Abstract 291: Sequential treatment with the Wee1 inhibitor, AZD1775, enhances the effect of trabectedin in the L-sarcomas

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Abstract Soft tissue sarcomas are heterogeneous mesenchymal neoplasms and account for 1% of all cancers in adults. Over 50 sarcomas subtypes have been classified and many have very limited treatment options. Chemotherapies such as doxorubicin, dacarbazine and gemcitabine have had very low response rates. Two of the most common subtypes of sarcomas are liposarcoma and leiomyosarcoma, also referred to as the L-sarcomas. Trabectedin, a marine derived compound from the sea sponge, Ecteinascidia turbinate, has recently been approved for the treatment of L-sarcomas which has shown a modest effect over common therapies. As a DNA damaging agent, we hypothesized that trabectedin would induce a G2 cell cycle arrest and subsequent inhibition of Wee1 would abrogate this cell cycle checkpoint and induce apoptosis. We therefore examined the effects of trabectedin followed by AZD1775, a Wee1 inhibitor, in a panel of 6 sarcoma cell lines including liposarcoma (LS141, DDLS) and leiomyosarcoma (SK-LMS, SK-UT1, SK-UT1b). IC50s concentrations of trabectedin were determined to be between 0.5 to 2nM, while IC50s for AZD1775 were in the range of 100-200 nM. In vitro results have shown an enhanced inhibition of cell viability with combination treatment in all cell lines at concentrations of 1nM trabectedin for 24hrs followed by 100nM AZD1775 for 48hrs. We also examined biochemical effects with sequential drug treatment (24hrs trabectedin followed by 24hrs AZD1775) which presented an increase of cyclin A1 and cyclin B1 indicative of G2 cell cycle arrest along with increase of phospho-H2AX, indicative of DNA damage by trabectedin, while subsequent treatment with the Wee1 inhibitor showed decrease of phosphorylation of CDC2 (Tyr15). Flow cytometric analysis indicated G2/M cell cycle arrest with trabectedin and abrogation of G2/M with AZD1775. These observations correlated with enhanced apoptosis as measured by biochemical PARP cleavage and DNA content (sub-G1 population). Taken together these results provide a foundation for the development of the sequential treatment of trabectedin followed by the Wee1 inhibitor, AZD775, in the L-sarcomas. Citation Format: Elgilda Musi, Grazia Ambrosini, Gary K. Schwartz. Sequential treatment with the Wee1 inhibitor, AZD1775, enhances the effect of trabectedin in the L-sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 291. doi:10.1158/1538-7445.AM2017-291