Identification of selective inhibitors of dedifferentiated liposarcoma cells by high-throughput screening (HTS).

Abstract

10005 Background: Current chemotherapy for dedifferentiated liposarcoma (DDLS) is largely ineffective demanding a need for new therapeutics. An HTS was performed to discover compounds that selectively promote differentiation and cytotoxicity in DDLS cells but not in adipose-derived stem cells (ASC). Methods: A 3,119 molecule HTS was performed using two DDLS cell lines (DDLS8817 and LPS141) and ASC. Cells were incubated with 10uM of compounds and immunofluorescently stained with C/EBPα and Hoechst nuclear stain to quantify differentiation and cytotoxicity. Images were analyzed by laser confocal microscopy. Hits for C/EBPα were validated by immunoblotting. CyQuant proliferation and annexin V staining confirmed cytotoxicity. SCID mice were transplanted with DDLS tumor (BWH) and treated with adriamycin 0.9mg/kg daily or emetine 20mg/kg biweekly. Results: 48 of 3,119 compounds (2%) were positive for C/EBPα induction in both DDLS lines but not in ASC. 32 compounds (1%) were selectively cytotoxic to DDLS lines. 16 compounds, including deguelin and emetine, were selective C/EBPα inducers and cytotoxic. Immunoblotting confirmed increased C/EBPα expression in treated cells (100nM emetine, 4uM deguelin) compared to untreated controls. Emetine completely inhibited proliferation in DDLS lines. Deguelin decreased proliferation by 24% in DDLS8817 (p<0.05) and 48% in LPS141 (p<0.05). ASC treated with deguelin or emetine had no significant change in proliferation. Emetine increased apoptosis 2-fold and 3.4-fold (p<0.05), while deguelin increased apoptosis 1.1-fold and 4.8-fold (p<0.05) compared to controls in DDLS8817 and LPS141. BWH mice treated with emetine had a 49% reduction in tumor growth compared to untreated controls, yet adriamycin only had an 18% reduction. Conclusions: A chemical screen was used to discover compounds that induce differentiation and show selective cytotoxicity for DDLS cells. Emetine inhibits proliferation and induces apoptosis at nM concentrations and inhibits tumor growth in vivo more than adriamycin, a commonly used LS chemotherapeutic. These results show the promise of this approach for the discovery of novel differentiation-based agents for the treatment of DDLS. No significant financial relationships to disclose.