Purpose: We have recently shown that the novel nuclear factor-κB (NF-κB) inhibitor LC-1 is effective in primary chronic lymphocytic leukemia (CLL) cells. Here we elucidated the mechanism of action of LC-1, evaluated its relative cytotoxicity in prognostic subsets, and investigated its potential synergistic interaction with fludarabine. Experimental Design: Ninety-six fully characterized CLL cases were assessed for in vitro sensitivity to LC-1 and fludarabine. In selected cases, caspase activation, inhibition of Rel A DNA binding, and the transcription of CFLAR, BIRC5, and BCL2 were measured before and after exposure to LC-1. In addition, the efficacy of LC-1 was assessed in the presence of the survival factors CD154 and interleukin-4, and the potential synergistic interaction between LC-1 and fludarabine was evaluated. Results: Cell death was associated with caspase-3 activation mediated via activation of both caspase-8 and caspase-9. Apoptosis was preceded by a reduction of nuclear Rel A DNA binding and inhibition of CFLAR, BIRC5, and BCL2 transcription. Importantly, LC-1 overcame the cytoprotective effects by interleukin-4 and CD40 ligand and was equipotent in CLL cells derived from good and bad prognostic subsets. LC-1 exhibited strong synergy with fludarabine, and the combination produced a highly significant mean dose reduction index for fludarabine of >1,000. Conclusions: In view of imminent first-in-man study of LC-1 in Cardiff, these data show an important mechanistic rationale for the use of LC-1 in this disease. Furthermore, it validates the concept of targeting nuclear factor-κB in CLL and identifies the therapeutic potential of LC-1 in combination with fludarabine even in patients with fludarabine resistance.
Hewamana, S., Lin, T. T., Jenkins, C., Burnett, A. K., Jordan, C. T., Fegan, C., ... Pepper, C. (2008). The Novel Nuclear Factor-κB Inhibitor LC-1 Is Equipotent in Poor Prognostic Subsets of Chronic Lymphocytic Leukemia and Shows Strong Synergy with Fludarabine. Clinical Cancer Research, 14(24), 8102-8111. https://doi.org/10.1158/1078-0432.CCR-08-1673