A proliferation-inducing ligand (APRIL) serum levels predict time to first treatment in patients affected by B-cell chronic lymphocytic leukemia

Purpose: A proliferation-inducing ligand (APRIL), a tumor necrosis factor superfamily member involved inB-lymphocytes differentiation and survival, plays a role in protecting B-Cell Chronic lymphocytic leukemia(B-CLL) cells from apoptosis. Having observed that APRIL serum (sAPRIL) levels were higher in B-CLLpatients with CLL at diagnosis as compared to healthy donors (14.61 ± 32.65 vs. 4.19 ± 3.42 ng ⁄ mL;P < 0.001), we tested the correlation existing in these patients between sAPRIL, clinical–biological parametersand disease progression. Experimental design: sAPRIL levels were measured by ELISA in 130patients with B-CLL at diagnosis and in 25 healthy donors. Results: sAPRIL levels did not correlate withgender, age, clinical stage, blood cell counts, b2-microglobulin (b2M) levels, ZAP-70 and CD38 expression.Using median sAPRIL natural logarithm (ln) as cutoff, we distinguished two groups of patients (APRILLOWand APRILHIGH) who were comparable with regard to clinical–biological parameters and overall survival, butdifferent with regard to time to the first treatment (TTFT; P = 0.035). According to univariate analysis, highlymphocyte count, high b2M, Binet stage B–C, ZAP-70 expression and ln(sAPRIL) above median wereassociated with earlier TTFT. Advanced clinical stage, high b2M, ZAP-70 expression and ln(sAPRIL) abovemedian remained independently predictive of shorter TTFT at multivariate analysis. Moreover, sAPRILincreased its prognostic significance when patients were stratified according to independent favorable clinical–biological characteristics (low b2M, stage A and lack of ZAP-70 expression). Conclusions: sAPRIL is anovel indicator of shorter TTFT in B-CLL and a predictor of progression especially in patients otherwiseconsidered at low risk according to validated prognostic factors.