The CXCR4 antagonist plerixafor enhances the effect of rituximab in diffuse large B-cell lymphoma cell lines.
BACKGROUND
Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease with variable clinical outcome, accounting for at least 25-30 % of adult non-Hodgkin lymphomas. Approximately one third of DLBCL patients are not cured by the currently used treatment regimen, R-CHOP. Hence, new treatment strategies are needed. Antagonizing the CXCR4 receptor might be promising since the CXCR4-CXCL12 axis is implicated in several aspects of tumor pathogenesis as well as in protection from chemotherapeutic response. In Burkitt lymphoma, the CXCR4 antagonist plerixafor has already been shown to enhance the therapeutic effect of rituximab, the immunotherapeutic agent of R-CHOP; but this is yet to be confirmed for DLBCL. We, therefore, investigated the effect of plerixafor on DLBCL cellular response to rituximab.


METHODS
In this in vitro study, human DLBCL cell lines were treated with rituximab and/or plerixafor, concomitantly or in sequence. The trypan blue exclusion method and MTS-based assays were used to evaluate cellular proliferation, whereas flow cytometry was used for assessment of apoptosis status and CXCR4 surface expression level. Linear mixed effects models were used to assess statistical significance.


RESULTS
We observed that simultaneous addition of plerixafor and rituximab resulted in a significant decrease in DLBCL cellular proliferation, compared to monotherapeutic response. The effect was dose-dependent, and concomitant administration was observed to be superior to sequential drug administration. Accordingly, the fraction of apoptotic/dead cells significantly increased following addition of plerixafor to rituximab treatment. Furthermore, exposure of DLBCL cells to plerixafor resulted in a significant decrease in CXCR4 fluorescence intensity.


CONCLUSIONS
Based on our results, implying that the anti-proliferative/pro-apoptotic effect of rituximab on DLBCL cells can be synergistically enhanced by the CXCR4 antagonist plerixafor, addition of plerixafor to the R-CHOP regimen can be suggested to improve treatment outcome for DLBCL patients.
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Linn
L
Reinholdt
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Maria Bach
MB
Laursen
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Clinical Cancer Research Center, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Alexander
A
Schmitz
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Clinical Cancer Research Center, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Julie Støve
JS
Bødker
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Department of Clinical Medicine, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Lasse Hjort
LH
Jakobsen
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Clinical Cancer Research Center, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Department of Clinical Medicine, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Martin
M
Bøgsted
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Clinical Cancer Research Center, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Department of Clinical Medicine, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Hans Erik
HE
Johnsen
Department of Haematology, Aalborg University Hospital, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Clinical Cancer Research Center, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark ; Department of Clinical Medicine, Aalborg University, Sdr Skovvej 15, Aalborg, DK-9000 Denmark.
Karen
K
Dybkær
AMD3100; Anti-CD20 antibody; CXCR4; CXCR4 antagonist; DLBCL; Diffuse large B-cell lymphoma; Drug combination study; Plerixafor; Rituximab; in vitro