The Novel Nuclear Factor-B Inhibitor LC-1 Is Equipotent in Poor Prognostic Subsets of Chronic Lymphocytic Leukemia and Shows Strong Synergy with Fludarabine

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Clinical Cancer Research 14, 8102-8111, December 15, 2008. doi:

10.1158/1078-0432.CCR-08-1673

The Novel Nuclear Factor-B Inhibitor LC-1 Is Equipotent in Poor Prognostic

Subsets of Chronic Lymphocytic Leukemia and Shows Strong Synergy with

Fludarabine

Saman Hewamana1,2, Thet Thet Lin1, 3, Alan K. Burnett1, Craig T.

Jordan4, Fegan3, Brennan2, Clare Rowntree3 and Pepper1

Authors' Affiliations: Departments of 1 Haematology and 2 Medical Biochemistry

and Immunology, School of Medicine, Cardiff University, and 3 Department of

Haematology, University Hospital of Wales, Cardiff, United Kingdom; and 4

Division of Haematology/Oncology, University of Rochester School of Medicine,

Rochester, New York

Requests for reprints: Saman Hewamana, Department of Haematology, School of

Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, United Kingdom.

Phone: 44-29-20747747; Fax: 44-29-20744655; E-mail: hewamanas@... .

Purpose: We have recently shown that the novel nuclear factor-B (NF- 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-B in

CLL and identifies the therapeutic potential of LC-1 in combination with

fludarabine even in patients with fludarabine resistance.