Representative data was funded through the National Cancer Institute (K22CA218549 to S.T.S). In addition to their assistance in developing the comprehensive analysis method reported herein, we thank The Ohio State University Comprehensive Cancer Center Comparative Pathology and Mouse Phenotyping Shared Resource (Director &#8211; Krista La Perle, DVM, PhD) for histology and immunohistochemistry services and the Pathology Imaging Core for algorithm development and analysis.

Animal use followed University Laboratory Animal Resources (ULAR) regulations under the OSU Institutional Animal Care and Use Committee (IACUC)&#8211;approved protocol 2007A0120-R4 (PI: Dr. Gina Sizemore).
1. Tail-vein injection of breast cancer cells
<ol>
	<li>Preparation of cells and syringe for injection
	<ol>
		<li>Plate an appropriate number of cells based on the number of mice and cell concentration to be used. 
		NOTE: The number of cells injected and time to the development of metastases will depend on the cell line used and will need to be optimized. In this demonstration, 1 x 106 MDA-MB-231 cells are injected intravenously into NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice, and macroscopic lung lesions are observed no later than 24 days post-injection. For the MVT1 murine mammary tumor cell line17, 3 x 106 cells are injected into immune-competent FVB/N mice with numerous lung metastases observed by 14 days22,23.</li>
		<li>Aspirate media and rinse cell plates with 1x PBS. Trypsinize cells in minimal volume, add appropriate volume of media, and count cells using a hematocytometer or another preferred method. Trypan blue (0.4%) or other live/dead cell dyes can be used to determine viable cell counts.</li>
		<li>Pellet cells by spinning at 180 x g for 5 min.</li>
		<li>Resuspend appropriate number of cells in sterile 1x PBS such that a volume of 100 &#181;L is injected per mouse. Keep cell suspension on ice to maintain viability.</li>
		<li>Prior to injection, thoroughly resuspend cells with a 200 &#181;L or 1 mL pipette to avoid clumping. Draw up 100 &#181;L in a 28 G insulin syringe (see Table of Materials).</li>
		<li>Eliminate any air bubbles by keeping the syringe vertical, tapping on the syringe, and slowly adjusting the plunger. Injection of air bubbles into the vein is likely to cause an air/gas embolism that can be fatal.</li>
	</ol>
	</li>
	<li>Lateral tail-vein injection 
	NOTE: For experimental breast cancer metastasis assays, injections are performed on &#62; 6 weeks old female mice.
	<ol>
		<li>Handle the mouse by the tail and slide animal into a slotted tube/restraint device of an appropriate size (see the Table of Materials for restraint device used).</li>
		<li>Insert the plug portion of the restraint device and position the mouse on its side such that its lateral tail vein is easy to view. The mouse has a ventral artery in line with the genitalia, a dorsal vein, and two lateral caudal veins.</li>
		<li>Clean the surface of the mouse&#8217;s tail with an aseptic wipe. Grasp the tail between index finger and thumb with non-dominant hand and apply slight tension.</li>
		<li>Beginning at the distal portion of the tail, insert the needle parallel to the vein with the bevel end up.</li>
		<li>If allowed, carefully recap the needle and bend to a 20-30&#176; angle. A single-handed approach or needle recapping device is highly recommended. 
		NOTE: It is not necessary to aspirate as this may cause the vein to collapse. However, a small flash of blood may be seen when first placed. The needle will advance smoothly into the vein with proper placement.</li>
		<li>Slowly dispense the complete volume into the vein. There should not be resistance when the plunger is pushed.</li>
		<li>If any resistance is felt, promptly remove the syringe needle. If needed, re-insert the needle (ideally no more than 3 attempts) moving toward the proximal end of the tail or opposing lateral vein.</li>
		<li>A small volume of blood will likely be displaced after injection. Apply gentle pressure with sterile gauze and wipe with aseptic wipe.</li>
		<li>Promptly dispose of syringe in appropriate sharps container.</li>
		<li>Return the mouse to a clean, ventilated cage and monitor for signs of distress.</li>
		<li>Monitor mice 2-3x/weekly for signs of metastasis formation (labored breathing, hunched posture, weight loss) and general distress. The time to development of metastasis will depend on cell line and mouse strain.</li>
		<li>If using an in vivo live animal imaging device, image mice immediately after tail-vein injection to confirm successful injection of cells and obtain time &#8220;zero&#8221; data (specific details on in vivo bioluminescence imaging are not included herein, but are described by Yang et al.24).</li>
	</ol>
	</li>
</ol>
2. Lung tissue fixation and analysis of metastatic lung tumor burden
<ol>
	<li>Lung tissue inflation to maintain the structural format of the lungs for histopathology
	<ol>
		<li>After approved euthanasia procedures (e.g. carbon dioxide at 30 - 70% displacement of the chamber volume/min)&#160;are followed, secure the mouse carcass to a dissecting board with pins. Either spray or apply 70% ethanol to keep the mouse&#8217;s fur out of the way during dissection.&#160; 
		NOTE: Carbon dioxide asphyxiation can cause pulmonary hemorhhage as an expected background lesion, especially at slower flow rates.</li>
		<li>Open the thorax with a midline incision, extend the incision cranially/caudally through the peritoneum, and cut away the diaphragm by grasping the xyphoid process.</li>
		<li>Using a separate set of scissors to not dull the blades, cut the ribs along each side of the sternum and carefully remove rib cage leaving room for the lungs to expand.</li>
		<li>Isolate the trachea by removing submandibular salivary glands and infrahyoid musculature. Placing pins on either side of the trachea can prevent unwanted movement during needle insertion.</li>
		<li>Fill a 26 G syringe with 2-3 mL of 10% neutral buffered formalin and insert into the trachea.</li>
		<li>Slowly inject formalin and watch for the lungs to expand (usually requires ~1.5 mL of formalin).</li>
		<li>Once formalin begins leaking out of the lungs (avoid over inflation), pinch off the trachea with a pair of forceps, remove syringe needle and detach the entire respiratory apparatus. Place lungs, heart, etc. directly into formalin as additional trimming of tissue can be done post-fixation.</li>
		<li>Complete processing, embedding, sectioning of tissue, and hematoxylin and eosin (H&#38;E) staining using standard methods.</li>
	</ol>
	</li>
	<li>Analysis of metastatic lung tumor burden
	<ol>
		<li>Scan H&#38;E-stained lung sections on a high-resolution, slide scanner at 40x magnification (Figure 3).</li>
		<li>Import images into image analysis software (e.g., Visiopharm Image Analysis) for quantification of lung metastases. 
		NOTE: We recommend that new users either obtain onsite or online training to use the image analysis software. Numerous webinars are also available through the commercial webpage.</li>
		<li>Select the Visiopharm 10118 H&#38;E Lung Metastasis App from the software&#8217;s app library. 
		NOTE: The purpose of this app is to label and quantify lung metastasis on H&#38;E-stained slides. As part of the 10118 H&#38;E Lung Metastasis App, the first image processing step segments the lung tissue with the Tissue Detection App. The second image processing step uses the Metastasis Detect App which identifies the metastases inside the lung tissue. Metastases are identified via shape together with regions that are either too misshaped, too red or too sparse for being identified as metastases.</li>
		<li>Adjust the parameters defining shape and sparseness to best fit representative images. Segmented areas of tumor metastases and normal lung tissue can be displayed using different color labels for each tissue type. 
		NOTE: In the event that the app cannot accurately separate metastases from normal lung tissue, a custom app using the Visiopharm Decision Forest program may need to be written as was done for the experiments (see Figure 2 and Figure 3). Details for writing a custom algorithm follow below. Otherwise, proceed to step 2.2.9.</li>
		<li>Open the Decision Forest program, which works by training multiple Classes [i.e., lung tissue (non-neoplastic), metastases, red blood cells, epithelium, and/or white space] on a desired image. In Figure 2, tumor metastases are blue, normal tissue is green, and bronchiolar epithelium is yellow. Also, red blood cells are in red and air spaces in pink.</li>
		<li>Follow the prompted series of yes or no questions to appropriately train each Class for an image. The accuracy of the algorithm will determine the number of yes/no questions. For the analysis, the custom algorithm/app was written with accuracy set to 50 (range 0-100).</li>
		<li>Adjust Features for each class by applying filters to sharpen, blur, sort by shape, etc. to enhance the accuracy of the algorithm/App. Visiopharm views each Class through one or multiple lenses known as Features. Features change how the Class sees the image to bring out certain colors or intensities. 
		NOTE: For the custom algorithm, metastases measuring 8500 &#181;m2 and above are labeled and measured as metastases. This accounts for size variance and metastases too small to detect. Small misshaped areas and small metastatic areas under 8500 &#181;m2 were included in the normal tissue quantification.</li>
		<li>Save the modified settings from either the app or custom algorithm and then, apply the algorithm/app to an entire set or series of H&#38;E-stained tissues.</li>
		<li>Finally, export all output variables, which includes those listed in Table 1. Area in microns squared (&#181;m2) can be quantified for each tissue type and percentages are derived from specimen total net tissue area (i.e., total tissue minus air space).</li>
		<li>When creating a custom algorithm, review tissue markups in consultation with a veterinary pathologist board-certified by the American College of Veterinary Pathologists to ensure accurate measurements and differentiate between tissue types.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

As researchers continue to use intravenous injection of tumor cells as an experimental model for metastasis, standard practices to analyze the resulting metastatic tumor burden are lacking. In some cases, significant differences in metastatic tumor burden upon manipulation of particular cell lines and/or use of chemical compounds can be observed macroscopically. However, in other instances, subtle differences in metastatic seeding and growth may be overlooked or misinterpreted without thorough pathological analysis. This...

An erratum was issued for:&#160;<a href="https://jove.unicartagenaproxy.elogim.com/t/61270/pathological-analysis-lung-metastasis-following-lateral-tail-vein">Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells</a>. The author list was updated.
The author list was updated from:
Katie A. Thies1,&#160;Sue E. Knoblaugh2, and Steven T. Sizemore1 
1Department of Radiation Oncology, Arthur G. James Comprehensive Cancer Center and Richard L. Solove Research Institute, The Ohio State University Medical Center 
2Department of Veterinary Biosciences, Comparative Pathology and Digital Imaging Shared Resource, The Ohio State University
to:
Katie A. Thies1, Sarah Steck1, Sue E. Knoblaugh2, and Steven T. Sizemore1 
1Department of Radiation Oncology, Arthur G. James Comprehensive Cancer Center and Richard L. Solove Research Institute, The Ohio State University Medical Center 
2Department of Veterinary Biosciences, Comparative Pathology and Digital Imaging Shared Resource, The Ohio State University

An erratum was issued for:&#160;<a href="https://jove.unicartagenaproxy.elogim.com/t/61270/pathological-analysis-lung-metastasis-following-lateral-tail-vein">Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells</a>. The author list was updated.

Erratum: Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells

Despite being a highly complex and inefficient process1, metastasis is a significant contributor to the morbidity and mortality of cancer patients2. In fact, most cancer-related deaths are attributed to metastatic spread of disease3,4. In order for tumor cells to successfully metastasize, they must detach from the primary site, invade through adjoining stroma, intravasate into blood circulation or lymphatics, travel to the capillary bed of a secondary site, extravasate into the secondary tissue, and proliferate or grow to form metastatic lesions5. The use of mouse models has been critical to furthering the understanding of the molecular mechanisms responsible for metastatic seeding and growth6,7. Herein, we focus on breast cancer metastasis, for which both genetically modified mouse models as well as methods of transplantation are often used &#8211; each with their own set of advantages and limitations.
Genetically engineered mammary tumor models make use of mammary gland specific promoters, including MMTV-LTR (mouse mammary tumor virus long terminal repeat)&#160;and WAP (Whey Acidic Protein), to drive expression of transgenes in the mammary epithelium8. Oncogenes including polyoma middle T antigen (PyMT), ErbB2/Neu, c-Myc, Wnt-1, and simian virus 40 (SV40) have been expressed in this manner9,10,11,12,13, and while these genetic models are useful for studying primary tumor initiation and progression, few readily metastasize to distant organs. Furthermore, these genetic mouse models are often more time and cost prohibitive than spontaneous or experimental metastasis models. Given the limitation of most genetically engineered mammary tumor models to study metastasis, transplantation techniques have become&#160;attractive methods&#160;to study this complex process. This includes orthotopic, tail-vein, intracardiac, and intracranial injection of suitable cell lines.
Although several breast cancer cell lines readily metastasize following orthotopic injection into the mammary fat pad14,15, the consistency and reproducibility of metastatic tumor burden can be a challenge, and the duration of such studies can be on the order of several months. For evaluating lung metastasis, in particular, intravenous injection into the tail-vein is often a more reproducible and time-effective method with metastatic spread typically occurring within the span of a few weeks. However, since the intravenous injection model&#160;bypasses initial steps of the metastatic cascade, care must be taken in interpreting the results of these studies. In this demonstration, we show tail-vein injection of mammary tumor cells along with an accurate and comprehensive method of analysis.
Even though the research community has made significant progress in understanding the complex process of breast cancer metastasis, it is estimated that over 150,000 women currently have metastatic breast cancer16. Of those with stage IV breast cancer, &#62;36% of patients have lung metastasis17; however, the site-specific pattern and incidence of metastases can vary based on molecular subtype18,19,20,21. Patients with breast cancer-associated lung metastases have a median survival of only 21 months highlighting the need to identify effective treatments and novel biomarkers for this disease17. The use of experimental metastasis models, including the intravenous injection of tumor cells, will continue to advance our knowledge of this important clinical challenge. When combined with digital imaging pathology and the method of metastatic lung tumor burden analysis described within this protocol, tail-vein injections are a valuable tool for breast cancer metastasis research.

<table><tbody><tr><td>alcohol prep pads</td><td>Fisher Scientific</td><td>22-363-750</td><td>&lt;strong&gt;for cleaning tail prior to injection&lt;/strong&gt;</td></tr><tr><td>dissection scissors</td><td>Fisher Scientific</td><td>08-951-5</td><td>&lt;strong&gt;for mouse dissection and lung tissue inflation&lt;/strong&gt;</td></tr><tr><td>DMEM with L-Glutamine, 4.5g/L Glucose and Sodium Pyruvate</td><td>Fisher Scientific</td><td>MT10013CV</td><td>cell culture media base for MDA-MB-231 and MVT1 cell lines</td></tr><tr><td>Dulbecco&#039;s Phosphate-Buffered Salt Solution 1x</td><td>Fisher Scientific</td><td>MT21030CV</td><td>used for resuspending tumor cells for injection</td></tr><tr><td>ethanol (70 % solution)</td><td>OSU</td><td></td><td>used to minimize mouse&#039;s fur during dissection; use caution - flammable</td></tr><tr><td>Evan&#039;s blue dye</td><td>Millipore Sigma</td><td>E2129</td><td>used at 1 % in sterile PBS for practice with tail-vein injection method; use caution - dangerous reagent</td></tr><tr><td>Fetal Bovine Serum</td><td>Millipore Sigma</td><td>F4135</td><td>cell culture media additive; used at 10% in DMEM</td></tr><tr><td>forceps</td><td>Fisher Scientific</td><td>10-270</td><td>for dissection and lung tissue inflation</td></tr><tr><td>FVB/NJ mice</td><td>The Jackson Laboratory</td><td>001800</td><td>syngeneic mouse strain for MVT1 cells</td></tr><tr><td>hemacytometer (Bright-Line)</td><td>Millipore Sigma</td><td>Z359629</td><td>for use in cell culture to obtain cell counts</td></tr><tr><td>insulin syringe (28 G)</td><td>Fisher Scientific</td><td>14-829-1B</td><td>for tail-vein injections (BD 329424)</td></tr><tr><td>MDA-MB-231 cells</td><td>ATCC</td><td></td><td>human breast cancer cell line</td></tr><tr><td>MVT1 cells</td><td></td><td></td><td>mouse mammary tumor cells</td></tr><tr><td>needles (26 G)</td><td>Fisher Scientific</td><td>14-826-15</td><td>used to inflate the mouse&#039;s lungs</td></tr><tr><td>neutral buffered formalin (10%)</td><td>Fisher Scientific</td><td>245685</td><td>used as a tissue fixative and to inflate lung tissue; use caution - dangerous reagent</td></tr><tr><td>NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice</td><td>The Jackson Laboratory</td><td>005557</td><td>maintained by OSUCCC Target Validation Shared Resource</td></tr><tr><td>Penicillin Streptomycin 100x</td><td>ThermoFisher</td><td>15140163</td><td>cell culture media additive</td></tr><tr><td>sterile gauze</td><td>Fisher Scientific</td><td>NC9379092</td><td>for applying pressue to mouse&#039;s tail if bleeding occurs</td></tr><tr><td>syringe (5 mL)</td><td>Fisher Scientific</td><td>14-955-458</td><td>used to inflate mouse lung tissue</td></tr><tr><td>tail-vein restrainer</td><td>Braintree Scientific, Inc.</td><td>TV-150 STD</td><td>used to restrain mouse for tail-vein injections</td></tr><tr><td>Trypan blue (0.4 %)</td><td>ThermoFisher</td><td>15250061</td><td>used in cell culture to assess viability</td></tr><tr><td>Trypsin-EDTA 0.25 %</td><td>ThermoFisher</td><td>25200-114</td><td>used in cell culture to detach tumor cells from plate</td></tr></tbody></table>

pathological analysis of lung metastasis following lateral tail-vein injection of tumor cells

Metastasis, the primary cause of morbidity and mortality for most cancer patients, can be challenging to model preclinically in mice. Few spontaneous metastasis models are available. Thus, the experimental metastasis model involving tail-vein injection of suitable cell lines is a mainstay of metastasis research. When cancer cells are injected into the lateral tail-vein, the lung is their preferred site of colonization. A potential limitation of this technique is the accurate quantification of the metastatic lung tumor burden. While some investigators count macrometastases of a pre-defined size and/or include micrometastases following sectioning of tissue, others determine the area of metastatic lesions relative to normal tissue area. Both of these quantification methods can be exceedingly difficult when the metastatic burden is high. Herein, we demonstrate an intravenous injection model of lung metastasis followed by an advanced method for quantifying metastatic tumor burden using image analysis software. This process allows for investigation of multiple end-point parameters, including average metastasis size, total number of metastases, and total metastasis area, to provide a comprehensive analysis. Furthermore, this method has been reviewed by a veterinary pathologist board-certified by the American College of Veterinary Pathologists (SEK) to ensure accuracy.

If using unlabeled cells for tail-vein injection, it may be difficult to confirm lung colonization until (1) the time of necropsy if macrometastases can be observed or (2) following histological analysis if microscopic metastases exist. With extensive metastatic lung tumor burden, mice will have labored breathing. As with any tumor study, mice should be carefully monitored throughout the study duration. The use of labeled cells is an easy way to confirm successful tail-vein injection; hence the use of luciferase-tagged M...

Watch this Scientific Journal Video about Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells at JoVE.com

Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells

Intravenous injection of cancer cells is often used in metastasis research, but the metastatic tumor burden can be difficult to analyze. Herein, we demonstrate a tail-vein injection model of metastasis and include a novel approach to analyze the resulting metastatic lung tumor burden.

Metastasis, the primary cause of morbidity and mortality for most cancer patients, can be challenging to model preclinically in mice. Few spontaneous ...

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8.7K Views.  The Ohio State University Medical Center. Intravenous injection of cancer cells is often used in metastasis research, but the metastatic tumor burden can be difficult to analyze. Herein, we demonstrate a tail-vein injection model of metastasis and include a novel approach to analyze the resulting metastatic lung tumor burden.

Video: Pathological Analysis of Lung Metastasis Following Lateral Tail-Vein Injection of Tumor Cells

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 ...

Experimental Metastasis Assay

Metastasis is the leading cause of death in cancer patients. To understand the mechanism of metastasis, an experimental metastasis assay was established using immunodeficient mice. This article delineates the procedures involved in this assay, including sample preparation, intravenous injection, and culturing cells from lung metastases. Briefly, a pre-determined number of human cancer cells were prepared in vitro and directly injected into the circulation of immunodeficient mice through their tail veins. A small number of cells survive the turbulence in the circulation and grow as metastases in internal organs, such as lung. The injected mice are dissected after a certain period. The tissue distribution of metastases is determined under a dissecting microscope. The number of metastases in a specific tissue is counted and it directly correlates with the metastatic ability of the injected cancer cells. The arisen metastases are isolated and cultured in vitro as cell lines, which often show enhanced metastatic abilities than the parental line when injected again into immunodeficient mice. These highly metastatic derivatives become useful tools for identifying genes or molecular pathways that regulate metastatic progression.

This article describes the procedures of an experimental metastasis assay that is used to determine the metastatic potential of human cancer cell lines.

Metastasis is the leading cause of death in cancer patients.  To understand the mechanism of metastasis, an experimental metastasis assay was established ...

Medicine

A Portal Vein Injection Model to Study Liver Metastasis of Breast Cancer

Breast cancer is the leading cause of cancer-related mortality in women worldwide. Liver metastasis is involved in upwards of 30% of cases with breast cancer metastasis, and results in poor outcomes with median survival rates of only 4.8 - 15 months. Current rodent models of breast cancer metastasis, including primary tumor cell xenograft and spontaneous tumor models, rarely metastasize to the liver. Intracardiac and intrasplenic injection models do result in liver metastases, however these models can be confounded by concomitant secondary-site metastasis, or by compromised immunity due to removal of the spleen to avoid tumor growth at the injection site. To address the need for improved liver metastasis models, a murine portal vein injection method that delivers tumor cells firstly and directly to the liver was developed. This model delivers tumor cells to the liver without complications of concurrent metastases in other organs or removal of the spleen. The optimized portal vein protocol employs small injection volumes of 5 - 10 &#956;l, &#8805; 32 gauge needles, and hemostatic gauze at the injection site to control for blood loss. The portal vein injection approach in Balb/c female mice using three syngeneic mammary tumor lines of varying metastatic potential was tested; high-metastatic 4T1 cells, moderate-metastatic D2A1 cells, and low-metastatic D2.OR cells. Concentrations of &#8804; 10,000 cells/injection results in a latency of ~ 20 - 40 days for development of liver metastases with the higher metastatic 4T1 and D2A1 lines, and &#62; 55 days for the less aggressive D2.OR line. This model represents an important tool to study breast cancer metastasis to the liver, and may be applicable to other cancers that frequently metastasize to the liver including colorectal and pancreatic adenocarcinomas.

A surgical procedure was developed to deliver mammary tumor cells to the murine liver via portal vein injection. This model permits investigation of late stages of liver metastasis in a fully immune competent host, including tumor cell extravasation, seeding, survival, and metastatic outgrowth in the liver.

Breast cancer is the leading cause of cancer-related mortality in women worldwide. Liver metastasis is involved in upwards of 30% of cases with breast ...

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 ...

Orthotopic Injection of Breast Cancer Cells into the Mice Mammary Fat Pad

A proper animal model is crucial for a better understanding of diseases. Animal models established by different methods (subcutaneous injections, xenografts, genetic manipulation, chemical reagents induction, etc.) have various pathological characters and play important roles in investigating certain aspects of diseases. Although no single model can totally mimic the whole human disease progression, orthotopic organs disease models with a proper stromal environment play an irreplaceable role in understanding diseases and screening for potential drugs. In this article, we describe how to implant breast cancer cells into the mammary fat pad in a simple, less invasive, and easy-to-handle way, and follow the metastasis to distant organs. With the proper features of primary tumor growth, breast and nipple pathological changes, and a high occurrence of other organs&#39; metastasis, this model maximumly mimics human breast cancer progression. Primary tumor growth in situ, long-distant metastasis, and the tumor microenvironment of breast cancer can be investigated by using this model.

Here, we present a protocol to implant breast cancer cells into the mammary fat pad in a simple, less invasive, and easy-to-handle way, and this mouse orthotopic breast cancer model with a proper mammary fat pad environment can be used to investigate various aspects of cancer.

A proper animal model is crucial for a better understanding of diseases. Animal models established by different methods (subcutaneous injections, ...

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 ...

Modeling Brain Metastasis Via Tail-Vein Injection of Inflammatory Breast Cancer Cells

Metastatic spread to the brain is a common and devastating manifestation of many types of cancer. In the United States alone, about 200,000 patients are diagnosed with brain metastases each year. Significant progress has been made in improving survival outcomes for patients with primary breast cancer and systemic malignancies; however, the dismal prognosis for patients with clinical brain metastases highlights the urgent need to develop novel therapeutic agents and strategies against this deadly disease. The lack of suitable experimental models has been one of the major hurdles impeding advancement of our understanding of brain metastasis biology and treatment. Herein, we describe a xenograft mouse model of brain metastasis generated via tail-vein injection of an endogenously HER2-amplified cell line derived from inflammatory breast cancer (IBC), a rare and aggressive form of breast cancer. Cells were labeled with firefly luciferase and green fluorescence protein to monitor brain metastasis, and quantified metastatic burden by bioluminescence imaging, fluorescent stereomicroscopy, and histologic evaluation. Mice robustly and consistently develop brain metastases, allowing investigation of key mediators in the metastatic process and the development of preclinical testing of new treatment strategies.

We describe a xenograft mouse model of breast cancer brain metastasis generated via tail-vein injection of an endogenously HER2-amplified inflammatory breast cancer cell line.

Metastatic spread to the brain is a common and devastating manifestation of many types of cancer. In the United States alone, about 200,000 patients are ...

Orthotopic Injection of Breast Cancer Cells into the Mammary Fat Pad of Mice to Study Tumor Growth.

Breast cancer growth can be studied in mice using a plethora of models. Genetic manipulation of breast cancer cells may provide insights into the functions of proteins involved in oncogenic progression or help to discover new tumor suppressors. In addition, injecting cancer cells into mice with different genotypes might provide a better understanding of the importance of the stromal compartment. Many models may be useful to investigate certain aspects of disease progression but do not recapitulate the entire cancerous process. In contrast, breast cancer cells engraftment to the mammary fat pad of mice better recapitulates the location of the disease and presence of the proper stromal compartment and therefore better mimics human cancerous disease. In this article, we describe how to implant breast cancer cells into mice orthotopically and explain how to collect tissues to analyse the tumor milieu and metastasis to distant organs. Using this model, many aspects (growth, angiogenesis, and metastasis) of cancer can be investigated simply by providing a proper environment for tumor cells to grow.

Cancer is a complex disease that is influenced by the tissue surrounding the tumor as well as local pro- and anti-inflammatory mediators. Therefore, orthotropic injection models, rather than subcutaneous models may be useful to study cancer progression in a manner that better mimics human pathology.

Breast cancer growth can be studied in mice using a plethora of models. Genetic manipulation of breast cancer cells may provide insights into the ...

Injection of Syngeneic Murine Melanoma Cells to Determine Their Metastatic Potential in the Lungs

Approximately 90% of human cancer deaths are linked to metastasis. Despite the prevalence and relative harm of metastasis, therapeutics for treatment or prevention are lacking. We report a method for the establishment of pulmonary metastases in mice, useful for the study of this phenomenon. Tail vein injection of B57BL/6J mice with B16-BL6 is among the most used models for melanoma metastases. Some of the circulating tumor cells establish themselves in the lungs of the mouse, creating "experimental" metastatic foci. With this model it is possible to measure the relative effects of therapeutic agents on the development of cancer metastasis. The difference in enumerated lung foci between treated and untreated mice indicates the efficacy of metastases neutralization. However, prior to the investigation of a therapeutic agent, it is necessary to determine an optimal number of injected B16-BL6 cells for the quantitative analysis of metastatic foci. Injection of too many cells may result in an overabundance of metastatic foci, impairing proper quantification and overwhelming the effects of anti-cancer therapies, while injection of too few cells will hinder the comparison between treated and controls.

Metastasis plays a profound role in the virulence of cancer, accounting for an estimated 90% of deaths. We report a protocol for a metastatic melanoma model in mice that is useful for determining the efficacy of therapeutic agents against this clinical phenomenon.

Approximately 90% of human cancer deaths are linked to metastasis.  Despite the prevalence and relative harm of metastasis, therapeutics for treatment or ...

An Orthotopic Mouse Model of Spontaneous Breast Cancer Metastasis

Metastasis is the primary cause of mortality of breast cancer patients. The mechanism underlying cancer cell metastasis, including breast cancer metastasis, is largely unknown and is a focus in cancer research. Various breast cancer spontaneous metastasis mouse models have been established. Here, we report a simplified procedure to establish orthotopic transplanted breast cancer primary tumor and resultant spontaneous metastasis that mimic human breast cancer metastasis. Combined with the bioluminescence live tumor imaging, this mouse model allows tumor growth and progression kinetics to be monitored and quantified. In this model, a low dose (1 x 104 cells) of 4T1-Luc breast cancer cells was injected into BALB/c mouse mammary fat pad using a tuberculin syringe. Mice were injected with luciferin and imaged at various time points using a bioluminescent imaging system. When the primary tumors grew to the size limit as in the IACUC-approved protocol (approximately 30 days), mice were anesthetized under constant flow of 2% isoflurane and oxygen. The tumor area was sterilized with 70% ethanol. The mouse skin around the tumor was excised to expose the tumor which was removed with a pair of sterile scissors. Removal of the primary tumor extends the survival of the 4T-1 tumor-bearing mice for one month. The mice were then repeatedly imaged for metastatic tumor spreading to distant organs. Therapeutic agents can be administered to suppress tumor metastasis at this point. This model is simple and yet sensitive in quantifying breast cancer cell growth in the primary site and progression kinetics to distant organs, and thus is an excellent model for studying breast cancer growth and progression, and for testing anti-metastasis therapeutic and immunotherapeutic agents in vivo.

An orthotopic breast cancer primary tumor model and surgical removal of primary tumor to extend mouse life to generate spontaneous metastasis are described. The tumor growth and progression are monitored and quantified by luciferase fluorescence imaging.