Abstract for ASH (American Society for Haematology) New Orleans Dec, 2009.
Chosen for an Oral Presentation
Paper #22102
Role of Selectins in the Pathogenesis of Multiple Myeloma
Abdel Kareem Azab, BPharm, PhD1, Phong Quang2*, Feda Azab, BPharm2*, Costas M
Pitsillides3*, John T Patton4*, Theodore Smith5*, Arun Sarkar4*, Judith M. Runnels, PhD1, Aldo
M. Roccaro, MD, PhD2, Antonio Sacco6*, Hai T. Ngo2*, Molly R Melhem2*, Patricia Maiso,
PhD7*, Kenneth C. Anderson, MD6, Charles P. Lin, PhD8*, John L. Magnani4* and Irene M.
Ghobrial, M.D.2
1
Medical Oncology, Dana-Farber Cancer Inst., Boston, MA; 2Medical Oncology, Dana-Farber
Cancer Institute, Boston, MA; 3Wellman Center for Photomedicine, Massachusetts General
Hospital, Boston, MA; 4GlycoMimetics, Inc, Gaithersburg, MD; 5GlycoMimetics, Inc.,
Gaithersburg, MD; 6Dana-Farber Cancer Institute, Boston, MA; 7Medical Oncology, Dana
Farber Cancer Institute, Boston, MA; 8Advanced Microscopy Program, Center for Systems
Biology and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA
INTRODUCTION: Multiple Myeloma (MM) is characterized by widespread disease at diagnosis with the
presence of multiple lytic lesions and disseminated involvement of the bone marrow (BM), implying that
the progression of MM involves a continuous re-circulation of the MM cells in the peripheral blood and
re-entrance into the BM. Selectins are adhesion molecules expressed by activated endothelium of
venules and leukocytes, and are involved in the primary interaction of lymphocytes with the
endothelium of blood vessels. The binding of selectins serves as a biologic brake, making leukocyte
quickly decelerate by rolling on endothelial cells, as the first step of extravasation. In this study, we have
investigated the role of selectins and their ligands in the regulation of homing of MM Cells to the BM
and the therapeutic implications of this role. METHODS AND RESULTS: We have used flow cytometry to
characterize the expression of E, L and P-selectins and their ligands on MM cell lines, patient samples
and on plasma cells from normal subjects. We found that all MM cell lines and patient samples showed
high expression of L and P, but little of no E-selectin. While normal plasma cells showed low expression
of all selectins and ligands, a pan-selectin inhibitor GMI-1070 (GlycoMimetics Inc., Gaithersburg, MD)
inhibited the interaction of recombinant selectins with the selectin-ligands on the MM cells in a dose
response manner. We have tested the role of the selectins and their ligands on the adhesion of MM cells
to endothelial cells and found that MM cells adhered preferentially to endothelial cells expressing Pselectin compared to control endothelial cells and endothelial cells expressing E-selectin (p<0.05).
Moreover, we found that blockade of P-selectin on endothelial cells reduced their interaction with MM
cells (p<0.01), while blockade of E and L-selectin did not show any effect. Treating endothelial cells with
GMI-1070 mimicked the effect of blocking P-selectin. Moreover, we found that treating endothelial cells
with the chemokine stroma cell-derived factor-1-alpha (SDF1) increased their expression of P but not E
or L-selectin detected by flow cytometry. Neither the blockade of each of the selectins and their ligands
nor the GMI-1070 inhibited the trans-well chemotaxis of MM cells towards SDF1-alpha. However,
blockade of P-selectin (p<0.001) on endothelial cells by GMI-1070 inhibited the trans-endothelial
chemotaxis of MM cells towards SDF1-alpha. Both adhesion to endothelial cells and activation with
recombinant P-selectin induced phosphorylation of cell adhesion related molecules including FAK, SRC,
Cadherins, Cofilin, AKT and GSK3. GMI-1070 decreased the activation of cell adhesion molecules induced
by both recombinant P-selectin and endothelial cells. Using in vivo flow cytometry we found that both
anti P-selectin antibody and GMI-1070 prevented the extravasation of MM cells out of blood vessels into
the bone marrow in mice. Moreover, we found that, in a co-culture system, endothelial cells protected
MM cells from bortezomib induced apoptosis, an effect which was reversed by using GMI-1070, showing
synergistic effect with bortezomib. CONCLUSION: In summary, we showed that P-selectin ligand is highly
expressed in MM cells compared to normal plasma cells, and that it plays a major role in homing of MM
cells to the BM, an effect which was inhibited by the pan-selectin inhibitor GMI-1070. This provides a
basis for testing the effect of selectin inhibition on tumor initiation and tumor response to therapeutic
agents such as bortezomib. Moreover, it provides a basis for future clinical trials for prevention of MM
metastasis and increasing efficacy of existing therapies by using selectin inhibitors for the treatment of
myeloma.