Abstract 3898: Discovering novel therapies in the treatment of osteosarcoma
Authors: Mehrhoff Casey , Du Yuchen , Xiao Sophie , Byrd Robert , Man Chris Tsz-Kwong , Procissi Daniele , Walterhouse David , Li Xiao Nan 
Published: June 2022

Abstract
Introduction: This research aims to discover novel therapies in the treatment of osteosarcoma (OS). OS is the most common primary bone cancer in pediatrics. 5-year overall survival is around 70% for patients presenting with localized OS, and less than 30% for patients with relapsed or metastatic disease. OS remains difficult to cure in large part due to the heterogenous property of the tumor and high rate of somatic mutations.
Methods: Using high throughput screening (HTS), 320 drugs purchased from Selleck have been tested against 3 OS cell lines - HOS, LM7, and 143B - each of which harbors different mutations seen in OS. The Echo® 650 Series Next Generation Acoustic Liquid Handler is a robotic machine used for HTS. On day -1, cells from each cell line were added to 384 well plates based on calculations from cell line density testing. On day 0, 3 drug concentrations (10uM, 1uM and 0.1uM) for 320 drugs were added to each cell line using the Echo® machine and HTS technology. On day 8, the inhibitory concentration was tested among all cell lines. Our standard for successful cell inhibition included drugs with an inhibitory concentration of ≥98% (IC98) in ≥2 drug concentrations on all 3 cell lines. Additionally, orthotopic xenograft models of immunocompromised mice have been established. 10 OS models have been implanted intratibially in mice from 5 patient samples (3 samples received from consented patients treated at Lurie Children’s Hospital, 2 samples gifted from St. Jude Children’s Research Hospital) and 5 cell lines (gifted from Texas Children’s Hospital).
Results: 32 drugs exhibited an IC98 on at least 1 cell line. 14 of 320 drugs met the inclusion criteria of an IC98 on all 3 cell lines, 10 of the 14 drugs have never been reported as being effective in osteosarcoma cell inhibition. These drugs are: BRL-15572 (dihydrochloride), PH-797804, Apalutamide (ARN-509), AMG-458, Ipatasertib (GDC-0068), Mifepristone, Prucalopride, VU 0361737, Olopatadine HCl, and AZ 3146. Multiple of these agents have proven to be effective in inhibiting other cancer types/solid tumors and will be of interest for in vivo testing. 5 orthotopic xenograft murine models have successfully grown, including 1 patient tumor sample from Lurie, 1 sample from St. Jude, and 3 cell lines. All 5 of the established orthotopic xenograft models have demonstrated metastatic disease to different organs including to the lungs. Tumor growth has been confirmed through gross observation, magnetic resonance imaging, computed tomography and microscopic evaluation.
Conclusion: The in vitro test results are promising and provide the groundwork to proceed with in vivo testing on orthotopic xenograft models. These models will be used for drug testing of the narrowed drug agents, with tumor growth inhibition and survival time of the drug treatment group monitored against a control group without drug exposure. Results from in vivo testing will be proposed for future clinical trials for treating pediatric osteosarcoma.
Citation Format: Casey Mehrhoff, Yuchen Du, Sophie Xiao, Robert Byrd, Chris Tsz-Kwong Man, Daniele Procissi, David Walterhouse, Xiao Nan Li. Discovering novel therapies in the treatment of osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3898.