(P 54) HIGH-THROUGHPUT DRUG SCREENING IN CHONDROSARCOMA CELLS IDENTIFIES MULTIPLE EFFICIENT ANTINEOPLASTIC AGENTS

Objective: Chondrosarcoma is a rare and heterogeneous group of malignant bone tumors that are characterized by the production of cartilaginous matrix. Conventional chondrosarcoma is generally resistant to traditional chemotherapy and radiotherapy. The mainstay of management for localized disease is surgical resection. Metastatic chondrosarcoma has a dismal prognosis, and to date, there are no proven effective systemic therapies. IDH mutations represent an attractive target for advanced chondrosarcoma, however, early results with IDH inhibitors in IDH-mutant chondrosarcoma are modest. As a means for drug repurposing, in this study, we aimed to identify potential therapeutic compounds for combinational therapy among FDA-approved anti-tumor agents.

Methods: We evaluated the treatment response to a panel of 215 FDA-approved anti-cancer compounds in IDH1-mutant chondrosarcoma cell lines, JJ012 and HT1080, as well as their mutant IDH1 knockout clones by means of a high-throughput drug screening platform. One thousand cells were seeded per well in 384-well micro-titer plates and treated with individual drugs over a 20,000-fold concentration range for 72 hours. Cell viability was assessed by measuring ATP levels via bioluminescence. Interpretation of dose response curve parameters was performed according to the modified drug sensitivity scoring (DSSmod) function. The drug sensitivity results were validated in clonogenic assays. The candidate drugs were further analyzed for cell death and cell cycle effects by flow cytometry.

Results: Top 20 compounds with the highest treatment efficacy were identified based on the DSSmod, and further classified according to their mechanism of action, where available. Treatment with these compounds including antimitotic (docetaxel), antimetabolite (methotrexate), HDAC inhibitor (panobinostat), anthracyclines (idarubicin and doxorubicin), topoisomerase inhibitor (camptothecin), and proteasome inhibitor (pevonedistat) for 72 hours, dramatically reduced cell viability of all tested cell lines in a dose-dependent manner, independent of IDH mutation status. The most potent representatives in each class- docetaxel, methotrexate, panobinostat, idarubicin, camptothecin, and pevonedistat- were selected and further tested for their effect on cell survival in clonogenic assays. When used within the range of their respective IC50s, the six drugs significantly reduced colony formation of the chondrosarcoma cells by 50-90%, compared with vehicle control (p < 0.05). Moreover, we observed that treatment with these drugs for 72 hours induced 2 to 10-fold increase in the number of chondrosarcoma cells undergoing apoptosis and/or cell cycle arrest as compared to vehicle controls (p < 0.05). We are currently evaluating their combinatorial antitumor effects in synergy tests.

Conclusion: We identified several highly effective agents that demonstrated anti-tumor activity in chondrosarcoma cells independent of IDH mutation status. These drugs represent attractive candidates for chondrosarcoma therapy and are worth considering for future preclinical and clinical testing.