Abstract LB-32: Patient-derived xenograft (PDX) paraclinical platform to guide precision medicine in urothelial cancer
Authors: Pan Chong-xian , Zhang Hongyong , Tepper Clifford , Ghosh Paramita , Kuslak-Meyer Sheri , Airhart Susie , Gill Parkash , Gandara David , Liu Edison , White Ralph de Vere 
Published: May 2015

Abstract
BACKGROUND: The overall efficiency in personalizing medicine by pairing targeted therapy with specific genomic alterations identified through omics technologies is disappointing as current computational biology methods have difficulty in distinguishing “driver” alterations from “passenger” ones. We have developed PDXs that share essentially the same genetic background as the parental human cancer, and use this platform to screen for most effective drugs and perform mechanistic study of drug resistance in order to guide design of precision medicine in urothelial cancer.
MATERIALS AND METHODS: PDXs were developed by direct implantation of fresh clinical tumor specimens in immunocompromised NSG mice (The Jackson Laboratory, West Sacramento, CA). Whole exome, transcriptome and microRNA sequencing was performed, followed by computational biological analysis to identify druggable genetic alterations that were further validated with immunofluorescence (IF) and immunohistochemical (IHC) staining. Efficacy tests to determine response to treatment by targeted therapy, together with analyses to determine the mechanisms of resistance were performed in NSG mice carrying PDXs.
RESULTS: The engraftment rate of PDX was 41 % (13/42). The fidelity between the PDXs and the parental patient cancers was confirmed with cell morphology, tissue microarray IHC/IF staining and mutation profiles. Cell morphology was maintained during passaging in both the subcutaneous and orthotopic PDXs. All PDXs had multiple druggable genetic alterations. Of the first 8 PDXs, 2 harbored PIK3CA mutations (H1047R at the kinase domain and D549Y at the helical domain); 5 had ERBB2 mRNA overexpression determined by transcriptome sequencing, and protein overexpression (3+ by IHC), and 5 had EphB4 overexpression. sEphB4-HSA is an experimental drug developed by Gill (co-author). In PDXs overexpressing EphB4, blockade of EphB4 with sEphB4-HSA significantly prolonged the progression-free survival (PFS) from 9.5 days in the control group to 16.7 days (p=3.17 X 10e-5). Western blot, IHC, and deep sequencing analyses in PDX tissue specimens collected before/during treatment, and after the development of resistance were used to determine the mechanism of resistance.
CONCLUSION: PDXs can potentially serve as a para-clinical model for drug efficacy screening, study of resistance mechanisms, and drug development.
Citation Format: Chong-xian Pan, Hongyong Zhang, Clifford Tepper, Paramita Ghosh, Sheri Kuslak-Meyer, Susie Airhart, Parkash Gill, David Gandara, Edison Liu, Ralph de Vere White. Patient-derived xenograft (PDX) paraclinical platform to guide precision medicine in urothelial cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-32. doi:10.1158/1538-7445.AM2014-LB-32