Name: in vitro evaluation of oncogenic transformation in human mammary epithelial cells
Uploaded: 2020-09-24T14:30:00
Description: Watch this Scientific Journal Video about In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells at JoVE.com

The AG laboratory is funded by the Spanish Nuclear Safety Council. T.A. and A.G. are members of a research group recognized by Generalitat de Catalunya (2017-SGR-503). MT holds a contract funded by the Scientific Foundation Asociaci&#243;n Espa&#241;ola Contra el C&#225;ncer [AECC-INVES19022TERR]. G.F. contract is funded by a grant from Cellex Foundation.

Human samples used in the following experiments were obtained from reduction mammoplasties carried out at Cl&#237;nica Pilar Sant Jordi (Barcelona) under standard procedure consent. All procedures are performed in a Class II Biological Safety Cabinet unless otherwise stated.
1. In vitro culture of human mammary epithelial cells and growth curve plot build-up
<ol>
	<li>In vitro culture of breast primary epithelial cells (BPECs): cell passaging 
	NOTE: For BPEC d...

<ol>
	<li>Hanahan, D., Weinberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hallmarks+of+cancer:+the+next+generation.">Hallmarks of cancer: the next generation.</a> Cell. 144 (5), 646-674 (2011).</li><li>Stampfer, M. R., Yaswen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culture+models+of+human+mammary+epithelial+cell+transformation.">Culture models of human mammary epithelial cell transformation.</a> Journal of Mammary Gland Biology and Neoplasia. 5 (4), 365-378 (2000).</li><li>Schinzel, A. C., Hahn, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oncogenic+transformation+and+experimental+models+of+human+cancer.">Oncogenic transformation and experimental models of human cancer.</a> Frontiers in Bioscience : A Journal and Virtual Library. 13 (13), 71 (2008).</li><li>Balani, S., Nguyen, L. V., Eaves, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+the+process+of+human+tumorigenesis.">Modeling the process of human tumorigenesis.</a> Nature Communications. 8 (1), 15422 (2017).</li><li>Bray, F., 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=Global+cancer+statistics+2018:+GLOBOCAN+estimates+of+incidence+and+mortality+worldwide+for+36+cancers+in+185+countries.">Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries.</a> CA: A Cancer Journal for Clinicians. 68 (6), 394-424 (2018).</li><li>Ince, T. 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=Transformation+of+different+human+breast+epithelial+cell+types+leads+to+distinct+tumor+phenotypes.">Transformation of different human breast epithelial cell types leads to distinct tumor phenotypes.</a> Cancer Cell. 12 (2), 160-170 (2007).</li><li>Repull&#233;s, 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=Radiation-induced+malignant+transformation+of+preneoplastic+and+normal+breast+primary+epithelial+cells.">Radiation-induced malignant transformation of preneoplastic and normal breast primary epithelial cells.</a> Molecular Cancer Research. , 1-13 (2019).</li><li>Weigelt, B., Bissell, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unraveling+the+microenvironmental+influences+on+the+normal+mammary+gland+and+breast+cancer.">Unraveling the microenvironmental influences on the normal mammary gland and breast cancer.</a> Seminars in Cancer Biology. 18 (5), 311-321 (2008).</li><li>Paoli, P., Giannoni, E., Chiarugi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anoikis+molecular+pathways+and+its+role+in+cancer+progression.">Anoikis molecular pathways and its role in cancer progression.</a> Biochimica et Biophysica Acta. 1833 (12), 3481-3498 (2013).</li><li>Debnath, J., Muthuswamy, S. K., Brugge, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphogenesis+and+oncogenesis+of+MCF-10A+mammary+epithelial+acini+grown+in+three-dimensional+basement+membrane+cultures.">Morphogenesis and oncogenesis of MCF-10A mammary epithelial acini grown in three-dimensional basement membrane cultures.</a> Methods. 30 (3), 256-268 (2003).</li><li>Borowicz, 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=The+soft+agar+colony+formation+assay.">The soft agar colony formation assay.</a> Journal of Visualized Experiments. (92), (2014).</li><li>Schindelin, 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=Fiji:+an+open-source+platform+for+biological-image+analysis.">Fiji: an open-source platform for biological-image analysis.</a> Nature Methods. 9 (7), 676-682 (2012).</li><li>Brocher, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+BioVoxxel+Image+Processing+and+Analysis+Toolbox.">The BioVoxxel Image Processing and Analysis Toolbox.</a> European BioImage Analysis Symposium. 8 (2), 67112 (2015).</li><li>Torquato, S., Truskett, T. M., Debenedetti, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+random+close+packing+of+spheres+well+defined.">Is random close packing of spheres well defined.</a> Physical Review Letters. 84 (10), 2064-2067 (2000).</li><li>LaBarge, M. A., Garbe, J. C., Stampfer, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Processing+of+human+reduction+mammoplasty+and+mastectomy+tissues+for+cell+culture.">Processing of human reduction mammoplasty and mastectomy tissues for cell culture.</a> Journal of Visualized Experiments. (71), (2013).</li><li>Zubeldia-Plazaola, 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=Glucocorticoids+promote+transition+of+ductal+carcinoma+in+situ+to+invasive+ductal+carcinoma+by+inducing+myoepithelial+cell+apoptosis.">Glucocorticoids promote transition of ductal carcinoma in situ to invasive ductal carcinoma by inducing myoepithelial cell apoptosis.</a> Breast Cancer Research. 20 (1), 65 (2018).</li></ol>

The experimental protocols described in this paper provide useful tools to assess the oncogenic transformation of in vitro cultured cells. Each technique evaluates specific aspects of the transformation process, and thus, special attention must be paid when drawing conclusions from a single analysis. Growth curves build-up is an approach that demands information already available when culturing cells for other purposes. That makes this technique cheaper and easier to apply compared to other cell proliferation assays. How...

Multiple successive events are required for neoplasm development. In 2011, Hanahan and Weinberg described 10 capabilities that enable transformed cells&#8217; growth, survival, and dissemination: the so-called &#8220;Hallmarks of Cancer&#8221;1. The methodology described here compiles three different tools to evaluate in vitro cellular transformation by focusing on some of the tumoral cells&#8217; distinctive features. These techniques assess the cell proliferation rate, the behavior of cells when cultured in 3D and their capacity to form colonies with anchorage independence.
Cell models are crucial to test hypothesis in vitro. Different approaches have been developed to generate experimental models of cellular transformation for the study of cancer2,3,4. Since breast cancer is the most common cancer among women worldwide and is responsible for approximately 15% of cancer deaths&#160;among women5, providing suitable cellular models of mammary epithelial cells is of utmost importance for further investigation. In this article, we have illustrated the potential of three techniques to evaluate cellular transformation using an experimental model of Breast Primary Epithelial Cells (BPECs) transformation initially described by Ince and colleagues in 20076 and later implemented in our laboratory7. This experimental model is based on the sequential alteration of three targeted genes (SV40 Large T and small t antigens herein referred to as Ttag, hTERT, and HRAS) to the genome of non-transformed BPECs. Moreover, the method used for BPECs derivation favors the maintenance of mammary epithelial cells with luminal or myoepithelial markers, resulting in a heterogeneous cell culture that retains some of the mammary gland physiological traits.
In the mammary gland, luminal mammary epithelial cells, which are responsible for milk production, are located near the lumen, whereas myoepithelial cells are disposed around luminal cells and take care of contraction movements leading the milk to the nipple. The loss of proper organization between these cell lineages is a feature of tumoral transformation8 that can be assessed in vitro after immunofluorescent detection of distinctive lineage markers in 3D cell cultures. Another major characteristic of tumoral cells is their capacity to grow without attachment to other cells and to the extracellular matrix1. When healthy cells are forced to grow in suspension, mechanisms such as anoikis &#8210; a type of cell death induced in response to detachment from the extracellular matrix &#8210; are activated9. The evasion of cell death is one of the distinctive hallmarks of cancer and thus, transformed cells are capable to inactivate anoikis and survive in an anchor-independent manner. This capacity can be evaluated in vitro with the anchorage-independent assay using soft agar. Furthermore, an inherent feature of tumoral tissues is their sustained proliferative signaling capacity, which can be easily monitored under in vitro conditions by measuring the increase of cell number along time, not only in suspension assays but also by monitoring the growth rate of monolayer adherent cultures.
Despite the best model to test tumorigenic potential is the inoculation of tumoral cells in murine models and evaluation of tumor development in situ, it is important to minimize the number of animals employed in experimental procedures as much as possible. Therefore, having suitable tests to assess transformation in vitro is a top priority. Here, we provide a set of tools to evaluate the tumorigenic potential of partially and fully transformed breast epithelial cells that can be easily implemented in most of the laboratories that work with cellular transformation models.

<table>
	<tbody>
		<tr>
			<td>1 ml Serological Pipettes</td>
			<td>Labclinics</td>
			<td>PLC91001</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml Eppendorfs</td>
			<td>Thermo Fisher Scientific</td>
			<td>3451</td>
			<td>Dark eppendorfs are preferred for MTT long-term storage</td>
		</tr>
		<tr>
			<td>10 &#956;l Pipette tips w/o filter</td>
			<td>Biologix</td>
			<td>20-0010</td>
			<td></td>
		</tr>
		<tr>
			<td>100 ml glass bottle</td>
			<td></td>
			<td></td>
			<td>With cap, autoclavable</td>
		</tr>
		<tr>
			<td>1000 &#956;l Pipette tips w/ filter</td>
			<td>Labclinics</td>
			<td>LAB1000ULFNL</td>
			<td></td>
		</tr>
		<tr>
			<td>1000 &#956;l Pipette tips w/o filter</td>
			<td>Biologix</td>
			<td>20-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>15 ml Conical tubes</td>
			<td>VWR</td>
			<td>525-0400</td>
			<td></td>
		</tr>
		<tr>
			<td>2 ml Serological Pipettes</td>
			<td>Labclinics</td>
			<td>PLC91002</td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#956;l Pipette tips w/ filter</td>
			<td>Labclinics</td>
			<td>FTR200-96</td>
			<td></td>
		</tr>
		<tr>
			<td>5 ml Serological Pipettes</td>
			<td>Labclinics</td>
			<td>PLC91005</td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml Conical Tubes</td>
			<td>VWR</td>
			<td>525-0304</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>PanReac AppliChem</td>
			<td>211007</td>
			<td>Used for 3D structure fixation prior to immunofluorescent labelling</td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Sigma-Aldrich</td>
			<td>A1296</td>
			<td>Used for anchorage assay</td>
		</tr>
		<tr>
			<td>Anti-Claudin 4 antibody</td>
			<td>Abcam</td>
			<td>15104, RRID:AB_301650</td>
			<td>Working dilution 1:100, host: rabbit</td>
		</tr>
		<tr>
			<td>Anti-Cytokeratin 14 [RCK107] antibody</td>
			<td>Abcam</td>
			<td>9220, RRID:AB_307087</td>
			<td>Working dilution 1:100, host: mouse</td>
		</tr>
		<tr>
			<td>Anti-mouse Cyanine Cy3 antibody</td>
			<td>Jackson ImmunoResearch Inc.</td>
			<td>115-165-146, RRID:AB_2338690</td>
			<td>Working dilution 1:500, host: goat</td>
		</tr>
		<tr>
			<td>Anti-rabbit Alexa Fluor 488 antibody</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-11034, RRID:AB_2576217</td>
			<td>Working dilution 1:500, host: goat</td>
		</tr>
		<tr>
			<td>Autoclave</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BioVoxxel Toolbox</td>
			<td></td>
			<td>RRID:SCR_015825</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture 24-well Plate</td>
			<td>Labclinics</td>
			<td>PLC30024</td>
			<td>Used for 3D cultures in Matrigel. Flat Bottom</td>
		</tr>
		<tr>
			<td>Cell culture 6-well Plate</td>
			<td>Labclinics</td>
			<td>PLC30006</td>
			<td>Used for anchorage assay</td>
		</tr>
		<tr>
			<td>Cell incubator (37 &#186;C and 5 % CO2)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Strainers</td>
			<td>Fisherbrand</td>
			<td>11587522</td>
			<td>Mesh size: 40 &#956;m</td>
		</tr>
		<tr>
			<td>CellSense software</td>
			<td>Olympus</td>
			<td></td>
			<td>Used to image acquisition</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cholera Toxin from Vibrio cholerae</td>
			<td>Sigma-Aldrich</td>
			<td>C8052</td>
			<td>Used to supplement cell culture medium</td>
		</tr>
		<tr>
			<td>Class II Biological Safety Cabinet</td>
			<td>Herasafe</td>
			<td>HAEREUS HS12</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal inverted Microscope</td>
			<td>Leica</td>
			<td>TCS SP5</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover glasses</td>
			<td>Witeg Labortechnik GmbH</td>
			<td>4600122</td>
			<td>22 X 22 mm, thickness 0.13 - 0.17 mm</td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td></td>
			<td></td>
			<td>2-(4-amidinophenyl)-1H -indole-6-carboxamidine</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Biowest</td>
			<td>S1810</td>
			<td>Used to inactivate trypsine action</td>
		</tr>
		<tr>
			<td>Fiji software (ImageJ)</td>
			<td>National Institutes of Health</td>
			<td>RRID:SCR_002285</td>
			<td>Free download, no license needed</td>
		</tr>
		<tr>
			<td>Glass Pasteur Pipettes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass slides</td>
			<td>Fisherbrand</td>
			<td>11844782</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Serum</td>
			<td>Biowest</td>
			<td>S2000</td>
			<td>Used for immunofluorescence of 3D structures</td>
		</tr>
		<tr>
			<td>Heat-Resistant Gloves</td>
			<td></td>
			<td></td>
			<td>Used for agar manipulation after autoclave</td>
		</tr>
		<tr>
			<td>Heater bath (37 &#186;C)</td>
			<td></td>
			<td></td>
			<td>Used to temper solutions prior to cell subculture</td>
		</tr>
		<tr>
			<td>Heater bath (42 &#186;C)</td>
			<td></td>
			<td></td>
			<td>Used to keep agar warm</td>
		</tr>
		<tr>
			<td>Heating plate</td>
			<td></td>
			<td></td>
			<td>Used for Matrigel dehydration</td>
		</tr>
		<tr>
			<td>Humid chamber</td>
			<td></td>
			<td></td>
			<td>Used for the incubation of antibodies during immunofluorescence</td>
		</tr>
		<tr>
			<td>Ice</td>
			<td></td>
			<td></td>
			<td>Used during Matrigel manipulation</td>
		</tr>
		<tr>
			<td>Ice-box</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted Optic Microscope</td>
			<td>Olympus</td>
			<td>IX71</td>
			<td></td>
		</tr>
		<tr>
			<td>Matrigel Matrix</td>
			<td>Becton Dickinson</td>
			<td>354234</td>
			<td>Store at -20 &#186;C and keep cold when in use. Referred to as basement membrane matrix</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>PanReac AppliChem</td>
			<td>131091</td>
			<td>Used for 3D structure fixation prior to immunofluorescent labelling</td>
		</tr>
		<tr>
			<td>Micropipette</td>
			<td></td>
			<td></td>
			<td>p1000, p200 and p10</td>
		</tr>
		<tr>
			<td>Microsoft Office Excel</td>
			<td>Microsoft</td>
			<td>RRID:SCR_016137</td>
			<td>Used to calculate population doubling and to obtain growth rate equation</td>
		</tr>
		<tr>
			<td>MilliQ water</td>
			<td></td>
			<td></td>
			<td>Referred to as ultrapure water</td>
		</tr>
		<tr>
			<td>Nail Polish</td>
			<td></td>
			<td></td>
			<td>Used to seal samples after mounting</td>
		</tr>
		<tr>
			<td>Parafilm M</td>
			<td>Bemis</td>
			<td>PM-999</td>
			<td>Used to cover antibody solution during incubation</td>
		</tr>
		<tr>
			<td>PBS pH 7.4 (w/o calcium &#38; magnesium)</td>
			<td>Gibco</td>
			<td>10010-056</td>
			<td>Sterile. Used for cell subculture</td>
		</tr>
		<tr>
			<td>PBS tablets</td>
			<td>Sigma-Aldrich</td>
			<td>P4417</td>
			<td>Dilute in milliQ water. No sterility required. Used for immunofluorescence</td>
		</tr>
		<tr>
			<td>Pipette Aid</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Primaria T25 flasks</td>
			<td>Corning</td>
			<td>353808</td>
			<td>Used for BPEC culture</td>
		</tr>
		<tr>
			<td>Scepter Automated Cell Counter</td>
			<td>Millipore</td>
			<td>PHCC20060</td>
			<td>Alternatively, use an haemocytometer</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td></td>
			<td></td>
			<td>Used to cut pipette tips and parafilm</td>
		</tr>
		<tr>
			<td>Sterile filters 0.22 &#956;m</td>
			<td>Millipore</td>
			<td>SLGP033RS</td>
			<td>Used to filter MTT solution</td>
		</tr>
		<tr>
			<td>Thiazolyl Blue Tetrazolium Bromide (MTT)</td>
			<td>Sigma-Aldrich</td>
			<td>M2128</td>
			<td>Store at -20 &#186;C</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td>Used for immunofluorescence of 3D structures</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA 10X</td>
			<td>Biowest</td>
			<td>X0930</td>
			<td>Dilute in PBS to obtain 3X solution</td>
		</tr>
		<tr>
			<td>Vectashield Antifade Mounting Medium</td>
			<td>Vector Laboratories</td>
			<td>H-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>WIT-P-NC Culture Medium</td>
			<td>Stemgent</td>
			<td>00-0051</td>
			<td>Used for primary BPEC culture</td>
		</tr>
		<tr>
			<td>WIT-T Culture Medium</td>
			<td>Stemgent</td>
			<td>00-0047</td>
			<td>Used for transformed BPEC culture</td>
		</tr>
	</tbody>
</table>

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.

An experimental model of cellular transformation with the introduction of three genetic elements in BPECs was chosen to generate representative results of oncogenic transformation6,7 (Figure 3). Non-transformed BPECs (N) were derived from disease-free breast tissue as described by Ince and colleagues6 and cultured following the protocol indicated here. After overcoming STASIS (stress ...

Watch this Scientific Journal Video about In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells at JoVE.com

In Vitro Evaluation of Oncogenic Transformation in Human Mammary Epithelial Cells

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 ...

This methodology uses the integration of different indicators to assess the degree of transformation of any cell model. This technique provides researchers with a set of time-consuming but simple-to-use tools for assessing cell transformation in vitro. This allows the method to be used in most laboratories.Demonstrating the procedure will be Teresa Anglada, a post-doctoral researcher from my laboratory, and Joan Repulles, a microscopy specialist. When the breast primary epithelial cell culture reaches 90%confluency, transfer the supernatant from the culture flask to a 15 milliliter tube containing two milliliters of fetal bovine serum and wash the cells with PBS. Treat the cells with one milliliter of trypsin for five minutes at 37 degrees Celsius.When the cells have detached, inactivate the trypsin with the reserved medium and collect the cells by centrifugation. Flick the tube to resuspend the pellet and add one to two milliliters of fresh medium for counting. After determining the cell concentration, add 300, 000 cells to a new tube and bring the final volume to five milliliters with additional fresh culture medium.Seed cells into a new T25 flask and return the cells to the cell culture incubator. Then use the formula to calculate the number of accumulated population doublings. To assess the proliferation rate of the cells, plot the accumulated number of population doublings for a specific time interval.An increased slope indicates an increased cell proliferation rate. To set up a 3D cell culture, rinse wells with a 1.9 square centimeter surface area with cold sterile PBS and coat the bottom of each well with 100 microliters of basement membrane matrix. Then place the plate in the cell culture incubator for about 20 minutes to allow the matrix to solidify.In the meantime, harvest mammary cells as just demonstrated and dilute the cells to a 400, 000 cells per milliliter of medium concentration. Mix the cells with fresh medium supplemented with 8%basement membrane matrix at a one-to-one ratio and add 500 microliters of the cells to each well of solidified matrix. Incubate the cells at 37 degrees Celsius for a few minutes, then add 500 microliters of medium supplemented with 4%basement membrane matrix to each well.Place the cells in the cell culture incubator for 14 days. The seeded cells will group and proliferate forming acini-like structures. For the immunofluorescent protein detection in the 3D cultured mammary cells, use a cutoff P200 pipette tip to remove the basement membrane matrix from each well and smear approximately 50 microliters of disaggregated matrix from each well onto individual glass slides.When the samples have completely dried, fix the cells with a one-to-one methanol-acetone solution at minus 20 degrees Celsius for 30 minutes. After fixing, block samples with blocking solution for two hours at room temperature. At the end of the incubation, add 30 microliters of the primary antibody working solution of interest and cover the slides with a strip of laboratory wrapping film for an overnight incubation at four degrees Celsius in a humid chamber.The next morning, wash the slides three times with PBS for one hour per wash and label the samples with the appropriate secondary antibody solution as just demonstrated. At the end of the incubation, wash the samples two times in PBS for two hours per wash before counter-staining with DAPI diluted in anti-fade mounting medium and covering each slide with a coverslip. Then analyze the fluorescent signal distribution for each acinus on a confocal microscope.To perform an anchorage-independent assay, first cover the bottom of the appropriate number of wells of a six-well plate with 1.5 milliliters of 0.6%agar in medium solution and let the agar solidify at room temperature. Next, prepare a five times 10 to the fourth cells per milliliter solution as demonstrated and filter the cells through a 40 micron strainer into a sterile 50 milliliter tube. Holding the tube at a 45 degree angle, add an equal volume of 0.6%agar in medium solution down the wall of the tube.And after thorough mixing, layer one milliliter of the cells in agar suspension to each well of the previously prepared six-well plate. Use an inverted microscope to confirm that the cells have been homogeneously dispersed throughout the agar. When the agar has completely solidified, carefully add one milliliter refresh medium to each well without disturbing the agar and incubate the cells for three weeks, changing the medium twice per week.At the end of the colony formation period, replace the medium with one milliliter of one milligram per milliliter MTT per well for a 24-hour incubation in the cell culture incubator. The next day, remove the MTT from each well and acquire images of each well on the inverted microscope. When all of the images have been acquired, open the images in ImageJ and click image, adjust, threshold, and apply to obtain a binary mask through thresholding of the original image.When well-delimited colonies have been obtained, select plugins and biovoxxel to launch the extended particle analyzer to identify the MTT-positive colonies. Over a specific interval of time, partially and fully transformed cells achieve a higher number of population doublings compared to non-transformed cells, indicating that the cell division rate is increased with the transformation process. Over the two-week 3D cell culture period, the cells aggregate and proliferate, increasing the acini size.The proper polarization of each acinus can be accurately assessed using protein immunofluorescent detection in conjunction with three-dimensional signal location by confocal microscopy. While all of the acini formed by non-transformed breast cells are properly organized, a loss of polarization is observed in acini formed by partially and fully transformed cells. After three weeks of embedded agar culture, cells with an anchorage independent growth capacity give rise to colonies composed of multiple cells.Only metabolically active cells are capable of cleaving the tetrazolium MTT ring, resulting in purple MTT formazan crystals after 24 hours. Measurement of the colony diameter by automatic image analysis allows the filtering of low proliferative colonies or individual cells. The number of colonies formed by non-transformed cells is negligible compared to those from partially and fully transformed cells.Colony size can also be used to discriminate between cells with different degrees of transformation. These assays can be used to screen cell lines prior to any inoculation as only those cell lines that have tested positive in vitro should be inoculated into mice.

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