Introduction: Mesenchymal stromal cells (MSC) are an integral cellular component of the tumor microenvironment.\nNevertheless, very little is known about MSC originating from human malignant tissue and modulation of these\ncells by tumor-derived factors. The aim of this study was to isolate and characterize MSC from head and neck\nsquamous cell carcinoma (HNSCC) and to investigate their interaction with tumor cells.\nMethods: MSC were isolated from tumor tissues of HNSCC patients during routine oncological surgery.\nImmunophenotyping, immunofluorescence and in vitro differentiation were performed to determine whether the isolated\ncells met the consensus criteria for MSC. The cytokine profile of tumor-derived MSC was determined by enzyme-linked\nimmunosorbent assay (ELISA). Activation of MSC by tumor-conditioned media was assessed by measuring cytokine release\nand expression of CD54. The impact of MSC on tumor growth in vivo was analyzed in a HNSCC xenograft model.\nResults: Cells isolated from HNSCC tissue met the consensus criteria for MSC. Tumor-derived MSC constitutively\nproduced high amounts of interleukin (IL)-6, IL-8 and stromal cell-derived factor (SDF)-1?. HNSCC-derived factors\nactivated MSC and enhanced secretion of IL-8 and expression of CD54. Furthermore, MSC provided stromal support\nfor human HNSCC cell lines in vivo and enhanced their growth in a murine xenograft model.\nConclusions: This is the first study to isolate and characterize MSC from malignant tissues of patients with HNSCC. We\nobserved cross-talk of stromal cells and tumor cells resulting in enhanced growth of HNSCC in vivo.
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