A TRANSFORMED MURINE MYOCARDIAL VASCULAR ENDOTHELIAL-CELL CLONE - CHARACTERIZATION OF CELLS IN-VITRO AND OF TUMORS DERIVED FROM THE CLONE IN-SITU

In the course of maintaining a cloned murine myocardium-derived endoth elial cell line (mouse heart endothelial cell clone 5; MHEC5) a sponta neously transformed variant has been identified (clone MHEC5-T). On in jection into histocompatible mice, clone MHEC5-T uniformly generated e pithelioid haemangioendotheliomas. Clone MHEC5-T underwent significant additional alterations in addition to the acquisition of tumour-formi ng potential ill vivo along with the diagnostic col-relate of loss of cellular contact inhibition in vitro, Whereas the transformed cells ma intained lectin-binding properties characteristic of endothelial cells , they lost the cell surface receptor(s) for acetylated low density li poprotein and no longer bound antibodies to either angiotensin convert ing enzyme or von Willebrand factor-associated antigen, Vascular cell adhesion molecule-1 (VCAM-1), expressed constitutively on the parent c lone, was clown regulated in the transformed cell line. The transforme d cells acquired immunoreactivity to antibodies directed against cytok eratin, and they showed a markedly increased response to migration-ind ucing factors in vitro. The cell line described in this report demonst rates that the in vitro transformation of myocardium-derived endotheli al cells can lead through transitional stages of differentiation to a new stable phenotype characterized by endothelial - to - epithelioid t ransition, The study of MHEC5-T cells, in addition to providing insigh t into the biology of cardiac neoplasms, may help to elucidate regulat ory mechanisms involved in endothelial cell activation, transition and transformation.