The Reaction of Bone to Tumor Growth From Human Breast Cancer Cells in a Rat Spine Single Metastasis Model

In Brief Study Design. In vivo experiments to develop a rat spine single metastasis model by using human breast cancer cells. Objective. To study the survival and tumorigenesis of the human breast cancer cells after transplantation to vertebral body (VB) by intraosseous injection as a model for therapeutic studies of spine metastatic tumor. Summary of Background Data. VBs are the most common bones involved in the metastases of breast cancer. To develop experimental therapeutics requires an appropriate animal model. Moreover, it is also important to establish accurate and sensitive detection methods for the evaluation. Methods. MDA-MB-231 human breast cancer cells were injected into 3-week-old female athymic rats. The tumorigenesis was assayed with quantitative in vivo bioluminescence (IVIS), microcomputed tomography (micro-CT), quantitative CT (qCT), micro position emission tomography (micro-PET), and histologic studies. Results. A spine single metastasis model of human breast cancer was successfully developed in rats. The IVIS signal intensity from the cancer cells increased after 2 weeks. Signal from the tumor in spine can be detected by micro-PET at day 1. The signal intensity decreased after 1 week and then recovered and continually increased afterwards. Bone destruction was demonstrated in the qCT and micro-CT images. However, both qCT and micro-CT found that the bone density in the cancer cell-injected VB increased before the appearance of osteolysis. The growth of tumor and the reaction of bone in the VB were observed simultaneously by histology. Conclusion. A spine single metastasis model was developed by injection of human breast cancer cells into the VB of athymic rats. This is the first report of quantitative evaluation with micro-PET in a spine metastasis model. In addition, the detection of osteogenesis after the introduction of MDA-MB-231 cells in vivo is a novel observation. A spine single metastasis model was developed in athymic rats by intraosseous injection of human breast cancer cells (MDA-MB-231). The tumorigenesis was evaluated by IVIS, micro-position emission tomography, quantitative computed tomography, microcomputed tomography, and histology. For the first time, osteogenesis was found in the bone before osteolysis induced by the MDA-MB-231 cells.