Establishment, characterization and drug sensitivity testing in primary cultures of human thymoma and thymic carcinoma

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Abstract
Thymomas and thymic carcinomas are peculiar epithelial tumors of the anterior mediastinum. They may show aggressive clinical behavior and are a paradigm for the interaction between the tumor and the immune system. So far, adequate functional studies enabling a better understanding of this malignancy have not been performed, since human thymoma/thymic carcinoma cell lines have not been available. Here, the authors describe the establishment, characterization and functional analyses of epithelial cell lines from a Type B1‐thymoma and a poorly differentiated thymic carcinoma. By Fluorescence‐activated cell sorting (FACS) analyses, both cell lines were aneuploid. The aneuploid cell fraction of the thymic carcinoma cell line was characterized by a high proliferation index of 55.9%, in contrast to a lower proliferation rate of the aneuploid cell fraction of the thymoma (19.7%). Array‐based comparative genomic hybridization (aCGH) and conventional cytogenetic analysis of the thymoma revealed only minor imbalances whereas the thymic carcinoma was characterized by a complex karyotype in the hyperdiploid range that was readily defined with multicolor FISH (mFISH). Application of a selective COX‐2 inhibitor reduced cell viability in both cell lines in a dose‐dependent manner. In conclusion, these first cell lines of a thymoma and a CD5‐positive thymic carcinoma are useful tools for further in vitro studies of cellular, molecular and genetic aspects of the disease and for functional tests to evaluate new therapeutic targets.