This work has been partially supported by NIH R01CA187780.

NOTE: Astroglial and neuronal lentivirus reporter systems were purchased as pre-packaged, concentrated lentiviral preparations. Basic knowledge of flow cytometry technique is required. Also, for a full use of this protocol the user will need access to a flow cytometer with high throughput capacity (accepts 96-well plates as sample source).
1. Lentiviral Transcriptional Reporter System
NOTE: In all flow cytometric analyses, use parental, non-transduced, cells or vector...

<ol>
	<li>Maher, E. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Malignant+glioma:+genetics+and+biology+of+a+grave+matter.">Malignant glioma: genetics and biology of a grave matter.</a> Genes Dev. 15 (11), 1311-1333 (2001).</li><li>Bonavia, R., Inda, M. M., Cavenee, W. K., Furnari, F. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterogeneity+maintenance+in+glioblastoma:+a+social+network.">Heterogeneity maintenance in glioblastoma: a social network.</a> Cancer Res. 71 (12), 4055-4060 (2011).</li><li>Bao, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glioma+stem+cells+promote+radioresistance+by+preferential+activation+of+the+DNA+damage+response.">Glioma stem cells promote radioresistance by preferential activation of the DNA damage response.</a> Nature. 444 (7120), 756-760 (2006).</li><li>Sul, J., Fine, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Malignant+gliomas:+new+translational+therapies.">Malignant gliomas: new translational therapies.</a> Mt Sinai J Med. 77 (6), 655-666 (2010).</li><li>Bar, E. E., Chaudhry, A., Farah, M. H., Eberhart, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hedgehog+signaling+promotes+medulloblastoma+survival+via+Bc/II.">Hedgehog signaling promotes medulloblastoma survival via Bc/II.</a> Am J Pathol. 170 (1), 347-355 (2007).</li><li>Chu, Q., Orr, B. A., Semenkow, S., Bar, E. E., Eberhart, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prolonged+inhibition+of+glioblastoma+xenograft+initiation+and+clonogenic+growth+following+in+vivo+Notch+blockade.">Prolonged inhibition of glioblastoma xenograft initiation and clonogenic growth following in vivo Notch blockade.</a> Clin Cancer Res. 19 (12), 3224-3233 (2013).</li><li>Schreck, K. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Notch+target+Hes1+directly+modulates+Gli1+expression+and+Hedgehog+signaling:+a+potential+mechanism+of+therapeutic+resistance.">The Notch target Hes1 directly modulates Gli1 expression and Hedgehog signaling: a potential mechanism of therapeutic resistance.</a> Clin Cancer Res. 16 (24), 6060-6070 (2010).</li><li>Warrell, R. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+therapy+of+acute+promyelocytic+leukemia+with+tretinoin+(all-trans-retinoic+acid).">Differentiation therapy of acute promyelocytic leukemia with tretinoin (all-trans-retinoic acid).</a> N Engl J Med. 324 (20), 1385-1393 (1991).</li><li>Piccirillo, S. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+proteins+inhibit+the+tumorigenic+potential+of+human+brain+tumour-initiating+cells.">Bone morphogenetic proteins inhibit the tumorigenic potential of human brain tumour-initiating cells.</a> Nature. 444 (7120), 761-765 (2006).</li><li>Bar, E. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclopamine-mediated+hedgehog+pathway+inhibition+depletes+stem-like+cancer+cells+in+glioblastoma.">Cyclopamine-mediated hedgehog pathway inhibition depletes stem-like cancer cells in glioblastoma.</a> Stem Cells. 25 (10), 2524-2533 (2007).</li><li>Bar, E. E., Lin, A., Mahairaki, V., Matsui, W., Eberhart, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hypoxia+increases+the+expression+of+stem-cell+markers+and+promotes+clonogenicity+in+glioblastoma+neurospheres.">Hypoxia increases the expression of stem-cell markers and promotes clonogenicity in glioblastoma neurospheres.</a> Am J Pathol. 177 (3), 1491-1502 (2010).</li><li>Kahlert, U. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD133/CD15+defines+distinct+cell+subpopulations+with+differential+in+vitro+clonogenic+activity+and+stem+cell-related+gene+expression+profile+in+in+vitro+propagated+glioblastoma+multiforme-derived+cell+line+with+a+PNET-like+component.">CD133/CD15 defines distinct cell subpopulations with differential in vitro clonogenic activity and stem cell-related gene expression profile in in vitro propagated glioblastoma multiforme-derived cell line with a PNET-like component.</a> Folia Neuropathol. 50 (4), 357-368 (2012).</li><li>Lim, K. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+monocarboxylate+transporter-4+depletes+stem-like+glioblastoma+cells+and+inhibits+HIF+transcriptional+response+in+a+lactate-independent+manner.">Inhibition of monocarboxylate transporter-4 depletes stem-like glioblastoma cells and inhibits HIF transcriptional response in a lactate-independent manner.</a> Oncogene. 33 (35), 4433-4441 (2014).</li><li>Kahlert, U. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ZEB1+Promotes+Invasion+in+Human+Fetal+Neural+Stem+Cells+and+Hypoxic+Glioma+Neurospheres.">ZEB1 Promotes Invasion in Human Fetal Neural Stem Cells and Hypoxic Glioma Neurospheres.</a> Brain Pathol. 25 (6), 724-732 (2014).</li><li>Hu, Y., Smyth, G. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ELDA:+extreme+limiting+dilution+analysis+for+comparing+depleted+and+enriched+populations+in+stem+cell+and+other+assays.">ELDA: extreme limiting dilution analysis for comparing depleted and enriched populations in stem cell and other assays.</a> J Immunol Methods. 347 (1-2), 70-78 (2009).</li><li>Meyer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+cell-derived+clonal+analysis+of+human+glioblastoma+links+functional+and+genomic+heterogeneity.">Single cell-derived clonal analysis of human glioblastoma links functional and genomic heterogeneity.</a> Proc Natl Acad Sci U S A. 112 (3), 851-856 (2015).</li><li>Galli, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+tumorigenic,+stem-like+neural+precursors+from+human+glioblastoma.">Isolation and characterization of tumorigenic, stem-like neural precursors from human glioblastoma.</a> Cancer Res. 64 (19), 7011-7021 (2004).</li><li>Spina, R., Voss, D. M., Asnaghi, L., Sloan, A., Bar, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atracurium+Besylate+and+other+neuromuscular+blocking+agents+promote+astroglial+differentiation+and+deplete+glioblastoma+stem+cells.">Atracurium Besylate and other neuromuscular blocking agents promote astroglial differentiation and deplete glioblastoma stem cells.</a> Oncotarget. 7 (1), 459-472 (2016).</li></ol>

While most of the previous studies of GSCs focused primarily on the markers that define them, in this study we decided to take the reverse approach. We focus primarily on the differentiated progenies generated by GSCs (e.g., cells expressing astroglial and neuronal markers). Here we demonstrate the utilization of a cell-based high throughput drug screening system, which is based on human GFAP promoter-dependent expression of GFP. All the experiments were performed utilizing patient-derived neurosphere glioblastoma cell l...

Recent studies have shown that tumors contain a small population of cells, termed cancer stem cells (CSCs) or tumor-initiating cells, which are responsible for tumor progression, metastasis, and resistance to chemo- and radio-therapies 1,2. The presence of cancer stem cells and their more differentiated progenies within tumors is considered an important factor promoting intratumoral heterogeneity and thus represents a major hurdle in treating cancers3. Tumor cell hierarchy, provided by the cancer stem cell theory, has inspired the development of new strategies to treat cancers 4. One approach for targeting cancer stem cells is to identify and inhibit signaling pathways that are known to be required during embryonic development of the affected organ. Indeed, we and others have previously published multiple papers describing the ongoing requirement for the neural stem cell-relevant signaling pathways Sonic Hedgehog and Notch in glioblastoma5,6,7. This work has helped in solidifying the rationale for several GBM clinical trials. A second approach for targeting cancer stem cells is to promote their differentiation. This approach has received a lot of support due to the favorable results from preclinical and clinical studies in treating acute promyelocytic leukemia with retinoic acids (ATRA, a vitamin-A analog). Here ATRA was found to remove the maturation block and promote cancer cell differentiation8. More recently, Piccirillo and colleagues have elegantly shown that BMP-4 promotes GSC differentiation into astrocytes with significant anti-GBM effects in vitro and in vivo9.
The rationale for the current study is based on a &#34;reversed engineering&#34; approach for targeting GSCs. Given the vast heterogeneity present in GBM and with poor differentiation being one of the hallmarks of cancer, we asked if we could promote a more favorable phenotype - differentiation into an astrocyte-like state. Here, we do not have prior knowledge of the signaling pathways that maintain GSCs in a given tumor specimen but rather aim to achieve a desired phenotype (e.g. GFAP positivity).
This report describes the procedures used to establish GSC differentiation reporter-lines from the transduction of GSC-enriched cultures to GSC clonal selection. The glioblastoma neurosphere lines used were established at the laboratory of Professor Angelo Vescovi from patients with a diagnosis of primary glioblastoma at Hospital San Raffaele - Milano, Italy. These lines have been extensively studied in several publications 6,10,11,12,13,14. It is highly recommended that individuals who are interested in implementing these techniques in their laboratory determine the relevance of the reporter to cancer stem cell self-renewal capacity in the cells they plan to study (this is true for any reporter). A detailed protocol for one of the in vitro clonogenic assays accepted in the field is provided to accomplish this15,16. Finally, a detailed protocol describing the utilization of the differentiation reporter-lines in a flow-cytometry based drug screen is provided at the end. Of note, similarly to the astroglial differentiation system described here, we have successfully established and validated GSC reporter lines integrating an MAP2:GFP (neuronal differentiation) reporter. Therefore, the methodologies describe in this paper may be applied to study cellular differentiation into various cell lineages.
Some of the figures in this report can be found in a recent publication: &#34;Atracurium Besylate and other neuromuscular blocking agents promote astroglial differentiation and deplete glioblastoma stem cells18.

<table>
	<tbody>
		<tr>
			<td>ESGRO Complete Accutase</td>
			<td>EMD Millipore</td>
			<td>SF006</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl Sulfoxide (DMSO)</td>
			<td>Sigma Aldrich</td>
			<td>D2650</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS (Hank&#39;s Balanced Salt Solution)</td>
			<td>Sigma Aldrich</td>
			<td>H6648</td>
			<td></td>
		</tr>
		<tr>
			<td>Human GFAP Differentiation Reporter (pGreenZeo, Virus)</td>
			<td>SBI (System Biosciences)</td>
			<td>SR10015VA-1</td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml sterile disposable reagent reservoirs</td>
			<td>Corning</td>
			<td>4870</td>
			<td></td>
		</tr>
		<tr>
			<td>6 well plate</td>
			<td>Thermo Fisher Scientific</td>
			<td>130184</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well plate</td>
			<td>Falcon</td>
			<td>353072</td>
			<td></td>
		</tr>
		<tr>
			<td>Biolite T25 cm&#178; Flask Vented</td>
			<td>Thermo Fisher Scientific</td>
			<td>130189</td>
			<td></td>
		</tr>
		<tr>
			<td>Biolite T75 cm&#178; Flask Vented</td>
			<td>Thermo Fisher Scientific</td>
			<td>130190</td>
			<td></td>
		</tr>
		<tr>
			<td>15 ml Centrifuge tubes</td>
			<td>Celltreat</td>
			<td>229411</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5ml Microcentrifuge tubes</td>
			<td>Fisher Scientific</td>
			<td>05-408-129</td>
			<td></td>
		</tr>
		<tr>
			<td>Ovation Multi Channel Pipette, 12 Channel, 0.5 - 20uL</td>
			<td>VistaLab Technologies</td>
			<td>1060-0020</td>
			<td></td>
		</tr>
		<tr>
			<td>Ovation Multi Channel Pipette, 12 Channel, 5-250uL</td>
			<td>VistaLab Technologies</td>
			<td>1060-0250</td>
			<td></td>
		</tr>
		<tr>
			<td>Multi 12-channel pipette tips 25 &#956;l</td>
			<td>VistaLab Technologies</td>
			<td>4060-1002</td>
			<td></td>
		</tr>
		<tr>
			<td>Multi 12-channel pipette tips 250 &#956;l</td>
			<td>VistaLab Technologies</td>
			<td>4060-9025</td>
			<td></td>
		</tr>
		<tr>
			<td>Guava easyCyte 5HT Benchtop Flow Cytometer</td>
			<td>EMD Millipore</td>
			<td>0500-4005</td>
			<td></td>
		</tr>
		<tr>
			<td>NIH Clinical Collections 1 and 2 small molecule libraries</td>
			<td>Evotec</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>For the preparation of neural stem cell media (500 mL)</td>
			<td></td>
			<td></td>
			<td>Final concentration</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>GoldBio.com</td>
			<td>A-421-250</td>
			<td>0.20%</td>
		</tr>
		<tr>
			<td>DMEM/F12 10X</td>
			<td>Corning</td>
			<td>90-091-PB</td>
			<td>1X</td>
		</tr>
		<tr>
			<td>Heparin sodium salt</td>
			<td>Sigma Aldrich</td>
			<td>H3149</td>
			<td>0.0002%</td>
		</tr>
		<tr>
			<td>HEPES 1M</td>
			<td>Sigma Aldrich</td>
			<td>H4036</td>
			<td>5.4 mM</td>
		</tr>
		<tr>
			<td>Insulin-Transferrin- Selenium (ITS -G) (100X)</td>
			<td>Life Technologies</td>
			<td>41400-045</td>
			<td>1X</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma Aldrich</td>
			<td>S-5761</td>
			<td>14.5 mM</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (10,000 U/mL) 100X</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>1X</td>
		</tr>
		<tr>
			<td>Progesterone</td>
			<td>Sigma Aldrich</td>
			<td>P8783</td>
			<td>16 nM</td>
		</tr>
		<tr>
			<td>Putrescine</td>
			<td>Sigma Aldrich</td>
			<td>P5780</td>
			<td>4.8 &#181;M</td>
		</tr>
		<tr>
			<td>Basic FGF (FGF2), Human</td>
			<td>GoldBio</td>
			<td>1140-02-50</td>
			<td>10 ng/ml</td>
		</tr>
		<tr>
			<td>EGF, Human</td>
			<td>GoldBio</td>
			<td>1150-04-100</td>
			<td>20 ng/ml</td>
		</tr>
		<tr>
			<td>Bottle-Top Filter, 150ml, 33mm, 0.22um, Pes, S, Ind</td>
			<td>Corning</td>
			<td>431160</td>
			<td>Use to filter sterlize media</td>
		</tr>
	</tbody>
</table>

flow cytometry-based drug screening system for the identification of small molecules that promote cellular differentiation of glioblastoma stem cells

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median survival following diagnosis is less than 15 months with maximal surgical resection, radiation, and temozolomide chemotherapy. The challenges inherent in developing more effective GBM treatments have become increasingly clear, and include its unyielding invasiveness, its resistance to standard treatments, its genetic complexity and molecular adaptability, and subpopulations of GBM cells with phenotypic similarities to normal stem cells, herein referred to as glioblastoma stem cells (GSCs). Because GSCs are required for tumor growth and progression, differentiation-based therapy represents a viable treatment modality for these incurable neoplasms. 
The following protocol describes a collection of procedures to establish a high throughput screening platform aimed at the identification of small molecules that promote GSC astroglial differentiation. At the core of the system is a glial fibrillary acidic protein (GFAP) differentiation reporter-construct. The protocol contains the following general procedures: (1) establishing GSC differentiation reporter lines; (2) testing/validating the relevance of the reporter to GSC self-renewal/clonogenic capacity; and (3) high-capacity flow-cytometry based drug screening. 
The screening platform provides a straightforward and inexpensive approach to identify small molecules that promote GSCs differentiation. Furthermore, utilization of libraries of FDA-approved drugs holds the potential for the identification of agents that can be repurposed more rapidly. Also, therapies that promote cancer stem cell differentiation are expected to work synergistically with current "standard of care" therapies that have been shown to target and eliminate primarily more differentiated cancer cells.

Three independent patient-derived neurospheres lines were transduced with the lentivirus astroglial reporter encoding for a green-fluorescent protein (GFP) fused in-frame with a Zeocin resistance cassette and driven by the human GFAP promoter element (Figure 1). Next individual clones were isolated by plating 0.7 cells per well in a 96 well plate (Figure 2), this was followed by flow cytometric determination of the percentage of ...

Watch this Scientific Journal Video about Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells at JoVE.

Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells

An efficient screening protocol is presented for the identification of small molecules that promote astroglial differentiation in glioblastoma stem cells (GSCs). The assay is based on a stem cell differentiation reporter whereby the expression of the enhanced GFP (eGFP) is driven by the human GFAP promoter.

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median ...

The overall goal of this procedure is to screen small molecule libraries for agents that promote astroglial differentiation in glioblastoma stem cells. This method can help answer key questions in the cancer stem cell field, such as what are the signaling pathways that are required for maintaining glioblastoma stem cells in the undifferentiated state. Proper execution of this technique allows for the straightforward identification of small molecules that promote glioblastoma stem cell differentiation.The implication of this technique extend toward therapy for Ehlers-Danlos glioblastoma because reducing the percentage of glioblastoma stem cells may decrease the likelihood of recurrence. This method can also be applied to setting differentiation into other cell lineages using other reporter constructs. Our report is the first to establish a high throughput approach to screen for agents that force glioma stem cells to differentiate.Working with lentivirus particles in cancer cells derived from patients can be extremely hazardous. Therefore standard procedure for working with bloodborne pathogens should always be followed. To begin, seed one million glioblastoma stem cells or GSCs in two milliliters of complete neural stem cell growth medium in a six-well plate.Next, transduce the cells with the lentivirus reporter at a multiplicity of infection equal to five. To the cell and virus mixture, add two microliters of polybrene such that the final concentration is eight micrograms per milliliter, and incubate the cells at 37 degrees Celsius and 5%CO2 overnight. After incubation, replace the growth medium to remove unbound virus.And centrifuge cells at 360 times G for five minutes. Then carefully aspirate medium and plate cells back in a six-well plate. And continue to incubate the cells for 24 hours.Harvest 0.5 milliliters of the total culture volume. Pellet cells by centrifugation at 360 times G for five minutes at room temperature. Resuspend cells in 0.5 milliliters fresh neural stem cell growth medium.Place the plate back in the incubator to allow for expansion for at least 72 hours. Add 200 microliters of dissociation reagent and incubate for five minutes in a water bath set to 37 degrees Celsius. Dissociate cells by pippetting up and down gently.To the dissociated cells add 800 microliters of HBSS to ensure minimal cell attachment or aggregation. Next, transfer 200 microliters of each cell suspension into wells of a 96-multiwell plate. Determine the percentage of cells expressing the green fluorescent protein by flow cytometry.Record at least 10, 000 viable cells in each acquisition. In all flow cytometric analysis use parental non-transduced cells or vector-transduced nonfluorescent cells to establish baseline fluorescence. To select and expand individual subclones seed cells at a density of 0.7 cells per well in 100 microliters of neural stem cell medium in a 96-well plate.Maintain these clones in culture for 11 days. Look out for neurospheres with a diameter greater than 100 microns. We have previously established this cutoff size to retrospectively determine if the neuorsphere was originated by a self-renewing glioblastoma stem cell.This cutoff size may need optimization when working with different glioblastoma cell models. Observe the cells under a fluorescence microscope equipped with a FITC filter and mark wells that contain a single neurosphere in which approximately one 1%to 5%of the cells are GFP-positive. After marking, expand individual clones until a sufficient number of cells is available for flow cytometry analysis.Assuming the reporter clones contain 1%to 5%of GFP-positive cells, harvest 0.5 milliliters from each clone along with an equal quantity of non-transduced control cells to determine the exact percentage of GFP-positive cells. After pelleting cells at 360 times G for five minutes at room temperature, aspirate the supernatant. Add 200 microliters of dissociation reagent to each pellet and incubate the tubes in a water bath set to 37 degrees Celsius.After incubation, triturate the cells about 20 to 30 times to achieve a single cell suspension. Then add 800 microliters of HBSS to ensure minimal cell attachment or aggregation. Now transfer 200 microliters of each cell suspension into wells of a 96-multiwell plate.Finally, perform flow cytometry, recording at least 10, 000 viable cells in each acquisition. To assess the clonogenic capacity prepare single cell suspensions of differentiation reporter subclones by triturating the cells about 20 to 30 times. Then plate these cells in 100 microliters of complete neural stem cell growth medium at a density of about five to 500 cells per well in 96-multiwell plates.Maintain these cells in culture for nine to 11 days. Look for neurospheres under a light microscope. A well containing at least one single large neurosphere is considered positive.Considering parental non-transduced cells and GFP-positive lentivirus-transduced cells as controls input the total wells analyzed and the number of positive cells on the ELDA online interface. To begin screening, plate 5000 cells in 99 microliters of complete neural stem cell growth medium in a 96-well plate. Then with a 12-channel pipettor treat cells with two micromolar final concentration of diluted library compounds or with the DMSO control.Incubate the cells for 72 hours. Now add 150 microliters of cell dissociation reagent using a 12-channel pipettor in each well and incubate at 37 degrees Celsius for 20 minutes. Then gently triturate the cells in each well about 20 to 30 times using a 12-channel pipettor until a single cell suspension is achieved.Now perform flow cytometry and determine the percentage of cells expressing the GFAP:GFP reporter. First determine the cell size and viability from the forward and side scatters and gate the viable cell population. Then determine the GFP-positive cells within the viable cell population.An increase of percentage of GFP-positive cells by three standard deviations over controls is considered to be a positive hit which may be adjusted to accommodate user preference of stringency. Representative images of HSR-GBM1 GSC subclones expressing low and high levels of GFAP:GFP are shown. The subclones positive for GFAP:GFP expression were selected by flow cytometry for the patient-derived neurosphere line.Here, low GFAP:GFP indicates that less than 5%of the cells in the clone are GFP-positive, while high GFAP:GFP indicates that greater than 75%of the cells in the clone are GFP-positive. These results show that in vitro self-renewal capacity of GFAP-low subclones is higher than their GFAP-high counterparts as determined by ELDA. Therefore GH subclones are more differentiated than GL subclones.Finally, drug libraries were screened to identify agents capable to induce astroglial differentiation in GSCs. 12 drugs were found to significantly increase the percentage of cells expressing the GFAP:GFP reporter. Once mastered, this technique can be done in a few weeks if it is performed properly.Following this procedure other methods like alamarBlue assay, clonogenic assay in semisolid media, flank or intracranial xenograph injection can be performed in order to answer additional questions like the effect of selective drugs on cellular proliferation and clonogenicity in vitro and tumorigenicity in vivo. After watching this video, you should have a good understanding of how to identify compounds capable of inducing astroglial differentiation in glioblastoma stem cells.

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Cancer Research

8.2K vistas.  Case Western Reserve University School of Medicine. The overall goal of this procedure is to screen small molecule libraries for agents that promote astroglial differentiation in glioblastoma stem cells. This method can help answer key questions in the cancer stem cell field, such as what are the signaling pathways that are required for maintaining glioblastoma stem cells in the undifferentiated state. Proper execution of this technique allows for the straightforward identification of small molecules that promote glioblastoma stem cell differe...

Video: Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells