I-kappa-kinase-2 (IKK-2) inhibition potentiates vincristine cytotoxicity in non-Hodgkin's lymphoma
- Equal contributors
1 Lymphoma Research Laboratory, Wayne State University - School of Med, 540 E. Canfield, 8229 Scott Hall, Detroit, MI 48201, USA
2 Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111-2497, USA
3 Millennium Pharmaceuticals, 40 Landsdowne Street, Cambridge, Massachusetts 02139, USA
4 Clinical Pathology, Wayne State University School of Medicine, 4727 St. Antoine, Detroit, MI 48201, USA
5 Internal Medicine, Wayne State Univeristy, 2224 Ellimann Bldg, 421 E. Canfield, Detroit, MI 48201, USA
6 Karmanos Cancer Institute, 732 HWCRC, 4100 John R, Detroit, MI 48201, USA
Molecular Cancer 2010, 9:228 doi:10.1186/1476-4598-9-228Published: 1 September 2010
IKK-2 is an important regulator of the nuclear factor-κB (NF-κB) which has been implicated in survival, proliferation and apoptosis resistance of lymphoma cells. In this study, we investigated whether inhibition of IKK-2 impacts cell growth or cytotoxicity of selected conventional chemotherapeutic agents in non-Hodgkin's lymphoma.
Two established model systems were used; Follicular (WSU-FSCCL) and Diffuse Large Cell (WSU-DLCL2) Lymphoma, both of which constitutively express p-IκB. A novel, selective small molecule inhibitor of IKK-2, ML120B (N-[6-chloro-7-methoxy-9H-β-carbolin-8-yl]-2-methylnicotinamide) was used to perturb NF-κB in lymphoma cells. The growth inhibitory effect of ML120B (M) alone and in combination with cyclophosphamide monohydrate (C), doxorubicin (H) or vincristine (V) was evaluated in vitro using short-term culture assay. We also determined efficacy of the combination in vivo using the SCID mouse xenografts.
ML120B down-regulated p-IκBα protein expression in a concentration dependent manner, caused growth inhibition, increased G0/G1 cells, but did not induce apoptosis. There was no significant enhancement of cell kill in the M/C or M/H combination. However, there was strong synergy in the M/V combination where the vincristine concentration can be lowered by a hundred fold in the combination for comparable G2/M arrest and apoptosis. ML120B prevented vincristine-induced nuclear translocation of p65 subunit of NF-κB. In vivo, ML120B was effective by itself and enhanced CHOP anti-tumor activity significantly (P = 0.001) in the WSU-DLCL2-SCID model but did not prevent CNS lymphoma in the WSU-FSCCL-SCID model.
For the first time, this study demonstrates that perturbation of IKK-2 by ML120B leads to synergistic enhancement of vincristine cytotoxicity in lymphoma. These results suggest that disruption of the NF-κB pathway is a useful adjunct to cytotoxic chemotherapy in lymphoma.