Promotes Breast Cancer Proliferation Research Articles

Synergistic anticancer efficacy of polydatin and sorafenib against the MCF-7 breast cancer cell line via inhibiting of PI3K/AKT/mTOR pathway and reducing resistance to treatment

Polydatin (PD), a glucoside derivative of resveratrol, has been investigated for its potential to mitigate sorafenib (SOF) side effects and combat multidrug resistance in cancer treatment. The study evaluated its mechanism of action for inhibiting the protein kinase B/mTOR pathway in promoting breast cancer proliferation. The combined PD and SOF have synergistic effects with a combination index (CI) < 1 in the liver (HepG2) and breast (MCF-7) cancer cell lines. Molecular docking studies were conducted to analyze interactions of PD& SOF with protein kinases as well as apoptotic and multidrug resistance proteins, including AKT1, PI3K, mTOR, Apaf-1, and ABCB1 in MCF-7 cells. Experimental validation through real-time PCR confirmed. PD has a strong binding affinity, particularly with AKT1 (-56 kcal/mol) and ABCB1 (-27.16 kcal/mol), a gene associated with multidrug resistance. These interactions were linked to anti-proliferative anti-angiogenic effects and reduced resistance to treatment, demonstrating PD has potential therapeutic benefits. Furthermore, PD combined with SOF induced apoptosis, inhibited cell growth, and arrested MCF-7 cells in the sub-G1 phase with increased intracellular ROS. This was accompanied by reduced expression of AKT1 and ABCB1 genes, reinforcing the anticancer efficacy of PD/SOF combination therapy. In conclusion, the findings suggest that PD/SOF could serve as a promising anticancer treatment strategy, warranting further investigation for potential clinical applications and mechanistic studies in vivo.

The Role of Breastmilk in Macrophage-Tumour Cell Interactions in Postpartum Breast Cancer

Background: Lactation is associated with long-term reduced risk of breast cancer. However, there is a transient increased risk of breast cancer in the 5 to 10 years postpartum and this is associated with a high incidence of metastasis and mortality. Breastmilk is a physiological fluid secreted by the mammary glands intimately connected with breast cells and the microenvironment that may affect postpartum breast cancer development and progression. This study aims to investigate the effect of breastmilk on interactions between breast cancer cells and macrophages in vitro. Methods: Human breastmilk from healthy donors (n = 7) was pooled and incubated with breast cancer (MCF-7 and MDA-MB-231) and macrophage (RAW264.7) cell lines to assess cell proliferation, viability, migration, and expression of key genes associated with epithelial-mesenchymal transition (EMT) and macrophage phenotype. Indirect co-culture studies assessed the effect of breastmilk on interactions between breast cancer cells and macrophages. Results: Breastmilk increased the proliferation and viability of breast cancer cells, reduced EMT markers, and reduced cell migration in MDA-MB-231 cells. Breastmilk decreased mRNA expression of interleukin 1B (IL1B) and interleukin 10 (IL10) in macrophages. Reduced EMT marker expression was observed in breast cancer cells co-cultured with macrophages pre-treated with breastmilk. Macrophages co-cultured with breast cancer cells pre-treated with breastmilk exhibited increased expression of a pro-inflammatory cytokine tumor necrosis factor A (TNFA) and pro-inflammatory nitric oxide synthase 2 (NOS2), and reduced expression of cytokines IL10 and transforming growth factor B1 (TGFB1) which are associated with the alternatively-activated macrophage phenotype. Conclusions: Breastmilk has the potential to promote breast cancer proliferation, however, it can also reduce breast cancer progression through inhibition of breast cancer cell migration and regulation of macrophage polarisation. These findings suggest that breastmilk has potential to shape the tumour microenvironment in postpartum breast cancer.

KCNK1 promotes proliferation and metastasis of breast cancer cells by activating lactate dehydrogenase A (LDHA) and up-regulating H3K18 lactylation.

Breast cancer is the most prevalent malignancy and the most significant contributor to mortality in female oncology patients. Potassium Two Pore Domain Channel Subfamily K Member 1 (KCNK1) is differentially expressed in a variety of tumors, but the mechanism of its function in breast cancer is unknown. In this study, we found for the first time that KCNK1 was significantly up-regulated in human breast cancer and was correlated with poor prognosis in breast cancer patients. KCNK1 promoted breast cancer proliferation, invasion, and metastasis in vitro and vivo. Further studies unexpectedly revealed that KCNK1 increased the glycolysis and lactate production in breast cancer cells by binding to and activating lactate dehydrogenase A (LDHA), which promoted histones lysine lactylation to induce the expression of a series of downstream genes and LDHA itself. Notably, increased expression of LDHA served as a vicious positive feedback to reduce tumor cell stiffness and adhesion, which eventually resulted in the proliferation, invasion, and metastasis of breast cancer. In conclusion, our results suggest that KCNK1 may serve as a potential breast cancer biomarker, and deeper insight into the cancer-promoting mechanism of KCNK1 may uncover a novel therapeutic target for breast cancer treatment.

Suppression of Bcl3 Disrupts Viability of Breast Cancer Cells through Both p53-Dependent and p53-Independent Mechanisms via Loss of NF-κB Signalling.

The NF-κB co-factor Bcl3 is a proto-oncogene that promotes breast cancer proliferation, metastasis and therapeutic resistance, yet its role in breast cancer cell survival is unclear. Here, we sought to determine the effect of Bcl3 suppression alone on breast cancer cell viability, with a view to informing future studies that aim to target Bcl3 therapeutically. Bcl3 was suppressed by siRNA in breast cancer cell lines before changes in viability, proliferation, apoptosis and senescence were examined. Bcl3 suppression significantly reduced viability and was shown to induce apoptosis in all cell lines tested, while an additional p53-dependent senescence and senescence-associated secretory phenotype was also observed in those cells with functional p53. The role of the Bcl3/NF-κB axis in this senescence response was confirmed via siRNA of the non-canonical NF-κB subunit NFKB2/p52, which resulted in increased cellular senescence and the canonical subunit NFKB1/p50, which induced the senescence-associated secretory phenotype. An analysis of clinical data showed a correlation between reduced relapse-free survival in patients that expressed high levels of Bcl3 and carried a p53 mutation. Together, these data demonstrate a dual role for Bcl3/NF-κB in the maintenance of breast cancer cell viability and suggests that targeting Bcl3 may be more beneficial to patients with tumours that lack functional p53.

RACK1 facilitates breast cancer progression by competitively inhibiting the binding of β-catenin to PSMD2 and enhancing the stability of β-catenin

The receptor for activated C kinase 1 (RACK1) is a key scaffolding protein with multifunctional and multifaceted properties. By mediating protein-protein interactions, RACK1 integrates multiple intracellular signals involved in the regulation of various physiological and pathological processes. Dysregulation of RACK1 has been implicated in the initiation and progression of many tumors. However, the exact function of RACK1 in cancer cellular processes, especially in proliferation, remains controversial. Here, we show that RACK1 is required for breast cancer cell proliferation in vitro and tumor growth in vivo. This effect of RACK1 is associated with its ability to enhance β-catenin stability and activate the canonical WNT signaling pathway in breast cancer cells. We identified PSMD2, a key component of the proteasome, as a novel binding partner for RACK1 and β-catenin. Interestingly, although there is no interaction between RACK1 and β-catenin, RACK1 binds PSMD2 competitively with β-catenin. Moreover, RACK1 prevents ubiquitinated β-catenin from binding to PSMD2, thereby protecting β-catenin from proteasomal degradation. Collectively, our findings uncover a novel mechanism by which RACK1 increases β-catenin stability and promotes breast cancer proliferation.

RAB10 promotes breast cancer proliferation migration and invasion predicting a poor prognosis for breast cancer

RAB10, a member of the small GTPase family, has complex biological functions, but its role in breast cancer (BC) remains unclear. The aim of this study was to investigate the relationship between RAB10's role in BC, its biological functions, and BC prognosis. An online database was used to analyze the correlation between differential expression of RAB10 in BC and prognosis. The results of immunohistochemical assays in clinical cohorts were combined with the database analysis. The chi-square test and COX regression were employed to analyze the correlation between RAB10 and pathological features of BC. MTT, Transwell, and wound healing assays were conducted to detect BC cell proliferation, invasion, and metastatic ability. Bioinformatics techniques were employed to explore the correlation between RAB10 and BC tumor immune cell infiltration, and to speculate the biological function of RAB10 in BC and related signaling pathways. Our findings suggest that RAB10 expression is elevated in BC and is associated with HER2 status, indicating a poor prognosis for BC patients. RAB10 can promote the proliferation, migration, and invasion ability of BC cells in vitro. RAB10 is also associated with BC immune cell infiltration and interacts with multiple signaling pathways. RAB10 is a potential biomarker or molecular target for BC.

A novel RBBP8(p.E281*) germline mutation is a predisposing mutation in familial hereditary cancer syndrome.

Screening tumor susceptibility genes helps in identifying powerful biomarkers for hereditary cancer monitoring, prevention, and diagnosis, providing opportunities for understanding potential molecular mechanisms and biomarkers for the precise treatment of hereditary cancer syndromes. Whole-exome sequencing of blood and bioinformatics analysis uncovered a novel RBBP8(p.E281*) germline mutation in a family with hereditary cancer syndrome, which was verified by Sanger sequencing. Cell proliferation, colony formation, cell migration, and in vivo tumorigenesis were investigated by CCK8, colony formation, Transwell, and in vivo xenograft assays. Protein localization and interaction were detected by immunofluorescence, nuclear and cytoplasmic protein extraction kits, and Co-IP. A new heterozygous germline mutation of the RBBP8(p.E281*) gene was found to be associated with familial hereditary cancer syndrome. RBBP8-WT was mainly detected in the nucleus and interacts with BRCA1. In contrast, RBBP8(p.E281*) is mainly located in the cytoplasm, with no interaction with BRCA1. RBBP8(p.E281*) variant plays an oncogenic role in the cytoplasm in addition to its loss of function in the nucleus, which promotes breast cancer proliferation, in vivo tumorigenesis, and migration. Compared with the control group, RBBP8(p.E281*) showed elevated cell death in response to cisplatin and olaparib treatment. A novel RBBP8(p.E281*) germline mutation was identified from familial hereditary cancer syndrome. RBBP8(p.E281*) is not able to enter the nucleus or interact with BRCA1 through the lost binding motif, and RBBP8(p.E281*) variant appears to promote tumorigenesis in the cytoplasm in addition to its loss of function in the nucleus. RBBP8(p.E281*) variant may promote tumor susceptibility and serve as a precision medicine biomarker in familial hereditary cancer syndrome. KEY MESSAGES: RBBP8(p.E281*) is a susceptibility gene in this familial hereditary cancer syndrome RBBP8(p.E281*) lost its ability to enter the nucleus and the BRCA1 binding motif A novel RBBP8(p.E281*) germline mutation promotes breast cancer tumorigenesis Patients with RBBP8(p.E281*) germline mutation may benefit from Olaparib, Cisplatin.

WTAP Mediates NUPR1 Regulation of LCN2 Through m6A Modification to Influence Ferroptosis, Thereby Promoting Breast Cancer Proliferation, Migration and Invasion.

Ferroptosis is involved in various pathophysiological diseases, including triple-negative breast cancer (TNBC). Targeting ferroptosis is considered as a novel anti-TNBC strategy. Nevertheless, the regulatory mechanism of ferroptosis during TNBC progression is unclear. Here, the role of WTAP in ferroptosis during TNBC progression was investigated.The clinicopathological significance of WTAP, NUPR1 and LCN2 was analyzed by Kaplan-Meier method. Cell viability was assessed using MTT assay. Transwell assay was employed to analyze cell migration and invasion. GSH/GSSG and Fe2+ levels in TNBC cells were analyzed using kits. m6A level was examined using m6A dot blot assay. NUPR1 mRNA stability was analyzed using RNA degradation assay. RIP was performed to analyze the interaction between eIF3a and NURP1.Herein, our results revealed that WTAP, NUPR1 and LCN2 expressions were significantly elevated in TNBC. NUPR1 silencing inhibited TNBC cell proliferation, migration and invasion by inducing ferroptosis. NUPR1 positively regulated LCN2 expression in TNBC cells, and LCN2 knockdown induced ferroptosis to suppress TNBC cell malignant behaviors. Our molecular study further revealed that WTAP promoted NUPR1 expression in an m6A-EIF3A mediated manner. And, as expected, WTAP knockdown promoted ferroptosis to suppress TNBC cell malignant behaviors, which were abrogated by NUPR1 overexpression.WTAP upregulated LCN2 by regulation of NUPR1 m6A modification, thereby suppressing ferroptosis to contribute to accelerate TNBC progression. Our study revealed the cancer-promoting effect of WTAP, NUPR1 and LCN2 in TNBC and clarified the relevant mechanism, providing a theoretical basis for developing novel diagnostic and therapeutic strategies for TNBC.

PAX5-miR-142 feedback loop promotes breast cancer proliferation by regulating DNMT1 and ZEB1

BackgroundBreast cancer is one of the most common malignancies occurred in female around the globe. Recent studies have revealed the crucial characters of miRNA and genes, as well as the essential roles of epigenetic regulation in breast cancer initiation and progression. In our previous study, miR-142-3p was identified as a tumor suppressor and led to G2/M arrest through targeting CDC25C. However, the specific mechanism is still uncertain.MethodsWe identified PAX5 as the upstream regulator of miR-142-5p/3p through ALGGEN website and verified by series of assays in vitro and in vivo. The expression of PAX5 in breast cancer was detected by qRT-PCR and western blot. Besides, bioinformatics analysis and BSP sequencing were performed to analyze the methylation of PAX5 promoter region. Finally, the binding sites of miR-142 on DNMT1 and ZEB1 were predicted by JASPAR, and proved by luciferase reporter assay, ChIP analysis and co-IP.ResultsPAX5 functioned as a tumor suppressor by positive regulation of miR-142-5p/3p both in vitro and in vivo. The expression of PAX5 was regulated by the methylation of its promoter region induced by DNMT1 and ZEB1. In addition, miR-142-5p/3p could regulate the expression of DNMT1 and ZEB1 through binding with their 3’UTR region, respectively.ConclusionIn summary, PAX5-miR-142-DNMT1/ZEB1 constructed a negative feedback loop to regulate the progression of breast cancer, which provided emerging strategies for breast cancer therapy.

EIF4A3-induced circZFAND6 promotes breast cancer proliferation and metastasis through the miR-647/FASN axis

AimsCircular RNAs (circRNAs) are important regulators in breast cancer progression. However, the underlying mechanism of circRNAs functions in breast cancer remain largely unclear. Main methodsTo investigate the circRNAs expression pattern in breast cancer, high-throughput circRNA microarray assay was used. The top up-regulated circRNA, circZFAND6, was submitted to further experiments, including cell counting kit-8 (CCK-8) assay, colony formation assay, transwell assay and mouse xenograft assay. To investigate the underlying mechanism of circZFAND6 function in breast cancer progression, luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted. Key findingsWe found a novel circRNA, circZFAND6, was up-regulated in breast cancer tissues and cell lines. Inhibition of circZFAND6 reduced proliferation and metastasis of breast cancer. Mechanically, circZFAND6 acted as a competing endogenous RNA (ceRNA) to sponge miR-647 and increase fatty acid synthase (FASN) expression. And eukaryotic translation initiation factor 4A3 (EIF4A3) was found to bind to circZFAND6 pre-mRNA transcript upstream region, leading to the high expression of circZFAND6 in breast cancer. Inhibition of EIF4A3 also suppressed proliferation and metastasis of breast cancer. SignificanceEIF4A3-induced circZFAND6 up-regulation promoted proliferation and metastasis of breast cancer through the miR-647/FASN axis. Our results uncovered a possible mechanism underlying breast cancer progression and might provide a breast cancer treatment target.

Abstract 341: Critical role of defensins in respiratory viral infection induced breast cancer progression

Abstract Respiratory viral infections (RVI) such as influenza and COVID19 impact the host systemic immune system along with causing deleterious chronic inflammatory responses and respiratory distress. While the role of chronic inflammation in cancer is well-established, the role of RVI on tumorigenesis is poorly defined. To study the role of RVI on breast cancer, we first infected murine respiratory epithelial cells (mRES) with murine sendai virus (mSV), an analog for human parainfluenza virus. These infected mRES were co-cultured with 4T1 murine breast cancer cells in 1:1 dilution on a single 2D plate and also in trans-well format. Both in co-culture and transwell culture we saw a 40-80% (p&amp;lt;0.05) increased proliferation of breast cancer cells. Similarly, when 4T1 cells were treated with the supernatant collected from infected mRES cells in 1:5 dilution, also demonstrated a 2.3 fold increased breast cancer cell proliferation. The cytokine analysis from the supernatant collected from infected mRES cells demonstrated a 17-23 fold enhanced secretion of α/β-defensins. Direct treatment of α-defensin (cyptidin-4, 10 pg/mL) and β-defensin-3 (mBD3, 20 pg/mL) on 4T1 cells demonstrated enhanced expression of chemokine metastatic receptor, CXCR4 (4.3 fold), angiogenic factor, VEGF (12.8 fold) and cell division favoring factor, CDK2 (8.1 fold). Further, analysis of infected mRES cells demonstrated upregulation of toll-like receptor 2 (TLR2) and NOD-like receptor protein 3 (NLRP3) expression. Interesting, co-cultured of infected mRES with syngeneic murine CD4 T cells induced exhaustion phenotype (PD1+ and CTLA4+) differentiation of CD4 T cells. Taken together, these data suggest that respiratory viral infections through induction of cancer cell proliferation and inhibiting anti-tumor adaptive immune responses promote breast cancer proliferation. Citation Format: Umer Ali, Venkataswarup Tiriveedhi. Critical role of defensins in respiratory viral infection induced breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 341.

Inhibition of lncRNA PCAT19 promotes breast cancer proliferation.

Breast cancer (BC) is the most common malignancy affecting women. It is vital to explore sensitive biological markers to diagnose and treat BC patients. Recent studies have proved that long noncoding RNAs (lncRNAs) were involved in breast tumor progression. Nonetheless, whether lncRNA prostate cancer-associated transcript 19 (PCAT19) impacts BC development remains unknown. We performed various bioinformatic analyses, including machine learning models to identify critical regulatory lncRNAs affecting prognosis in BC. The in situ hybridization (ISH) assay was carried out to confirm the expression levels of lncRNA PCAT19 in tissue specimens. MTT assay, wound healing assay, and transwell assay were performed to investigate PCAT19's impact on proliferation, migration, and invasion of BC cells. Mouse xenografts were used to examine the proliferation-inhibiting function of PCAT19 in vivo. Among the prognosis-associated lncRNAs, PCAT19 predicted a favorable prognosis in BC. Patients with high expression levels of PCAT19 had a lower clinical stage and less lymph node metastasis. The PCAT19-related genes were enriched in signaling pathways involved in tumor development, indicating PCAT19 was an essential regulator of BC. Using the ISH assay, we confirmed the expression level of lncRNA PCAT19 in human BC tissues was lower than normal breast tissues. Moreover, the knockdown of PCAT19 further confirmed its inhibiting ability in BC cell proliferation. Correspondingly, overexpressing PCAT19 reduced tumor size in mouse xenografts. Our study demonstrated that lncRNA PCAT19 suppressed the development of BC. PCAT19 might be a promising prognostic biomarker, which provides new insights into risk stratification for BC patients.

Abstract P1-05-33: RNA in Extracellular vesicles used for the prediction of distant metastasis of breast cancer and the function of TGM2 in promoting breast cancer development

Abstract Background: Extracellular vesicles (EVs) can be released by living cells during the process of tumor metastasis. Since EVs could contain various of molecular with high stability, a growing number of evidences indicated that those molecular can be utilized as biomarkers of liquid biopsy for metastatic prediction. Therefore, we aimed to identify genes and build a model that can predict the risk of metastasis in breast cancer patients with acceptable sensitivity and accuracy. Methods: Pretreatment plasma EV-RNAs of patients diagnosed at Fudan University Shanghai Cancer Center from 2017 to 2018 were extracted and analyzed by next generation sequencing (NGS) and bioinformatics, including breast cancer patients (n=114) and benign cases (n=18). Weighted correlation network analysis (WGCNA) was utilized to determine the relationship between clinical features and genes. The Kaplan-Meier was used for survival analysis in public database. By 100 times of 5 folds cross-validation, we used logistic regression analysis to set up the model. The receiver operating characteristic curve (ROC) and area under curve (AUC) were used to assess the predicted capacity of the model. QRT-PCR was conducted to further confirm the expression of genes selected by the predicting model in 175 breast cancer patients with and without metastasis, along with 5 EV-RNAs of tumor samples and paired normal adjacent breast tissues. The functions of candidate genes on cell proliferation, metastasis, and invasion were determined by a series of in vitro experiments in cancer lines. RNA sequencing and bioinformatic analysis were performed to explore the mechanism of the candidate genes. Moreover, co-immunoprecipitation (Co-IP) was used to reveal interacting proteins. Results: WGCNA screened 40 hub genes which were significantly associated with the distant metastasis in patients with breast cancer. A total of 207 upregulated genes were identified in patients with distant metastasis. After intersection, 6 genes were selected. Survival analysis suggested that high expression of IGFBP5, BCL6B, TGM2, and SH3PXD2A were correlated with poor distant metastasis-free survival (DMFS). The metastasis predicting model built based on those genes showed an AUC value of 0.923 with diagnostic accuracy of 91.2%. In the validation cohort, data showed the AUC value of each single gene were 0.835, 0.818, 0.845, 0.834, for TGM2, IGFBP5, BCL6B, and SH3PXD2A respectively. Among those four genes, TGM2 was significantly upregulated with clinical stages and correlated with poor prognosis. Moreover, TGM2 showed the highest abundance in tumor tissue EVs. Functional experiments revealed that TGM2 promoted breast cancer proliferation, metastasis, and invasion in vitro. The initially upregulated expression of TGM2 in EVs of cell lines was significantly decreased by adding the exosome release inhibitor GW4869. In addition, EVs from TGM2 overexpressed cells promoted cell migration and invasion of wild-type cells. Mechanistically, TGM2 was positively correlated with EMT, Hedgehog and IL6-JAK-STAT3 pathways. Co-IP assay found that TGM2 interacted with TMF1, which was an effector for degradation of STAT3 through the ubiquitin-proteasome pathway. Interfering the expression of TMF1 remarkably promoted the migration ability of cells and reversed by TGM2 overexpression. Conclusion: Based on the plasma EV-RNAs, we constructed a model with promising predicted capacity of distant metastasis in patients with breast cancer. TGM2, as the most effective predictor, can promote the progression and metastasis of breast cancer by targeting TMF1/STAT3. Key words Breast Cancer; Extracellular vesicles; Metastasis; Prediction model; TGM2 Citation Format: Jiong Wu, Yayun Chi. RNA in Extracellular vesicles used for the prediction of distant metastasis of breast cancer and the function of TGM2 in promoting breast cancer development [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-33.

5′-tRF-GlyGCC promotes breast cancer metastasis by increasing fat mass and obesity-associated protein demethylase activity

tRNA-derived fragments (tRFs) are a class of regulatory non-coding RNAs that play essential biological functions in cancer and stress-induced diseases. Several lines of evidence suggest that 5′-tRF-GlyGCC participates in tumor progression; however, its molecular mechanisms remain unclear. In this study, we explored the function of 5′-tRF-GlyGCC in breast cancer (BC) progression and studied the related potential molecular mechanisms. 5′-tRF-GlyGCC expression increased in human BC, and it promoted the proliferation, migration, and invasion of BC cells in vitro and tumor growth and metastasis in vivo. 5′-tRF-GlyGCC was found for the first time to bind directly to fat mass and obesity-associated proteins, and increase the activity of FTO demethylase, reducing eIF4G1 methylation, inhibiting autophagy, and promoting BC proliferation and metastasis. These findings suggest that 5′-tRF-GlyGCC might be a therapeutic target for treating BC.

BMI-1 promotes breast cancer proliferation and metastasis through different mechanisms in different subtypes.

Breast cancer is among the most common malignant cancers in women. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is a transcriptional repressor that has been shown to be involved in tumorigenesis, the cell cycle, and stem cell maintenance. In our study, increased expression of BMI-1 was found in both human triple negative breast cancer and luminal A-type breast cancer tissues compared with adjacent tissues. We also found that knockdown of BMI-1 significantly suppressed cell proliferation and migration in vitro and in vivo. Further mechanistic research demonstrated that BMI-1 directly bound to the promoter region of CDKN2D/BRCA1 and inhibited its transcription in MCF-7/MDA-MB-231. More importantly, we discovered that knockdown of CDKN2D/BRCA1 could promote cell proliferation and migration after repression by PTC-209. Our results reveal that BMI-1 transcriptionally suppressed BRCA1 in TNBC cell lines whereas, in luminal A cell lines, CDKN2D was the target gene. This provides a reference for the precise treatment of different types of breast cancer in clinical practice.

G3BP1 regulates breast cancer cell proliferation and metastasis by modulating PKCζ.

Breast cancer is a leading cause of death and morbidity among female cancers. Several factors, including hormone levels, lifestyle, and dysregulated RNA-binding proteins, have been associated with the development of breast cancer. Ras-GTPase-activating protein SH3 domain-binding protein 1 (G3BP1) and protein kinase C, Zeta isoform (PKCζ) are oncogenes implicated in numerous cancers, including breast cancer. However, their interaction and role in promoting breast cancer proliferation and metastasis have not been well-characterized. In the present study, we demonstrated that G3BP1 expression was elevated in breast cancer and that knockdown of G3BP1 diminished the proliferation and metastasis of breast cancer cells. Mechanistically, we identified proliferation and a series of metastasis-related properties, including chemotaxis, migration, Golgi polarity localization, and actin polymerization, that were modulated by G3BP1 knockdown. We found that G3BP1 and PKCζ were co-localized and interacted intracellularly, and they co-underwent membrane translocation under EGF stimulation. Following the knockdown of G3BP1, we observed the membrane translocation and phosphorylation of PKCζ were significantly impaired, suggesting that G3BP1 regulates the activation of PKCζ. Our findings indicate that G3BP1 plays multiple roles in breast cancer cell proliferation and metastasis. The activation of PKCζ by G3BP1 may be the specific mechanism underlying the process.

Upregulation of circ_0008812 and circ_0001583 predicts poor prognosis and promotes breast cancer proliferation.

Background: Accumulating evidence suggests that circular RNAs (circRNAs) are highly correlated with tumor progression and pathogenesis in breast cancer. Whereas, their regulatory roles and corresponding mechanisms in breast cancer are still not exhaustive. Thus, we intended to establish circRNA-mediated competive endogenous RNA (ceRNA) network to uncover the possible roles and clinical implications of circRNAs in breast cancer. Methods: Microarray and RNA-sequencing (RNA-seq) data were download from GEO and TCGA database to screen for differentially expressed RNAs (DEcircRNAs, DEmiRNAs, DEmRNAs) in breast cancer. By implementing online databases, we established ceRNA networks, performed gene set enrichment analysis, constructed protein-protein interaction (PPI) networks, and assessed the expression levels and prognostic significance of hub genes. Subsequently, we explored the functions of prognosis-related genes and constructed gene-drug interaction networks. Finally, the functional roles of DEcircRNAs in breast cancer were revealed via MTT and colony formation assay. Results: Based on the identified 8 DEcircRNAs, 25 miRNAs and 216 mRNAs, a ceRNA regulatory network was established. Further analysis revealed that prominent enrichments were transcription factor binding, transforming growth factor-beta (TGF-β) and Apelin signaling pathway etc. PPI network and survival curves analysis showed that elevated levels of hub genes (RACGAP1 and KPNA2) were associated with poorer prognosis. They were found to be positively relevant to cell cycle and proliferation. Then a prognostic sub-network of ceRNA was constructed, consisting of 2 circRNAs, 4 miRNAs and 2 mRNAs. The gene-drug interaction network showed that numerous drugs could regulate the expression of these two prognosis-related genes. Functional experiments showed that depletion of circ_0008812 and circ_0001583 could significantly inhibit the proliferation of MCF-7 cells. Conclusion: Our study constructed 4 prognostic regulatory axes that are significantly correlated with tumor prognosis in breast cancer patients, and uncover the roles of circ_0008812 and circ_0001583 in breast cancer, providing a new perspective into the molecular mechanisms of breast cancer pathogenesis.

MiR-92a-3p promotes breast cancer proliferation by regulating the KLF2/BIRC5 axis.

Breast cancer remains the most common malignancy in females around the world. Recently, a growing number of studies have focused on gene dysregulation. In our previous study, Krüppel-like factors (KLFs) were found to play essential roles in breast cancer development, among which KLF2 could function as a tumor suppressor. Nevertheless, the underlying molecular mechanism remains unclear. miR-92a-3p was identified as the upstream regulator of KLF2 by starBase v.3.0. The regulation of KLF2 by miR-92a-3p was verified by a series of in vitro and in vivo assays. Further exploration revealed that Baculoviral IAP Repeat Containing 5 (BIRC5)was the target of KLF2. ChIP assay, dual-luciferase reporter analysis, quantitative real-time PCR, and western blot were performed for verification. miR-92a-3p functioned as a tumor promoter by inhibiting KLF2 by binding to its 3'-untranslated region (3'-UTR). In addition, KLF2 could transcriptionally suppress the expression of BIRC5. Collectively, our results uncovered the miR-92a-3p/KLF2/BIRC5 axis in breast cancer and provided a potential mechanism for breast cancer development, which may serve as promising strategies for breast cancer therapy.

ERα-LBD, an isoform of estrogen receptor alpha, promotes breast cancer proliferation and endocrine resistance

Estrogen receptor alpha (ERα) drives mammary gland development and breast cancer (BC) growth through an evolutionarily conserved linkage of DNA binding and hormone activation functions. Therapeutic targeting of the hormone binding pocket is a widely utilized and successful strategy for breast cancer prevention and treatment. However, resistance to this endocrine therapy is frequently encountered and may occur through bypass or reactivation of ER-regulated transcriptional programs. We now identify the induction of an ERα isoform, ERα-LBD, that is encoded by an alternative ESR1 transcript and lacks the activation function and DNA binding domains. Despite lacking the transcriptional activity, ERα-LBD is found to promote breast cancer growth and resistance to the ERα antagonist fulvestrant. ERα-LBD is predominantly localized to the cytoplasm and mitochondria of BC cells and leads to enhanced glycolysis, respiration and stem-like features. Intriguingly, ERα-LBD expression and function does not appear to be restricted to cancers that express full length ERα but also promotes growth of triple-negative breast cancers and ERα-LBD transcript (ESR1-LBD) is also present in BC samples from both ERα(+) and ERα(−) human tumors. These findings point to ERα-LBD as a potential mediator of breast cancer progression and therapy resistance.

Long Non-Coding RNA LINC00052 Targets miR-548p/Notch2/Pyk2 to Modulate Tumor Budding and Metastasis of Human Breast Cancer.

Abnormal expression of long non-coding RNAs (lncRNAs) is involved in many pathological processes of cancers. However, the role of lncRNA LINC00052 in breast cancer progression is still unclear. Here, LINC00052 expression was detected by in situ hybridization and quantitative real-time PCR assays. Cell Counting Kit-8, wound healing, and transwell assays were used to investigate changes in the proliferation, migration, and invasion of breast cancer cells. MiR-548p was found associated with LINC00052 or Notch2 by RNA pull-down, dual-luciferase reporter, and qRT-PCR assays. The effect of LINC00052 on lung metastasis was explored through in vivo experiments. High LINC00052 expression was observed in breast cancer tissues and cells. LINC00052 silencing inhibited the proliferation, migration, and invasion of MCF7 cells, and LINC00052 overexpression produced the opposite results. MiR-548p, a target gene of LINC00052, partially rescued the effects of LINC00052 on proliferation, migration, and invasion of MCF7. Notch2 was the target of miR-548p and LINC00052 could promote Notch2 expression. Moreover, the phosphorylation of proline-rich tyrosine kinase 2 (Pyk2), a downstream factor of Notch2, was increased by LINC00052, and a Pyk2 mutant could inhibit the cell migration and invasion induced by LINC00052 overexpression in MDA-MB-468 cells, which was similar to the function of the miR-548p mimic. We further demonstrated that LINC00052 exacerbated the metastases of breast cancer cells in vivo. Our research demonstrated that LINC00052 is highly expressed in breast cancer and promotes breast cancer proliferation, migration, and invasion via the miR-548p/Notch2/Pyk2 axis. LINC00052 could serve as a potential therapeutic target for breast cancer.