Deregulated CXCR4-CXCL12 Signaling Impacts on the Pathogenesis of DLBCL

Introduction:

The interaction of the chemokine receptor CXCR4 and its ligand CXCL12 appears to be implicated in many important biological processes such as proliferation, survival, migration, and/or invasion. Furthermore, it is important for normal leukocyte trafficking. Deregulation of this axis is frequently observed in several hematologic malignancies. In diffuse large B cell lymphomas (DLBCL), the CXCR4-CXCL12 axis is still largely unexplored and published data are contradictive. Hence, we comprehensively studied the CXCR4-CXCL12-axis in our DLBCL cohort as well as the effects of CXCR4 antagonists on lymphoma cell lines in vitro.

Methods:

We determined the CXCR4 and CXCL12 expression levels in NGCB- and GCB-DLBCL consisting of primary and transformed follicular lymphomas (n=77 in total), the corresponding bone marrow samples (n=63) and non-neoplastic germinal center-B cells (GC-B, n=5) serving as non-malignant control. To investigate the effects of CXCR4 antagonists in vitro and their function in regulation of important pathways (JNK, ERK1/2 and NF-κB) known to be involved in lymphomagenesis, we treated lymphoma cell lines with three different CXCR4 antagonists, AMD070, AMD3100 and WK1 (a novel nicotinic acid derivative of AMD070 - synthesized by us), followed by functional assays and gene expression profile.

Results:

CXCR4 was 140-fold higher expressed in DLBCL compared to non-neoplastic GC-B cells. Interestingly, higher CXCR4 expression correlated to a clinically advanced stage, to bone marrow infiltration and worse cancer-specific survival in DLBCL. Further expression analysis by using the corresponding bone marrow biopsies demonstrated that CXCL12 expression correlated to the lymphoma infiltration rate and that CXCR4 expression was reduced in remission under therapy. Moreover, two CXCR4 antagonists - AMD070 and especially WK1 - exerted pro-apoptotic effects on CXCR4 positive lymphoma cells in vitro and induced the expression of certain pro-apoptotic genes in CXCR4 positive cell lines. Remarkably, these effects were more pronounced for the WK1. Finally, WK1 treatment resulted in reduced expression of JNK-, ERK1/2- and NFκB/BCR-target genes.

Conclusion:

Our data demonstrate that the CXCR4-CXCL12 axis is involved in the pathogenesis of DLBCL. Since CXCR4 antagonists exert pro-apoptotic effects and impact lymphoma relevant pathways, they represent interesting molecules to develop novel therapeutic agents.