Effect of high cell density stress on the expression of transcription factor NF-κB

Nuclear factor NF-κB is involved in the transcriptional regulation of several genes. Our data in 244B human lymphoblastoid cells demonstrate for the first time that NF-κB expression was affected by cell density in cells treated with phorbol 12-myristate 13-acetate (PMA). When the cell density was 1 x 10⁶ cells/ml, the expression was maximum at 8 h; the expression at this time was less at the higher cell densities of 2.5 and 5.0 x 10⁶ cells/ml. The expression was dependent on the time at which the cells were harvested, with higher levels being observed a second time at 36 h, following negligible expression for all 3 cell densities at 16 h. NF-κB subunit p50 expression was highest at the lowest cell density, while p65 expression was unaltered at the three cell densities.