Breast Cancer Cell Cycle Progression Research Articles

Role of β3 subunit of the GABA type A receptor in triple negative breast cancer proliferation, migration, and cell cycle progression

ABSTRACT Triple negative breast cancer (TNBC) is known for its heterogeneous nature and aggressive onset. The unresponsiveness to hormone therapies and immunotherapy and the toxicity of chemotherapeutics account for the limited treatment options for TNBC. Ion channels have emerged as possible therapeutic candidates for cancer therapy, but little is known about how ligand gated ion channels, specifically, GABA type A ligand-gated ion channel receptors (GABAAR), affect cancer pathogenesis. Our results show that the GABAA β3 subunit is expressed at higher levels in TNBC cell lines than non-tumorigenic cells, therefore contributing to the idea that limiting the GABAAR via knockdown of the GABAA β3 subunit is a potential strategy for decreasing the proliferation and migration of TNBC cells. We employed pharmacological and genetic approaches to investigate the role of the GABAA β3 subunit in TNBC proliferation, migration, and cell cycle progression. The results suggest that pharmacological antagonism or genetic knockdown of GABAA β3 subunit decreases TNBC proliferation and migration. In addition, GABAA β3 subunit knockdown causes cell cycle arrest in TNBC cell lines via decreased cyclin D1 and increased p21 expression. Our findings suggest that membrane bound GABAA receptors containing the β3 subunit can be further developed as a potential novel target for the treatment of TNBC.

NNMT/1-MNA Promote Cell-Cycle Progression of Breast Cancer by Targeting UBC12/Cullin-1-Mediated Degradation of P27 Proteins.

Cell cycle dysregulation is a defining feature of breast cancer. Here, 1-methyl-nicotinamide (1-MNA), metabolite of nicotinamide N-methyltransferase(NNMT) is identified, as a novel driver of cell-cycle progression in breast cancer. NNMT, highly expressed in breast cancer tissues, positively correlates with tumor grade, TNM stage, Ki-67 index, and tumor size. Ablation of NNMT expression dramatically suppresses cell proliferation and causes cell-cycle arrest in G0/G1 phase. This phenomenon predominantly stems from the targeted action of 1-MNA, resulting in a specific down-regulation of p27 protein expression. Mechanistically, 1-MNA expedites the degradation of p27 proteins by enhancing cullin-1 neddylation, crucial for the activation of Cullin-1-RING E3 ubiquitin ligase(CRL1)-an E3 ubiquitin ligase targeting p27 proteins. NNMT/1-MNA specifically up-regulates the expression of UBC12, an E2 NEDD8-conjugating enzyme required for cullin-1 neddylation. 1-MNA showes high binding affinity to UBC12, extending the half-life of UBC12 proteins via preventing their localization to lysosome for degradation. Therefore, 1-MNAis a bioactive metabolite that promotes breast cancer progression by reinforcing neddylation pathway-mediated p27 degradation. The study unveils the link between NNMT enzymatic activity with cell-cycle progression, indicating that 1-MNA may be involved in the remodeling of tumor microenvironment.

CircANKRD17 promotes glycolysis by inhibiting miR-143 in breast cancer cells.

Glucose metabolic reprogramming, known as the Warburg effect, is one of the metabolic hallmarks of tumor cells. Cancer cells preferentially metabolize glucose by glycolysis rather than mitochondrial oxidative phosphorylation regardless of oxygen availability, but the regulatory mechanism underlying this switch has been incompletely understood. Here, we report that the circular RNA circ ankyrin repeat domain 17 (ANKRD17)functions as a key regulator for glycolysis to promote cell growth, migration, invasion, and cell-cycle progression in breast cancer (BC) cells. We further show that circANKRD17 acts to accelerate glycolysis in BC cells by acting as a sponge for miR-143 and in turn overrides the repressive effect of miR-143, a well-documented glycolytic repressor, on hexokinase 2in BC cells, thus resulting in enhanced glycolysis in BC cells. These data suggest the circANKRD17-miR-143 cascade as a novel mechanism in controlling glucose metabolic reprogramming in BC cells and suggest circANKRD17 as a promising therapeutic target to interrupt cancerous glycolysis.

Evaluation of anti-cancer effects of carnosine and melittin-loaded niosomes in MCF-7 and MDA-MB-231 breast cancer cells.

Background: We investigated the anti-cancer effect of carnosine-loaded niosomes (Car-NIO) and melittin-loaded niosomes (Mel-NIO) with olaparib in breast cancer cell lines (MCF-7 and MDA-MB-231). Methods: The thin film method was used for preparing the niosomes and characterized in terms of morphology, size, and polydispersity index (PDI). We further evaluated the impact of these peptides on breast cancer cells viability, RT-qPCR assays, malondialdehyde (MDA) activity, and cell cycle progression, to determine if these are linked to carnosine and melittin's anti-proliferative properties. Results: Car-NIO and Mel-NIO in vitro study inhibited cancer cell viability. They have also upregulated the expression of protein 53 (P53), BCL2-Associated X Protein (Bax), caspase-9, caspase-3, programmed cell death 4 (PDCD4), and Forkhead box O3 (FOXO3), while downregulated the expression of B-cell lymphoma 2 (Bcl2), poly (ADP-ribose) polymerase (PARP 1), and MicroRNA-183 (miRNA-183). The MCF-7 cells were arrested at the G2/M phase in Car-NIO, on the other hand, the MDA-MB-231 cells were arrested at the S phase. While the Mel-NIO and olaparib arrested the MCF-7 and MDA-MB-231 cells at the G0/1 phase. Conclusion: Our study successfully declared that Mel-NIO had more anti-cancer effects than Car-NIO in both MCF-7 and MDA-MB-231 breast cancer cells.

Abstract 3983: Defining the role of FANCA in breast cancer development and cell cycle progression

Abstract FANCA is one of the 22 known Fanconi anemia (FA) pathway genes and is indispensable for interstrand crosslink (ICL) repair. It is reported that FANCA is responsible for about 64% of FA cases and one important clinical characterization of FA patients is predisposition to cancer. However, analysis of TCGA database reveals that FANCA level is elevated in breast cancer patients, especially in ER- breast cancer, which is associated with the methylation status at the S-shore of CpG island ahead of FANCA gene. Moreover, the FANCA level is negatively correlated with the survival rate of breast cancer patients. To understand the implication of FANCA in breast cancer development, we have targeted FANCA by either CRISPR mediated knock-out (KO) or shRNA mediated knockdown (KD) in MDA-MB-231 breast cancer cells. Our data suggest that depletion of FANCA protein inhibits breast cancer growth both in vitro and in vivo. On the other hand, overexpressing FANCA in low-FANCA breast cancer cell line MDA-MB-468 promotes cancer cell proliferation. Cell cycle profiling reveals an inefficiency of MDA-MB-231 FANCA KO cells in G1 to S transition due to p21 and p27 upregulation in FANCA KO cells. In addition, the proliferation inefficiency in MDA-MB-231 FANCA KO cells is caused by Rb hypophosphorylation. Therefore, we conclude that FANCA contributes to the breast cancer development by promoting cell cycle progression through Rb/E2F signaling pathway. Our immunoprecipitation (IP) results indicate that in MDA-MB-231, FANCA is interacting with HES1, which is a transcription suppressor that binds to the promoter region of CDKN1A and CDKN1B to promote cell cycle progression, explaining how FANCA participates in cell cycle progression in breast cancer. Citation Format: Liang Luo, Wenjun Liu, Anna Palovcak, Fenghua Yuan, Fang Li, Daniel Calkins, Yan Li, Karoline Briegel, Daniel Bilbao, Evan Roberts, Christian Mason, Zhao-Jun Liu, Sylvia Daunert, Yanbin Zhang. Defining the role of FANCA in breast cancer development and cell cycle 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 3983.

YTHDF2 Regulates Cell Growth and Cycle by Facilitating KDM1A mRNA Stability

Breast cancer is the leading cause of cancer death in women. The physiological functions of N6-methyladenosine methylation in cancer have been the focus of studies in recent years. Herein, four data sets (GSE70947, GSE45827, GSE42586, and The Cancer Genome Atlas Breast Cancer) were analyzed to confirm the differentially expressed N6-methyladenosine genes. YTH N6-methyladenosine RNA-binding protein 2 (YTHDF2) was found to be highly expressed in breast cancer tissues and cells. Invitro, YTHDF2 affects cell proliferation, cell cycle, and invasive ability. Tumorigenesis in xenograft nude mice confirmed that YTHDF2 interference reduced the tumor formation ability of cancer cells. Pearson correlation analysis demonstrated a positive correlation between YTHDF2 and lysine-specific histone demethylase 1A (KDM1A) expression. An online tool, Sequence-based RNA Adenosine Methylation Site Predictor (SRAMP), predicted eight methylation sites in the KDM1A mRNA sequence. The expression of KDM1A was dramatically increased in breast cancer tissues and cells. Down-regulation of YTHDF2 reduced KDM1A expression and the methylation level of KDM1A mRNA. YTHDF2 interference promoted the degradation of KDM1A mRNA, which suggested an interaction between YTHDF2 and KDM1A. KDM1A interference altered cell proliferation, cell cycle, and invasive ability, whereas YTHDF2 overexpression rescued KDM1A interference-induced cell phenotypic changes. In conclusion, YTHDF2 promotes breast cancer cell growth and cell cycle progression by facilitating KDM1A mRNA stability. This study provides new therapeutic targets for breast cancer treatment in the future.

DCXR promotes cell proliferation by promoting the activity of aerobic glycolysis in breast cancer.

The function of human dicarbonyl/L‑xylulose reductase (DCXR) in the pathophysiology of breast cancer is yet to be elucidated. The present study aimed to investigate the function of DCXR in glycolysis and the cell cycle of breast cancer cells with respect to cell proliferation. Differential expressed DCXR was identified in The Cancer Genome Atlas (TCGA) database and verified in clinical breast cancer tissue. DCXR silencing and overexpression were induced by RNA interference and lentiviral vectors, respectively. Cell cycle progression, proliferation and glycolytic activity of breast cancer cells were detected by flow cytometry, Cell Counting Kit‑8 assay and chemical methods, respectively. Tumorigenicity was detected using nude mice xenograft models. The expression of DCXR was increased in TCGA breast cancer database and the function of DCXR was enriched in 'glycolysis' and 'cell cycle'. Further analysis using clinical breast cancer samples confirmed upregulation of DCXR. The silencing of DCXR suppressed proliferation and cell cycle progression of breast cancer cells and significantly decreased the capacity for glycolysis, thereby demonstrating the effect of DCXR on the function of breast cancer cells. Similar conclusions were obtained in DCXR overexpressing cells; notably, DCXR overexpression promoted proliferation, cell cycle progression at S phase and glycolysis. 2‑Deoxy‑D‑glucose inhibited the effect of DCXR on the proliferation and cell cycle progression of breast cancer cells. The present study revealed that DCXR regulated breast cancer cell cycle progression and proliferation by increasing glycolysis activity and thus may serve as an oncogene for breast cancer.

BPTF promotes the progression of distinct subtypes of breast cancer and is a therapeutic target.

To assess the biomarker and functional role of the chromatin remodeling factor, bromodomain PHD finger transcription factor (BPTF), in breast cancer progression. BPTF copy number was assessed using fluorescence in situ hybridization. BPTF expression was regulated in breast cancer cells by shRNA/siRNA-mediated gene silencing and BPTF cDNA overexpression. The effects of regulating BPTF expression were examined on key oncogenic signaling pathways and on breast cancer cell proliferation, apoptosis, and cell cycle progression, as well as in xenograft models. The consequences of pharmacological bromodomain inhibition, alone or in combination with other targeted agents, on breast cancer progression were assessed in culture and in xenograft models. BPTF copy number was gained in 34.1% and separately amplified in 8.2% of a breast cancer tissue cohort. Elevated BPTF copy number was significantly associated with increasing patient age and tumor grade and observed in both ER-positive and triple-negative breast cancer (TNBC) subtypes. BPTF copy number gain and amplification were also observed in The Cancer Genome Atlas (TCGA) breast cancer cohort. Stable shRNA-mediated silencing of BPTF significantly inhibited cell proliferation and induced apoptosis in TNBC and ER-positive human breast cancer cell lines. BPTF knockdown suppressed signaling through the phosphoinositide 3 kinase (PI3K) pathway, including reduced expression of phosphorylated AKT (Ser473), phosphorylated GSK-β (Ser9), and CCND1. These findings were confirmed following transient BPTF knockdown by a distinct siRNA in TNBC and ER-positive breast cancer cells. Stable suppression of BPTF expression significantly inhibited the in vivo growth of TNBC cells. Conversely, BPTF cDNA overexpression in TNBC and ER-positive breast cancer cells enhanced breast cancer cell proliferation and reduced apoptosis. BPTF targeting with the bromodomain inhibitor bromosporine, alone or in combination with the PI3K pathway inhibitor gedatolisib, produced significant anti-tumor effects against TNBC cells in vitro and in vivo. These studies demonstrate BPTF activation in distinct breast cancer subtypes, identify pathways by which BPTF promotes breast cancer progression, and suggest BPTF as a rational target for breast cancer therapy.

The Synergistic Effects of SHR6390 Combined With Pyrotinib on HER2+/HR+ Breast Cancer.

HER2+/HR+ breast cancer is a special molecular type of breast cancer. Existing treatment methods are prone to resistance; “precision treatment” is necessary. Pyrotinib is a pan-her kinase inhibitor that can be used in HER2-positive tumors, while SHR6390 is a CDK4/6 inhibitor that can inhibit ER+ breast cancer cell cycle progression and cancer cell proliferation. In cancer cells, HER2 and CDK4/6 signaling pathways could be nonredundant; co-inhibition of both pathways by combination of SHR6390 and pyrotinib may have synergistic anticancer activity on HER2+/HR+ breast cancer. In this study, we determined the synergy of the two-drug combination and underlying molecular mechanisms. We showed that the combination of SHR6390 and pyrotinib synergistically inhibited the proliferation, migration, and invasion of HER2+/HR+ breast cancer cells in vitro. The combination of two drugs induced G1/S phase arrest and apoptosis in HER2+/HR+ breast cancer cell lines. The combination of two drugs prolonged the time to tumor recurrence in the xenograft model system. By second-generation RNA sequencing technology and enrichment analysis of the pyrotinib-resistant cell line, we found that FOXM1 was associated with induced resistance to HER2-targeted therapy. In HER2+/HR+ breast cancer cell lines, the combination of the two drugs could further reduce FOXM1 phosphorylation, thereby enhancing the antitumor effect to a certain extent. These findings suggest that SHR6390 combination with pyrotinib suppresses the proliferation, migration, and invasion of HER2+/HR+ breast cancers through regulation of FOXM1.

Abstract P5-05-05: Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds

Abstract The transcription factor FOXM1 is up-regulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome-dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1. (Supported by Breast Cancer Research Foundation grant (BCRF-083 to BSK), The Julius and Mary Landfield Cancer Research Fund (to BSK), NIH grant R01 DK015556 (to JAK), NIH T32 GM070421 Fellowship (to VSG), Bankhead-Coley Foundation grant 09BW04 (to DEA), USDA award ILLU-698-909 and National Center for Supercomputing Applications Faculty Fellowship (to ZME), and UIUC Environmental Toxicology Scholarship (to BPS)). Citation Format: Benita S. Katzenellenbogen, Yvonne Ziegler, Mary J Laws, Valeria S. Guillen, SungHoon Kim, Parama Dey, Brandi P. Smith, Ping Gong, Noah Bindman, Yuechao Zhao, Kathryn Carlson, Mayuri A. Yasuda, Divya Singh, Zhong Li, Dorraya El-Ashry, Zeynep Madak-Erdogan, John A. Katzenellenbogen. Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-05-05.

Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds

The transcription factor FOXM1 is upregulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome- dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1.

NEAT1/miR‑124/STAT3 feedback loop promotes breast cancer progression.

The long non‑coding RNA nuclear enriched abundant transcript1 (NEAT1) has important roles in the regulation of multiple cell functions, such as proliferation, apoptosis and migration. However, the mechanism by which NEAT1 regulates breast cancer progression is not well elucidated. In the present study, NEAT1 and microRNA‑124 (miR‑124) levels were detected by reverse transcription‑quantitative PCR in breast cancer tissues and cell lines. STAT3 protein levels were detected by western blot analysis. Cell proliferation and cell cycle distribution were determined using MTT and colony formation assays, and flow cytometry, respectively. The results demonstrated that NEAT1 and STAT3 expression levels were increased in breast cancer tissues compared with normal breast tissues, whereas miR‑124 expression was significantly decreased. Functional analyses revealed that NEAT1 promoted cell proliferation and cell cycle progression in breast cancer cells. Additionally, NEAT1 and STAT3 expression levels were negatively correlated with miR‑124 levels in breast cancer tissues. A direct interaction between miR‑124, and NEAT1 and STAT3, was predicted by bioinformatics analysis and confirmed using a luciferase activity assay. NEAT1 overexpression markedly increased STAT3 protein expression levels, and this effect was reversed by miR‑124 overexpression in breast cancer cells. Furthermore, miR‑124 overexpression partially attenuated the effects of NEAT1 on breast cancer cell proliferation and cell cycle progression. The inhibitory effects of miR‑124 overexpression on the proliferation rate and cell cycle progression were abolished by STAT3 overexpression. In turn, STAT3 silencing inhibited NEAT1 transcription in breast cancer cells. In summary, the present findings revealed that NEAT1 and STAT3 formed a feedback loop via sponging miR‑124 to promote breast cancer progression.

The novel long non‑coding RNA PRNCR1‑2 is involved in breast cancer cell proliferation, migration, invasion and cell cycle progression.

Long non‑coding RNAs (lncRNAs) have recently been reported to act as important mediators of tumor initiation and progression. The present study aimed to investigate the expression and pathogenic roles of the lncRNA prostate cancer‑associated non‑coding RNA (PRNCR)1‑2 in breast cancer. The expression levels of PRNCR1‑2 were detected in breast cancer tissues and numerous breast cancer cell lines using reverse transcription‑quantitative polymerase chain reaction. Depletion of PRNCR1‑2 expression in breast cancer cells was conducted through small interfering RNA‑mediated silencing. Subsequently, cell proliferation was assessed by MTS assay, cell migration and invasion capacities were evaluated using the Transwell culture system, and cell cycle progression and apoptosis were analyzed by flow cytometry. Protein expression levels of the signaling components checkpoint kinase2 (CHK2), protein kinaseB (AKT), phosphorylated (p)‑CHK2 and p‑AKT were measured by western blotting. The results demonstrated that PRNCR1‑2 expression was significantly elevated in breast cancer tissues compared with in adjacent normal tissues. Furthermore, depletion of PRNCR1‑2 in HS‑578T and MDA‑MB‑231 breast cancer cells markedly suppressed their proliferation rates, migration and invasion capacities, and cell cycle progression; however, it had no effect on cell apoptosis. In addition, PRNCR1‑2 depletion increased CHK2 phosphorylation and decreased AKT phosphorylation in HS‑578T and MDA‑MB‑231 cells. In conclusion, the lncRNA PRNCR1‑2 may promote breast cancer cell proliferation, migration, invasion and cell cycle progression.

DDX3X RNA helicase affects breast cancer cell cycle progression by regulating expression of KLF4.

DDX3X is a multifunctional RNA helicase with documented roles in different cancer types. Here, we demonstrate that DDX3X plays an oncogenic role in breast cancer cells by modulating the cell cycle. Depletion of DDX3X in MCF7 cells slows cell proliferation by inducing a G1 phase arrest. Notably, DDX3X inhibits expression of Kruppel‐like factor 4 (KLF4), a transcription factor and cell cycle repressor. Moreover, DDX3X directly interacts with KLF4 mRNA and regulates its splicing. We show that DDX3X‐mediated repression of KLF4 promotes expression of S‐phase inducing genes in MCF7 breast cancer cells. These findings provide evidence for a novel function of DDX3X in regulating expression and downstream functions of KLF4, a master negative regulator of the cell cycle.

KIAA0101 inhibition suppresses cell proliferation and cell cycle progression by promoting the interaction between p53 and Sp1 in breast cancer

KIAA0101 functions as a regulator of centrosome number in breast cancer. Here, we identify the role of KIAA0101 in breast cancer cell proliferation and cell cycle progression. KIAA0101 knockdown significantly inhibited cell growth, colony formation and G1/S phase transition. Further investigation indicated that KIAA0101 silencing suppressed the expression of CCNE2, CDK6 and CDKN1A. Luciferase reporter assay and ChIP assay demonstrated that Sp1 positively regulated the transcription of CCNE2, CDK6 and CDKN1A. KIAA0101 knockdown promoted the interaction between p53 and Sp1, inhibiting the transcriptional activation of Sp1 on CCNE2, CDK6 and CDKN1A. Knockdown of p53 counteracted the inhibitory effect of KIAA0101 knockdown on breast cancer cells proliferation and cell cycle progression while Sp1 knockdown mimicked the effect of KIAA0101 knockdown. These results suggested that KIAA0101 knockdown suppressed the cell proliferation and cell cycle progression by promoting the formation of p53/Sp1 complex in breast cancer.

Ras GTPase-Activating-Like Protein IQGAP1 (IQGAP1) Promotes Breast Cancer Proliferation and Invasion and Correlates with Poor Clinical Outcomes.

BackgroundBreast cancer is one of the most common female cancers in the world. As a key integrator of cell signaling pathways, IQGAP1 contributes to the development and progression of several cancers. However, the exact effects and molecular mechanisms of IQGAP1 in breast cancer progression remain poorly understood.Material/MethodsIn the present study, IQGAP1 expression was measured in 96 paired breast cancer samples and the corresponding adjacent non-cancerous tissues by immunohistochemistry and quantitative polymerase chain reaction. To further explore the biological function of IQGAP1 in breast cancer cells, we knocked down IQGAP1 expression in MCF-7 cells and overexpressed it in SK-BR-3 cells.ResultsIQGAP1 was specifically upregulated in breast cancer tissues compared with the corresponding adjacent non-cancerous tissues. Moreover, IQGAP1 expression was positively correlated with breast cancer survival rate. IQGAP1 also promoted breast cancer cell proliferation and cell cycle progression and suppressed apoptosis.ConclusionsIn conclusion, our results suggest that IQGAP1 plays an important role in the cell proliferation and invasion of human breast cancer cells, thus indicating that IQGAP1 may be a potential therapeutic target for the treatment of human breast cancer.

PSMD2 regulates breast cancer cell proliferation and cell cycle progression by modulating p21 and p27 proteasomal degradation

Alterations in the ubiquitin-proteasome system (UPS) and UPS-associated proteins have been implicated in the development of many human malignancies. In this study, we investigated the expression profiles of 797 UPS-related genes using HiSeq data from The Cancer Genome Atlas and identified that PSMD2 was markedly upregulated in breast cancer. High PSMD2 expression was significantly correlated with poor prognosis. Gene set enrichment analysis revealed that transcriptome signatures involving proliferation, cell cycle, and apoptosis were critically enriched in specimens with elevated PSMD2. Consistently, PSMD2 knockdown inhibited cell proliferation and arrested cell cycle at G0/G1 phase in vitro, as well as suppressed tumor growth in vivo. Rescue assays demonstrated that the cell cycle arrest caused by silencing PSMD2 partially resulted from increased p21 and/or p27. Mechanically, PSMD2 physically interacted with p21 and p27 and mediated their ubiquitin-proteasome degradation with the cooperation of USP14. Notably, intratumor injection of therapeutic PSMD2 small interfering RNA effectively delayed xenograft tumor growth accompanied by p21 and p27 upregulation. These data provide novel insight into the role of PSMD2 in breast cancer and suggest that PSMD2 may be a potential therapeutic target.

Withaferin A and sulforaphane regulate breast cancer cell cycle progression through epigenetic mechanisms

Little is known about the effects of combinatorial dietary compounds on the regulation of epigenetic mechanisms involved in breast cancer prevention. The human diet consists of a multitude of components, and there is a need to elucidate how certain compounds interact in collaboration. Withaferin A (WA), found in the Indian winter cherry and documented as a DNA methyltransferase (DNMT) inhibitor, and sulforaphane (SFN), a well-known histone deacetylase (HDAC) inhibitor found in cruciferous vegetables, are two epigenetic modifying compounds that have only recently been studied in conjunction. The use of DNMT and HDAC inhibitors to reverse the malignant expression of certain genes in breast cancer has shown considerable promise. Previously, we found that SFN + WA synergistically promote breast cancer cell death. Herein, we determined that these compounds inhibit cell cycle progression from S to G2 phase in MDA-MB-231 and MCF-7 breast cancer. Furthermore, we demonstrate that this unique combination of epigenetic modifying compounds down-regulates the levels of Cyclin D1 and CDK4, and pRB; conversely, the levels of E2F mRNA and tumor suppressor p21 are increased independently of p53. We find these events coincide with an increase in unrestricted histone methylation. We propose SFN + WA-induced breast cancer cell death is attributed, in part, to epigenetic modifications that result in the modulated expression of key genes responsible for the regulation of cancer cell senescence.

Paip1 affects breast cancer cell growth and represents a novel prognostic biomarker

Polyadenylate-binding protein-interacting protein 1 (Paip1) regulates translational initiation. Increasing evidence suggests that Paip1 plays important roles in cancer development and progression. This study explored the role of Paip1 in breast cancer progression and evaluated its prognostic value. The cellular location of Paip1 protein was determined using immunofluorescence. Then, Paip1 protein expression was evaluated by immunohistochemical staining in 119 breast cancers and 40 normal breast tissues. The correlation between Paip1 expression and the clinicopathologic features of breast cancer was evaluated using the χ2 test, and differences in survival curves were analyzed using log-rank tests. The role of Paip1 in breast cancer proliferation and cell cycle progression was identified by siRNA transfection. Paip1 was expressed mainly in the cytoplasm of cancer cells and tissues. Expression was observed in 60.5% of the breast cancers (72/119), which was significantly higher than in normal breast tissues (17.5%; 7/40). High expression of Paip1 protein was associated with high histologic grade, late clinical stage, and a low survival rate. Multivariate analysis indicated that Paip1 was an independent prognostic factor. Additionally, Paip1 depletion by RNAi significantly decreased cell proliferation and induced cell cycle arrest. In conclusion, our study demonstrated that Paip1 promotes the growth of breast cancers and could be a prognostic biomarker and therapeutic target.

UBAP2L silencing inhibits cell proliferation and G2/M phase transition in breast cancer

BackgroundUbiquitin-associated protein 2-like (UBAP2L) contains a ubiquitin-associated domain near its N-terminus, which has been demonstrated to be overexpressed in multiple tumors, including hepatocellular carcinoma and colorectal carcinoma but its role has not been well studied in breast cancer. Thus, this study was designed to evaluate whether UBAP2L can serve as a potential molecular target for breast cancer therapy.MethodsThe expression of UBAP2L was determined in breast cancer tissues and cell lines by Western blotting and Oncomine database mining. Then the expression of UBAP2L was silenced using RNA interference and the effects of UBAP2L knockdown on breast cancer cell proliferation and cell cycle progression by MTT and colony formation assay, and Flow cytometry, respectively.ResultsWe found the expression of UBAP2L was significantly up-regulated in breast cancer tissues and cell lines. Knockdown of UBAP2L suppressed cell proliferation, impaired colony formation ability and induced cell cycle arrest at G2/M phase. At molecular levels, knockdown of UBAP2L increased p21 expression, but decreased the expression of CDK1 and Cyclin B1 in breast cancer cells.ConclusionOur findings suggest that UBAP2L plays an important role in breast cancer cell proliferation and might serve as a potential target for breast cancer treatment.