Expression of ZAP-70 protein correlates with disease stage in chronic lymphocytic leukemia and is associated with, but not generally restricted to, non-mutated Ig VH status.
The mutational status of immunoglobulin variable region genes (Ig VH) is a well established prognostic parameter in chronic lymphocytic leukemia (CLL). Recently, a subset of genes with a characteristic expression profile correlating with the mutational status of B-CLLs has been identified. One of the overexpressed genes in the prognostically unfavorable group of CLL patients with unmutated Ig VH genes encodes for the protein tyrosine kinase ZAP-70, which is physiologically involved in T-cell signaling. Since ZAP-70 has been described to be prognostically relevant in CLL, we analyzed the possible relationship of its expression to the mutational status of Ig VH genes as well as to other prognostic factors in CLL and indolent lymphomas. The mutational status of Ig VH genes was analyzed by seminested PCR, direct sequencing and comparison with the sequences of the EMBL databases in 60 samples of patients with B-CLL and 18 samples of patients with indolent B-cell malignancies. ZAP-70 protein expression was assessed in all samples by immunoblotting and for semiquantitative analysis the ratio of ZAP-70 to tubulin expression was calculated. ZAP-70 protein was found to be expressed in all investigated B-cell malignancies. Expression levels varied within a wide range in each entity. The highest mean level of ZAP-70 expression was observed in unmutated B-CLLs, however, with broad expression variability. High levels of ZAP-70 expression correlated with higher stage Binet B or C and with unmutated Ig VH genes. Overall survival rates estimated by Kaplan-Meier curves did not differ among patients with high or low ZAP-70 expression. We conclude that ZAP-70 is associated with the mutational status of Ig VH genes, but this expression pattern is not present in all individual cases. Furthermore, high levels of ZAP-70 correlated with Binet stages B or C indicating an involvement of ZAP-70 in mechanisms promoting growth of B-CLL cells.
Kim
Soo-Zin
SZ
Department of Internal Medicine III, University Hospital Frankfurt, Germany.
Chow
Kai Uwe
KU
Kukoc-Zivojnov
Natasa
N
Boehrer
Simone
S
Brieger
Angela
A
Steimle-Grauer
Susanne Annette
SA
Harder
Lana
L
Hoelzer
Dieter
D
Mitrou
Paris Sophokles
PS
Weidmann
Eckhart
E
D000328:Adult; D000368:Aged; D001402:B-Lymphocytes / Q000737:chemistry / Q000473:pathology; D018450:Disease Progression; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005803:Genes, Immunoglobulin / Q000235:genetics*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009363:Neoplasm Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D009367:Neoplasm Staging; D011505:Protein-Tyrosine Kinases / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D051746:ZAP-70 Protein-Tyrosine Kinase
D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D009363:Neoplasm Proteins; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human