ZAP-70 expression as a surrogate for immunoglobulin-variable-region mutations in chronic lymphocytic leukemia.
BACKGROUND
The mutational status of immunoglobulin heavy-chain variable-region (IgVH) genes in the leukemic cells of chronic lymphocytic leukemia (CLL) is an important prognostic factor in the disease. We investigated whether the expression of ZAP-70 by CLL cells correlated with the IgVH mutational status, disease progression, and survival.


METHODS
The expression of ZAP-70 was analyzed in T-cell and B-cell lines and in peripheral-blood samples from 56 patients with CLL with the use of flow cytometry, Western blotting, and immunohistochemistry. The results were correlated with the IgVH mutational status and clinical outcome.


RESULTS
ZAP-70 was detected by flow-cytometric analysis in cells of T-cell lineage and in leukemic cells from 32 of 56 patients with CLL. In all patients in whom at least 20 percent of the leukemic cells were positive for ZAP-70, IgVH was unmutated, whereas IgVH mutations were found in 21 of 24 patients in whom less than 20 percent of the leukemic cells were positive for ZAP-70 (P<0.001). Concordant results were obtained when ZAP-70 expression was assessed by immunohistochemistry or Western blotting. The level of ZAP-70 expression did not change over time (median, 37 months) in sequential samples from 30 patients with CLL. Patients with Binet stage A CLL who had at least 20 percent ZAP-70-positive leukemic cells had more rapid progression and poorer survival than those with less than 20 percent ZAP-70-positive cells.


CONCLUSIONS
Among patients with CLL, expression of ZAP-70, as detected by flow-cytometric analysis, correlated with IgVH mutational status, disease progression, and survival.
Department of Hematology, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Barcelona, Spain.
Marta
M
Crespo
Francesc
F
Bosch
Neus
N
Villamor
Beatriz
B
Bellosillo
Dolors
D
Colomer
María
M
Rozman
Silvia
S
Marcé
Armando
A
López-Guillermo
Elies
E
Campo
Emili
E
Montserrat
D036541:ADP-ribosyl Cyclase / Q000032:analysis; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD / Q000032:analysis; D018450:Disease Progression; D005434:Flow Cytometry; D005803:Genes, Immunoglobulin; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000276:immunology / Q000401:mortality; D008562:Membrane Glycoproteins; D009154:Mutation; D011379:Prognosis; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism; D016019:Survival Analysis; D051746:ZAP-70 Protein-Tyrosine Kinase
D015703:Antigens, CD; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1