ESTABLISHMENT AND CHARACTERIZATION OF A MALIGNANT EPITHELIOID HEMANGIOENDOTHELIOMA FROM MOUSE THYROID-TUMOR

A mouse epithelioid hemangioendothelioma (mEHE) cell line, passagable in vivo without TSH stimulation, was established from a thyroid tumor. Before establishment of the cell line, the primary thyroid tumor which was co-transplanted with a TSH-producing pituitary adenoma showed signs of hyperplasia and then transformed during several in vivo transplantable passages. The cell line which was established from an in vitro culture, was deficient in thyroid-specific differentiation function and had characteristics of endothelial cell origin such as vascular cavity formation and factor VIII expression. The cell growth of mEHE/CH1-5 cell lines was independent of TSH but was inhibited by c-AMP and vitamin D-3. c-Myc proto-oncogene expression was also suppressed by vitamin Dg treatment. Both serum depletion and heparin treatment induced morphological changes in mEHE/CH 5 from an epithelial cell-like to an endothelial cell-like shape. Immunohistochemical analysis showed that epithelial membrane antigen expression was decreased and factor VIII expression was increased in relation to the morphological changes. In a further in vivo transplantation experiment, the histology of the mEHE/CH5 cell tumor had an angiosarcoma-like structure. These results indicate that this cell line established from a thyroid tumor possesses both epithelial and endothelial characteristics. The mEHE/CH5 cells might provide a good model for analyzing thyroid tumorigenesis and allow functional characterization of endothelial cells.