This work is supported by the Imperial BRC, the National Institute for Health Research, and Action Against Cancer with special mention to Hilary Craft and Sir Douglas Myers.

The procedures below have been ethically approved by Imperial College, London.
1. Generation of Primary Mammospheres from Human Breast Cancer Cell Lines
NOTE: Perform the following steps under a sterile culture hood.
<ol>
	<li>Prepare Mammosphere Media containing DMEM/F12 supplemented with 2 mM L-glutamine, 100 U/ml penicillin, 100 U/ml streptomycin. Prepare complete media immediately before use by adding 20 ng/ml recombinant human epidermal growth factor (EGF; Sigma), 10 ng/ml recombinant human basic fibroblast growth factor (bFGF; R&#38;D Systems) and 1x B27 supplement.</li>
	<li>Aspirate media from flask containing adherent MCF-7 or MDA-MB-231 cells (or a breast cancer cell line of your choice; 70-80% confluence), wash twice in 1x PBS, and trypsinize cells.</li>
	<li>Centrifuge cells at 200 x g at room temperature for 5 min. Decant supernatant and resuspend cells in 1-5 ml of mammosphere media. Pipette up and down and if necessary use a 40 &#181;m cell strainer cap filter to obtain single-cell suspension. Use a hemocytometer to ensure a single cell suspension has formed (if not, use a 25 G needle to syringe the cell suspension up to 3 times).</li>
	<li>If necessary isolate CD44+CD24- cellular subset via FACS using anti-CD24-phycoerythrin (PE) and anti-CD44-fluorescein isothiocyanate (FITC) monoclonal antibodies9. Alternatively, isolate such population using a magnetic-activated cell sorting (MACS) system with anti-CD44 and anti-CD24-biotin combined microbeads as per manufacturer&#8217;s instructions. Perform positive selection using LS columns, and negative selection using LD columns and confirm the phenotypes of all isolated cells by flow cytometry17.</li>
	<li>Calculate the number of viable cells per ml using trypan blue. 
	NOTE: Cell viability is calculated as the number of viable cells divided by the total number of cells within the grids on the hemocytometer. Cells that take up trypan blue are considered non-viable. The following procedure is used to accurately determine proportion of viable cells.
	<ol>
		<li>Prepare a 0.4% solution of trypan blue in PBS. Add 0.1 ml of trypan blue stock solution to 1 ml of cells. Load a hemocytometer and examine immediately under a microscope at low magnification. Count the number of total cells and the number of blue staining cells. 
		Viable cells = [1.00 &#8211; (Number of blue cells &#247; Number of total cells)] &#215; 100.</li>
		<li>To calculate the number of viable cells per ml of culture, use the formula below. Remember to correct for the dilution factor. 
		Number of viable cells &#215; 104 &#215; 1.1 = cells/ml culture</li>
	</ol>
	</li>
	<li>Resuspend a pre-determined amount of cells in 2 ml of complete mammosphere media in each well of a 6-well ultra-low adherent plate. The seeding density is normally 500-4,000 cells/cm2 cell per well. Optionally use low attachment 24-well plates while seeding cells at the same density in 0.5 ml of media. 
	NOTE: We recommend optimization of seeding density and time of culture for each cell lines of interest.</li>
	<li>Incubate ultra low-attachment 6-well plates at 37 &#176;C and 5% CO2 for 5-10 days (depending on the cell line and the size of mammospheres) without disturbing the plates, particularly during the growth phase of the first 5 days.</li>
</ol>
2. Generation of Primary Mammospheres from Human Breast Cancer Clinical Samples
NOTE: Human breast cancer tissue can be obtained from patients undergoing surgery for the removal of breast tumors. Store tissue on ice for up to 24 hr in 50 ml sterile tubes in culture media containing 100 U/ml penicillin and 100 U/ml streptomycin. Perform the following steps under a sterile culture hood.
<ol>
	<li>Transfer the sample into a 100 mm tissue Petri dish with a small volume of media. Remove the adipose tissue using sterile scissors, scapel and tweezers.</li>
	<li>Add 2-3 ml of DMEM/F12 and mince the sample into 1 mm3 pieces with a sterile scapel or razor blade until no large pieces remain.</li>
	<li>Resuspend the tissue pieces in pre-warmed 10 ml DMEM containing proteolytic enzymes (3,000 U/ml collagenase and 1,000 U/ml hyaluronidase) and incubate at 37 &#176;C in a rotary shaker until all the tissue fragments are digested. Usually complete digestion takes from 1-3 hr. Adjust the digestion time according to pathological characters of tumors. (For example breast adenocarcinoma is usually harder to digest compared to mucinous carcinoma which is more fragile and needs shorter digestion time). Assess the degree of digestion every &#189; hour by observing 20 &#181;l suspension under hemocytometer.</li>
	<li>Allow the fragments to sediment for 5 min, then transfer the supernatant in a 15 ml conical polypropylene tube and centrifuge at 200 x g for 10 min at room temperature. Carefully decant off the supernatant and resuspend cells in 1 - 5 ml of mammosphere media.</li>
	<li>Follow the steps 1.1-1.4 described above for cell lines to obtain and plate single cell suspensions. Pass cells through the 25 G syringe a maximum of 2 times if necessary to limit damaging cells.</li>
</ol>
3. Mammosphere Forming Efficiency (%) Calculation
<ol>
	<li>After the culture period, count the mammospheres (greater than 40 &#181;m) diameter under a microscope at 40X magnification. Digitally image 5 random fields using a digital camera on a light microscope and determine the mammospheres size using the acquisition software. Use any Image Analysis Software.</li>
	<li>Calculate Mammosphere Forming Efficiency (MFE%) using the following equation: 
	MFE (%) = (# of mammospheres per well) / (# of cells seeded per well) x 100</li>
</ol>
4. Serial Passaging of Mammospheres for Assessment of Self-renewal
<ol>
	<li>Pipette the media containing the mammospheres from each well into a 15 ml tube. Wash the wells with PBS and add to the collected media. Centrifuge at 115 x g for 10 min at room temperature.</li>
	<li>Discard supernatant and resuspend the pellet in 500 &#181;l of pre-warmed 0.5% trypsin/0.2% EDTA. Incubate for 2-3 min.</li>
	<li>Add 500 &#181;l of FCS to neutralize trypsin. Centrifuge at 500 x g for 5 min. Discard supernatant and resuspend pellet in 100 &#181;l of mammospheres media, pipetting up and down to disaggregate spheres.</li>
	<li>Count cells with hemocytometer and determine if cells are in single cell suspension. If not pass through a 25 G syringe up to 3 times to obtain single cells. Seed the cells into a new ultra low-attachment 6-well plate at the same density used in the primary generation.</li>
	<li>After 5-10 days, count spheres &#62;40 &#181;m and calculate sphere-forming efficiency using the formula reported before.</li>
</ol>

<ol>
	<li>Iliopoulos, D., Hirsch, H. a., Struhl, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+epigenetic+switch+involving+NF-kappaB,+Lin28,+Let-7+MicroRNA,+and+IL6.">An epigenetic switch involving NF-kappaB, Lin28, Let-7 MicroRNA, and IL6.</a> Cell. 139 (4), 693-706 (2009).</li><li>Iliopoulos, D., Hirsch, H. a., Wang, G., Struhl, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inducible+formation+of+breast+cancer+stem+cells+and+their+dynamic+equilibrium+with+non-stem+cancer+cells+via+IL6+secretion.">Inducible formation of breast cancer stem cells and their dynamic equilibrium with non-stem cancer cells via IL6 secretion.</a> Proc Natl Acad Sci U S A. 108 (4), 1397-1402 (2011).</li><li>Visvader, J. E., Lindeman, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+stem+cells:+current+status+and+evolving+complexities.">Cancer stem cells: current status and evolving complexities.</a> Cell stem cell. 10 (6), 717-728 (2012).</li><li>Rosen, J. M., Jordan, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+increasing+complexity+of+the+cancer+stem+cell+paradigm.">The increasing complexity of the cancer stem cell paradigm.</a> Science. 324 (5935), 1670-1673 (2009).</li><li>Rokavec, M., Wu, W., Luo, J. -. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IL6-mediated+suppression+of+miR-200c+directs+constitutive+activation+of+inflammatory+signaling+circuit+driving+transformation+and+tumorigenesis.">IL6-mediated suppression of miR-200c directs constitutive activation of inflammatory signaling circuit driving transformation and tumorigenesis.</a> Mol Cell. 45 (6), 777-789 (2012).</li><li>Chen, J., Li, Y., 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=A+restricted+cell+population+propagates+glioblastoma+growth+after+chemotherapy.">A restricted cell population propagates glioblastoma growth after chemotherapy.</a> Nature. 488 (7412), 522-526 (2012).</li><li>Driessens, G., Beck, B., Caauwe, A., Simons, B. D., Blanpain, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defining+the+mode+of+tumour+growth+by+clonal+analysis.">Defining the mode of tumour growth by clonal analysis.</a> Nature. 488 (7412), 527-530 (2012).</li><li>Schepers, A. G., Snippert, H. 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=Lineage+tracing+reveals+Lgr5++stem+cell+activity+in+mouse+intestinal+adenomas.">Lineage tracing reveals Lgr5+ stem cell activity in mouse intestinal adenomas.</a> Science. 337 (6095), 730-735 (2012).</li><li>Sheridan, C., Kishimoto, H., 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=CD44+/CD24-+breast+cancer+cells+exhibit+enhanced+invasive+properties:+an+early+step+necessary+for+metastasis.">CD44+/CD24- breast cancer cells exhibit enhanced invasive properties: an early step necessary for metastasis.</a> Breast cancer research: BCR. 8 (5), R59 (2006).</li><li>Ginestier, C., Hur, M. H., 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=ALDH1+is+a+marker+of+normal+and+malignant+human+mammary+stem+cells+and+a+predictor+of+poor+clinical+outcome.">ALDH1 is a marker of normal and malignant human mammary stem cells and a predictor of poor clinical outcome.</a> Cell stem cell. 1 (5), 555-567 (2007).</li><li>Liu, S., Cong, Y., 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=Breast+Cancer+Stem+Cells+Transition+between+Epithelial+and+Mesenchymal+States+Reflective+of+their+Normal+Counterparts.">Breast Cancer Stem Cells Transition between Epithelial and Mesenchymal States Reflective of their Normal Counterparts.</a> Stem cell reports. 2 (1), 78-91 (2014).</li><li>Reynolds, B. A., Weiss, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+neurons+and+astrocytes+from+isolated+cells+of+the+adult+mammalian+central+nervous+system.">Generation of neurons and astrocytes from isolated cells of the adult mammalian central nervous system.</a> Science. 255 (5052), 1707-1710 (1992).</li><li>Pastrana, E., Silva-Vargas, V., Doetsch, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eyes+wide+open:+a+critical+review+of+sphere-formation+as+an+assay+for+stem+cells.">Eyes wide open: a critical review of sphere-formation as an assay for stem cells.</a> Cell stem cell. 8 (5), 486-498 (2011).</li><li>Dontu, G., Abdallah, W. 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=In+vitro+propagation+and+transcriptional+profiling+of+human+mammary+stem+/+progenitor+cells.">In vitro propagation and transcriptional profiling of human mammary stem / progenitor cells.</a> Genes Dev. , 1253-1270 (2003).</li><li>Ponti, D., Costa, 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=Isolation+and+in+vitro+propagation+of+tumorigenic+breast+cancer+cells+with+stem/progenitor+cell+properties.">Isolation and in vitro propagation of tumorigenic breast cancer cells with stem/progenitor cell properties.</a> Cancer Res. 65 (13), 5506-5011 (2005).</li><li>Grimshaw, M. J., Cooper, L., 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=Mammosphere+culture+of+metastatic+breast+cancer+cells+enriches+for+tumorigenic+breast+cancer+cells.">Mammosphere culture of metastatic breast cancer cells enriches for tumorigenic breast cancer cells.</a> Breast Cancer Res. 10 (3), R52 (2008).</li><li>Pham, P. V., Phan, N. L. 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=Differentiation+of+breast+cancer+stem+cells+by+knockdown+of+CD44:+promising+differentiation+therapy.">Differentiation of breast cancer stem cells by knockdown of CD44: promising differentiation therapy.</a> J Transl Med. 9 (1), 209 (2011).</li><li>Manuel Iglesias, J., Beloqui, I., 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=Mammosphere+formation+in+breast+carcinoma+cell+lines+depends+upon+expression+of+E-cadherin.">Mammosphere formation in breast carcinoma cell lines depends upon expression of E-cadherin.</a> PloS one. 8 (10), e77281 (2013).</li><li>Coles-Takabe, B. L. K., Brain, I., 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=Don&#8217;t+look:+growing+clonal+versus+nonclonal+neural+stem+cell+colonies.">Don&#8217;t look: growing clonal versus nonclonal neural stem cell colonies.</a> Stem Cells. 26 (11), 2938-2944 (2008).</li><li>Stingl, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+and+analysis+of+mammary+gland+stem+cells.">Detection and analysis of mammary gland stem cells.</a> J Pathol. 217 (2), 229-241 (2009).</li><li>Kreso, A., Dick, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+cancer+stem+cell+model.">Evolution of the cancer stem cell model.</a> Cell stem cell. 14 (3), 275-291 (2014).</li><li>Al-Hajj, M., Clarke, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-renewal+and+solid+tumor+stem+cells.">Self-renewal and solid tumor stem cells.</a> Oncogene. 23 (43), 7274-7282 (2004).</li><li>Yu, F., Yao, H., 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=let-7+regulates+self+renewal+and+tumorigenicity+of+breast+cancer+cells.">let-7 regulates self renewal and tumorigenicity of breast cancer cells.</a> Cell. 131 (6), 1109-1123 (2007).</li></ol>

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this article.

Successful assessment of primary and secondary mammospheres relies on cells being plated at sufficiently low densities that mammospheres form from single clones, with minimal sphere aggregation. However at densities that are too low, too few mammospheres may form to distinguish the effects of treatments statistically. Seeding density should be optimised for each cell line used since they can vary considerably in their sphere forming efficiencies (those expressing low E-cadherin may form less stable and shorter term mammo...

The existence of tumor cell lineages headed by stem-like cancer stem cells has greatly added to our understanding of tumor heterogeneity. While some phenotypic diversity in tumors does arise from the clonal outgrowth of genetically distinct clones, a substantial component appears to result from epigenetic differences: cancer cells can transition (sometimes reversibly) between stem, progenitor, and differentiated states via activation or repression of specific gene expression programs1&#8211;3. This may reflect cell intrinsic or extrinsic factors, reflecting the gene expression program currently being expressed in a cell with its resultant autocrine signalling in conjunction with paracrine signalling from neighboring cancer, stromal or immune cells delivering modulatory factors, and microenviromental conditions such as the degree of hypoxia2,4,5.
Although innovative lineage tracing approaches are advancing our ability to study putative cancer stem cells in their in vivo niche6&#8211;8, sphere-forming assays remain a popular and convenient approach to estimate breast cancer cells&#8217; potential to behave like stem cells, at least under the assay conditions used. It is often used alongside retrospective methods for purifying cancer stem cells, by their expression of membrane markers CD44 and CD249, and activity levels of the enzyme ALDH (aldehyde dehydrogenase)10, markers that have been proposed to correspond to more mesenchymal- and epithelial-like cancer stem cells respectively11. The sphere formation approach was first developed as the neurosphere assay, enabling the growth of putative stem cells from single clones in non-adherent, serum free conditions with the addition of epithelial growth factor (EGF)12, later being usefully applied to normal and cancerous breast tissues.
The identity of the sphere-forming founder cell, and the mixed cell types making up the sphere mass, are relevant for the inferences that can be made from mammo-, or other-sphere forming assays. Long-term quiescent bone fide stem cells, thought to rest in G0 phase, will not experience the precise combination of factors that would favor activation in vivo. The mammosphere assay instead enables the growth of cells either poised for mitotic division or already dividing13. These progenitors, although not a truly quiescent cell, may be the cell stage that proliferates with the EGF and basic fibroblast growth factor (bFGF) mitogens used in the assay. Nevertheless, they contain a range of activated stem cell-associated signalling pathways14. In addition, the rate of their formation relates to the tumorigenicity of the tissue they were taken from, when measured by their potency in limited dilution assays in mouse xenografts2,15,16.
Here we provide detailed protocols to isolate single cells and generate primary mammospheres from both human breast cancer cell lines and clinical samples of breast tumors. We also describe how to perform serial passages of primary mammospheres to assess self-renewal, and how to calculate sphere forming efficiency that allows comparison across different seeding densities (see scheme in Figure 1).

<table><tbody><tr><td>DMEM/F12</td><td>Lonza</td><td>CC-3151</td><td></td></tr><tr><td>2 mM L-glutamine</td><td>Sigma Aldrich</td><td>G8540</td><td></td></tr><tr><td>100 U/ml Penicillin &amp;amp; Streptomycin</td><td>Sigma Aldrich</td><td>P4083</td><td></td></tr><tr><td>20 ng/ml Recombinant human epidermal growth factor (EGF)</td><td>Sigma Aldrich</td><td>E9644</td><td></td></tr><tr><td>20 ng/ml Recombinant human basic fibroblast growth factor (bFGF)</td><td>R&amp;amp;D systems</td><td>233-FB-025</td><td></td></tr><tr><td>1x B27 supplement</td><td>Invitrogen</td><td>17504-044</td><td></td></tr><tr><td>Phosphate buffered saline (PBS)</td><td>Thermo Scientific</td><td>12399902</td><td></td></tr><tr><td>0.5% trypsin/0.2% EDTA</td><td>Sigma Aldrich</td><td>59418C</td><td></td></tr><tr><td>Fetal calf serum</td><td>First Link UK</td><td>02-00-850</td><td></td></tr><tr><td>Trypan blue</td><td>Sigma Aldrich</td><td>93595</td><td></td></tr><tr><td>Low attachment 6-well plates</td><td>Corning</td><td>CLS3814</td><td></td></tr><tr><td>Collagenase type 1A</td><td>Sigma Aldrich</td><td>C9891</td><td></td></tr><tr><td>Hyaluronidase</td><td>Sigma Aldrich</td><td>H3506</td><td></td></tr><tr><td>Sterile razor blades</td><td>Fisher Scientific</td><td>12443170</td><td></td></tr><tr><td>Sterile scalpel</td><td>Fisher Scientific</td><td>11758353</td><td></td></tr><tr><td>Sterile micro-dissecting scissors</td><td>Sigma Aldrich</td><td>S3146</td><td></td></tr></tbody></table>

mammosphere formation assay from human breast cancer tissues and cell lines

Similar to healthy tissues, many blood and solid malignancies are now thought to be organised hierarchically, with a subset of stem-like cancer cells that self-renew while giving rise to more differentiated progeny. Understanding and targeting these cancer stem cells in breast cancer, which may possess enhanced chemo- and radio-resistance compared to the non-stem tumor bulk, has become an important research area. Markers including CD44, CD24, and ALDH activity can be assessed using fluorescence activated cell sorting (FACS) to prospectively isolate cells that display enhanced tumorigenicity when implanted into immunocompromised mice: the mammosphere assay has also become widely used for its ability to retrospectively identify sphere-forming cells that develop from single stem cell-like clones. Here we outline approaches for the appropriate culturing of mammospheres from cell lines or primary patient samples, their passaging, and calculations to estimate sphere forming efficiency (SFE). First we discuss key considerations and pitfalls in the appropriate planning and interpretation of mammosphere experiments.

Different samples or those subjected to different treatments may vary in the number of mammospheres &gt;40 µm that form after normalizing for initial cells seeded. Calculate mammosphere forming efficiency (MFE) for each treatment grown in triplicate. This enables experiments with different seeding densities to be compared. Data is best displayed on a bar graph, ideally with positive and negative controls, and displaying the standard deviation across the triplicate wells. Consistently transfer adherent cells into non-adh...

Watch this Scientific Journal Video about Mammosphere Formation Assay from Human Breast Cancer Tissues and Cell Lines at JoVE.com

Mammosphere Formation Assay from Human Breast Cancer Tissues and Cell Lines

Floating mammosphere assays can investigate the subset of stem-like breast cancer cells that survive in suspension conditions and show enhanced tumorigenesis when implanted into mice. This protocol provides a convenient in vitro measure of sphere-forming ability, a proxy for in vivo tumorigenesis, while facilitating analysis of the stem-associated transcriptional landscape.

Similar to healthy tissues, many blood and solid malignancies are now thought to be organised hierarchically, with a subset of stem-like cancer cells that ...

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Medicine

33.2K Views.  Imperial College London. Floating mammosphere assays can investigate the subset of stem-like breast cancer cells that survive in suspension conditions and show enhanced tumorigenesis when implanted into mice. This protocol provides a convenient in vitro measure of sphere-forming ability, a proxy for in vivo tumorigenesis, while facilitating analysis of the stem-associated transcriptional landscape.

Video: Mammosphere Formation Assay from Human Breast Cancer Tissues and Cell Lines

Using Microarrays to Interrogate Microenvironmental Impact on Cellular Phenotypes in Cancer

Understanding the impact of the microenvironment on the phenotype of cells is a difficult problem due to the complex mixture of both soluble growth factors and matrix-associated proteins in the microenvironment in vivo. Furthermore, readily available reagents for the modeling of microenvironments in vitro typically utilize complex mixtures of proteins that are incompletely defined and suffer from batch to batch variability. The microenvironment microarray (MEMA) platform allows for the assessment of thousands of simple combinations of microenvironment proteins for their impact on cellular phenotypes in a single assay. The MEMAs are prepared in well plates, which allows the addition of individual ligands to separate wells containing arrayed extracellular matrix (ECM) proteins. The combination of the soluble ligand with each printed ECM forms a unique combination. A typical MEMA assay contains greater than 2,500 unique combinatorial microenvironments that cells are exposed to in a single assay. As a test case, the breast cancer cell line MCF7 was plated on the MEMA platform. Analysis of this assay identified factors that both enhance and inhibit the growth and proliferation of these cells. The MEMA platform is highly flexible and can be extended for use with other biological questions beyond cancer research.

The purpose of the method presented here is to show how microenvironment microarrays (MEMA) can be fabricated and used to interrogate the impact of thousands of simple combinatorial microenvironments on the phenotype of cultured cells.

Understanding the impact of the microenvironment on the phenotype of cells is a difficult problem due to the complex mixture of both soluble growth ...

Cancer Research

Differentiation of Mouse Breast Epithelial HC11 and EpH4 Cells

Cadherins play an important role in the regulation of cell differentiation as well as neoplasia. Here we describe the origins and methods of the induction of differentiation of two mouse breast epithelial cell lines, HC11 and EpH4, and their use to study complementary stages of mammary gland development and neoplastic transformation.
The HC11 mouse breast epithelial cell line originated from the mammary gland of a pregnant Balb/c mouse. It differentiates when grown to confluence attached to a plastic Petri dish surface in medium containing fetal calf serum and Hydrocortisone, Insulin and Prolactin (HIP medium). Under these conditions, HC11 cells produce the milk proteins &#946;-casein and whey acidic protein (WAP), similar to lactating mammary epithelial cells, and form rudimentary mammary gland-like structures termed &#34;domes&#34;.
The EpH4 cell line was derived from spontaneously immortalized mouse mammary gland epithelial cells isolated from a pregnant Balb/c mouse. Unlike HC11, EpH4 cells can fully differentiate into spheroids (also called mammospheres) when cultured under three-dimensional (3D) growth conditions in HIP medium. Cells are trypsinized, suspended in a 20% matrix consisting of a mixture of extracellular matrix proteins produced by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells, plated on top of a layer of concentrated matrix coating a plastic Petri dish or multiwell plate, and covered with a layer of 10% matrix-containing HIP medium. Under these conditions, EpH4 cells form hollow spheroids that exhibit apical-basal polarity, a hollow lumen, and produce &#946;-casein and WAP.
Using these techniques, our results demonstrated that the intensity of the cadherin/Rac signal is critical for the differentiation of HC11 cells. While Rac1 is necessary for differentiation and low levels of activated RacV12 increase differentiation, high RacV12 levels block differentiation while inducing neoplasia. In contrast, EpH4 cells represent an earlier stage in mammary epithelial differentiation, which is inhibited by even low levels of RacV12.

We describe techniques for differentiation induction of two breast epithelial lines, HC11 and EpH4. While both require fetal calf serum, insulin, and prolactin to produce milk proteins, EpH4 cells can fully differentiate into mammospheres in three-dimensional culture. These complementary models are useful for signal transduction studies of differentiation and neoplasia.

Cadherins play an important role in the regulation of cell differentiation as well as neoplasia. Here we describe the origins and methods of the induction ...

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

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

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

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

In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells

Tumorigenesis is a multi-step process in which cells acquire capabilities&#160;that allow their growth, survival, and dissemination under hostile conditions. Different tests seek to identify and quantify these hallmarks of cancerous cells; however, they often focus on a single aspect of cellular transformation and, in fact, multiple tests are required for their proper characterization. The purpose of this work is to provide researchers with a set of tools to assess cellular transformation in vitro from a broad perspective, thereby making it possible to draw sound conclusions.
A sustained proliferative signaling activation is the major feature of tumoral tissues and can be easily monitored under in vitro conditions by calculating the number of population doublings achieved over time. Besides, the growth of cells in 3D cultures allows their interaction with surrounding cells, resembling what occurs in vivo. This enables the evaluation of cellular aggregation and, together with immunofluorescent labeling of distinctive cellular markers, to obtain information on another relevant feature of tumoral transformation: the loss of proper organization. Another remarkable characteristic of transformed cells is their capacity to grow without attachment to other cells and to the extracellular matrix, which can be evaluated with the anchorage assay.
Detailed experimental procedures to evaluate cell growth rate, to perform immunofluorescent labeling of cell lineage markers in 3D cultures, and to test anchorage-independent cell growth in soft agar are provided. These methodologies are optimized for Breast Primary Epithelial Cells (BPEC) due to its relevance in breast cancer; however, procedures can be applied to other cell types after some adjustments.

This protocol provides experimental in vitro tools to evaluate the transformation of human mammary cells. Detailed steps to follow-up cell proliferation rate, anchorage-independent growth capacity, and distribution of cell lineages in 3D cultures with basement membrane matrix are described.

Tumorigenesis is a multi-step process in which cells acquire capabilities&#160;that allow their growth, survival, and dissemination under hostile ...

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 ...

Modeling Breast Cancer in Human Breast Tissue using a Microphysiological System

Breast cancer (BC) remains a leading cause of death for women. Despite more than $700 million invested in BC research annually, 97% of candidate BC drugs fail clinical trials. Therefore, new models are needed to improve our understanding of the disease. The NIH Microphysiological Systems (MPS) program was developed to improve the clinical translation of basic science discoveries and promising new therapeutic strategies. Here we present a method for generating MPS for breast cancers (BC-MPS). This model adapts a previously described approach of culturing primary human white adipose tissue (WAT) by sandwiching WAT between adipose-derived stem cell sheets (ASC)s. Novel aspects of our BC-MPS include seeding BC cells into non-diseased human breast tissue (HBT) containing native extracellular matrix, mature adipocytes, resident fibroblasts, and immune cells; and sandwiching the BC-HBT admixture between HBT-derived ASC sheets. The resulting BC-MPS is stable in culture ex vivo for at least 14 days. This model system contains multiple elements of the microenvironment that influence BC including adipocytes, stromal cells, immune cells, and the extracellular matrix. Thus BC-MPS can be used to study the interactions between BC and its microenvironment. 
We demonstrate the advantages of our BC-MPS by studying two BC behaviors known to influence cancer progression and metastasis: 1) BC motility and 2) BC-HBT metabolic crosstalk. While BC motility has previously been demonstrated using intravital imaging, BC-MPS allows for high-resolution time-lapse imaging using fluorescence microscopy over several days. Furthermore, while metabolic crosstalk was previously demonstrated using BC cells and murine pre-adipocytes differentiated into immature adipocytes, our BC-MPS model is the first system to demonstrate this crosstalk between primary human mammary adipocytes and BC cells in vitro.

This protocol describes the construction of an in vitro microphysiological system for studying breast cancer using primary human breast tissue with off the shelf materials.

Breast cancer (BC) remains a leading cause of death for women. Despite more than $700 million invested in BC research annually, 97% of candidate BC drugs ...

Mouse Mammary Epithelial Cells form Mammospheres During Lactogenic Differentiation

A phenotypic measure commonly used to determine the degree of lactogenic differentiation in mouse mammary epithelial cell cultures is the formation of dome shaped cell structures referred to as mammospheres 1. The HC11 cell line has been employed as a model system for the study of regulation of mammary lactogenic differentiation both in vitro and in vivo 2. The HC11 cells differentiate and synthesize milk proteins in response to treatment with lactogenic hormones. Following the growth of HC11 mouse mammary epithelial cells to confluence, lactogenic differentiation was induced by the addition of a combination of lactogenic hormones including dexamethasone, insulin, and prolactin, referred to as DIP. The HC11 cells induced to differentiate were photographed at times up to 120 hours post induction of differentiation and the number of mammospheres that appeared in each culture was enumerated. The size of the individual mammospheres correlates with the degree of differentiation and this is depicted in the images of the differentiating cells.

HC11 lactogenic differentiation can be characterized by the formation of domed structures referred to as mammospheres. The structures can be enumerated by phase contrast microscopy to aid in quantifying lactogenic differentiation.

A phenotypic measure commonly used to determine the degree of lactogenic differentiation in mouse mammary epithelial cell cultures is the formation of ...

Biology

Mammary Epithelial and Endothelial Cell Spheroids as a Potential Functional In vitro Model for Breast Cancer Research

Breast cancer is the leading cause of mortality in women. The growth of breast cancer cells and their subsequent metastasis is a key factor for its progression. Although the mechanisms involved in promoting breast cancer growth have been intensively studied using monocultures of breast cancer cells such as MCF-7 cells, the contribution of other cell types, such as vascular and lymphatic endothelial cells that are intimately involved in tumor growth, has not been investigated in depth. Cell-cell interaction plays a key role in tumor growth and progression. Neoangiogenesis, or the development of vessels, is essential for tumor growth, whereas the lymphatic system serves as a portal for cancer cell migration and subsequent metastasis. Recent studies provide evidence that vascular and lymphatic endothelial cells can significantly influence cancer cell growth. These observations imply a need for developing in vitro models that would more realistically reflect breast cancer growth processes in vivo. Moreover, restrictions in animal research require the development of ex vivo models to elucidate better the mechanisms involved.
This article describes the development of breast cancer spheroids composed of both breast cancer cells (estrogen receptor-positive MCF-7 cells) and vascular and/or lymphatic endothelial cells. The protocol describes a detailed step-by-step approach in creating dual-cell spheroids using two different approaches, hanging drop (gold standard and cheap) and 96-well U-bottom plates (expensive). In-depth instructions are provided for how to delicately pick up the formed spheroids to monitor growth by microscopic sizing and assessing viability using dead and live cell staining. Moreover, procedures to fix the spheroids for sectioning and staining with growth-specific antibodies to differentiate growth patterns in spheroids are delineated. Additionally, details for preparing spheroids with transfected cells and methods to extract RNA for molecular analysis are provided. In conclusion, this article provides in-depth instructions for preparing multi-cell spheroids for breast cancer research.

Mammary Epithelial and Endothelial Cell Spheroids as a Potential Functional In vitro Model for Breast Cancer Research

Crosstalk between mammary epithelial cells and endothelial cells importantly contributes to breast cancer progression, tumor growth, and metastasis. In this study, spheroids have been made from breast cancer cells together with vascular and/or lymphatic endothelial cells and demonstrate their applicability as an in vitro system for breast cancer research.

Breast cancer is the leading cause of mortality in women. The growth of breast cancer cells and their subsequent metastasis is a key factor for its ...

Quantification of Self-renewal in Murine Mammosphere Cultures

The mammary gland is characterized by extensive regeneration capacity, as it goes through massive hormonal changes throughout the life cycle of a female. The role of mammary stem cells (MaSCs) is widely studied both in the physiological/developmental context and with regards to breast carcinogenesis. In this aspect, ex vivo studies focused on MaSC properties are highly sought after. Mammosphere cultures represent a surrogate of organ formation and have become a valuable tool for both basic and translational research. Here, we present a detailed protocol for the generation of murine primary mammosphere cultures and the quantitation of MaSC growth properties. The protocol includes mammary gland collection and digestion, isolation of primary mammary epithelial cells (MECs), establishment of primary mammosphere cultures, serial passaging, quantitation of mammosphere growth parameters and interpretation of the results. As an example, we present the effect of low-level constitutive Myc expression on normal MECs leading to increased self-renewal and proliferation.

Here, we describe the implementation and interpretation of the results of an in vitro mammosphere self-renewal quantitative assay.

The mammary gland is characterized by extensive regeneration capacity, as it goes through massive hormonal changes throughout the life cycle of a female. ...

Developmental Biology

Non-enzymatic, Serum-free Tissue Culture of Pre-invasive Breast Lesions for Spontaneous Generation of Mammospheres

Breast ductal carcinoma in situ (DCIS), by definition, is proliferation of neoplastic epithelial cells within the confines of the breast duct, without breaching the collagenous basement membrane. While DCIS is a non-obligate precursor to invasive breast cancers, the molecular mechanisms and cell populations that permit progression to invasive cancer are not fully known. To determine if progenitor cells capable of invasion existed within the DCIS cell population, we developed a methodology for collecting and culturing sterile human breast tissue at the time of surgery, without enzymatic disruption of tissue.
Sterile breast tissue containing ductal segments is harvested from surgically excised breast tissue following routine pathological examination. Tissue containing DCIS is placed in nutrient rich, antibiotic-containing, serum free medium, and transported to the tissue culture laboratory. The breast tissue is further dissected to isolate the calcified areas. Multiple breast tissue pieces (organoids) are placed in a minimal volume of serum free medium in a flask with a removable lid and cultured in a humidified CO2 incubator. Epithelial and fibroblast cell populations emerge from the organoid after 10 - 14 days. Mammospheres spontaneously form on and around the epithelial cell monolayer. Specific cell populations can be harvested directly from the flask without disrupting neighboring cells. Our non-enzymatic tissue culture system reliably reveals cytogenetically abnormal, invasive progenitor cells from fresh human DCIS lesions.

Primary cell culture using intact tissue organoids provides a model system that mimics the multi-cellular in vivo microenvironment. We developed a serum-free primary breast epithelium tissue culture model that perpetuates mixed cell culture lineages and exhibits differentiated morphology, without enzymatic tissue disruption. Breast organoids remain viable for &#62;6 months.

Breast ductal carcinoma in situ (DCIS), by definition, is proliferation of neoplastic epithelial cells within the confines of the breast duct, without ...

Mammosphere Formation Assay from Human Breast Cancer Tissues and Cell Lines

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Using Microarrays to Interrogate Microenvironmental Impact on Cellular Phenotypes in Cancer

Differentiation of Mouse Breast Epithelial HC11 and EpH4 Cells

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

In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells

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

Modeling Breast Cancer in Human Breast Tissue using a Microphysiological System

Mouse Mammary Epithelial Cells form Mammospheres During Lactogenic Differentiation

Mammary Epithelial and Endothelial Cell Spheroids as a Potential Functional In vitro Model for Breast Cancer Research

Quantification of Self-renewal in Murine Mammosphere Cultures

Non-enzymatic, Serum-free Tissue Culture of Pre-invasive Breast Lesions for Spontaneous Generation of Mammospheres