ZAP-70 expression in B-cell chronic lymphocytic leukemia: Evaluation by external (isotypic) or internal (T/NK cells) controls and correlation with IgVH mutations
✍ Scribed by Antonella Zucchetto; Riccardo Bomben; Michele Dal Bo; Paola Nanni; Pietro Bulian; Francesca Maria Rossi; Maria Ilaria Del Principe; Simone Santini; Giovanni Del Poeta; Massimo Degan; Valter Gattei
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 575 KB
- Volume
- 70B
- Category
- Article
- ISSN
- 1552-4949
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✦ Synopsis
Abstract
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 (IgV~H~) 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 IgV~H~ 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 IgV~H~ 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 IgV~H~ 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. © 2006 International Society for Analytical Cytology