Abstract 1581: Determination of the cellular origin of stroma in osteosarcoma

Abstract

Abstract Introduction- Solid tumors like osteosarcoma have a distinct structure that is comprised of two interdependent compartments, the parenchyma (neoplastic cells) and the stroma that the neoplastic cells induce or produce and in which they are dispersed. The stroma may be induced as a result of tumor cell-host interactions or alternatively tumors may undergo different patterns of programmed differentiation to perform the necessary stromal support functions. Since stroma development is critical to the growth of tumor, identification of origin and mechanism of development of stroma can help target potential therapies against the tumor. Therefore we performed this study to elucidate the origin of stroma in a osteoarcoma xenograft, with a hypothesis that, the stroma of osteosarcoma is host (mouse) derived. Methods- (1) Frozen sections from xenograft osteosarcomas, were stained with vWF and CD31 (endothelial marker antigens) to identify the blood vessels. (2) The endothelial cells were laser capture dissected from frozen sections by pattern recognition. The Human and mice vWF and CD31 gene expression was quantified by real time PCR. (3) Detection of human and mice vWF gene by F.I.S.H. (4) Double immunofluorescent staining used to further delineate the mouse or human origin of the blood vessels. Anti Human Vimentin used to stain all human tissues, and anti vWF(Human and mice) to stain blood vessels of human and mice, fluorophore labeled secondary antibodies used to identify the bound primary antibodies. Results-The Immuno staining for vWF (reactive for both human and mice) and CD 31 (reactive only for human) revealed deficient staining for CD31, implying that the blood vessels were mostly murine. The gene expression assays on the microdissected samples for human and mouse VWF and CD 31, showed that there is expression of both human and murine vWF and CD31 in the xenografts, with more mouse genes than human in the microdissected blood vessels. The findings were confirmed by F.I.S.H for vWF probes for human and mice, whose initial results show that 95% of the tumors is human but at least 5% of the xenograft section stained for the mouse vWF probes. Double immunofluorescent studies are still in progress but preliminary results show, predominant human blood vessels with interspread murine blood vessels. Conclusions – Although confirmatory experiments are still in progress, initial suggestions in the context of human heterotopic osteosarcoma xenografts, show that most of blood vessels are murine derived. Further studies will be undertaken to determine whether the blood vessels in human osteosarcomas are tumor derived or a result of vascular in-growth as is the case in the murine system. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1581. doi:10.1158/1538-7445.AM2011-1581