EDN1 and neoplasm: In addition, endothelin 1 (Edn1) was maximally 10fold downregulated, but showed a short delay compared to Ednrb and Ece1. Common to all three genes was a gradual return to an expression ratio, which was similar to that of control cells growing in vitro after the respective tumor cells had been re-isolated and were grown under standard culture conditions (37°C, humidified atmosphere with 5% CO2).