Purpose Bone is a preferential site of breast cancer metastasis and models are needed to study this process at the level of the microenvironment. We have used bioluminescence imaging (BLI) and multiplex biomarker immunoassays to monitor dynamic breast cancer cell behaviors in co-culture with human bone tissue. Procedures Femur tissue fragments harvested from hip replacement surgeries were co-cultured with luciferase-positive MDA-MB-231-fLuc cells. BLI was performed to quantify breast cell division and track migration relative to bone tissue. Breast cell colonization of bone tissues was assessed with immunohistochemistry. Biomarkers in co-culture supernatants were profiled with MILLIPLEX® immunoassays. Results BLI demonstrated increased MDA-MB-231-fLuc proliferation (p<0.001) in the presence vs. absence of bones, and revealed breast cell migration toward bone. Immunohistochemistry illustrated MDA-MB-231-fLuc colonization of bone, and MILLIPLEX® profiles of culture supernatants suggested breast/bone crosstalk. Conclusions Breast cell behaviors that facilitate metastasis occur reproducibly in human bone tissue co-cultures and can be monitored and quantified using BLI and multiplex immunoassays.

Purpose: Bone is the most common site of breast cancer metastasis and model systems are needed to study aspects of this process directly at the microenvironmental level. Our goal was to establish optical imaging approaches to monitor and quantitate the dynamics of cell growth, migration and colonization in viable ex vivo co-cultures of breast cancer cells and bone tissue explants. Experimental Procedures: Femur tissues harvested from CD-1 nude mice and discarded femoral heads from human hip replacement surgeries were cultivated in 6-well tissue culture plates adjacent to 4T1 mouse mammary carcinoma or MDA-MB-231 human breast cancer cells harboring luciferase reporters. Serial bioluminescence imaging (BLI) was performed on an IVIS 50 Imaging System to quantify breast cancer cell growth, track breast cell migration toward bones, and monitor breast cell colonization of bone tissue over a period of days and weeks. Bioluminescence imaging of single breast cancer cells in these cultures was also performed over time using a prototype LV200 Bioluminescent Imaging System from Olympus. Summary of Results: BLI revealed the directed migration of breast cancer cells toward and into adjacent bone tissues within days, and documented extended colonization of bone tissues for up to several weeks. Quantitative BLI demonstrated variable growth rates for breast cancer cells grown in the presence vs. absence of bone tissues. Growth, migration and colonization varied dramatically and consistently according to the region of femur (epiphysis vs. diaphysis) used for co-culture. The variable patterns of breast cancer cell growth and migration observed in association with different anatomic regions of the femur are consistent with the presence of distinct cell populations within specific microenvironmental compartments of the bone. Migration of bone cells toward adjacent colonies of breast cancer cells was also observed. Conclusions: Cell behaviors associated with breast cancer metastasis occur reproducibly in viable, dynamic ex vivo co-cultures and can be monitored and quantified using optical imaging approaches. Because of the accelerated time course of interactions, and the immediate quantitation afforded by BLI, this model will facilitate the direct, rapid study of breast cancer cell interactions within the metastatic niche of bone tissues. This approach circumvents the prolonged time course associated with in vivo metastasis models and offers the potential for high throughput perturbation to identify and evaluate therapeutic interventions. Citation Format: Bonnie L. King, Marie Bammer, Irfan Ali-Khan, Jonathan W. Hardy, Christopher H. Contag. Optical imaging model for monitoring dynamic interactions of breast cancer cells and bone tissues in ex vivo co-cultures. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A48.