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>

<ol>
	<li>Chambers, A. F., Groom, A. C., MacDonald, I. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissemination+and+growth+of+cancer+cells+in+metastatic+sites.">Dissemination and growth of cancer cells in metastatic sites.</a> Nature Reviews: Cancer. 2 (8), 563-572 (2002).</li><li>Steeg, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+metastasis.">Targeting metastasis.</a> Nature Reviews: Cancer. 16 (4), 201-218 (2016).</li><li>Gupta, G. P., Massague, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cancer+metastasis:+building+a+framework.">Cancer metastasis: building a framework.</a> Cell. 127 (4), 679-695 (2006).</li><li>Steeg, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+metastasis:+mechanistic+insights+and+clinical+challenges.">Tumor metastasis: mechanistic insights and clinical challenges.</a> Nature Medicine. 12 (8), 895-904 (2006).</li><li>Chaffer, C. L., Weinberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+perspective+on+cancer+cell+metastasis.">A perspective on cancer cell metastasis.</a> Science. 331 (6024), 1559-1564 (2011).</li><li>Eckhardt, B. L., Francis, P. A., Parker, B. S., Anderson, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strategies+for+the+discovery+and+development+of+therapies+for+metastatic+breast+cancer.">Strategies for the discovery and development of therapies for metastatic breast cancer.</a> Nature Reviews Drug Discovery. 11 (6), 479-497 (2012).</li><li>Gomez-Cuadrado, L., Tracey, N., Ma, R., Qian, B., Brunton, V. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+metastasis:+progress+and+prospects.">Mouse models of metastasis: progress and prospects.</a> Disease Models &amp; Mechanisms. 10 (9), 1061-1074 (2017).</li><li>Fantozzi, A., Christofori, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+breast+cancer+metastasis.">Mouse models of breast cancer metastasis.</a> Breast Cancer Research. 8 (4), 212 (2006).</li><li>Schoenenberger, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+c-myc+gene+expression+in+mammary+glands+of+transgenic+mice+induces+mammary+tumours+with+constitutive+milk+protein+gene+transcription.">Targeted c-myc gene expression in mammary glands of transgenic mice induces mammary tumours with constitutive milk protein gene transcription.</a> EMBO Journal. 7 (1), 169-175 (1988).</li><li>Nusse, R., Varmus, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Many+tumors+induced+by+the+mouse+mammary+tumor+virus+contain+a+provirus+integrated+in+the+same+region+of+the+host+genome.">Many tumors induced by the mouse mammary tumor virus contain a provirus integrated in the same region of the host genome.</a> Cell. 31 (1), 99-109 (1982).</li><li>Muller, W. J., Sinn, E., Pattengale, P. K., Wallace, R., Leder, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-step+induction+of+mammary+adenocarcinoma+in+transgenic+mice+bearing+the+activated+c-neu+oncogene.">Single-step induction of mammary adenocarcinoma in transgenic mice bearing the activated c-neu oncogene.</a> Cell. 54 (1), 105-115 (1988).</li><li>Lin, E. Y., 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=Progression+to+malignancy+in+the+polyoma+middle+T+oncoprotein+mouse+breast+cancer+model+provides+a+reliable+model+for+human+diseases.">Progression to malignancy in the polyoma middle T oncoprotein mouse breast cancer model provides a reliable model for human diseases.</a> American Journal of Pathology. 163 (5), 2113-2126 (2003).</li><li>Green, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+C3(1)/SV40+T-antigen+transgenic+mouse+model+of+mammary+cancer:+ductal+epithelial+cell+targeting+with+multistage+progression+to+carcinoma.">The C3(1)/SV40 T-antigen transgenic mouse model of mammary cancer: ductal epithelial cell targeting with multistage progression to carcinoma.</a> Oncogene. 19 (1), 1020-1027 (2000).</li><li>Iorns, E., 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=A+new+mouse+model+for+the+study+of+human+breast+cancer+metastasis.">A new mouse model for the study of human breast cancer metastasis.</a> PloS One. 7 (10), 47995 (2012).</li><li>Kim, I. S., Baek, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+for+breast+cancer+metastasis.">Mouse models for breast cancer metastasis.</a> Biochemical and Biophysical Research Communications. 394 (3), 443-447 (2010).</li><li>Mariotto, A. B., Etzioni, R., Hurlbert, M., Penberthy, L., Mayer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimation+of+the+Number+of+Women+Living+with+Metastatic+Breast+Cancer+in+the+United+States.">Estimation of the Number of Women Living with Metastatic Breast Cancer in the United States.</a> Cancer Epidemiology, Biomarkers and Prevention. 26 (6), 809-815 (2017).</li><li>Xiao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risk+factors+and+survival+outcomes+in+patients+with+breast+cancer+and+lung+metastasis:+a+population-based+study.">Risk factors and survival outcomes in patients with breast cancer and lung metastasis: a population-based study.</a> Cancer Medicine. 7 (3), 922-930 (2018).</li><li>Smid, 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=Subtypes+of+breast+cancer+show+preferential+site+of+relapse.">Subtypes of breast cancer show preferential site of relapse.</a> Cancer Research. 68 (9), 3108-3114 (2008).</li><li>Kennecke, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metastatic+behavior+of+breast+cancer+subtypes.">Metastatic behavior of breast cancer subtypes.</a> Journal of Clinical Oncology. 28 (20), 3271-3277 (2010).</li><li>Soni, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Breast+cancer+subtypes+predispose+the+site+of+distant+metastases.">Breast cancer subtypes predispose the site of distant metastases.</a> American Journal of Clinical Pathology. 143 (4), 471-478 (2015).</li><li>Leone, B. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prognostic+impact+of+metastatic+pattern+in+stage+IV+breast+cancer+at+initial+diagnosis.">Prognostic impact of metastatic pattern in stage IV breast cancer at initial diagnosis.</a> Breast Cancer Research and Treatment. 161 (3), 537-548 (2017).</li><li>Pei, X. 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=Explant-cell+culture+of+primary+mammary+tumors+from+MMTV-c-Myc+transgenic+mice.">Explant-cell culture of primary mammary tumors from MMTV-c-Myc transgenic mice.</a> In Vitro Cellular and Developmental Biology: Animal. 40 (1-2), 14-21 (2004).</li><li>Mathsyaraja, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CSF1-ETS2-induced+microRNA+in+myeloid+cells+promote+metastatic+tumor+growth.">CSF1-ETS2-induced microRNA in myeloid cells promote metastatic tumor growth.</a> Oncogene. 34 (28), 3651-3661 (2015).</li><li>Yang, S., Zhang, J. J., Huang, X. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+for+tumor+metastasis.">Mouse models for tumor metastasis.</a> Methods in Molecular Biology. 928, 221-228 (2012).</li><li>La Perle, K. M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+Pathologists:+Ultimate+Control+Freaks+Seeking+Validation.">Comparative Pathologists: Ultimate Control Freaks Seeking Validation.</a> Veterinary Pathology. 56 (1), 19-23 (2019).</li><li>Blomberg, O. S., Spagnuolo, L., de Visser, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immune+regulation+of+metastasis:+mechanistic+insights+and+therapeutic+opportunities.">Immune regulation of metastasis: mechanistic insights and therapeutic opportunities.</a> Disease Models &amp; Mechanisms. 11 (10), (2018).</li><li>Gonzalez, H., Hagerling, C., Werb, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Roles+of+the+immune+system+in+cancer:+from+tumor+initiation+to+metastatic+progression.">Roles of the immune system in cancer: from tumor initiation to metastatic progression.</a> Genes and Development. 32 (19-20), 1267-1284 (2018).</li><li>Borowsky, A. D., 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=Syngeneic+mouse+mammary+carcinoma+cell+lines:+two+closely+related+cell+lines+with+divergent+metastatic+behavior.">Syngeneic mouse mammary carcinoma cell lines: two closely related cell lines with divergent metastatic behavior.</a> Clinical and Experimental Metastasis. 22 (1), 47-59 (2005).</li><li>Yang, Y., 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=Immunocompetent+mouse+allograft+models+for+development+of+therapies+to+target+breast+cancer+metastasis.">Immunocompetent mouse allograft models for development of therapies to target breast cancer metastasis.</a> Oncotarget. 8 (19), 30621-30643 (2017).</li><li>Resch, M., Neels, T., Tichy, A., Palme, R., Rulicke, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+assessment+of+tail-vein+injection+in+mice+using+a+modified+anaesthesia+induction+chamber+versus+a+common+restrainer+without+anaesthesia.">Impact assessment of tail-vein injection in mice using a modified anaesthesia induction chamber versus a common restrainer without anaesthesia.</a> Laboratory Animals. 53 (2), 190-201 (2019).</li><li>Rashid, O. 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=Is+tail+vein+injection+a+relevant+breast+cancer+lung+metastasis+model.">Is tail vein injection a relevant breast cancer lung metastasis model.</a> Journal of Thoracic Disease. 5 (4), 385-392 (2013).</li><li>Goodale, D., Phay, C., Postenka, C. O., Keeney, M., Allan, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+tumor+cell+dissemination+patterns+in+preclinical+models+of+cancer+metastasis+using+flow+cytometry+and+laser+scanning+cytometry.">Characterization of tumor cell dissemination patterns in preclinical models of cancer metastasis using flow cytometry and laser scanning cytometry.</a> Cytometry Part A. 75 (4), 344-355 (2009).</li><li>Goddard, E. T., Fischer, J., Schedin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Portal+Vein+Injection+Model+to+Study+Liver+Metastasis+of+Breast+Cancer.">A Portal Vein Injection Model to Study Liver Metastasis of Breast Cancer.</a> Journal of Visualized Experiments. (118), (2016).</li><li>Wright, L. E., 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=Murine+models+of+breast+cancer+bone+metastasis.">Murine models of breast cancer bone metastasis.</a> BoneKEy Reports. 5, 804 (2016).</li><li>Simmons, J. K., 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=Animal+Models+of+Bone+Metastasis.">Animal Models of Bone Metastasis.</a> Veterinary Pathology. 52 (5), 827-841 (2015).</li><li>Liu, Z., 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=Improving+orthotopic+mouse+models+of+patient-derived+breast+cancer+brain+metastases+by+a+modified+intracarotid+injection+method.">Improving orthotopic mouse models of patient-derived breast cancer brain metastases by a modified intracarotid injection method.</a> Scientific Reports. 9 (1), 622 (2019).</li><li>Kodack, D. P., Askoxylakis, V., Ferraro, G. B., Fukumura, D., Jain, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emerging+strategies+for+treating+brain+metastases+from+breast+cancer.">Emerging strategies for treating brain metastases from breast cancer.</a> Cancer Cell. 27 (2), 163-175 (2015).</li><li>Brown, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Practical+Stereology+Applications+for+the+Pathologist.">Practical Stereology Applications for the Pathologist.</a> Veterinary Pathology. 54 (3), 358-368 (2017).</li><li>Aeffner, 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=Digital+Microscopy,+Image+Analysis,+and+Virtual+Slide+Repository.">Digital Microscopy, Image Analysis, and Virtual Slide Repository.</a> Institute for Laboratory Animal Research Journal. 59 (1), 66-79 (2018).</li></ol>

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://www.jove.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://www.jove.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>for cleaning tail prior to injection</td>
		</tr>
		<tr>
			<td>dissection scissors</td>
			<td>Fisher Scientific</td>
			<td>08-951-5</td>
			<td>for mouse dissection and lung tissue inflation</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&#39;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&#39;s fur during dissection; use caution - flammable</td>
		</tr>
		<tr>
			<td>Evan&#39;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&#39;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&#39;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 ...

pathological-analysis-lung-metastasis-following-lateral-tail-vein

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8.6K 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 ...

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 ...

Intracarotid Cancer Cell Injection to Produce Mouse Models of Brain Metastasis

Metastasis, the spread and growth of malignant cells at secondary sites within a patient&#39;s body, accounts for &#62; 90% of cancer-related mortality. Recently, impressive advances in novel therapies have dramatically prolonged survival and improved quality of life for many cancer patients. Sadly, incidence of brain metastatic recurrences is fast rising, and all current therapies are merely palliative. Hence, good experimental animal models are urgently needed to facilitate in-depth studies of the disease biology and to assess novel therapeutic regimens for preclinical evaluation. However, the standard in vivo metastasis assay via tail vein injection of cancer cells produces predominantly lung metastatic lesions; animals usually succumb to the lung tumor burden before any meaningful outgrowth of brain metastasis. Intracardiac injection of tumor cells produces metastatic lesions to multiple organ sites including the brain; however, the variability of tumor growth produced with this model is large, dampening its utility in evaluating therapeutic efficacy. To generate reliable and consistent animal models for brain metastasis study, here we describe a procedure for producing experimental brain metastasis in the house mouse (Mus musculus) via intracarotid injection of tumor cells. This approach allows one to produce large number of brain metastasis-bearing mice with similar growth and mortality characteristics, thus facilitating research efforts to study basic biological mechanisms and to assess novel therapeutic agents.

Brain metastasis has become an urgent unmet medical need as its incidence has increased while therapeutic options have remained palliative. Creating experimental animal models of brain metastasis via intracarotid arterial injection of cancer cells facilitates mechanistic studies of the disease biology and evaluation of novel intervention regimens.

Metastasis, the spread and growth of malignant cells at secondary sites within a patient&#39;s body, accounts for &#62; 90% of cancer-related mortality. ...

Simple and Rapid Method to Obtain High-quality Tumor DNA from Clinical-pathological Specimens Using Touch Imprint Cytology

It is critical to determine the mutational status in cancer before administration and treatment of specific molecular targeted drugs for cancer patients. In the clinical setting, formalin-fixed paraffin-embedded (FFPE) tissues are widely used for genetic testing. However, FFPE DNA is generally damaged and fragmented during the fixation process with formalin. Therefore, FFPE DNA is sometimes not adequate for genetic testing because of low quality and quantity of DNA. Here we present a method of touch imprint cytology (TIC) to obtain genomic DNA from cancer cells, which can be observed under a microscope. Cell morphology and cancer cell numbers can be evaluated using TIC specimens. Furthermore, the extraction of genomic DNA from TIC samples can be completed within two days. The total amount and quality of TIC DNA obtained using this method was higher than that of FFPE DNA. This rapid and simple method allows researchers to obtain high-quality DNA for genetic testing (e.g., next generation sequencing analysis, digital PCR, and quantitative real time PCR) and to shorten the turnaround time for reporting results.

Obtaining high-quality genomic DNA from tumor tissues is an essential first step for analyzing genetic alterations using next generation sequencing. In this article, we present a simple and rapid method to enrich tumor cells and obtain intact DNA from touch imprint cytology specimens.

It is critical to determine the mutational status in cancer before administration and treatment of specific molecular targeted drugs for cancer patients. ...

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 ...

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 ...

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 ...

Using Computer-based Image Analysis to Improve Quantification of Lung Metastasis in the 4T1 Breast Cancer Model

Breast cancer is a devastating malignancy, accounting for 40,000 female deaths and 30% of new female cancer diagnoses in the United States in 2019 alone. The leading cause of breast cancer related deaths is the metastatic burden. Therefore, preclinical models for breast cancer need to analyze metastatic burden to be clinically relevant. The 4T1 breast cancer model provides a spontaneously-metastasizing, quantifiable mouse model for stage IV human breast cancer. However, most 4T1 protocols quantify the metastatic burden by manually counting stained colonies on tissue culture plates. While this is sufficient for tissues with lower metastatic burden, human error in manual counting causes inconsistent and variable results when plates are confluent and difficult to count. This method offers a computer-based solution to human counting error. Here, we evaluate the protocol using the lung, a highly metastatic tissue in the 4T1 model. Images of methylene blue-stained plates are acquired and uploaded for analysis in Fiji-ImageJ. Fiji-ImageJ then determines the percentage of the selected area of the image that is blue, representing the percentage of the plate with metastatic burden. This computer-based approach offers more consistent and expeditious results than manual counting or histopathological evaluation for highly metastatic tissues. The consistency of Fiji-ImageJ results depends on the quality of the image. Slight variations in results between images can occur, thus it is recommended that multiple images are taken and results averaged. Despite its minimal limitations, this method is an improvement to quantifying metastatic burden in the lung by offering consistent and rapid results.

We describe a more consistent and expeditious method to quantify lung metastasis in the 4T1 breast cancer model by using Fiji-ImageJ.

Breast cancer is a devastating malignancy, accounting for 40,000 female deaths and 30% of new female cancer diagnoses in the United States in 2019 alone. ...

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 ...

Portal Vein Injection of Colorectal Cancer Organoids to Study the Liver Metastasis Stroma

Hepatic metastasis of colorectal cancer (CRC) is a leading cause of cancer-related death. Cancer-associated fibroblasts (CAFs), a major component of the tumor microenvironment, play a crucial role in metastatic CRC progression and predict poor patient prognosis. However, there is a lack of satisfactory mouse models to study the crosstalk between metastatic cancer cells and CAFs. Here, we present a method to investigate how liver metastasis progression is regulated by the metastatic niche and possibly could be restrained by stroma-directed therapy. Portal vein injection of CRC organoids generated a desmoplastic reaction, which faithfully recapitulated the fibroblast-rich histology of human CRC liver metastases. This model was tissue-specific with a higher tumor burden in the liver when compared to an intra-splenic injection model, simplifying mouse survival analyses. By injecting luciferase-expressing tumor organoids, tumor growth kinetics could be monitored by in vivo imaging. Moreover, this preclinical model provides a useful platform to assess the efficacy of therapeutics targeting the tumor mesenchyme. We describe methods to examine whether adeno-associated virus-mediated delivery of a tumor-inhibiting stromal gene to hepatocytes could remodel the tumor microenvironment and improve mouse survival. This approach enables the development and assessment of novel therapeutic strategies to inhibit hepatic metastasis of CRC.

Portal vein injection of colorectal cancer (CRC) organoids generates stroma-rich liver metastasis. This mouse model of CRC hepatic metastasis represents a useful tool to study tumor-stroma interactions and develop novel stroma-directed therapeutics such as adeno-associated virus-mediated gene therapies.

Hepatic metastasis of colorectal cancer (CRC) is a leading cause of cancer-related death. Cancer-associated fibroblasts (CAFs), a major component of the ...