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Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells.

ABSTRACT: BACKGROUND: ZAP-70 is an independent negative prognostic marker in chronic lymphocytic leukemia (CLL). Usually, its expression is investigated by flow cytometric protocols in which the percentage of ZAP-70 positive CLL cells is determined in respect to isotypic control (ISO-method) or residual ZAP-70 positive T cells (T-method). These methods, however, beside suffering of an inherent subjectivity in their application, may give discordant results in some cases. The aim of this study was to assess the prognostic significance of these methods in comparison with another in which ZAP-70 expression was evaluated as a Mean-Fluorescence-Intensity Ratio between gated T and CLL cells (T/B Ratio-method). METHODS: Cytometric files relative to ZAP-70 determination according to the three readouts were retrospectively reviewed on a cohort of 173 patients (test set), all with complete clinical and biological prognostic assessment and time-to-treatment (TTT) available. Findings were then validated in an independent cohort of 341 cases from a different institution (validation set). RESULTS: The optimal prognostic cut-offs for ZAP-70 expression were selected at 11% (ISO-method) or 20% of positive cells (T-method), as well as at 3.0 (T/B Ratio-method) in the test set; these cut-offs yielded 66, 60 and 73 ZAP-70+ cases, respectively. Univariate analyses resulted in a better separation of ZAP-70+ vs. ZAP-70- CLL patients utilizing the T/B Ratio, compared to T- or ISO-methods. In multivariate analyses which included the major clinical and biological prognostic markers for CLL, the prognostic impact of ZAP-70 appeared stronger when the T/B-Ratio method was applied. These findings were confirmed in the validation set, in which ZAP-70 expression, evaluated by the T- (cut-off = 20%) or T/B Ratio- (cut-off = 3.0) methods, yielded 180 or 127 ZAP-70+ cases, respectively. ZAP-70+ patients according to the T/B Ratio-method had shorter TTT, both if compared to ZAP-70- CLL, and to cases classified ZAP-70+ by the T-method only. CONCLUSIONS: We suggest to evaluate ZAP-70 expression in routine settings using the T/B Ratio-method, given the operator and laboratory independent feature of this approach. We propose the 3.0 T/B Ratio value as optimal cut-off to discriminate ZAP-70+ (T/B Ratio less than 3.0) from ZAP-70- (T/B Ratio more/equal than 3.0) cases.

SUBMITTER: Rossi FM

PROVIDER: S-EPMC2846891 | biostudies-other | 2010

REPOSITORIES: biostudies-other

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Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells.

Rossi Francesca M FM Del Principe Maria Ilaria MI Rossi Davide D Irno Consalvo Maria M Luciano Fabrizio F Zucchetto Antonella A Bulian Pietro P Bomben Riccardo R Dal Bo Michele M Fangazio Marco M Benedetti Dania D Degan Massimo M Gaidano Gianluca G Del Poeta Giovanni G Gattei Valter V

Journal of translational medicine 20100308

<h4>Background</h4>ZAP-70 is an independent negative prognostic marker in chronic lymphocytic leukemia (CLL). Usually, its expression is investigated by flow cytometric protocols in which the percentage of ZAP-70 positive CLL cells is determined in respect to isotypic control (ISO-method) or residual ZAP-70 positive T cells (T-method). These methods, however, beside suffering of an inherent subjectivity in their application, may give discordant results in some cases. The aim of this study was to ...[more]

PMID: 20211015

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Project description:Several studies demonstrated IgVH mutation status and ZAP-70 expression as the most relevant prognostic markers in CLL, suggesting the separation of two patient subgroups: with good (MTZAP-70-) and poor prognosis (UMZAP-70+). We determined gene expression of B cells in 112 CLL patients divided into three classes: the first with IgVHMT and ZAP-70-, the second with IgVHUM and ZAP-70+, and the third included both IgVHUM ZAP-70- and IgVHMT ZAP-70+. We found LPL, AGPAT2, MBOAT1, CHPT1, AGPAT4, PLD1 genes encoding enzymes involved in lipid (glycerolipid/glycerophospholipid) metabolism overexpressed in UMZAP-70+. In addition, this study demonstrates the role of ARSD, a gene belonging to the sphingolipid metabolism, as a new gene significantly overexpressed in UMZAP-70+ in respect to MTZAP-70-. ARSD protein was found at significantly higher concentrations in UMZAP-70+ compared to MTZAP-70- CLL B cells and B cells from healthy individuals by Western blotting. Statistical analysis identified a strong correlation between ARSD and IgVH mutation status; ARSD protein level was associated with the requirement of therapy for CLL patients and for this purpose it is as good as IgVH mutational status. Our study highlights ARSD as a promising new prognostic factor in CLL and sphingolipid metabolism as a putative new biological mechanism in CLL. In this study we performed gene expression profiling of B cells on 112 CLL patients divided into three classes based on IgVH mutational status and ZAP-70 protein expression: class one with mutated IgVH and ZAP-70-, class two with unmutated IgVH and ZAP-70+, and class three included CLL patients with unmutated IgVH and ZAP-70-, or mutated IgVH and ZAP-70+, respectively. The decision to divide CLL patients in three categories was due to the clinical feature and the molecular heterogeneity of CLL, in order to elaborate different molecular signature capable of reveal biological mechanisms, and to identify new potential molecular predictors for prognostic assessment or genetic risk. RNA was extracted and quantified for high-density oligonucleotide microarrays Human Genome U133 Plus 2.0 GeneChip (Affymetrix, Santa Clara, CA). A first cohort of 62 subjects was analyzed using GeneChip Expression 3' Amplification One-Cycle Target Labeling Kit, while a second cohort of 50 subjects using GeneChip 3'IVT Express Kit, according to manufacturerM-bM-^@M-^Ys protocol (Affymetrix), respectively.

Dataset Information

Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells.

Publications

Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells.

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