This research project in the Pannequin lab was supported by research grant from the SIRIC: Grant &#171; INCa-DGOS-Inserm 6045 &#187;. The PhD theses of Guillaume Belthier and Zeinab Homayed were supported by the anti-cancer league/Ligue contre le Cancer. C&#233;line Bouclier salary was financed by &#34;region Occitanie&#34;. Thanks to Julian Venables for English editing.

All in vivo protocols were approved by the animal ethical agencies.
1. CTC Amplification in 3D Culture Conditions
<ol>
	<li>To culture CTCs in suspension, first seed CTCs in wells of an Ultra-Low Attachment (ULA) 24-well plate at the maximal concentration of 5 cells/&#181;L and into 1 mL of M12 medium (i.e., advanced DMEM-F12 supplemented with 2&#8197;mM l-glutamine, 100&#8197;Unit/mL penicillin and streptomycin, N2 supplement, 20&#8197;ng/mL epidermal growth factor and 10&#8197;ng/mL fibroblast growth factor10).</li>
	<li>To allow sphere formation and cell expansion, incubate the cells in hypoxic conditions (2% O2) between 6 to 10 days.</li>
	<li>Once the spheres are large enough (100 &#181;m), to prevent necrosis, dissociate them for amplification.
	<ol>
		<li>Place the cell suspension in a 2 mL tube or a 15 mL tube and centrifuge at 300 x g for 5 minutes.</li>
		<li>Remove the supernatant and add 500 &#181;L of gentle dissociation reagent (e.g., Accumax) to the pellet.</li>
		<li>Vortex gently and incubate the cell suspension with gentle dissociation reagent for 20 to 30 minutes at 37 &#176;C. 
		NOTE: Exceeding the incubation time in the gentle dissociation reagent (Accumax) may cause abnormal increased cell mortality.</li>
		<li>Add 1.5 mL of Phosphate Buffered Saline (PBS) and centrifuge the tube for 5 minutes at 300 x g.</li>
		<li>Pour off the supernatant and resuspend the pellet in fresh M12 medium to reach the density of 1-5 cells per &#181;L.</li>
		<li>Seed the cell suspension in new wells of an Ultra-Low Attachment plate: 10 mL for T75 flasks, 2 mL for 6 well plates and 100 &#181;L for 96 well plates</li>
	</ol>
	</li>
</ol>
2. Immuno-Fluorescence (IF) Staining on CTC Sphere Sections
<ol>
	<li>Centrifuge CTC spheres into a 15 mL tube at 300 x g for 5 min, aspirate the supernatant, and wash the pellet twice with PBS.</li>
	<li>Resuspend the pellet with 500 &#181;L of 4% paraformaldehyde (PFA) and incubate for 20 min on ice. Centrifuge the suspension at 300 x g and wash twice with 5 mL of PBS.</li>
	<li>Resuspend the pellet with (i.e., 15 to 20 &#181;L) hot and liquid Histogel. With a pipette, take all the suspension and make a droplet on a precooled surface at 4 &#176;C and let it polymerize for 5 to 10 minutes. 
	NOTE: Work fast to avoid the polymerization of the suspension into the tip.</li>
	<li>Detach the solid droplet with the blade of a scalpel and insert it into a compartmented embedding cassette.</li>
	<li>Perform the following steps: paraffin inclusion, paraffin sectioning, section rehydration, antigen retrieval and antibody incubation. These steps are the same as for any tumor or organ embedded in paraffin and processed for immunofluorescence staining12. 
	NOTE: The cassette can be stored in 70% ethanol at 4 &#176;C until paraffin embedding.</li>
</ol>
3. Cytometry Analysis
<ol>
	<li>Centrifuge CTC spheres into a 15 mL tube at 300 x g for 5 min and wash the pellet twice with PBS.</li>
	<li>Aspirate the supernatant and add 500 &#181;L of the gentle dissociation reagent to the pellet.</li>
	<li>Vortex gently and incubate the cell suspension with the gentle dissociation reagent for 20 to 30 min at 37 &#176;C. 
	NOTE: Exceeding 40 min of incubation in the gentle dissociation reagent (Accumax) may result in an abnormal increased cell mortality.</li>
	<li>Centrifuge the cell suspension for 5 min at 300 x g, eliminate the supernatant and resuspend the pellet in 5 mL of blocking buffer (i.e., PBS with 1% bovine serum albumin (BSA)).</li>
	<li>Pass the cell suspension through a 40 &#181;m cell strainer to eliminate the remaining spheres.</li>
	<li>After counting, put 200,000 cells into three fluorescence-activated cell sorting (FACS) tubes, centrifuge at 300 x g for 5 min and remove the supernatant. Use one of the three FACS tube as a control that will not receive any staining reagents.</li>
	<li>According to the datasheet, add the appropriate antibody into the two remaining FACS tubes (i.e., one conjugated antibody against the protein of interest, one conjugated isotype control).</li>
	<li>After the recommended incubation time, add 300 &#181;L of the blocking buffer to wash the cells, centrifuge the 3 tubes at 300 x g and aspirate the supernatant. Repeat this step twice. Then, resuspend the pellet with the blocking buffer with a cell viability staining reagent (except for the FACS tube control without any staining).</li>
	<li>Keep the tubes on ice until FACS analysis. Use first the tube without staining to identify the gate for the cell viability and the antibody staining. Then analyze the FACS tube with the conjugated antibody against the protein of interest, to quantify the percentage of CTC expressing the protein of interest. The FACS tube with the conjugated isotype control should not indicate a shift. This confirms that the shift is specific to the targeted protein of interest. 
	&#8203;NOTE: If possible, use a cell line expressing a high level of protein of interest as a positive control and a cell line that does not express the protein as a negative control.</li>
</ol>
4. Luminescence Viability Assay (CellTiter-Glo)
<ol>
	<li>Resuspend dissociated CTCs (as described in section 1.4.5) in M12 medium. Count the cells and adapt the cell concentration to 200,000 cells/mL.</li>
	<li>In a ULA 96-well plate, seed 10,000 dissociated CTCs per well, in 50 &#181;L, and incubate the plate in hypoxia (2% O2) for 24 h.</li>
	<li>The following day, add 50 &#181;L of the tested drug to the CTCs. It is previously recommended to perform a titration of the drug concentration, to determine the half maximal inhibitory concentration (IC50). Treat some wells with vehicle only to determine basal cell viability. 
	NOTE: The number of cells seeded may differ between CTC lines, depending on their doubling time. In addition, cells should be seeded in triplicates to minimize results variability.</li>
	<li>Incubate plates in hypoxia for another 48 h.</li>
	<li>At day 3, place the cultured plates and the luminescence cell viability buffer and substrate at room temperature and reconstitute the substrate with an appropriate volume of buffer, according to manufacturer protocol.</li>
	<li>Add 70 &#181;L of the luminescence viability mix into each cultured plate well. Put plates on an orbital shaker for 20 min to induce cell lysis and then transfer 100 &#181;L of the mix into an opaque-walled multi-well plate, compatible with the luminometer.</li>
	<li>Allow the plate to rest at room temperature, cover it with aluminum foil in order to stabilize the luminescent signal. 
	&#8203;NOTE: Luminescent signal is stable for up to 3 hours.</li>
	<li>Record luminescence using a microplate reader (i.e., Tecan Infinite 200 Pro).</li>
	<li>For data analysis, calculate the mean of the triplicate relative light unit RLU per condition. To assess the percentage of viability according to each drug concentration needed: (RLU of treated cells/RLU of untreated cells) x 100.</li>
</ol>
5. Subcutaneous Injections
<ol>
	<li>In a microcentrifuge tube, resuspend cells in 100 &#181;L of sterile PBS. If the number of injected cells is low, resuspend cells in 1:1 PBS/Matrigel, reduced in growth factors, to concentrate cells together and promote tumor initiation. 
	NOTE: Cell density can be from 10 cells (to challenge the tumor initiation capacity) to 1 million of cells depending on the scientific question and the aim of the experiment.</li>
	<li>Pull up the full volume in an insulin syringe.</li>
	<li>On an immune-deficient mouse, pinch the skin of the flank between the index and the ring finger and gently insert the needle at the base of the skin. 
	NOTE: This procedure is not painful and is done on conscious mice.</li>
	<li>Slowly inject the volume in the same spot to prevent the spreading of the cells. This will create a small bleb beneath the skin.</li>
	<li>Apply gentle pressure on the injection site to prevent the backflow of the volume.</li>
	<li>Monitor the tumor growth, every other day, using a caliper.</li>
	<li>Sacrifice the animal if the tumor exceeds 1500 mm3. Depending on the material availability, euthanize the mice by carbon dioxide or anaesthetic gases inhalation or by cervical dislocation.</li>
</ol>
6. Intrasplenic Injection
<ol>
	<li>Before starting, autoclave the surgical instruments (scissors and forceps) at 124 &#176;C for 15 min and clean out all surfaces of the working space with 70% ethanol.</li>
	<li>In a microcentrifuge tube, resuspend cells in 50 &#181;L of sterile PBS and store them on ice. Cell density can go from 0.5 to 1 million cells. A larger number of cells can cause a clots development into the blood circulation.</li>
	<li>Prior to injecting the cells, inject 100 &#181;L of 0.015 mg/mL buprenorphine subcutaneously, for pain relief.</li>
	<li>Place the mouse in an induction chamber, where isoflurane is maintained at 3%, for 2-3 min. When the animal is no longer responsive to movement, put it on its right-hand side on a heating pad and maintain the anaesthesia using a breathing circuit face mask that delivers a gas mixture of O2 and isoflurane.</li>
	<li>Apply eye lubricant over each eye to avoid eye drying during the surgery. Disinfect the thoracic area with&#160;Povidone-iodine solution (i.e. Betadine).</li>
	<li>On the dorsoventral side, make a small incision of 0.5 cm using scissors below the 10th false rib.</li>
	<li>Gently lift the spleen out and lay it on sterile gauze. Using an insulin syringe, inject the 50 &#181;L of CTCs in the tip of the spleen. Make sure to maintain the syringe upright and wait 3-5 min to avoid backflow, and then remove the needle.</li>
	<li>Ligate the splenic vessels from the two sides (arteries and veins) and remove the spleen by cutting directly above the two ligatures. The spleen is removed to prevent unwanted tumor formation in this organ.</li>
	<li>Stitch the abdominal peritoneum and then the skin using 5.0 degradable sterile sutures.</li>
	<li>Keep the mouse warm until its full recovery from anesthesia.</li>
	<li>Monitor the mouse 3 days per week for abnormal bodily function, abnormal movement and posture and for weight loss.</li>
	<li>Sacrifice the animal when humane end points reach (approximately 6 weeks after the surgery) to analyze liver metastasis.</li>
</ol>

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	<li>Wittekind, C., Neid, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+invasion+and+metastasis.">Cancer invasion and metastasis.</a> Oncology. 69, 14-16 (2005).</li><li>Eger, A., Mikulits, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+epithelial-mesenchymal+transition.">Models of epithelial-mesenchymal transition.</a> Drug Discovery Today: Disease Models. 2, 57-63 (2005).</li><li>Palmirotta, 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=Liquid+biopsy+of+cancer:+a+multimodal+diagnostic+tool+in+clinical+oncology.">Liquid biopsy of cancer: a multimodal diagnostic tool in clinical oncology.</a> Therapeutic Advances in Medical Oncology. 10, (2018).</li><li>Hong, B., Zu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detecting+circulating+tumor+cells:+current+challenges+and+new+trends.">Detecting circulating tumor cells: current challenges and new trends.</a> Theranostics. 3, 377-394 (2013).</li><li>vander Toom, E. E., Verdone, J. E., Gorin, M. A., Pienta, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technical+challenges+in+the+isolation+and+analysis+of+circulating+tumor+cells.">Technical challenges in the isolation and analysis of circulating tumor cells.</a> Oncotarget. 7, 62754-62766 (2016).</li><li>Jin, 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=Evaluation+of+the+diagnostic+value+of+circulating+tumor+cells+with+CytoSorter&#174;+CTC+capture+system+in+patients+with+breast+cancer.">Evaluation of the diagnostic value of circulating tumor cells with CytoSorter&#174; CTC capture system in patients with breast cancer.</a> Cancer Medicine. 9, 1638-1647 (2020).</li><li>Huang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relationship+between+circulating+tumor+cells+and+tumor+response+in+colorectal+cancer+patients+treated+with+chemotherapy:+a+meta-analysis.">Relationship between circulating tumor cells and tumor response in colorectal cancer patients treated with chemotherapy: a meta-analysis.</a> BMC Cancer. 14, 976 (2014).</li><li>Yu, 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=Ex+vivo+culture+of+circulating+breast+tumor+cells+for+individualized+testing+of+drug+susceptibility.">Ex vivo culture of circulating breast tumor cells for individualized testing of drug susceptibility.</a> Science. 345, 216-220 (2014).</li><li>Aceto, N., 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=Circulating+Tumor+Cell+Clusters+are+Oligoclonal+Precursors+of+Breast+Cancer+Metastasis.">Circulating Tumor Cell Clusters are Oligoclonal Precursors of Breast Cancer Metastasis.</a> Cell. 158, 1110-1122 (2014).</li><li>Grillet, 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=Circulating+tumour+cells+from+patients+with+colorectal+cancer+have+cancer+stem+cell+hallmarks+in+ex+vivo+culture.">Circulating tumour cells from patients with colorectal cancer have cancer stem cell hallmarks in ex vivo culture.</a> Gut. 66, 1802-1810 (2017).</li><li>Lee, W. Y., Hong, H. K., Ham, S. K., Kim, C. I., Cho, Y. 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The authors have no competing interests to disclose.

The protocol described above was used initially for colorectal CTC functional characterization, but it can be used for other types of cancer such as breast cancer and can be adapted for mouse models.
The real limiting factor is the number of CTCs present in the blood sample and the efficiency of the technique used to isolate and expand them. Several CTC isolation technics have been described based on specific CTC properties such as the Parsortix, a microfluidic device, that allows the isolatio...

Despite recent improvements in early cancer diagnosis and in therapeutic strategy, more than ninety percent of cancer morbidity is still due to metastasis1. The metastatic process is a multi-step cascade that starts with the local detachment of cells from the primary tumor and their entrance into the bloodstream where they become circulating tumor cells (CTCs) to finally colonize distant sites such as liver and lungs, in the case of colorectal cancer (CRC)2. Recently, there has been growing attention to liquid biopsies, which are a non-invasive tool to notably detect and enumerate CTCs from patient blood samples. Intratumor genetic heterogeneity is a major cause of drug resistance; thus, isolating representative cells from tumor material constitutes a promising tool for personalized medicine3.
Despite low frequency of CTCs in the blood (1 CTC per 106 - 107 leukocytes)4, several detection and isolation techniques were developed based on property differences between CTCs and other components of the blood5. The number of CTCs in patient blood samples, alone, can provide information about the stage of malignancy, treatment response and disease progression6,7. Thus, CTC isolation is a crucial tool for translational studies to assess genetic heterogeneity or perform drug screening, as well as for fundamental studies to characterize these invasive cells, as they are the key actors of metastatic induction8,9. Indeed, compared to commercially established cancer cell lines that have accumulated thousands of mutations over time, fresh CTCs share the main features of the original primary tumor including a potent capacity to metastasize, and they are a better reflection of the disease. These features make them a robust tool for fundamental studies, especially in knockout experiments of predicted key factors involved in metastasis. The outcome of these experiments can be validated in vivo, on mice, as described below.
Once CTCs are isolated, they can be expanded in non-adherent culture conditions and then, they can be manipulated just as any available cancer cell line, i.e. they can equally be cultured in adherent conditions or embedded in Matrigel, depending on the scientific question10. For example, to test the expression and localization of a protein of interest, CTC spheres can be grown in suspension condition and be embedded in Histogel to perform immunofluorescence on sphere sections. In addition, if the protein is membranous, its expression on living cells can be measured by cytometry.
For functional studies, to test the role of a protein of interest that may play a role in liver colonization, CTCs with genes edited, by shRNA or CRISPR/Cas9, can be injected into the spleen of immunodeficient mice. This latter experiment is a powerful model to mimic liver metastasis colonization11.
The ability of CTCs to initiate tumors can be assessed by injecting a very small number of cells into immuno-deficient mice. As tumor initiation is a hallmark of cancer stem cells (CSCs) this assay will indicate the percentage of CSCs within CTC lines. This stem cell phenotype makes circulating tumor cell lines resistant to some gold-standard cancer therapies. Expanded CTCs can therefore be used to screen drugs and pinpoint the best potential efficient treatment for the patient; CTC response to treatment can be tested in vitro using a luminescence viability assay, for example.
In a long-term perspective, drug screening on freshly isolated and amplified CTCs could be used as a new tool for personalized medicine to aid in choosing the most efficient and adapted treatment for patients.
In the present paper, protocols to culture CTC lines, to stain specific proteins via immunostaining and cytometry, to perform cytotoxicity assays as well as in vivo xenograft experiments with CTC are detailed.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Accumax solution</td>
			<td>Sigma-Aldrich</td>
			<td>A7089</td>
			<td></td>
		</tr>
		<tr>
			<td>Advanced DMEM/F-12</td>
			<td>Gibco</td>
			<td>12634028</td>
			<td></td>
		</tr>
		<tr>
			<td>CellTiter-Glo Luminescent Cell Viability Assay</td>
			<td>Promega</td>
			<td>G7570</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning Matrigel Growth Factor Reduced (GFR) Basement Membrane Matrix</td>
			<td>Corning</td>
			<td>354230</td>
			<td></td>
		</tr>
		<tr>
			<td>Costar 24-well Clear Flat Bottom Ultra-Low Attachment Multiple Well Plates,</td>
			<td>Corning</td>
			<td>3473</td>
			<td></td>
		</tr>
		<tr>
			<td>Histiogel Specimen Medium</td>
			<td>LabStorage</td>
			<td>HG-4000</td>
			<td></td>
		</tr>
		<tr>
			<td>Human EGF, premium grade</td>
			<td>Miltenyi Biotec</td>
			<td>130-097-751</td>
			<td></td>
		</tr>
		<tr>
			<td>Human FGF-2, premium grade</td>
			<td>Miltenyi Biotec</td>
			<td>130-093-564</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine (200 mM)</td>
			<td>Gibco</td>
			<td>25030081</td>
			<td></td>
		</tr>
		<tr>
			<td>N-2 Supplement</td>
			<td>Gibco</td>
			<td>17502048</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (5,000 U/mL)</td>
			<td>Gibco</td>
			<td>15070063</td>
			<td></td>
		</tr>
	</tbody>
</table>

circulating tumor cell lines: an innovative tool for fundamental and translational research

Metastasis is a leading cause of cancer death. Despite improvements in treatment strategies, metastatic cancer has a poor prognosis. We thus face an urgent need to understand the mechanisms behind metastasis development, and thus to propose efficient treatments for advanced cancer. Metastatic cancers are hard to treat, as biopsies are invasive and inaccessible. Recently, there has been considerable interest in liquid biopsies including both cell-free circulating deoxyribonucleic acid (DNA) and circulating tumor cells from peripheral blood and we have established several circulating tumor cell lines from metastatic colorectal cancer patients to participate in their characterization. Indeed, to functionally characterize these rare and poorly described cells, the crucial step is to expand them. Once established, circulating tumor cell (CTC) lines can then be cultured in suspension or adherent conditions. At the molecular level, CTC lines can be further used to assess the expression of specific markers of interest (such as differentiation, epithelial or cancer stem cells) by immunofluorescence or cytometry analysis. In addition, CTC lines can be used to assess drug sensitivity to gold-standard chemotherapies as well as to targeted therapies. The ability of CTC lines to initiate tumors can also be tested by subcutaneous injection of CTCs in immunodeficient mice.
Finally, it is possible to test the role of specific genes of interest that might be involved in cancer dissemination by editing CTC genes, by short hairpin ribonucleic acid (shRNA) or Crispr/Cas9. Modified CTCs can thus be injected into immunodeficient mouse spleens, to experimentally mimic part of the metastatic development process in vivo.
In conclusion, CTC lines are a precious tool for future research and for personalized medicine, where they will allow prediction of treatment efficiency using the very cells that are originally responsible for metastasis.

Both EpCAM and CD26 expressions observed by IF (Figure 1A right panel) and FACS (Figure 1B) respectively, indicate that the CTC line is epithelial and display one of the CSC hallmarks10. This epithelial trait can be further characterized by staining with antibodies directed against other epithelial and mesenchymal markers. Thereby, it could be possible to approximately know where the CTC line is along the epithelial-mesen...

Watch this Scientific Journal Video about Circulating Tumor Cell Lines: an Innovative Tool for Fundamental and Translational Research at JoVE.com

Circulating Tumor Cell Lines: an Innovative Tool for Fundamental and Translational Research

Culturing CTCs allows a deeper functional characterization of cancer, through assaying specific marker expression, and assessing drug resistance and the ability to colonize the liver among other possibilities. Overall, CTC culture could be a promising clinical tool for personalized medicine to improve patient outcome.

Metastasis is a leading cause of cancer death. Despite improvements in treatment strategies, metastatic cancer has a poor prognosis. We thus face an ...

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Cancer Research

4.0K Views.  Montpellier University. Culturing CTCs allows a deeper functional characterization of cancer, through assaying specific marker expression, and assessing drug resistance and the ability to colonize the liver among other possibilities. Overall, CTC culture could be a promising clinical tool for personalized medicine to improve patient outcome. 

Video: Circulating Tumor Cell Lines: an Innovative Tool for Fundamental and Translational Research

Capture and Release of Viable Circulating Tumor Cells from Blood

We demonstrate a method for size based capture of viable circulating tumor cell (CTC) from whole blood, along with the release of these cells from chip for downstream analysis and/or culture. The strategy employs the use of a novel Parylene C membrane slot pore microfilter to capture CTC and a coating of poly (N-iso-propylacrylamide) (PIPAAm) for thermoresponsive viable release of the captured CTC. The capture of live cells is enabled by leveraging the design of a slot pore geometry with specific dimensions to reduce the shear stress typically associated with the filtration process. While the microfilter exhibits a high capture efficiency, the release of these cells is non-trivial. Typically, only a small percentage of cells are released when techniques such as reverse flow or cell scraping are used. The strong adhesion of these epithelial cancer cells to the Parylene C membrane is attributable to non-specific electrostatic interaction. To counteract this effect, we employed the use of PIPAAm coating and exploited its thermal responsive interfacial properties to release the cells from the filter. Blood is first filtered at room temperature. Below 32 &#176;C, PIPAAm is hydrophilic. Thereafter, the filter is placed in either culture media or a buffer maintained at 37 &#176;C, which results in the PIPAAm turning hydrophobic, and subsequently releasing the electrostatically bound cells.

A protocol to utilize a poly(N-iso-propylacrylamide) (PIPAAm) coated microfilter for effective capture and thermoresponsive release of viable circulating tumor cells (CTC) is presented. This method allows capture of CTC from patients&#39; blood and subsequent release of viable CTC for downstream off-chip culture, analyses and characterization.

We demonstrate a method for size based capture of viable circulating tumor cell (CTC) from whole blood, along with the release of these cells from chip ...

Isolation of Circulating Tumor Cells in an Orthotopic Mouse Model of Colorectal Cancer

Despite the advantages of easy applicability and cost-effectiveness, subcutaneous mouse models have severe limitations and do not accurately simulate tumor biology and tumor cell dissemination. Orthotopic mouse models have been introduced to overcome these limitations; however, such models are technically demanding, especially in hollow organs such as the large bowel. In order to produce uniform tumors which reliably grow and metastasize, standardized techniques of tumor cell preparation and injection are critical. 
We have developed an orthotopic mouse model of colorectal cancer (CRC) which develops highly uniform tumors and can be used for tumor biology studies as well as therapeutic trials. Tumor cells from either primary tumors, 2-dimensional (2D) cell lines or 3-dimensional (3D) organoids are injected into the cecum and, depending on the metastatic potential of the injected tumor cells, form highly metastatic tumors. In addition, CTCs can be found regularly. We here describe the technique of tumor cell preparation from both 2D cell lines and 3D organoids as well as primary tumor tissue, the surgical and injection techniques as well as the isolation of CTCs from the tumor-bearing mice, and present tips for troubleshooting.

We describe the establishment of orthotopic colorectal tumors via injection of tumor cells or organoids into the cecum of mice and the subsequent isolation of circulating tumor cells (CTCs) from this model.

Despite the advantages of easy applicability and cost-effectiveness, subcutaneous mouse models have severe limitations and do not accurately simulate ...

The Establishment of a Lung Colonization Assay for Circulating Tumor Cell Visualization in Lung Tissues

Metastasis is the major cause of cancer death. The role of circulating tumor cells (CTCs) in promoting cancer metastasis, in which lung colonization by CTCs critically contributes to early lung metastatic processes, has been vigorously investigated. As such, animal models are the only approach that captures the full systemic process of metastasis. Given that problems occur in previous experimental designs for examining the contributions of CTCs to blood vessel extravasation, we established an in vivo lung colonization assay in which a long-term-fluorescence cell-tracer, carboxyfluorescein succinimidyl ester (CFSE), was used to label suspended tumor cells and lung perfusion was performed to clear non-specifically trapped CTCs prior to lung removal, confocal imaging, and quantification. Polymeric fibronectin (polyFN) assembled on CTC surfaces has been found to mediate lung colonization in the final establishment of metastatic tumor tissues. Here, to specifically test the requirement of polyFN assembly on CTCs for lung colonization and extravasation, we performed short term lung colonization assays in which suspended Lewis lung carcinoma cells (LLCs) stably expressing FN-shRNA (shFN) or scramble-shRNA (shScr) and pre-labeled with 20 &#956;M of CFSE were intravenously inoculated into C57BL/6 mice. We successfully demonstrated that the abilities of shFN LLC cells to colonize the mouse lungs were significantly diminished in comparison to shScr LLC cells. Therefore, this short-term methodology may be widely applied to specifically demonstrate the ability of CTCs within the circulation to colonize the lungs.

An animal model is needed to decipher the role of circulating tumor cells (CTCs) in promoting lung colonization during cancer metastasis. Here, we established and successfully performed an in vivo assay to specifically test the requirement of polymeric fibronectin (polyFN) assembly on CTCs for lung colonization.

Metastasis is the major cause of cancer death. The role of circulating tumor cells (CTCs) in promoting cancer metastasis, in which lung colonization by ...

Paramyxoviruses for Tumor-targeted Immunomodulation: Design and Evaluation Ex Vivo

Successful cancer immunotherapy has the potential to achieve long-term tumor control. Despite recent clinical successes, there remains an urgent need for safe and effective therapies tailored to individual tumor immune profiles. Oncolytic viruses enable the induction of anti-tumor immune responses as well as tumor-restricted gene expression. This protocol describes the generation and ex vivo analysis of immunomodulatory oncolytic vectors. Focusing on measles vaccine viruses encoding bispecific T cell engagers as an example, the general methodology can be adapted to other virus species and transgenes. The presented workflow includes the design, cloning, rescue, and propagation of recombinant viruses. Assays to analyze replication kinetics and lytic activity of the vector as well as functionality of the isolated immunomodulator ex vivo are included, thus facilitating the generation of novel agents for further development in preclinical models and ultimately clinical translation.

This protocol describes a detailed workflow for the generation and ex vivo characterization of oncolytic viruses for expression of immunomodulators, using measles viruses encoding bispecific T cell engagers as an example. Application and adaptation to other vector platforms and transgenes will accelerate the development of novel immunovirotherapeutics for clinical translation.

Successful cancer immunotherapy has the potential to achieve long-term tumor control. Despite recent clinical successes, there remains an urgent need for ...

Patient-derived Orthotopic Xenograft Models for Human Urothelial Cell Carcinoma and Colorectal Cancer Tumor Growth and Spontaneous Metastasis

Cancer patients have poor prognoses when lymph node (LN) involvement is present in both high-grade urothelial cell carcinoma (HG-UCC) of the bladder and colorectal cancer (CRC). More than 50% of patients with muscle-invasive UCC, despite curative therapy for clinically-localized disease, will develop metastases and die within 5 years, and metastatic CRC is a leading cause of cancer-related deaths in the US. Xenograft models that consistently mimic UCC and CRC metastasis seen in patients are needed. This study aims to generate patient-derived orthotopic xenograft (PDOX) models of UCC and CRC for primary tumor growth and spontaneous metastases under the influence of LN stromal cells mimicking the progression of human metastatic diseases for drug screening. Fresh UCC and CRC tumors were obtained from consented patients undergoing resection for HG-UCC and colorectal adenocarcinoma, respectively. Co-inoculated with LN stromal cell (LNSC) analog HK cells, luciferase-tagged UCC cells were intra-vesically (IB) instilled into female non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, and CRC cells were intra-rectally (IR) injected into male NOD/SCID mice. Tumor growth and metastasis were monitored weekly using bioluminescence imaging (BLI). Upon sacrifice, primary tumors and mouse organs were harvested, weighed, and formalin-fixed for Hematoxylin and Eosin and immunohistochemistry staining. In our unique PDOX models, xenograft tumors resemble patient pre-implantation tumors. In the presence of HK cells, both models have high tumor implantation rates measured by BLI and tumor weights, 83.3% for UCC and 96.9% for CRC, and high distant organ metastasis rates (33.3% detected liver or lung metastasis for UCC and 53.1% for CRC). In addition, both models have zero mortality from the procedure. We have established unique, reproducible PDOX models for human HG-UCC and CRC, which allow for tumor formation, growth, and metastasis studies. With these models, testing of novel therapeutic drugs can be performed efficiently and in a clinically-mimetic manner.

This protocol describes the generation of patient-derived orthotopic xenograft models by intra-vesically instilling high-grade urothelial cell carcinoma cells or intra-rectally injecting colorectal cancer cells into non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice for primary tumor growth and spontaneous metastases under the influence of lymph node stromal cells, which mimics the progression of human metastatic diseases.

Cancer patients have poor prognoses when lymph node (LN) involvement is present in both high-grade urothelial cell carcinoma (HG-UCC) of the bladder and ...

Establishment and Characterization of Three Afatinib-resistant Lung Adenocarcinoma PC-9 Cell Lines Developed with Increasing Doses of Afatinib

Acquired resistance to molecular target inhibitors is a severe problem in cancer therapy. Lung cancer remains the leading cause of cancer-related death in most countries. The discovery of "oncogenic driver mutations," such as epidermal growth factor receptor (EGFR)-activating mutations, and subsequent development of molecular targeted agents of EGFR tyrosine kinase inhibitors (TKIs) (gefitinib, erlotinib, afatinib, dacomitinib, and osimertinib) have dramatically altered lung cancer treatment in recent decades. However, these drugs are still not effective in patients with non-small cell lung cancer (NSCLC) carrying EGFR-activating mutations. Following acquired resistance, the systemic progression of NSCLC remains a significant obstacle in treating patients with EGFR mutation-positive NSCLC. Here, we present a stepwise dose escalation method for establishing three independent acquired afatinib-resistant cell lines from NSCLC PC-9 cells harboring EGFR-activating mutations of 15-base pair deletions in EGFR exon 19. Methods for characterizing the three independent afatinib-resistance cell lines are briefly presented. The acquired resistance mechanisms to EGFR TKIs are heterogeneous. Therefore, multiple cell lines with acquired resistance to EGFR-TKIs must be examined. Ten to twelve months are required to obtain cell lines with acquired resistance using this stepwise dose escalation approach. The discovery of novel acquired resistance mechanisms will contribute to the development of more effective and safe therapeutic strategies.

A method for establishing afatinib-resistance cell lines from lung adenocarcinoma PC-9 cells was developed, and resistant cells were characterized. The resistant cells can be used to investigate epidermal growth factor receptor tyrosine kinase inhibitor-resistance mechanisms, applicable for patients with non-small cell lung cancer.

Acquired resistance to molecular target inhibitors is a severe problem in cancer therapy. Lung cancer remains the leading cause of cancer-related death in ...

Micromanipulation of Circulating Tumor Cells for Downstream Molecular Analysis and Metastatic Potential Assessment

Blood-borne metastasis accounts for&#160;most cancer-related deaths and involves circulating tumor cells (CTCs) that are successful in establishing new tumors at distant sites. CTCs are found in the bloodstream of patients as single cells (single CTCs) or as multicellular aggregates (CTC clusters and CTC-white blood cell clusters), with the latter displaying a higher metastatic ability. Beyond enumeration, phenotypic and molecular analysis is extraordinarily important to dissect CTC biology and to identify actionable vulnerabilities. Here, we provide a detailed description of a workflow that includes CTC immunostaining and micromanipulation, ex vivo culture to assess&#160;proliferative and survival capabilities of individual cells, and in vivo metastasis-formation assays. Additionally, we provide a protocol to achieve the dissociation of CTC clusters into individual cells and the investigation of intra-cluster heterogeneity. With these approaches, for instance, we precisely quantify survival and proliferative potential of single CTCs and individual cells within CTC clusters, leading us to the observation that cells within clusters display better survival and proliferation in ex vivo cultures compared to single CTCs. Overall, our workflow offers a platform to dissect the characteristics of CTCs at the single cell level, aiming towards the identification of metastasis-relevant pathways and a better understanding of CTC biology.

Here, we present an integrated workflow to identify phenotypic and molecular features that characterize circulating tumor cells (CTCs). We combine live immunostaining and robotic micromanipulation of single and clustered CTCs with single cell-based techniques for downstream analysis and assessment of metastasis-seeding ability.

Blood-borne metastasis accounts for&#160;most cancer-related deaths and involves circulating tumor cells (CTCs) that are successful in establishing new ...

Detection and Monitoring of Tumor Associated Circulating DNA in Patient Biofluids

Complications associated with upfront and repeat surgical tissue sampling present the need for minimally invasive platforms capable of molecular sub-classification and temporal monitoring of tumor response to therapy. Here, we describe our dPCR-based method for the detection of tumor somatic mutations in cell free DNA (cfDNA), readily available in&#160;patient biofluids. Although limited in the number of mutations that can be tested for in each assay, this method provides a high level of sensitivity and specificity. Monitoring of mutation abundance, as calculated by MAF, allows for the evaluation of tumor response to therapy, thereby providing a much-needed supplement to radiographic imaging.

Here, we present a protocol to detect tumor somatic mutations in circulating DNA present in patient biological fluids (biofluids). Our droplet digital polymerase chain reaction (dPCR)-based method enables quantification of the tumor mutation allelic frequency (MAF), facilitating a minimally invasive complement to diagnosis and temporal monitoring of tumor response.

Complications associated with upfront and repeat surgical tissue sampling present the need for minimally invasive platforms capable of molecular ...

Radiosensitivity of Cancer Stem Cells in Lung Cancer Cell Lines

The presence of cancer stem cells (CSCs) has been associated with relapse or poor outcomes after radiotherapy. Studying radioresistant CSCs may provide clues to overcoming radioresistance. Voltage-gated calcium channel &#945;2&#948;1 subunit isoform 5 has been reported as a marker for radioresistant CSCs in non-small cell lung cancer (NSCLC) cell lines. Using calcium channel &#945;2&#948;1 subunit as an example of a CSC marker, methods to study the radiosensitivity of CSCs in NSCLC cell lines are presented. CSCs are sorted with putative markers by flow cytometry, and the self-renewal capacity of sorted cells is evaluated by sphere formation assay. Colony formation assay, which determines how many cells lose the ability to generate descendants forming the colony after a certain dose of radiation, is then performed to assess the radiosensitivity of sorted cells. This manuscript provides initial steps for studying the radiosensitivity of CSCs, which establishes the basis for further understanding of the underlying mechanisms.

The presence of cancer stem cells have been associated with relapse or poor outcomes after radiotherapy. This manuscript describes the methods to study the radiosensitivity of cancer stem cells in lung cancer cell lines.

The presence of cancer stem cells (CSCs) has been associated with relapse or poor outcomes after radiotherapy. Studying radioresistant CSCs may provide ...

Analysis of Side Population in Solid Tumor Cell Lines

Cancer stem cells (CSCs) are an important cause of tumor growth, metastasis, and recurrence. Isolation and identification of CSCs are of great significance for tumor research. Currently, several techniques are used for the identification and purification of CSCs from tumor tissues and tumor cell lines. Separation and analysis of side population (SP) cells are two of the commonly used methods. The methods rely on the ability of CSCs to rapidly expel fluorescent dyes, such as Hoechst 33342. The efflux of the dye is associated with the ATP-binding cassette (ABC) transporters and can be inhibited by ABC transporter inhibitors. Methods for staining cultured tumor cells with Hoechst 33342 and analyzing the proportion of their SP cells by flow cytometry are described. This assay is convenient, fast, and cost-effective. Data generated in this assay can contribute to a better understanding of the effect of genes or other extracellular and intracellular signals on the stemness properties of tumor cells.

A convenient, fast, and cost-effective method to measure the proportion of side population cells in solid tumor cell lines is presented.