Abstract 365: Circulating bone marrow-derived VEGFR-2+ progenitor cells in benign and malignant soft tissue tumors.

Abstract

Abstract Background : Circulating endothelial progenitor cells (cEPCs) as recruited to the angiogenic vascular system of malignant tumors have been evaluated as a biomarker of tumor remission or progression through therapy in lung and breast cancer. We were interested to analyze the presence of bone marrow derived (BMD) cEPCs in soft tissue malignancies and correlate the changes to treatment efficacy. Methods: 75 treatment-naïve patients have (41 sarcoma, 21 gastro-intestinal stromal tumors GIST, 12 desmoid) and 11 healthy controls have been enrolled to the study. 25 ml of blood samples were drawn prior to therapy and 4-6 weeks after treatment by 20G iv cannula, collected in tubes containing sodium citrate (0.105 M) and processed within 1 h. Peripheral blood mononuclear cells (PBMC) were isolated by Ficoll density gradient centrifugation and cEPCs were characterized by quadruple staining using antibodies against CD133+, CD34, CD45dim and vascular endothelial growth factor-receptor (VEGF-R)-2+. The expression of cell-surface antigens was determined by four-color immunofluorescence. The frequency of cEPCs in peripheral blood was determined by a 2-dimensional side-scatter/fluorescence dot-plot analysis after exclusion of annexin V-positive cells and appropriate to exclude apoptotic cells. EPC counts are expressed as a percentage of total PBMCs. Serum-concentrations of VEGF and Angiopoetin-2 were determined by ELISA in triplicate samples from 5 ml serum. Results:The percentage of hematopoietic stem cells (CD34+, CD133+) was significantly increased in sarcoma and desmoid patients (0.44 ± 0.1 %) compared to GIST and healthy controls (0.13 ± 0.04 %; p=0.001). The percentage of VEGFR-2+ cells correspond to cEPC in sarcoma of 0.179 ± 0.190 % vs. healthy controls of 0.025 ± 0.018 %. Values for desmoid patients were similar to sarcoma whereas GIST patients showed values comparable to healthy patients. We found significantly increased mean VEGF levels in both sarcoma and desmoids (359 ± 157 pg/ml) in comparison to healthy controls (27 ± 13 pg/ml; p = 0.001). Ang-2 levels before therapy were significantly lower in healthy controls and desmoids (1665 ± 445 pg/ml) compared to sarcoma and GIST (2929 ± 960 pg/ml, p = 0.033) patients. Patients without signs of tumor recurrence showed normal cEPC values at post-treatment controls, whereas patients with progressive disease had increasing cEPC levels. Conclusion: This study demonstrates an increased mobilization of cEPCs in sarcoma and (non-metatasizing) desmoids tumors compared to healthy individuals and patients with GIST. cEPCs recruited for vasculogenesis and paracrine effects play a different role in the various subtypes of human soft tissue tumors. Citation Format: Kai Nowak, Elena Joas, Grietje Beck, Neysan Rafat, Peter Hohenberger. Circulating bone marrow-derived VEGFR-2+ progenitor cells in benign and malignant soft tissue tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 365. doi:10.1158/1538-7445.AM2013-365