TCL1 Expression in Chronic Lymphocytic Leukemia Correlates with the Intensity of 11q Deletions and ZAP-70.

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Blood (ASH Annual Meeting Abstracts) 2007 110: Abstract 2068

© 2007 American Society of Hematology

TCL1 Expression in Chronic Lymphocytic Leukemia Correlates with the Intensity of

11q Deletions and ZAP-70.

Rassenti, PhD1, L. Huynh, B.S.1,*, G.W. Basak, MD, PhD1,*, E.M. Ghia,

PhD1,*, D. Van Dyke, PhD2,*, N. Heerema, PhD2,*, D. Zahrieh, PhD2,*, P. DalCin,

PhD2,*, M.L. Dell'Aquila, PhD1,*, P. Koduru, PhD2,*, J.C. Byrd, MD2,*, N.E. Kay,

MD2,*, K.R. Rai, MD2,*, J.R. Brown, MD, PhD2,*, W.W. Wierda, MD, PhD2,*, A.W.

Greaves, B.S.2,* and J. Kipps, MD, PhD2

1 Medicine, University of California, San Diego, La Jolla, CA, USA and 2 CLL

Research Consortium.

Abstract

The TCL1 (T-cell leukemia/lymphoma1) oncogene is a coactivator of the AKT

oncoprotein, an essential molecule in the transduction of antiapoptotic signals

in T and B cells. Eµ-TCL transgenic mice with B cells with high TCL1 expression

develop the aggressive phenotype of chronic lymphocytic leukemia (CLL). Studies

in human CLL have found that expression of TCL1 correlates with high expression

of ZAP-70 and use of unmutated IgVH genes. The expression of TCL1 may be

regulated in part by microRNA, miR-29 and miR-181, which map to chromosome

11(11q). Because aberrations at 11q have been associated with poor prognosis in

CLL, we interrogated the relationship between deletions at 11q and expression of

TCL1 and ZAP-70. We used a direct immunophenotyping method to investigate the

relative co-expression levels of TCL1 and ZAP-70 within CLL cells and examined

the relationship between such levels and the proportion of leukemia cells within

the CLL population bearing 11q deletions, as detected by FISH analysis. Direct

staining of intracellular TCL1 protein was performed by using the monoclonal

anti-TCL1 antibody (clone 1-21) labeled with a647 in combination with the

established ZAP-70 protocol (NEJM 2004; 351:893) together with mAb directed

against CD5 and B cell surface antigens. Negative staining levels were set using

isotype control antibodies. FISH was performed on interphase nuclei by using

uniform and cross-validated procedures at all CRC sites using the CLL-panel from

Vysis. Chromosomal abnormalities were detected in 76% (520) of the 680 CLL

samples analyzed. Sixteen percent of the patients had leukemia cells with

monoalleleic deletions at 11q. We performed flow cytometry for intracellular

co-expression TCL1 and ZAP-70 on cryopreserved samples obtained from 25 CLL

patient samples with varying proportions of cells with the 11q deletion (10% to

98% abnormal cells with 11q deletion, mean 70%) and 30 CLL samples lacking any

chromosomal abnormalities. We detected significantly higher levels of TCL1 in

CLL cells that expressed ZAP-70 and/or unmutated IgVH genes. The ZAP-70pos cases

(39/55) had a median percent of TCL1pos cells of 34% compared to 15% for the

ZAP-70neg cases. The cases using unmutated IgVH genes (43/55) had a median

percent of TCL1pos cells of 31%, which was greater than the 19% median observed

for cases that used mutated IgVH genes. Multiparameter analyses revealed that

the ZAP-70 positive fraction of each CLL clone had significantly higher levels

of TCL1 than did the ZAP-70 negative cells (mean=45% versus 29%, respectively,

p=0.002). We observed a significant difference between the expression levels of

TCL1 for CLL cells that had deletions in 11q relative to that of CLL cells

lacking any chromosomal abnormalities (mean=41% versus 18%, respectively

p=0.0002). In addition, we observed a relationship between the levels of TCL1

expressed in leukemia cell populations and the relative proportion of leukemia

cells with deletions at 11q. This study reveals a relationship between the

levels of TCL1 expression in CLL leukemia-cell expression of ZAP-70, and the

relative proportions of leukemia cells having deletions at 11q. Studies are in

progress to define whether these relationships can be explained by altered

expression of microRNA that map to 11q, which might also account for the noted

adverse prognosis of CLL that has deletions at 11q.

Footnotes

Disclosure: No relevant conflicts of interest to declare.