Cell Growth Inhibition by the IRF-1 System

A genetic approach, based on the growth regulatory protein interferon-regulated-factor- 1 (IRF-1), activated by the addition of estradiol, has been applied to regulate BHK cell growth. With the addition of 100 nM of estradiol 48 hours after inoculation, growth inhibition occurs within 24 hours but is followed by a significant decrease in cell viability, whereas rec-protein specific productivity is not significantly altered. Viability decrease is not due to estradiol effect and is independent upon the culture system. In order to define strategies to extend the stationary growth phase, several parameters have been studied: estradiol concentration, time post inoculation for estradiol addition and time span of estradiol exposure. When the time of contact between the cells and estradiol is reduced the cell viability increases, achieving similar values of the control, without the estradiol, and leading to a stationary growth phase extension.