Detection of circulating lymphendothelial cells in patients with solid tumors

Abstract

20010 Background: Bone marrow derived endothelial progenitor cells (ECPs) contribute to neoangiogenesis in cancer patients. Elevated numbers of circulating endothelial cells and EPCs can be detected in the peripheral blood of tumor patients. Recently, proliferating lymphatic vessels have been described in human cancers such as melanoma and head and neck tumors. Therefore, we investigated whether circulating lymphatic endothelial cells can be detected in cancer patients. Methods: We developed a sensitive immunocytochemical approach using a monoclonal antibody against the lymphendothelial specific hyaluronic receptor LYVE. After enrichment by Ficoll density gradient centrifugation, 7 × 10(5) peripheral blood mononuclear cells (PBMNCs) from 23 patients with metastatic cancer (6 gastrointestinal, 4 lung, 3 thymus, 3 thyroid, 1 mamma, 1 pancreas, 2 renal, 1 adrenal, 2 urothelial cancer, 1 PNET, 1 NET) and healthy individuals (n = 7) were spun onto glass slides. Two million PBMNs from each patient were stained for LYVE using the APAP technique. Isotype antibodies were used as controls. Cytospins were analyzed with the automated cellular imaging system (ACIS; ChromaVision Medical Systems). The method was validated with spiked blood samples. Results: Circulating LYVE+ lymphatic endothelial cells could be detected in 4 of 7 healthy subjects (57%) and in 16 of 23 patients (69%) with metastatic cancer. The mean number of lymphendothelial cells was significantly higher in cancer patients (15 cells/1 × 10(6) PBMNCs [range 0–276] vs. 1.0 cells/1 × 10(6) PBMNCs [range 0–2]). As a control, circulating tumor cells were enumerated after staining with a cytokeratin antibody (A45-B/B3). Circulating tumor cells could not be detected in healthy controls but in 13 of 23 of cancer patients (mean 1.4 cells/1 × 10(6) PBMNCs range [0–9]). Conclusion: Circulating lymphendothelial cells can be detected in patients with metastatic cancer and healthy subjects. Tumor patients have higher levels of circulating lymphendothelial cells than normal controls. These cells may participate in the generation of lymphatic vessels within tumor manifestations. No significant financial relationships to disclose.