The authors wish to thank Dr. Ming-Min Chang and Ms. Ya-Hsin Cheng for their technical support. This work was supported by Taiwan&#39;s Ministry of Science and Technology (MOST- 103-2325-B-006 -009, MOST- 104-2325-B-006-001, MOST- 105-2325-B-006-001, and MOST-106-2320-B-006-068-MY3) and the Ministry of Health and Welfare (MOHW106-TDU-B-211-144004). We are also grateful for the support from the Core Research Laboratory of the College of Medicine, National Cheng Kung University, for their multi-photon confocal microscope.

All experiments on mice were performed according to the guidelines of our institute (the Guide for Care and Use of Laboratory Animals, NCKU Medical College).
1. Preparation of Instruments, Culture Media, and Dishes
<ol>
	<li>Before starting the experimental protocols, obtain sterile surgical sutures, 1 mL syringes with 26G/0.5 cm needle (for tail vein injection), 3 mL syringes with 24G/3 cm needle (for lung perfusion), Dulbecco&#39;s Modified Eagle Media (DMEM), trypsin-EDTA solution (5 g/L trypsin and 0.53 mM), fetal bovine serum (FBS), 1x PBS (137 mM NaCl, 2.7 mM KCl, 10 mM Na2PHO4, and 1.8 mM KH2PO4), and 6 cm culture dishes.</li>
</ol>
2. Preparation and Recovery of Tumor Cells in Suspension
<ol>
	<li>Prepare sterile Dulbecco&#39;s Modified Eagle Media (DMEM) containing 10% or 20% FBS and freshly add 2 mM L-glutamine, 1x PBS, and 0.05% Trypsin-EDTA.</li>
	<li>Culture the cells in DMEM supplemented with 10% FBS at 37 &#176;C and grow them until there is 70-80% confluence in the culture dish.</li>
	<li>Remove the culture media (DMEM) from the dishes, followed by two washes with 2 mL of sterile 1x PBS.</li>
	<li>Add 1 mL of 0.05% Trypsin-EDTA into the dishes to thoroughly cover all the cells. Immediately remove 800 &#956;L of solution and leave only 200 &#956;L in the dishes. Incubate the dishes at 37 &#176;C for 30 s to 1 min (depending on cell type) and wait until the majority of cells are in the suspended state.</li>
	<li>Add 1 mL of fresh DMEM containing 10% FBS directly into the dishes to stop the enzymatic activity of trypsin and vigorously pipette the cell suspension up and down with a 1000 &#181;L pipette to prepare a single cell suspension.</li>
	<li>Transfer the cells from the dish to a 1.5 mL microcentrifuge tube, and spin down the cells at room temperature at 162 x g for 3 min.</li>
	<li>Aspirate the supernatant and resuspend the tumor cells in 1.5 mL DMEM containing 20% FBS and end-over-end rotate the cells in suspension at 37 &#176;C for 2 h. 
	NOTE: If the medium turns yellow during the recovery, exchange the old medium with fresh medium containing 20% FBS.</li>
</ol>
3. Fluorescence Staining and Analysis of Tumor Cells in Suspension With Carboxyfluorescein Succinimidyl Ester (CFSE)
<ol>
	<li>After cell recovery in suspension, count the appropriate viable cell numbers with Trypan Blue in a Neubauer counting chamber for titrating the fluorescence staining doses and for tail vein injection.</li>
	<li>Spin down the cells at 162 x g at room temperature for 3 min and resuspend the pelleted cells in 1 mL of sterilized 1x PBS, followed by room temperature centrifugation at 162 x g for 3 min.</li>
	<li>Resuspend the pelleted cells in 500 &#181;L of 1X PBS containing 10% FBS and 0, 5, 10, 20, or 40 &#181;M CFSE for dose titration, and incubate the cell suspension at 37 oC for 10 min in the dark.</li>
	<li>Spin down the cells at 162 x g at room temperature for 3 min and resuspend the pelleted cells with 4 mL of DMEM containing 1% FBS. Repeat this washing step three more times. Resuspend the pelleted cells with 4 mL of DMEM alone for the final wash.</li>
	<li>Subject the CFSE-labeled cells to fluorescence-activated cell sorting (FACS) analysis to quantify the fluorescence intensity of a single cell, or tail vein injection. 
	NOTE: Keep the cells on ice prior to performing the FACS analysis or tail vein injections.</li>
</ol>
4. Lung Colonization Assay
<ol>
	<li>Prepare the cells labeled with 20 &#181;M CFSE (refer to Steps 3.1 through 3.4). 
	NOTE: Decide the working dose of CFSE for labelling tumor cells, based on the titration results from the FACS analysis (refer to Step 3.3).</li>
	<li>Warm up the tails of 4-6 week-old male C57BL/6 mice (6 mice) with a halide lamp for 5-10 min on a mouse-by-mouse basis to dilate mouse tail veins.</li>
	<li>Thoroughly mix and aspirate CFSE-labeled tumor cells with a 1 mL (26Gx1/2) syringe, avoiding any bubbles in the cell suspension (with a final cell density of 5 x 106 cells/mL).</li>
	<li>Carefully inject 1 x106 CFSE-labeled tumor cells in 200 &#181;L of DMEM into the mouse tail vein, which should be lodged in a mouse restrainer. 
	NOTE: During the injection, if the needle is directly placed in the lumen of the tail vein, tumor cells should be easily delivered into the circulation without needing to push hard on the syringe. If it is hard to push the tumor cells through, they have most likely been injected outside of the tail vein, into the subcutaneous space.</li>
	<li>Divide the mice that intravenously received the CFSE-labeled tumor cells into two groups: one group will undergo lung perfusion followed by confocal microscopy and ImageJ quantification in the lung colonization assay and the other one will be left alone for 4-5 weeks in the long term lung colonization assay.</li>
	<li>At 20, 38, or 45 h and with 1x 106 tumor cells intravenously injected during a time course- and dose-dependent titration, anesthetize tumor-bearing mice with 50-75 mg/kg zoletil 50, which is a well-accepted and proper anesthetizer23. 
	NOTE: Use vet ointment on the mice&#39;s eyes to prevent dryness while under anesthesia.</li>
	<li>Longitudinally cut the skin and subcutaneous tissues from the abdomen to the chest region with surgical scissors. Open the pleural cavity with surgical scissors and forceps to fully expose the heart and lungs. 
	NOTE: Be careful to avoid cutting off blood vessels.</li>
	<li>Tie the superior vena cava (SVC) and inferior vena cava (IVC) with sterile surgical sutures to prevent the backflow of perfusion solution during lung perfusion.</li>
	<li>Cut the left ventricle wall with surgical scissors to open a fissure (about 2-4 mm) to drain the perfusion solution from the lungs.</li>
	<li>Inject 1x PBS into the right ventricle with a 3 mL syringe and remove the drained solution with constant suction during lung perfusion until the lungs turn from a reddish color to completely pale.</li>
</ol>
5. Confocal Microscopic Imaging and Analysis of Lung-Colonized Tumor Cells
<ol>
	<li>Remove the now-pale lungs from the pleural cavity and separate the five lobes by cutting away the trachea and connective tissue ligaments with surgical scissor and forceps24.</li>
	<li>Prepare a stretcher-like lung holder as shown in Figure 3B by winding a nylon suture around two metal rods to produce a reticulate texture with a space between the two rods for the placement of lung lobes. Set the lung holder in a 6 cm dish. 
	NOTE: The lung holder will be used to stabilize the lung lobes underneath the objective lens of a confocal microscope.</li>
	<li>Lodge and fix the lung lobes on the reticulate texture of the lung holder. Cover and moisten the lung lobes with 1x PBS.</li>
	<li>Subject the 6-cm culture dish harboring the lung lobes on the lung holder to confocal microscopy to capture fluorescence images recording the lung-colonizing tumor cells.</li>
	<li>For imaging, use objective lenses (5X, MPLN, NA: 0.1, WD: 20, Air).</li>
	<li>Rotate the filter wheel to NIBA (excitation/emission; 470-495 nm/510-550 nm) and use a 488 nm laser to excite CFSE, to clearly visualize images of fluorescence dots in the lung lobes.</li>
	<li>Rotate the filter wheel to R690 (for MaiTai HP DeepSee laser) to scan with 2.0 &#181;s/pixel scanning speed and optimize the HV, Gain, and offset levels.</li>
	<li>Capture fluorescence images (512 x 512 pixels) by using the microscope software with a 10 &#181;s/pixel scanning speed.</li>
	<li>Quantify and statistically analyze the microscopic images using ImageJ and GraphPad software as previously described21.</li>
</ol>
6. Long term lung colonization assays
NOTE: Repeat steps 4.1 through 4.5.
<ol>
	<li>Sacrifice the mice after tumor cell inoculation for 4-5 weeks and fix their lungs with Bouin&#39;s Fluid25 for 1 to 2 days.</li>
	<li>Quantify and statistically analyze the tumor nodules from the mice lungs with software21.</li>
</ol>

The authors have nothing to disclose.

Together with long term lung colonization assays, the short term methodology we employed here to evaluate in vivo lung colonization by CTCs in distant organs clearly unveiled and differentiated the specific role of polyFN assembled on CTCs in colonizing the lungs, which then led to the extravasation and metastatic processes18,19,20,21. Although labeling cells with long term cell tracke...

Metastasis is the major cause of cancer death1,2. Tumor cells derived from primary tissues enter the circulation in suspension and survive various hematogenous challenges, e.g., anoikis, immune assaults, and damages due to shear stress from blood pressure or geometric constraints, before they are able to colonize distant organs, a key step dictating the success of metastasis3,4,5,6. Therefore, vigorous efforts have currently been made in characterizing circulating tumor cells (CTCs) and correlating these characteristics with tumor malignancy, metastasis, and survival rates of cancer patients7,8,9. Since the process of cancer metastasis specifically depicts an in vivo event, animal models are the only approach that captures the full systemic process of metastasis10,11,12.
CTCs become metastatic tumor tissues through multiple cellular events including the colonization of distant organs1,2. However, the most commonly used metastasis assays13,14,15 do not provide a way to observe CTC colonization of distant organs. Therefore, an in vivo assay design for CTC colonization visualization is urgently needed. Although several in vivo and ex vivo short term lung colonization assays have been designed, problems and disadvantages remain. For instance, while green fluorescence protein (GFP)-overexpressing tumor cells have been used in these assays22,23, it takes time to stably transfect and clone tumor cells with sufficient GFP fluorescent intensity under the microscope. Similarly, although transient staining of tumor cells with the long term cell tracer CFSE has been employed to replace the GFP-expressing tumor cells, it remains difficult to judge whether the CFSE-labeled tumor cells are attached or merely present within the vasculature of the excised distant organs16,17.
Polymeric fibronectin (polyFN) assembled on surfaces of CTCs has been found to critically contribute to the final establishment of metastatic tumor tissues18,19,20,21,22. Here, 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 CFSE were intravenously inoculated into C57BL/6 mice. After 2-3 days, mouse lungs were first perfused with phosphate buffered saline (PBS) to completely remove unattached CTCs within the vasculature before being subjected to confocal microscopy and quantification of lung-colonizing LLCs. We clearly showed that the numbers of lung-colonizing shFN LLCs and tumor nodules were significantly reduced in comparison with shScr LLCs,substantially corroborating the role of polyFN assembly on CTCs in facilitating the colonization and growth of CTCs in the lungs. Our study warrants further investigation for the role of polyFN in cancer metastasis.

<table><tbody><tr><td>&lt;strong&gt;Material&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Bovine Serum Albumin&amp;nbsp;(BSA)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-9048-46-8</td><td></td></tr><tr><td>Bouin&#039;s Fluid</td><td>MCC(medical chemical corporation)/POISON</td><td>456-A-1GL</td><td></td></tr><tr><td>CFSE Proliferation Dye</td><td>ebiosciences</td><td>65-0850-85</td><td>Full name: Carboxyfluorescein succinimidyl ester</td></tr><tr><td>Dulbecco&#039;s Modified Eagle Media (DMEM)&amp;nbsp;</td><td>(Gibco)ThermoFisher Scientific</td><td>12100-061</td><td></td></tr><tr><td>Ethylenediaminetetraacetic acid (EDTA)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-6381-92-6</td><td>For prepared trypsin-EDTA solution( Final concentration: 0.53mM )&amp;nbsp;</td></tr><tr><td>Fetal bovine serum (FBS)</td><td>(Gibco)ThermoFisher Scientific</td><td>10437-028</td><td></td></tr><tr><td>Lewis lung carcinoma (LLC)</td><td>ATCC, Manassas, VA, USA</td><td>CRL-1642</td><td></td></tr><tr><td>L-Glutamine, USP&amp;nbsp;</td><td>(Gibco)ThermoFisher Scientific</td><td>21051-024</td><td></td></tr><tr><td>Potassium chloride (KCl)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-7447-40-7</td><td>For prepared 1X PBS ( Final concentration: 2.7mM )</td></tr><tr><td>Potassium phosphate monobasic (KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-7778-77-0</td><td>For prepared 1X PBS ( Final concentration: 1.8mM )</td></tr><tr><td>Sodium chloride (NaCl)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-7647-14-5</td><td>For prepared 1X PBS ( Final concentration: 137mM )</td></tr><tr><td>Sodium phosphate dibasic (Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Cyrusbioscience (Taipei, Taiwan)</td><td>101-10039-32-4</td><td>For prepared 1X PBS ( Final concentration: 10mM )</td></tr><tr><td>Trypan Blue</td><td>Sigma Aldrich</td><td>T6146</td><td>0.5 g mix with 100 mL 1X PBS</td></tr><tr><td>Trypsin</td><td>Sigma Aldrich</td><td>T4799</td><td>For prepared trypsin-EDTA solution ( Final concentration: 5g/L )</td></tr><tr><td>Zoletil 50</td><td>Virbac</td><td></td><td>To dilute with 1X PBS&amp;nbsp;</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Compact Tabletop Centrifuge 2420</td><td>KUBOTA Co.</td><td>2420</td><td></td></tr><tr><td>Culture dish (6cm)</td><td>Wuxi NEST Biotechnology Co.</td><td>705001</td><td></td></tr><tr><td>Disposable syringe (with needle)</td><td>Perfect Medical Industry Co.</td><td></td><td>24G/3 cm;3 ml &amp;amp; 26G/0.5 cm;1 ml</td></tr><tr><td>End over end mixer</td><td>C.T.I YOUNG CHENN</td><td>TS-20</td><td>For suspended cells recovery&amp;nbsp;</td></tr><tr><td>FACSCalibur (FACS)</td><td>BD biosciences</td><td></td><td></td></tr><tr><td>Forceps</td><td>Dimeda</td><td>10.102.14</td><td></td></tr><tr><td>Forma Direct Heat CO&lt;sub&gt;2&lt;/sub&gt; incubator</td><td>Thermo Fisher Scientific Inc.</td><td>HEPA CLASS 100</td><td></td></tr><tr><td>Mouse restrainer (Cylindrical Restrainer 15-30 gm)</td><td>Stoelting</td><td>51338</td><td></td></tr><tr><td>Multiphoton Confocal Microscope BX61WI</td><td>Olympus</td><td>FV1000MPE</td><td></td></tr><tr><td>Neubauer counting chamber</td><td>Marienfeld-Superior</td><td>640010</td><td></td></tr><tr><td>Surgical scissor</td><td>Dimeda</td><td>08.370.11</td><td></td></tr><tr><td>Surgical sutures&amp;nbsp;</td><td>UNIK SURGICAL SUTURES MFG. CO.</td><td>NO. 0034</td><td>Black Braided silk; non-absorbable (25YD; U.S.P. 4/0)</td></tr><tr><td>1.5 mL microcentrifuge tube</td><td>Wuxi NEST Biotechnology Co.</td><td>615001</td><td></td></tr><tr><td>15 mL Greiner tube</td><td>Greiner bio-one</td><td>188271</td><td></td></tr></tbody></table>

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.

Prior to performing the in vivo lung colonization assay as illustrated in Figure 1A to test whether polyFN on suspended tumor cells mediates lung colonization and/or extravasation in facilitating metastasis, we first titrated different concentrations of CFSE, a fluorescent compound that is cell permeable and covalently conjugates intracellular amine-containing molecules26,27 in suspended tumo...

Watch this Scientific Journal Video about The Establishment of a Lung Colonization Assay for Circulating Tumor Cell Visualization in Lung Tissues at JoVE.com

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

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 ...

the-establishment-lung-colonization-assay-for-circulating-tumor-cell

Research

JoVE Journal

Cancer Research

9.2K Views.  National Cheng Kung University. Een dierlijk model is nodig om het ontcijferen van de rol van circulerende tumorcellen (CTCs) bij de bevordering van longkanker kolonisatie tijdens kanker uitzaaiingen. Hier, we vastgesteld en met succes uitgevoerd een in vivo assay op specifiek proef de eis van polymere fibronectine (polyFN) vergadering over CTCs voor longkanker kolonisatie.

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

Lung Tumor Cell Recruitment Assay

To investigate the molecular mechanisms governing tumor metastasis, various assays using the mouse as a model animal have been proposed. Here, we demonstrate a simple assay to evaluate tumor cell extravasation or micrometastasis. In this assay, tumor cells were injected through the tail vein, and after a short period, the lungs were dissected and digested to count the accumulated labeled tumor cells. This assay skips the initial step of primary tumor invasion into the blood vessel and facilitates the study of events in the distant organ where tumor metastasis occurs. The number of cells injected into the blood vessel can be optimized to observe a limited number of metastases. It has been reported that stromal cells in the distant organ contribute to metastasis. Thus, this assay could be a useful tool to explore potential therapeutic drugs or devices for prevention of tumor metastasis.

This manuscript describes a method to quantify tumor cell accumulation in the lungs in an animal model of tumor metastasis.

To investigate the molecular mechanisms governing tumor metastasis, various assays using the mouse as a model animal have been proposed. Here, we ...

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 ...

Practical Considerations in Studying Metastatic Lung Colonization in Osteosarcoma Using the Pulmonary Metastasis Assay

The pulmonary metastasis assay (PuMA) is an ex vivo lung explant and closed cell culture system that permits researchers to study the biology of lung colonization in osteosarcoma (OS) by fluorescence microscopy. This article provides a detailed description of the protocol, and discusses examples of obtaining image data on metastatic growth using widefield or confocal fluorescence microscopy platforms. The flexibility of the PuMA model permits researchers to study not only the growth of OS cells in the lung microenvironment, but also to assess the effects of anti-metastatic therapeutics over time. Confocal microscopy allows for unprecedented, high-resolution imaging of OS cell interactions with the lung parenchyma. Moreover, when the PuMA model is combined with fluorescent dyes or fluorescent protein genetic reporters, researchers can study the lung microenvironment, cellular and subcellular structures, gene function, and promoter activity in metastatic OS cells. The PuMA model provides a new tool for osteosarcoma researchers to discover new metastasis biology and assess the activity of novel anti-metastatic, targeted therapies.

The goal of this article is to provide a detailed description of the protocol for the pulmonary metastasis assay (PuMA). This model permits researchers to study metastatic osteosarcoma (OS) cell growth in lung tissue using a widefield fluorescence or confocal laser-scanning microscope.

The pulmonary metastasis assay (PuMA) is an ex vivo lung explant and closed cell culture system that permits researchers to study the biology of lung ...

Acellular and Cellular Lung Model to Study Tumor Metastasis

It is difficult to isolate tumor cells at different points of tumor progression. We created an ex vivo lung model that can show the interaction of tumor cells with a natural matrix and continual flow of nutrients, as well as a model that shows the interaction of tumor cells with normal cellular components and a natural matrix. The acellular ex vivo lung model is created by isolating a rat heart-lung block and removing all the cells using the decellularization process. The right main bronchus is tied off and tumor cells are placed in the trachea by a syringe. The cells move and populate the left lung. The lung is then placed in a bioreactor where the pulmonary artery receives a continual flow of media in a closed circuit. The tumor grown on the left lung is the primary tumor. The tumor cells that are isolated in the circulating media are circulating tumor cells and the tumor cells in the right lung are metastatic lesions. The cellular ex vivo lung model is created by skipping the decellularization process. Each model can be used to answer different research questions.

Here, we present a protocol for an ex vivo lung cancer model that mimics the steps of tumor progression and helps to isolate a primary tumor, circulating tumor cells, and metastatic lesions.

It is difficult to isolate tumor cells at different points of tumor progression. We created an ex vivo lung model that can show the interaction of tumor ...

Improved Visualization of Lung Metastases at Single Cell Resolution in Mice by Combined In-situ Perfusion of Lung Tissue and X-Gal Staining of lacZ-Tagged Tumor Cells

Metastasis is the main cause of death in the majority of cancer types and consequently a main focus in cancer research. However, the detection of micrometastases by radiologic imaging and the success in their therapeutic eradication remain limited.
While animal models have proven to be invaluable tools for cancer research1, the monitoring/visualization of micrometastases remains a challenge and inaccurate evaluation of metastatic spread in preclinical studies potentially leads to disappointing results in clinical trials2. Consequently, there is great interest in refining the methods to finally allow reproducible and reliable detection of metastases down to the single cell level in normal tissue. The main focus therefore is on techniques, which allow the detection of tumor cells in vivo, like micro-computer tomography (micro-CT), positron emission tomography (PET), bioluminescence or fluorescence imaging3,4. We are currently optimizing these techniques for in vivo monitoring of primary tumor growth and metastasis in different osteosarcoma models. Some of these techniques can also be used for ex vivo analysis of metastasis beside classical methods like qPCR5, FACS6 or different types of histological staining. As a benchmark, we have established in the present study the stable transfection or transduction of tumor cells with the lacZ gene encoding the bacterial enzyme &beta;-galactosidase that metabolizes the chromogenic substrate 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) to an insoluble indigo blue dye7 and allows highly sensitive and selective histochemical blue staining of tumor cells in mouse tissue ex vivo down to the single cell level as shown here. This is a low-cost and not equipment-intensive tool, which allows precise validation of metastasis8 in studies assessing new anticancer therapies9-11. A limiting factor of X-gal staining is the low contrast to e.g. blood-related red staining of well vascularized tissues. In lung tissue this problem can be solved by in-situ lung perfusion, a technique that was recently established by Borsig et al.12 who perfused the lungs of mice under anesthesia to clear them from blood and to fix and embed them in-situ under inflation through the trachea. This method prevents also the collapse of the lung and thereby maintains the morphology of functional lung alveoli, which improves the quality of the tissue for histological analysis. In the present study, we describe a new protocol, which takes advantage of a combination of X-gal staining of lacZ-expressing tumor cells and in-situ perfusion and fixation of lung tissue. This refined protocol allows high-sensitivity detection of single metastatic cells in the lung and enabled us in a recent study to detect "dormant" lung micrometastases in a mouse model13, which was originally described to be non-metastatic14.

Improved Visualization of Lung Metastases at Single Cell Resolution in Mice by Combined In-situ Perfusion of Lung Tissue and X-Gal Staining of lacZ-Tagged Tumor Cells

The novel protocol reported in the present study allows selective detection of lung metastases at single cell resolution in mice by combined in-situ lung perfusion and fixation and X-Gal staining of lacZ-tagged tumor cells.

Metastasis is the main cause of death in the majority of cancer types and consequently a main focus in cancer research. However, the detection of ...

Medicine

Semi-automatic PD-L1 Characterization and Enumeration of Circulating Tumor Cells from Non-small Cell Lung Cancer Patients by Immunofluorescence

Circulating tumor cells (CTCs) derived from the primary tumor are shed into the bloodstream or lymphatic system. These rare cells (1&#8722;10 cells per mL of blood) warrant a poor prognosis and are correlated with shorter overall survival in several cancers (e.g., breast, prostate and colorectal). Currently, the anti-EpCAM-coated magnetic bead-based CTC capturing system is the gold standard test approved by the U.S. Food and Drug Administration (FDA) for enumerating CTCs in the bloodstream. This test is based on the use of magnetic beads coated with anti-EpCAM markers, which specifically target epithelial cancer cells. Many studies have illustrated that EpCAM is not the optimal marker for CTC detection. Indeed, CTCs are a heterogeneous subpopulation of cancer cells and are able to undergo an epithelial-to-mesenchymal transition (EMT) associated with metastatic proliferation and invasion. These CTCs are able to reduce the expression of cell surface epithelial marker EpCAM, while increasing mesenchymal markers such as vimentin. To address this technical hurdle, other isolation methods based on physical properties of CTCs have been developed. Microfluidic technologies enable a label-free approach to CTC enrichment from whole blood samples. The spiral microfluidic technology uses the inertial and Dean drag forces with continuous flow in curved channels generated within a spiral microfluidic chip. The cells are separated based on the differences in size and plasticity between normal blood cells and tumoral cells. This protocol details the different steps to characterize the programmed death-ligand 1 (PD-L1) expression of CTCs, combining a spiral microfluidic device with customizable immunofluorescence (IF) marker set.

The characterization of circulating tumor cells (CTCs) is a popular topic in translational research. This protocol describes a semi-automatic immunofluorescence (IF) assay for PD-L1 characterization and enumeration of CTCs in non-small cell lung cancer (NSCLC) patient samples.

Circulating tumor cells (CTCs) derived from the primary tumor are shed into the bloodstream or lymphatic system. These rare cells (1&#8722;10 cells per mL ...

Multidimensional Coculture System to Model Lung Squamous Carcinoma Progression

Tumor-stroma interactions play a critical role in the development of lung squamous carcinoma (LUSC). However, understanding how these dynamic interactions contribute to tissue architectural changes observed during tumorigenesis remains challenging due to the lack of appropriate models. In this protocol, we describe the generation of a 3D coculture model using a LUSC primary cell culture known as TUM622. TUM622 cells were established from a LUSC patient-derived xenograft (PDX) and have the unique property to form acinar-like structures when seeded in a basement membrane matrix. We demonstrate that TUM622 acini in 3D coculture recapitulate key features of tissue architecture during LUSC progression as well as the dynamic interactions between LUSC cells and components of the tumor microenvironment (TME), including the extracellular matrix (ECM) and cancer-associated fibroblasts (CAFs). We further adapt our principal 3D culturing protocol to demonstrate how this system could be utilized for various downstream analyses. Overall, this organoid model creates a biologically rich and adaptable platform that enables one to gain insight into the cell-intrinsic and extrinsic mechanisms that promote the disruption of epithelial architectures during carcinoma progression and will aid the search for new therapeutic targets and diagnostic markers.

An in vitro model system was developed to capture tissue architectural changes during lung squamous carcinoma (LUSC) progression in a 3-dimensional (3D) co-culture with cancer-associated fibroblasts (CAFs). This organoid system provides a unique platform to investigate the roles of diverse tumor cell-intrinsic and extrinsic changes that modulate the tumor phenotype.

Tumor-stroma interactions play a critical role in the development of lung squamous carcinoma (LUSC). However, understanding how these dynamic interactions ...

Combined Use of Tail Vein Metastasis Assays and Real-Time In Vivo Imaging to Quantify Breast Cancer Metastatic Colonization and Burden in the Lungs

Metastasis is the main cause of cancer-related deaths and there are limited therapeutic options for patients with metastatic disease. The identification and testing of novel therapeutic targets that will facilitate the development of better treatments for metastatic disease requires preclinical in vivo models. Demonstrated here is a syngeneic mouse model for assaying breast cancer metastatic colonization and subsequent growth. Metastatic cancer cells are stably transduced with viral vectors encoding firefly luciferase and ZsGreen proteins. Candidate genes are then stably manipulated in luciferase/ZsGreen-expressing cancer cells and then the cells are injected into mice via the lateral tail vein to assay metastatic colonization and growth. An in vivo imaging device is then used to measure the bioluminescence or fluorescence of the tumor cells in the living animals to quantify changes in metastatic burden over time. The expression of the fluorescent protein allows the number and size of metastases in the lungs to be quantified at the end of the experiment without the need for sectioning or histological staining. This approach offers a relatively quick and easy way to test the role of candidate genes in metastatic colonization and growth, and provides a great deal more information than traditional tail vein metastasis assays. Using this approach, we show that simultaneous knockdown of Yes associated protein (YAP) and transcriptional co-activator with a PDZ-binding motif (TAZ) in breast cancer cells leads to reduced metastatic burden in the lungs and that this reduced burden is the result of significantly impaired metastatic colonization and reduced growth of metastases.

The described approach combines experimental tail vein metastasis assays with in vivo live animal imaging to allow real-time monitoring of breast cancer metastasis formation and growth in addition to the quantification of metastasis number and size in the lungs.

Metastasis is the main cause of cancer-related deaths and there are limited therapeutic options for patients with metastatic disease. The identification ...

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.

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 ...

CTC Immunofluorescence Assay : A Technique to  Characterize Circulating Tumor Cells

Source: Garcia, J., et al. <a href="https://www.jove.com/v/59873/semi-automatic-pd-l1-characterization-enumeration-circulating-tumor">Semi-automatic PD-L1 Characterization and Enumeration of Circulating Tumor Cells from Non-small Cell Lung Cancer Patients by Immunofluorescence.</a>&#160;J. Vis. Exp.&#160;(2019)
This video describes the Circulating Tumor Cells (CTC) Immunofluorescence assay, a technique to characterize the biomarkers on circulating tumor cells in non-small cell lung cancer patient samples. This assay could be used to monitor dynamic changes of the tumor and immune response, which may reflect the response to chemotherapy, radiation, and possible immunotherapy treatments.

Source: Garcia, J., et al. Semi-automatic PD-L1 Characterization and Enumeration of Circulating Tumor Cells from Non-small Cell Lung Cancer Patients by ...

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

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