AACR: Cytogenetics on CLL Survival and Sensitivity to CpG ODN

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Abstract Number: 3795

Impact of cytogenetics on B-cell chronic lymphocytic leukemia

survival and sensitivity to treatment with CpG oligonucleotides in-

vitro

Bernd Jahrsdoerfer, Sue E. Blackwell, Christiana M. , J.

Weiner. Holden Comprehensive Cancer Center, Iowa City, IA.

Immunostimulatory CpG-containing oligonucleotides (CpG ODN) have a

number of immunologic effects and are felt to be attractive as

potential components of cancer immunotherapy. We previously

demonstrated CpG ODN treatment of B-cell chronic lymphocytic leukemia

(CLL) cells induces upregulation of a variety of surface molecules

including those involved in apoptosis, costimulation and activation.

CpG ODN can also induce apoptosis of CLL cells in some samples. While

CLL phenotypic changes induced by CpG ODN are relatively uniform,

induction of apoptosis varies considerably from sample to sample.

Induction of apoptosis does not correlate with parameters such as

white blood cell count, CD38 expression or serum LDH. We therefore

evaluated if the cytogenetics of CLL cells correlates with

spontaneous, or CpG ODN-mediated, survival in vitro.

CLL cells were harvested from 23 subjects and incubated in vitro with

or without CpG ODN or control ODN for 4 and 7 days. Apoptosis was

measured by a combination of standard Annexin V/PI staining and a

counting method utilizing calibration beads. As in our prior studies,

considerable heterogeneity was noted in the survival of CLL cells in

both the control and CpG ODN treated samples.

Incubation with CpG ODN, but not control ODN, resulted in decreased

numbers of viable cells and increased numbers of apoptotic cells in

17 of 23 CLL samples. The mutational status of the CLL samples was

determined by interphase FISH. Correlation between cell

survival/apoptosis and FISH demonstrated that in the absence of CpG

ODN, spontaneous apoptosis of CLL cells in media alone was

significantly higher in samples with 17p deletions or other mutations

(11q deletion or trisomy 12) when compared to samples with normal

karyotype or samples bearing the 13q deletion as single abnormality

(** p< 0.005).

In contrast, in the presence of CpG ODN, CLL cell apoptosis was

significantly lower in samples with 17p deletions or other mutations

when compared to samples with a normal karyotype or 13q deletion as

single abnormality (** p< 0.002).

We conclude that the cytogenetics of CLL cells impacts on in vitro

cell survival. CLL cells bearing a normal karyotype or a 13q deletion

survive longer in vitro despite the better clinical prognosis of that

subgroup of patients.

CpG ODN is most effective at inducing apoptosis in this same subset

of samples, i.e. those with better viability when untreated, and has

less of an effect on cells bearing 17p deletions or other mutations.

Ongoing studies are exploring the mechanisms responsible for both

spontaneous and CpG ODN-induced apoptosis in these subsets of

patients.

This study demonstrates the variable biologic behavior of CLL based

on cytogenetic abnormalities can be measured in the laboratory as

well as the clinic, and that response to biologic agents can vary

significantly based on those abnormalities.

Presenter: Bernd Jahrsdoerfer

Affiliation: Holden Comprehensive Cancer Center, Iowa City, IA; E-

mail: bernd-jahrsdoerfer@...

Copyright © 2004 American Association for Cancer Research. All rights

reserved. Citation information: Proceedings of the AACR, Volume 45,

March 2004.