Expressió de ZAP-70 en linfòcits B normals i síndromes limfoproliferatives B
SUMMARY: BACKGROUND: The mutational status of immunoglobulin variable region genes (IgVH) is an important prognostic parameter in chronic lymphocytic leukemia (CLL). Unfortunately, no good surrogates for IgVH mutations have as yet been identified. The ZAP-70 gene is overexpressed in a subset of CLL cases, this change correlating with the lack of mutations of IgVH. METHODS: To probe the suggestive link between ZAP-70 expression and IgVH mutations, ZAP-70 was analyzed in different cell lines and in 56 CLL pacients using flow cytometry, Western Blot, and/or immunohistochemistry methods. The results were correlated with the IgVH mutational status and patients outcome. RESULTS: Using flow cytometry ZAP-70 expression was higher in IgVH unmutated CLL (n=35) (48 percent of cells ± 21 percent) than in mutated cells (n=21) (5.7 percent of cells ± 3.8 percent). All CLL patients with ZAP-70 expression > 20 percent (n=32) lacked IgVH mutations, whereas 21/24 CLL with ZAP-70 < 20 percent exhibited IgVH mutations. Finally, ZAP-70 expression had prognostic significance for progression and survival in Binet A cases. CONCLUSIONS: ZAP-70 expression by flow cytometry correlated with the IgVH mutational status and had prognostic significance in CLL patients. Therefore, ZAP-70 analysis can be considered a reliable surrogate for the IgVH mutational status in CLL and a useful tool for assessing prognosis in this disease. PURPOSE: ZAP-70 gene is normally expressed in T and NK cells, where is required for the T-cell receptor signaling. It has been described that ZAP-70 contributes to the B-cell development at early stages of B-cell differentiation in mice. The purpose was to investigate the presence of ZAP-70 in normal pro/pre B-cells and mature B-cells, and in tumoral cells from B-acute lymphoblastic leukemias (B-ALLs). EXPERIMENTAL DESIGN: ZAP-70 expression was ascertained by flow cytometry, immunofluorescence, Western blot, and quantitative RT-PCR. Analysis of ZAP-70 and other signalling proteins of the pre-TCR/TCR was performed by Western Blot. RESULTS: ZAP-70 was expressed in pro/pre B-cells, but not in normal mature B-cells derived from bone marrow, peripheral blood or tonsil. Among tumoral cells, ZAP-70 was expressed in 56% of B-ALLs with pro/pre B-cell phenotype and in 4/6 Burkitt/ALL lymphomas. Moreover, other elements of the pre-TCR/TCR signaling pathway, like LAT and Lck, were also found in B-ALL cells. CONCLUSIONS: Amongst normal B-cell subsets, ZAP-70 was found expressed in normal pro/pre B-cells, but not in a significant proportion of normal B-cells with mature phenotype. Moreover, the presence of ZAP-70 in B-ALLs probably reflects their cellular origin. The lack of ZAP-70 expression in normal mature B-cells suggests that its expression in mature-derived neoplasms with different cellular origin, such as Burkitts lymphoma and chronic lymphocytic leukemia, might be due to an aberrant phenomenon.
Advisor:Montserrat Costa, Emilio; Bosch Alavedra, Francesc
School:Universitat de Barcelona
Source Type:Master's Thesis
Date of Publication:06/23/2006