We thank Nguyen H. Nguyen for her technical help and Audrey O&#8217;Neill for support with the Zeiss Cell Observer spinning-disk confocal microscope. This work was supported by a Department of Defense postdoctoral fellowship (W81XWH-11-01-0139) and the Weizmann Institute of Science-National Postdoctoral Award Program for Advancing Women in Science (to V.P.).

All procedures described must be performed in accordance with guidelines and regulations for the use of vertebrate animals, including prior approval by the local Institutional Animal Care and Use Committee (IACUC).
1. Generation of Lung Metastases for Ex vivo Live Imaging (Transgenic or Tail Vein Injection)
NOTE: Lung metastases can be generated by utilizing genetically engineered mouse models or by intravenous (i.v) injection of cancer cells.
<o...

<ol>
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The authors have no conflicts of interest to disclose. All animal experiments were conducted in accordance with IACUC approved protocols, UCSF.

This manuscript describes a detailed method for ex vivo live imaging of lung metastasis in mouse models of metastasis. This imaging protocol provides a direct visualization of the dynamic and spatial tumor cell-stroma interactions within the lung microenvironment. It is a relatively easy and fast method that allows reliable imaging of lung metastasis for at least 4 hr. Movies acquired from these experiments can be used to track dynamic processes as cell motility and cellular interactions.
<p class="jove_cont...

The deadliest aspect of cancer is metastasis, which accounts for more than 90% of cancer-related morbidity and mortality1. Metastasis is a multistep process and due to its complexity, the exact cellular and molecular mechanisms that govern metastatic dissemination and growth are still elusive. To metastasize, tumor cells in the primary tumor must detach from their neighboring cells and basement membrane, cross through the extracellular matrix, intravasate, travel via blood or lymphatic vessels, extravasate at the secondary site, and finally, survive and establish secondary tumors. In addition to the properties of the tumor cells, the contribution from the microenvironment, which includes the adjacent stroma along with the normal counterparts of the cancer cells, is crucial for the seeding and establishment of metastatic lesions2.
Traditional methods to study metastatic seeding and growth examine static states, as tissues are excised and sectioned for histology. These data only generate a snapshot of this highly dynamic process. Although some useful information can be gained from these studies, the complicated process by which tumor and stromal cells interact during metastatic formation cannot be adequately assessed by these methods. Furthermore, it is not possible to gain insights into tumor or stromal cell migration patterns, which are important in establishing a colony at the distant site. In order to effectively study the metastatic process, it is essential to visualize various interactions between cancer cells and their microenvironment in a continuous manner and at real time. 
The lung is a common site for metastases from solid tumors as breast, colorectal, pancreatic cancer, melanoma and sarcoma3. Intravital imaging was previously used to study cell-cell interaction in various primary tumor and metastatic models4,5. Methods of lung imaging in mice, including intravital imaging, lung section imaging, and an ex vivo pulmonary metastasis assay have been published6&#8211;9. Intravital imaging of mouse lungs utilizes a thoracic suction window to stabilize the lungs6. This method is used for time-lapse imaging of the lung microcirculation and alveolar spaces. The anatomical location of the lungs poses a challenge to intravital imaging. In order to access the lungs, the chest cavity must be opened which leads to loss of negative pressure and collapsed lungs. This method only allows the visualization of a small part of the lungs and is technically demanding; an unnecessary complication in studies that examine processes that are independent of blood flow. Moreover, this method also requires gating out movement caused by breathing. This is done either by collecting images between breaths or during post image acquisition analyses10. The alternative ex vivo lung section imaging provides stability and depth, and also prepares lung parenchyma for immunostaining7. However, the lengthy sectioning process leads to an extensive delay between the time of animal sacrifice and the start of the imaging session. Moreover, the process of sectioning a mouse lung causes considerable amount of cell death8, thus interfering with the quality and quantity of imaging samples and perhaps needlessly altering tumor-stroma interactions. In order to technically bridge between the methods of intravital imaging and lung section imaging, while exploiting the advantages of the two techniques, a relatively fast and easy method for ex vivo lung imaging was developed. This method was achieved by imaging of non-sectioned whole lung lobes. Using this method, the motility of cancer cells as well as interactions between cancer cells and stromal cells in their microenvironment can be visualized in real time for several hours.

<table>
	<tbody>
		<tr>
			<td>MMTV-PyMT/FVB mice</td>
			<td>Jackson Laboratory</td>
			<td>2374</td>
			<td>Female mice</td>
		</tr>
		<tr>
			<td>ACTB-ECFP/FVB mice</td>
			<td>UCSF Werb lab</td>
			<td></td>
			<td>Female mice</td>
		</tr>
		<tr>
			<td>c-fms-EGFP/FVB mice</td>
			<td>UCSF Werb lab</td>
			<td></td>
			<td>Female mice</td>
		</tr>
		<tr>
			<td>FVB mice</td>
			<td>Jackson Laboratory</td>
			<td>1800</td>
			<td>Female mice</td>
		</tr>
		<tr>
			<td>GFP+ VO-PyMT cells</td>
			<td>UCSF Werb lab</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>70,000 kDa Dextran, rhodamine-conjugated</td>
			<td>Invitrogen</td>
			<td>D1818</td>
			<td>Dilute to&#160; 4mg/ml in 1 x PBS and store at -20&#160; &#176;C. Use 0.4 mg per animal.&#160;</td>
		</tr>
		<tr>
			<td>10,000 kDa Dextran, Alexa Fluor 647 conjugated</td>
			<td>Invitrogen</td>
			<td>D22914</td>
			<td>Dilute to&#160; 4mg/ml in 1 x PBS and store at -20&#160; &#176;C. Use 0.4 mg per animal.&#160;</td>
		</tr>
		<tr>
			<td>Anti-mouse Gr-1 antibody Alexa Fluor 647</td>
			<td>UCSF Monoclonal antibody core</td>
			<td></td>
			<td>Stock 1mg/ml. Use 7 ug per animal.</td>
		</tr>
		<tr>
			<td>Anesthetic</td>
			<td></td>
			<td></td>
			<td>Anesthesia approved by IACUC, used for anesthesia and/or euthanesia</td>
		</tr>
		<tr>
			<td>1X PBS</td>
			<td>UCSF cell culture facility</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS, USP sterile&#160;</td>
			<td>Amresco INC</td>
			<td>K813-500ML</td>
			<td>Ultra pure grade for i.v. injection</td>
		</tr>
		<tr>
			<td>Styrofoam platform</td>
			<td></td>
			<td></td>
			<td>Will be used as dissection board</td>
		</tr>
		<tr>
			<td>Fine scissors sharp&#160;</td>
			<td>Fine Science Tools</td>
			<td>14060-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Roboz Surgical Store</td>
			<td>RS-5135</td>
			<td></td>
		</tr>
		<tr>
			<td>Hot bead sterilizer</td>
			<td>Fine Science Tools</td>
			<td>18000-45</td>
			<td>Turn ON 30min before use</td>
		</tr>
		<tr>
			<td>Air</td>
			<td>UCSF</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen</td>
			<td>UCSF</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon dioxide</td>
			<td>UCSF</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1 mL syringe without needle&#160;</td>
			<td>BD</td>
			<td>309659</td>
			<td></td>
		</tr>
		<tr>
			<td>27 G x 1/2 needle&#160;&#160;</td>
			<td>BD</td>
			<td>305109</td>
			<td>for i.v. injection</td>
		</tr>
		<tr>
			<td>20 G x 1 needle, short bevel&#160;&#160;</td>
			<td>BD</td>
			<td>305178</td>
			<td></td>
		</tr>
		<tr>
			<td>Low-melting-temperature agarose&#160;</td>
			<td>Lonza</td>
			<td>50111</td>
			<td>To make 10 ml of solution, weigh 0.2 g of agarose, add to 10 ml 1 x PBS, and heat to dissolve. Agarose will solidify at room temperature, so maintain in a 37 &#176;C water bath until used for inflation.</td>
		</tr>
		<tr>
			<td>RPMI-1640 medium without phenol red</td>
			<td>Life Technologies</td>
			<td>11835-030</td>
			<td></td>
		</tr>
		<tr>
			<td>24 well Imaging plate&#160;</td>
			<td>E&#38;K scientific</td>
			<td>EK-42892</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass cover slides, 15 mm&#160;</td>
			<td>Fisher Scientific</td>
			<td>22-031-144</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital CO2 and temperature controller</td>
			<td>Okolab</td>
			<td>DGTCO2BX</td>
			<td>http://www.oko-lab.com</td>
		</tr>
		<tr>
			<td>Climate chamber</td>
			<td>Okolab</td>
			<td></td>
			<td>http://www.oko-lab.com</td>
		</tr>
		<tr>
			<td>Cell Observer spinning disk confocal microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zen software</td>
			<td>Zeiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted microscope</td>
			<td>Carl Zeiss Inc</td>
			<td>Zeiss Axiovert 200M</td>
			<td></td>
		</tr>
		<tr>
			<td>ICCD camera</td>
			<td>Stanford Photonics</td>
			<td>XR-Mega-10EX S-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Spinning disk confocal scan-head</td>
			<td>Yokogawa Corporation</td>
			<td>CSU-10b</td>
			<td></td>
		</tr>
		<tr>
			<td>Imaris</td>
			<td>Bitplane</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>mManager</td>
			<td>Vale lab, UCSF</td>
			<td></td>
			<td>Open-source software</td>
		</tr>
	</tbody>
</table>

ex vivo live imaging of lung metastasis and their microenvironment

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular and molecular processes that govern metastatic dissemination and growth are still elusive. Live imaging allows visualization of the dynamic and spatial interactions of cells and their microenvironment. Solid tumors commonly metastasize to the lungs. However, the anatomical location of the lungs poses a challenge to intravital imaging. This protocol provides a relatively simple and quick method for ex vivo live imaging of the dynamic interactions between tumor cells and their surrounding stroma within lung metastasis. Using this method, the motility of cancer cells as well as interactions between cancer cells and stromal cells in their microenvironment can be visualized in real time for several hours. By using transgenic fluorescent reporter mice, a fluorescent cell line, injectable fluorescently labeled molecules and/or antibodies, multiple components of the lung microenvironment can be visualized, such as blood vessels and immune cells. To image the different cell types, a spinning disk confocal microscope that allows long-term continuous imaging with rapid, four-color image acquisition has been used. Time-lapse movies compiled from images collected over multiple positions and focal planes show interactions between live metastatic and immune cells for at least 4 hr. This technique can be further used to test chemotherapy or targeted therapy. Moreover, this method could be adapted for the study of other lung-related pathologies that may affect the lung microenvironment.

Using spinning-disk confocal microscopy, various mouse model systems and injectables, the metastatic microenvironment can be visualized and tracked over time. Using an MMTV-PyMT; ACTB-ECFP; c-fms-EGFP triple transgenic mouse model, different cellular components are fluorescently labeled (Figure 2A, Movie 1). The typical structure of the lung parenchyma can be visualized in the CFP channel since all cells express ECFP under the &#946;-actin promoter. Larger/multicellular lung met...

Watch this Scientific Journal Video about Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment at JoVE.com

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

We describe a relatively simple method for ex vivo live imaging of the tumor cell-stroma interactions within lung metastasis, utilizing fluorescent reporters in mice. Using spinning-disk confocal microscopy, this technique enables visualization of live cells for at least 4 hr and could be adapted to study other inflammatory lung conditions.

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular ...

The overall goal of this procedure is to visualize dynamic tumor cell stroma interactions within lung metastases.This method can help answer key questions in the cancer metastasis field, such as how are metastasis established.and what cell types within the micro-environment are involved in this process?The main advantage that this technique offers is that this is a fast and easy method for ex vivo lung imaging that enables visualization of live cells for at least four hours.This technique may have furthered our understanding of mechanisms of action of various targeted therapeutics for treatment of lung metastasis.We first had an idea for this method when we were examining metastasis by lung section imaging and were struggling with extensive cell death as a result of this procedure.To prepare the lungs for ex vivo live imaging, begin by immobilizing the mouse on a polystyrene foam lid covered with a piece of soaker and sterilize the animal with 70%ethanol.Next, using surgical scissors make a transverse epigastric incision through the skin, followed by a similar incision through the peritoneum.Then, moving the dissection board into a vertical position, cut the descending aorta, so that the blood pools into the abdomen and not into the chest cavity.Snip the small opening in the diaphragm to release the vacuum.Then, cut along the rib cage to excise the diaphragm and to visualize the lungs.Using surgical scissors, cut the skin up to the trachea over the rib cage leaving the ribs intact.Then, separate the skin from the rib cage, and remove the surrounding connective tissue to expose the trachea, taking care not to damage the trachea itself.Snip a small opening approximately one millimeter in diameter in the exposed trachea, parallel to the cartilaginous rings as close to the larynx as possible without cutting completely through the trachea.Then, gently insert a 20 gauge needle four to five millimeters into the trachea without any counter-force.The end of the needle should be visible through the trachea.Fill a syringe with 400 microliters of 37 degrees Celsius 2%low melting temperature agarose, and then stabilize the needle with forceps.Keeping the dissection board vertical, slowly instill the entire quantity of warm agarose through the needle into the lungs.Once the lungs are inflated, detach the syringe while keeping the needle inside the trachea and pour approximately 50 milliliters of 20 degrees Celsius PBS over the lungs to help set the agarose.When the agarose has solidified, remove the needle and use forceps to close the trachea to prevent the leakage of any non-solidified agarose.Now, open the chest further by sternotomy and grasp the trachea with forceps.Then, using a pair of surgical scissors, cut through the trachea completely.To remove the lungs, gently pull the trachea up, cut away the connective tissue and esophagus, and pull the lungs completely out of the chest cavity.Immerse the tissue in 37 degrees Celsius RPMI 1640 to wash off the excessive blood.Using scissors and forceps, cut the lobes

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12.2K vistas.  University of California. The overall goal of this procedure is to visualize dynamic tumor cell stroma interactions within lung metastases.This method can help answer key questions in the cancer metastasis field, such as how are metastasis established.and what cell types within the micro-environment are involved in this process?The main advantage that this technique offers is that this is a fast and easy method for ex vivo lung imaging that enables visualization of live cells for at least four hours.This technique may...