Inhibition of IκB kinase subunit 2 in cutaneous T-cell lymphoma down-regulates nuclear factor-κB constitutive activation, induces cell death, and potentiates the apoptotic response to antineoplastic chemotherapeutic agents

Purpose: A key molecular feature of cutaneous T-cell lymphomas (CTCL) is the constitutive activation of the nuclear factor-kappa B (NF-kappa B) transcription factor. We investigated in vitro the effects on CTCL survival and chemoresistance of a specific inhibition of I kappa B kinase subunit 2 (IKK2). Experimental Design: Selective IKK2 inhibition was carried out by transfection of SeAx and MyLa CTCL lines with an inactive form of IKK2 and by exposing these lines and tumor cells from 10 patients with Sezary syndrome (SS) to AS602868, a new IKK2 inhibitor. The constitutive nuclear translocation of NF-kappa B was analyzed by electrophoretic mobility shift assay and confocal microscopy. Apoptosis was determined by Annexin V/propidium iodide-positive staining and mitochondrial transmembrane potential alterations as well as poly (ADP-ribose)polymerase cleavage. The expression of Bcl-2 family oncoproteins and survivin was studied by immunoblotting. Results: Specific IKK2 inhibition resulting from transfection or from incubation with AS602868 allowed a down-regulation of NF-kappa B transcriptional activity. As shown by electrophoretic mobility shift assay and apoptosis assays, AS602868 down-regulated the nuclear translocation of NF-kappa B and induced a potent apoptotic response in CTCL lines and in tumor cells from patients with SS while preserving the viability of both peripheral blood lymphocytes from healthy donors and of nonmalignant T cells from SS patients. Moreover, CTCL death induction by conventional antineoplastic agents etoposide and vincristine was potentiated by AS602868. Finally, AS602868-induced apoptosis of CTCL cells was associated with an up-regulation of Bax dimers and a decrease of survivin. Conclusion: These results indicate that IKK2 inhibition represents a promising strategy for the treatment of advanced stages of CTCL.