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. Preparare le soluzioni di siRNA <ol><li> Risospendere 5 nmol di strapazzate (Ctrl) e 5 nmol di BRCA2 siRNA pellet secchi in 100 ml di acqua RNase-free (concentrazione siRNA finale: 50 micron). Questo è lo stock siRNA e deve essere conservato a -20 ° C in 10 microlitri aliquote. </li><li> Prendete una aliquota di 10 ml dal magazzino siRNA e aggiungere 40 ml di acqua RNase-free per ottenere la soluzione di lavoro 10 micron siRNA. Questa diluizione deve essere conservata a -20 ° C fino al momento dell&#39;uso. NOTA: La soluzione di lavoro siRNA non deve essere sottoposto a congelamento / scongelamento più di 3 volte. </li></ol> 2. Semina di epiteliali umane linee cellulari <ol><li> Rimuovere il mezzo di crescita di linee cellulari epiteliali umane che crescono come monostrati di cellule in piastre di coltura di tessuti in un incubatore umidificato a 37 ° C, 5% CO 2. </li><li> Lavare le cellule nella piastra una volta con PBS RT (10 ml di PBS per una piastra di 100 mm). </li><li> Per staccare le cellule dalla piastra,aggiungere 2 ml di 0,25% tripsina / EDTA soluzione 0,53 mM e incubare 3-5 min a seconda del tipo di cellula. </li><li> Prima di raccogliere le cellule staccate, neutralizzare tripsina aggiungendo 2 ml di terreno di coltura completo contenente siero bovino fetale al 10%. </li><li> Trasferire le cellule in una provetta da 15 ml. </li><li> Centrifugare le cellule a 320-330 xg per 3 min a 4 ° C in un rotore oscillante secchio. </li><li> Risospendere il pellet di cellule in 5 ml di free-antibiotici medie. </li><li> Contare le cellule sotto il microscopio in una camera di Burker o utilizzando un sistema di conteggio automatico secondo le istruzioni del produttore. </li><li> Seed le cellule in 6 pozzetti per essere circa l&#39;80% confluenti dopo 24 ore (0,5-1 x10 6 celle in 2 ml di terreno per ogni bene). Numero ottimale di cellule per essere seminati possono variare a seconda delle linee cellulari specifiche e il tasso di crescita. NOTA: Non aggiungere antibiotici nel mezzo a questo punto, perché gli antibiotici interferiscono negativamente con l&#39;efficienza di trasferction. È molto importante che le cellule sono a passaggi su coltura basse (&lt;10) per ottenere un&#39;elevata efficienza di BRCA2 siRNA trasfezione. </li></ol> 3. Le cellule trasfezione con siRNA <ol><li> Ventiquattro ore dopo la placcatura le cellule, procedere con il primo turno di trasfezione. <ol><li> Diluire 6 ml di base lipidica 10 siRNA specifico reagente di trasfezione in 130 ml di mezzo di siero ridotto. </li><li> Diluire 3 ml di 10 micron siRNA (30 pmol) in 130 ml di mezzo di siero ridotto. </li><li> Unire il siRNA diluito con il reagente di trasfezione diluito e incubare per 5-10 minuti a temperatura ambiente. </li><li> Durante l&#39;incubazione, rimuovere il terreno dalle cellule e aggiungere 2 ml di mezzo fresco pre-riscaldato a 37 ° C (senza antibiotici). </li><li> Aggiungere 250 l di siRNA-trasfezione complessi reagenti alle cellule (l&#39;importo è per un singolo pozzo di un 6-pozzetti). </li><li> Incubare le cellule in un incubatore umidificato a 3776; C con 5% di CO 2. </li></ol></li><li> Dopo 24 ore, procedere con il secondo turno di trasfezione ripetendo i punti 3.1.1-3.1.5 con la seguente modifica di passo 3.1.2: diluire 5 ml di 10 micron siRNA (50 pmoli) in 130 ml di mezzo di siero ridotto. <ol><li> Incubare le cellule per 1-2 giorni a 37 ° C prima dell&#39;analisi. NOTA: Due turni di trasfezioni e l&#39;uso di un rapporto di reagenti alto siRNA / trasfezione al secondo turno sono essenziali per ottenere un&#39;elevata efficienza di silenziamento BRCA2. </li></ol></li></ol> 4. cellule Lisare per l&#39;analisi immunoblotting <ol><li> Preparare tampone di lisi fresca con PBS (pH 7.4) contenente 1% di non ionico, non denaturante detergente ottilfenossipolietossietanolo, 5 mM sodio pirofosfato, 1 mM orthovanadate di sodio, fluoruro di sodio 10 mM, fluoruro phenylmethylsulfonyl 2 mM, 10 mg / ml leupeptina, 10 ug / ml aprotinina. Keep it sul ghiaccio. </li><li> Rimuovere il supporto da parte delle cellule e wcenere una volta con PBS freddo (2 ml / pozzetto) nella piastra. Per evitare qualsiasi riporto PBS, rimuoverlo completamente dalla piastra. </li><li> Aggiungere 200 ml di tampone di lisi a ciascun pozzetto. NOTA: Se le cellule devono essere utilizzati anche per altri saggi, trypsinize le cellule come descritto al punto 2.1-2.6 e risospendere le cellule in appropriato tampone / supporto secondo l&#39;applicazione da usare. </li><li> Ruotare delicatamente la piastra per distribuire uniformemente il tampone di lisi e incubare per 15 min a 4 ° C su un rotatore. </li><li> Raccogliere il lisato cellulare in una provetta su ghiaccio con un raschietto cellulare. </li><li> Centrifugare a 17.900 xg per 25 min a 4 ° C e raccogliere il surnatante in una nuova provetta. </li><li> Misurare la concentrazione proteica utilizzando un saggio proteico disponibile in commercio secondo le istruzioni del produttore. </li></ol> 5. BRCA2 analisi immunoblotting <ol><li> Preparare il tampone di corsa diluendo 50 ml di 20x Tris-acetato SDS esecuzione bUffer (Tricine 50 mM, 50 mM Tris Base, 0,1% SDS, pH 8.24) con 950 ml di acqua distillata. </li><li> Preparare il campione come segue: aggiungere 15 ug di lisato cellulare totale, 5 ml di tampone campione 4x contenenti litio dodecil solfato a pH 8,4, 2 ml di agente riducente 10x campione (0.5 M DTT), e tampone di lisi a un volume finale di 20 ul. NOTA: Questo protocollo consente il rilevamento di BRCA2 in linee cellulari normali anche quando si utilizza una minore quantità di proteine ​​totali (fino a 5 mg). </li><li> Denaturare i campioni a 55 ° C per 10 min. NOTA: E &#39;fondamentale utilizzare 55 ° C. Dal momento che la proteina BRCA2 è termosensibile 11, le temperature più elevate denaturanti provocano la perdita costante di intatta tutta lunghezza (390 kDa) proteina BRCA2. </li><li> Impostare la camera elettroforetico secondo le istruzioni del produttore. </li><li> Caricare i campioni e 10 ml di alto peso molecolare pre-tinto standard di proteine ​​su un gel precasted (Tris-acetato 3-8%) e correre a 120 V per abfuori 2 ore 12. Fermare la corsa elettroforetica prima del 55 kDa indicatore blu lascia il gel precasted. </li><li> Preparare il buffer di trasferimento con 50 ml di 20x tampone di trasferimento, 100 ml di metanolo 100% e 850 ml di acqua. </li><li> Attiva membrana PVDF (0,45 micron dimensione dei pori) immergendolo in metanolo 100% per 5 minuti, risciacquare con acqua distillata ed equilibrare in tampone di trasferimento almeno per 5 min. Immergere le spugne del dispositivo di trasferimento in tampone di trasferimento a 4 ° C fino al momento dell&#39;uso. </li><li> Quando la corsa elettroforetica è finita, montare il sandwich nella pila di trasferimento nel seguente ordine (bottom-up): tre spugne saturi nel buffer di trasferimento, un foglio di carta 3MM grado saturo in buffer di trasferimento, il gel, membrane PVDF attivato, uno 3MM foglio di carta di grado saturi in buffer di trasferimento, tre spugne saturo in buffer di trasferimento 13,14. Posizionare la pila nelle proteine ​​apparecchi e di trasferimento a 350 mA per 4 ore a 4 ° C o 180 mA notte a 4 ° C. NOTA: Essendo BRCA2 una grande proteina, è fondamentale per estendere il tempo di trasferimento da 1 hr (come suggerito dal produttore e la maggior parte dei protocolli di trasferimento) per 4 ore o durante la notte per garantire la completa trasferimento di proteine ​​ad alto peso molecolare. In aggiunta, a causa del tempo di trasferimento lungo, è indispensabile effettuare il blotting in una camera fredda a 4 ° C per ridurre al minimo il surriscaldamento e facilitare smontaggio sandwich. Sistemi di trasferimento semi-dry non sono buone per il trasferimento di grandi proteine. </li><li> Dopo il trasferimento, lavare la membrana con TBS, bloccarlo per 1 ora a RT in TBS-Tween 0,25% (TBS-T) contenente latte in polvere 5% nonfat e sonda notte a 4 ° C con 30 microlitri anti-BRCA2 anticorpo policlonale di coniglio ( 200 mcg / ml), diluito in 9 ml TBS-T + 5% latte scremato secca [1: 300 (v / v)] diluizione. </li><li> Lavare la membrana tre volte (10 min ciascuno) con TBS-T, allora il filtro incubare per 1 ora con 1 ml di rafano anti-coniglio anticorpo secondario coniugato con perossidasi diluito in 10 ml di TBS-T + 5% senza grassi latte in polvere. Successivamente, lavare la membrana per tre volte (10 min ciascuno) con TBS-T. </li><li> Eseguire immunolocalizzazione di ECL per rivelare la proteina BRCA2 con chemiluminescenza (ECL) Western Blotting Detection Reagent, seguendo le istruzioni del produttore. Visualizza bande immunochemiluminescenti ad alta risoluzione su pellicole ECL. </li><li> Eseguire immunolocalizzazione con un anticorpo per un gene housekeeping, come β-tubulina (55 kDa), sullo stesso filtro come controllo di caricamento utilizzando un anticorpo monoclonale di β-tubulina diluito a 1: 1.000 (10 ml di anticorpo anti-tubulina in 10 ml TBS-T latte in polvere senza grassi + 5%) per 1 ora a temperatura ambiente. Lavare e incubare anticorpo secondario come descritto per BRCA2 (5,10-5,11), fatta eccezione per l&#39;utilizzo di perossidasi di rafano-coniugato anti-mouse invece di anticorpo secondario anti-coniglio. </li><li> Acquisire un&#39;immagine digitale dei film impressi con bande immunochemiluminescenti e analizzare l&#39;intensità della banda da immagine dedicato software di analisi (per esempio., ImageJ). </li></ol>

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The authors have nothing to disclose.

A causa mutazioni germinali del gene BRCA2 piombo ad un aumentato rischio di diversi tipi di cancro, tra cui il cancro al seno maschile e femminile, il cancro ovarico, il cancro alla prostata, cancro al pancreas, e il melanoma 3,4, sono state avviate una serie di studi per comprendere la funzione biologica della proteina BRCA2. La maggior parte di questi studi sono genetiche a base principalmente a causa di difficoltà tecniche analizzando una proteina gigante come BRCA2. Il metodo descritto qui di s...

Il BRCA2 (Breast Cancer suscettibilità gene-2) gene codifica per una proteina soppressore del tumore che gioca un ruolo cruciale nella riparazione del DNA rotture del doppio filamento regolando la funzione dell&#39;enzima recombinase Rad51 1. BRCA2 è stato anche coinvolto nella modulazione della trascrizione e nel controllo del ciclo cellulare 2. Mutazioni germinali nel gene BRCA2 inducono un autosomica dominante suscettibilità cancro al seno e alle ovaie nelle donne e il cancro alla prostata negli uomini, nonché la predisposizione di altri tipi di cancro 3,4. Tuttavia, nonostante l&#39;aumento del rischio di sviluppare il cancro, mutazioni BRCA2 che sopprimono o riducono la funzionalità BRCA2 possono rendere le cellule tumorali più vulnerabili agli agenti chemioterapici che causano danni al DNA 5-7. Tumori sporadici presentano un basso tasso di mutazioni BRCA2 (&lt;3%) anche se sono stati rilevati livelli ridotti di proteina BRCA2 in alcuni tipi di cancro, suggerendo che la proteina BRCA2può essere perso durante la tumorigenesi nei tumori sporadici attraverso meccanismi non mutazionale dipendenti 7,8. Pertanto, è importante comprendere appieno funzioni BRCA2 nel contesto della biologia cancro e in altri contesti biologici. Uno strumento potente usato per identificare nuove funzioni di un gene in cellule di mammifero è di mettere a tacere la sua espressione. Come esempio, il silenziamento dell&#39;espressione BRCA2 in una varietà di cellule epiteliali normali ha recentemente portato all&#39;identificazione di una nuova funzione di BRCA2 come regolatore di anoikis resistenza, un passo importante durante l&#39;acquisizione di cellule di cancro invasivo e metastatico capacità 9. Gene silenziamento può essere raggiunto con l&#39;introduzione nelle cellule o small interfering (si) RNA o brevi tornanti (sh) molecole di RNA rivolti al gene specifico. L&#39;elevata potenza di siRNA e la sua facilità d&#39;uso ne fanno lo strumento preferenziale per tacere esperimenti volti ad acquisire nuove conoscenze sui processi biologici critici unnd di identificare nuovi bersagli terapeutici. Tuttavia, l&#39;abbattimento efficiente di espressione genica può non essere facilmente raggiungibile per tutti i geni e può essere molto variabile a seconda del tipo di cellula. Poiché una diminuzione dei livelli di proteine ​​intracellulari è il fenotipo più rilevante in esame, è fondamentale quantificare silenziamento genico mediante immunoblotting analisi del prodotto del gene. Con questo proposito, la proteina BRCA2 presenta un&#39;ulteriore sfida: essere una grande proteina (circa 390 kDa), esistono difficoltà tecniche per l&#39;analisi biochimica convenzionale, compresi immunoblotting. Riportiamo qui un protocollo ottimizzato per tacere efficiente di BRCA2 in linee cellulari epiteliali umane e per la rilevazione rapida e positiva di proteine ​​BRCA2 knockdown mediante immunoblotting analisi.

<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

Silenziamento della proteina BRCA2 soppressore del tumore e la sua individuazione da analisi biochimiche convenzionali rappresentano una grande sfida tecnica a causa delle grandi dimensioni della proteina BRCA2 umana (circa 390 kDa). Riportiamo modifiche di protocolli di trasfezione e immunoblotting siRNA standard per tacere BRCA2 umano e rilevare proteina BRCA2 endogena, rispettivamente, nelle linee di cellule epiteliali umane. Passaggi chiave includono un alto siRNA rapporto reagente di trasfezione e due successivi turni di siRNA trasfezione all&#39;interno dello stesso esperimento. Utilizzando queste e altre modifiche al protocollo standard che costantemente raggiungere oltre il 70% silenziamento del gene BRCA2 umano come giudicato da immunoblotting con anticorpi anti-BRCA2. Inoltre, denaturazione dei lisati cellulari a 55 ° C invece che nel tradizionale 70-100 ° C e altre ottimizzazioni tecniche della procedura immunoblotting consentono di individuare proteina BRCA2 intatta anche when molto basse quantità di materiale di partenza sono disponibili o quando i livelli di espressione della proteina BRCA2 sono molto basse. Silenziamento efficiente di BRCA2 nelle cellule umane offre una valida strategia per interrompere la funzione BRCA2 in cellule con BRCA2 intatte, comprese le cellule tumorali, per esaminare nuovi percorsi molecolari e funzioni cellulari che possono essere interessati da mutazioni BRCA2 patogeni nei tumori. L&#39;adattamento di questo protocollo per tacere e l&#39;analisi di altre proteine ​​&quot;grandi&quot; come BRCA2 efficiente dovrebbe essere facilmente realizzabile.

Prima di procedere con un saggio biologico / biochimico per esaminare l&#39;effetto di silenziamento BRCA2 sulle funzioni cellulari, il primo passo è per confermare la specificità del silenziamento utilizzando un siRNA criptato (non-targeting siRNA) fianco a fianco con BRCA2 siRNA (Figura 1A ). E &#39;importante eseguire una seconda tornata di siRNA trasfezione con un elevato rapporto siRNA / trasfezione per ottenere un&#39;elevata efficienza di silenziamento BRCA2. In effetti, l&#39...

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.

Silencing di<em&gt; BRCA2</em&gt; Per identificare le funzioni biologiche Novel BRCA2-regolamentato coltivate cellule umane

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

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Research

JoVE Journal

Biology

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

9.0K Views.  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. 

Video: 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.

Utilizzando Genomica Funzionale screening per identificare gli obiettivi farmaco potenzialmente romanzo in Cancer Cell Culture Spheroid

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

Ricerca

Ricerca sul cancro

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.

Valutazione funzionale delle varianti BRCA1 utilizzando editor di base mediati da 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 valutazione funzionale di cellule staminali di cancro al seno umano da campioni di cellule e tessuti

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 di microRNA regolati dagli estrogeni in cellule di carcinoma mammario

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

Medicina

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.

Valutare l&#39;efficacia delle Cancer Drug Sensibilizzazione<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.

Identificare gli effetti delle mutazioni BRCA1 sulla ricombinazione omologa utilizzando cellule che esprimono endogeno 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 ...

Biologia

In Vitro Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing

Gene inactivation is instrumental to study gene function and represents a promising strategy for the treatment of a broad range of diseases. Among traditional technologies, RNA interference suffers from partial target abrogation and the requirement for life-long treatments. In contrast, artificial nucleases can impose stable gene inactivation through induction of a DNA double strand break (DSB), but recent studies are questioning the safety of this approach. Targeted epigenetic editing via engineered transcriptional repressors (ETRs) may represent a solution, as a single administration of specific ETR combinations can lead to durable silencing without inducing DNA breaks.
ETRs are proteins containing a programmable DNA-binding domain (DBD) and effectors from naturally occurring transcriptional repressors. Specifically, a combination of three ETRs equipped with the KRAB domain of human ZNF10, the catalytic domain of human DNMT3A and human DNMT3L, was shown to induce heritable repressive epigenetic states on the ETR-target gene. The hit-and-run nature of this platform, the lack of impact on the DNA sequence of the target, and the possibility to revert to the repressive state by DNA demethylation on demand, make epigenetic silencing a game-changing tool. A critical step is the identification of the proper ETRs&#39; position on the target gene to maximize on-target and minimize off-target silencing. Performing this step in the final ex vivo or in vivo preclinical setting can be cumbersome.
Taking the CRISPR/catalytically dead Cas9 system as a paradigmatic DBD for ETRs, this paper describes a protocol consisting of the in vitro screen of guide RNAs (gRNAs) coupled to the triple-ETR combination for efficient on-target silencing, followed by evaluation of the genome-wide specificity profile of top hits. This allows for reduction of the initial repertoire of candidate gRNAs to a short list of promising ones, whose complexity is suitable for their final&#160;evaluation in the therapeutically relevant setting of interest.

In Vitro Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing

Here, we present a protocol for the in vitro selection of engineered transcriptional repressors (ETRs) with high, long-term, stable, on-target silencing efficiency and low genome-wide, off-target activity. This workflow allows for reducing an initial, complex repertoire of candidate ETRs to a short list, suitable for further evaluation in therapeutically relevant settings.

In vitro Selezione di repressori trascrizionali ingegnerizzati per il silenziamento epigenetico mirato

Gene inactivation is instrumental to study gene function and represents a promising strategy for the treatment of a broad range of diseases. Among ...

Bioingegneria

siRNA Screening to Identify Ubiquitin and Ubiquitin-like System Regulators of Biological Pathways in Cultured Mammalian Cells

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that regulates diverse biological pathways including the hypoxia response, proteostasis, the DNA damage response and transcription.&#160; To better understand how UBLs regulate pathways relevant to human disease, we have compiled a human siRNA &#8220;ubiquitome&#8221; library consisting of 1,186 siRNA duplex pools targeting all known and predicted components of UBL system pathways. This library can be screened against a range of cell lines expressing reporters of diverse biological pathways to determine which UBL components act as positive or negative regulators of the pathway in question.&#160; Here, we describe a protocol utilizing this library to identify ubiquitome-regulators of the HIF1A-mediated cellular response to hypoxia using a transcription-based luciferase reporter.&#160; An initial assay development stage is performed to establish suitable screening parameters of the cell line before performing the screen in three stages: primary, secondary and tertiary/deconvolution screening. &#160;The use of targeted over whole genome siRNA libraries is becoming increasingly popular as it offers the advantage of reporting only on members of the pathway with which the investigators are most interested.&#160; Despite inherent limitations of siRNA screening, in particular false-positives caused by siRNA off-target effects, the identification of genuine novel regulators of the pathways in question outweigh these shortcomings, which can be overcome by performing a series of carefully undertaken control experiments.

Here, we describe a methodology to perform a targeted siRNA &#8220;ubiquitome&#8221; screen to identify novel ubiquitin and ubiquitin-like regulators of the HIF1A-mediated cellular response to hypoxia.&#160; This can be adapted to any biological pathway where a robust read out of reporter activity is available.

siRNA screening per identificare ubiquitina e ubiquitina-come regolatori del sistema di percorsi biologici in cellule di mammifero coltivate

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that ...

gDNA Enrichment by a Transposase-based Technology for NGS Analysis of the Whole Sequence of BRCA1, BRCA2, and 9 Genes Involved in DNA Damage Repair

The widespread use of Next Generation Sequencing has opened up new avenues for cancer research and diagnosis. NGS will bring huge amounts of new data on cancer, and especially cancer genetics. Current knowledge and future discoveries will make it necessary to study a huge number of genes that could be involved in a genetic predisposition to cancer. In this regard, we developed a Nextera design to study 11 complete genes involved in DNA damage repair. This protocol was developed to safely study 11 genes (ATM, BARD1, BRCA1, BRCA2, BRIP1, CHEK2, PALB2, RAD50, RAD51C, RAD80, and TP53) from promoter to 3&#39;-UTR in 24 patients simultaneously. This protocol, based on transposase technology and gDNA enrichment, gives a great advantage in terms of time for the genetic diagnosis thanks to sample multiplexing. This protocol can be safely used with blood gDNA.

gDNA Enrichment by a Transposase-based Technology for NGS Analysis of the Whole Sequence of BRCA1, BRCA2, and 9 Genes Involved in DNA Damage Repair

gDNA enrichment for NGS sequencing is an easy and powerful tool for the study of constitutional mutations. In this article, we present the procedure to analyse simply the complete sequence of 11 genes involved in DNA damage repair.

gDNA arricchimento da una tecnologia basata trasposasi-NGS per l&#39;analisi della sequenza intera<em&gt; BRCA1</em&gt;,<em&gt; BRCA2</em&gt;, e 9 geni coinvolti nella riparazione del DNA Damage

The widespread use of Next Generation Sequencing has opened up new avenues for cancer research and diagnosis. NGS will bring huge amounts of new data on ...

Visualization of DNA Repair Proteins Interaction by Immunofluorescence

Mammalian cells are constantly exposed to chemicals, radiations, and naturally occurring metabolic by-products, which create specific types of DNA insults. Genotoxic agents can damage the DNA backbone, break it, or modify the chemical nature of individual bases. Following DNA insult, DNA damage response (DDR) pathways are activated and proteins involved in the repair are recruited. A plethora of factors are involved in sensing the type of damage and activating the appropriate repair response. Failure to correctly activate and recruit DDR factors can lead to genomic instability, which underlies many human pathologies including cancer. Studies of DDR proteins can provide insights into genotoxic drug response and cellular mechanisms of drug resistance.
There are two major ways of visualizing&#160;proteins in vivo: direct observation, by tagging the protein of interest with a fluorescent protein and following it by live imaging, or indirect immunofluorescence on fixed samples. While visualization of fluorescently tagged proteins allows precise monitoring over time, direct tagging in N- or C-terminus can interfere with the protein localization or function. Observation of proteins in their unmodified, endogenous version is preferred. When DNA repair proteins are recruited to the DNA insult, their concentration increases locally and they form groups, or &#8220;foci&#8221;, that can be visualized by indirect immunofluorescence using specific antibodies.
Although detection of protein foci does not provide a definitive proof of direct interaction, co-localization of proteins in cells indicates that they regroup to the site of damage and can inform of the sequence of events required for complex formation. Careful analysis of foci spatial overlap in cells expressing wild type or mutant versions of a protein can provide precious clues on functional domains important for DNA repair function. Last, co-localization of proteins indicates possible direct interactions that can be verified by co-immunoprecipitation in cells, or direct pulldown using purified proteins.

Following DNA damage, human cells activate essential repair pathways to restore the integrity of their genome. Here, we describe the method of indirect immunofluorescence as a means to detect DNA repair proteins, analyze their spatial and temporal recruitment, and help interrogate protein-protein interaction at the sites of DNA damage.

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