We thank Virginie Ory, PhD for helpful discussions and advice on the approach of the 3D co-culture model. We also thank Elizabeth Jones for excellent technical assistance with the IHC sectioning. This study was supported by grants from the DFG (Deutsche Forschungsgemeinschaft) to YL (LI 2547/4-1) and the National Institutes of Health to AW (R01 CA231291), to ATR (R01 CA205632), to GWP (R01 CA218670), and the Core Grant of the Cancer Center (P30 CA51008).

A list and explanation of some frequently used words throughout the protocol can be found in Supplementary File 1.
1. Generation of spheroids
<ol>
	<li>Prepare and autoclave 2% agarose in 1x PBS (e.g., 1 g agarose in 50 mL of 1x PBS) and autoclave 35- and 81-microwell rubber molds. 
	CAUTION: Avoid using low-melting agarose for generating the agarose casts for IHC processing.</li>
	<li>Prepare agarose casts 
	NOTE: 35-microwell casts are used for invasion, immunofl...

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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=Development+of+a+Novel+3D+Tumor-tissue+Invasion+Model+for+High-throughput,+High-content+Phenotypic+Drug+Screening.">Development of a Novel 3D Tumor-tissue Invasion Model for High-throughput, High-content Phenotypic Drug Screening.</a> Scientific Reports. 8 (1), 13039 (2018).</li><li>Jenkins, R. 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=Ex+Vivo+Profiling+of+PD-1+Blockade+Using+Organotypic+Tumor+Spheroids.">Ex Vivo Profiling of PD-1 Blockade Using Organotypic Tumor Spheroids.</a> Cancer Discovery. 8 (2), 196-215 (2018).</li><li>Berens, E. B., Holy, J. M., Riegel, A. T., Wellstein, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Cancer+Cell+Spheroid+Assay+to+Assess+Invasion+in+a+3D+Setting.">A Cancer Cell Spheroid Assay to Assess Invasion in a 3D Setting.</a> Journal of Visualized Experiments. 20 (105), (2015).</li><li>Shoval, 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=Tumor+cells+and+their+crosstalk+with+endothelial+cells+in+3D+spheroids.">Tumor cells and their crosstalk with endothelial cells in 3D spheroids.</a> Scientific Reports. 7 (1), 10428 (2017).</li><li>Giannattasio, 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=Cytotoxicity+and+infiltration+of+human+NK+cells+in+in+vivo-like+tumor+spheroids.">Cytotoxicity and infiltration of human NK cells in in vivo-like tumor spheroids.</a> BioMed Central Cancer. 3 (15), 351 (2015).</li><li>Friedl, P., Wolf, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumour-cell+invasion+and+migration:+diversity+and+escape+mechanisms.">Tumour-cell invasion and migration: diversity and escape mechanisms.</a> Nature Reviews Cancer. 3 (5), 362-374 (2003).</li><li>McLennan, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+crest+migration+is+driven+by+a+few+trailblazer+cells+with+a+unique+molecular+signature+narrowly+confined+to+the+invasive+front.">Neural crest migration is driven by a few trailblazer cells with a unique molecular signature narrowly confined to the invasive front.</a> Development. 142 (11), 2014-2025 (2015).</li><li>Coffey, A., Johnson, M. 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(99), e52868 (2015).</li><li>Brenner, 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=Differential+inhibition+of+renal+cancer+cell+invasion+mediated+by+fibronectin,+collagen+IV+and+laminin.">Differential inhibition of renal cancer cell invasion mediated by fibronectin, collagen IV and laminin.</a> Cancer Letters. 155 (2), 199-205 (2000).</li><li>Farhat, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+Extraction+from+Collagen+Gels+Using+Qiagen's+RNeasy+Kit.">RNA Extraction from Collagen Gels Using Qiagen's RNeasy Kit.</a> The Protocol Place. 2012, (2019).</li><li>Foty, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+hanging+drop+cell+culture+protocol+for+generation+of+3D+spheroids.">A simple hanging drop cell culture protocol for generation of 3D spheroids.</a> Journal of Visualized Experiments. 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The authors declare that they have no competing financial interests.

The method presented here describes 3D tumor spheroid generation, which allows co-culture with T-cells, cell-based functional and molecular assays, as well as a variety of monitoring and analysis possibilities using a single device. The major advantage of our approach is that it does not necessitate transfer of the 3D culture to a separate assay and maintains the integrity of the 3D culture throughout the assays.
The workflow presented here can be modified as needed. The incubation times for s...

Despite significant improvements in cancer immunotherapy over the past decade, our mechanistic understanding of sensitivity and resistance to treatments are still fairly poor1. It is well-established that tumors display substantial heterogeneity, and that the dynamic interactions of the tumor cells with their microenvironment as well as with the immune cells, impact tumor cell death, invasive behavior and response to treatments that include immunotherapy1,2,3. As one arm of the adaptive immune system, T-cells execute cell-specific cytotoxicity. The analysis of T-cell recognition and response to cancer cells provides mechanistic insights into resistance and sensitivity to immune modulatory treatments.
In vitro modeling and monitoring interactions between cancer and T-cells in an appropriate environment has been challenging and so far, resulted in limited mechanistic insights. Most cell-based assays rely on a two-dimensional (2D) environment, that lacks key features that are critical for recapitulating the three-dimensional (3D) in vivo physiology4,5,6, namely spatial cell-cell interactions, contact with the extracellular matrix (ECM)7, dynamic metabolic demand, increased hypoxia due to mass growth8, and effects of the tumor microenvironment (TME)9. On the other hand, there are still a number of shortcomings with the currently used three-dimensional (3D) co-culture and invasion assay systems: (1) the time consuming nature of spheroid generation and harvest5,10, (2) the lack of control over spheroid size, shape and cell density11,12, (3) the low-throughput type assays, (4) the requirement for special equipment13,14, (5) the need to transfer the co-culture into distinct environments for different assays15,16,17. In particular, transferring of a co-culture assay often leads to disruption of spheroids and loss of the co-culture integrity. This applies especially for &#8220;loose&#8221; spheroids with reduced cell-cell adhesion. For example, most 3D invasion assays require that spheroids are harvested after their initial formation and then resuspended in ECM14,15,16. This resuspension step results in a loss of control over the distance between spheroids. Since distance between tumor spheroids impacts their invasive behavior, this loss of control introduces high inter-assay variance and reduces the reproducibility. Furthermore, the application of cell fractionation assays by consecutive centrifugation steps for assessment of the peripheral and tumor spheroid infiltrating immune cells is limited to tumor cell populations that generate more stable spheroids17.
Concept and approach
Our approach addresses the above-mentioned deficiencies using an &#8220;All-in-One&#8221;&#8212;3D spheroid co-culture model, which does not require the transfer of spheroids for subsequent assays. We adapted a spheroid formation device (see Table of Materials) to generate an assay for simultaneously monitoring invasive behavior of cancer cells and cytotoxicity of co-cultured T-cells. This method is user-friendly, inexpensive and allows for quick and easy handling in a relatively high-throughput 3D setting. Dependent on the type of device used, up to 81 large uniformly-sized spheroids can be generated in a single pipetting step with control over the individual spheroid size by modifying the number of cells seeded. Spheroid formation is forced by enhanced cell-cell interactions in scaffold-free agarose multi-well casts with U-shaped bottoms. We adapted this 3D system for dynamic cell-based functional studies as well as endpoint molecular and biochemical assays that include fluorescence activated cell sorting (FACS), immunofluorescence (IF) or immunohistochemistry (IHC) staining as well as gene expression analysis of the intact 3D co-culture.
For functional studies, embedding spheroids in type I collagen within the agarose casts results in invasion of cancer cells from equidistant spheroids and permits monitoring essential cell line-specific features, such as single cell vs. collective cell migration18,19. Furthermore, the collagen matrix is easily separated from the agarose cast, resulting in a 1&#8210;2 mm thick patch containing multiple spheroids, which can be further processed for IF-staining and imaging by confocal microscopy. This can reveal distinct cell invasion and cell-matrix interactions in a high-throughput screening. Also, cells in the collagen matrix can be isolated after collagen digestion and single cell dissociation for subsequent cell cultivation or analysis.
For IHC analysis of spheroids, after fixation and sectioning of the agarose cast, proteins or other molecules of interest are detectable whilst maintaining the geographic positions of the spheroids. In the approach described here, spheroids are directly embedded in Hydroxyethyl agarose processing gel within the agarose cast and the gel serves as a &#8220;lid&#8221; to retain the spheroids at the bottom of the microwells. After paraffin embedding of the agarose cast20, serial horizontal sectioning is performed with the bottom of the cast serving as the starting point.
This approach contrasts with conventional IHC sectioning of spheroids that requires harvesting of cells before embedding in Hydroxyethyl agarose processing gel21 and risks disruption of spheroids thus losing the spatial arrangement of cells. Also, cell fractionation by centrifugation for assessing whether immune cells infiltrated or remained peripheral to tumor spheroids17 is avoided by direct embedding.
Furthermore, 3D co-culture can be performed by admixing tumor, stromal or immune cells, and thus studying tumor cell crosstalk or recapitulating different tumor microenvironments for analyzing cell-cell interactions including co-cultures with endothelial cells16.
This 3D spheroid co-culture setting can be used to perform co-culture of different cell types present in the tumor microenvironment and to assess the effects of altered ECM elements. Besides type I collagen, other ECM components (e.g., matrigel, matrigel/collagen mixtures, fibronectin), can be used since tumor cell invasion is impacted by the abundance of different substrates22. Also, the microwells of the agarose cast are suitable for spheroid formation of primary cell lines and for cells with low cell-cell adhesion.

<table>
	<tbody>
		<tr>
			<td>3D Petri Dishes</td>
			<td>Microtissues Inc</td>
			<td>Z764019 &#38; Z764051</td>
			<td>referred to as &#34;rubber molds&#34; in the protocols; 81-microwell &#38; 35-microwell molds</td>
		</tr>
		<tr>
			<td>8-well Chamber Slides</td>
			<td>Lab-Tek</td>
			<td>154534</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose Type I, low EEO</td>
			<td>Sigma-Aldrich</td>
			<td>A6013</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-rabbit-HRP conjugated secondary antibody</td>
			<td>Agilent</td>
			<td>K4003</td>
			<td>ready to use</td>
		</tr>
		<tr>
			<td>Collagen Type I, Rat Tail, 100 mg</td>
			<td>Millipore</td>
			<td>08-115</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase Type 4, 1 g</td>
			<td>Worthington</td>
			<td>LS004188</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, fetal bovine serum</td>
			<td>ThermoFisher</td>
			<td>11965092, 16000044</td>
			<td>referred to as &#34;cell culture medium&#34; in the protocols</td>
		</tr>
		<tr>
			<td>Harris hematoxylin</td>
			<td>ThermoFisher</td>
			<td>SH30-500D</td>
			<td></td>
		</tr>
		<tr>
			<td>HistoGel</td>
			<td>ThermoFisher</td>
			<td>HG-4000-012</td>
			<td>referred to as &#34;Hydroxyethyl agarose processing gel&#34; in the protocols</td>
		</tr>
		<tr>
			<td>Hoechst</td>
			<td>Life Technologies</td>
			<td>H1399</td>
			<td>1/1000 dilution</td>
		</tr>
		<tr>
			<td>Phalloidin 546</td>
			<td>Invitrogen</td>
			<td>486624</td>
			<td>1/200 dilution</td>
		</tr>
		<tr>
			<td>rabbit anti-CD8 antibody</td>
			<td>Cell Signaling</td>
			<td>98941</td>
			<td>1/25 dilution</td>
		</tr>
		<tr>
			<td>rat anti-keratin 8</td>
			<td>DSHB</td>
			<td>TROMA-I AB_531826</td>
			<td>1/500 dilution</td>
		</tr>
		<tr>
			<td>RNeasy Mini Kit</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td>referred to as &#34;RNA extraction kit&#34; in the protocols</td>
		</tr>
		<tr>
			<td>RPMI</td>
			<td>ThermoFisher</td>
			<td>11875093</td>
			<td>for T-cell culture medium</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>BioRad</td>
			<td>1610407</td>
			<td>referred to as &#34;Octoxynol&#34; in the protocols</td>
		</tr>
		<tr>
			<td>Trizol</td>
			<td>ThermoFisher</td>
			<td>15596026</td>
			<td>referred to as &#34;guanidinium thiocyanate with phenol&#34; in the protocols</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Sigma-Aldrich</td>
			<td>P1379</td>
			<td>referred to as &#34;polysorbate 20&#34; in the protocols</td>
		</tr>
		<tr>
			<td>TypLE</td>
			<td>ThermoFisher</td>
			<td>12604013</td>
			<td>referred to as &#34;cell dissociation enzymes solution&#34; in the protocols</td>
		</tr>
	</tbody>
</table>

monitoring cancer cell invasion and t-cell cytotoxicity in 3d culture

Significant progress has been made in treating cancer with immunotherapy, although a large number of cancers remain resistant to treatment. A limited number of assays allow for direct monitoring and mechanistic insights into the interactions between tumor and immune cells, amongst which, T-cells play a significant role in executing the cytotoxic response of the adaptive immune system to cancer cells. Most assays are based on two-dimensional (2D) co-culture of cells due to the relative ease of use but with limited representation of the invasive growth phenotype, one of the hallmarks of cancer cells. Current three-dimensional (3D) co-culture systems either require special equipment or separate monitoring for invasion of co-cultured cancer cells and interacting T-cells.
Here we describe an approach to simultaneously monitor the invasive behavior in 3D of cancer cell spheroids and T-cell cytotoxicity in co-culture. Spheroid formation is driven by enhanced cell-cell interactions in scaffold-free agarose microwell casts with U-shaped bottoms. Both T-cell co-culture and cancer cell invasion into type I collagen matrix are performed within the microwells of the agarose casts without the need to transfer the cells, thus maintaining an intact 3D co-culture system throughout the assay. The collagen matrix can be separated from the agarose cast, allowing for immunofluorescence (IF) staining and for confocal imaging of cells. Also, cells can be isolated for further growth or subjected to analyses such as for gene expression or fluorescence activated cell sorting (FACS). Finally, the 3D co-culture can be analyzed by immunohistochemistry (IHC) after embedding and sectioning. Possible modifications of the assay include altered compositions of the extracellular matrix (ECM) as well as the inclusion of different stromal or immune cells with the cancer cells.

The 3D co-culture model allows for different assays shown in Figure 1A, which can be combined or modified as needed. In our established experimental setup, tumor and T-cells are co-cultured for 2 days followed by initiation of the invasion assay for selection of invasive and/or resistant tumor cells (Figure 1B). On day 4 the quantitation of invasion is performed and &#8220;survivor&#8221; cells are isolated from the collagen matrix or directly processed for RNA<...

Watch this Scientific Journal Video about Monitoring Cancer Cell Invasion and T-Cell Cytotoxicity in 3D Culture at JoVE.com

Monitoring Cancer Cell Invasion and T-Cell Cytotoxicity in 3D Culture

The presented approach simultaneously evaluates cancer cell invasion in 3D spheroid assays and T-cell cytotoxicity. Spheroids are generated in a scaffold-free agarose multi-microwell cast. Co-culture and embedding in type I collagen matrix are performed within the same device which allows to monitor cancer cell invasion and T-cell mediated cytotoxicity.

Significant progress has been made in treating cancer with immunotherapy, although a large number of cancers remain resistant to treatment. A limited ...

These methods can provide mechanistic insights into immune cell-mediated tumor cell cytotoxicity and invasive behavior in a 3D setting. The main advantage of this technique is that this 3D spheroid co-culture model does not require the transfer of spheroids for multiple subsequent essays. Demonstrating this procedure will be Apsra Nasir, a PhD student from our department.To generate the spheroids using aseptic technique in a cell culture hood add 500 microliters of molten agarose into an 81 microwell rubber mold taking care to avoid bubbles. When the agarose has solidified carefully flex the rubber mold to pop out the agarose casts into individual wells of a 12 well plate. To equilibrate the casts add 2.5 milliliters of cell culture medium supplemented with 10%fetal bovine serum into each well and place the plate into a cell culture incubator for one hour.At the end of the incubation tilt the plate to remove the cell culture medium in the surrounding first, then in the seeding chamber and carefully seed 190 microliters of the prepared to tumor cell suspension dropwise into each cell seeding chamber. After a 15 minute incubation in the cell culture incubator add at 2.5 milliliters of medium to the outside of the cast and return the plate to the incubator for 48 hours. To set up a T-cell co-culture resuspend the appropriate number of T-cells in 190 microliters of inappropriate T-cell culture, medium per well until the 12 well-plate to allow removal of the cell culture medium surrounding the agarose cast first.Then in the seeding chamber, without removing the spheroids use a light microscope to check whether any spheroids have been aspirated and holding the P200 loaded pipette about half a centimeter above each cast carefully seed the T-cells onto the casts in a dropwise fashion without dislodging the spheroids. When all of the casts have been seeded carefully returned the plate to the cell culture incubator for 15 minutes before adding fresh cell culture medium supplemented with fetal bovine serum to the outside of each cast for another 48 hour incubation. To embed the 3D co-cultures in type one collagen dilute stock collagen with serum free base medium to a final working concentration of three milligrams per milliliter and add 11 microliters of 10X PBS, add 1.2 microliters of one molar sodium hydroxide per 100 microliters of collagen.After neutralizing the collagen solution on ice for one hour, remove the cell culture medium surrounding and within each cast as demonstrated. Carefully add the neutralized collagen one mixture to each cast in a dropwise fashion, and immediately returned the plate to the cell culture incubator for five minutes before inverting the plate for an additional one hour in the incubation. At the end of the incubation place the plate right side up in the biosafety hood and slowly add a fresh cell culture medium down the side of each well.Then return the plate to the cell culture incubator for 48 hours. For immunofluorescent staining of the embedded 3D co-cultures fix each entire agarose cast including the spheroids in 5.4%formalin overnight at room temperature in a humidified chamber. The next day, remove the formalin surrounding the agarose cast and use sleek tip tweezers to grasp the corner of each collagen matrix to allow the casts to be peeled from the seeding chambers in a single fluid movement.Place each collagen patch into a single well of an eight well chamber slide and add 250 microliters of 0.5%octoxynol all to each well. After one hour at room temperature replace the octoxynol with 250 microliters of blocking solution. After one hour at room temperature add a 250 microliters of the primary antibody cocktail of interest to each well and place a slide in a dark humidified chamber overnight at room temperature.The next morning remove the primary antibody from each well and wash the wells three times with 300 microliters of IF buffer for five minutes at room temperature per wash. After the last wash, add a 250 microliters of inappropriate secondary antibody solution to each well for a one hour incubation at room temperature protected from light. At the end of the incubation remove the antibody and wash each sample three times with IF buffer as demonstrated.After the last wash rinse the samples with 300 microliters of PBS per well and carefully remove the walls of the chamber slide. So that only the glass slide at the bottom remains. Add 200 microliters of mounting medium to the glass slide and carefully drop the cover slip onto the sample without creating bubbles then store the mounted samples in a dark dry place overnight before imaging by confocal fluorescence microscopy Here typical experimental setups for the assays and they yield of representative and analyzable samples at the end of the experiment for each protocol can be observed.Embedding the 3D culture in type one collagen within the micro wells of an agarose cast allows monitoring and analysis of the invasion by image J.In this analysis of two primary murine, pancreatic cancer cell lines different spheroid shapes and invasive behaviors were observed. The first cell line one demonstrated a more compact spheroid formation and spiky invasion similar to that observed for single cell invasions. While the second cell line formed spheroids that were more loose and demonstrated a collective invasion pattern.Co-culture can be performed with two different tumor clonal cell lines seeded at the same time or with tumor and T-cells upon tumor spheroid formation or a subsequent tumor T-cell interaction evaluations. For a detailed assessment of the invasive behavior immunofluorescent staining and con focal imaging can be performed in a high throughput manner. The agarose cast allows embedding of the whole 3D culture system in paraffin for serial sectioning and immunohistochemistry staining to quantify the spatial relationship between tumor and T-cells.For example, T-cell infiltration can be identified and characterized by cell surface marker staining. This technique allows the analysis of patient samples as well as the use of stimulating and blocking drugs to probe tumor cell T-cell interactions.

monitoring-cancer-cell-invasion-and-t-cell-cytotoxicity-in-3d-culture

Research

JoVE Journal

Cancer Research

11.1K visualizações.  Georgetown University. Esses métodos podem fornecer insights mecanicistas sobre citotoxicidade de células tumorais mediadas por células imunes e comportamento invasivo em um ambiente 3D. A principal vantagem dessa técnica é que este modelo de cocultura 3D esferoide não requer a transferência de esferoides para múltiplos ensaios subsequentes. Demonstrando este procedimento será Apsra Nasir, uma estudante de doutorado do nosso departamento.Para gerar os esferoides usando técnica asséptica em uma cap...