RESUMO
Senescent cells within tumors and their stroma exert complex pro- and anti-tumorigenic functions. However, the identities and traits of these cells, and the potential for improving cancer therapy through their targeting, remain poorly characterized. Here, we identify a senescent subset within previously-defined cancer-associated fibroblasts (CAFs) in pancreatic ductal adenocarcinomas (PDAC) and in premalignant lesions in mice and humans. Senescent CAFs isolated from mouse and humans expressed elevated levels of immune-regulatory genes. Depletion of senescent CAFs, either genetically or using the Bcl-2 inhibitor ABT-199 (venetoclax), increased the proportion of activated CD8+ T cells in mouse pancreatic carcinomas, whereas induction of CAF senescence had the opposite effect. Combining ABT-199 with an immune checkpoint therapy regimen significantly reduced mouse tumor burden. These results indicate that senescent CAFs in PDAC stroma limit the numbers of activated cytotoxic CD8+ T cells, and suggest that their targeted elimination through senolytic treatment may enhance immunotherapy.
Assuntos
Linfócitos T CD8-Positivos , Fibroblastos Associados a Câncer , Carcinoma Ductal Pancreático , Senescência Celular , Imunoterapia , Neoplasias Pancreáticas , Sulfonamidas , Animais , Fibroblastos Associados a Câncer/imunologia , Fibroblastos Associados a Câncer/metabolismo , Fibroblastos Associados a Câncer/patologia , Neoplasias Pancreáticas/imunologia , Neoplasias Pancreáticas/terapia , Neoplasias Pancreáticas/patologia , Neoplasias Pancreáticas/genética , Linfócitos T CD8-Positivos/imunologia , Camundongos , Humanos , Carcinoma Ductal Pancreático/imunologia , Carcinoma Ductal Pancreático/terapia , Carcinoma Ductal Pancreático/patologia , Carcinoma Ductal Pancreático/genética , Senescência Celular/imunologia , Imunoterapia/métodos , Sulfonamidas/farmacologia , Sulfonamidas/uso terapêutico , Camundongos Endogâmicos C57BL , Linhagem Celular Tumoral , Ativação Linfocitária/imunologia , Feminino , Inibidores de Checkpoint Imunológico/farmacologia , Inibidores de Checkpoint Imunológico/uso terapêutico , Adenocarcinoma/imunologia , Adenocarcinoma/terapia , Adenocarcinoma/genética , Adenocarcinoma/patologia , Masculino , Compostos Bicíclicos Heterocíclicos com PontesRESUMO
Senescent cells can influence the function of tissues in which they reside, and their propensity for disease. A portion of adult human pancreatic beta cells express the senescence marker p16, yet it is unclear whether they are in a senescent state, and how this affects insulin secretion. We analyzed single-cell transcriptome datasets of adult human beta cells, and found that p16-positive cells express senescence gene signatures, as well as elevated levels of beta-cell maturation genes, consistent with enhanced functionality. Senescent human beta-like cells in culture undergo chromatin reorganization that leads to activation of enhancers regulating functional maturation genes and acquisition of glucose-stimulated insulin secretion capacity. Strikingly, Interferon-stimulated genes are elevated in senescent human beta cells, but genes encoding senescence-associated secretory phenotype (SASP) cytokines are not. Senescent beta cells in culture and in human tissue show elevated levels of cytoplasmic DNA, contributing to their increased interferon responsiveness. Human beta-cell senescence thus involves chromatin-driven upregulation of a functional-maturation program, and increased responsiveness of interferon-stimulated genes, changes that could increase both insulin secretion and immune reactivity.
Assuntos
Senescência Celular , Montagem e Desmontagem da Cromatina , Células Secretoras de Insulina , Interferons , Humanos , Células Secretoras de Insulina/metabolismo , Senescência Celular/genética , Interferons/metabolismo , Interferons/genética , Secreção de Insulina , Insulina/metabolismo , Cromatina/metabolismo , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Inibidor p16 de Quinase Dependente de Ciclina/genética , Células Cultivadas , Fenótipo Secretor Associado à Senescência/genética , Transcriptoma , Análise de Célula ÚnicaRESUMO
Cellular senescence forms a barrier to tumorigenesis, by inducing cell cycle arrest in damaged and mutated cells. However, once formed, senescent cells often emit paracrine signals that can either promote or suppress tumorigenesis. There is evidence that, in addition to cancer cells, subsets of tumor stromal cells, including fibroblasts, endothelial cells, and immune cells, undergo senescence. Such senescent stromal cells can influence cancer development and progression and represent potential targets for therapy. However, understanding of their characteristics and roles is limited and few studies have dissected their functions in vivo. Here, we discuss current knowledge and pertinent questions regarding the presence of senescent stromal cells in cancers, the triggers that elicit their formation, and their potential roles within the tumor microenvironment.
Assuntos
Neoplasias , Microambiente Tumoral , Humanos , Células Endoteliais , Neoplasias/patologia , Células Estromais/patologia , Carcinogênese/patologiaRESUMO
BACKGROUND: Drug resistance continues to be a major limiting factor across diverse anti-cancer therapies. Contributing to the complexity of this challenge is cancer plasticity, in which one cancer subtype switches to another in response to treatment, for example, triple-negative breast cancer (TNBC) to Her2-positive breast cancer. For optimal treatment outcomes, accurate tumor diagnosis and subsequent therapeutic decisions are vital. This study assessed a novel approach to characterize treatment-induced evolutionary changes of distinct tumor cell subpopulations to identify and therapeutically exploit anticancer drug resistance. METHODS: In this research, an information-theoretic single-cell quantification strategy was developed to provide a high-resolution and individualized assessment of tumor composition for a customized treatment approach. Briefly, this single-cell quantification strategy computes cell barcodes based on at least 100,000 tumor cells from each experiment and reveals a cell-specific signaling signature (CSSS) composed of a set of ongoing processes in each cell. RESULTS: Using these CSSS-based barcodes, distinct subpopulations evolving within the tumor in response to an outside influence, like anticancer treatments, were revealed and mapped. Barcodes were further applied to assign targeted drug combinations to each individual tumor to optimize tumor response to therapy. The strategy was validated using TNBC models and patient-derived tumors known to switch phenotypes in response to radiotherapy (RT). CONCLUSIONS: We show that a barcode-guided targeted drug cocktail significantly enhances tumor response to RT and prevents regrowth of once-resistant tumors. The strategy presented herein shows promise in preventing cancer treatment resistance, with significant applicability in clinical use.
Assuntos
Antineoplásicos , Neoplasias de Mama Triplo Negativas , Humanos , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/patologia , Linhagem Celular Tumoral , Transdução de Sinais , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêuticoRESUMO
OBJECTIVE: Cellular senescence limits tumourigenesis by blocking the proliferation of premalignant cells. Additionally, however, senescent cells can exert paracrine effects influencing tumour growth. Senescent cells are present in premalignant pancreatic intraepithelial neoplasia (PanIN) lesions, yet their effects on the disease are poorly characterised. It is currently unknown whether senolytic drugs, aimed at eliminating senescent cells from lesions, could be beneficial in blocking tumour development. DESIGN: To uncover the functions of senescent cells and their potential contribution to early pancreatic tumourigenesis, we isolated and characterised senescent cells from PanINs formed in a Kras-driven mouse model, and tested the consequences of their targeted elimination through senolytic treatment. RESULTS: We found that senescent PanIN cells exert a tumour-promoting effect through expression of a proinflammatory signature that includes high Cox2 levels. Senolytic treatment with the Bcl2-family inhibitor ABT-737 eliminated Cox2-expressing senescent cells, and an intermittent short-duration treatment course dramatically reduced PanIN development and progression to pancreatic ductal adenocarcinoma. CONCLUSIONS: These findings reveal that senescent PanIN cells support tumour growth and progression, and provide a first indication that elimination of senescent cells may be effective as preventive therapy for the progression of precancerous lesions.
Assuntos
Adenocarcinoma/patologia , Senescência Celular/efeitos dos fármacos , Ciclo-Oxigenase 2/metabolismo , Neoplasias Pancreáticas/patologia , Lesões Pré-Cancerosas/patologia , Senoterapia/uso terapêutico , Adenocarcinoma/metabolismo , Animais , Modelos Animais de Doenças , Camundongos , Neoplasias Pancreáticas/metabolismo , Lesões Pré-Cancerosas/metabolismoRESUMO
The most common events in breast cancer (BC) involve chromosome arm losses and gains. Here we describe identification of 1089 gene-centric common insertion sites (gCIS) from transposon-based screens in 8 mouse models of BC. Some gCIS are driver-specific, others driver non-specific, and still others associated with tumor histology. Processes affected by driver-specific and histology-specific mutations include well-known cancer pathways. Driver non-specific gCIS target the Mediator complex, Ca++ signaling, Cyclin D turnover, RNA-metabolism among other processes. Most gCIS show single allele disruption and many map to genomic regions showing high-frequency hemizygous loss in human BC. Two gCIS, Nf1 and Trps1, show synthetic haploinsufficient tumor suppressor activity. Many gCIS act on the same pathway responsible for tumor initiation, thereby selecting and sculpting just enough and just right signaling. These data highlight ~1000 genes with predicted conditional haploinsufficient tumor suppressor function and the potential to promote chromosome arm loss in BC.
Assuntos
Neoplasias da Mama/genética , Perda de Heterozigosidade/genética , Animais , Neoplasias da Mama/patologia , Transformação Celular Neoplásica , Elementos de DNA Transponíveis/genética , Feminino , Genes Supressores de Tumor , Humanos , Camundongos , Mutagênese Insercional , Neoplasias Experimentais , Transdução de SinaisRESUMO
p16INK4a (CDKN2A) is a central tumor-suppressor and activator of senescence. We recently found that prolonged expression of p16INK4a in epidermal cells induces hyperplasia and dysplasia through Wnt-mediated stimulation of neighboring keratinocytes. The study suggests a pro-tumorigenic function of p16INK4a in early epidermal lesions, which could potentially be targeted by senolytic therapy.
RESUMO
p16INK4a (CDKN2A) is a central tumor suppressor, which induces cell-cycle arrest and senescence. Cells expressing p16INK4a accumulate in aging tissues and appear in premalignant lesions, yet their physiologic effects are poorly understood. We found that prolonged expression of transgenic p16INK4a in the mouse epidermis induces hyperplasia and dysplasia, involving high proliferation rates of keratinocytes not expressing the transgene. Continuous p16INK4a expression increases the number of epidermal papillomas formed after carcinogen treatment. Wnt-pathway ligands and targets are activated upon prolonged p16INK4a expression, and Wnt inhibition suppresses p16INK4a-induced hyperplasia. Senolytic treatment reduces p16INK4a-expressing cell numbers, and inhibits Wnt activation and hyperplasia. In human actinic keratosis, a precursor of squamous cell carcinoma, p16INK4a-expressing cells are found adjacent to dividing cells, consistent with paracrine interaction. These findings reveal that chronic p16INK4a expression is sufficient to induce hyperplasia through Wnt-mediated paracrine stimulation, and suggest that this tumor suppressor can promote early premalignant epidermal lesion formation.
Assuntos
Transformação Celular Neoplásica/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Epiderme/metabolismo , Via de Sinalização Wnt/genética , Animais , Proliferação de Células/genética , Transformação Celular Neoplásica/metabolismo , Células Cultivadas , Inibidor p16 de Quinase Dependente de Ciclina/metabolismo , Humanos , Hiperplasia/genética , Hiperplasia/metabolismo , Queratinócitos/metabolismo , Ceratose/genética , Ceratose/metabolismo , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Papiloma/genética , Papiloma/metabolismo , Papiloma/patologiaRESUMO
Senescence is a cellular phenotype present in health and disease, characterized by a stable cell-cycle arrest and an inflammatory response called senescence-associated secretory phenotype (SASP). The SASP is important in influencing the behavior of neighboring cells and altering the microenvironment; yet, this role has been mainly attributed to soluble factors. Here, we show that both the soluble factors and small extracellular vesicles (sEVs) are capable of transmitting paracrine senescence to nearby cells. Analysis of individual cells internalizing sEVs, using a Cre-reporter system, show a positive correlation between sEV uptake and senescence activation. We find an increase in the number of multivesicular bodies during senescence in vivo. sEV protein characterization by mass spectrometry (MS) followed by a functional siRNA screen identify interferon-induced transmembrane protein 3 (IFITM3) as being partially responsible for transmitting senescence to normal cells. We find that sEVs contribute to paracrine senescence.
Assuntos
Microambiente Celular , Vesículas Extracelulares/metabolismo , Proteínas de Membrana/metabolismo , Comunicação Parácrina , Proteínas de Ligação a RNA/metabolismo , Feminino , Células HEK293 , Humanos , Células MCF-7 , MasculinoRESUMO
Differentiation events contribute to phenotypic cellular heterogeneity within tumors and influence disease progression and response to therapy. Here, we dissect mechanisms controlling intratumoral heterogeneity within triple-negative basal-like breast cancers. Tumor cells expressing the cytokeratin K14 possess a differentiation state that is associated with that of normal luminal progenitors, and K14-negative cells are in a state closer to that of mature luminal cells. We show that cells can transition between these states through asymmetric divisions, which produce one K14+ and one K14- daughter cell, and that these asymmetric divisions contribute to the generation of cellular heterogeneity. We identified several regulators that control the proportion of K14+ cells in the population. EZH2 and Notch increase the numbers of K14+ cells and their rates of symmetric divisions, and FOXA1 has an opposing effect. Our findings demonstrate that asymmetric divisions generate differentiation transitions and heterogeneity, and identify pathways that control breast cancer cellular composition.
Assuntos
Divisão Celular Assimétrica , Neoplasias de Mama Triplo Negativas/patologia , Animais , Linhagem Celular Tumoral , Células Cultivadas , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Feminino , Fator 3-alfa Nuclear de Hepatócito/genética , Fator 3-alfa Nuclear de Hepatócito/metabolismo , Humanos , Queratinas/genética , Queratinas/metabolismo , Camundongos , Receptores Notch/genética , Receptores Notch/metabolismo , Neoplasias de Mama Triplo Negativas/metabolismoRESUMO
The growing use of genomic testing presents new treatment options but also new dilemmas. We describe here a heavily-pretreated metastatic triple negative breast cancer patient who failed to respond to conventional treatment. Genomic analyses were performed that discovered several targetable alterations (e.g. FGFR1, CDK6, INSR) and created a clinical challenge - which target to target first? Our solution to this relatively common scenario was using ex-vivo organ culture (EVOC) system to prioritize treatment directed toward the best molecular target. EVOC enabled the trial of several potent targeted agents (Everolimus, Linsitinib, Palbociclib, AZD4547) and allowed semi-quantitative measurement of tumor response. The best response was to FGFR inhibitor, AZD4547. Consequently, the most accessible FGFR inhibiting agents (Pazopanib, then Nintedanib) were administered and some response was achieved. This report provides a potential rationale for utilizing EVOC system to predict tumor response to targeted therapy when multiple targets are proposed.
Assuntos
Antineoplásicos/farmacologia , Ensaios de Seleção de Medicamentos Antitumorais , Técnicas de Cultura de Órgãos , Animais , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Modelos Animais de Doenças , Resistencia a Medicamentos Antineoplásicos/genética , Ensaios de Seleção de Medicamentos Antitumorais/métodos , Feminino , Perfilação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Imuno-Histoquímica , Camundongos , Pessoa de Meia-Idade , Terapia de Alvo Molecular , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/patologia , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Breast cancer subtypes display distinct biological traits that influence their clinical behavior and response to therapy. Recent studies have highlighted the importance of chromatin structure regulators in tumorigenesis. The RNF20-RNF40 E3 ubiquitin ligase complex monoubiquitylates histone H2B to generate H2Bub1, while the deubiquitinase (DUB) USP44 can remove this modification. We found that RNF20 and RNF40 expression and global H2Bub1 are relatively low, and USP44 expression is relatively high, in basal-like breast tumors compared with luminal tumors. Consistent with a tumor-suppressive role, silencing of RNF20 in basal-like breast cancer cells increased their proliferation and migration, and their tumorigenicity and metastatic capacity, partly through upregulation of inflammatory cytokines. In contrast, in luminal breast cancer cells, RNF20 silencing reduced proliferation, migration and tumorigenic and metastatic capacity, and compromised estrogen receptor transcriptional activity, indicating a tumor-promoting role. Notably, the effects of USP44 silencing on proliferation and migration in both cancer subtypes were opposite to those of RNF20 silencing. Hence, RNF20 and H2Bub1 have contrasting roles in distinct breast cancer subtypes, through differential regulation of key transcriptional programs underpinning the distinctive traits of each subtype.
Assuntos
Neoplasias da Mama/patologia , Histonas/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Neoplasias da Mama/metabolismo , Neoplasias da Mama/mortalidade , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Citocinas/metabolismo , Feminino , Humanos , Interleucina-6/genética , Interleucina-6/metabolismo , Células MCF-7 , Camundongos , NF-kappa B/metabolismo , Receptores de Estrogênio/genética , Receptores de Estrogênio/metabolismo , Taxa de Sobrevida , Fator de Transcrição RelA/antagonistas & inibidores , Fator de Transcrição RelA/genética , Fator de Transcrição RelA/metabolismo , Ubiquitina Tiolesterase , Ubiquitina-Proteína Ligases/antagonistas & inibidores , Ubiquitina-Proteína Ligases/genética , Proteases Específicas de Ubiquitina/antagonistas & inibidores , Proteases Específicas de Ubiquitina/genética , Proteases Específicas de Ubiquitina/metabolismo , UbiquitinaçãoRESUMO
Senescent cells, formed in response to physiological and oncogenic stresses, facilitate protection from tumourigenesis and aid in tissue repair. However, accumulation of such cells in tissues contributes to age-related pathologies. Resistance of senescent cells to apoptotic stimuli may contribute to their accumulation, yet the molecular mechanisms allowing their prolonged viability are poorly characterized. Here we show that senescent cells upregulate the anti-apoptotic proteins BCL-W and BCL-XL. Joint inhibition of BCL-W and BCL-XL by siRNAs or the small-molecule ABT-737 specifically induces apoptosis in senescent cells. Notably, treatment of mice with ABT-737 efficiently eliminates senescent cells induced by DNA damage in the lungs as well as senescent cells formed in the epidermis by activation of p53 through transgenic p14(ARF). Elimination of senescent cells from the epidermis leads to an increase in hair-follicle stem cell proliferation. The finding that senescent cells can be eliminated pharmacologically paves the way to new strategies for the treatment of age-related pathologies.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Compostos de Bifenilo/farmacologia , Nitrofenóis/farmacologia , Proteínas/antagonistas & inibidores , Sulfonamidas/farmacologia , Proteína bcl-X/antagonistas & inibidores , Animais , Proteínas Reguladoras de Apoptose , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Senescência Celular/efeitos dos fármacos , Dano ao DNA , Epiderme/efeitos dos fármacos , Epiderme/metabolismo , Epiderme/patologia , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Regulação da Expressão Gênica , Humanos , Pulmão/efeitos dos fármacos , Pulmão/metabolismo , Pulmão/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Piperazinas/farmacologia , Cultura Primária de Células , Proteínas/genética , Proteínas/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Transdução de Sinais , Proteína Supressora de Tumor p14ARF/genética , Proteína Supressora de Tumor p14ARF/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Proteína bcl-X/genética , Proteína bcl-X/metabolismoRESUMO
Cellular senescence is thought to contribute to age-associated deterioration of tissue physiology. The senescence effector p16(Ink4a) is expressed in pancreatic beta cells during aging and limits their proliferative potential; however, its effects on beta cell function are poorly characterized. We found that beta cell-specific activation of p16(Ink4a) in transgenic mice enhances glucose-stimulated insulin secretion (GSIS). In mice with diabetes, this leads to improved glucose homeostasis, providing an unexpected functional benefit. Expression of p16(Ink4a) in beta cells induces hallmarks of senescence--including cell enlargement, and greater glucose uptake and mitochondrial activity--which promote increased insulin secretion. GSIS increases during the normal aging of mice and is driven by elevated p16(Ink4a) activity. We found that islets from human adults contain p16(Ink4a)-expressing senescent beta cells and that senescence induced by p16(Ink4a) in a human beta cell line increases insulin secretion in a manner dependent, in part, on the activity of the mechanistic target of rapamycin (mTOR) and the peroxisome proliferator-activated receptor (PPAR)-γ proteins. Our findings reveal a novel role for p16(Ink4a) and cellular senescence in promoting insulin secretion by beta cells and in regulating normal functional tissue maturation with age.
Assuntos
Envelhecimento/genética , Senescência Celular/genética , Inibidor p16 de Quinase Dependente de Ciclina/biossíntese , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Envelhecimento/patologia , Animais , Proliferação de Células/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Fibroblastos/metabolismo , Regulação da Expressão Gênica , Glucose/metabolismo , Humanos , Insulina/genética , Secreção de Insulina , Células Secretoras de Insulina/patologia , Camundongos , Camundongos Transgênicos , PPAR gama/genética , Serina-Treonina Quinases TOR/genéticaRESUMO
Cellular heterogeneity is a prominent characteristic of breast cancers, and accumulating evidence indicates that variability in the differentiation state of tumor cells contributes to this phenomenon. Breast cancers are among the tumor types in which the existence of cancer stem cells has been widely supported, and specific markers, including CD44/CD24 and ALDH1, have been consistently used to identify such cells. Recent studies have revealed the potential for dynamic bidirectional transitions of breast cancer cells between differentiated and stem-like phenotypes. In addition, the potential importance of intermediate states along differentiation axes, including the epithelial-to-mesenchymal transition and the basal-luminal differentiation axis, has emerged. These findings provide a view of breast cancer stem cells that departs from the traditional unidirectional hierarchical model, as well as new insights into the mechanisms by which differentiation events contribute to breast cancer biology. Herein we discuss these advances.
Assuntos
Neoplasias da Mama/patologia , Diferenciação Celular , Células-Tronco Neoplásicas/patologia , Transição Epitelial-Mesenquimal , HumanosRESUMO
Genomic instability, a hallmark of cancer, is commonly caused by failures in the DNA damage response. Here we conducted a bioinformatical screen to reveal DNA damage response genes that are upregulated by estrogen and highly mutated in breast and ovarian cancers. This screen identified 53 estrogen-dependent cancer genes, some of which are novel. Notably, the screen retrieved 9 DNA helicases as well as 5 nucleases. DNA2, which functions as both a helicase and a nuclease and plays a role in DNA repair and replication, was retrieved in the screen. Mutations in DNA2, found in estrogen-dependent cancers, are clustered in the helicase and nuclease domains, suggesting activity impairment. Indeed, we show that mutations found in ovarian cancers impair DNA2 activity. Depletion of DNA2 in cells reduces their tumorogenicity in mice. In human, high expression of DNA2 correlates with poor survival of estrogen receptor-positive patients but not of estrogen receptor-negative patients. We also demonstrate that depletion of DNA2 in cells reduces proliferation, while addition of estrogen restores proliferation. These findings suggest that cells responding to estrogen will proliferate despite impaired in DNA2 activity, potentially promoting genomic instability and triggering cancer development.
Assuntos
Neoplasias da Mama/genética , DNA Helicases/genética , Reparo do DNA/genética , Estrogênios/farmacologia , Neoplasias Ovarianas/genética , Animais , Neoplasias da Mama/mortalidade , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Transformação Celular Neoplásica/genética , Dano ao DNA/genética , DNA Helicases/biossíntese , Feminino , Instabilidade Genômica/genética , Humanos , Células MCF-7 , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mutação , Transplante de Neoplasias , Neoplasias Ovarianas/mortalidade , Interferência de RNA , RNA Interferente Pequeno , Receptores de Estrogênio/metabolismo , Transplante HeterólogoRESUMO
Differentiation-associated regulatory programs are central in determining tumor phenotype, and contribute to heterogeneity between tumors and between individual cells within them. The transcriptional programs that control luminal and basal lineage identity in the normal mammary epithelium, as well as progenitor and stem cell function, are active in breast cancers, and show distinct associations with different disease subtypes. Also active in some tumors is the epithelial to mesenchymal transition (EMT) program, which endows carcinoma cells with mesenchymal as well as stem cell traits. The differentiation state of breast cancer cells is thus dictated by the complex combination of regulatory programs, and these can dramatically affect tumor growth and metastatic capacity. Breast cancer differentiation is often viewed along an axis between a basalmesenchymalstem cell state and a luminalepithelialdifferentiated state. Here we consider the links, as well as the distinctions, between the three components of this axis: basal versus luminal, mesenchymal versus epithelial, and stem cell versus differentiated identity. Analysis on a multidimensional scale, in which each of these axes is assessed separately, may offer increased resolution of tumor differentiation state. Cancer cells possessing a high degree of stemness would display increased capacity to shift between positions on such a multidimensional scale, and to acquire intermediate phenotypes on its different axes. Further molecular analysis of breast cancer cells with a focus on single-cell profiling, and the development of improved tools for dissection of the circuits controlling gene activity, are essential for the elucidation of the programs dictating breast cancer differentiation state.
Assuntos
Neoplasias da Mama , Diferenciação Celular , Transição Epitelial-Mesenquimal , Células-Tronco Neoplásicas , Animais , Feminino , Humanos , CamundongosRESUMO
Cellular senescence, a state of cell-cycle arrest accompanied by dramatic morphologic and metabolic changes, is a central means by which cells respond to physiologic stress and oncogene activity. Senescence is thought to play important roles in aging and in tumor suppression, yet the dynamics by which senescent cells are formed, their effects on tissue function and their eventual fate are poorly understood. To study cellular senescence within an adult tissue, we developed transgenic mice inducibly expressing p14(ARF) (human ortholog of murine p19(ARF)), a central activator of senescence. Induction of p14(ARF) in the epidermis rapidly led to widespread apoptosis and cell-cycle arrest, a stage that was transient, and was followed by p53-dependent cellular senescence. The endogenous Cdkn2a products p19(ARF) and p16(Ink4a) were activated by the transgenic p14(ARF) through p53, revealing a senescence-promoting feed-forward loop. Commitment of cells to senescence required continued p14(ARF) expression, indicating that entry into this state depends on a persistent signal. However, once formed, senescent cells were retained in the epidermis, often for weeks after transgene silencing, indicating an absence of an efficient rapidly acting mechanism for their removal. Stem cells in the hair follicle bulge were largely protected from apoptosis upon p14(ARF) induction, but irreversibly lost their ability to proliferate and initiate follicle growth. Interestingly, induction of epidermal hyperplasia prevented the appearance of senescent cells upon p14(ARF) induction. Our findings provide basic insights into the dynamics of cellular senescence, a central tumor- suppressive mechanism, and reveal the potential for prolonged retention of senescent cells within tissues.
Assuntos
Apoptose , Epiderme/metabolismo , Proteína Supressora de Tumor p14ARF/metabolismo , Animais , Ciclo Celular , Senescência Celular , Inativação Gênica , Folículo Piloso/metabolismo , Humanos , Camundongos , Camundongos Transgênicos , Modelos Biológicos , RNA/metabolismo , Transgenes , Proteína Supressora de Tumor p14ARF/fisiologia , Proteína Supressora de Tumor p53/metabolismo , beta-Galactosidase/metabolismoRESUMO
Vav1 functions as a signal transducer protein in the hematopoietic system, where it is exclusively expressed. Vav1 was recently implicated in several human cancers, including lung, pancreatic and neuroblasoma. In this study, we analyzed the expression and function of Vav1 in human breast tumors and breast cancer cell lines. Immunohistochemical analysis of primary human breast carcinomas indicated that Vav1 is expressed in 62% of 65 tumors tested and is correlated positively with estrogen receptor expression. Based on published gene profiling of 50 breast cancer cell lines, several Vav1-expressing cell lines were identified. RT-PCR confirmed Vav1 mRNA expression in several of these cell lines, yet no detectable levels of Vav1 protein were observed due to cbl-c proteasomal degradation. We used two of these lines, MCF-7 (Vav1 mRNA negative) and AU565 (Vav1 mRNA positive), to explore the effect of Vav1 expression on breast cell phenotype and function. Vav1 expression had opposite effects on function in these two lines: it reduced proliferation and enhanced cell death in MCF-7 cells but enhanced proliferation in AU565 cells. Consistent with these findings, transcriptome analysis revealed an increase in expression of proliferation-related genes in Vav1-expressing AU565 cells compared to controls, and an increase in apoptosis-related genes in Vav1-expressing MCF-7 cells compared with controls. TUNEL and γ-H2AX foci assays confirmed that expression of Vav1 increased apoptosis in MCF-7 cells but not AU565 cells and shRNA experiments revealed that p53 is required for this pro-apoptotic effect of Vav1 in these cells. These results highlight for the first time the potential role of Vav1 as an oncogenic stress activator in cancer and the p53 dependence of its pro-apoptotic effect in breast cells.
Assuntos
Apoptose/fisiologia , Neoplasias da Mama/metabolismo , Proteínas Proto-Oncogênicas c-vav/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Apoptose/genética , Neoplasias da Mama/genética , Linhagem Celular , Proliferação de Células , Feminino , Humanos , Imuno-Histoquímica , Imunoprecipitação , Marcação In Situ das Extremidades Cortadas , Proteínas Proto-Oncogênicas c-vav/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína Supressora de Tumor p53/genéticaRESUMO
Regulatory factors controlling stem cell identity and self-renewal are often active in aggressive cancers and are thought to promote their growth and progression. TCF3 (also known as TCF7L1) is a member of the TCF/LEF transcription factor family that is central in regulating epidermal and embryonic stem cell identity. We found that TCF3 is highly expressed in poorly differentiated human breast cancers, preferentially of the basal-like subtype. This suggested that TCF3 is involved in the regulation of breast cancer cell differentiation state and tumorigenicity. Silencing of TCF3 dramatically decreased the ability of breast cancer cells to initiate tumor formation, and led to decreased tumor growth rates. In culture, TCF3 promotes the sphere formation capacity of breast cancer cells and their self-renewal. We found that in contrast to ES cells, where it represses Wnt-pathway target genes, TCF3 promotes the expression of a subset of Wnt-responsive genes in breast cancer cells while repressing another distinct target subset. In the normal mouse mammary gland, Tcf3 is highly expressed in terminal end buds, structures that lead duct development. Primary mammary cells are dependent on Tcf3 for mammosphere formation, and its overexpression in the developing gland disrupts ductal growth. Our results identify TCF3 as a central regulator of tumor growth and initiation, and a novel link between stem cells and cancer.