These studies were funded, in part, by grants from the Alternative Research and Development Foundation (107588), the National Institute of Health (1U54CA136465-04S1), and the California Breast Cancer Research Program (201B-0141). We thank Drs. Andrew Wilber and R. Scott McIvor for the generous donation of their <pkt2 lubig=""> transponson and pK/hUbiC-SB11 transposase plasmids. We gratefully acknowledge John Tamaresis, Ph.D. for advice on statistical methods, Timothy Brown for performing flow cytometry, Georgette Henrich for advice on migrations assays, and Nancy Bellagamba for facilitating the collection of THR specimens. </pkt2>

Femoral heads were collected from patients undergoing elective THR surgery in the Department of Orthopaedic Surgery at the Stanford University School of Medicine. All tissues were collected as de-identified specimens in accordance with regulations of the Stanford University Research Compliance Office.
&#8203;1. Selecting a Breast Cancer Cell Line(s)
<ol>
	<li>Obtain or transfect the desired breast cancer cell line(s) with a luciferase-GFP reporter construct. The following experiments were performed using the MDA...

No disclosures to report.

Mehra et al. have previously described the postmortem collection and analysis of bone specimens from metastatic prostate cancer patients harvested at the time of autopsy, revealing high quality tissues and validating the use of human bone samples to study the metastatic process47. Here we have described protocols for collecting, processing and using human bone tissue fragments obtained from discarded femoral heads following THR surgery in a short-term co-culture system to study breast cell migration, ...

The tumor microenvironment is widely recognized as a critical determinant of cancer cell behavior during breast cancer progression and metastatic spread1-3. The goal of the method presented here is to facilitate the study of breast cancer cells within the microenvironment of human bone tissue, the most frequent site of breast cancer metastasis4-6. Bone is comprised of mineralized and marrow compartments7-9, both of which harbor cells and secreted factors implicated in metastatic progression10,11. Although widely used in vivo mouse models facilitate systemic studies of the metastatic process12-15, cell interactions within the skeleton are not readily accessible for observation and direct perturbation. Model systems for studying and culturing mouse bone tissues and mouse marrow cells provide better access and have yielded many insights regarding crosstalk and mechanisms underlying breast cancer cell metastasis of the murine skeleton16-22. However, studies have suggested that there may be species-specific patterns of osteotropism for bone tissue23,24. These patterns could reflect inherent species-specific differences in bone tissue properties, differences resulting from altered bone marrow populations in immune-deficient mice11, and/or the relatively young age of mice used in experiments, all of which are likely determinants of the bone microenvironment.
In vitro approaches for studying breast cancer cells in human bone co-cultures have typically focused on specific bone cell types such as marrow-derived osteoblasts or stromal cells cultured as monolayers or within engineered 3-dimensional model systems25-35. Although 2-dimensional cell culture models have formed the mainstay of in vitro approaches for cancer research, it has long been recognized that cell behavior is fundamentally altered in monolayer culture systems18,36,37. This has led to the development of engineered microenvironments that mimic the complexity of 3-dimensional living tissues, including matrix- and scaffold-based models composed of natural materials such as collagen, or synthetic polymers seeded with specific cell types to create tissue-like microenvironments36-41. Engineered approaches have also included the use of bioreactor platforms to control and study the hormonal milieu of the microenvironment18,19,41-43. Although biomimetic models and bioreactors provide many elements of a complex tissue microenvironment in a controlled setting, and have been successfully applied to advance the study of breast cancer metastasis to bone18,19,35,42,43, engineered model systems do not generally incorporate the full spectrum of cell types and extracellular matrix components present within the native bone environment.
Until recently, breast cancer cells have not been studied within the native, intact, 3-dimensional microenvironment of human bone tissues. We recently reported the development of a co-culture model using human bone tissue fragments isolated from total hip replacement (THR) surgery specimens44. These specimens harbor both the mineralized and marrow compartments necessary to study mechanisms underlying micro-metastasis in short term culture. In previous work we established proof-of-principle for using bioluminescence imaging (BLI) to monitor the proliferation of luciferase-expressing breast cancer cells (MDA-MB-231-fLuc) co-cultured with bone fragments44. Here we present detailed experimental protocols for studying breast cell cancer proliferation, colonization, and migration within the context of the native microenvironment using human bone tissue explants.
First we present a protocol for co-culturing breast cancer cells adjacent to bone fragments to measure breast cell proliferation using BLI. In this section, breast cell suspensions are seeded as cell spots in 6-well plates adjacent to bone fragments, which are immobilized by pieces of bone wax. Control wells contain bone wax, but no bone fragment. Once cell spots attach, medium is added and the plate is cultured for 24 hr, after which bioluminescent signal intensity (associated with cell number) is measured with BLI. In the next step we present methods for co-culturing breast cancer cells seeded directly onto bone fragments to study colonization and proliferation. Here the breast cell suspensions are pipetted directly onto the bone tissue fragments, which are monitored in culture by BLI and fluorescence microscopy over time to track colonization and cell number. In this method, the marrow compartment can be flushed from the bone fragments at any time point for analysis of colonized breast cancer cells by flow cytometry, or marrow viability assays.
In addition, we describe two different approaches for measuring breast cancer cell migration. In the first method steps are outlined for measuring migration toward bone tissue culture supernatants. In this protocol the breast cancer cells are seeded onto the inner, upper surfaces of Transwell insert membranes with an 8 &#181;m pore size (as shown in Figure 1A). The inserts are then placed into a receiver plate with wells containing bone tissue supernatant or control medium. Over the course of a 20 hr incubation period, small numbers of breast cancer cells migrate through the insert membranes down into the lower tissue culture wells where they attach for detection by BLI. In the second migration method the breast cancer cells are seeded onto the lower, outer surfaces of Transwell insert membranes. Bone tissue fragments are placed into the insert cups and the breast cancer cells migrate up through the membranes to colonize the bone fragments (as shown in Figure 1B), which are then imaged using BLI.

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	<tbody>
		<tr>
			<td>DMEM (1X) + GlutaMAX-l</td>
			<td>Life Technologies</td>
			<td>10569-010</td>
			<td>Supplement all DMEM with 10% fetal bovine serum and 1% Pen/Strep</td>
		</tr>
		<tr>
			<td>McCoy&#39;s 5A Medium (1X)</td>
			<td>Life Technologies</td>
			<td>16600-082</td>
			<td>Supplement all McCoy&#39;s&#160; with 10% fetal bovine serum and 1% Pen/Strep</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Life Technologies</td>
			<td>16000-044</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillen Streptomycin</td>
			<td>Life Technologies</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Blastocidin (10 mgl/ml)</td>
			<td>InvivoGen&#160;</td>
			<td>ant-bl</td>
			<td>Supplement media used for transfected cell lines.</td>
		</tr>
		<tr>
			<td>Falcon&#174; Cell Culture Inserts for 24 Well Plate with Transparent PET Membrane (8.0 &#956;m pore size)</td>
			<td>Corning Incorporated</td>
			<td>353097</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon&#174; 24 Well TC-Treated Polystyrene Cell Culture Insert Companion Plate</td>
			<td>Corning Incorporated</td>
			<td>353504</td>
			<td></td>
		</tr>
		<tr>
			<td>LIVE/DEAD Viability/Cytotoxicity Kit *for mammalian cells*</td>
			<td>Invitrogen Detection Technologies</td>
			<td>L-3224</td>
			<td></td>
		</tr>
		<tr>
			<td>FluoroBrite DMEM</td>
			<td>Life Technologies</td>
			<td>A18967-01</td>
			<td></td>
		</tr>
		<tr>
			<td>D-luciferin firefly, potassium salt 5 grams (30 mg/mL)</td>
			<td>Life Technologies</td>
			<td>L-8220</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile Cell Strainer 70 &#956;m</td>
			<td>Fisher Scientific</td>
			<td>22363548</td>
			<td></td>
		</tr>
		<tr>
			<td>6 Well TC-Treated Cell Culture Cluster</td>
			<td>Corning Incorporated</td>
			<td>3516</td>
			<td></td>
		</tr>
		<tr>
			<td>12 Well TC-Treated Cell Culture Cluster</td>
			<td>Corning Incorporated</td>
			<td>3513</td>
			<td></td>
		</tr>
		<tr>
			<td>24 Well TC-Treated Cell Culture Cluster</td>
			<td>Corning Incorporated</td>
			<td>3526</td>
			<td></td>
		</tr>
		<tr>
			<td>Friedman-Pearson Rongeur</td>
			<td>Fine Science Tools</td>
			<td>16021-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Bone wax</td>
			<td>Surgical Specialties Corporation</td>
			<td>903</td>
			<td></td>
		</tr>
		<tr>
			<td>IVIS 50 Imaging Platform</td>
			<td>Caliper Life Sciences/PerkinElmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Living Image Software Program&#160;</td>
			<td>Caliper Life Sciences/PerkinElmer</td>
			<td>133026</td>
			<td></td>
		</tr>
		<tr>
			<td>EVOS FL Imaging System</td>
			<td>Life Technologies</td>
			<td>Version 4.2</td>
			<td></td>
		</tr>
		<tr>
			<td>OsteoSense 680 EX</td>
			<td>PerkinElmer</td>
			<td>NEV10020EX</td>
			<td></td>
		</tr>
		<tr>
			<td>MCF-7 breast cancer cells</td>
			<td>ATCC</td>
			<td>HTB-22</td>
			<td></td>
		</tr>
		<tr>
			<td>MDA-MB-231 breast cancer cells</td>
			<td>ATCC</td>
			<td>HTB-26</td>
			<td></td>
		</tr>
		<tr>
			<td>Monoclonal mouse anti-human cytokeratin antibody</td>
			<td>DAKO Cytomation</td>
			<td>Clone (AE1/AE3)</td>
			<td></td>
		</tr>
	</tbody>
</table>

methods for culturing human femur tissue explants to study breast cancer cell colonization of the metastatic niche

Bone is the most common site of breast cancer metastasis. Although it is widely accepted that the microenvironment influences cancer cell behavior, little is known about breast cancer cell properties and behaviors within the native microenvironment of human bone tissue.We have developed approaches to track, quantify and modulate human breast cancer cells within the microenvironment of cultured human bone tissue fragments isolated from discarded femoral heads following total hip replacement surgeries. Using breast cancer cells engineered for luciferase and enhanced green fluorescent protein (EGFP) expression, we are able to reproducibly quantitate migration and proliferation patterns using bioluminescence imaging (BLI), track cell interactions within the bone fragments using fluorescence microscopy, and evaluate breast cells after colonization with flow cytometry. The key advantages of this model include: 1) a native, architecturally intact tissue microenvironment that includes relevant human cell types, and 2) direct access to the microenvironment, which facilitates rapid quantitative and qualitative monitoring and perturbation of breast and bone cell properties, behaviors and interactions. A primary limitation, at present, is the finite viability of the tissue fragments, which confines the window of study to short-term culture. Applications of the model system include studying the basic biology of&#160;breast cancer and other bone-seeking malignancies within the metastatic niche, and developing therapeutic strategies to effectively target breast cancer cells in bone tissues.

Isolating Tissue Fragments from Femoral Heads
Femoral heads were collected from equal numbers of male and female patients (44-90 years of age) undergoing elective total hip replacement surgery in the Department of Orthopaedic Surgery at the Stanford University School of Medicine. Each discarded femoral head contains a small portion of the upper femur, which harbors trabecular bone tissue composed of mineralized spicules and marrow. This tissue is accessible through the surgically exposed cross...

Watch this Scientific Journal Video about Methods for Culturing Human Femur Tissue Explants to Study Breast Cancer Cell Colonization of the Metastatic Niche at JoVE.com

Methods for Culturing Human Femur Tissue Explants to Study Breast Cancer Cell Colonization of the Metastatic Niche

Protocols are described for studying breast cancer cell migration, proliferation and colonization in a human bone tissue explant model system.

Bone is the most common site of breast cancer metastasis. Although it is widely accepted that the microenvironment influences cancer cell behavior, little ...

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