Name: silencing of brca2 to identify novel brca2-regulated biological functions in cultured human cells
Uploaded: 2015-08-12T14:00:00.000+00:00
Duration: 9 min 24 s
Description: Watch this Scientific Journal Video about Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells at JoVE.com

This work was supported by FIRB-Merit grants RBNE08YFN3_005 and RBNE08HWLZ_012, and the Italian Ministry of Economy and Finance to the CNR for the Project &#8220;FaReBio di Qualit&#224;&#8221;.

1. Prepare soluções siRNA <ol><li> Ressuspender 5 nmol de embaralhada (Ctrl) e 5 nmol de BRCA2 siRNA peletes secos em 100 ul de água isenta de RNase (concentração final de siRNA: 50 uM). Este é o banco de siRNA e deve ser armazenado a -20 ° C em alíquotas de 10 ul. </li><li> Tomar uma aliquota de 10 ul de estoque de siRNA e adicionar 40 ul de água isenta de RNase para obter a solução de trabalho a 10 ^ M de siARN. Esta diluição deve ser armazenado a -20 ° C até à sua utilização. NOTA: A solução de trabalho siRNA não devem ser submetidos a congelamento / descongelamento mais de 3 vezes. </li></ol> 2. Sementeira de linhas celulares epiteliais humanas <ol><li> Remover o meio de crescimento de linhas celulares epiteliais humanas que crescem como monocamadas celulares em placas de cultura de tecidos numa incubadora humidificada a 37 ° C, 5% de CO 2. </li><li> Lavam-se as células na placa uma vez com PBS temperatura ambiente (10 ml de PBS para uma placa de 100 mm). </li><li> Para retirar as células a partir da placa,adicionar 2 ml de tripsina a 0,25% / solução de 0,53 mM de EDTA e incubar 3-5 minutos, dependendo do tipo de célula. </li><li> Antes de recolher as células destacadas, neutralizar a tripsina por adição de 2 ml de meio de crescimento completo contendo 10% de soro fetal bovino. </li><li> Transferir as células para um tubo de 15 ml. </li><li> Centrifugar as células a 320-330 x g durante 3 min a 4 ° C num rotor de balde oscilante. </li><li> Ressuspender as peletes de células em 5 ml de meio livre de antibióticos. </li><li> Contar as células ao microscópio numa câmara de Burker, quer utilizando um sistema automatizado de contagem de acordo com as instruções do fabricante. </li><li> Semente as células em placas de 6 poços para ser cerca de 80% confluente após 24 horas (0,5-1 x 10 6 células em 2 ml de meio para cada poço). O número de células óptimas a serem semeadas podem variar dependendo das linhas de células específicas e a taxa de crescimento. NOTA: Não adicionar antibióticos a médio neste momento porque os antibióticos irá interferir negativamente com a eficiência de transfection. É muito importante que as células estão na cultura de passagens baixas (&lt;10) para atingir uma elevada eficiência de transfecção siRNA BRCA2. </li></ol> 3. Células de transfecção com siRNA <ol><li> Vinte e quatro horas após o plaqueamento das células, prosseguir com a primeira rodada de transfecção. <ol><li> Dilui-se 6 ul de 10 siRNA reagente de transfecção à base de lípidos específicos, em 130 ul de meio de soro reduzido. </li><li> Dilui-se 3 ul de siRNA 10 uM (30 pmol) em 130 ul de meio de soro reduzido. </li><li> Combinar o siARN diluiu-se com o reagente de transfecção diluído e incubar durante 5-10 min à temperatura ambiente. </li><li> Durante a incubação, remover o meio das células e adicionar 2 ml de meio fresco pré-aquecido a 37 ° C (sem antibióticos). </li><li> Adicionar 250 ul de complexos de siRNA-reagentes de transfecção para as células (este valor é para um único poço de uma placa de 6 poços). </li><li> Incubam-se as células numa incubadora humidificada a 3776; C com 5% de CO 2. </li></ol></li><li> Após 24 horas, prosseguir com a segunda rodada de transfecção por passos 3.1.1-3.1.5 repetindo com a seguinte modificação para a etapa 3.1.2: diluir 5 ul de 10 mM siRNA (50 pmol) em 130 mL de meio de soro reduzido. <ol><li> Incubam-se as células durante 1-2 dias a 37 ° C antes da análise. NOTA: Duas rodadas de transfecções e uso de uma relação de reagente alta siRNA / transfecção na segunda rodada são essenciais para obter alta eficiência do BRCA2 silenciamento. </li></ol></li></ol> 4. Lisar as células para análise de imunotransferência <ol><li> Preparar tampão de lise fresco com PBS (pH 7,4) contendo 1% do não iónico, não-detergente desnaturante octilfenoxipolietoxietanol, pirofosfato de sódio a 5 mM, ortovanadato de sódio 1 mM, fluoreto de sódio 10 mM, fluoreto de fenilmetilsulfonilo 2 mM, 10 ug / ml de leupeptina, 10 ug / ml de aprotinina. Mantê-lo em gelo. </li><li> Remover o meio das células e wash-los uma vez com PBS frio (2 ml / poço) na placa. Para evitar qualquer transição PBS, removê-la completamente a partir da placa. </li><li> Adicionar 200 ul de tampão de lise a cada poço. NOTA: Se as células têm de ser usado também para outros ensaios, trypsinize as células tal como descrito no passo 2,1-2,6 e ressuspender as células em tampão / meio apropriado de acordo com a aplicação a ser utilizada. </li><li> Rodar suavemente a placa para distribuir uniformemente o tampão de lise e incubar durante 15 min a 4 ° C num rotor. </li><li> Recolhe-se o lisado celular num tubo de microcentrífuga em gelo usando um raspador de células. </li><li> Centrifugar a 17.900 xg durante 25 min a 4 ° C e recolher o sobrenadante num novo tubo. </li><li> Medir a concentração de proteína usando um ensaio de proteína disponível comercialmente de acordo com as instruções do fabricante. </li></ol> Análise immunoblotting 5. BRCA2 <ol><li> Preparar o tampão de corrida, diluindo 50 ml de 20x de Tris-Acetato de SDS execução bpode ser prejudicado (Tricina 50 mM, 50 mM Tris Base, 0,1% de SDS, pH 8,24) com 950 ml de água destilada. </li><li> Preparar a amostra como se segue: adicionar 15? G de lisado celular total, 5 uL de tampão de amostra 4x contendo sulfato de dodecilo de lítio, a pH 8,4, 2 mL de amostra de 10x agente redutor (DTT 0,5 M) e tampão de lise para um volume final de 20 ul. NOTA: Este protocolo permite a detecção de BRCA2 em linhas de células normais, também quando se utiliza uma menor quantidade de proteínas totais (inferior a 5 ug). </li><li> Desnaturar amostras a 55 ° C durante 10 min. NOTA: É fundamental usar 55 ° C. Desde que a proteína BRCA2 é termossensível 11, as temperaturas de desnaturação mais elevadas resultam em perda consistente dos intacto de comprimento completo (390 kDa) da proteína BRCA2. </li><li> Defina-se a câmara de electroforese de acordo com as instruções do fabricante. </li><li> Coloque as amostras e 10 ul de alto peso molecular pré-corados padrão de proteína em um gel precasted (Tris-Acetato de 3-8%) e executado em 120 V para aba 2 horas 12. Parar a corrida eletroforética antes do 55 kDa marcador azul deixa o gel precasted. </li><li> Preparar o tampão de transferência com 50 ml de tampão de transferência 20x, 100 ml de metanol a 100% e 850 ml de água. </li><li> Activar a membrana de PVDF (tamanho do poro de 0,45 um) por imersão em 100% de metanol durante 5 minutos, enxaguar com água destilada e equilibrar em tampão de transferência, pelo menos, durante 5 min. Soak as esponjas do aparelho de transferência com tampão de transferência a 4 ° C até à sua utilização. </li><li> Quando a corrida eletroforética é longo, montar o sanduíche na pilha de transferência na seguinte ordem (bottom-up): três esponjas saturadas em tampão de transferência, uma folha de papel 3MM grau saturado em tampão de transferência, o gel, membrana PVDF ativado, um 3MM folha de papel grau saturado em tampão de transferência, três esponjas saturado em tampão de transferência 13,14. Colocar a pilha no aparelho e as proteínas de transferência em 350 mA durante 4 horas a 4 ° C ou a 180 mA durante a noite a 4 ° C. NOTA: Ser BRCA2 uma proteína muito grande, é crucial para estender o tempo de transferência de 1 hora (tal como sugerido pelo fabricante, e a maioria dos protocolos de transferência) a 4 horas ou durante a noite para assegurar a transferência completa de proteínas de alto peso molecular. Além disso, devido ao longo tempo de transferência, que é essencial para realizar o blotting numa sala fria a 4 ° C para minimizar o sobreaquecimento e facilitar a desmontagem sanduíche. Sistemas de transferência semi-secas não são bons para a transferência de grandes proteínas. </li><li> Após a transferência, lavar a membrana com TBS, bloqueá-lo durante 1 hora à temperatura ambiente em TBS-Tween 0,25% (TBS-T) contendo 5% de leite seco sem gordura e a sonda durante a noite a 4 ° C com 30 ul de anti-anticorpo policlonal de coelho BRCA2 ( 200 ug / ml), diluído em 9 ml de TBS-T + 5% de leite em pó magro [1: 300 (v / v)] de diluição. </li><li> Lava-se a membrana três vezes (10 minutos cada) com TBS-T, em seguida, o filtro incubar durante 1 hora com 1 ml de peroxidase de rábano conjugado com anti-anticorpo secundário de coelho diluído em 10 ml de TBS-T + 5% de leite em pó magro. Em seguida, lava-se a membrana três vezes (10 minutos cada) com TBS-T. </li><li> Realizar imunodetecção por ECL para revelar proteína BRCA2 usando quimioluminescência aumentada (ECL) de Reagente de Detecção de Western Blotting, seguindo as instruções do fabricante. Visualize bandas imunoquimioluminométricos sobre filmes de alta resolução ECL. </li><li> Realizar imunodetecção com um anticorpo para um gene de manutenção, como β-tubulina (55 kDa), no mesmo filtro como controlo de carga, utilizando um anticorpo monoclonal para β-tubulina diluído a 1: 1000 (10 ul de anticorpo anti-tubulina em 10 ml de TBS-T + 5% de leite seco não gordo) durante 1 h à TA. Lavar e incubar o anticorpo secundário como descrito para BRCA2 (5,10-5,11), excepto na utilização de peroxidase de rábano conjugado com anti-ratinho em vez do anticorpo secundário anti-coelho. </li><li> Adquirir uma imagem digital dos filmes impressionados com bandas imunoquimioluminométricos e analisar a intensidade da banda por imagem dedicada software de análise (por exemplo,., ImageJ). </li></ol>

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The authors have nothing to disclose.

Porque mutações germinativas do gene BRCA2 chumbo ao aumento do risco de diversos tipos de câncer, incluindo o câncer feminino e masculino de mama, câncer de ovário, câncer de próstata, câncer de pâncreas e melanoma 3,4, uma série de estudos têm sido realizados para compreender a função biológica da proteína BRCA2. A maioria destes estudos são baseados em genética, principalmente devido a dificuldades técnicas na análise de uma proteína gigante como BRCA2. O método descrito aqui...

O gene BRCA2 (cancro da mama susceptibilidade gene-2) codifica para uma proteína supressora de tumor que desempenha um papel crucial na reparação de DNA quebras de cadeia dupla através da regulação da função da enzima recombinase Rad51 1. BRCA2 também tem sido implicado na modulação da transcrição e o controlo do ciclo celular em dois. Mutações da linha germinativa no gene BRCA2 induzir uma autossómica dominante susceptibilidade para cancro da mama e do cancro do ovário em mulheres e cancro da próstata em homens, assim como a predisposição para outros tipos de cancro 3,4. No entanto, apesar do aumento do risco de desenvolvimento de cancro, BRCA2 que suprimem ou reduzem a função BRCA2 pode tornar as células de cancro mais vulnerável a agentes quimioterapêuticos que provocam danos no DNA 5-7. Cânceres esporádicos apresentam uma baixa taxa de mutações BRCA2 (&lt;3%) que os níveis reduzidos de proteína BRCA2 foram detectados em alguns tipos de câncer, o que sugere que a proteína BRCA2podem ser perdidos durante a tumorigênese em cânceres esporádicos através de mecanismos não-mutacional-dependentes 7,8. Assim, é importante compreender as funções BRCA2 no contexto da biologia do cancro, bem como em outras configurações biológicos. Uma poderosa ferramenta utilizada para identificar novos funções de um gene em células de mamífero é silenciar a sua expressão. Como um exemplo, o silenciamento BRCA2 expressão numa variedade de células epiteliais normais levou recentemente à identificação de uma nova função de BRCA2 como regulador de resistência anoikis, um passo importante durante a aquisição de célula de cancro invasivo e metastático capacidade 9. Gene silenciamento pode ser alcançado através da introdução nas células ou de interferência (Si) ou ARN pequeno gancho de cabelo curto (sh) moléculas de RNA alvo do gene específico. A alta potência de siRNA e sua facilidade de uso tornam a ferramenta preferencial para silenciar experiências destinadas a ganhar novos insights sobre processos biológicos críticos umnd para identificar novos alvos terapêuticos. No entanto, knockdown eficiente da expressão do gene pode não ser facilmente possível para todos os genes e pode ser altamente variável dependendo do tipo de célula. Porque a diminuição dos níveis de proteína intracelular é o fenótipo mais relevante sob investigação, que é fundamental para quantificar o silenciamento do gene por análise de imunotransf erência do produto do gene. Com este respeito, a proteína BRCA2 apresenta um desafio adicional: sendo uma proteína grande (cerca de 390 kDa), dificuldades técnicas existem para análise bioquímica convencional, incluindo a imunotransferência. Nós relatamos aqui um protocolo otimizado para silenciamento eficiente do BRCA2 em linhas de células epiteliais humanas e para a detecção rápida e bem sucedida de proteína BRCA2 knockdown por immunoblotting análise.

<table><tbody><tr><td>BRCA2 siRNA</td><td>Dharmacon</td><td>L-003462-00</td><td>SMARTpool: ON-TARGETplus BRCA2 siRNA</td></tr><tr><td>Ctrl siRNA</td><td>Dharmacon</td><td>&amp;nbsp;D-001810-10-05</td><td>ON-TARGETplus Non-targeting Pool</td></tr><tr><td>Lipofectamine RNAiMAX Reagent&amp;nbsp;</td><td>Life Technologies</td><td>&lt;a href=&quot;http://www.lifetechnologies.com/order/catalog/product/13778075&quot;&gt;13778075&lt;/a&gt;</td><td>Transfection Reagent</td></tr><tr><td>OPTI-MEM I Reduced Serum Medium</td><td>Life Technologies</td><td>31985-070</td><td>Medium for transfection procedure</td></tr><tr><td>NuPAGE Tris-Acetate 3-8% 1,5 mm Gel precast</td><td>Life Technologies</td><td>EA0378</td><td>Gel for protein electrophoresis</td></tr><tr><td>NuPAGE LDS Sample buffer&amp;nbsp;</td><td>Life Technologies</td><td>NP0007</td><td>Reagent for protein electrophoresis</td></tr><tr><td>NuPAGE Sample Reducing agent (10x)</td><td>Life Technologies</td><td>NP0004</td><td>Reagent for protein electrophoresis</td></tr><tr><td>NuPAGE Antioxidant</td><td>Life Technologies</td><td>NP0005</td><td>Reagent for protein electrophoresis</td></tr><tr><td>HiMark Pre-stained protein standard</td><td>Life Technologies</td><td>LC5699</td><td>Prestained marker for gel electrophoresis</td></tr><tr><td>XCell SureLoc Mini-Cell&amp;nbsp; System</td><td>Life Technologies</td><td>EI0002</td><td>Equipment for protein electrophoresis/transfer</td></tr><tr><td>NuPAGE Tris-Acetate SDS Running Buffer</td><td>Life Technologies</td><td>LA0041</td><td>Reagent for Western blotting</td></tr><tr><td>PVDF membrane</td><td>Millipore</td><td>IPVH00010</td><td>Reagent for Western blotting</td></tr><tr><td>NuPAGE Transfer Buffer</td><td>Life Technologies</td><td>NP0006-1</td><td>Reagent for Western blotting</td></tr><tr><td>BRCA2 H-300 rabbit polyclonal antibody</td><td>Santa Cruz Biotechnology</td><td>sc-8326</td><td>1:300 dilution</td></tr><tr><td>Beta-tubulin monoclonal antibody</td><td>Sigma Aldrich</td><td>T4026-100UL</td><td>1:1,000 dilution</td></tr><tr><td>Skim Milk powder</td><td>Sigma Aldrich</td><td>70166</td><td>Reagent for Western blotting</td></tr><tr><td>Tween-20</td><td>Sigma Aldrich</td><td>P1379</td><td>Reagent for Western blotting</td></tr><tr><td>SuperSignal West Pico/Femto Chemiluminescent Substrate</td><td>Pierce Thermo Scientific</td><td>34080/34096</td><td>Chemiluminescence system</td></tr><tr><td>PNT1A cells</td><td>SIGMA Aldrich (for ECACC)</td><td>95012614</td><td>PNT1A human, normal prostate epithelium immortalized with SV40</td></tr><tr><td>Nthy cells</td><td>SIGMA Aldrich (for ECACC)</td><td>90011609</td><td>Nthy-ori 3-1 Cell Line human, thyroid follicular epithelial cells</td></tr><tr><td>Cell Proliferation Kit I (MTT)</td><td>Roche</td><td>11465007001</td><td>Kit for cell proliferation assays</td></tr></tbody></table>

silencing of brca2 to identify novel brca2-regulated biological functions in cultured human cells

O silenciamento do BRCA2 proteína supressora de tumor e sua detecção por análises bioquímicas convencionais representam um grande desafio técnico, devido ao grande tamanho da proteína BRCA2 humano (cerca de 390 kDa). Relatamos modificações de transfecção e immunoblotting protocolos padrão de siRNA para silenciar BRCA2 e detectar a proteína humana endógena BRCA2, respectivamente, em linhas de células epiteliais humanas. Passos-chave incluem um elevado siRNA à relação de reagente de transfecção e duas rodadas subseqüentes de transfecção siRNA dentro do mesmo experimento. Usando estas e outras modificações introduzidas no protocolo padrão que consistentemente conseguir mais do que 70% silenciamento do gene BRCA2 humano, tal como avaliado por análise de imunotransf erência com anticorpos anti-BRCA2. Além disso, a desnaturação dos lisados ​​celulares a 55 ° C em vez da convencional de 70-100 ° C e outras optimizações técnicas do procedimento de imunotransferência permitir a detecção de proteína intacta, mesmo BRCA2 when quantidades muito pequenas de material de partida estão disponíveis ou quando os níveis de expressão de proteína BRCA2 são muito baixos. Silenciamento eficaz de BRCA2 em células humanas oferece uma estratégia terapêutica valiosa para interromper a função BRCA2 em células intactas com BRCA2, incluindo as células tumorais, para examinar novas vias moleculares e as funções celulares que podem ser afectadas por mutações em tumores BRCA2 patogénicos. Adaptação deste protocolo para silenciamento e análise de outras proteínas &quot;grandes&quot; como BRCA2 eficiente deve ser facilmente alcançável.

Antes de prosseguir com um ensaio biológico / bioquímicas para examinar o efeito de silenciamento BRCA2 em funções celulares, o primeiro passo é para confirmar a especificidade do silenciamento usando um siRNA mexidos (não-alvo siARN) lado a lado com BRCA2 siRNA (Figura 1A ). É importante a realização de um segundo turno de transfecção com o siRNA um elevado rácio de siRNA / transfecção para obter uma elevada eficiência de silenciamento BRCA2. Com efeito, a realização ...

Watch this Scientific Journal Video about Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells at JoVE.com

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Gene silencing by siRNA represents a convenient experimental strategy to analyze BRCA2-dependent biological functions with immediate implications to better understand cancer biology. A method to efficiently silence BRCA2, along with the experimental procedure to detect and quantify changes in BRCA2 protein expression by immunoblotting in human cell lines, is presented.

Silenciamento de<em&gt; BRCA2</em&gt; Identificar funções biológicas regulada-BRCA2 romance em células humanas de cultura

Silencing of the tumor suppressor protein BRCA2 and its detection by conventional biochemical analyses represent a great technical challenge owing to the ...

silencing-brca2-to-identify-novel-brca2-regulated-biological

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Biology

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

9.0K visualizações.  National Research Council. Gene silencing by siRNA represents a convenient experimental strategy to analyze BRCA2-dependent biological functions with immediate implications to better understand cancer biology. A method to efficiently silence BRCA2, along with the experimental procedure to detect and quantify changes in BRCA2 protein expression by immunoblotting in human cell lines, is presented. 

Vídeo: Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Utilizing Functional Genomics Screening to Identify Potentially Novel Drug Targets in Cancer Cell Spheroid Cultures

The identification of functional driver events in cancer is central to furthering our understanding of cancer biology and indispensable for the discovery of the next generation of novel drug targets. It is becoming apparent that more complex models of cancer are required to fully appreciate the contributing factors that drive tumorigenesis in vivo and increase the efficacy of novel therapies that make the transition from pre-clinical models to clinical trials.
Here we present a methodology for generating uniform and reproducible tumor spheroids that can be subjected to siRNA functional screening. These spheroids display many characteristics that are found in solid tumors that are not present in traditional two-dimension culture. We show that several commonly used breast cancer cell lines are amenable to this protocol. Furthermore, we provide proof-of-principle data utilizing the breast cancer cell line BT474, confirming their dependency on amplification of the epidermal growth factor receptor HER2 and mutation of phosphatidylinositol-4,5-biphosphate 3-kinase (PIK3CA) when grown as tumor spheroids. Finally, we are able to further investigate and confirm the spatial impact of these dependencies using immunohistochemistry.

Identifying novel drug targets that transition from pre-clinical testing to human trials is a scientific priority. To that end, here we describe a functional genomics approach for examining the impact of gene depletion on cancer cell line spheroids, which more appropriately model human cancers in vivo.

Utilizando Genómica Funcional de triagem para identificar alvos de drogas potencialmente romance em Spheroid culturas de células de câncer

The identification of functional driver events in cancer is central to furthering our understanding of cancer biology and indispensable for the discovery ...

Pesquisa do câncer

Time-lapse Imaging of Primary Preneoplastic Mammary Epithelial Cells Derived from Genetically Engineered Mouse Models of Breast Cancer

Time-lapse imaging can be used to compare behavior of cultured primary preneoplastic mammary epithelial cells derived from different genetically engineered mouse models of breast cancer. For example, time between cell divisions (cell lifetimes), apoptotic cell numbers, evolution of morphological changes, and mechanism of colony formation can be quantified and compared in cells carrying specific genetic lesions. Primary mammary epithelial cell cultures are generated from mammary glands without palpable tumor. Glands are carefully resected with clear separation from adjacent muscle, lymph nodes are removed, and single-cell suspensions of enriched mammary epithelial cells are generated by mincing mammary tissue followed by enzymatic dissociation and filtration. Single-cell suspensions are plated and placed directly under a microscope within an incubator chamber for live-cell imaging. Sixteen 650 &mu;m x 700 &mu;m fields in a 4x4 configuration from each well of a 6-well plate are imaged every 15 min for 5 days. Time-lapse images are examined directly to measure cellular behaviors that can include mechanism and frequency of cell colony formation within the first 24 hr of plating the cells (aggregation versus cell proliferation), incidence of apoptosis, and phasing of morphological changes. Single-cell tracking is used to generate cell fate maps for measurement of individual cell lifetimes and investigation of cell division patterns. Quantitative data are statistically analyzed to assess for significant differences in behavior correlated with specific genetic lesions.

Time-lapse imaging is used to assess behavior of primary preneoplastic mammary epithelial cells derived from genetically engineered mouse models of breast cancer risk to determine if there are correlations between specific behavioral parameters and distinct genetic lesions.

Lapso de tempo de imagem de pré-neoplásicas primárias células epiteliais mamárias derivados de modelos de rato geneticamente modificado do cancro da mama

Time-lapse  imaging can be used to compare behavior of cultured primary preneoplastic  mammary epithelial cells derived from different genetically ...

Medicina

Functional Assessment of BRCA1 variants using CRISPR-Mediated Base Editors

Recent studies have investigated the risks associated with BRCA1 gene mutations using various functional assessment methods such as fluorescent reporter assays, embryonic stem cell viability assays, and therapeutic drug-based sensitivity assays. Although they have clarified a lot of BRCA1 variants, these assays involving the use of exogenously expressed BRCA1 variants are associated with overexpression issues and cannot be applied to post-transcriptional regulation. To resolve these limitations, we previously reported a method for functional analysis of BRCA1 variants via CRISPR-mediated cytosine base editor that induce targeted nucleotide substitution in living cells. Using this method, we identified variants whose functions remain ambiguous, including c.-97C&#62;T, c.154C&#62;T, c.3847C&#62;T, c.5056C&#62;T, and c.4986+5G&#62;A, and confirmed that CRISPR-mediated base editors are useful tools for reclassifying the variants of uncertain significance in BRCA1. Here, we describe a protocol for functional analysis of BRCA1 variants using CRISPR-based cytosine base editor. This protocol provides guidelines for the selection of target sites, functional analysis and evaluation of BRCA1 variants.

Functional Assessment of BRCA1 variants using CRISPR-Mediated Base Editors

People with BRCA1 mutations have a higher risk of developing cancer, which warrants accurate evaluation of the function of BRCA1 variants. Herein, we described a protocol for functional assessment of BRCA1 variants using CRISPR-mediated cytosine base editors that enable targeted C:G to T:A conversion in living cells.

Avaliação funcional das variantes BRCA1 usando editores de base mediados pelo CRISPR

Recent studies have investigated the risks associated with BRCA1 gene mutations using various functional assessment methods such as fluorescent reporter ...

Isolation and Functional Assessment of Human Breast Cancer Stem Cells from Cell and Tissue Samples

Breast cancer stem cells (BCSCs) are cancer cells with inherited or acquired stem cell-like characteristics. Despite their low frequency, they are major contributors to breast cancer initiation, relapse, metastasis and therapy resistance. It is imperative to understand the biology of breast cancer stem cells in order to identify novel therapeutic targets to treat breast cancer. Breast cancer stem cells are isolated and characterized based on expression of unique cell surface markers such as CD44, CD24 and enzymatic activity of aldehyde dehydrogenase (ALDH). These ALDHhighCD44+CD24- cells constitute the BCSC population and can be isolated by fluorescence-activated cell sorting (FACS) for downstream functional studies. Depending on the scientific question, different in vitro and in vivo methods can be used to assess the functional characteristics of BCSCs. Here, we provide a detailed experimental protocol for isolation of human BCSCs from both heterogenous populations of breast cancer cells as well as primary tumor tissue obtained from breast cancer patients. In addition, we highlight downstream in vitro and in vivo functional assays including colony forming assays, mammosphere assays, 3D culture models and tumor xenograft assays that can be used to assess BCSC function.

This experimental protocol describes the isolation of BCSCs from breast cancer cell and tissue samples as well as the in vitro and in vivo assays that can be used to assess BCSC phenotype and function.

Isolamento e Avaliação Funcional de Células-Tronco de Câncer de Mama Humano de Amostras de Células e Tecidos

Breast cancer stem cells (BCSCs) are cancer cells with inherited or acquired stem cell-like characteristics. Despite their low frequency, they are major ...

Profiling of Estrogen-regulated MicroRNAs in Breast Cancer Cells

Estrogen plays vital roles in mammary gland development and breast cancer progression. It mediates its function by binding to and activating the estrogen receptors (ERs), ER&#945;, and ER&#946;. ER&#945; is frequently upregulated in breast cancer and drives the proliferation of breast cancer cells. The ERs function as transcription factors and regulate gene expression. Whereas ER&#945;&#39;s regulation of protein-coding genes is well established, its regulation of noncoding microRNA (miRNA) is less explored. miRNAs play a major role in the post-transcriptional regulation of genes, inhibiting their translation or degrading their mRNA. miRNAs can function as oncogenes or tumor suppressors&#160;and are also promising biomarkers. Among the miRNA assays available, microarray and quantitative real-time polymerase chain reaction (qPCR) have been extensively used to detect and quantify miRNA levels. To identify miRNAs regulated by estrogen signaling in breast cancer, their expression in ER&#945;-positive breast cancer cell lines were compared before and after estrogen-activation using both the &#181;Paraflo-microfluidic microarrays and Dual Labeled Probes-low density arrays. Results were validated using specific qPCR assays, applying both Cyanine dye-based and Dual Labeled Probes-based chemistry. Furthermore, a time-point assay was used to identify regulations over time. Advantages of the miRNA assay approach used in this study is that it enables a fast screening of mature miRNA regulations in numerous samples, even with limited sample amounts. The layout, including the specific conditions for cell culture and estrogen treatment, biological and technical replicates, and large-scale screening followed by in-depth confirmations using separate techniques, ensures a robust detection of miRNA regulations,&#160;and eliminates false positives and other artifacts. However, mutated or unknown miRNAs, or regulations at the primary and precursor transcript level, will not be detected. The method presented here represents a thorough investigation of estrogen-mediated miRNA regulation.

Molecular signaling through both estrogen and microRNAs are critical in breast cancer development and growth. Estrogen activates the estrogen receptors, which are transcription factors. Many transcription factors can regulate the expression of microRNAs, and estrogen-regulated microRNAs can be profiled using different large-scale techniques.

Profiling de MicroRNAs estrogênio regulados em células do cancro da mama

Estrogen plays vital roles in mammary gland development and breast cancer progression. It mediates its function by binding to and activating the estrogen ...

Evaluation of Stem Cell Properties in Human Ovarian Carcinoma Cells Using Multi and Single Cell-based Spheres Assays

Years of research indicates that ovarian cancers harbor a heterogeneous mixture of cells including a subpopulation of so-called &#8220;cancer stem cells&#8221; (CSCs) responsible for tumor initiation, maintenance and relapse following conventional chemotherapies. Identification of ovarian CSCs is therefore an important goal. A commonly used method to assess CSC potential in vitro is the spheres assay in which cells are plated under non-adherent culture conditions in serum-free medium supplemented with growth factors and sphere formation is scored after a few days. Here, we review currently available protocols for human ovarian cancer spheres assays and perform a side-by-side analysis between commonly used multi cell-based assays and a more accurate system based on single cell plating. Our results indicate that both multi cell-based as well as single cell-based spheres assays can be used to investigate sphere formation in vitro. The more laborious and expensive single cell-based assays are more suitable for functional assessment of individual cells and lead to overall more accurate results while multi cell-based assays can be strongly influenced by the density of plated cells and require titration experiments upfront. Methylcellulose supplementation to multi cell-based assays can be effectively used to reduce mechanical artifacts.

In vitro spheres assays are commonly used to identify cancer stem cells. Here we compare single with multi cell-based spheres assays. The more laborious single cell-based assays or methylcellulose supplementation give more accurate results while multi cell-based assays performed in liquid medium can be highly influenced by cell density.

Avaliação das Propriedades Stem Cell em carcinomas de células do ovário humano utilizar multi e individuais baseados em células Esferas Ensaios

Years of research indicates that ovarian cancers harbor a heterogeneous mixture of cells including a subpopulation of so-called &#8220;cancer stem ...

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo

Due to the high level of heterogeneity and mutations inherent in human cancers, single agent therapies, or combination regimens which target the same pathway, are likely to fail. Emphasis must be placed upon the inhibition of pathways that are responsible for intrinsic and/or adaptive resistance to therapy. An active field of investigation is the development and testing of DNA repair inhibitors that promote the action of, and prevent resistance to, commonly used chemotherapy and radiotherapy. We used a novel protocol to evaluate the effectiveness of BRCA2 inhibition as a means to sensitize tumor cells to the DNA damaging drug cisplatin. Tumor cell metabolism (acidification and respiration) was monitored in real-time for a period of 72 hr to delineate treatment effectiveness on a minute by minute basis. In combination, we performed an assessment of metastatic frequency using a chicken embryo chorioallantoic membrane (CAM) model of extravasation and invasion. This protocol addresses some of the weaknesses of commonly used in vitro and in vivo methods to evaluate novel cancer therapy regimens. It can be used in addition to common methods such as cell proliferation assays, cell death assays, and in vivo murine xenograft studies, to more closely discriminate amongst candidate targets and agents, and select only the most promising candidates for further development.

Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo

Here, real-time monitoring of tumor cell metabolism, combined with an in vivo chicken embryo chorio-allantoic membrane (CAM) model of metastasis, are used to evaluate novel anti-cancer targets/agents for their ability to sensitize tumor cells to DNA damaging chemotherapeutics.

Avaliar a eficácia do Cancer Drogas Sensibilização<em&gt; In Vitro</em&gt; E<em&gt; In Vivo</em

Due to the high level of heterogeneity and mutations inherent in human cancers, single agent therapies, or combination regimens which target the same ...

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1

The functional analysis of missense mutations can be complicated by the presence in the cell of the endogenous protein. Structure-function analyses of the BRCA1 have been complicated by the lack of a robust assay for the full length BRCA1 protein and the difficulties inherent in working with cell lines that express hypomorphic BRCA1 protein1,2,3,4,5. We developed a system whereby the endogenous BRCA1 protein in a cell was acutely depleted by RNAi targeting the 3'-UTR of the BRCA1 mRNA and replaced by co-transfecting a plasmid expressing a BRCA1 variant. One advantage of this procedure is that the acute silencing of BRCA1 and simultaneous replacement allow the cells to grow without secondary mutations or adaptations that might arise over time to compensate for the loss of BRCA1 function. This depletion and add-back procedure was done in a HeLa-derived cell line that was readily assayed for homologous recombination activity. The homologous recombination assay is based on a previously published method whereby a recombination substrate is integrated into the genome (Figure 1)6,7,8,9. This recombination substrate has the rare-cutting I-SceI restriction enzyme site inside an inactive GFP allele, and downstream is a second inactive GFP allele. Transfection of the plasmid that expresses I-SceI results in a double-stranded break, which may be repaired by homologous recombination, and if homologous recombination does repair the break it creates an active GFP allele that is readily scored by flow cytometry for GFP protein expression. Depletion of endogenous BRCA1 resulted in an 8-10-fold reduction in homologous recombination activity, and add-back of wild-type plasmid fully restored homologous recombination function. When specific point mutants of full length BRCA1 were expressed from co-transfected plasmids, the effect of the specific missense mutant could be scored. As an example, the expression of the BRCA1(M18T) protein, a variant of unknown clinical significance10, was expressed in these cells, it failed to restore BRCA1-dependent homologous recombination. By contrast, expression of another variant, also of unknown significance, BRCA1(I21V) fully restored BRCA1-dependent homologous recombination function. This strategy of testing the function of BRCA1 missense mutations has been applied to another biological system assaying for centrosome function (Kais et al, unpublished observations). Overall, this approach is suitable for the analysis of missense mutants in any gene that must be analyzed recessively.

We provide a method for testing BRCA1 variants in a tissue culture based assay for homologous recombination repair of DNA damage by depleting endogenous BRCA1 protein from a cell using RNAi and replacing it with a BRCA1 point mutant that contains a coding change.

Identificar os efeitos das mutações BRCA1 em Recombinação Homóloga usando células que expressam BRCA1 tipo selvagem endógena

The functional analysis of missense mutations can be complicated by the presence in the cell of the endogenous protein. Structure-function analyses of the ...

Biologia

Investigando a extensão das quebras de DNA que ocorrem durante a replicação do DNA 

Detection of DNA Breaks in Dividing Human Cells by Neutral Comet Assay

DNA replication is constantly challenged by a wide variety of endogenous and exogenous stressors that can damage DNA. Such lesions encountered during genome duplication can stall replisomes and convert replication forks into double-strand breaks. If left unrepaired, these toxic DNA breaks can trigger chromosomal rearrangements, leading to heightened genome instability and an increased likelihood of cellular transformation. Additionally, cancer cells exhibit persistent replication stress, making the targeting of replication fork vulnerabilities in tumor cells an attractive strategy for chemotherapy. A highly versatile and powerful technique to study DNA breaks during replication is the comet assay. This gel electrophoresis technique reliably detects the induction and repair of DNA breaks at the single-cell level. Herein, a protocol is outlined that allows investigators to measure the extent of DNA damage in mitotically dividing human cells using fork-stalling agents across multiple cell types. Coupling this with automated comet scoring facilitates rapid analysis and enhances the reliability in studying induction of DNA breaks.

Autor em destaque: Revelando o papel do SNF2L na estabilidade do garfo de replicação e duplicação do genoma

This protocol is designed to investigate the extent of DNA damage occurring during DNA replication. Under neutral conditions, the induction of DNA breaks can be readily assessed within a short time frame. Additionally, the protocol is adaptable to other cell types and various replication stress reagents.

Detecção de quebras de DNA em células humanas em divisão por ensaio de cometa neutro

DNA replication is constantly challenged by a wide variety of endogenous and exogenous stressors that can damage DNA. Such lesions encountered during ...

Silenciamento de

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