The authors would like to acknowledge the Netherlands Organization for Scientific Research (NWO, grant 17.106.329)

Animal experiments were approved by the animal welfare committee of the Leiden University Medical Center(LUMC).
1. Preparation of Cells, Instruments and Mice
<ol>
	<li>A day before operation, shave the NOD/SCID gamma (NSG) mice from the fourth nipple to the midline and weigh the mice to verify that all mice have roughly comparable weights.</li>
	<li>Autoclave a scissor, two tweezers and two straight mosquito forceps (Figure 1A) .</li>
	<li>On the day of operation, wash the human breast adenocarcinoma (MDA-MB-231) cells that will be injected once with phosphate buffered saline (PBS), pH 7.4 and trypsinize the cells. Quench the trypsin by adding 10 ml serum-containing DMEM media on top of the cells. Centrifuge the cells at 1,200 rpm for 7 min at RT to remove serum by resuspending the cells either in PBS or in media without serum. Centrifuge them again to remove traces of serum completely. Resuspend the cells in PBS or media.</li>
	<li>Count the cells with a hemocytometer and calculate the amount of cells. Use 500,000 cells/mouse in not more than 150 &#956;l. Optional to PBS or media, resuspend the cells in matrigel. 
	NOTE: Determine the amount of cells depending on the cell type used.</li>
	<li>Place cells in a sterile microcentrifuge tubes and keep them on ice.</li>
	<li>Fill one 50 ml conical centrifuge tube with 35 ml of PBS pH 7.4 and another 50ml conical centrifuge tube with 70% ethanol. Soak cotton swabs into each tube.</li>
</ol>
2. Orthotopic Injection
<ol>
	<li>Perform the surgery in a sterile hood to maintain a sterile atmosphere. Anesthetize the mouse by subcutaneously injecting Xylazin/Ketamine mix at a dose of 10mg/kg, 100 mg/kg body weight respectively. Fix the mouse on a heating pad. Confirm the success of anesthesia by the lack of reaction to toe pinch. 
	NOTE: If one is not very familiar with surgical procedures, surgery may take longer. Arrange the anaesthesia dose accordingly.</li>
	<li>Apply ophthalmic ointment on the eyes of mice, to prevent the eyes from drying out.</li>
	<li>Clean the shaved area by using the cotton swab dipped into ethanol prepared in step 1.6. Alternating scrubs using betadine and alcohol three times in a circular fashion rotating away from the planned incision site should be performed. Alternatively, use ionophore as a disinfectant.</li>
	<li>Make a small incision between the fourth nipple and the midline with a scissor and make a pocket by inserting the cotton swab moistened with PBS pH 7.4.</li>
	<li>Use a tweezer to expose the mammary fat pad. Observe the fat pad by its white colour.</li>
	<li>Squeeze the fat pad with the other tweezer from its base; by doing this, fully expose the fat pad (Figure 1B) to perform injections easily.</li>
	<li>Homogenize the cell mixture by pipetting up and down. Gently aspirate 50 &#181;l of cell suspension into an insulin syringe and inject into the mammary fat pad by holding the needle horizontally. Confirm successful injection by checking for swelling of the fat pad.</li>
	<li>Release the fat pad gently.</li>
	<li>Suture the incision by using a needle driver. Make three throws by turning the suture around the needle driver in clockwise, anti-clockwise and clockwise direction. Two knots per suture should be used. 
	NOTE: Make sure the knots are tight otherwise mice can open up the sutures.</li>
	<li>After surgery, inject an analgesic, such as temgesic at 0.05-0.1 mg/kg bodyweight, subcutaneously in order to relieve the pain.</li>
	<li>Do not leave the animals unattended until they gain consciousness and maintain sternal recumbence. Place all the animals into different cages until they are fully recovered.</li>
	<li>To maintain sterility, use autoclaved cages and water. Change the cages every three days to keep the atmosphere clean.</li>
</ol>
3. Harvesting Organs for Analysis
<ol>
	<li>At the day of harvest, 8 weeks after the implantation of the cells, fill 15 ml conical centrifuge tubes with 3 ml Bouin&#8217;s solution for each mouse. In addition, use two 15 ml tubes filled with 5 ml formalin solution per mouse.</li>
	<li>Anesthetize the animals by injecting Xylazin/Ketamine, at a dose of 10 mg/kg 100 mg/kg body weight subcutaneously. Wait until the animal loses toe pinch withdrawal reflex.</li>
	<li>Fix the animal with needles on a base. Make a long, vertical midline incision with scissors. Make two horizontal incisions right below the front leg and above the rear leg. Expose the tumor by pinning the skin to the base. Measure the tumor volume by using a caliper.</li>
	<li>Dissociate the tumor from the skin using scissors. Snap freeze a part of the tumor in liquid nitrogen for RNA isolation. Place the other part, into the conical centrifuge tube filled with formalin to perform immunohistochemistry following paraffin embedding.</li>
	<li>Gently take out the lungs. Place the left lung into Bouin&#8217;s solution. Keep the lung in solution for 3 days. Observe superficial metastatic foci clearly to naked eye. Optionally, place the right lung into formalin to verify micrometastasis using haematoxylin and eosin (H&#38;E) staining. 
	NOTE: Although, lung metastasis observed frequently in breast cancer, one might also want to collect bone, liver, brain and spleen to analyse metastasis. The cells at the metastatic area are denser and morphologically different and therefore can be distinguished easily from lung tissue.</li>
	<li>A day after harvest, aspirate the formalin solution from 15 ml tubes and replace with 70% ethanol. Embed the tissues in paraffin and perform immunohistochemistry studies.</li>
	<li>For blood analysis, open up the chest cavity with scissors. Withdraw 450 &#181;l blood via cardiac puncture. Place blood sample in a microcentrifuge tube containing 50 &#181;l of 3.2% sodium citrate. After blood is collected, spin it at 2,000 x g for 10 min. Store the plasma samples at -20 &#176;C until further use. 
	NOTE: There are several other blood collection techniques commonly used in practice20 and the technique that needs to be used depends on experimental setup and scientist&#8217;s choice. If blood sample is not required, euthanize the animal according to the animal protocol or as per the institution guidelines.</li>
</ol>

<ol>
	<li>Aaronson, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+factors+and+cancer.">Growth factors and cancer.</a> Science. 254 (5035), 1146-1153 (1991).</li><li>Bao, L., Matsumura, Y., Baban, D., Sun, Y., Tarin, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+inoculation+site+and+Matrigel+on+growth+and+metastasis+of+human+breast+cancer+cells.">Effects of inoculation site and Matrigel on growth and metastasis of human breast cancer cells.</a> Br. J. Cancer. 70 (2), 228-232 (1994).</li><li>Brouxhon, S. 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=Monoclonal+antibody+against+the+ectodomain+of+E-cadherin+(DECMA-1)+suppresses+breast+carcinogenesis:+involvement+of+the+HER/PI3K/Akt/mTOR+and+IAP+pathways.">Monoclonal antibody against the ectodomain of E-cadherin (DECMA-1) suppresses breast carcinogenesis: involvement of the HER/PI3K/Akt/mTOR and IAP pathways.</a> Clin. Cancer Res. 19 (12), 3234-3246 (2013).</li><li>Dobie, K. 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=Variegated+transgene+expression+in+mouse+mammary+gland+is+determined+by+the+transgene+integration+locus.">Variegated transgene expression in mouse mammary gland is determined by the transgene integration locus.</a> Proc. Natl. Acad. Sci. U S A. 93 (13), 6659-6664 (1996).</li><li>Ewens, A., Mihich, E., Ehrke, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distant+metastasis+from+subcutaneously+grown+E0771+medullary+breast+adenocarcinoma.">Distant metastasis from subcutaneously grown E0771 medullary breast adenocarcinoma.</a> Anticancer Res. 25 (6B), 3905-3915 (2005).</li><li>Fidler, I. J., Naito, S., Pathak, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Orthotopic+implantation+is+essential+for+the+selection,+growth+and+metastasis+of+human+renal+cell+cancer+in+nude+mice+[corrected.">Orthotopic implantation is essential for the selection, growth and metastasis of human renal cell cancer in nude mice [corrected.</a> Cancer Metastasis Rev. 9 (2), 149-165 (1990).</li><li>Fridman, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+tumor+growth+of+both+primary+and+established+human+and+murine+tumor+cells+in+athymic+mice+after+coinjection+with+Matrigel.">Enhanced tumor growth of both primary and established human and murine tumor cells in athymic mice after coinjection with Matrigel.</a> J. Natl. Cancer Inst. 83 (11), 769-774 (1991).</li><li>Fynan, T. M., Reiss, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resistance+to+inhibition+of+cell+growth+by+transforming+growth+factor-beta+and+its+role+in+oncogenesis.">Resistance to inhibition of cell growth by transforming growth factor-beta and its role in oncogenesis.</a> Crit Rev. Oncog. 4 (5), 493-540 (1993).</li><li>Huang, H. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trypsin-induced+proteome+alteration+during+cell+subculture+in+mammalian+cells.">Trypsin-induced proteome alteration during cell subculture in mammalian cells.</a> J. Biomed. Sci. 17, 36 (2010).</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), e47995 (2012).</li><li>Jessani, N., Niessen, S., Mueller, B. M., Cravatt, B. F. <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+cell+lines+grown+in+vivo:+what+goes+in+isn't+always+the+same+as+what+comes+out.">Breast cancer cell lines grown in vivo: what goes in isn't always the same as what comes out.</a> Cell Cycle. 4 (2), 253-255 (2005).</li><li>Kalluri, R., 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=The+basics+of+epithelial-mesenchymal+transition.">The basics of epithelial-mesenchymal transition.</a> J. Clin. Invest. 119 (6), 1420-1428 (2009).</li><li>Kocaturk, B., 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=Alternatively+spliced+tissue+factor+promotes+breast+cancer+growth+in+a+beta1+integrin-dependent+manner.">Alternatively spliced tissue factor promotes breast cancer growth in a beta1 integrin-dependent manner.</a> Proc. Natl. Acad. Sci. U S A. 110, 11517-11522 (2013).</li><li>Lowe, S. W., Lin, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis+in+cancer.">Apoptosis in cancer.</a> Carcinogenesis. 21 (3), 485-495 (2000).</li><li>Meek, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+p53+response+to+DNA+damage.">The p53 response to DNA damage.</a> DNA Repair (Amst). 3 (8-9), 1049-1056 (2004).</li><li>Meek, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+suppression+by+p53:+a+role+for+the+DNA+damage+response).">Tumor suppression by p53: a role for the DNA damage response).</a> Nat. Rev. Cancer. 9 (10), 714-723 (2009).</li><li>Miller, F. R., Medina, D., Heppner, G. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preferential+growth+of+mammary+tumors+in+intact+mammary+fatpads.">Preferential growth of mammary tumors in intact mammary fatpads.</a> Cancer Res. 41 (10), 3863-3867 (1981).</li><li>Mueller, B. M., Ruf, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Requirement+for+binding+of+catalytically+active+factor+VIIa+in+tissue+factor-dependent+experimental+metastasis.">Requirement for binding of catalytically active factor VIIa in tissue factor-dependent experimental metastasis.</a> J. Clin. Invest. 101 (7), 1372-1378 (1998).</li><li>Paoli, P., Giannoni, E., Chiarugi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anoikis+molecular+pathways+and+its+role+in+cancer+progression.">Anoikis molecular pathways and its role in cancer progression.</a> Biochim. Biophys. Acta. 1833 (12), 3481-3498 (2013).</li><li>Parasuraman, S., Raveendran, R., Kesavan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+sample+collection+in+small+laboratory+animals.">Blood sample collection in small laboratory animals.</a> J. Pharmacol. Pharmacother. 1 (2), 87-93 (2010).</li><li>Shay, J. W., Zou, Y., Hiyama, E., Qright, W. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Telomerase+and+cancer.">Telomerase and cancer.</a> Hum. Mol. Genet.. 10 (7), 677-685 (2001).</li><li>Sporn, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+war+on+cancer.">The war on cancer.</a> Lancet. 347 (9012), 1377-1381 (1996).</li><li>Tao, K., Fang, M., Alroy, J., Sahagian, G. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imagable+4T1+model+for+the+study+of+late+stage+breast+cancer.">Imagable 4T1 model for the study of late stage breast cancer.</a> BMC. Cancer. 8, 228 (2008).</li><li>Versteeg, H. 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=Protease-activated+receptor+(PAR)+2,+but+not+PAR1,+signaling+promotes+the+development+of+mammary+adenocarcinoma+in+polyoma+middle+T+mice.">Protease-activated receptor (PAR) 2, but not PAR1, signaling promotes the development of mammary adenocarcinoma in polyoma middle T mice.</a> Cancer Res. 68 (17), 7219-7227 (2008).</li><li>Versteeg, H. 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=Inhibition+of+tissue+factor+signaling+suppresses+tumor+growth.">Inhibition of tissue factor signaling suppresses tumor growth.</a> Blood. 111 (1), 190-199 (2008).</li><li>Wagner, K. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+of+breast+cancer:+quo+vadis,+animal+modeling?.">Models of breast cancer: quo vadis, animal modeling?.</a> Breast Cancer Res. 6 (1), 31-38 (2004).</li><li>Weigelt, B., Peterse, J. L., van't Veer, L. J. <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+metastasis:+markers+and+models.">Breast cancer metastasis: markers and models.</a> Nat. Rev. Cancer. 5 (8), 591-602 (2005).</li></ol>

The authors declare that they have no competing financial interests.

Orthotopic injection of breast cancer cells is a powerful model to study all aspects of cancer growth. Implantation of these cells in the mammary fat pad of the mice should be carefully performed in order to prevent variation in tumor growth. Most importantly, injecting the same amount of cells to each mouse is crucial. To do so, one should trypsinize the cells rigorously without affecting viability of the cells. Non-viable cells should be disregarded during the cell counting and reagents (i.e. trypan blue) that...

Cancer is a very complex disease that has been subject to studies for over centuries. Breast cancer is the most common cancer type; it occurs predominantly in females but may sporadically also occur in males27. The disease is mainly caused by the loss of control mechanism governing cell division which in turn leads to an infinite growth of cells in the body. These malfunctions can be caused by several mechanisms: first, healthy cells need growth signals from the surrounding cells in order to proliferate whereas cancer cells make their own growth factors and increase the expression of growth factor receptors thus obtaining a higher proliferative rate1; second, cancer cells are less susceptible to anti-proliferative signals8; third, to balance the cell number in the body cell death is also required; however, cancer cells escape from programmed cell death, termed apoptosis14; fourth, cells adhere to extracellular matrices in order to survive but tumor cells can grow without the need of attachment and show resistance to anoikis19; fifth, activation of telomerase circumvents the telomere shortening and prevents the replicative senescence21; last but not least, skipping of DNA quality control following mitosis results in altered genetic content15,16. In order to identify oncogenes or tumor suppressors that play a role in this deregulated proliferation, tumor growth experiments in mice are crucial.
Primary tumor growth is generally not the main reason of death. Migration of cancer cells from the primary site to a secondary site, termed metastasis, is the leading cause of death in most cancer patients22. Metastasis entails tumor cell invasion, intravasation, travelling through the circulation, avoiding immune attack, extravasation and growth at the secondary site. Epithelial to mesenchymal transition (EMT) is a key process in metastasis and involves a switch in gene expression profiles yielding cells with higher motility and invasiveness, which are pre-requisites for the metastasizing cell12. As the cancerous process is the resultant of a combination of various actions, including reciprocal interactions between cancer cells, stromal cells and pro- and anti-inflammatory cells, an in vitro approach to cancer often does not provide full insight into the cancerous process. Similarly, anticancer treatments impacting the tumor vasculature can often not be studied in vitro, thus the use of in vivo approaches is inevitable.
To study breast cancer progression, different experimental methods have been developed. The most widely used model is the subcutaneous injection of breast cancer cells into mice5. In this experimental setup, the investigator may introduce a wide range of alterations to a cell line of choice in vitro (i.e. upregulation, downregulation of proteins) and inject the cells under the skin. Although this method is straightforward and the injection process is simple without any need to perform surgery on the mice, the site at which the tumor is injected does not represent the local mammary tumor environment and the absence of this environment may result in breast cancer development that differs from that observed in human pathology. Secondly, genetically engineered mice are used frequently as an in vivo tool to study breast cancer progression. In this model, oncogene (i.e. PyMT, Neu) expression is driven by a mammary tissue specific promoter leading to the formation of spontaneous breast tumor s. This experimental setup is useful to study the treatment aspect of the disease by injecting drugs or antibodies while checking tumor size in time3. However, breeding these mice with other mouse strains deficient or mutated in a gene of interest might also give insights into the role of different proteins in breast tumor growth24. The downside of this model is that it is prone to variation in tumor size and number. Moreover, the level of transgene expression depends on the integration site in the genome and can change from one mouse strain to another4. In this model, the expression of the transgene can be achieved by all the cells with epithelial origin whereas in human disease, only a subpopulation of cells express the oncogene or downregulate the tumor suppressor levels26. To study metastasis, breast cancer cells may also be injected intravenously (a model termed experimental metastasis)25. However, this approach only recapitulates the metastatic process partially; it circumvents the requirement for tumor cells to invade and intravasate, and starts from the point at which tumor cells are readily present in the circulation.
In our work, we use an orthotopic injection model to study the involvement of genes of interest in breast cancer progression13. We overexpress the protein in human breast cancer cells and inject them into the mammary fat pad of NOD/SCID gamma (NSG) mice. This method is advantageous in many ways: it allows very rapid and diverse genetic changes in the injected cell line, it covers the entire process of breast cancer progression from primary tumor growth to metastasis at pathologically relevant sites, and it also provides a good experimental model for studying the impact of therapeutic treatments at early or late stages of the disease. In addition, using this model one can investigate the role of stromal versus cancer cell-derived proteins in disease progression by using genetically modified mice or cells. Although subcutaneous injections are easier to perform, orthotopic models give rise to a more tumorigenic and more metastatic cancer cell population. Thus, results obtained by means of the subcutaneous injections might be either false-negative or false-positive6,17 encouraging the use of orthotopic models to study the tumor growth.

<table border="0" cellpadding="0" cellspacing="0" width="1093">
	<tbody>
		<tr height="17">
			<td height="17" style="height:17px;width:185px;">Name of material/equipment</td>
			<td style="width:172px;">Company</td>
			<td style="width:95px;">Catalog number</td>
			<td style="width:641px;">Comments/Description</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Bouin&#39;s solution</td>
			<td>Sigma-Aldrich</td>
			<td>HT10132</td>
			<td>Used for investigating the metastasis on lungs</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Formalin solution</td>
			<td>Sigma-Aldrich</td>
			<td>HT501128</td>
			<td>Used to fix the tissues</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Matrigel, growth factor reduced</td>
			<td>Corning</td>
			<td>356230</td>
			<td>Cells can be resuspended in matrigel for injection</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Mosquito forceps</td>
			<td>Fine Science Tools</td>
			<td>13008-12</td>
			<td>Used for stiching</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Angled forceps</td>
			<td>Electron microscopy sciences</td>
			<td>72991-4c</td>
			<td>These make the exposure of mammary fat pad easier</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Scissors</td>
			<td>B Braun Medicals</td>
			<td>BC056R</td>
			<td>Used to cut open the mice</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Straight forceps</td>
			<td>B Braun Medicals</td>
			<td>BD025R</td>
			<td>This is used to open up the skin to expose mammary fat pad</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">NOD scid gamma mice</td>
			<td>Charles River</td>
			<td>005557</td>
			<td>Experimental animal used for experiment</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MDA-MB-231</td>
			<td>Sigma-Aldrich</td>
			<td>92020424</td>
			<td>Experimental cells used for injections</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Oculentum simplex</td>
			<td>Teva Pharmachemie</td>
			<td></td>
			<td>Opthalmic ointment used to prevent drying out of eyes</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Betadine</td>
			<td>Fischer Scientific</td>
			<td>19-898-859</td>
			<td>Ionophore, used to disinfect the surgical area</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Xylazin/Ketamine</td>
			<td>Sigma-Aldrich</td>
			<td>X1251, K2753</td>
			<td>Use injected anesthesia as 10mg/kg and 100mg/kg body weight respectively</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Temgesic</td>
			<td>Schering-Plough</td>
			<td></td>
			<td>Use the painkiller as 0,05-0,1mg/kg body weight</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">DMEM</td>
			<td>Life sciences</td>
			<td>11995</td>
			<td>For trypsin neutralization,use media with serum(FBS:media 1:10 volume); for injection, use media with no serum</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Buffered sodium citrate</td>
			<td>Aniara</td>
			<td>A12-8480-10</td>
			<td>Use the volume ratio as citrate:blood; 1:9</td>
		</tr>
	</tbody>
</table>

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.

Successful application of the &#8220;orthotopic breast cancer model&#8221; is based on proper injection of cells into the mammary fat pad. Experimental errors such as imprecise inoculation of cells or leakage might lead to variations in tumor size or even the absence of a tumor which leads to the formation of a structure looking similar to a mammary fat pad injected with a control buffer (Figure 2A). The growth rate of the tumor is dependent on the nature of the injected cell line and in general, can be ...

Watch this Scientific Journal Video about Orthotopic Injection of Breast Cancer Cells into the Mammary Fat Pad of Mice to Study Tumor Growth. at JoVE.com

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

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 ...

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Research

JoVE Journal

Medicine

78.7K Görüntüleme.  Leiden University Medical Center.  Kanser tümörü çevreleyen dokunun hem de yerel pro- ve anti-inflamatuar aracılar tarafından etkilenir kompleks bir hastalıktır. Bu nedenle, daha çok deri altı modellere göre ortotrop enjeksiyon modelleri, bir şekilde daha iyi taklit eden insan patoloji kanser ilerlemesinin incelemek için yararlı olabilir. 

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

Performing and Processing FNA of Anterior Fat Pad for Amyloid

Historically, heart, liver, and kidney biopsies were performed to demonstrate amyloid deposits in amyloidosis. Since the clinical presentation of this disease is so variable and non-specific, the associated risks of these biopsies are too great for the diagnostic yield. Other sites that have a lower biopsy risk, such as skin or gingival, are also relatively invasive and expensive. In addition, these biopsies may not always have sufficient amyloid deposits to establish a diagnosis. Fat pad aspiration has demonstrated good clinical correlation with low cost and minimal morbidity. However, there are no standardized protocols for performing this procedure or processing the aspirated specimen, which leads to variable and nonreproducible results. The most frequently utilized modality for detecting amyloid in tissue is an apple-green birefringence on Congo red stained sections using a polarizing microscope. This technique requires cell block preparation of aspirated material. Unfortunately, patients presenting in early stage of amyloidosis have minimal amounts of amyloid which greatly reduces the sensitivity of Congo red stained cell block sections of fat pad aspirates. Therefore, ultrastructural evaluation of fat pad aspirates by electron microscopy should be utilized, given its increased sensitivity for amyloid detection. This article demonstrates a simple and reproducible procedure for performing anterior fat pad aspiration for the detection of amyloid utilizing both Congo red staining of cell block sections and electron microscopy for ultrastructural identification.

Fat pad aspiration is a preferred, minimally invasive, and low cost approach as compared to other methods to detect amyloid for diagnosis of systemic amyloidosis. This video article demonstrates a procedural outline for performing fat pad aspiration with appropriate processing of the specimen for the optimal diagnostic outcome.

Historically, heart, liver, and kidney biopsies were performed to demonstrate amyloid deposits in amyloidosis.  Since the clinical presentation of this ...

An In Vitro System to Study Tumor Dormancy and the Switch to Metastatic Growth

Recurrence of breast cancer often follows a long latent period in which there are no signs of cancer, and metastases may not become clinically apparent until many years after removal of the primary tumor and adjuvant therapy. A likely explanation of this phenomenon is that tumor cells have seeded metastatic sites, are resistant to conventional therapies, and remain dormant for long periods of time 1-4.
The existence of dormant cancer cells at secondary sites has been described previously as quiescent solitary cells that neither proliferate nor undergo apoptosis 5-7. Moreover, these solitary cells has been shown to disseminate from the primary tumor at an early stage of disease progression 8-10 and reside growth-arrested in the patients' bone marrow, blood and lymph nodes 1,4,11. Therefore, understanding mechanisms that regulate dormancy or the switch to a proliferative state is critical for discovering novel targets and interventions to prevent disease recurrence. However, unraveling the mechanisms regulating the switch from tumor dormancy to metastatic growth has been hampered by the lack of available model systems.
in vivo and ex vivo model systems to study metastatic progression of tumor cells have been described previously 1,12-14. However these model systems have not provided in real time and in a high throughput manner mechanistic insights into what triggers the emergence of solitary dormant tumor cells to proliferate as metastatic disease. We have recently developed a 3D in vitro system to model the in vivo growth characteristics of cells that exhibit either dormant (D2.OR, MCF7, K7M2-AS.46) or proliferative (D2A1, MDA-MB-231, K7M2) metastatic behavior in vivo . We demonstrated that tumor cells that exhibit dormancy in vivo at a metastatic site remain quiescent when cultured in a 3-dimension (3D) basement membrane extract (BME), whereas cells highly metastatic in vivo readily proliferate in 3D culture after variable, but relatively short periods of quiescence. Importantly by utilizing the 3D in vitro model system we demonstrated for the first time that the ECM composition plays an important role in regulating whether dormant tumor cells will switch to a proliferative state and have confirmed this in in vivo studies15-17. Hence, the model system described in this report provides an in vitro method to model tumor dormancy and study the transition to proliferative growth induced by the microenvironment.

An In Vitro System to Study Tumor Dormancy and the Switch to Metastatic Growth

A modified 3-D in vitro system is presented in which growth characteristics of several tumor cell lines in reconstituted basement membrane correlate with the dormant or proliferative behavior of the tumor cells at a metastatic secondary site in vivo.

Recurrence of breast cancer often follows a long latent period in which there are no signs of cancer, and metastases may not become clinically apparent ...

An Orthotopic Bladder Tumor Model and the Evaluation of Intravesical saRNA Treatment

We present a novel method for treating bladder cancer with intravesically delivered small activating RNA (saRNA) in an orthotopic xenograft mouse bladder tumor model. The mouse model is established by urethral catheterization under inhaled general anesthetic. Chemical burn is then introduced to the bladder mucosa using intravesical silver nitrate solution to disrupt the bladder glycosaminoglycan layer and allows cells to attach. Following several washes with sterile water, human bladder cancer KU-7-luc2-GFP cells are instilled through the catheter into the bladder to dwell for 2 hours. Subsequent growth of bladder tumors is confirmed and monitored by in vivo bladder ultrasound and bioluminescent imaging. The tumors are then treated intravesically with saRNA formulated in lipid nanoparticles (LNPs). Tumor growth is monitored with ultrasound and bioluminescence. All steps of this procedure are demonstrated in the accompanying video.

Establishing an orthotopic bladder tumor model to evaluate antitumor effects of intravesically delivered saRNA and monitoring tumor growth by ultrasound and bioluminescent imaging.

We present a novel method for treating bladder cancer with intravesically delivered small activating RNA (saRNA) in an orthotopic xenograft mouse bladder ...

Human Neuroendocrine Tumor Cell Lines as a Three-Dimensional Model for the Study of Human Neuroendocrine Tumor Therapy

Neuroendocrine tumors (NETs) are rare tumors, with an incidence of two per 100,&#x200A;000 individuals per year, and they account for 0.5% of all human malignancies.1 Other than surgery for the minority of patients who present with localized disease, there is little or no survival benefit of systemic therapy. Therefore, there is a great need to better understand the biology of NETs, and in particular define new therapeutic targets for patients with nonresectable or metastatic neuroendocrine tumors. 3D cell culture is becoming a popular method for drug screening due to its relevance in modeling the in vivo tumor tissue organization and microenvironment.2,3 The 3D multicellular spheroids could provide valuable information in a more timely and less expensive manner than directly proceeding from 2D cell culture experiments to animal (murine) models.
To facilitate the discovery of new therapeutics for NET patients, we have developed an in vitro 3D multicellular spheroids model using the human NET cell lines. The NET cells are plated in a non-adhesive agarose-coated 24-well plate and incubated under physiological conditions (5% CO2, 37 &deg;C) with a very slow agitation for 16-24 hr after plating. The cells form multicellular spheroids starting on the 3rd or 4th day. The spheroids become more spherical by the 6th day, at which point the drug treatments are initiated. The efficacy of the drug treatments on the NET spheroids is monitored based on the morphology, shape and size of the spheroids with a phase-contrast light microscope. The size of the spheroids is estimated automatically using a custom-developed MATLAB program based on an active contour algorithm. Further, we demonstrate a simple method to process the HistoGel embedding on these 3D spheroids, allowing the use of standard histological and immunohistochemical techniques. 
This is the first report on generating 3D spheroids using NET cell lines to examine the effect of therapeutic drugs. We have also performed histology on these 3D spheroids, and displayed an example of a single drug's effect on growth and proliferation of the NET spheroids. Our results support that the NET spheroids are valuable for further studies of NET biology and drug development.

We present a simple agarose overlay platform to grow 3D multicellular spheroids using neuroendocrine cancer cell lines. This method provides a very convenient way to examine the effect of therapeutic drugs on the neuroendocrine tumor cells. It could also help us establish human neuroendocrine tumor spheroids for cancer therapy.

Neuroendocrine tumors (NETs) are rare tumors, with an incidence of two per 100,&#x200A;000 individuals per year, and they account for 0.5% of all human ...

Orthotopic Aortic Transplantation in Mice for the Study of Vascular Disease

Vascular procedures involving anastomoses in the mouse are generally thought to be difficult and highly dependent on the skill of the individual surgeon. This is largely true, but there are a number of important principles that can reduce the difficulty of these procedures and enhance reproducibility. Orthotopic aortic transplantation is an excellent procedure in which to learn these principles because it involves only two end-to-end anastomoses, but requires good suturing technique and handling of the vessels for consistent success. This procedure begins with the procurement of a length of abdominal aorta from a donor animal, followed by division of the native aorta in the recipient. The procured aorta is then placed between the divided ends of the recipient aorta and sutured into place using end-to-end anastomoses. To accomplish this objective successfully requires a high degree of concentration, good tools, a steady hand, and an appreciation of how easily the vasculature of a mouse can be damaged, resulting in thrombosis. Learning these important principles is what occupies most of the beginner's time when learning microsurgery in small rodents. Throughout this protocol, we refer to these important points. This model can be used to study vascular disease in a variety of different experimental systems1-8. In the context shown here, it is most often used for the study of post-transplant vascular disease, a common long-term complication of solid organ transplantation in which intimal hyperplasia occurs within the allograft. The primary advantage of the model is that it facilitates quantitative morphometric analyses and the transplanted vessel lies contiguous to the endogenous vessel, which can serve as an additional control9. The technique shown here is most often used for mice weighing 18-25 grams. We have accumulated most of our experience using the C57BL/6J, BALB/cJ, and C3H/HeJ strains.

We describe a technique in which a section of the abdominal aorta from a mouse is transplanted orthotopically to just below the renal arteries in an allogeneic or syngeneic recipient. This technique can be useful in studies in which transplantation of large arteries of uniform size is deemed advantageous.

Vascular procedures involving anastomoses in the mouse are generally thought to be difficult and highly dependent on the skill of the individual surgeon. ...

Time-lapse Imaging of Primary Preneoplastic Mammary Epithelial Cells Derived from Genetically Engineered Mouse Models of Breast Cancer

Time-lapse imaging can be used to compare behavior of cultured primary preneoplastic mammary epithelial cells derived from different genetically engineered mouse models of breast cancer. For example, time between cell divisions (cell lifetimes), apoptotic cell numbers, evolution of morphological changes, and mechanism of colony formation can be quantified and compared in cells carrying specific genetic lesions. Primary mammary epithelial cell cultures are generated from mammary glands without palpable tumor. Glands are carefully resected with clear separation from adjacent muscle, lymph nodes are removed, and single-cell suspensions of enriched mammary epithelial cells are generated by mincing mammary tissue followed by enzymatic dissociation and filtration. Single-cell suspensions are plated and placed directly under a microscope within an incubator chamber for live-cell imaging. Sixteen 650 &mu;m x 700 &mu;m fields in a 4x4 configuration from each well of a 6-well plate are imaged every 15 min for 5 days. Time-lapse images are examined directly to measure cellular behaviors that can include mechanism and frequency of cell colony formation within the first 24 hr of plating the cells (aggregation versus cell proliferation), incidence of apoptosis, and phasing of morphological changes. Single-cell tracking is used to generate cell fate maps for measurement of individual cell lifetimes and investigation of cell division patterns. Quantitative data are statistically analyzed to assess for significant differences in behavior correlated with specific genetic lesions.

Time-lapse imaging is used to assess behavior of primary preneoplastic mammary epithelial cells derived from genetically engineered mouse models of breast cancer risk to determine if there are correlations between specific behavioral parameters and distinct genetic lesions.

Time-lapse  imaging can be used to compare behavior of cultured primary preneoplastic  mammary epithelial cells derived from different genetically ...

A Novel High-resolution In vivo Imaging Technique to Study the Dynamic Response of Intracranial Structures to Tumor Growth and Therapeutics

We have successfully integrated previously established Intracranial window (ICW) technology 1-4 with intravital 2-photon confocal microscopy to develop a novel platform that allows for direct long-term visualization of tissue structure changes intracranially. Imaging at a single cell resolution in a real-time fashion provides supplementary dynamic information beyond that provided by standard end-point histological analysis, which looks solely at 'snap-shot' cross sections of tissue.
Establishing this intravital imaging technique in fluorescent chimeric mice, we are able to image four fluorescent channels simultaneously. By incorporating fluorescently labeled cells, such as GFP+ bone marrow, it is possible to track the fate of these cells studying their long-term migration, integration and differentiation within tissue. Further integration of a secondary reporter cell, such as an mCherry glioma tumor line, allows for characterization of cell:cell interactions. Structural changes in the tissue microenvironment can be highlighted through the addition of intra-vital dyes and antibodies, for example CD31 tagged antibodies and Dextran molecules.
Moreover, we describe the combination of our ICW imaging model with a small animal micro-irradiator that provides stereotactic irradiation, creating a platform through which the dynamic tissue changes that occur following the administration of ionizing irradiation can be assessed.
Current limitations of our model include penetrance of the microscope, which is limited to a depth of up to 900 &mu;m from the sub cortical surface, limiting imaging to the dorsal axis of the brain. The presence of the skull bone makes the ICW a more challenging technical procedure, compared to the more established and utilized chamber models currently used to study mammary tissue and fat pads 5-7. In addition, the ICW provides many challenges when optimizing the imaging.

A Novel High-resolution In vivo Imaging Technique to Study the Dynamic Response of Intracranial Structures to Tumor Growth and Therapeutics

We describe a novel in vivo imaging technique that couples fluorescent chimeric mice with intracranial windows and high-resolution 2-photon microscopy. This imaging platform aids studies of dynamic changes in brain tissue and microvasculature, at a single-cell level, following pathological insults and is adaptable to assess intracranial drug delivery and distribution.

We have successfully integrated previously established Intracranial window (ICW) technology 1-4 with intravital 2-photon confocal microscopy to develop a ...

Three Dimensional Cultures: A Tool To Study Normal Acinar Architecture vs. Malignant Transformation Of Breast Cells

Invasive breast carcinomas are a group of malignant epithelial tumors characterized by the invasion of adjacent tissues and propensity to metastasize. The interplay of signals between cancer cells and their microenvironment exerts a powerful influence on breast cancer growth and biological behavior1. However, most of these signals from the extracellular matrix are lost or their relevance is understudied when cells are grown in two dimensional culture (2D) as a monolayer. In recent years, three dimensional (3D) culture on a reconstituted basement membrane has emerged as a method of choice to recapitulate the tissue architecture of benign and malignant breast cells. Cells grown in 3D retain the important cues from the extracellular matrix and provide a physiologically relevant ex&#160;vivo system2,3. Of note, there is growing evidence suggesting that cells behave differently when grown in 3D as compared to 2D4. 3D culture can be effectively used as a means to differentiate the malignant phenotype from the benign breast phenotype and for underpinning the cellular and molecular signaling involved3. One of the distinguishing characteristics of benign epithelial cells is that they are polarized so that the apical cytoplasm is towards the lumen and the basal cytoplasm rests on the basement membrane. This apico-basal polarity is lost in invasive breast carcinomas, which are characterized by cellular disorganization and formation of anastomosing and branching tubules that haphazardly infiltrates the surrounding stroma. These histopathological differences between benign gland and invasive carcinoma can be reproduced in 3D6,7. Using the appropriate read-outs like the quantitation of single round acinar structures, or differential expression of validated molecular markers for cell proliferation, polarity and apoptosis in combination with other molecular and cell biology techniques, 3D culture can provide an important tool to better understand the cellular changes during malignant transformation and for delineating the responsible signaling.

Three dimensional culture of mammary epithelial cells on a reconstituted basement membrane is a useful method to recapitulate the in vivo architecture of the benign breast, and to differentiate the malignant phenotype from the benign breast phenotype. Importantly, this system can be applied to study invasive carcinomas in other tissues.

Invasive breast carcinomas are a group of malignant epithelial tumors characterized by the invasion of adjacent tissues and propensity to metastasize. The ...

Assessment of Viability of Human Fat Injection into Nude Mice with Micro-Computed Tomography

Lipotransfer is a vital tool in the surgeon&#8217;s armamentarium for the treatment of soft tissue deficits of throughout the body. Fat is the ideal soft tissue filler as it is readily available, easily obtained, inexpensive, and inherently biocompatible.1 However, despite its burgeoning popularity, fat grafting is hampered by unpredictable results and variable graft survival, with published retention rates ranging anywhere from 10-80%. 1-3
To facilitate investigations on fat grafting, we have therefore developed an animal model that allows for real-time analysis of injected fat volume retention. Briefly, a small cut is made in the scalp of a CD-1 nude mouse and 200-400 &#181;l&#160;of processed lipoaspirate is placed over the skull. The scalp is chosen as the recipient site because of its absence of native subcutaneous fat, and because of the excellent background contrast provided by the calvarium, which aids in the analysis process. Micro-computed tomography (micro-CT) is used to scan the graft at baseline and every two weeks thereafter. The CT images are reconstructed, and an imaging software is used to quantify graft volumes.
Traditionally, techniques to assess fat graft volume have necessitated euthanizing the study animal to provide just a single assessment of graft weight and volume by physical measurement ex vivo. Biochemical and histological comparisons have likewise required the study animal to be euthanized. This described imaging technique offers the advantage of visualizing and objectively quantifying volume at multiple time points after initial grafting without having to sacrifice the study animal. The technique is limited by the size of the graft able to be injected as larger grafts risk skin and fat necrosis. This method has utility for all studies evaluating fat graft viability and volume retention. It is particularly well-suited to providing a visual representation of fat grafts and following changes in volume over time.

Fat grafting is an essential technique for reconstructing soft tissue deficits. However, it remains an unpredictable procedure characterized by variable graft survival. Our goal was to devise a mouse model that utilizes a novel imaging method to compare volume retention between differing techniques of fat graft preparation and delivery.

Lipotransfer is a vital tool in the surgeon&#8217;s armamentarium for the treatment of soft tissue deficits of throughout the body. Fat is the ideal soft ...

An Ex vivo Model to Study Hormone Action in the Human Breast

The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro culture, primary mammary epithelial cells tend to lose hormone receptor expression. Widely used hormone receptor positive breast cancer cell lines are of limited relevance to the in vivo situation. Here, we describe an ex vivo model to study hormone action in the human breast. Fresh human breast tissue specimens from surgical discard material such as reduction mammoplasties or mammectomies are mechanically and enzymatically digested to obtain tissue fragments containing ducts and lobules and multiple stromal cell types. These tissue microstructures kept in basal medium without growth factors preserve their intercellular contacts, the tissue architecture, and remain hormone responsive for several days. They are readily processed for RNA and protein extraction, histological analysis or stored in freezing medium. Fluorescence activated cell sorting (FACS) can be used to enrich for specific cell populations. This protocol provides a straightforward, standard approach for translational studies with highly complex, varied human specimens.

An Ex vivo Model to Study Hormone Action in the Human Breast

We have developed a novel ex vivo model to study hormone action in the human breast. It is based on tissue microstructures isolated from surgical breast tissue specimens which preserve tissue architecture, intercellular interactions, and paracrine signaling.

The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro culture, primary mammary epithelial ...