Effect of eltrombopag on proliferation of solid and hematologic tumor cell lines in vitro

Abstract

14628 Background: Eltrombopag is an oral platelet growth factor in clinical studies to treat thrombocytopenia. It increases platelet production by interacting with the transmembrane domain of the receptor, thereby inducing proliferation and differentiation of cells in the megakaryocytic lineage. TPOR is expressed on the surface of some leukemia and stem cells. The following experiments were conducted to evaluate the effects of eltrombopag on the proliferation of tumor cell lines in vitro. Methods: 10 solid tumor cell lines were examined: non-small cell lung carcinoma (NSCLC) cell lines (A549, EKVX, HOP-62, HOP-92, NCI-H226, NCI-H23, NCI-H322M, NCI-H460, NCI-H522) and the hepatocellular carcinoma cell line, HepG2. 13 cells lines from various AML, CML, and lymphoblastic leukemias included: U937, ML-2, OCI- AML2, OCI-AML3, RPMI-8226, HEL 92.1.7, HL-60, K562, SR, CCRF-CEM, MOLT-4, NOMO-1, OCI-M1. Proliferation was measured by 3H-thymidine incorporation and CellTiter-Glo in the hematologic and solid tumors, respectively. Doxorubicin (Dox) was used as + control in the solid tumors. Myeloid differentiation was assayed by flow cytometry and apoptosis by Annexin V. TPOR mRNA expression was determined by Taqman in 7 cell lines. Results: All solid tumor lines demonstrated decreased proliferation after 72-hour culture w/eltrombopag (IC50=5.7 to 14 ug/mL). However, 3 NSCLC lines were less-responsive to both Dox and eltrombopag. Eltrombopag did not increase proliferation of any of the hematologic cell lines and decreased the proliferation of 11 of the 13 hematologic cell lines, (IC50=5.6 to 15.4 ug/mL). Two cell lines, NOMO-1 and OCI-M1, demonstrated an IC50 >40 ug/mL. Further examination of K562, U937 and OCI-AML3 demonstrated a decrease in total cell number as well as decreased proliferation. Annexin V staining suggests that the cells die by a method other than apoptosis. No change in differentiation was observed after eltrombopag treatment. In the cell lines examined, no relationship between the expression of TPOR mRNA and proliferation IC50 was observed. Conclusion: Eltrombopag did not increase proliferation or differentiation of hematologic tumor cell lines. Eltrombopag caused a dose-dependent decrease in proliferation in most of the 23 solid and hematologic tumor cell lines tested. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration GlaxoSmithKline GlaxoSmithKline GlaxoSmithKline