Abstract 3231: An orthotopic xenograft model of sarcoma metastasis demonstrates essential role of tumor microenvironment for metastasis

Abstract

Abstract Sarcoma metastasis is a multi-step process that includes migration, intravasation into the circulation, extravasation and invasion to distant tissue, and distant tumor growth, and because commonly used xenograft models do not account for every step in the process, we sought to develop a novel metastasis model system. Our technique involves implanting small fragments of patient-derived xenografts into either the tibia or gastrocnemius muscle of NOD/SCID/IL-2Rγ knock-out mice and amputating the affected limb when the tumor reaches at least 1 cm in diameter. Mice are then followed for the development of distant metastases. We found that Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma xenografts all undergo distant metastasis when implanted in an orthotopic location, but do not metastasize after subcutaneous implantation, even when the subcutaneous tumor is excised and mice are observed long-term post-excision. We also investigated whether the difference in metastatic potential is related to cell intrinsic or cell extrinsic factors. Analysis by immunofluorescence revealed that tumors are infiltrated by macrophages regardless of site of implantation, but that the polarization of these macrophages differs. We also found differences in expression of arginase and NOS2 based on site of xenograft implantation. Thus, we have demonstrated that sarcoma patient-derived xenografts undergo spontaneous distant metastasis when implanted in an orthotopic location, but not when implanted in a heterotopic location, highlighting the essential role of the tumor microenvironment in determining metastatic potential. This model has significant benefits compared with the more commonly used tail vein injection model of metastasis, which bypasses the requirements for local invasion and vascular intravasation, processes that are amenable to study using our model. We have begun to use this model to investigate the mechanisms by which tumor microenvironment influences metastasis, and also are using this model for preclinical drug evaluation to determine a therapy's effect not only on growth of the primary tumor, but also on development of metastasis. Citation Format: Seth D. Goldstein, Masanori Hayashi, Catherine M. Albert, Kyle W. Jackson, David M. Loeb. An orthotopic xenograft model of sarcoma metastasis demonstrates essential role of tumor microenvironment for metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3231. doi:10.1158/1538-7445.AM2015-3231