Abstract 3297: CD90/Thy-1-positive cells in the peripheral blood of tumor patients co-express CD44

Abstract

Abstract Aims: Interactions between epithelial tumor cells and the surrounding milieu are an essential regulatory component of tumor development. Especially the contribution of the crosstalk between epithelial tumor cells and tumor-associated fibroblasts (TAFs) on tumor progression and metastasis formation is of emerging interest. Therefore, we ask whether circulating TAFs could be detected in the peripheral blood of tumor patients and how they could be further characterized. Methods: CD90/Thy-1 is a putative marker of TAFs. A fluorescence-scanning-cytometer (scanR) was used to detect and quantify vital CD90-positive cells in blood samples from individual tumor patients (e.g. breast, bladder, kidney). For further analysis CD90-positive cells were separated from leukocyte fractions pooled from different tumor patients using an immunomagnetic cell separation technology (ROBOSEP®). The CD90-positive fraction was subsequently analyzed by immunofluorescence and immunohistochemistry. We focused on the expression of other stroma markers like FAP-alpha and cell surface proteins like CD44 which are involved in metastasis formation. Results: In cell culture experiments we established CD90 as a highly specific marker for fibroblasts. The amount of CD90 positive cells in whole blood samples varied from 0 up to 54,000 cells/ml and changed over time. The CD90-positive cells were enriched immunomagnetically from the leukocyte fraction pooled from tumor patients. By immunofluorescence we approved the cell vitality and verified that the separated cells do not belong to the sub-population of CD34-positive blood stem cells. Blood samples from more than 300 patients with solid tumors were tested for the presence of CD90-positive cells. Immunofluorescence double staining of the separated cells showed the co-expression of CD90 and CD44, which participates in a wide variety of cellular functions like hematopoiesis and tumor metastasis formation. Further immunohistochemical analysis demonstrated the expression of CD29 which is involved in metastasis formation and CD105 a marker for activated fibroblasts in a subset of the CD90-positive cell fraction. Conclusions: We could show that CD90-positive cells circulate in the peripheral blood of tumor patients. The additional expression of other stroma and tumor associated proteins on the cells could argue for their involvement in aspects of tumor progression. Ongoing studies should evaluate their suitability as prognostic factor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3297.