Triple-negative Breast Cancer Tumorigenesis Research Articles

Exploring the regulatory role of FBXL19-AS1 in triple-negative breast cancer through the miR-378a-3p/OTUB2 axis.

The regulatory potential of long noncoding RNA (lncRNA) FBXL19-AS1 has been highlighted in various cancers, but its effect on triple-negative breast cancer (TNBC) remains unclear. Here, we aimed to elucidate the role of FBXL19-AS1 in TNBC and its underlying mechanism. RT-qPCR was employed to detect the expressions of FBXL19-AS1 and miR-378a-3p in tissues and cells. Immunohistochemical staining and western blot were utilized to detect the expression levels of proteins. Cell activities were detected using flow cytometry, CCK-8, and transwell assay. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were deployed to investigate interactions of different molecules. Protein-protein interaction (PPI) network, gene ontology (GO), and Kyoto encyclopedia of genes and genomes (KEGG) pathways were used to analyze the downstream pathway. In vivo xenograft model was conducted to detect the effect of FBXL19-AS1 on tumor growth. FBXL19-AS1 was overexpressed in TNBC tissues and cell lines compared with counterparts. FBXL19-AS1 knockdown suppressed TNBC cell activities, whereas its overexpression exhibited the opposite effect. Mechanistically, FBXL19-AS1 was found to interact with miR-378a-3p. Further analysis revealed that miR-378a-3p exerted tumor-suppressive effects in TNBC cells. Additionally, miR-378a-3p targeted and downregulated the expression of ubiquitin aldehyde binding 2 (OTUB2), a deubiquitinase associated with TNBC progression. In vivo experiments substantiated the inhibitory effects of FBXL19-AS1 knockdown on TNBC tumorigenesis, and a miR-378a-3p inhibitor partially rescued these effects. The downstream pathway of the miR-378a-3p/OTUB2 axis was explored, revealing connections with proteins involved in modifying other proteins, removing ubiquitin molecules, and influencing signaling pathways, including the Hippo signaling pathway. Western blot analysis confirmed changes in YAP and TAZ expression levels, indicating a potential regulatory network. In summary, FBXL19-AS1 promotes exacerbation in TNBC by suppressing miR-378a-3p, leading to increased OTUB2 expression. The downstream mechanism may be related to the Hippo signaling pathway. These findings propose potential therapeutic targets for TNBC treatment.

CK2α-mediated phosphorylation of GRP94 facilitates the metastatic cascade in triple-negative breast cancer

Distant metastasis is a significant hallmark affecting to the high death rate of patients with triple-negative breast cancer (TNBC). Thus, it is crucial to identify and develop new therapeutic strategies to hinder cancer metastasis. While emerging studies have hinted a pivotal role of glucose-regulated protein 94 (GRP94) in tumorigenesis, the exact biological functions and molecular mechanisms of GRP94 in modulating cancer metastasis remain to be elucidated. Our study demonstrated an increased expression of GRP94 in TNBC correlated with metastatic progression and unfavorable prognosis in patients. Functionally, we identified that GRP94 depletion significantly diminished TNBC tumorigenesis and subsequent lung metastasis. In contrast, GRP94 overexpression exacerbated the invasiveness, migration, and lung metastasis of non-TNBC cells. Mechanistically, we found that casein kinase 2 alpha (CK2α) active in advanced breast cancer phosphorylated GRP94 at a conserved serine 306 (S306) residue. This phosphorylation increased the stability of GRP94 and enhanced its interaction with LRP6, leading to activation of canonical Wnt signaling. From a therapeutic standpoint, we found that benzamidine, a novel CK2α inhibitor, effectively suppressed GRP94 phosphorylation, LRP6 stabilization, and metastasis of TNBC. Our results point to the critical role of CK2α-mediated GRP94 phosphorylation in TNBC metastasis through activation of Wnt signaling, highlighting GRP94 as a therapeutic target to impede TNBC metastasis.

YAP1-induced RBM24 promotes the tumorigenesis of triple-negative breast cancer through the β-catenin pathway.

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype and refractory to current treatments. RBM24 is an RNA-binding protein and shows the ability to regulate tumor progression in multiple cancer types. However, its role in TNBC is still unclear. In this study, we analyzed publicly available profiling data from TNBC tissues and cells. Loss- and gain-of-function experiments were performed to determine the function of RBM24 in TNBC cells. The mechanism for RBM24 action in TNBC was investigated. RBM24 was deregulated in TNBC tissues and TNBC cells with depletion of SIPA1, YAP1, or ARID1A, three key regulators of TNBC. Compared to MCF10A breast epithelial cells, TNBC cells had higher levels of RBM24. Knockdown of RBM24 inhibited TNBC cell proliferation, colony formation, and tumorigenesis, while overexpression of RBM24 promoted aggressive phenotype in TNBC cells. YAP1 overexpression induced the expression of RBM24 and the RBM24 promoter-driven luciferase reporter. YAP1 was enriched at the promoter region of RBM24. Overexpression of RBM24 increased β-catenin-dependent transcriptional activity. Most importantly, knockdown of CTNNB1 rescued RBM24 aggressive phenotype in TNBC cells. Collectively, the YAP1/RBM24/β-catenin axis plays a critical role in driving TNBC progression. RBM24 may represent a novel therapeutic target for TNBC treatment.

Unveiling Epigenetic Vulnerabilities in Triple-Negative Breast Cancer through 3D Organoid Drug Screening.

Triple-negative breast cancer (TNBC) poses a therapeutic challenge due to its aggressive nature and lack of targeted therapies. Epigenetic modifications contribute to TNBC tumorigenesis and drug resistance, offering potential therapeutic targets. Recent advancements in three-dimensional (3D) organoid cultures, enabling precise drug screening, hold immense promise for identifying novel compounds targeting TNBC. In this study, we established two patient-derived TNBC organoids and implemented a high-throughput drug screening system using these organoids and two TNBC cell lines. Screening a library of 169 epigenetic compounds, we found that organoid-based systems offer remarkable precision in drug response assessment compared to cell-based models. The top 30 compounds showing the highest drug sensitivity in the initial screening were further assessed in a secondary screen. Four compounds, panobinostat, pacritinib, TAK-901, and JIB-04, targeting histone deacetylase, JAK/STAT, histone demethylases, and aurora kinase pathways, respectively, exhibited potent anti-tumor activity in TNBC organoids, surpassing the effect of paclitaxel. Our study highlights the potential of these novel epigenetic drugs as effective therapeutic agents for TNBC and demonstrates the valuable role of patient-derived organoids in advancing drug discovery.

METTL14/miR-29c-3p axis drives aerobic glycolysis to promote triple-negative breast cancer progression though TRIM9-mediated PKM2 ubiquitination.

The energy metabolic rearrangement of triple-negative breast cancer (TNBC) from oxidative phosphorylation to aerobic glycolysis is a significant biological feature and can promote the malignant progression. However, there is little knowledge about the functional mechanisms of methyltransferase-like protein 14 (METTL14) mediated contributes to TNBC malignant progression. Our study found that METTL14 expression was significantly upregulated in TNBC tissues and cell lines. Silencing METTL14 significantly inhibited TNBC cell growth and invasion invitro, as well as suppressed tumour growth. Mechanically, METTL14 was first found to activate miR-29c-3p through m6A and regulate tripartite motif containing 9 (TRIM9) to promote ubiquitination of pyruvate kinase isoform M2 (PKM2) and lead to its transition from tetramer to dimer, resulting in glucose metabolic reprogramming from oxidative phosphorylation to aerobic glycolysis to promote the progress of TNBC. Taken together, these findings reveal important roles of METTL14 in TNBC tumorigenesis and energy metabolism, which might represent a novel potential therapeutic target for TNBC.

Spatholobus suberectus inhibits lipogenesis and tumorigenesis in triple-negative breast cancer via activation of AMPK-ACC and K-Ras-ERK signaling pathway.

Triple-negative breast cancer (TNBC) is a highly invasive type of breast cancer with a poor prognosis. Currently, there are no effective management strategies for TNBC. Earlier, our lab reported the percolation of Spatholobus suberectus for the treatment of breast cancer. Lipid metabolic reprogramming is a hallmark of cancer. However, the anti-TNBC efficiency of S.suberectus extract and its causal mechanism for preventing lipogenesis have not been fully recognized. Hence, the present study aimed to investigate the inhibitory role of S.suberectus extract on lipogenesis and tumorigenesis in TNBC invitro and invivo by activating AMPK-ACC and K-Ras-ERK signaling pathways using lipidomic and metabolomic techniques. Dried stems of S.suberectus extract inhibited lipogenesis and tumorigenesis and promoted fatty acid oxidation as demonstrated by the identification of the metabolites and fatty acid markers using proteomic and metabolomic analysis, qPCR, and Western blot. The results indicated that S.suberectus extract promotes fatty acid oxidation and suppresses lipogenic metabolites and biomarkers, thereby preventing tumorigenesis via the AMPK-ACC and K-Ras-ERK signaling pathways. On the basis of this preclinical evidence, we suggest that this study represents a milestone and complements Chinese medicine. Further studies remain underway in our laboratory to elucidate the active principles of S.suberectus extract. This study suggests that S.suberectus extract could be a promising therapy for TNBC.

MEF2C and miR-194-5p: New Players in Triple Negative Breast Cancer Tumorigenesis.

Among breast cancer (BC) subtypes, the most aggressive is triple negative BC (TNBC), which is prone to metastasis. We previously found that microRNA (miR)-194-5p is downregulated at the early stages of TNBC brain metastasis development. Additionally, the transcription factor myocyte enhancer factor 2 (MEF2)C, a bioinformatically predicted miR-194-5p target, was increasingly expressed throughout TNBC brain metastasis formation and disease severity. However, the contributions of these two players to malignant cells' features remain undetermined. This study aimed at disclosing the role of miR-194-5p and MEF2C in TNBC tumorigenesis. The transfection of 4T1 cells with a silencer for MEF2C or with a pre-miRNA for miR-194-5p was employed to study TNBC cells' phenotypic alterations regarding epithelial and mesenchymal markers, as well as migratory capability alterations. MEF2C-silenced cells presented a decline in both vimentin and cytokeratin expression, whereas the overexpression of miR-194-5p promoted an increase in cytokeratin and a reduction in vimentin, reflecting the acquisition of an epithelial phenotype. Both treatments reduced TNBC cells' migration. These results suggest that MEF2C may determine TNBC cells' invasive properties by partially determining the occurrence of epithelial-mesenchymal transition, while the overexpression of miR-194-5p promotes a decline in TNBC cells' aggressive behavior and reinforces this miRNA's role as a tumor suppressor in TNBC.

SP1-Induced Upregulation of LncRNA AFAP1-AS1 Promotes Tumor Progression in Triple-Negative Breast Cancer by Regulating mTOR Pathway.

The long non-coding RNA (lncRNA) actin fiber-associated protein-1 antisense RNA 1 (AFAP1-AS1) exerted oncogenic activity in triple-negative breast cancer (TNBC). We designed this study and conducted it to investigate the upstream regulation mechanism of AFAP1-AS1 in TNBC tumorigenesis. In this work, we proved the localization of AFAP1-AS1 in the cytoplasm. We elucidated the mechanism by which the transcription factor specificity protein 1 (SP1) modulated AFAP1-AS1 in TNBC progression, which has yet to be thoroughly studied. Dual luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay revealed a strong affinity of SP1 toward the promoter regions P3 of AFAP1-AS1, proving the gene expression regulation of AFAP1-AS1 via SP1 in TNBC. Additionally, SP1 could facilitate the tumorigenesis of TNBC cells in vitro and in vivo by regulating the AFAP1-AS1 expression. Furthermore, silenced AFAP1-AS1 suppressed the expression of genes in the mTOR pathway, such as eukaryotic translation initiation factor 4B (EIF4B), mitogen-activated protein kinase-associated protein 1 (MAPKAP1), SEH1-like nucleoporin (SEH1L), serum/glucocorticoid regulated kinase 1 (SGK1), and its target NEDD4-like E3 ubiquitin protein ligase (NEDD4L), and promoted the gene expression of s-phase kinase-associated protein 2 (SKP2). Overall, this study emphasized the oncogenic role of SP1 and AFAP1-AS1 in TNBC and illustrated the AFAP1-AS1 upstream interaction with SP1 and the downstream modulatory of mTOR signaling, thus offering insights into the tumorigenesis mechanism in TNBC.

A feedback loop between lncRNA MALAT1 and DNMT1 promotes triple-negative breast cancer stemness and tumorigenesis

ABSTRACT Background The function of long non-coding RNA (lncRNA) MALAT1 in regulating triple-negative breast cancer (TNBC) stemness and tumorigenesis was investigated. Methods Sphere formation and colony formation assays coupled with flow cytometry were employed to evaluate the percentage of CD44high/CD44low cells, and ALDH+ cells were performed to evaluate the stemness. Bisulfite sequencing PCR (BSP) was employed to detect the methylation level of MALAT1. Tumor xenograft experiment was performed to evaluate tumorigenesis in vivo. Finally, dual-luciferase reporter and RIP assays were employed to verify the binding relationship between MALAT1 and miR-137. Results Our results revealed that MALAT1 and BCL11A were highly expressed in TNBC, while miR-137 and DNMT1 were lowly expressed. Our results proved that MALAT1 positively regulated BCL11A expression through targeting miR-137. Functional experiments revealed that MALAT1 inhibited DNMT1 expression through acting on the miR-137/BCL11A pathway to enhance TNBC stemness and tumorigenesis. We also found that high MALAT1 expression in TNBC was related to the DNMT1-mediated hypomethylation of MALAT1. As expected, DNMT1 overexpression could remarkably inhibit TNBC stemness and tumorigenesis, which was eliminated by MALAT1 overexpression. Conclusion MALAT1 downregulated DNMT1 by miR-137/BCL11A pathway to enhance TNBC stemness and tumorigenesis; meanwhile, DNMT1/MALAT1 formed a positive feedback loop to continuously promote TNBC malignant behaviors.

Hyperglycemia and O-GlcNAc transferase activity drive a cancer stem cell pathway in triple-negative breast cancer

BackgroundEnhanced glucose metabolism is a feature of most tumors, but downstream functional effects of aberrant glucose flux are difficult to mechanistically determine. Metabolic diseases including obesity and diabetes have a hyperglycemia component and are correlated with elevated pre-menopausal cancer risk for triple-negative breast cancer (TNBC). However, determining pathways for hyperglycemic disease-coupled cancer risk remains a major unmet need. One aspect of cellular sugar utilization is the addition of the glucose-derived protein modification O-GlcNAc (O-linked N-acetylglucosamine) via the single human enzyme that catalyzes this process, O-GlcNAc transferase (OGT). The data in this report implicate roles of OGT and O-GlcNAc within a pathway leading to cancer stem-like cell (CSC) expansion. CSCs are the minor fraction of tumor cells recognized as a source of tumors as well as fueling metastatic recurrence. The objective of this study was to identify a novel pathway for glucose-driven expansion of CSC as a potential molecular link between hyperglycemic conditions and CSC tumor risk factors.MethodsWe used chemical biology tools to track how a metabolite of glucose, GlcNAc, became linked to the transcriptional regulatory protein tet-methylcytosine dioxygenase 1 (TET1) as an O-GlcNAc post-translational modification in three TNBC cell lines. Using biochemical approaches, genetic models, diet-induced obese animals, and chemical biology labeling, we evaluated the impact of hyperglycemia on CSC pathways driven by OGT in TNBC model systems.ResultsWe showed that OGT levels were higher in TNBC cell lines compared to non-tumor breast cells, matching patient data. Our data identified that hyperglycemia drove O-GlcNAcylation of the protein TET1 via OGT-catalyzed activity. Suppression of pathway proteins by inhibition, RNA silencing, and overexpression confirmed a mechanism for glucose-driven CSC expansion via TET1-O-GlcNAc. Furthermore, activation of the pathway led to higher levels of OGT production via feed-forward regulation in hyperglycemic conditions. We showed that diet-induced obesity led to elevated tumor OGT expression and O-GlcNAc levels in mice compared to lean littermates, suggesting relevance of this pathway in an animal model of the hyperglycemic TNBC microenvironment.ConclusionsTaken together, our data revealed a mechanism whereby hyperglycemic conditions activated a CSC pathway in TNBC models. This pathway can be potentially targeted to reduce hyperglycemia-driven breast cancer risk, for instance in metabolic diseases. Because pre-menopausal TNBC risk and mortality are correlated with metabolic diseases, our results could lead to new directions including OGT inhibition for mitigating hyperglycemia as a risk factor for TNBC tumorigenesis and progression.

Myc derived circRNA promotes triple-negative breast cancer progression via reprogramming fatty acid metabolism

Myc is a well-known proto-oncogene that is frequently amplified and activated in breast cancer, especially in triple-negative breast cancer (TNBC). However, the role of circular RNA (circRNA) generated by Myc remains unclear. Herein, we found that circMyc (hsa_circ_0085533) was remarkably upregulated in TNBC tissues and cell lines, which was attributed to gene amplification. Genetic knockdown of circMyc mediated by lentiviral vector significantly inhibited TNBC cell proliferation and invasion. Importantly, circMyc increased cellular triglycerides, cholesterols and lipid droplet contents. CircMyc was detected in both cytoplasm and nucleus, cytoplasmic circMyc could directly bind to HuR protein, facilitating the binding of HuR to SREBP1 mRNA, resulting in increasing SREBP1 mRNA stability. Nuclear circMyc bound to Myc protein, facilitating the occupation of Myc on SREBP1 promoter, leading to increasing SREBP1 transcription. As a result, the elevated SREBP1 increased the expression of its downstream lipogenic enzymes, enhancing lipogenesis and TNBC progression. Moreover, the orthotopic xenograft model showed that depletion of circMyc markedly inhibited lipogenesis and reduced tumor size. Clinically, high circMyc was closely related to larger tumor volume, later clinical stage and lymph node metastasis, functioning as an adverse prognostic factor. Collectively, our findings characterize a novel Myc-derived circRNA controlling TNBC tumorigenesis via regulation of metabolic reprogramming, implying a promising therapeutic target.

Abstract 441: Targeting MKK3-MYC complex to reduce racial survival disparity in breast cancer

Abstract Breast cancer is the most common cancer and the leading cause of cancer-related death in women. The triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer. African American women experience up to 2-fold higher incidence of TNBC as compared to White women. Moreover, African Americans die from breast cancer at up to 40% higher rate than White and Hispanic women. However, there is no therapeutic options are currently available to reduce survival disparity in breast cancer. To address this unmet medical need, we develop novel computational methods combined with experimental chemical biology and high-throughput screening (HTS) technologies. Using our specially designed bioinformatics workflow, we discovered that high expression of mitogen-activated protein kinase kinase 3 (MKK3) strongly correlates with worsened clinical outcomes in African American TNBC patients. The analysis of TNBC patient genomic profiles revealed that MKK3 promotes TNBC in part by activating the major tumor driver transcription factor MYC. MYC is a highly appealing therapeutic target in TNBC, however, no approved MYC inhibitors are available. We found that MKK3 binds and activates MYC through protein-protein interaction (PPI) in TNBC cells. Both genetic and pharmacological inhibition of the MKK3/MYC complex suppresses MYC activity and the viability of TNBC cells. Thus, MKK3/MYC interaction represents a novel vulnerability for therapeutic intervention in TNBC. By combining computational modeling with experimental HTS, we have discovered the first small molecule MKK3/MYC PPI inhibitors. For example, a quinoline derivative SGI-1027 disrupts the MKK3/MYC complex in cells and in vitro, inhibits MYC transcriptional activity, and suppresses the viability of TNBC cells. Together, our studies revealed a novel mechanism of TNBC tumorigenesis through MKK3-induced MYC activation, establish a new HTS to enable the discovery of potent and selective inhibitors to regulate MKK3/MYC complex, and may open new clinical strategies to reduce racial disparity in TNBC mortality. Acknowledgments: This work was supported in part by Mary Kay Ash Foundation Grant for Cancer Research (A.A.I.), Emory initiative on Biological Discovery through Chemical Innovation (A.A.I.), NCI’s Informatics Technology for Cancer Research (ITCR) Program (R21CA274620, A.A.I.), NCI Cancer Target Discovery and Development (CTD^2) Network (U01CA217875, H.F.), NCI Emory Lung Cancer SPORE (P50CA217691, H.F.), Career Enhancement Program (A.A.I., P50CA217691), Winship Cancer Institute (NIH 5P30CA138292).

A novel fatty-acid metabolism-based classification for triple negative breast cancer.

The high heterogeneity of triple negative breast cancer (TNBC) is the main clinical challenge for individualized therapy. Considering that fatty acid metabolism (FAM) plays an indispensable role in tumorigenesis and development of TNBC, we proposed a novel FAM-based classification to characterize the tumor microenvironment immune profiles and heterogeneous for TNBC. Weighted gene correlation network analysis (WGCNA) was performed to identify FAM-related genes from 221 TNBC samples in Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) dataset. Then, non-negative matrix factorization (NMF) clustering analysis was applied to determine FAM clusters based on the prognostic FAM-related genes, which chosen from the univariate/multivariate Cox regression model and the least absolute shrinkage and selection operator (LASSO) regression algorithm. Then, a FAM scoring scheme was constructed to further quantify FAM features of individual TNBC patient based on the prognostic differentially expressed genes (DEGs) between different FAM clusters. Systematically analyses were performed to evaluate the correlation between the FAM scoring system (FS) with survival outcomes, genomic characteristics, tumor microenvironment (TME) features and immunotherapeutic response for TNBC, which were further validated in the Cancer Genome Atlas (TCGA) and GSE58812 datasets. Moreover, the expression level and clinical significancy of the selected FS gene signatures were further validated in our cohort. 1860 FAM-genes were screened out using WGCNA. Three distinct FAM clusters were determined by NMF clustering analysis, which allowed to distinguish different groups of patients with distinct clinical outcomes and tumor microenvironment (TME) features. Then, prognostic gene signatures based on the DEGs between different FAM clusters were identified using univariate Cox regression analysis and Lasso regression algorithm. A FAM scoring scheme was constructed, which could divide TNBC patients into high and low-FS subgroups. Low FS subgroup, characterized by better prognosis and abundance with effective immune infiltration. While patients with higher FS were featured with poorer survival and lack of effective immune infiltration. In addition, two independent immunotherapy cohorts (Imvigor210 and GSE78220) confirmed that patients with lower FS demonstrated significant therapeutic advantages from anti-PD-1/PD-L1 immunotherapy and durable clinical benefits. Further analyses in our cohort found that the differential expression of CXCL13, FBP1 and PLCL2 were significantly associated with clinical outcomes of TNBC samples. This study revealed FAM plays an indispensable role in formation of TNBC heterogeneity and TME diversity. The novel FAM-based classification could provide a promising prognostic predictor and guide more effective immunotherapy strategies for TNBC.

The role of activated androgen receptor in cofilin phospho-regulation depends on the molecular subtype of TNBC cell line and actin assembly dynamics.

Triple negative breast cancer (TNBC) is highly metastatic and of poor prognosis. Metastasis involves coordinated actin filament dynamics mediated by cofilin and associated proteins. Activated androgen receptor (AR) is believed to contribute to TNBC tumorigenesis. Our current work studied roles of activated AR and cofilin phospho-regulation during migration of three AR+ TNBC cell lines to determine if altered cofilin regulation can explain their migratory differences. Untreated or AR agonist-treated BT549, MDA-MB-453, and SUM159PT cells were compared to cells silenced for cofilin (KD) or AR expression/function (bicalutamide). Cofilin-1 was found to be the only ADF/cofilin isoform expressed in each TNBC line. Despite a significant increase in cofilin kinase caused by androgens, the ratio of cofilin:p-cofilin (1:1) did not change in SUM159PT cells. BT549 and MDA-MB-453 cells contain high p-cofilin levels which underwent androgen-induced dephosphorylation through increased cofilin phosphatase expression, but surprisingly maintain a leading-edge with high p-cofilin/total cofilin not found in SUM159PT cells. Androgens enhanced cell polarization in all lines, stimulated wound healing and transwell migration rates and increased N/E-cadherin mRNA ratios while reducing cell adhesion in BT549 and MDA-MB-453 cells. Cofilin KD negated androgen effects in MDA-MB-453 except for cell adhesion, while in BT549 cells it abrogated androgen-reduced cell adhesion. In SUM159PT cells, cofilin KD with and without androgens had similar effects in almost all processes studied. AR dependency of the processes were confirmed. In conclusion, cofilin regulation downstream of active AR is dependent on which actin-mediated process is being examined in addition to being cell line-specific. Although MDA-MB-453 cells demonstrated some control of cofilin through an AR-dependent mechanism, other AR-dependent pathways need to be further studied. Non-cofilin-dependent mechanisms that modulate migration of SUM159PT cells need to be investigated. Categorizing TNBC behavior as AR responsive and/or cofilin dependent can inform on decisions for therapeutic treatment.

Novel Chiral Ru(II) Complexes as Potential c-myc G-quadruplex DNA Stabilizers Inducing DNA Damage to Suppress Triple-Negative Breast Cancer Progression.

Currently, effective drugs for triple-negative breast cancer (TNBC) are lacking in clinics. c-myc is one of the core members during TNBC tumorigenesis, and G-rich sequences in the promoter region can form a G-quadruplex conformation, indicating that the c-myc inhibitor is a possible strategy to fight cancer. Herein, a series of chiral ruthenium(II) complexes ([Ru(bpy)2(DPPZ-R)](ClO4)2, Λ/Δ-1: R = -H, Λ/Δ-2: R = -Br, Λ/Δ-3: R = -C≡C(C6H4)NH2) were researched based on their interaction with c-myc G-quadruplex DNA. Λ-3 and Δ-3 show high affinity and stability to decrease their replication. Additional studies showed that Λ-3 and Δ-3 exhibit higher inhibition against different tumor cells than other molecules. Δ-3 decreases the viability of MDA-MB-231 cells with an IC50 of 25.51 μM, which is comparable with that of cisplatin, with an IC50 of 25.9 μM. Moreover, Δ-3 exhibits acceptable cytotoxic activity against MDA-MB-231 cells in a zebrafish xenograft breast cancer model. Further studies suggested that Δ-3 decreases the viability of MDA-MB-231 cells predominantly through DNA-damage-mediated apoptosis, which may be because Δ-3 can induce DNA damage. In summary, the results indicate that Ru(II) complexes containing alkinyl groups can be developed as c-myc G-quadruplex DNA binders to block TNBC progression.

UCHL1 promotes cancer stemness in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a special kind of breast cancer with strong ability of invasion and metastasis. UCHL1 belongs to the ubiquitin carboxy-terminal hydrolase family and is found to be increased in a variety of malignancies, but its expression in TNBC is unknown. First, we analyzed the expression of UCHL1 in 128 TNBC specimens and paired adjacent normal tissues from 17 TNBC patients undergoing curative resection by immunohistochemistry. Then, the relationship between UCHL1 and cancer stemness was investigated by cell flow cytometry, spheroid formation assays and western blot. Moreover, cell scratch assay and Transwell assays were performed to explore whether UCHL1 promotes the migration and invasion of TNBC cells. Finally, we constructed a xenografts model of TNBC cell lines to observe the effect of UCHL1 on tumorigenesis in vivo. UCHL1 was overexpressed in TNBC tissues and associated with poor prognosis. UCHL1 promoted stem cancer cells properties, including the percentage of CD44+/CD24- cells, sphere-forming ability and CSCs related markers. Furthermore, Scratch assay and Transwell assay proved that UCHL1 enhanced the migration and invasion of TNBC cells. The experimental results of xenografts model in nude mice showed that UCHL1 promoted tumorigenesis of TNBC in vivo. UCHL1 may play a role in the malignant progression of TNBC by maintaining the stemness and promoting cell invasion and is expected to become a potential therapeutic target for TNBC patients.

Compounds from diverse natural origin against triple-negative breast cancer: A comprehensive review.

Triple-negative breast cancer (TNBC) is caused due to the lack of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor 2 (HER2) expression. Triple-negative breast cancer is the most aggressive heterogeneous disease that is capable of producing different clones and mutations. Tumorigenesis in TNBC is caused due to the mutation or overexpression of tumor suppressor genes. It is also associated with mutations in the BRCA gene which is linked to hereditary breast cancer. In addition, PARP proteins and checkpoint proteins also play a crucial function in causing TNBC. Many cell signaling pathways are dysregulated in TNBC. Even though chemotherapy and immunotherapy are good options for TNBC treatment, the response rates are still low in general. Many phytochemicals that are derived from natural compounds have shown very good inhibitions for TNBC. Natural compounds have the great advantage of being less toxic, having lesser side effects, and being easily available. The secondary metabolites such as alkaloids, terpenoids, steroids, and flavonoids in natural products make them promising inhibitors of TNBC. Their compositions also offer vital insights into inhibitory action, which could lead to new cancer-fighting strategies. This review can help in understanding how naturally occurring substances and medicinal herbs decrease specific tumors and pave the way for the development of novel and extremely efficient antitumor therapies.

The application of exosomes in the treatment of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a heterogeneous and invasive breast cancer (BC) subtype that is estrogen receptor-negative, progesterone receptor-negative, and human epidermal growth factor receptor 2 (Her2)-negative. So far, the treatment of TNBC is still ineffective due to the lack of well-defined molecular targets. Exosomes are nanosized extracellular vesicles composed of lipid bilayers. They originate from various types of donor cells and release a complex mixture of contents including diverse nucleic acid types (miRNA, LnRNA, siRNA, and DNA) and proteins; after binding to recipient cells the exosomes release their contents that execute their biological functions. Exosomes have been reported to play an important role in the tumorigenesis of TNBC, including tumor initiation, metastasis, angiogenesis, cell proliferation, immune escape, and drug resistance. On the other hand, exosomes can be valuable biomarkers for diagnosis, monitoring, and treatment of TNBC. More interestingly, exosomes can be harnessed as a nanosized drug-delivery system specifically targeting TNBC. In this review, we present the most recent mechanistic findings and clinical applications of exosomes in TNBC therapy, focusing on their use as diagnostic and prognostic biomarkers, nanoscale drug delivery platforms, and immunotherapeutic agents. In addition, the associated challenges and future directions of using exosomes for TNBC treatment will be discussed.

Ubiquitin specific protease 46 potentiates triple negative breast cancer development by stabilizing PGAM1-mediated glycolysis.

Triple-negative breast cancer (TNBC) is a malignancy with high metastasis rate and poor prognosis. Limited drugs are effective for the treatment of TNBC patients. Ubiquitin specific proteases (USPs) are important posttranscription modulators that promote protein stability by reducing the ubiquitination of the proteins. Aberrant expression of USPs is involved in the development of numerous cancers. However, it remains poorly understood on the role of USP46 in TNBC growth and metastasis. In this study, we explored the clinical relevance, function and molecular mechanisms of USP46 in TNBC. USP46 expression was increased in breast cancer tissues. High expression of USP46 was associated with the poorer prognosis of the patients. Overexpression and knockdown experiments demonstrated that USP46 was critical for TNBC cell growth, migration, and tumorigenesis. Mechanistically, USP46 enhanced the protein stability of phosphoglycerate mutase 1 (PGAM1) via direct interaction. Importantly, USP46 stimulated the glycolysis and promoted the malignant growth of TNBC cells through upregulation of PGAM1. Our study reveals that USP46/PGAM1 axis contributes to TNBC progression and is a potential target for the treatment of TNBC patients.

WFDC21P promotes triple-negative breast cancer proliferation and migration through WFDC21P/miR-628/SMAD3 axis.

Long non-coding RNAs (lncRNAs) modulate cell proliferation, cycle, and apoptosis. However, the role of lncRNA-WFDC21P in the tumorigenesis of triple-negative breast cancer (TNBC) remains unclear. Results of this study demonstrated that WFDC21P levels significantly increased in TNBC, which was associated with the poor survival of patients. WFDC21P overexpression significantly promoted TNBC cell proliferation and metastasis. WFDC21P interacted with miR-628-5p, which further suppressed cell proliferation and metastasis by negatively regulating Smad3-related gene expression. Recovery of miR-628-5p weakened the roles of WFDC21P in promoting the growth and metastasis of TNBC cells. Moreover,N6-methyladenosine (m6A) modification upregulated WFDC21P expression in the TNBC cells. WFDC21P and its m6A levels were increased after methyltransferase like 3 (METTL3) overexpression but reduced after METTL3 silencing. The proliferation and metastasis of TNBC cells were promoted by METTL3 overexpression but suppressed by METTL3 silencing. This study demonstrated the vital roles of WFDC21P and its m6A in regulating the proliferation and metastasis of TNBC cells via the WFDC21P/miR-628/SMAD3 axis.