We are grateful to Mr. Arkadiusz Slusarczyk and Kentucky Biomedical Research Infrastructure Network (KBRIN, P20GM103436) for acquiring transmission electron microscope images. This work was supported in part by grants from NIH AA018016-01 (J.W.E.), Commonwealth of Kentucky Research Challenge Trust Fund (J.W.E.), NIH CA106599 and CA175003 (C.L.), NIH CA198249 (K.Y.), and Free to Breathe Research Grant (K.Y.).

1. Culturing ES-D3 cells
<ol>
	<li>To generate exosome-free fetal bovine serum (FBS), load FBS into an ultracentrifuge and centrifuge at 100,000 x g for 16 h at 4 &#176;C. Following centrifugation, collect serum supernatant as exosome-free FBS for culturing the murine ESC cell line ES-D3 and acquiring exosome-enriched EVs.</li>
	<li>Before plating the ES-D3 cells, coat 15 cm tissue culture dishes using gelatin (0.1%) at room temperature for 30 min.</li>
	<li>Following a previously described protocol<sup class=...

<ol>
	<li>Thomson, J. 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=Embryonic+stem+cell+lines+derived+from+human+blastocysts.">Embryonic stem cell lines derived from human blastocysts.</a> Science. 282 (5391), 1145-1147 (1998).</li><li>Sakthiswary, R., Raymond, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cell+therapy+in+neurodegenerative+diseases:+From+principles+to+practice.">Stem cell therapy in neurodegenerative diseases: From principles to practice.</a> Neural Regeneration Research. 7 (23), 1822-1831 (2012).</li><li>Liu, Y. W., 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=Human+embryonic+stem+cell-derived+cardiomyocytes+restore+function+in+infarcted+hearts+of+non-human+primates.">Human embryonic stem cell-derived cardiomyocytes restore function in infarcted hearts of non-human primates.</a> Nature Biotechnology. 36 (7), 597-605 (2018).</li><li>Aguayo-Mazzucato, C., Bonner-Weir, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cell+therapy+for+type+1+diabetes+mellitus.">Stem cell therapy for type 1 diabetes mellitus.</a> Nature Reviews: Endocrinology. 6 (3), 139-148 (2010).</li><li>Thery, 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=Minimal+information+for+studies+of+extracellular+vesicles+2018+(MISEV2018):+a+position+statement+of+the+International+Society+for+Extracellular+Vesicles+and+update+of+the+MISEV2014+guidelines.">Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines.</a> Journal of Extracell Vesicles. 7 (1), 1535750 (2018).</li><li>Raposo, G., Stoorvogel, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+vesicles:+exosomes,+microvesicles,+and+friends.">Extracellular vesicles: exosomes, microvesicles, and friends.</a> Journal of Cell Biology. 200 (4), 373-383 (2013).</li><li>Meldolesi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exosomes+and+Ectosomes+in+Intercellular+Communication.">Exosomes and Ectosomes in Intercellular Communication.</a> Current Biology. 28 (8), R435-R444 (2018).</li><li>Stremersch, S., De Smedt, S. C., Raemdonck, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Therapeutic+and+diagnostic+applications+of+extracellular+vesicles.">Therapeutic and diagnostic applications of extracellular vesicles.</a> Journal of Control Release. 244 (Pt B), 167-183 (2016).</li><li>Lindenbergh, M. F. S., Stoorvogel, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antigen+Presentation+by+Extracellular+Vesicles+from+Professional+Antigen-Presenting+Cells.">Antigen Presentation by Extracellular Vesicles from Professional Antigen-Presenting Cells.</a> Annual Review of Immunology. 36, 435-459 (2018).</li><li>Kunigelis, K. E., Graner, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Dichotomy+of+Tumor+Exosomes+(TEX)+in+Cancer+Immunity:+Is+It+All+in+the+ConTEXt?.">The Dichotomy of Tumor Exosomes (TEX) in Cancer Immunity: Is It All in the ConTEXt?.</a> Vaccines (Basel). 3 (4), 1019-1051 (2015).</li><li>Becher, B., Tugues, S., Greter, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GM-CSF:+From+Growth+Factor+to+Central+Mediator+of+Tissue+Inflammation.">GM-CSF: From Growth Factor to Central Mediator of Tissue Inflammation.</a> Immunity. 45 (5), 963-973 (2016).</li><li>Conti, L., Gessani, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GM-CSF+in+the+generation+of+dendritic+cells+from+human+blood+monocyte+precursors:+recent+advances.">GM-CSF in the generation of dendritic cells from human blood monocyte precursors: recent advances.</a> Immunobiology. 213 (9-10), 859-870 (2008).</li><li>Higano, C. 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=Integrated+data+from+2+randomized,+double-blind,+placebo-controlled,+phase+3+trials+of+active+cellular+immunotherapy+with+sipuleucel-T+in+advanced+prostate+cancer.">Integrated data from 2 randomized, double-blind, placebo-controlled, phase 3 trials of active cellular immunotherapy with sipuleucel-T in advanced prostate cancer.</a> Cancer. 115 (16), 3670-3679 (2009).</li><li>Yan, W. L., Shen, K. Y., Tien, C. Y., Chen, Y. A., Liu, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+progress+in+GM-CSF-based+cancer+immunotherapy.">Recent progress in GM-CSF-based cancer immunotherapy.</a> Immunotherapy. 9 (4), 347-360 (2017).</li><li>Dranoff, 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=Vaccination+with+irradiated+tumor+cells+engineered+to+secrete+murine+granulocyte-macrophage+colony-stimulating+factor+stimulates+potent,+specific,+and+long-lasting+anti-tumor+immunity.">Vaccination with irradiated tumor cells engineered to secrete murine granulocyte-macrophage colony-stimulating factor stimulates potent, specific, and long-lasting anti-tumor immunity.</a> Proceedings of the National Academy of Sciences of the United States of America. 90 (8), 3539-3543 (1993).</li><li>Tremml, G., Singer, M., Malavarca, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+1,+Unit+1C+4,+Culture+of+mouse+embryonic+stem+cells.">Chapter 1, Unit 1C 4, Culture of mouse embryonic stem cells.</a> Current Protocols in Stem Cell Biology. , (2008).</li><li>Kirsch, P., Hafner, M., Zentgraf, H., Schilling, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time+course+of+fluorescence+intensity+and+protein+expression+in+HeLa+cells+stably+transfected+with+hrGFP.">Time course of fluorescence intensity and protein expression in HeLa cells stably transfected with hrGFP.</a> Molecules and Cells. 15 (3), 341-348 (2003).</li><li>Zeng, X., 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=Stable+expression+of+hrGFP+by+mouse+embryonic+stem+cells:+promoter+activity+in+the+undifferentiated+state+and+during+dopaminergic+neural+differentiation.">Stable expression of hrGFP by mouse embryonic stem cells: promoter activity in the undifferentiated state and during dopaminergic neural differentiation.</a> Stem Cells. 21 (6), 647-653 (2003).</li><li>Yaddanapudi, K., 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=Vaccination+with+embryonic+stem+cells+protects+against+lung+cancer:+is+a+broad-spectrum+prophylactic+vaccine+against+cancer+possible?.">Vaccination with embryonic stem cells protects against lung cancer: is a broad-spectrum prophylactic vaccine against cancer possible?.</a> PLoS One. 7 (7), e42289 (2012).</li><li>Dalby, B., 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=Advanced+transfection+with+Lipofectamine+2000+reagent:+primary+neurons,+siRNA,+and+high-throughput+applications.">Advanced transfection with Lipofectamine 2000 reagent: primary neurons, siRNA, and high-throughput applications.</a> Methods. 33 (2), 95-103 (2004).</li><li>Thery, C., Amigorena, S., Raposo, G., Clayton, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+3,+Unit+3+22,+Isolation+and+characterization+of+exosomes+from+cell+culture+supernatants+and+biological+fluids.">Chapter 3, Unit 3 22, Isolation and characterization of exosomes from cell culture supernatants and biological fluids.</a> Current Protocols in Cell Biology. , (2006).</li><li>Zhang, X., 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=Exosomes+for+Immunoregulation+and+Therapeutic+Intervention+in+Cancer.">Exosomes for Immunoregulation and Therapeutic Intervention in Cancer.</a> Journal of Cancer. 7 (9), 1081-1087 (2016).</li><li>Bunggulawa, E. J., 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=Recent+advancements+in+the+use+of+exosomes+as+drug+delivery+systems.">Recent advancements in the use of exosomes as drug delivery systems.</a> Journal of Nanobiotechnology. 16 (1), 81 (2018).</li><li>Schlesinger, S., Lee, A. H., Wang, G. Z., Green, L., Goff, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proviral+silencing+in+embryonic+cells+is+regulated+by+Yin+Yang+1.">Proviral silencing in embryonic cells is regulated by Yin Yang 1.</a> Cell Reports. 4 (1), 50-58 (2013).</li><li>Dranoff, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GM-CSF-based+cancer+vaccines.">GM-CSF-based cancer vaccines.</a> Immunological Reviews. 188, 147-154 (2002).</li><li>Park, Y. 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=Effects+of+Feeder+Cell+Types+on+Culture+of+Mouse+Embryonic+Stem+Cell+In+Vitro.">Effects of Feeder Cell Types on Culture of Mouse Embryonic Stem Cell In Vitro.</a> Development and Reproduction. 19 (3), 119-126 (2015).</li><li>Lin, S., Talbot, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+culturing+mouse+and+human+embryonic+stem+cells.">Methods for culturing mouse and human embryonic stem cells.</a> Methods in Molecular Biology. 690, 31-56 (2011).</li><li>Yaddanapudi, K., 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=Exosomes+from+GM-CSF+expressing+embryonic+stem+cells+are+an+effective+prophylactic+vaccine+for+cancer+prevention.">Exosomes from GM-CSF expressing embryonic stem cells are an effective prophylactic vaccine for cancer prevention.</a> OncoImmunology. 8 (3), 1561119 (2019).</li></ol>

This study shows a highly efficient method of producing exosome-enriched EVs carrying the immune-stimulatory protein GM-CSF, which can be employed to study the immune-modulatory effects of exosome-enriched EVs. Several studies suggest that exosomes exhibit immune-regulatory and anti-tumor functions22. Thus, exosomes from ESCs expressing GM-CSF might also possess biological activities that regulate the immune response. In this protocol, exogenous murine GM-CSF was stably overexpressed in murine ES-...

ESCs are derived from the blastocyst stage of a preimplantation embryo1. As pluripotent stem cells, ESCs have the capability to self-renew and differentiate into any type of embryonic cell. Due to their remarkable developmental potential and long-term proliferative capacity, ESCs are extremely valuable for biomedical research1. Current research efforts have largely focused on the therapeutic potential of ESCs for a variety of major pathological disorders, including diabetes, heart disease, and neurodegenerative diseases2,3,4.
Mammalian cells, including ESCs, are known to release vesicles with variable sizes to the extracellular environment, and these EVs possess many physiological and pathological functions due to their role in intercellular communication5. Among different subtypes of EVs, exosomes are small membrane vesicles released from various cell types into the extracellular space upon fusion of intermediate endocytic compartments, multivesicular bodies (MVBs), with the plasma membrane6. Exosomes have been reported to mediate intercellular communication and are critically involved in many (patho)physiological processes7,8. Exosomes inherit some biological functions from their own parental cells, because exosomes contain biological materials acquired from the cytosol, including proteins and nucleic acids. Thus, the associated antigens or factors stimulating the immune response specific for a given disease are encapsulated in the exosomes from particular types of cells9. This paved the way for clinical trials exploring tumor-derived exosomes as an anti-cancer vaccine10.
GM-CSF is a cytokine secreted by different types of immune cells11. Emerging evidence demonstrates that GM-CSF activates and regulates the immune system and plays an essential role in the antigen-presenting process12. For instance, a clinical report suggests that GM-CSF stimulates the immune response to tumors as a vaccine adjuvant13. Several GM-CSF-based cancer immunotherapy strategies to exploit the potent immune-stimulatory activity of GM-CSF have been investigated in clinical trials14. Among these, a cancer vaccine composed of irradiated GM-CSF-secreting tumor cells has shown some promise in advanced melanoma patients by inducing cellular and humoral antitumor responses and subsequent necrosis in metastasized tumors15.
Because the exosomes derived from ESCs possess similar biological activities as the original ESCs, maybe GM-CSF-carrying exosomes from ESCs could function as cell-free vesicles to regulate the immune response. In this paper, a detailed method to produce high-quality exosome-enriched EVs from ESCs expressing GM-CSF is described. These exosome-enriched EVs have the potential to serve as immune-regulatory vesicles to modulate the immune response.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alkaline phosphate, Calf Intestinal</td>
			<td>New England Biolabs</td>
			<td>M0290S</td>
			<td>Dephosphorylating DNA plasmid</td>
		</tr>
		<tr>
			<td>anti-Annexin V mAb</td>
			<td>Santa Cruz Biotechnology</td>
			<td>clone H-3, sc-74438</td>
			<td>Western blot, RRID:AB_1118989</td>
		</tr>
		<tr>
			<td>anti-CD81 mAb</td>
			<td>Santa Cruz Biotechnology</td>
			<td>clone B-11, sc-166029</td>
			<td>Western blot, RRID:AB_2275892</td>
		</tr>
		<tr>
			<td>anti-cytochrome c mAb</td>
			<td>Santa Cruz Biotechnology</td>
			<td>clone A-8, sc-13156</td>
			<td>Western blot, RRID:AB_627385</td>
		</tr>
		<tr>
			<td>anti-Flotillin-1 mAb</td>
			<td>Santa Cruz Biotechnology</td>
			<td>clone C-2; sc-74566</td>
			<td>Western blot, RRID:AB_2106563</td>
		</tr>
		<tr>
			<td>anti-GAPDH pAb</td>
			<td>Rockland</td>
			<td>600-401-A33S</td>
			<td>Western blot, RRID:AB_11182910</td>
		</tr>
		<tr>
			<td>anti-mouse IgG, goat, peroxidase-conjugated</td>
			<td>Thermo Fisher</td>
			<td>31430</td>
			<td>Western blot, RRID:AB_228307</td>
		</tr>
		<tr>
			<td>anti-Oxphos COX IV-subunit IV mAb</td>
			<td>Thermo Fisher</td>
			<td>clone 20E8C12 A21348</td>
			<td>Western blot, RRID:AB_221509</td>
		</tr>
		<tr>
			<td>anti-protein disulfide isomerase (PDI) pAb</td>
			<td>Enzo</td>
			<td>ADI-SPA-890</td>
			<td>Western blot, RRID:AB_10616242</td>
		</tr>
		<tr>
			<td>anti-rabbit IgG, goat, peroxidase-conjugated</td>
			<td>Thermo Fisher</td>
			<td>31460</td>
			<td>Western blot, RRID:AB_228341</td>
		</tr>
		<tr>
			<td>BCA (bicinchoninic acid) assay</td>
			<td>Thermo Fisher</td>
			<td>23223</td>
			<td>Determining protein concentrations</td>
		</tr>
		<tr>
			<td>Bis-Tris PAGE Gel, ExpressPlus, 4-20%</td>
			<td>Genscript</td>
			<td>M42015</td>
			<td>Western blot</td>
		</tr>
		<tr>
			<td>Carbenicillin, Disodium Salt</td>
			<td>Thermo Fisher</td>
			<td>10177012</td>
			<td>Selecting E. coli colonies</td>
		</tr>
		<tr>
			<td>Centrifuge, Avanti J-26 XPI</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td>Low speed centrifugation</td>
		</tr>
		<tr>
			<td>Centrifuge rotor, JA-10</td>
			<td>Beckman Coulter</td>
			<td>09U1597</td>
			<td>Low speed centrifugation</td>
		</tr>
		<tr>
			<td>Centrifuge bottle, Nalgene PPCO</td>
			<td>Thermo Fisher</td>
			<td>3120-0500PK</td>
			<td>Low speed centrifugation</td>
		</tr>
		<tr>
			<td>Cu grids with carbon support film</td>
			<td>Electron Microscopy Sciences</td>
			<td>FF200-Cu</td>
			<td>Acquiring electron microscopy images</td>
		</tr>
		<tr>
			<td>EcoRI</td>
			<td>New England Biolabs</td>
			<td>R0101</td>
			<td>Digesting DNA plasmid</td>
		</tr>
		<tr>
			<td>Enhanced chemiluminescence detection system</td>
			<td>Thermo Fisher</td>
			<td>32106</td>
			<td>Western blot</td>
		</tr>
		<tr>
			<td>FACScalibur flow cytometer</td>
			<td>Becton Dickinson</td>
			<td></td>
			<td>Examining GFP levels of ES-D3 cells</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>ATCC</td>
			<td>SCRR-30-2020</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>Fisherbrand Sterile Cell Strainers; Mesh Size: 40&#956;m</td>
			<td>Thermo Fisher</td>
			<td>22-363-547</td>
			<td>Filtering ES-D3 cells for FACS sorting</td>
		</tr>
		<tr>
			<td>Gelatin (0.1%)</td>
			<td>Thermo Fisher</td>
			<td>ES006B</td>
			<td>Culturing ES-D3 cells</td>
		</tr>
		<tr>
			<td>GM-CSF ELISA kit</td>
			<td>Thermo Fisher</td>
			<td>88733422</td>
			<td>Determining GM-CSF concentrations</td>
		</tr>
		<tr>
			<td>KnockOut Dulbecco&#8217;s Modified Eagle&#8217;s Medium</td>
			<td>Thermo Fisher</td>
			<td>10-829-018</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>Leukemia Inhibitory Factor</td>
			<td>Thermo Fisher</td>
			<td>ESG1106</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>VWR</td>
			<td>VWRL0131-0100</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>Lipofectamine 2000 transfection reagent</td>
			<td>Thermo Fisher</td>
			<td>11668019</td>
			<td>Transfecting ES-D3 cells</td>
		</tr>
		<tr>
			<td>Microplate reader, PowerWave XS</td>
			<td>BioTek</td>
			<td></td>
			<td>Determining GM-CSF concentrations</td>
		</tr>
		<tr>
			<td>MoFlo XDP high-speed cell sorter</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td>Isolating single ES-D3 cell clones</td>
		</tr>
		<tr>
			<td>NEB 5-alpha Competent E. coli</td>
			<td>New England Biolabs</td>
			<td>C2988J</td>
			<td>Generating GM-CSF expression plasmid</td>
		</tr>
		<tr>
			<td>Neomycin</td>
			<td>Thermo Fisher</td>
			<td>10-131-035</td>
			<td>Selecting ES-D3 clones</td>
		</tr>
		<tr>
			<td>Non-essential amino acids</td>
			<td>Thermo Fisher</td>
			<td>SH3023801</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>Non-fat dry milk</td>
			<td>Thermo Fisher</td>
			<td>NC9022655</td>
			<td>Western blot</td>
		</tr>
		<tr>
			<td>Opti-MEM I Reduced Serum Medium</td>
			<td>Thermo Fisher</td>
			<td>31985062</td>
			<td>Transfecting ES-D3 cells</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Electron Microscopy Sciences</td>
			<td>15710</td>
			<td>Acquiring electron microscopy images</td>
		</tr>
		<tr>
			<td>Penicillin/streptomycin</td>
			<td>VWR</td>
			<td>sc45000-652</td>
			<td>Medium for ES-D3 cells</td>
		</tr>
		<tr>
			<td>Plasmid pEF1a-FD3ER-IRES-hrGFP</td>
			<td>Addgene</td>
			<td>37270</td>
			<td>Generating GM-CSF expression plasmid</td>
		</tr>
		<tr>
			<td>PVDF membranes</td>
			<td>Millipore EMD</td>
			<td>IPVH00010</td>
			<td>Western blot</td>
		</tr>
		<tr>
			<td>QIAprep Spin Miniprep Kit (250)</td>
			<td>QIAGEN</td>
			<td>27106</td>
			<td>Generating GM-CSF expression plasmid</td>
		</tr>
		<tr>
			<td>QIAquick Gel Extraction Kit (50)</td>
			<td>QIAGEN</td>
			<td>28704</td>
			<td>Generating GM-CSF expression plasmid</td>
		</tr>
		<tr>
			<td>Quick Ligation Kit</td>
			<td>New England Biolabs</td>
			<td>M2200S</td>
			<td>Generating GM-CSF expression plasmid</td>
		</tr>
		<tr>
			<td>Transmission electron microscope</td>
			<td>Hitachi</td>
			<td>HT7700</td>
			<td>Acquiring electron microscopy images</td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>VWR</td>
			<td>45000-660</td>
			<td>Culturing ES-D3 cells</td>
		</tr>
		<tr>
			<td>Ultracentrifuge, OptimaTM L-100 XP</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td>High speed centrifugation</td>
		</tr>
		<tr>
			<td>Ultracentrifuge rotor, 45Ti</td>
			<td>Beckman Coulter</td>
			<td>09U4454</td>
			<td>High speed centrifugation</td>
		</tr>
		<tr>
			<td>Ultracentrifuge polycarbonate bottle</td>
			<td>Beckman Coulter</td>
			<td>355622</td>
			<td>High speed centrifugation</td>
		</tr>
		<tr>
			<td>UranyLess staining solution</td>
			<td>Electron Microscopy Sciences</td>
			<td>22409</td>
			<td>Acquiring electron microscopy images</td>
		</tr>
	</tbody>
</table>

isolation of exosome-enriched extracellular vesicles carrying granulocyte-macrophage colony-stimulating factor from embryonic stem cells

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell types, ESCs release small membrane vesicles, such as exosomes, to the extracellular environment. Exosomes serve as essential mediators of intercellular communication and play a basic role in many (patho)physiological processes. Granulocyte-macrophage colony-stimulating factor (GM-CSF) functions as a cytokine to modulate the immune response. The presence of GM-CSF in exosomes has the potential to boost their immune-regulatory function. Here, GM-CSF was stably overexpressed in the murine ESC cell line ES-D3. A protocol was developed to isolate high-quality exosome-enriched extracellular vesicles (EVs) from ES-D3 cells overexpressing GM-CSF. Isolated exosome-enriched EVs were characterized by a variety of experimental approaches. Importantly, significant amounts of GM-CSF were found to be present in exosome-enriched EVs. Overall, GM-CSF-bearing exosome-enriched EVs from ESCs might function as cell-free vesicles to exert their immune-regulatory activities.

GM-CSF is overexpressed in murine ESCs. 
To stably overexpress GM-CSF in ES-D3 cells, murine GM-CSF cDNA was cloned into a transfection vector to generate the expression vector pEF1&#945;-mGM-CSF-IRES-hrGFP (Figure 1A). GM-CSF was overexpressed in ES-D3 cells by transfection, and about 20% of transiently transfected ES-D3 cells were GFP-positive. Cell clones stably overexpressing GM-CSF or the empty vector control were a...

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Isolation of Exosome-Enriched Extracellular Vesicles Carrying Granulocyte-Macrophage Colony-Stimulating Factor from Embryonic Stem Cells

This study describes a method to isolate exosome-enriched extracellular vesicles carrying immune-stimulatory granulocyte macrophage colony-stimulating factors from embryonic stem cells.

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell ...

Our protocol can be used to produce high quality exosome-enriched extracellular vesicles from embryonic stem cells that express the immune stimulatory factor, GM-CSF. Exosome enriched extracellular vesicles carrying GM-CSF, have the potential to serve a cell-free immune regulatory vesicles that can modulate the immune response. Researchers with the basic molecular and cellular biology training, Should be able to easily as could this protocol, but anyone performing this protocol for the first time should follow the directions closely.Since our protocol is complicated, visualizing the intricate details of each step will help other researchers To generate exosome free FBS, ultracentrifuge the desired volume of FBS and collect the exosome free supernatant. Before plating the ESD three cells, coat 15 centimeter tissue culture dishes with 0.1%Gelatin at room temperature for 30 minutes. Remove Gelatin by aspiration and culture the ESD three cells without feeder layer cells in ESD three cell culture medium at 37 degrees Celsius in 5%Carbon dioxide humidified incubator until the cells reach 90%confluency.Wash the almost confluent cultures with five milliliters of 0.05%trypsin per dish followed by a five minute incubation at 37 degrees Celsius in fresh trypsin. At the end of the incubation pull the detached cells in a centrifuge tube and inactivate the trypsin with five milliliters of fresh culture medium. Sediment the cells by centrifugation and re-suspend the pallets in fresh medium for counting For passaging, plate five times 10 to the sixth of the ESD three cells in 15 milliliters of cell culture medium onto new Gelatin coated plates for three days of culture before sub-culturing the cells To collect the cell culture supernatant for the isolation of exosome enriched extracellular vesicles plate one times 10 to the seventh ESD three cells in 15 milliliters of cell culture medium per new Gelatin coated plate for three days prior to collecting the cell culture supernatants For exosome enriched extra cellular vesicle isolation, First sediment the large cell fragments within the supernatants collected from 72 hour cultured ESD three cells by centrifugation.After collecting the supernatant, Ultracentrifuge the samples and discard the supernatants. Gently rinse each pallette two times with one milliliter of PBS per wash to remove any residual culture supernatant and quantify the exosome enriched extracellular vesicle protein content with a Bicinchoninic acid assay, according to the manufacturer's instruction. Then re-suspend the exosome enriched extracellular vesicles in PBS at a six micrograms per micro meter concentration for storage at minus 80 degrees Celsius.To visualize the exosome enriched extracellular vesicles by transmission electron microscopy fix three to five micrograms per milliliter of the extracellular vesicles with the final concentration of 2%electron microscope grid paraformaldehyde at room temperature for two hours. At the end of the incubation, load 10 microliters of the fixed samples onto Copper Grids with carbon support film for one minute before draining the grids with filter paper, stay in the grids with an appropriate staining solution, according to the manufacturer's protocol and use tweezers to transfer the grids to a piece of filter paper, then use the transmission electron microscope with a 50, 000 times magnification to acquire electron microscopy images, according to the standard protocols. To prepare Whole Cell Extracts, collect ESD three cells from culture as demonstrated, and re-suspend the harvested cells in PBS for counting.After a second centrifugation, re-suspend the cells out of five times 10 to the third cells per microliter of SDS page loading buffer containing 0.5%SDS concentration and Sonicate the samples for 10 seconds on a Sonicator with a 10%amplitude. Then heat the samples at 100 degrees Celsius for five minutes. To prepare lysates for the exosome enriched extracellular vesicles, Re-suspend the exosome enriched extracellular vesicles in SDS page loading buffer containing 0.5%SDS at a 1.2 micrograms per microliter concentration and Sonicate the samples for 10 seconds as demonstrated then heat the samples at 100 degrees Celsius for five minutes.For Western Blot Analysis, load 10 microliter wholesale extract and exosome enriched extracellular vesicle lysate samples into individual Wells of a best stress page gel. At the end of the run, transfer the proteins onto PVDF membranes and incubate the membranes with the appropriate primary and secondary antibodies of interest, then detect the protein expression using an enhanced chemiluminescence detection kit, According to the manufacturer's instructions. To evaluate the amount of GM-CSF within exosome enriched extracellular vesicles, use a kit Murine GM-CSF to coat an ELISA Plate with anti GM-CSF capture antibody next, treat 0.6 micrograms of exosome enriched extracellular vesicles samples with 100 microliters of PBS alone, or PBS plus 0.05%tween 20 at room temperature for 30 minutes.At the end of the incubation, add the treated samples to individual Wells of the prepared ELISA Plate for a one hour incubation at room temperature followed by washing of the appropriate corresponding Wells with PBS alone, or PBS plus 0.05%tween 20. After the wash, add the detection antibody to the samples for a one hour incubation at room temperature followed by a wash with PBS alone or PBS plus 0.05%tween 20 as demonstrated, Then add Avidin Horseradish Peroxidase to the samples for a 30 minute incubation at room temperature, followed by a wash and measuring the absorbance in each well on a Microplate Reader at 450 nanometers. The GFP fluorescence intensity of a GM-CSF expressing ESD three cell line or an ESD three cell line expressing an empty vector is much higher than that of their parental counterparts.ELISA reveals that ESD three cells expressing GM-CSF produce markedly higher levels of GMCSF in their cell culture supernatant than do empty vector control cells. Furthermore, the amount of GM-CSF generated by GM-CSF expressing ESD three cells is similar to that produced by STO fibroblasts expressing GM-CSF. Transmission electron microscopy of extracellular vesicles isolated from vector transduced and GM-CSF transduced cell cultures reveal vesicles of different sizes that fall within the expected 30 to 100 nanometer diameter range.The expression of exosomal markers, including CD81, Annexin V and flotillin-1 is markedly enhanced in extracellular vesicles, isolated from ESD three cells compared to corresponding wholesale extracts by Western blot analysis. Importantly, the presence of other sub-cellular compartment markers in ESD three derived extracellular vesicles was not detected including the endoplasmic reticulum marker, Protein Disulfide Isomerase, the mitochondrial markers, cytochrome C and Oxphos complex IV-subunit IV and the cytosolic marker GAPDH. After washing with 0.05%tween 20, the background GM-CSF levels detected in the control Extracellular vesicles was significantly reduced.In contrast, GM-CSF levels in the extracellular vesicles of GM-CSF expressing cells was significantly increased by tween 20. Acquiring high quality exosome enriched extracellular vesicles carrying GMCSF is the most important step for the success of this protocol. Researchers can perform additional experiments, such as studies in GM-CSF dependent cell lines and animals to determine whether exosome enriched extracellular vesicles caring GM-CSF can function as cell-free immune regulatory vesicles.These exosome enriched extracellular vesicles can then be used to explore how modulation of the immune response affects different disease conditions.

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Research

JoVE Journal

Cancer Research

Invasive Behavior of Human Breast Cancer Cells in Embryonic Zebrafish

In many cases, cancer patients do not die of a primary tumor, but rather because of metastasis. Although numerous rodent models are available for studying cancer metastasis in vivo, other efficient, reliable, low-cost models are needed to quickly access the potential effects of (epi)genetic changes or pharmacological compounds. As such, we illustrate and explain the feasibility of xenograft models using human breast cancer cells injected into zebrafish embryos to support this goal. Under the microscope, fluorescent proteins or chemically labeled human breast cancer cells are transplanted into transgenic zebrafish embryos, Tg (fli:EGFP), at the perivitelline space or duct of Cuvier (Doc) 48 h after fertilization. Shortly afterwards, the temporal-spatial process of cancer cell invasion, dissemination, and metastasis in the living fish body is visualized under a fluorescent microscope. The models using different injection sites, i.e., perivitelline space or Doc are complementary to one another, reflecting the early stage (intravasation step) and late stage (extravasation step) of the multistep metastatic cascade of events. Moreover, peritumoral and intratumoral angiogenesis can be observed with the injection into the perivitelline space. The entire experimental period is no more than 8 days. These two models combine cell labeling, micro-transplantation, and fluorescence imaging techniques, enabling the rapid evaluation of cancer metastasis in response to genetic and pharmacological manipulations.

Here, we describe xenograft zebrafish models using two different injection sites, i.e., perivitelline space and duct of Cuvier, to investigate the invasive behavior and to assess the intravasation and extravasation potential of human breast cancer cells, respectively.

In many cases, cancer patients do not die of a primary tumor, but rather because of metastasis. Although numerous rodent models are available for studying ...

Harnessing the DNA Dye-triggered Side Population Phenotype to Detect and Purify Cancer Stem Cells from Biological Samples

Cancer is a stem cell-driven disease and eradication of these cells has become a major therapeutic goal. Deciphering vulnerabilities of Cancer Stem Cells (CSCs) and identifying suitable molecular targets relies on methods that allow their specific discrimination in heterogeneous samples such as cell lines and ex vivo tumor tissue. Flow cytometry/FACS is a powerful technology to multi-parametrically dissect biological samples at the single cell level and is to date the method of choice to recover live cells for downstream analyses. Surface markers such as CD44 and CD133 as well as detection of aldehyde dehydrogenase enzymatic activity have often been used to define and sort out CSCs from tumor samples by FACS. A complementary approach, depicted here in methodological detail, makes use of functional dye extrusion by ABC drug transporters, which identifies a distinct population of fluorescence-dim cells commonly referred to as side population (SP). SP&#160;cancer cells exhibit canonical stem cell characteristics and can be abrogated and functionally confirmed using agents that inhibit the dye-extruding drug transporter (most frequently ABCB1/P-glycoprotein/MDR1/CD243 and ABCG2/Bcrp1/CD338). Moreover, the SP&#160;assay is compatible with other flow cytometric evaluations such as staining of surface antigens, aldehyde dehydrogenase detection and dead cell discrimination (e.g., with 7-AAD or propidium iodide (PI)). Thus, we describe a valuable and broadly applicable method for CSC identification, isolation and sub-characterization mechanistically based on a functional, rather than a phenotypic parameter. Although originally performed with Hoechst 33342 as triggering dye, we here focus on the more recent Violet dye-based SP phenotype that is resolvable on any flow cytometer equipped with a violet laser source.

Methods allowing the characterization and isolation of stem cell populations from biological samples are critical for the advance of stem cell-targeted treatments in cancer and beyond. Here, we provide a detailed protocol for cancer stem cell isolation using the dye-triggered side population phenotype.

Cancer is a stem cell-driven disease and eradication of these cells has become a major therapeutic goal. Deciphering vulnerabilities of Cancer Stem Cells ...

A Preclinical Mouse Model of Osteosarcoma to Define the Extracellular Vesicle-mediated Communication Between Tumor and Mesenchymal Stem Cells

Within the tumor microenvironment, resident or recruited mesenchymal stem cells (MSCs) contribute to malignant progression in multiple cancer types. Under the influence of specific environmental signals, these adult stem cells can release paracrine mediators leading to accelerated tumor growth and metastasis. Defining the crosstalk between tumor and MSCs is of primary importance to understand the mechanisms underlying cancer progression and identify novel targets for therapeutic intervention. 
Cancer cells produce high amounts of extracellular vesicles (EVs), which can profoundly affect the behavior of target cells in the tumor microenvironment or at distant sites. Tumor EVs enclose functional biomolecules, including inflammatory RNAs and (onco)proteins, that can educate stromal cells to enhance the metastatic behavior of cancer cells or to participate in the pre-metastatic niche formation. In this article, we describe the development of a preclinical cancer mouse model that enables specific evaluation of the EV-mediated crosstalk between tumor and mesenchymal stem cells. First, we describe the purification and characterization of tumor-secreted EVs and the assessment of the EV internalization by MSCs. We then make use of a multiplex bead-based immunoassay to evaluate the alteration of the MSC cytokine expression profile induced by cancer EVs. Finally, we illustrate the generation of a bioluminescent orthotopic xenograft mouse model of osteosarcoma that recapitulates the tumor-MSC interaction, and show the contribution of EV-educated MSCs to tumor growth and metastasis formation. 
Our model provides the opportunity to define how cancer EVs shape a tumor-supporting environment, and to evaluate whether blockade of the EV-mediated communication between tumor and MSCs prevents cancer progression.

Direct injection of cancer-derived extracellular vesicles (EVs) leads to reprogramming of bone marrow supporting tumor progression; however, which cells mediate this effect is unclear. Herein, we describe a step-by-step protocol to investigate EV-mediated tumor-mesenchymal stem cell (MSC) interactions in vivo, revealing a crucial role for EV-educated MSCs in metastasis.

Within the tumor microenvironment, resident or recruited mesenchymal stem cells (MSCs) contribute to malignant progression in multiple cancer types. Under ...

Isolation and Characterization of Tumor-initiating Cells from Sarcoma Patient-derived Xenografts

The existence and importance of tumor-initiating cells (TICs) have been supported by increasing evidence during the past decade. These TICs have been shown to be responsible for tumor initiation, metastasis, and drug resistance. Therefore, it is important to develop specific TIC-targeting therapy in addition to current chemotherapy strategies, which mostly focus on the bulk of non-TICs. In order to further understand the mechanism behind the malignancy of TICs, we describe a method to isolate and to characterize TICs in human sarcomas. Herein, we show a detailed protocol to generate patient-derived xenografts (PDXs) of human sarcomas and to isolate TICs by fluorescence-activated cell sorting (FACS) using human leukocyte antigen class I (HLA-1) as a negative marker. Also, we describe how to functionally characterize these TICs, including a sphere formation assay and a tumor formation assay, and to induce differentiation along mesenchymal pathways. The isolation and characterization of PDX TICs provide clues for the discovery of potential targeting therapy reagents. Moreover, increasing evidence suggests that this protocol may be further extended to isolate and characterize TICs from other types of human cancers.

We describe a detailed protocol for the isolation of tumor-initiating cells from human sarcoma patient-derived xenografts by fluorescence-activated cell sorting, using human leukocyte antigen-1 (HLA-1) as a negative marker, and for the further validation and characterization of these HLA-1-negative tumor-initiating cells.

The existence and importance of tumor-initiating cells (TICs) have been supported by increasing evidence during the past decade. These TICs have been ...

Isolation of Human Endothelial Cells from Normal Colon and Colorectal Carcinoma - An Improved Protocol

Primary cells isolated from human carcinomas are valuable tools to identify pathogenic mechanisms contributing to disease development and progression. In particular, endothelial cells (EC) constituting the inner surface of vessels, directly participate in oxygen delivery, nutrient supply, and removal of waste products to and from tumors, and are thereby prominently involved in the constitution of the tumor microenvironment (TME). Tumor endothelial cells (TECs) can be used as cellular biosensors of the intratumoral microenvironment established by communication between tumor and stromal cells. TECs also serve as targets of therapy. Accordingly, in culture these cells allow studies on mechanisms of response or resistance to anti-angiogenic treatment. Recently, it was found that TECs isolated from human colorectal carcinoma (CRC) exhibit memory-like effects based on the specific TME they were derived from. Moreover, these TECs actively contribute to the establishment of a specific TME by the secretion of different factors. For example, TECs in a prognostically favorable Th1-TME secrete the anti-angiogenic tumor-suppressive factor secreted protein, acidic and rich in cysteine-like 1 (SPARCL1). SPARCL1 regulates vessel homeostasis and inhibits tumor cell proliferation and migration. Hence, cultures of pure, viable TECs isolated from human solid tumors are a valuable tool for functional studies on the role of the vascular system in tumorigenesis. Here, a new up-to-date protocol for the isolation of primary EC from the normal colon as well as CRC is described. The technique is based on mechanical and enzymatic tissue digestion, immunolabeling, and fluorescence activated cell sorting (FACS)-sorting of triple-positive cells (CD31, VE-cadherin, CD105). With this protocol, viable TEC or normal endothelial cell (NEC) cultures could be isolated from colon tissues with a success rate of 62.12% when subjected to FACS-sorting (41 pure EC cultures from 66 tissue samples). Accordingly, this protocol provides a robust approach to isolate human EC cultures from normal colon and CRC.

Tumor endothelial cells are important determinants of the tumor microenvironment and the course of the disease. Here, a protocol for the isolation of pure and viable endothelial cells from human colorectal carcinoma and normal colon to be used in drug testing and pathogenesis research is described.

Primary cells isolated from human carcinomas are valuable tools to identify pathogenic mechanisms contributing to disease development and progression. In ...

Mesenchymal Stem Cell Isolation from Pulp Tissue and Co-Culture with Cancer Cells to Study Their Interactions

Cancer as a multistep process and complicated disease is not only regulated by individual cell proliferation and growth but also controlled by tumor environment and cell-cell interactions. Identification of cancer and stem cell interactions, including changes in extracellular environment, physical interactions, and secreted factors, might enable the discovery of new therapy options. We combine known co-culture techniques to create a model system for mesenchymal stem cells (MSCs) and cancer cell interactions. In the current study, dental pulp stem cells (DPSCs) and PC-3 prostate cancer cell interactions were examined by direct and indirect co-culture techniques. Condition medium (CM) obtained from DPSCs and 0.4 &#181;m pore sized trans-well membranes were used to study paracrine activity. Co-culture of different cell types together was performed to study direct cell-cell interaction. The results revealed that CM increased cell proliferation and decreased apoptosis in prostate cancer cell cultures. Both CM and trans-well system increased cell migration capacity of PC-3 cells. Cells stained with different membrane dyes were seeded into the same culture vessels, and DPSCs participated in a self-organized structure with PC-3 cells under this direct co-culture condition. Overall, the results indicated that co-culture techniques could be useful for cancer and MSC interactions as a model system.

We provide protocols for evaluation of mesenchymal stem cells isolated from dental pulp and prostate cancer cell interactions based on direct and indirect co-culture methods. Condition medium and trans-well membranes are suitable to analyze indirect paracrine activity. Seeding differentially stained cells together is an appropriate model for direct cell-cell interaction.

Cancer as a multistep process and complicated disease is not only regulated by individual cell proliferation and growth but also controlled by tumor ...

Extraction of Extracellular Vesicles from Whole Tissue

Circulating and interstitial small membrane-bound extracellular vesicles (EVs) represent promising targets for the development of novel diagnostic or prognostic biomarker assays, and likely serve as important players in the progression of a vast spectrum of diseases. Current research is focused on the characterization of vesicles secreted from multiple cell and tissue types in order to better understand the role of EVs in the pathogenesis of conditions including neurodegeneration, inflammation, and cancer. However, globally consistent and reproducible techniques to isolate and purify vesicles remain in progress. Moreover, methods for extraction of EVs from solid tissue ex vivo are scarcely described. Here, we provide a detailed protocol for extracting small EVs of interest from whole fresh or frozen tissues, including brain and tumor specimens, for further characterization. We demonstrate the adaptability of this method for multiple downstream analyses, including electron microscopy and immunophenotypic characterization of vesicles, as well as quantitative mass spectrometry of EV proteins.

Here, we provide a detailed protocol to isolate small extracellular vesicles (EVs) from whole tissues, including brain and tumor specimens. This method offers a reproducible technique to extract EVs from solid tissue for further downstream analyses.

Circulating and interstitial small membrane-bound extracellular vesicles (EVs) represent promising targets for the development of novel diagnostic or ...

Spatial and Temporal Control of Murine Melanoma Initiation from Mutant Melanocyte Stem Cells

Cutaneous melanoma is well known as the most aggressive skin cancer. Although the risk factors and major genetic alterations continue to be documented with increasing depth, the incidence rate of cutaneous melanoma has shown a rapid and continuous increase during recent decades. In order to find effective preventative methods, it is important to understand the early steps of melanoma initiation in the skin. Previous data has demonstrated that follicular melanocyte stem cells (MCSCs) in the adult skin tissues can act as melanoma cells of origin when expressing oncogenic mutations and genetic alterations. Tumorigenesis arising from melanoma-prone MCSCs can be induced when MCSCs transition from a quiescent to active state. This transition in melanoma-prone MCSCs can be promoted by the modulation of either hair follicle stem cells&#39; activity state or through extrinsic environmental factors such as ultraviolet-B (UV-B). These factors can be artificially manipulated in the laboratory by chemical depilation, which causes transition of hair follicle stem cells and MCSCs from a quiescent to active state, and by UV-B exposure using a benchtop light. These methods provide successful spatial and temporal control of cutaneous melanoma initiation in the murine dorsal skin. Therefore, these in vivo model systems will be valuable to define the early steps of cutaneous melanoma initiation and could be used to test potential methods for tumor prevention.

The following procedure describes a method for spatial and temporal control of melanocytic tumor initiation in murine dorsal skin, using a genetically engineered mouse model. This protocol describes macroscopic as well as microscopic cutaneous melanoma initiation.

Cutaneous melanoma is well known as the most aggressive skin cancer. Although the risk factors and major genetic alterations continue to be documented ...

Isolation of Stem-like Cells from 3-Dimensional Spheroid Cultures

Despite advances in adult stem cell research, identification and isolation of stem cells from tissue specimens remains a major challenge. While resident stem cells are relatively quiescent with niche restraints in adult tissues, they enter the cell cycle in anchor-free three-dimensional (3D) culture and undergo both symmetric and asymmetric cell division, giving rise to both stem and progenitor cells. The latter proliferate rapidly and are the major cell population at various stages of lineage commitment, forming heterogeneous spheroids. Using primary normal human prostate epithelial cells (HPrEC), a spheroid-based, label-retention assay was developed that permits the identification and functional isolation of the spheroid-initiating stem cells at a single cell resolution.
HPrEC or cell lines are two-dimensionally (2D) cultured with BrdU for 10 days to permit its incorporation into the DNA of all dividing cells, including self-renewing stem cells. Wash out commences upon transfer to the 3D culture for 5 days, during which stem cells self-renew through asymmetric division and initiate spheroid formation. While relatively quiescent daughter stem cells retain BrdU-labeled parental DNA, the daughter progenitors rapidly proliferate, losing the BrdU label. BrdU can be substituted with CFSE or Far Red pro-dyes, which permit live stem cell isolation by FACS. Stem cell characteristics are confirmed by in vitro spheroid formation, in vivo tissue regeneration assays, and by documenting their symmetric/asymmetric cell divisions. The isolated label-retaining stem cells can be rigorously interrogated by downstream molecular and biologic studies, including RNA-seq, ChIP-seq, single cell capture, metabolic activity, proteome profiling, immunocytochemistry, organoid formation, and in vivo tissue regeneration. Importantly, this marker-free functional stem cell isolation approach identifies stem-like cells from fresh cancer specimens and cancer cell lines from multiple organs, suggesting wide applicability. It can be used to identify cancer stem-like cell biomarkers, screen pharmaceuticals targeting cancer stem-like cells, and discover novel therapeutic targets in cancers.

Using human primary prostate epithelial cells, we report a novel biomarker-free method of functional characterization of stem-like cells by a spheroid-based label-retention assay. A step-by-step protocol is described for BrdU, CFSE, or Far Red 2D cell labeling; three-dimensional spheroid formation; label-retaining stem-like cell identification by immunocytochemistry; and isolation by FACS.

Despite advances in adult stem cell research, identification and isolation of stem cells from tissue specimens remains a major challenge. While resident ...

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.

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