High CD49d Protein Expression Predicts Short Overall Survival and Early Progression in Chronic Lymphocytic Leukemia Patients.

B-cell chronic lymphocytic leukemia (CLL) is a heterogeneous disease with highly variable clinical courses which can be at least in part foreseen by investigating the expression of known prognosticators, including the IGHV gene mutational status or CD38/ZAP-70 expression. By analysing the coordinated expression of several surface antigens in a series of CLL with known clinical courses, we identified the simultaneous over-expression of CD38 and CD49d as part of the signature characterizing the subgroup with the worst outcome. The aim of the present study was to investigate the relationship between CD49d and other well-established biologic prognosticators (CD38 and ZAP-70 expression, IGHV gene mutational status), or markers of tumor burden (Rai clinical stage, beta2-M, sCD23), and to define the independent prognostic impact of CD49d in predicting overall survival (OS) and disease progression (evaluated as time-to-treatment, TTT) in CLL patients. The study includes samples from 303 patients affected by CLL according to the current diagnostic criteria (median age: 63.5 years, range 32–97). The entire cohort of patients was utilized to investigate the impact of CD49d and other prognosticators (CD38, ZAP-70, IGHV gene mutational status) on OS. TTT information and additional laboratory parameters (beta2-M, sCD23) were available for 232/303 patients, whose therapies were established according to NCI-WG criteria. CD49d expression was determined by three-color flow cytometry combining anti-CD49d, anti-CD19 and anti-CD5 mAbs; its expression was demonstrated to be stable over-time and the 30% of positive CD5+CD19+CLL cells was chosen as cut-off to discriminate CD49dlow from CD49dhigh cases. CD49d, whose expression was strongly associated with that of CD38 (p=2.2×10exp-16) and ZAP-70 (p=2.6×10exp-5), or with IGHV gene status (p=1.1×10exp-6), was independent predictor for OS (HR=4.39; p=0.0081) along with IGHV status (HR=5.54; p=0.0005) or, if this parameter was omitted, with ZAP-70 (HR=2.90; p=0.0092). CD49d also effectively predicted TTT and refined the prognostic relevance of all the investigated prognosticators. Notably, a CD49dhigh phenotype, while not changing the outcome of good prognosis (ZAP-70low, mutated-IGHV) CLL, was necessary to correctly predict the bad clinical courses of ZAP-70high (HR=3.12; p=0.023) or unmutated-IGHV (HR=2.95; p=0.002) cases. These findings support the introduction of CD49d detection in routine prognostic assessment of CLL patients, and suggest both pathogenetic and therapeutic implications for CD49d expression in CLL, e.g. envisioning the use of a humanized anti-CD49d monoclonal antibody, currently employed in multiple sclerosis (Natalizumab), for selcted CLL patients.