Depletion of these cells from tumor bearing nude mice resulted in a decrease in tumor growth, reduced angiogenesis Pitavastatin nmr and an inhibiton of tumor invasion. In order to characterize the tumor-supporting capacities of inflammatory cells we analysed the contribution of neutrophils and macrophages to tumor invasion in vitro. We were able to demonstrate that both cell types strongly enhance

invasion of SCC tumor cells in the presence of exogenously added stimulating cytokines while they do not influence invasion without additional cytokine stimulation. This implies that inflammatory cells need stimulation by specific mediators to be activated towards a tumor supporting phenotype. In this context we are currently Ruboxistaurin order analysing selected stimulatory factors with respect to their influence on both neutrophils and macrophages and have selleck chemicals identified a novel factor that activates these two cell types. Poster No. 88 Ovarian Cancer Cells Acquire Chemoresistance through Intercellular Transfer of MSC-Derived PgP Raphaël Lis 1,2 , Pejman Mirshahi2, Rowaida Ziad Taha1, Mary Poupot3, Eliane Mery4, Jean Jacques Fournié3, Denis Querleu4, Massoud Mirshahi2, Arash Rafii1 1 Stem Cells Research, Weill Cornell Medical College – Qatar, Doha, Qatar, 2 Tumor cells resistance, Centre de Recherche de Cordeliers – INSERM U872, Paris,

France, 3 Oncology, Centre de Physiopathologie Toulouse Purpan – INSERM U563, Toulouse, France, 4 LFR 44, IFR 31, Institut Claudius Regaud, Toulouse, France Background: The microenvironment plays a

major role in the onset and progression of metastasis. Epithelial ovarian cancer (EOC) tends to metastasize to the peritoneal cavity where interactions within the microenvironment might lead to chemoresistance. Mesothelial cells and particularly Mesenchymal Stem Cells (MSC) are important actors of the peritoneal homeostasis; we determined their role in the acquisition of chemoresistance of ovarian tumours. Methodology/Principal Findings: We isolated MSC from ascitis of patients Exoribonuclease with ovarian carcinosis using limiting dilution. We studied their ability to confer chemoresistance through heterocellular interactions. These MSC derived from ascitis diplayed positive immunostaining for CD9, CD10, CD29, CD146, CD166 and Multi drug resistance protein, as described in the litterature. They preferentially interacted with epithelial ovarian cancer cells. This interaction induced chemoresistance to platin and taxans with the implication of multi-drug resistance proteins. This contact enabled EOC cells to capture patches of the MSC membrane through intercellular transfer of membrane and proteins (also referenced as trogocytosis), therefore acquiring their functional P-gp proteins and thus developing chemoresistance. Presence of MSC in ovarian cancer tissue micro-array from patients with neo-adjuvant chemotherapy was also significantly associated to chemoresistance.