NF-κB is essential for the progression of KSHV- and EBV-infected lymphomas in vivo

Activated NF-kappa B is a critical mechanism by which lymphoma cells infected by Epstein-Barr virus (EBV/HHV-4) and Kaposi sarcoma herpesvirus (KSHV/HHV-8) are protected from apoptotic stress. Selective pharmacologic inhibition of constitutive NF-kappa B activity induces apoptosis in KSHV- and EBV-infected lymphoma cells. In both tumor types, pharmacologic inhibition of NF-kappa B in vitro induced identical mitochondrially mediated apoptosis cascades. Assessment of gene regulation by microarray analysis revealed that the inhibition of NF-kappa B in tumor cells results in the down-regulation of a distinct group of prosurvival genes, including clAP-1, cIAP-2, cFLIP, and IL-6. Using EBV- and KSHV-associated lymphomas in a murine system, we demonstrated that Bay 117082, a selective pharmacologic inhibitor of NF-kappa B prevents or delays tumor growth and prolongs disease-free survival. Inhibition of NF-kappa B activity and tumor growth responses were further documented using a traceable reporter KSHV-positive cell line and in vivo imaging. These findings indicate that specific NF-kappa B-regulated survival factors work cooperatively to protect KSHV- and EBV-infected lymphoma cells from apoptosis such that they promote the establishment and progression of KSHV- and EBV-associated lymphomas in mice. They also support the use of selective NF-kappa B inhibitors in the treatment of herpesvirus-associated lymphomas.