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

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.