IL-21 regulates the expression of chemokine genes in B-chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) is a common type of leukemia, characterized by the progressive accumulation of CD5+ “mature” monoclonal B lymphocytes in peripheral blood, bone marrow and lymphoid tissues. Although circulating CLL cells are non-dividing cells, prone to spontaneous apoptosis, their progressive accumulation is the result of a dynamic balance between cell death and proliferation and a high turn-over rate has been related to a poor prognosis. Indeed, CLL cells are protected from apoptosis and proliferate in specific niches within the lymphoid tissues and the bone marrow. CLL cells show variable expression of IL-21R that can be up-regulated by cell activation via CD40. CD40-activated CLL cells phosphorylate STAT-1 and STAT-3 and undergo apoptosis in response to IL-21 stimulation. By gene-expression profiling we found out that IL-21 modulates the expression of several genes including cytokine and chemokine genes and genes involved in cell survival and apoptosis in CD40-activated CLL cells. PBMCs were isolated from heparinized blood obtained from 13 untreated patients diagnosed with CLL on the basis of clinical and immunophenotypic criteria. PBMCs were isolated by Ficoll density gradient centrifugation and characterized by immunofluorescence and FACS analysis. When residual non B-cells exceeded 10%, B cells were enriched by negative selection with antibody-coated magnetic beads (CD2-beads, Dynal, Oslo, Norway) to obtain a >95% pure CD19+/CD5+ B cell population. B-CLL cells were pre-activated on adherent CD40L-transduced L cells for 48-36h and then stimulated with IL-21 or medium only for additional 18h. Total RNA was isolated from samples using TriZol (Invitrogen) reagent.