Abstract LB-167: Novel LSD-1 inhibitor validation in new established clinically PFA patient-derived orthotopic xenograft (PDOX) models of ependymoma (2018)

Abstract Background: Ependymoma (EPN) is one of the most malignant tumors and surgical resection is the mainstay of treatment followed by re-irradiation and chemotherapy. However the benefit of this modality have not been clearly demonstrated. Posterior fossa A (PFA) EPN have the worst prognosis and driven by epigenetic changes, suggesting targeting epigenetic changes in PFA EPN can potentially be effective. The limited availability of a reliable translational platform has hampered efforts to understand tumor biology and the preclinical and clinical trials for EPN. In this study, we established a series of orthotopic EPN xenograft mouse models from fresh surgical specimens. We also examined the therapeutic efficacy of SYC-836, a novel LSD-1 inhibitor developed at Baylor College of Medicine, both in vitro and in vivo in these PDOX models. Material and Methods: Clinically and pathologically available PFA EPN samples were obtained from patients who had treatment in Texas Children's Hospital. Parts of the surgical samples were dissociated into single cells and implanted into the cerebellum of SCID mice (1x105 cells /2 uL FBS). Once tumorigenicity confirmed, xenograft tumor would be serially subtransplanted in mouse brains and be cultured in vitro to develop the permanent cell line. To test if xenograft tumors precisely reflect morphologic and pathologic characteristics of their parental tumors, we compared histology, and several key parameters in invasiveness, growth rate and microvessel density by IHC. To examine in vitro anti-tumor activities, primary cultured cells from an established PDOX model of PFA EPN (4423EPN) were subjected to SYC-836 at various concentrations (0-25uM). Cell viability was measured at 5 different time points over 14 days. To validate the drug's in vivo efficacy, two established PFA EPN PDOX models, 4423EPN and 2002EPN, were utilized. 40 mice per model were implanted and divided into 4 treatment groups: 1) control , 2) radiation/standard therapy (2 Gy XRT x 5 days), 3) SYC-836 only (15mg/kg IP x 28 days), and 4) combination (radiation + SYC-836 per regimen above). Animal survival times were analyzed using log rank analysis. Results: By now we have successfully developed 6 intracerebellum xenografts. It has since been serially subtransplanted in mouse for more than 3 generations and can be cryopreserved for long-term maintenance of tumorigenicity. We showed xenograft tumors precisely replicated morphologic and pathologic characteristics of their parental tumors. SYC-836 demonstrated effective cell killing in vitro in both time- and dose-dependent manner. IC50 was ~7.5uM. In vivo experiment was completed in 2 PFA EPN PDOX models. There were no survival benefit with either XRT only or SYC-836 only compared to control group; however, the combination treatment lead to significant improvement in animal survival. SYC-836 was well tolerated in mice. Conclusion: We have successfully established a series of clinically orthotopic EPN xenograft models and they well-matched with those of parental EPNs both preclinically and clinically. Our data showed that combining SYC-836 with radiation synergistically prolongs animal survival significantly, suggesting that SYC-836 may have a role in the clinical setting by either reducing radiation dosages, or be a potential adjuvant agent to other chemotherapy drugs in treatment for EPN. Citation Format: Huiyuan Zhang, Sibo Zhao, Yuchen Du, Lin Qi, Frank K. Braun, Mari Kogiso, Holly B. Lindsay, Sarah G. Injac, Laszlo Perlaky, Patricia Baxter, Jack M. Su, Xiao-Nan Li. Novel LSD-1 inhibitor validation in new established clinically PFA patient-derived orthotopic xenograft (PDOX) models of ependymoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-167.