The Prognostic Value of Serum APRIL Levels in Patients with Chronic Lymphocytic Leukemia
Authors: Esatoglu Sinem Nihal , Keskin Dilek , Kutnu Muge , Elverdi Tugrul , Salihoglu Ayse , Eskazan Ahmet Emre , AR Muhlis Cem , Ongoren Aydin Seniz , Baslar Zafer , Aydin Yildiz , Uzun Hanife , Soysal Teoman 
Published: October 2019

Abstract
Introduction: Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with variable clinical course. Several studies have been conducted to predict outcome in patients with CLL and also have been going on. A proliferation inducing ligand (APRIL) has been shown to involve in survival and resistance to apoptosis in CLL, and APRIL molecule has been investigated as a prognostic marker in CLL patients. However, there are limited and controversial data regarding APRIL and its impact on prognosis in CLL. We aimed to compare serum APRIL levels in CLL patients with those of age and gender matched healthy subjects, and to investigate the relationship between APRIL and the other common prognostic factors, and to determine whether serum APRIL levels predict time to first treatment in CLL.
Methods: After ethical approval and informed consent were obtained, between May and December 2012, venous blood samples were driven from 96 CLL patients’ and 25 healthy controls’, and serum APRIL levels were measured by ELISA. Demographic data and the prognostic markers were obtained from the patients’ files, and patients have been followed for a minimum of 12 months. We tested the correlation between APRIL with the, clinical and biological parameters, and used the log rank test to compare their Kaplan Meier curves.
Results: Patients were divided into three groups: Treatment naive (group A, n=49), chemotherapy receiving (group B, n=25) and who had previously received chemotherapy (group C, n=22). Median APRIL level was higher in group A (2.78 vs 1.29; p=0.034) and group C (3.54 vs 1.29; p=0.001) when compared to healthy controls, but was not different in group B (1.56 vs 1.29; p=0.3) (Figure 1). Serum APRIL level in group A was negatively correlated with hemoglobin levels (r=-0.298; p=0.037) and platelet counts (r=-0.321; p=0.025) whereas no correlation with age, Rai and Binet stages, lymphocyte counts, β2-microglobulin and CD38 levels were detected. Group A patients were also divided into 2 subgroups (APRIL levels low, n=20 and APRIL levels high, n=29) using median natural logarithm of serum APRIL level as cut off. April low and high subgroups were similar with respect to demographic data and prognostic factors. Median time to first treatment was not reached in the APRIL low group, but was 104 months in the APRIL high group (p=0.13, log-rank test).
Conclusions: Among the treatment naive patients, serum APRIL levels only negatively correlate with hemoglobin levels and platelet counts. These correlations seem to be associated with tumor burden rather than the prognosis, because APRIL levels were not different in chemotherapy receiving patients compared to healthy controls. Since a median survival time could not be reached in the APRIL low group, short follow up time might be an explanation why the APRIL levels did not predict the time to first treatment. In conclusion, our findings let us to think APRIL levels are not a useful marker to predict prognosis in patients with CLL.
Figure 1. Median APRIL levels of CLL patients and healthy controls (ng/mL) Figure 1. Median APRIL levels of CLL patients and healthy controls (ng/mL)

Disclosures
No relevant conflicts of interest to declare.