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Characterization of tissue factor expression on the human endothelial cell line ECV304

The endothelial cell line ECV304 is a spontaneously transformed cell line established from human umbilical vein. The characterization of tissue factor (TF) expression by ECV304 cells has been accomplished in this study. ECV304 cells expressed both TF mRNA and antigen (TFag) constitutively. In ECV304 cell lysates, the levels of TFag (1.4 ± 0.3 ng of TFag/106 cells) were considerably higher than in THP‐1 monocytoid cells (0.07 ± 0.03 ng of TFag/106 cells). TFag was also detected on the ECV304 cell surface by flow cytometric studies. In binding analyses, 3.5 ± 0.7 × 104 molecules of TF per cell were estimated, similar to the amounts found in ECV304 cell lysates (2.9 ± 0.6 × 104 molecules/cell), suggesting that all TFag was translocated to the cell surface. Phorbol myristate acetate (PMA) stimulation of ECV304 cells resulted in an increase of TF mRNA levels, which was abrogated when gene transcription was impaired, suggesting a transcriptional regulation of the TF gene by PMA. In contrast, TFag was not elevated by PMA‐stimulation, indicating the existence of additional posttranscriptional mechanisms. Thus, ECV304 cells constitute a singular endothelial cell model for exploring the regulation of TF expression. Am. J. Hematol. 56:71–78, 1997. © 1997 Wiley‐Liss, Inc.