ZAP-70 compared with immunoglobulin heavy-chain gene mutation status as a predictor of disease progression in chronic lymphocytic leukemia.
BACKGROUND
The course of chronic lymphocytic leukemia (CLL) is variable. In aggressive disease, the CLL cells usually express an unmutated immunoglobulin heavy-chain variable-region gene (IgV(H)) and the 70-kD zeta-associated protein (ZAP-70), whereas in indolent disease, the CLL cells usually express mutated IgV(H) but lack expression of ZAP-70.


METHODS
We evaluated the CLL B cells from 307 patients with CLL for ZAP-70 and mutations in the rearranged IgV(H) gene. We then investigated the association between the results and the time from diagnosis to initial therapy.


RESULTS
We found that ZAP-70 was expressed above a defined threshold level in 117 of the 164 patients with an unmutated IgV(H) gene (71 percent), but in only 24 of the 143 patients with a mutated IgV(H) gene (17 percent, P<0.001). Among the patients with ZAP-70-positive CLL cells, the median time from diagnosis to initial therapy in those who had an unmutated IgV(H) gene (2.8 years) was not significantly different from the median time in those who had a mutated IgV(H) gene (4.2 years, P=0.07). However, the median time from diagnosis to initial treatment in each of these groups was significantly shorter than the time in patients with ZAP-70-negative CLL cells who had either mutated or unmutated IgV(H) genes (P<0.001). The median time from diagnosis to initial therapy among patients who did not have ZAP-70 was 11.0 years in those with a mutated IgV(H) gene and 7.1 years in those with an unmutated IgV(H) gene (P<0.001).


CONCLUSIONS
Although the presence of an unmutated IgV(H) gene is strongly associated with the expression of ZAP-70, ZAP-70 is a stronger predictor of the need for treatment in B-cell CLL.
Rassenti
Laura Z
LZ
Chronic Lymphocytic Leukemia Research Consortium, University of California, San Diego, La Jolla 92093, USA.
Huynh
Lang
L
Toy
Tracy L
TL
Chen
Liguang
L
Keating
Michael J
MJ
Gribben
John G
JG
Neuberg
Donna S
DS
Flinn
Ian W
IW
Rai
Kanti R
KR
Byrd
John C
JC
Kay
Neil E
NE
Greaves
Andrew
A
Weiss
Arthur
A
Kipps
Thomas J
TJ
D001402:B-Lymphocytes / Q000378:metabolism*; D018076:DNA, Complementary; D018450:Disease Progression; D005434:Flow Cytometry; D005803:Genes, Immunoglobulin; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism* / Q000628:therapy; D009154:Mutation; D016016:Proportional Hazards Models; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell; D017422:Sequence Analysis, DNA; D014407:Tumor Cells, Cultured; D051746:ZAP-70 Protein-Tyrosine Kinase
D018076:DNA, Complementary; D007143:Immunoglobulin Heavy Chains; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human