Abstract 2079: Collection of patient-derived xenografts (PDX) to study the biology and therapy of bone sarcomas
Authors: Manara Maria Cristina , Nicoletti Giordano , Ferracin Manuela , Cristalli Camilla , Righi Alberto , Magnani Mauro , Pasello Michela , Picci Piero , Nanni Patrizia , Lollini Pier-Luigi , Scotlandi Katia 
Published: August 2018

Abstract
Osteosarcoma (OS) and Ewing's sarcoma (EWS) are the two most common pediatric solid tumors, after brain tumors. Multimodal treatments have significantly improved prognosis in localized disease but outcome is still poor in metastatic patients, for whom therapeutic options are often inadequate. Preclinical drug testing to identify promising treatment options that match the molecular make-up of these tumors is hampered by the lack of appropriate and molecularly well-characterized patient-derived models. To address this need, a panel of patient-derived- xenografts (PDXs) was established by subcutaneous implantation of fresh, surgically resected OS and EWS tumors in NSG mice. Tumors were re-transplanted to next mice generations and fragments were collected for histopathological and molecular characterization. A model was considered established after observing stable histological and molecular features for at least three passages. To evaluate the similarity of the model with primary tumor, we performed a global gene expression profiling and tissue microarrays (TMA), to assess tumor specific biomarkers on tissues from OS/EWS tumors and their PDXs (1st and 3rd passage). Moreover, we verified the feasibility of these models for preclinical drug testing. We implanted 61 OS and 29 EWS samples: 14/38 (37%) primary OS and 9/23 (39%) OS lung metastases successfully engrafted; while among EWS, 5/26 (19%) primary samples and 1/3 (33%) metastases were established. Comparison between patient samples and PDXs, highlighted that histology and genetic characteristics of PDXs were stable and maintained over passages. In particular, correlative analysis between OS and EWS samples and their PDXs was extremely high (Pearson's r range r=0.94-0.96), while patient-derived primary cultures displayed reduced correlation with human samples (r=0.90-0.93), indicating that in vitro adaptation superimpose molecular alterations that create genetic diversion from original tumors. No significant differentially expressed gene profile was observed from the comparison between EWS samples and PDXs (fold change &gt; 2, adjusted p &lt;0.05 at paired t-test). In OS, the comparison between OS patient-derived tumors and PDX indicated differences in 397 genes, mostly belonging to immune system functional category. This is in line with the idea that human immune cells are gradually replaced by murine counterparts upon engraftment in the mouse. As proof-of concept, two EWS PDX and one OS PDX have been treated with conventional and innovated drugs to test their value in terms of drug-sensitivity prediction. Overall, our study indicated that PDX models maintained the histological and genetic markers of the tumor samples and represent reliable models to test sensitivity to novel drug associations. Grants AIRC (IG 18451 to KS; IG15324 to P-LL), Italian Ministry of Health (ER2017 2364984-ERANET. to KS; RF-2013-02357552 to P-LL)
Citation Format: Maria Cristina Manara, Giordano Nicoletti, Manuela Ferracin, Camilla Cristalli, Alberto Righi, Mauro Magnani, Michela Pasello, Piero Picci, Patrizia Nanni, Pier-Luigi Lollini, Katia Scotlandi. Collection of patient-derived xenografts (PDX) to study the biology and therapy of bone sarcomas [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 2079.