Immunohistochemical analysis of ZAP-70 expression in B-cell lymphoid neoplasms

Abstract

ZAP-70 is a tyrosine kinase that participates in early B-cell differentiation and is a prognostic factor in chronic lymphocytic leukaemia (CLL), where it is associated with an unmutated configuration of the IgV(H) genes. In this study ZAP-70 expression was studied by immunohistochemistry in a spectrum of B-cell lymphoid neoplasms; this staining method was compared with flow cytometry, and the relationship of ZAP-70 expression to mutational status and prognosis was assessed. 242 tissue samples from 225 patients with B-cell lymphoid neoplasms arising at different maturational stages were included. Flow cytometry was performed in all CLL cases (n = 52). IgV(H) mutational status was determined in 25 CLL and 12 mantle cell lymphoma (MCL) patients. ZAP-70 was positive in 34/52 (65%) CLL, 9/31 (31%) Burkitt's lymphoma, 2/7 (29%) lymphoblastic lymphomas, 3/36 (8%) MCL, 1/23 (4%) marginal zone lymphoma, and 1/45 (2%) diffuse large B-cell lymphomas, but in none of the 19 follicular lymphomas or the 14 Hodgkin lymphomas. An identical ZAP-70 pattern was obtained in six patients with simultaneous biopsies from different sites and in 12 patients with sequential biopsies. Immunohistochemistry and flow cytometry gave identical results in 48 the 52 CLLs. All but one ZAP-70-positive CLL had IgV(H) gene in an unmutated configuration, whereas all but one ZAP-70-negative CLL had somatically hypermutated IgV(H). The 12 MCLs analysed were ZAP-70 negative regardless of IgV(H) mutational status (4 mutated, 8 unmutated). ZAP-70 positive CLL was associated with a shorter overall survival (median time 103 months vs. 293 months, p = 0.01) and a shorter time to disease progression (median time 26 months vs. 60 months, p = 0.01). In conclusion, ZAP-70 is expressed in several types of B-cell neoplasm and is easily detected by immunohistochemistry, providing a useful prognostic marker in patients with CLL from whom no other material is available or when other techniques for its assessment cannot be performed.

ZAP-70 expression, as detected by immunohistochemistry on bone marrow biopsies from early-phase CLL patients, is a strong adverse prognostic factor

“…In addition, FC is not simple to standardize for intracellular antigens as ZAP-70 25 and, moreover, fresh or frozen viable cells are needed, thus complicating the centralization in reference laboratories and impeding retrospective studies. 15,17 The degree of concordance between ZAP-70 expression and IGHV mutational status was variable in the different series, ranging between 75 and 490%, 12-14 likely owing to the different techniques used. In particular, in the largest series analysed 14 the concordance rate between ZAP-70 expression evaluated by FC and IGHV mutation results was 77%.…”

“…Data concerning ZAP-70 protein expression detected by IHC method in CLL are promising, but a standardized protocol has not been established yet for bone marrow (BM) samples. 10,12,16,17 The use of BM trephine biopsies could represent a potentially suitable material to evaluate ZAP-70, as this tissue is in most cases, infiltrated by neoplastic lymphocytes and BM biopsy is largely included in the diagnostic evaluation of CLL patients. 18 In this study, we analysed the expression of ZAP-70 protein by IHC on BM biopsies taken at presentation of 156 patients with CLL seen at our institution in order to evaluate the prognostic value of this parameter.…”

Clinical implications of ZAP‐70 expressionin chronic lymphocytic leukemia

“…The expression of ZAP-70 can be assessed by different methods, such as Western blotting, quantitative RT-PCR, immunohistochemistry, and flow cytometry (20)(21)(22). Flow cytometry is the most useful technique, as it is a precise and fast methodology extensively used in routine diagnosis of hematological malignancies.…”

ZAP‐70 expression is low in normal precursor B cells or hematogones

“…However with B cell activation the levels are upregulated, indicating a functional role of the ZAP 70 pathway in B cells, as well as T cells (7)(8)(9)11). Given the observation that ZAP 70 expression can be seen in a variety of B cell malignancies (9,10,(12)(13)(14)(15), this may be another indication that some lymphoproliferative disorders display an activated phenotype. Our observation that ZAP-70 is not expressed in normal precursor B cells, along with the reports that later B cell maturation stages do have upregulated levels of this Syk family tyrosine kinase and its absence can block maturation from pro-B to pre-B cells (16), suggests that the ZAP 70 pathway can be turned on and off during the normal development and physiologic response of B cells.…”