RESUMEN
The alternative splicing of PML precursor mRNA gives rise to various PML isoforms, yet their expression profile in breast cancer cells remains uncharted. We discovered that PML1 is the most abundant isoform in all breast cancer subtypes, and its expression is associated with unfavorable prognosis in estrogen receptor-positive (ER+) breast cancers. PML depletion reduces cell proliferation, invasion, and stemness, while heterologous PML1 expression augments these processes and fuels tumor growth and resistance to fulvestrant, an FDA-approved drug for ER+ breast cancer, in a mouse model. Moreover, PML1, rather than the well-known tumor suppressor isoform PML4, rescues the proliferation of PML knockdown cells. ChIP-seq analysis reveals significant overlap between PML-, ER-, and Myc-bound promoters, suggesting their coordinated regulation of target gene expression, including genes involved in breast cancer stem cells (BCSCs), such as JAG1, KLF4, YAP1, SNAI1, and MYC. Loss of PML reduces BCSC-related gene expression, and exogenous PML1 expression elevates their expression. Consistently, PML1 restores the association of PML with these promoters in PML-depleted cells. We identified a novel association between PML1 and WDR5, a key component of H3K4 methyltransferase (HMTs) complexes that catalyze H3K4me1 and H3K4me3. ChIP-seq analyses showed that the loss of PML1 reduces H3K4me3 in numerous loci, including BCSC-associated gene promoters. Additionally, PML1, not PML4, re-establishes the H3K4me3 mark on these promoters in PML-depleted cells. Significantly, PML1 is essential for recruiting WDR5, MLL1, and MLL2 to these gene promoters. Inactivating WDR5 by knockdown or inhibitors phenocopies the effects of PML1 loss, reducing BCSC-related gene expression and tumorsphere formation and enhancing fulvestrant's anticancer activity. Our findings challenge the conventional understanding of PML as a tumor suppressor, redefine its role as a promoter of tumor growth in breast cancer, and offer new insights into the unique roles of PML isoforms in breast cancer.
Asunto(s)
Neoplasias de la Mama , Histonas , Factor 4 Similar a Kruppel , Células Madre Neoplásicas , Proteína de la Leucemia Promielocítica , Receptores de Estrógenos , Humanos , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Neoplasias de la Mama/genética , Femenino , Proteína de la Leucemia Promielocítica/metabolismo , Proteína de la Leucemia Promielocítica/genética , Animales , Receptores de Estrógenos/metabolismo , Receptores de Estrógenos/genética , Ratones , Células Madre Neoplásicas/metabolismo , Células Madre Neoplásicas/patología , Histonas/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Péptidos y Proteínas de Señalización Intracelular/genética , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Regulación Neoplásica de la Expresión GénicaRESUMEN
The advent of sequencing technologies for assessing chromosome conformations has provided a wealth of information on the organization of the 3-dimensional genome and its role in cancer progression. It is now known that changes in chromatin folding and accessibility can promote aberrant activation or repression of transcriptional programs that can drive tumorigenesis and progression in diverse cancers. This includes breast cancer, which comprises several distinct subtypes defined by their unique transcriptomes that dictate treatment response and patient outcomes. Of these, basal-like breast cancer is an aggressive subtype controlled by a pluripotency-enforcing transcriptome. Meanwhile, the more differentiated luminal subtype of breast cancer is driven by an estrogen receptor-dominated transcriptome that underlies its responsiveness to antihormone therapies and conveys improved patient outcomes. Despite the clear differences in molecular signatures, the genesis of each subtype from normal mammary epithelial cells remains unclear. Recent technical advances have revealed key distinctions in chromatin folding and organization between subtypes that could underlie their transcriptomic and, hence, phenotypic differences. These studies also suggest that proteins controlling particular chromatin states may be useful targets for treating aggressive disease. In this review, we explore the current state of understanding of chromatin architecture in breast cancer subtypes and its potential role in defining their phenotypic characteristics.
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Neoplasias de la Mama , Humanos , Femenino , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Línea Celular Tumoral , Mama/metabolismo , Cromatina/genética , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión GénicaRESUMEN
Chromatin organization is highly dynamic and modulates DNA replication, transcription, and chromosome segregation. Condensin is essential for chromosome assembly during mitosis and meiosis, as well as maintenance of chromosome structure during interphase. While it is well established that sustained condensin expression is necessary to ensure chromosome stability, the mechanisms that control its expression are not yet known. Herein, we report that disruption of cyclin-dependent kinase 7 (CDK7), the core catalytic subunit of CDK-activating kinase, leads to reduced transcription of several condensin subunits, including structural maintenance of chromosomes 2 (SMC2). Live and static microscopy revealed that inhibiting CDK7 signaling prolongs mitosis and induces chromatin bridge formation, DNA double-strand breaks, and abnormal nuclear features, all of which are indicative of mitotic catastrophe and chromosome instability. Affirming the importance of condensin regulation by CDK7, genetic suppression of the expression of SMC2, a core subunit of this complex, phenocopies CDK7 inhibition. Moreover, analysis of genome-wide chromatin conformation using Hi-C revealed that sustained activity of CDK7 is necessary to maintain chromatin sublooping, a function that is ascribed to condensin. Notably, the regulation of condensin subunit gene expression is independent of superenhancers. Together, these studies reveal a new role for CDK7 in sustaining chromatin configuration by ensuring the expression of condensin genes, including SMC2.
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Cromatina , Quinasas Ciclina-Dependientes , Transducción de Señal , Cromatina/genética , Cromatina/metabolismo , Quinasas Ciclina-Dependientes/genética , Quinasas Ciclina-Dependientes/metabolismo , Mitosis/genética , Inestabilidad Cromosómica/genética , Humanos , Línea Celular Tumoral , Regulación de la Expresión Génica/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Silenciador del GenRESUMEN
Breast cancer subtypes and their phenotypes parallel different stages of the mammary epithelial cell developmental hierarchy. Discovering mechanisms that control lineage identity could provide novel avenues for mitigating disease progression. Here we report that the transcriptional corepressor TLE3 is a guardian of luminal cell fate in breast cancer and operates independently of the estrogen receptor. In luminal breast cancer, TLE3 actively repressed the gene-expression signature associated with highly aggressive basal-like breast cancers (BLBC). Moreover, maintenance of the luminal lineage depended on the appropriate localization of TLE3 to its transcriptional targets, a process mediated by interactions with FOXA1. By repressing genes that drive BLBC phenotypes, including SOX9 and TGFß2, TLE3 prevented the acquisition of a hybrid epithelial-mesenchymal state and reduced metastatic capacity and aggressive cellular behaviors. These results establish TLE3 as an essential transcriptional repressor that sustains the more differentiated and less metastatic nature of luminal breast cancers. Approaches to induce TLE3 expression could promote the acquisition of less aggressive, more treatable disease states to extend patient survival. SIGNIFICANCE: Transcriptional corepressor TLE3 actively suppresses SOX9 and TGFß transcriptional programs to sustain the luminal lineage identity of breast cancer cells and to inhibit metastatic progression.
Asunto(s)
Neoplasias , Factores de Transcripción , Diferenciación Celular , Proteínas Co-Represoras/genética , Receptores de Estrógenos/metabolismo , Factor de Crecimiento Transformador beta , Neoplasias de la Mama/metabolismo , HumanosRESUMEN
The pioneering function of FOXA1 establishes estrogen-responsive transcriptomes in luminal breast cancer. Dysregulated FOXA1 chromatin occupancy through focal amplification, mutation, or cofactor recruitment modulates estrogen receptor (ER) transcriptional programs and drives endocrine-resistant disease. However, ER is not the sole nuclear receptor (NR) expressed in breast cancers, nor is it the only NR for which FOXA1 serves as a licensing factor. Receptors for androgens, glucocorticoids, and progesterone are also found in the majority of breast cancers, and their functions are also impacted by FOXA1. These NRs interface with ER transcriptional programs and, depending on their activation level, can reprogram FOXA1-ER cistromes. Thus, NR interplay contributes to endocrine therapy response and resistance and may provide a vulnerability for future therapeutic benefit in patients. Herein, we review what is known regarding FOXA1 regulation of NR function in breast cancer in the context of cell identity, endocrine resistance, and NR crosstalk in breast cancer progression and treatment.
RESUMEN
Cyclin-dependent kinase 7 (CDK7) is a master regulatory kinase that drives cell cycle progression and stimulates expression of oncogenes in a myriad of cancers. Inhibitors of CDK7 (CDK7i) are currently in clinical trials; however, as with many cancer therapies, patients will most likely experience recurrent disease due to acquired resistance. Identifying targets underlying CDK7i resistance will facilitate prospective development of new therapies that can circumvent such resistance. Here we utilized triple-negative breast cancer as a model to discern mechanisms of resistance as it has been previously shown to be highly responsive to CDK7 inhibitors. After generating cell lines with acquired resistance, high-throughput RNA sequencing revealed significant upregulation of genes associated with efflux pumps and transforming growth factor-beta (TGF-ß) signaling pathways. Genetic silencing or pharmacological inhibition of ABCG2, an efflux pump associated with multidrug resistance, resensitized resistant cells to CDK7i, indicating a reliance on these transporters. Expression of activin A (INHBA), a member of the TGF-ß family of ligands, was also induced, whereas its intrinsic inhibitor, follistatin (FST), was repressed. In resistant cells, increased phosphorylation of SMAD3, a downstream mediator, confirmed an increase in activin signaling, and phosphorylated SMAD3 directly bound the ABCG2 promoter regulatory region. Finally, pharmacological inhibition of TGF-ß/activin receptors or genetic silencing of SMAD4, a transcriptional partner of SMAD3, reversed the upregulation of ABCG2 in resistant cells and phenocopied ABCG2 inhibition. This study reveals that inhibiting the TGF-ß/Activin-ABCG2 pathway is a potential avenue for preventing or overcoming resistance to CDK7 inhibitors.
Asunto(s)
Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/biosíntesis , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Resistencia a Antineoplásicos/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Subunidades beta de Inhibinas/metabolismo , Proteínas de Neoplasias/biosíntesis , Inhibidores de Proteínas Quinasas/farmacología , Transducción de Señal/efectos de los fármacos , Factor de Crecimiento Transformador beta/metabolismo , Neoplasias de la Mama Triple Negativas/metabolismo , Regulación hacia Arriba/efectos de los fármacos , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/genética , Línea Celular Tumoral , Quinasas Ciclina-Dependientes/genética , Quinasas Ciclina-Dependientes/metabolismo , Resistencia a Antineoplásicos/genética , Femenino , Humanos , Subunidades beta de Inhibinas/genética , Proteínas de Neoplasias/genética , Transducción de Señal/genética , Factor de Crecimiento Transformador beta/genética , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Neoplasias de la Mama Triple Negativas/genética , Neoplasias de la Mama Triple Negativas/patología , Quinasa Activadora de Quinasas Ciclina-DependientesRESUMEN
The phenotypes of each breast cancer subtype are defined by their transcriptomes. However, the transcription factors that regulate differential patterns of gene expression that contribute to specific disease outcomes are not well understood. Here, using gene silencing and overexpression approaches, RNA-Seq, and splicing analysis, we report that the transcription factor B-cell leukemia/lymphoma 11A (BCL11A) is highly expressed in triple-negative breast cancer (TNBC) and drives metastatic disease. Moreover, BCL11A promotes cancer cell invasion by suppressing the expression of muscleblind-like splicing regulator 1 (MBNL1), a splicing regulator that suppresses metastasis. This ultimately increases the levels of an alternatively spliced isoform of integrin-α6 (ITGA6), which is associated with worse patient outcomes. These results suggest that BCL11A sustains TNBC cell invasion and metastatic growth by repressing MBNL1-directed splicing of ITGA6 Our findings also indicate that BCL11A lies at the interface of transcription and splicing and promotes aggressive TNBC phenotypes.
Asunto(s)
Regulación Neoplásica de la Expresión Génica , Invasividad Neoplásica/genética , Proteínas Represoras/genética , Neoplasias de la Mama Triple Negativas/genética , Regulación hacia Arriba , Línea Celular Tumoral , Progresión de la Enfermedad , Femenino , Humanos , Invasividad Neoplásica/patología , Metástasis de la Neoplasia/genética , Metástasis de la Neoplasia/patología , Neoplasias de la Mama Triple Negativas/patologíaRESUMEN
BACKGROUND: Triple-negative breast cancer (TNBC) is characterized by high rates of recurrence and poor overall survival. This is due, in part, to a deficiency of targeted therapies, making it essential to identify therapeutically targetable driver pathways of this disease. While epidermal growth factor receptor (EGFR) is expressed in 60% of TNBCs and drives disease progression, attempts to inhibit EGFR in unselected TNBC patients have had a marginal impact on outcomes. Hence, we sought to identify the mechanisms that dictate EGFR expression and inhibitor response to provide a path for improving the utility of these drugs. In this regard, the majority of TNBCs express low levels of the transcription factor, Krüppel-like factor 4 (KLF4), while a small subset is associated with high expression. KLF4 and EGFR have also been reported to have opposing actions in TNBC. Thus, we tested whether KLF4 controls the expression of EGFR and cellular response to its pharmacological inhibition. METHODS: KLF4 was transiently overexpressed in MDA-MB-231 and MDA-MB-468 cells or silenced in MCF10A cells. Migration and invasion were assessed using modified Boyden chamber assays, and proliferation was measured by EdU incorporation. Candidate downstream targets of KLF4, including EGFR, were identified using reverse phase protein arrays of MDA-MB-231 cells following enforced KLF4 expression. The ability of KLF4 to suppress EGFR gene and protein expression and downstream signaling was assessed by RT-PCR and western blot, respectively. ChIP-PCR confirmed KLF4 binding to the EGFR promoter. Response to erlotinib in the context of KLF4 overexpression or silencing was assessed using cell number and dose-response curves. RESULTS: We report that KLF4 is a major determinant of EGFR expression and activity in TNBC cells. KLF4 represses transcription of the EGFR gene, leading to reduced levels of total EGFR, its activated/phosphorylated form (pEGFR), and its downstream signaling intermediates. Moreover, KLF4 suppression of EGFR is a necessary intermediary step for KLF4 to inhibit aggressive TNBC phenotypes. Most importantly, KLF4 dictates the sensitivity of TNBC cells to erlotinib, an FDA-approved inhibitor of EGFR. CONCLUSIONS: KLF4 is a major regulator of the efficacy of EGFR inhibitors in TNBC cells that may underlie the variable effectiveness of such drugs in patients.
Asunto(s)
Antineoplásicos/farmacología , Clorhidrato de Erlotinib/farmacología , Factores de Transcripción de Tipo Kruppel/metabolismo , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Neoplasias de la Mama Triple Negativas/genética , Apoptosis/efectos de los fármacos , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Movimiento Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/genética , Receptores ErbB/metabolismo , Femenino , Humanos , Factor 4 Similar a Kruppel , Factores de Transcripción de Tipo Kruppel/genética , Fosforilación , Transducción de Señal , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/patologíaRESUMEN
A significant therapeutic challenge for patients with cancer is resistance to chemotherapies such as taxanes. Overexpression of LIN9, a transcriptional regulator of cell-cycle progression, occurs in 65% of patients with triple-negative breast cancer (TNBC), a disease commonly treated with these drugs. Here, we report that LIN9 is further elevated with acquisition of taxane resistance. Inhibiting LIN9 genetically or by suppressing its expression with a global BET inhibitor restored taxane sensitivity by inducing mitotic progression errors and apoptosis. While sustained LIN9 is necessary to maintain taxane resistance, there are no inhibitors that directly repress its function. Hence, we sought to discover a druggable downstream transcriptional target of LIN9. Using a computational approach, we identified NIMA-related kinase 2 (NEK2), a regulator of centrosome separation that is also elevated in taxane-resistant cells. High expression of NEK2 was predictive of low survival rates in patients who had residual disease following treatment with taxanes plus an anthracycline, suggesting a role for this kinase in modulating taxane sensitivity. Like LIN9, genetic or pharmacologic blockade of NEK2 activity in the presence of paclitaxel synergistically induced mitotic abnormalities in nearly 100% of cells and completely restored sensitivity to paclitaxel, in vitro. In addition, suppressing NEK2 activity with two distinct small molecules potentiated taxane response in multiple in vivo models of TNBC, including a patient-derived xenograft, without inducing toxicity. These data demonstrate that the LIN9/NEK2 pathway is a therapeutically targetable mediator of taxane resistance that can be leveraged to improve response to this core chemotherapy. SIGNIFICANCE: Resistance to chemotherapy is a major hurdle for treating patients with cancer. Combining NEK2 inhibitors with taxanes may be a viable approach for improving patient outcomes by enhancing mitotic defects induced by taxanes alone.
Asunto(s)
Resistencia a Antineoplásicos/efectos de los fármacos , Mitosis/efectos de los fármacos , Quinasas Relacionadas con NIMA/antagonistas & inhibidores , Proteínas Nucleares/antagonistas & inhibidores , Paclitaxel/farmacología , Taxoides/farmacología , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Proteínas Supresoras de Tumor/antagonistas & inhibidores , Antineoplásicos/administración & dosificación , Antineoplásicos/farmacología , Apoptosis , Línea Celular Tumoral , Senescencia Celular , Centrosoma/enzimología , Femenino , Regulación Neoplásica de la Expresión Génica , Silenciador del Gen , Xenoinjertos , Humanos , Mitosis/genética , Quinasas Relacionadas con NIMA/metabolismo , Proteínas de Neoplasias/antagonistas & inhibidores , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , Paclitaxel/administración & dosificación , Tasa de Supervivencia , Taxoides/administración & dosificación , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/mortalidad , Ensayo de Tumor de Célula Madre , Proteínas Supresoras de Tumor/metabolismo , Regulación hacia ArribaRESUMEN
Activins and inhibins are closely related protein heterodimers with a similar tissue distribution; however, these two complexes have opposing functions in development and disease. Both are secreted cytokine hormones, with activin the primary inducer of downstream signaling cascades and inhibin acting as a rheostat that exquisitely governs activin function. Adding to the complexity of activin signaling, follistatin, a highly glycosylated monomeric protein, binds activin with high affinity and restrains downstream pathway activation but through a mechanism distinct from that of inhibin. These three proteins were first identified as key ovarian hormones in the pituitary-gonadal axis that direct the synthesis and secretion of FSH from the pituitary, hence controlling folliculogenesis. Research during the past 30 years has expanded the roles of these proteins, first by discovering the ubiquitous expression of the trio and then by implicating them in a wide array of biological functions. In concert, these three hormones govern tissue development, homeostasis, and disease in multiple organ systems through diverse autocrine and paracrine mechanisms. In the present study, we have reviewed the actions of activin and its biological inhibitors, inhibin, and follistatin, in mammary gland morphogenesis and cancer.
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Activinas/metabolismo , Folistatina/metabolismo , Inhibinas/metabolismo , Glándulas Mamarias Humanas/metabolismo , Activinas/genética , Animales , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Femenino , Folistatina/genética , Regulación Neoplásica de la Expresión Génica , Humanos , Inhibinas/genética , Transducción de SeñalRESUMEN
Triple-negative breast cancers (TNBC) are highly aggressive, lack FDA-approved targeted therapies, and frequently recur, making the discovery of novel therapeutic targets for this disease imperative. Our previous analysis of the molecular mechanisms of action of bromodomain and extraterminal protein inhibitors (BETi) in TNBC revealed these drugs cause multinucleation, indicating BET proteins are essential for efficient mitosis and cytokinesis. Here, using live cell imaging, we show that BET inhibition prolonged mitotic progression and induced mitotic cell death, both of which are indicative of mitotic catastrophe. Mechanistically, the mitosis regulator LIN9 was a direct target of BET proteins that mediated the effects of BET proteins on mitosis in TNBC. Although BETi have been proposed to function by dismantling super-enhancers (SE), the LIN9 gene lacks an SE but was amplified or overexpressed in the majority of TNBCs. In addition, its mRNA expression predicted poor outcome across breast cancer subtypes. Together, these results provide a mechanism for cancer selectivity of BETi that extends beyond modulation of SE-associated genes and suggest that cancers dependent upon LIN9 overexpression may be particularly vulnerable to BETi. Cancer Res; 77(19); 5395-408. ©2017 AACR.
Asunto(s)
Mitosis/efectos de los fármacos , Proteínas Nucleares/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Proteínas Supresoras de Tumor/antagonistas & inhibidores , Animales , Apoptosis/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Femenino , Humanos , Ratones , Ratones Endogámicos NOD , Ratones SCID , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/patología , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
BACKGROUND: Follistatin (FST) is an intrinsic inhibitor of activin, a member of the transforming growth factor-ß superfamily of ligands. The prognostic value of FST and its family members, the follistatin-like (FSTL) proteins, have been studied in various cancers. However, these studies, as well as limited functional analyses of the FSTL proteins, have yielded conflicting results on the role of these proteins in disease progression. Furthermore, very few have been focused on FST itself. We assessed whether FST may be a suppressor of tumorigenesis and/or metastatic progression in breast cancer. METHODS: Using publicly available gene expression data, we examined the expression patterns of FST and INHBA, a subunit of activin, in normal and cancerous breast tissue and the prognostic value of FST in breast cancer metastases, recurrence-free survival, and overall survival. The functional effects of activin and FST on in vitro proliferation, migration, and invasion of breast cancer cells were also examined. FST overexpression in an autochthonous mouse model of breast cancer was then used to assess the in vivo impact of FST on metastatic progression. RESULTS: Examination of multiple breast cancer datasets revealed that FST expression is reduced in breast cancers compared with normal tissue and that low FST expression predicts increased metastasis and reduced overall survival. FST expression was also reduced in a mouse model of HER2/Neu-induced metastatic breast cancer. We found that FST blocks activin-induced breast epithelial cell migration in vitro, suggesting that its loss may promote breast cancer aggressiveness. To directly determine if FST restoration could inhibit metastatic progression, we transgenically expressed FST in the HER2/Neu model. Although FST had no impact on tumor initiation or growth, it completely blocked the formation of lung metastases. CONCLUSIONS: These data indicate that FST is a bona fide metastasis suppressor in this mouse model and support future efforts to develop an FST mimetic to suppress metastatic progression.
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Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Folistatina/genética , Receptor ErbB-2/genética , Proteínas Supresoras de Tumor/genética , Animales , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/mortalidad , Línea Celular Tumoral , Movimiento Celular/genética , Proliferación Celular , Supervivencia Celular/genética , Bases de Datos Genéticas , Femenino , Folistatina/metabolismo , Humanos , Estimación de Kaplan-Meier , Ratones , Ratones Transgénicos , Metástasis de la Neoplasia , Estadificación de Neoplasias , Pronóstico , Receptor ErbB-2/metabolismo , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Bromodomain and extraterminal (BET) proteins are epigenetic "readers" that recognize acetylated histones and mark areas of the genome for transcription. BRD4, a BET family member protein, has been implicated in a number of types of cancer, and BET protein inhibitors (BETi) are efficacious in many preclinical cancer models. However, the drivers of response to BETi vary depending on tumor type, and little is known regarding the target genes conveying BETi activity in triple-negative breast cancer (TNBC). Here, we show that BETi repress growth of multiple in vitro and in vivo models of TNBC by inducing two terminal responses: apoptosis and senescence. Unlike in other cancers, response to BETi in TNBC is not dependent upon suppression of MYC Instead, both end points are preceded by the appearance of polyploid cells caused by the suppression of Aurora kinases A and B (AURKA/B), which are critical mediators of mitosis. In addition, AURKA/B inhibitors phenocopy the effects of BETi. These results indicate that Aurora kinases play an important role in the growth suppressive activity of BETi in TNBC. Elucidating the mechanism of response to BETi in TNBC should 1) facilitate the prediction of how distinct TNBC tumors will respond to BETi and 2) inform the rational design of drug combination therapies.
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Antineoplásicos/uso terapéutico , Aurora Quinasa A/antagonistas & inhibidores , Aurora Quinasa B/antagonistas & inhibidores , Mama/efectos de los fármacos , Proteínas Nucleares/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/uso terapéutico , Factores de Transcripción/antagonistas & inhibidores , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Animales , Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Aurora Quinasa A/metabolismo , Aurora Quinasa B/metabolismo , Mama/metabolismo , Mama/patología , Proteínas de Ciclo Celular , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Femenino , Humanos , Ratones , Ratones Endogámicos NOD , Ratones SCID , Proteínas Nucleares/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Factores de Transcripción/metabolismo , Neoplasias de la Mama Triple Negativas/metabolismo , Neoplasias de la Mama Triple Negativas/patologíaRESUMEN
The estrogenic properties of bisphenol A (BPA), a ubiquitous synthetic monomer that can leach into the food and water supply, have prompted considerable research into exposure-associated health risks in humans. Endocrine-disrupting properties of BPA suggest it may impact developmental plasticity during early life, predisposing individuals to disease at doses below the oral reference dose (RfD) established by the Environmental Protection Agency in 1982. Herein, we review the current in vivo literature evaluating the carcinogenic properties of BPA. We conclude that there is substantial evidence from rodent studies indicating that early-life BPA exposures below the RfD lead to increased susceptibility to mammary and prostate cancer. Based on the definitions of "carcinogen" put forth by the International Agency for Research on Cancer and the National Toxicology Program, we propose that BPA may be reasonably anticipated to be a human carcinogen in the breast and prostate due to its tumor promoting properties.
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Compuestos de Bencidrilo/toxicidad , Neoplasias de la Mama/inducido químicamente , Transformación Celular Neoplásica/inducido químicamente , Disruptores Endocrinos/toxicidad , Contaminantes Ambientales/toxicidad , Neoplasias de los Genitales Femeninos/inducido químicamente , Neoplasias de los Genitales Masculinos/inducido químicamente , Fenoles/toxicidad , Animales , Neoplasias de la Mama/epidemiología , Femenino , Neoplasias de los Genitales Femeninos/epidemiología , Neoplasias de los Genitales Masculinos/epidemiología , Humanos , Masculino , Medición de Riesgo , Factores de RiesgoRESUMEN
DNA double-strand break (DSB) repair is not only key to genome stability but is also an important anticancer target. Through an shRNA library-based screening, we identified ubiquitin-conjugating enzyme H7 (UbcH7, also known as Ube2L3), a ubiquitin E2 enzyme, as a critical player in DSB repair. UbcH7 regulates both the steady-state and replicative stress-induced ubiquitination and proteasome-dependent degradation of the tumor suppressor p53-binding protein 1 (53BP1). Phosphorylation of 53BP1 at the N terminus is involved in the replicative stress-induced 53BP1 degradation. Depletion of UbcH7 stabilizes 53BP1, leading to inhibition of DSB end resection. Therefore, UbcH7-depleted cells display increased nonhomologous end-joining and reduced homologous recombination for DSB repair. Accordingly, UbcH7-depleted cells are sensitive to DNA damage likely because they mainly used the error-prone nonhomologous end-joining pathway to repair DSBs. Our studies reveal a novel layer of regulation of the DSB repair choice and propose an innovative approach to enhance the effect of radiotherapy or chemotherapy through stabilizing 53BP1.
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Roturas del ADN de Doble Cadena , Reparación del ADN , Regulación Neoplásica de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Enzimas Ubiquitina-Conjugadoras/metabolismo , Camptotecina/química , Línea Celular Tumoral , Supervivencia Celular , Daño del ADN , Células HEK293 , Humanos , Fosforilación , Pronóstico , Complejo de la Endopetidasa Proteasomal/química , ARN Interferente Pequeño/metabolismo , Proteína 1 de Unión al Supresor Tumoral P53 , Ubiquitina/químicaRESUMEN
Resistance to receptor tyrosine kinase (RTK) blockade in breast cancer is often mediated by activation of bypass pathways that sustain growth. Src and mammalian target of rapamycin (mTOR) are two intrinsic targets that are downstream of most RTKs. To date, limited clinical efficacy has been observed with either Src or mTOR inhibitors when used as single agents. Resistance to mTOR inhibitors is associated with loss of negative feedback regulation, resulting in phosphorylation and activation of AKT. Herein, we describe a novel role for Src in contributing to rapalog-induced AKT activation. We found that dual activation of Src and the mTOR pathway occurs in nearly half of all breast cancers, suggesting potential cross-talk. As expected, rapamycin inhibition of mTOR results in feedback activation of AKT in breast cancer cell lines. Addition of the Src/c-Abl inhibitor, dasatinib, completely blocks this feedback activation, confirming convergence between Src and the mTOR pathway. Analysis in vivo revealed that dual Src and mTOR inhibition is highly effective in two mouse models of breast cancer. In a luminal disease model, combined dasatinib and rapamycin is more effective at inducing regression than either single agent. Furthermore, the combination of dasatinib and rapamycin delays tumor recurrence following the cessation of treatment. In a model of human EGFR-2-positive (HER2(+)) disease, dasatinib alone is ineffective, but potentiates the efficacy of rapamycin. These data suggest that combining mTOR and Src inhibitors may provide a new approach for treating multiple breast cancer subtypes that may circumvent resistance to targeted RTK therapies.
Asunto(s)
Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Genes src/genética , Proteínas Proto-Oncogénicas c-akt/genética , Sirolimus/farmacología , Serina-Treonina Quinasas TOR/antagonistas & inhibidores , Serina-Treonina Quinasas TOR/genética , Animales , Línea Celular Tumoral , Dasatinib , Resistencia a Antineoplásicos/genética , Femenino , Humanos , Células MCF-7 , Ratones , Fosforilación/efectos de los fármacos , Fosforilación/genética , Proteínas Proto-Oncogénicas c-abl/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-abl/genética , Pirimidinas/farmacología , Ratas , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Tiazoles/farmacologíaRESUMEN
Breast cancer is a heterogeneous disease comprised of distinct subtypes predictive of patient outcome. Tumors of the basal-like subtype have a poor prognosis due to inherent aggressiveness and the lack of targeted therapeutics. Basal-like tumors typically lack estrogen receptor-α, progesterone receptor and HER2/ERBB2, or in other words they are triple negative (TN). Continued evaluation of basal-like breast cancer (BLBC) biology is essential to identify novel therapeutic targets. Expression of the pi subunit of the GABA(A) receptor (GABRP) is associated with the BLBC/TN subtype, and herein, we reveal its expression also correlates with metastases to the brain and poorer patient outcome. GABRP expression in breast cancer cell lines also demonstrates a significant correlation with the basal-like subtype suggesting that GABRP functions in the initiation and/or progression of basal-like tumors. To address this postulate, we stably silenced GABRP in two BLBC cell lines, HCC1187 and HCC70 cells. Decreased GABRP reduces in vitro tumorigenic potential and migration concurrent with alterations in the cytoskeleton, specifically diminished cellular protrusions and expression of the BLBC-associated cytokeratins, KRT5, KRT6B, KRT14, and KRT17. Silencing GABRP also decreases phosphorylation of extracellular regulated kinase 1/2 (ERK1/2) in both cell lines and selective inhibition of ERK1/2 similarly decreases the basal-like cytokeratins as well as migration. Combined, these data reveal a GABRP-ERK1/2-cytokeratin axis that maintains the migratory phenotype of basal-like breast cancer. GABRP is a component of a cell surface receptor, thus, these findings suggest that targeting this new signaling axis may have therapeutic potential in BLBC.
Asunto(s)
Neoplasias de la Mama/patología , Sistema de Señalización de MAP Quinasas , Receptores de GABA-A/fisiología , Neoplasias de la Mama/enzimología , Línea Celular , Activación Enzimática , Perfilación de la Expresión Génica , Silenciador del Gen , Humanos , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores de GABA-A/genética , Análisis de SupervivenciaRESUMEN
Expression of FOXC1, a forkhead box transcription factor, correlates with the human basal-like breast cancer (BLBC) subtype, and functional analyses have revealed its importance for in vitro invasiveness of BLBC cells. Women diagnosed with this breast tumor subtype have a poorer outcome because of the lack of targeted therapies; thus, continued investigation of factors driving these tumors is critical to uncover novel therapeutic targets. Several processes that dictate normal mammary morphogenesis parallel cancer progression, and enforced expression of FOXC1 can induce a progenitor state in more-differentiated mammary epithelial cells. Consequently, evaluating how FOXC1 functions in the normal gland is critical to further understand BLBC biology. Although FOXC1 is well known to control normal development of a number of tissues, its role in the mammary gland has not yet been investigated. Herein, we describe FOXC1 expression patterning in the normal breast, where it is localized to the basal/myoepithelium, suggesting that FOXC1 would be required for normal development. However, mammary glands lacking Foxc1 have no overt defect in ductal outgrowth, alveologenesis, or lineage specification. Of significant interest, we found that expression of FOXC1 is enriched in the normal luminal progenitor population, which is the postulated cell of origin of BLBC. These results indicate that FOXC1 is unnecessary for mammary morphogenesis and that its role in BLBC likely involves processes that are unrelated to cell lineage specification.