberrant expression of circular RNAs (circRNAs) is involved in cancer progression through interaction with RNA-binding proteins (RBPs). Herein, we screened circRNA expression of A549 cells in circBase and the crosslinking immunoprecipitation (CLIP) data of human antigen R (HuR), an extensively studied RBP, and identified a circRNA, circ-defective in cullin neddylation 1 domain containing 4 (circDCUN1D4), originating from the DCUN1D4 gene transcript. circDCUN1D4 is downregulated in tumor samples under the mediation of DExH-box helicase 9 (DHX9), which inhibits the formation of circRNA by binding inverted repeat Alus (IRAlus) in flanking sequences. circDCUN1D4 depletion promoted invasion in vitro and metastasis in vivo. Importantly, the interaction between circDCUN1D4 and HuR increased the transportation of HuR to the cytoplasm. circDCUN1D4 acts as a scaffold to facilitate the interaction between the HuR protein and thioredoxin-interacting protein (TXNIP) mRNA, which enhances the stability of the TXNIP mRNA. Additionally, circDCUN1D4 directly interacts with TXNIP mRNA through base complementation, indicating the formation of the circDCUN1D4/HuR/TXNIP RNA-protein ternary complex. Furthermore, circDCUN1D4 suppressed metastasis and glycolysis of lung cancer cells in a TXNIP-dependent manner. Clinically, the downregulated expression of circDCUN1D4 was more prevalent in lymph node metastatic tissues and served as an independent risk factor for the overall survival of lung adenocarcinoma (LUAD) patients. These findings demonstrated that a novel circRNA, circDCUN1D4, is involved in the metastasis and glycolysis of LUAD.

Abstract Background Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive cancers. The two major lethal causes of ESCC are diagnosis at an advanced stage and lymph node metastasis (LNM). Circular RNAs (circRNAs) play critical regulatory roles in cancer progression, though, largely through unclear mechanisms. However, the character of circRNAs in the malignant progression of ESCC remains unclear. Methods The circRNA microarray was used to explore the circRNAs that were differentially expressed between ESCC and paired adjacent normal tissues. The function of circIMMP2L was validated by gain or loss of function assays. Pull‐down, RNA immunoprecipitation assays were used to demonstrate the biological mechanism of circIMMP2L. Tissue microarray (TMA), specimen, and paired plasma were investigated to evaluate the clinical significance of circIMMP2L. Results CircIMMP2L, commonly upregulated in tumor and plasma from advanced‐stage ESCC patients and LNM patients, predicts poorer patient survival. CircIMMP2L was also found to be a significant indicator for LNM, even in the T1 stage of ESCC. CircIMMP2L depletion suppressed the malignant progression of ESCC both in vitro and in vivo. Mechanistically, cytoplasmic circIMMP2L interacted with CtBP1 and facilitated the nuclear retention of CtBP1 in a CtBP2‐independent manner. Moreover, circIMMP2L promoted the interaction of CtBP1 with HDAC1 in the nucleus, which is essential for epigenetic remodeling and transcriptional suppression of E‐cadherin and p21. Conclusions These findings demonstrated that circIMMP2L promotes the malignant progression of ESCC mediated by CtBP1 nuclear retention and is a robust biomarker for the diagnosis, prognosis, and LNM in ESCC. Further, the findings extend our knowledge about the mechanism of circRNA regulation of gene transcription through epigenetics.

Background FLOT1 is a scaffolding protein of lipid rafts that is believed to be involved in numerous cellular processes. However, few studies have explored the function of FLOT1 in the development of lung adenocarcinoma (LUAD) and the underlying mechanisms of FLOT1 activity. Methods FLOT1 knockdown and overexpression models were constructed via lentivirus. Cell growth, invasion, migration, and apoptosis were detected to evaluate the role of FLOT1 in LUAD development. Epithelial–mesenchymal transition (EMT) and cell cycle regulatory markers were then examined. Finally, the influence of FLOT1 on the Erk/Akt signaling pathway was investigated. Results FLOT1 promoted cell growth, invasion, and migration and inhibited cell apoptosis. In addition, FLOT1 induced EMT and modulated the cell cycle by activating the Erk/Akt signaling pathway. Conclusion The findings indicate a significant role of FLOT1 in LUAD development. Targeting FLOT1 may be a potential therapeutic strategy for LUAD.

Long noncoding RNAs (lncRNAs) have recently received growing substantial attention in cancer research due to their important roles in various cancer types. However, the underlying mechanisms and functions of lncRNAs, especially in lung adenocarcinoma (LUAD), remain elusive. Based on pan-cancer screening analyses, we identified that the noncoding RNA LINC00665 was up-regulated in lung adenocarcinoma, which was subsequently confirmed in clinical samples and cell lines. Higher expression of LINC00665 was positively associated with poor prognosis and advanced T stage. Next, using gain- and loss- of function approaches, we revealed that LINC00665 promotes cell proliferation, cell migration, invasion, and suppresses cell apoptosis in LUAD through in vitro and in vivo experiments. Additionally, our findings showed that LINC00665 was predominately localized in the cytoplasm so as to interact with Ago2 protein, which could function as miRNA sponges. The results of bioinformatics prediction and RNA pull-down assay indicated that LINC00665 directly interacted with miR-195-5p. This was also confirmed by fluorescence colocalization. Furthermore, luciferase reporter assay demonstrated that Myc binding protein (MYCBP, also called AMY-1), which enhanced c-Myc transcriptional activity, was the target gene of LINC00665 dependent on miR-195-5p. Finally, rescue functional assay results uncovered that the oncogenic capability of LINC00665 was dependent on miR-195-5p and c-Myc transcriptional activity. In summary, this work elucidates that LINC00665 accelerates LUAD progression via the miR-195-5p/MYCBP axis by acting as a competing endogenous RNA (ceRNA), suggesting that LINC00665 may represent a potential therapeutic target for clinical intervention of LUAD.

Objective: Identification of tumor invasiveness of pulmonary adenocarcinomas before surgery is one of the most important guides to surgical planning. Additionally, preoperative diagnosis of lung adenocarcinoma with micropapillary patterns is also critical for clinical decision making. We aimed to evaluate the accuracy of deep learning models on classifying invasiveness degree and attempted to predict the micropapillary pattern in lung adenocarcinoma.Methods: The records of 291 histopathologically confirmed lung adenocarcinoma patients were retrospectively analyzed and consisted of 61 adenocarcinoma in situ, 80 minimally invasive adenocarcinoma, 117 invasive adenocarcinoma, and 33 invasive adenocarcinoma with micropapillary components (>5%). We constructed two diagnostic models, the Lung-DL model and the Dense model, based on the LeNet and the DenseNet architecture, respectively.Results: For distinguishing the nodule invasiveness degree, the area under the curve (AUC) value of the diagnosis with the Lung-DL model is 0.88 and that with the Dense model is 0.86. In the prediction of the micropapillary pattern, overall accuracies of 92 and 72.91% were obtained for the Lung-DL model and the Dense model, respectively.Conclusion: Deep learning was successfully used for the invasiveness classification of pulmonary adenocarcinomas. This is also the first time that deep learning techniques have been used to predict micropapillary patterns. Both tasks can increase efficiency and assist in the creation of precise individualized treatment plans.

Background Developments in high‐throughput genomic technologies have led to improved understanding of the molecular underpinnings of esophageal squamous cell carcinoma (ESCC). However, there is currently no model that combines the clinical features and gene expression signatures to predict outcomes. Methods We obtained data from the GSE53625 database of Chinese ESCC patients who had undergone surgical treatment. The R packages, Limma and WGCNA, were used to identify and construct a co‐expression network of differentially expressed genes, respectively. The Cox regression model was used, and a nomogram prediction model was constructed. Results A total of 3654 differentially expressed genes were identified. Bioinformatics enrichment analysis was conducted. Multivariate analysis of the clinical cohort revealed that age and adjuvant therapy were independent factors for survival, and these were entered into the clinical nomogram. After integrating the gene expression profiles, we identified a “2‐gene score” associated with overall survival. The combinational model is composed of clinical data and gene expression profiles. The C‐index of the combined nomogram for predicting survival was statistically higher than the clinical nomogram. The calibration curve revealed that the combined nomogram and actual observation showed better prediction accuracy than the clinical nomogram alone. Conclusions The integration of gene expression signatures and clinical variables produced a predictive model for ESCC that performed better than those based exclusively on clinical variables. This approach may provide a novel prediction model for ESCC patients after surgery.

Abstract Background Glyphosate-based herbicides (GBHs) are broad-spectrum herbicides that act on the shikimate pathway in bacteria, fungi, and plants. The possible effects of GBHs on human health are the subject of an intense public debate for both its potential carcinogenic and non-carcinogenic effects, including its effects on microbiome. The present pilot study examines whether exposure to GBHs at doses of glyphosate considered to be “safe” (the US Acceptable Daily Intake - ADI - of 1.75 mg/kg bw/day), starting from in utero, may modify the composition of gut microbiome in Sprague Dawley (SD) rats. Methods Glyphosate alone and Roundup, a commercial brand of GBHs, were administered in drinking water at doses comparable to the US glyphosate ADI (1.75 mg/kg bw/day) to F0 dams starting from the gestational day (GD) 6 up to postnatal day (PND) 125. Animal feces were collected at multiple time points from both F0 dams and F1 pups. The gut microbiota of 433 fecal samples were profiled at V3-V4 region of 16S ribosomal RNA gene and further taxonomically assigned and assessed for diversity analysis. We tested the effect of exposure on overall microbiome diversity using PERMANOVA and on individual taxa by LEfSe analysis. Results Microbiome profiling revealed that low-dose exposure to Roundup and glyphosate resulted in significant and distinctive changes in overall bacterial composition in F1 pups only. Specifically, at PND31, corresponding to pre-pubertal age in humans, relative abundance for Bacteriodetes (Prevotella) was increased while the Firmicutes (Lactobacillus) was reduced in both Roundup and glyphosate exposed F1 pups compared to controls. Conclusions This study provides initial evidence that exposures to commonly used GBHs, at doses considered safe, are capable of modifying the gut microbiota in early development, particularly before the onset of puberty. These findings warrant future studies on potential health effects of GBHs in early development such as childhood.

Systems biology provides an opportunity to discover the role that gut microbiota play in almost all aspects of human health. Existing evidence supports the hypothesis that gut microbiota is closely related to the pharmacological effects of chemical therapy and novel targeted immunotherapy. Gut microbiota shapes the efficiency of drugs through several key mechanisms: metabolism, immunomodulation, translocation, enzymatic degradation, reduction of diversity, and ecological variability. Therefore, gut microbiota have emerged as a novel target to enhance the efficacy and reduce the toxicity and adverse effects of cancer therapy. There is growing evidence to show that cancer therapy perturbs the host immune response and results in dysbiosis of the immune system, which then influences the efficiency of the therapy. Studies suggest that gut microbes play a significant role in cancer therapy by modulating drug efficacy, abolishing the anticancer effect, and mediating toxicity. In this review, we outline the role of gut microbiota in modulating cancer therapy and the implications for improving the efficacy of chemotherapy and immunotherapy in clinical practice. We also summarize the current limitations of the safety and effectiveness of probiotics in cancer therapies such as personalized cancer therapy.

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer, which is the leading cause of cancer death. It is unclear whether the improved survival seen at high-volume centers applies to the general population and, more importantly, whether the improvement in lung cancer survival was just a consequence of improved screening work. Data from the Surveillance, Epidemiology, and End Results (SEER) registry was used to identify 405,580 patients with NSCLC diagnosed from 1988 to 2008. The patients were divided into four groups according to the year of diagnosis. Trends of clinical characteristics were analyzed to reflect the progress of screening work. Five-year relative survivals in various subgroups were compared. The results indicated that proportion of aged, advanced, and non-surgical patients increased, whereas patients with lymph node metastasis and high histology grade decreased. Improvements in all stages of NSCLC patients were demonstrated, with relatively more significant gains for patients with localized and regional disease. After potentially curative surgical resection, remarkable improvements were observed in both cohorts with time (surgical: 52.00%-63.00%; non-surgical: 6.10%-13.50%). Specifically, patients who underwent pneumonectomy, lobectomy/bilobectomy, and partial/wedge/segmental resection all presented better survival rates. Our SEER analysis demonstrated improvements among patients in all stages of NSCLC that were deemed attributable to improved therapy and medical care for NSCLC rather than improved screening work. [ABSTRACT FROM AUTHOR]

Metabolic reprogramming is a hallmark of cancer cells and is used by cancer cells for growth and survival. Pyruvate kinase muscle isozyme M2 (PKM2) is a limiting glycolytic enzyme that catalyzes the final step in glycolysis, which is key in tumor metabolism and growth. The present review discusses the expression and regulation of PKM2, and reports the dominant role that PKM2 plays in glycolysis to achieve the nutrient demands of cancer cell proliferation. In addition, the present study discusses the non-metabolic function of PKM2, and its role as a coactivator and protein kinase, which contributes to tumorigenesis. Furthermore, conflicting studies concerning the role of PKM2 as a therapeutic target are reviewed. The improved understanding of PKM2 may provide a noval approach for cancer treatment. [ABSTRACT FROM AUTHOR]

The association between polymorphic CAG repeats in the androgen receptor gene in women and breast cancer susceptibility has been studied extensively. However, the conclusions regarding this relationship remain conflicting. The purpose of this meta-analysis was to identify whether androgen receptor CAG repeat lengths were related to breast cancer susceptibility. The MEDLINE, PubMed, and EMBASE databases were searched through to December 2014 to identify eligible studies. Data and study quality were rigorously assessed by two investigators according to the Newcastle-Ottawa Quality Assessment Scale. The publication bias was assessed by the Begg's test. Seventeen eligible studies were included in this meta-analysis. The overall analysis suggested no association between CAG polymorphisms and breast cancer risk (odds ratio [OR] 1.031, 95% confidence interval [CI] 0.855-1.245). However, in the subgroup analysis, we observed that long CAG repeats significantly increased the risk of breast cancer in the Caucasian population (OR 1.447, 95% CI 1.089-1.992). Additionally, the risk was significantly increased in Caucasian women carrying two alleles with CAG repeats ?22 units compared with those with two shorter alleles (OR 1.315, 95% CI 1.014-1.707). These findings suggest that long CAG repeats increase the risk of breast cancer in Caucasian women. However, larger scale case-control studies are needed to validate our results. [ABSTRACT FROM AUTHOR]