Background:Multiple Myeloma (MM) is a hematologic malignancy involving uncontrolled proliferation of plasma cells and is particularly trophic to bone where it induces osteoclast-mediated bone destruction. Ticagrelor is a platelet inhibitor that blocks P2Y12 receptors and inhibits ENT1-mediated adenosine uptake, thereby increasing extracellular adenosine, which activates P1 receptors. Prior studies demonstrate that ticagrelor increases life span in a murine model of MM via its effect on extracellular adenosine. Prior studies also demonstrate an increase in proliferation, in vitro, and tumor growth, in vivo, of MM cells in the presence of platelet releasate. Ticagrelor blocks in vitro platelet-stimulated myeloma proliferation, suggesting a positive relationship and interaction between active platelets and multiple myeloma. We therefore determined whether the effect of ticagrelor on myeloma cells was mediated by extra-cellular adenosine or/and inhibition of platelet function.

Methods:Human primary myeloma cells (KMS) were incubated with ticagrelor (10-9-10-4 M) in the presence of 5ng/ml IL-6 in the absence/presence of an A2AR antagonist (ZM241385 10-6M) and platelets (1:500 myeloma cell:platelets). In other experiments MM cells were incubated in the presence of platelet releasate, releasate from platelets treated with ticagrelor, or ticagrelor alone. Proliferation was assayed by Cell Titer MTS assay (Promega).

Results: Ticagrelor inhibited MM cell proliferation by 20% (p<0.0001, IC50=0.5µM). This effect was abrogated by ZM241385 (48±6% increased vs. ticagrelor, p<0.0001). Platelet releasate increased MM proliferation by 33±6% (p<0.05) and ticagrelor inhibited the effect of platelet releasate on MM cell proliferation (IC50=0.12µM).

Conclusions:These results suggest that ticagrelor inhibits proliferation of malignant plasma cells by a mechanism dependent on both adenosine A2A and platelet P2Y12 receptors. Moreover, platelet releasate intensifies proliferation, and this effect is reversed when the P2Y12 receptor is blocked by ticagrelor.

Figure 1
Figure 1.
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Figure 2.
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Figure 3.
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Disclosures

Meltzer:NIH: Research Funding; Celgene: Research Funding; AstraZeneca: Research Funding. Mediero:AstraZeneca: Research Funding; Celgene: Research Funding; NIH: Research Funding. Whatling:AstraZeneca: Employment. Berger:Merck: Membership on an entity's Board of Directors or advisory committees; AZ: Research Funding. Cronstein:AstraZeneca: Consultancy, Research Funding; CanFite: Equity Ownership; Gizmo Therapeutics: Consultancy; Eli Lilly & Co.: Consultancy; NIH: Research Funding; Celgene: Research Funding.

Topics:
multiple myeloma, ticagrelor, heart sound p2, adenosine, adenosine receptors, antagonists, bone destruction, hematologic neoplasms, interleukin-6, mohr-tranebjaerg syndrome

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2016 by The American Society of Hematology
2016
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