Thrombopoietin expression and effects of eltrombopag in prostate, breast, lung, and ovarian solid tumors.

e21084 Background: Eltrombopag is a novel, oral thrombopoietin receptor (TPO-R; MPL) agonist that interacts with the TPO-R on bone marrow progenitors to stimulate megakaryocyte production, thus increasing platelet counts. TPO-R is expressed on lymphoma and leukemia cell lines, but little data are available on TPO-R expression on solid tumors including prostate cancer. The objective of the present study was to assess the effects of eltrombopag and expression of MPL mRNA on a variety of tumor types. Methods: Proliferation was measured by Cell Titer Glo assay on 3 breast, 4 lung, 3 ovarian, and 2 prostate cancer cell lines from the ATCC treated with 0.1–100 μg/mL eltrombopag for up to 72 hours. MPL mRNA expression was determined by microarray analysis and qRT-PCR on patient tumors and normal tissue. Results: Eltrombopag, at clinically achievable concentrations (≥ 4 μg/mL), decreased proliferation of all cancer cell lines (IC50 range of 3.7–49.7 μg/mL). Eltrombopag did not increase proliferation at any eltrom...