Elevated serum BDNF levels are associated with favorable outcome in CLL patients: Possible link to CXCR4 downregulation

Increased chemokine C-X-C receptor 4 (CXCR4) expression is related to unfavorable outcome in chronic lymphocytic leukemia (CLL). Brain-derived neurotrophic factor (BDNF) is a neuronal growth factor that has been shown previously to interact with CXCR4 in neuronal cells. Here, we studied the in vitro effect of BDNF on CXCR4 expression and chemotaxis toward stromal derived factor-1 (SDF-1) in freshly isolated CLL cells. We also explored the correlations between serum BDNF levels in CLL patients and disease characteristics and clinical course. Incubation of CLL cells with recombinant BDNF (50 ng/mL) resulted in a downregulation of CXCR4 surface expression and atenuated chemotaxis toward SDF-1. Higher serum BDNF levels were associated with a mutated immunoglobulin heavy chain variable (IGHV) gene, an early clinical stage, and a stable clinical course. Our findings suggest that increased circulating blood BDNF may be associated with a favorable effect in CLL. However, the exact mechanism of this favorable effect should be investigated further.