Oncologic Trogocytosis Figure 2. Electronic microscopy analysis of ovarian cancer aggregates and primocultures of Hospicells and OVCAR3. A. Electronic microscopy sections showing EOC cell and Hospicells aggregates displaying numerous interactions between cancer cells (thin arrow) and Hospicells (thick arrow and (*)). B, C and D. Details of different interactions: through thin pseudopods (B and C), or through large membranous contact (D). Hospicells are marked with an (*) sign. E. Co-cultures of freshly isolated Hospicells (*) and OVCAR3 displaying the network of Hospicells’ pseudopods enhancing contact with EOC cells. F. Cell membrane fusion (arrows) between Hospicells (*) and cancer cells pseudopods in co-cultures. doi:10.1371/journal.pone.0003894.g002 Table 1. Demographic characteristics of the initial patients included in the study. Patients Age Histologic Type Grade FIGO stage 1 2 3 4 5 58 62 67 59 61 Serous adenocarcinoma Serous adenocarcinoma Serous adenocarcinoma Papillary adenocarcinoma Papillary adenocarcinoma 3 3 2 3 2 IIIc IIIc IIIc IV IIIc doi:10.1371/journal.pone.0003894.t001 pseudopods (Figure 2B), by membrane contact over a large surface area (Figure 2C), and through tight junctions such as desmosomes (Figure 2D). When cultured with EOC cells, Hospicells’ cytoplasm rapidly expanded into several short pseudopods (Figure 2E), producing small membrane fusion domains in the contact zones (Figure 2F). Phenotypic Characterization of the Hospicells According to immunochemistry studies (detailed in Table 2), these original cells isolated for their specific adhesion to ovarian cancer cells among the aggregates, did not express lineage-specific cell surface markers such as cytokeratin and EMA (specific for epithelial cell lines), vimentin (specific for mesenchymal cell lines), CD45 (specific for lymphoid tissue), CD20 (specific for B lymphocytes), CD3 (specific for T lymphocytes), CD68 (specific for macrophages and histiocytes), CD34 (specific for stem cells), S100 protein (specific for melanocytes), and myeloperoxidase (specific for granulocytic lineage). Specific adhesion of the Hospicells The isolation of the Hospicells among the EOCA raised the question about the specificity of the interaction between these cells and ovarian cancer cells. Unlike cell-lines such as human bone marrow endothelial cells (HBMEC) or fibroblasts, OVCAR3 cells adhered strongly and specifically to freshly isolated Hospicells (Figure 3A). It is noteworthy that OVCAR3 cells did not display a significative adhesion profile to other OVCAR3 cells, increasing the significance of Hospicells’ presence among the ECOA. Table 2. Molecular characterization of Hospicells. Hospicells’ reactivity Antigen specificity Epithelial Hematopoietic Mesenchymal Endothelial, lymphatic Neuro-epithelial Myo-epithelial Ubiquitous Embryonic Stem-cells doi:10.1371/journal.pone.0003894.t002 PLoS ONE | www.plosone.org 3 December 2008 | Volume 3 | Issue 12 | e3894 Negative EMA, KL1, AE1, AE3, alpha-Smooth actin CD44, CD47 SSEA-1, SSEA-4 CK5, CK6, CK7, CK8, CK18, CK19, CK20, E-cadherin, EGFR CD45, CD3, CD4, CD11a, CD15, CD16, CD19, CD23, CD26, CD34, CD68, CD41, LC, DBB42, CD10, MHC1 DBA44, CD15, CD30, CD49d, VLA4, CD51, CD56, CD66, CD69, CD126, CD133 CD133, CD99, vimentine, CALB2, HBME1 (mesothelial cell surface protein) D2-40, CD31, CD71, CD106 NSE, Chromogranin, CD57, synaptophysin (p38), S100 Positive CD9, CD29 CD166 CD146