High CD69 Protein Expression Predicts a Poor Prognosis in B-Cell Chronic Lymphocytic Leukemia (B-CLL).

Abstract

CD69 membrane protein is expressed early in the activation of lymphoid cells and is inducible by B-cells through cross-linking of surface immunoglobulins. Moreover, B-CLL cells exhibit features of activated and of antigen-experienced B lymphocytes overexpressing activation markers such as CD23, CD25, CD69 and CD71 (Damle, 2002). Furthermore, we have demonstrated that ZAP-70+ CLL subgroup shows a rapid disease progression and an inferior overall survival (Del Principe, 2006). The generation of antimurine CD69 monoclonal antibodies able to induce down-modulation or partial depletion of CD69+ cells (Sancho, 2006), prompted us to evaluate the real impact of CD69 expression on B-CLL prognosis. The primary aims of our study were:1.to determine progression-free survival (PFS) and overall survival (OS) upon CD69 expression;2.whether CD69 could predict varied outcome within ZAP-70+ and ZAP-70 negative subgroups; and finally3.whether CD69 was an independent prognostic factor. Therefore, we investigated 247 pts, median age 65 years, 131 males and 116 females.With regard to modified Rai stages, 69 pts had a low stage, 167 an intermediate stage and 11 a high stage. CD69 was determined by multicolor flow cytometry fixing a cut-off value of 30%. CD69+ B-CLL pts were 73/247 (30%). CD69 >30% was significantly associated with an intermediate/high Rai stage (p=0.001), lymphocyte doubling time (LDT) <12 months (p=0.00005) and beta-2 microglobulin >2.2 mg/dl (p=0.002). Lower CD69 expression and IgVH mutated status (>2%) were significantly correlated (73/92; p=0.0003). Furthermore, we found significant associations between lower CD69 and lower CD38 (137/184; p=0.02) or lower ZAP-70 (110/144; p=0.01). Lower levels of soluble CD23 (sCD23) were strongly associated with lower CD69 (127/158; p<0.00001). With regard to clinical outcome, both a significant shorter PFS (Figure) and OS were observed in CD69+ pts (5% vs 56% at 14 years; p<0.00001 and 44% vs 66% at 14 years; p=0.00001) as well as in ZAP-70+ pts (7% vs 62% at 12 years; p<0.00001 and 26% vs 90% at 14 years; p<0.00001). To further explore the prognostic impact of CD69, we investigated its expression within ZAP-70+ (103 pts) and ZAP-70 negative (144 pts) subsets. CD69+ pts showed a shorter PFS both within the ZAP-70+ subset (11% vs 27% at 8 years; p=0.004) and within the ZAP-70 negative subset (21% vs 79% at 12 years, p<0.00001). In multivariate analysis of PFS and OS, in which Rai modified stages, CD38, sCD23, LDT, CD69 and ZAP-70 entered, both ZAP-70 (p=0.0003 and p=0.0002) and CD69 (p=0.005 and p=0.0004) resulted to be independent prognostic factors. Therefore, CD69, determined by flow cytometry, could be considered as a new promising immunologic prognostic parameter in B-CLL. Furthermore, since the ZAP-70 negative subgroup consists of a heterogeneous population presenting variable outcome, CD69 might better stratify B-CLL subsets and early identify progressive pts in order to take timely therapeutic decisions. [Display omitted]