Antiproliferative effects of IFN-alpha correlate with the downregulation of nuclear factor-kappa B in human Burkitt lymphoma Daudi cells

Interferon-alpha (IFN-alpha) is known to exhibit antiviral, antiproliferati ve, and immunomodulatory properties through mechanisms still not fully unde rstood. Nuclear transcription factor-kappa B (NF-kappaB) plays a major role in viral replication, cell proliferation, and immune response. Whether ant iproliferative effects of IFN are mediated through suppression of NF-kappaB is not known. We, therefore, examined the relationship between the antipro liferative effects of IFN-alpha and NF-kappaB activity in a human Burkitt l ymphoma Daudi cell line. These cells were found to constitutively express h igh levels of active NF-kappaB that cannot be further activated by tumor ne crosis factor (TNF). Treatment of cells with IFN-alpha suppressed the activ ated NF-kappaB in a dose-dependent manner, with an optimum effect at 10 U/m l in 72 h. Suppression of NF-kappaB correlated with a concomitant decrease in the cytoplasmic levels of I kappaB alpha, the inhibitory protein of NF-k appaB, known to be regulated by NF-kappaB. Downregulation of constitutive N F-kappaB activity correlated with a decrease in cell proliferation by IFN-a lpha. Overall, our results suggest that IFN-alpha is a potent suppressor of constitutive NF-kappaB, which may contribute to the inhibition of cell pro liferation.