Constitutive NF-κB and NFAT activation in aggressive B-cell lymphomas synergistically activates the CD154 gene and maintains lymphoma cell survival

Abnormalities in B-lymphocyte CD40 ligand (CD154) expression have been described for a number of immunologic diseases, including B-cell lymphomas. Although functional analysis of the CD154 gene and protein has been extensive, little is known about the mechanisms controlling CD154 expression in activated T cells, and even less is known for normal and malignant B cells. In this study we describe the transcriptional mechanism controlling CD154 expression in large B-cell lymphoma (LBCL). We show that the nuclear factor of activated T cells (NFAT) transcription factor is also constitutively activated in LBCL. We demonstrate that the constitutively active NFATc1 and c-rel members of the NFAT and nuclear factor-kappa B (NF-kappa B) families of transcription factors, respectively, directly interact with each other, bind to the CD154 promoter, and synergistically activate CD154 gene transcription. Downregulation of NFATc1 or c-rel with small interfering RNA (siRNA) or chemical inhibitors inhibits CD154 gene transcription and lymphoma cell growth. These findings suggest that targeting NF-kappa B and NFAT, by inhibiting the expression of these transcription factors, or interdicting their interaction may provide a therapeutic rationale for patients with non-Hodgkin lymphoma of B-cell origin, and possibly other disorders that display dysregulated CD154 expression.