Send to

Choose Destination
See comment in PubMed Commons below
Blood. 2008 May 1;111(9):4723-30. doi: 10.1182/blood-2007-07-099531. Epub 2008 Jan 8.

IL-21 mediates apoptosis through up-regulation of the BH3 family member BIM and enhances both direct and antibody-dependent cellular cytotoxicity in primary chronic lymphocytic leukemia cells in vitro.

Author information

  • 1Division of Hematology-Oncology, Department of Medicine, The Ohio State University, Columbus, USA.


Interleukin-21 (IL-21) is a recently identified gamma-chain receptor cytokine family member that promotes B-cell apoptosis as well as activation of innate immune system. Based on this, we hypothesized that IL-21 might enhance the apoptosis induced by fludarabine and rituximab and also play a role in augmenting immune-mediated clearance of the chronic lymphocytic leukemia (CLL) cells. Our studies demonstrate that the majority of CLL patients have surface IL-21 receptor-alpha, and its expression correlates with apoptosis, tyrosine phosphorylation of STAT1, and up-regulation of the proapoptotic BH3 domain protein BIM. IL-21-induced BIM up-regulation is critical for apoptosis because inhibition of BIM expression using small interfering RNA prevented IL-21-induced apoptosis. IL-21 treatment of CLL cells but not normal T cells with fludarabine or rituximab additively enhanced the direct cytotoxic effect of these therapies. In addition to its proapoptotic effect, IL-21 promoted STAT1 and STAT5 phosphorylation in natural killer cells with concurrent enhanced antibody-dependent cellular cytotoxicity against rituximab-coated CLL cells in vitro. These data provide justification for combination studies of IL-21 with fludarabine and rituximab in CLL and suggest that BIM up-regulation might serve as relevant pharmacodynamic end point to measure biologic effect of this cytokine in vivo.

Comment in

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk