12th Congress of the European Hematology ... - Haematologica

with a p value of ≥ 0.10. Sets of measurement data were compared for
statistical significance using the Student’s t test or Mann-Whitney U
test. Sets of enumeration data were compared by χ 2 and Fisher’s exact
tests. Two-sided tests with an a level of 0.05 were used in all analyses.
Results. 74% of informative cases had stage A disease, 43% had unmutated
IgVH genes, 30% had high CD38 expression and 20% had adverse
cytogenetic abnormalities (loss of p53 or ATM). The median time from
diagnosis to blood sampling was 6.5 months and the median follow-up
time from diagnosis 35.6 months. Low p53 or p21CIP1 index values
were present in one third of patients and were associated with a significantly
shorter overall survival and treatment-free interval (Figure 1).
Although p53 dysfunction was strongly associated with loss of p53 or
ATM, the majority of patients with p53 dysfunction did not have either
of these adverse chromosomal abnormalities. Sub-group analysis
revealed p53 dysfunction to be a powerful predictor of adverse outcome
among patients classified as good risk by clinical staging, chromosomal
analysis, IgVH mutation analysis or CD38 expression. In multivariate
analysis, p53 dysfunction was the only independent predictor of
adverse outcome in patients with early-stage disease, those without
adverse chromosomal abnormalities, and those with mutated IgVH
genes (hazard ratio 7.8, 3.1 and 14.6 respectively). Summary/Conclusions.
These findings identify p53 dysfunction as a novel independent prognostic
factor in CLL. In addition, they provide the first demonstration
in human cancer that clinical outcome can be predicted by functional
probing of a DNA-damage response pathway.
Figure 1. TFI and OS of the two groups of CLL patients.
0911
THE ANTITUMOR ACTIVITY OF LUMILIXIMAB IS MEDIATED THROUGH THE INDUCTION
OF CASPASE-9DEPENDENT APOPTOSIS AND IS SYNERGISTIC WITH RITUXIMAB AND
FLUDARABINE IN CD23 + CLL AND LYMPHOMA CELLS
N. Pathan, 1 J.C. Byrd, 2 K. Hariharan, 1 P. Chu, 1 A. Molina1 1 2 Biogen Idec, SAN DIEGO, USA; Ohio State University, COLUMBUS,
USA
Background. The effectiveness of monoclonal antibody therapy in treating
patients with chronic lymphocytic leukemia (CLL) has prompted
interest in other antibodies specific for alternate B-cell antigens. The CD23
antigen, a transmembrane glycoprotein that functions as a low-affinity
receptor for immunoglobulin E, is highly expressed on most CLL cells and
represents a potential therapeutic target. Aims. We examined the ability
of lumiliximab, an IgG1 chimeric monoclonal antibody against CD23, to
mediate cytotoxicity via direct apoptosis, antibody-dependent cellular
cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC)
in CD23 + malignant B-cell lines and CLL cells. We also evaluated the antitumor
activity of lumiliximab in a disseminated human lymphoma model.
Methods. Cytotoxicity was determined using flow cytometry to assess
the induction of apoptosis via caspase-3, 51CR-release to determine
ADCC, and flow cytometry analysis of propidium iodide staining to
quantify CDC. The activation of caspase-8 and -9 and expression of proand
anti-apoptotic proteins were assessed before and after treatment with
lumiliximab using Western blot analysis. The anti-tumor activity of lumiliximab
was evaluated in vivo using the CD23 + SKW6.4 human lymphoma/SCID
mouse model. Results. In CD23 + B-cell lines, lumiliximab
induced apoptosis, ADCC, and CDC. Lumiliximab induced apoptosis
and ADCC in CLL cells; however, the degree of ADCC was low to moderate
compared with that seen in CD23 + B-cell lines. There was no evidence
of CDC induction in primary CLL cells after exposure to lumiliximab.
Treatment with lumiliximab in the presence of an anti-human IgG
Fc crosslinking antibody resulted in increased staining of activated caspase-3
in CLL cells’the median percentage of apoptosis was 46% compared
with 16% with the isotype control (p