Abstract B9: Mouse model of primary human renal cell carcinoma metastasis to bone

More than a third of patients with renal cell carcinoma (RCC) will die from disease and thus renal cell carcinoma has the highest mortality rate of the genitourinary cancers. Localized RCC can be cured by surgery but life expectancy is short for the metastatic disease. Thirty % of RCC metastasizes to bone and these metastases are especially debilitating and resistant to therapy. As the incidence of RCC is increasing, bone metastatic renal cancer merits greater focus. However, the development of effective therapies for RCC bone metastasis is hampered by lack of realistic pre-clinical models. Recent studies have shown that tumorgrafts are the most realistic models of solid tumors that are highly predictive of therapeutic response. We have improved this methodology by implanting precision-cut tumor tissue slices rather than minced tissue chunks into immunodeficient mice. Our aim is to develop a bone metastasis model using tissue slice tumorgrafts (TSGs) derived from fresh RCC specimens rather than established RCC cell lines that do not mimic natural history of metastases. Methods: Cores (8-mm diameter) of fresh renal cancer were obtained from nephrectomy specimens and precision-cut at 300-μm using a tissue slicer. Intact tissue slices were then implanted under the renal capsules of immunodeficient mice. The presence of disseminated cells in the bone marrow of graft-bearing mice was screened by qPCR (polymerase chain reaction) for human-specific markers. Primary cells were then obtained by enzymatical digestion of TSGs and injected into the tibiae of mice to mimic a RCC bone metastasis. Mice were followed up with x-ray and micro-CT. At the end of the experiment the mice bearing intratibial tumors were sacrificed and the tibiae were fixed and longitudinally sectioned at 5-μm. The phenotype of the metastases and interactions of cancer cells with the bone marrow cells/stem cell niche was analyzed by means of immunohistology. Results: By using human specific qPCR, we detected disseminated tumor cells in bone of mice bearing TSGs derived from a clear cell carcinoma patient, who subsequently progressed to metastatic disease, 1 month after implantation. The analysis for 9 other RCC cases is currently under way. We then confirmed the presence of metastatic lesions in bone by histology. These metastases retained many phenotypic characteristics of the primary tumor (as shown by histology and immunohistochemistry for CA-IX or CD-31). Primary cells derived from the TSGs produced x-ray visible tumors/metastases already at 3 weeks after cancer cell inoculation intratibially at a 100 % engraftment rate. Micro-CT analysis revealed an osteolytic nature of these lesions, which is considered typical for renal cancer bone metastases. Conclusions: We showed that orthotopic RCC TSGs have potential to develop micrometastases and metastases to bone. We demonstrated the feasibility of an intratibial model of RCC metastasis to bone that resembles the actual disease in many ways. These are the first reported models of primary RCC metastasis to bone. Our translational research project allows realistic settings to test therapeutics to prevent or treat micro-metastases and metastases in RCC and has potential for applications in personalized medicine Citation Format: Maija Valta, Hongjuan Zhao, Alexandre Ingels, Alan Thong, Rosalie Nolley, Matthias Saar, Donna Peehl. Mouse model of primary human renal cell carcinoma metastasis to bone. [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 B9.