Background: Expression of T cell specific zeta-associated protein 70 (ZAP-70) by B-cell chronic lymphocytic leukemia (B-CLL) cells, as investigated by flow cytometry, has both prognostic relevance and predictive power as surrogate for immunoglobulin heavy chain variable region (IgVH) mutations, although a standardization of the cytometric protocol is still lacking. Methods: Flow cytometric analyses for ZAP-70 were performed in peripheral blood samples from 145 B-CLL (124 with IgVH mutations) by a standard three-color protocol. Identification of ZAP-70+ cell population was based on an external negative control, i.e., the isotypic control (ISO method) or an internal positive control, i.e., the population of residual normal T/NK cells (TNK method). A comparison between these two approaches was performed. Results: While 86/145 cases were concordant as for ZAP-70 expression according to the two methods (ISO+TNK+ or ISO -TNK-), 59/145 cases had discordant ZAP-70 expression, mainly (56/59) showing a ISO+TNK- profile. These latter cases express higher levels of ZAP-70 in their normal T cell component. Moreover, discordant ISO+TNK- cases had a IgVH gene mutation profile similar to that of concordantly positive cases and different from ZAP-70 concordantly negative B-CLL. Conclusion: Analysis of ZAP-70 expression by B-CLL cells by using the ISO method allows to overcome the variability in the expression of ZAP-70 by residual T cells and yields a better correlation with IgVH gene mutations. A receiver operating characteristic analysis suggests to employ a higher cut-off than the commonly used 20%. A parallel evaluation of the prognostic value of ZAP-70 expression, as determined according to the ISO and TNK methods, is still needed.
- Propuostic factors
ASJC Scopus subject areas
- Cell Biology
- Pathology and Forensic Medicine