Comparison of chronic lymphocytic
leukemia patients expressing high or low level of ZAP70 mRNA: new
prognostic factors differences in microRNA expression and interaction
with the microenvironment
Stamatopoulos B, Haibe-Kains B, Equeter C, Debruyn C, Meuleman M, Hanosset D, Sorree A, Bron D, Martiat M, Lagneaux L
Zeta-associated protein 70
(ZAP70) is a prognostic factor in B chronic lymphocytic leukemia
(B-CLL) and a powerful surrogate marker for the immunoglobulin VH gene
(IgVH) status. In this study, we used gene expression profile to
identify genes associated with clinical disparity in CLL patients
expressing high versus low ZAP70 mRNA measured by quantitative real
time PCR (qPCR). Using Affymetrix GeneChip® Human Genome U133 Plus 2.0
Array, two groups of 7 patients selected for either high and low ZAP70
mRNA expression in purified CD19+ cells were compared. Selected genes
were verified by qPCR in an extended patient cohort (n=85) with a
median follow-up of 74 months. 27 genes were differentially expressed
with a FDR<10% and several genes were significant predictors of
treatment-free (TFS) and/or overall (OS) survival. Of these, ITGA4,
PDE8A, and FCRL genes were selected for further analysis. PDE8A and
FCRL family genes were downregulated in ZAP70 positive patients and can
predict TFS and OS. ITGA4 mRNA was upregulated in ZAP70 positive
patients and can significantly predict OS. Moreover this gene is known
to be implicated in adhesion to fibronectin and in the migration.
Therefore, we investigated and demonstrated the adhesion/migration
capacities of ZAP70 positive cells into a stromal microenvironment or
in response to conditioned medium. Finally, in order to complete this
RNA study, we investigated the differential expression of some microRNA
between ZAP70 positive and negative patients and found that miR-29c and
miR-223 had an individual prognostic power. In conclusion, this study
identifies new prognostic factors (genes and microRNA) and shows
clearly the better adhesion and migratory capacities of ZAP70 positive
cells in their microenvironment explaining their better survival and
the aggressiveness of the disease.