Abstract A26: The successful application of endoscopic ultrasound guided fine needle biopsy to establish pancreatic patient-derived tumor xenografts
Authors: Hermans Els , Merwe Schalk Van der , Depreeuw Jeroen , Dekervel Jeroen , Radaelli Enrico , Topal Baki , Lambrechts Diether , Amant Frédéric 
Published: March 2017

Abstract
Introduction: Pancreatic cancer is one of the most lethal cancer types with an overall 5-year survival rate of less than 5%. The vast majority of the patients are diagnosed late in their disease onset with already locally advanced setting or when metastasized to regional lymph nodes or other organs and are therefore excluded from surgery. Over the last decades no major advances have been made in the treatment of this disease, at least partly due to the lack of preclinical in vivo models reliably recapitulating the clinic. Patient-derived tumor xenografts (PDX) are currently used as reliable preclinical in vivo models to study tumor biology, accelerate biomarker discovery and preclinical drug screening. However, at present, large tumor biopsies obtained by invasive surgical approaches are still a prerequisite to successfully establish pancreatic PDXs thereby limiting this technique to patients that are eligible for surgery. The objective of the study was to establish pancreatic PDXs by transplanting tumor tissue acquired by endoscopic ultrasound (EUS) fine needle biopsies (FNB) and compare them to surgery-derived PDXs. Secondly, we aimed to demonstrate that EUS-derived PDXs of locally advanced or metastatic pancreatic cancer reflect the original tumors, at the histologic and genetic level.
Method: Biopsies of chemo-naive primary pancreatic carcinoma were collected at surgery and EUS. After localization of the tumor using a linear echoendoscope, a FNB on patients (n=10) with suspected malignant pancreas tumor was performed using a 22G needle. Concentration of the EUS-derived FNB occurred by centrifugation of the sample prior to engraftment. Surgical samples (n=4) on confirmed pancreatic adenocarcinoma were obtained at the time of tumor resection. Via a standardized aseptic technique transplantation was performed in nude mice upon propagation. To asses preservation of general tumor morphology and other tumor-specific characteristics as growth pattern and vascular-stromal composition, H&E and immunohistochemistry (cytokeratin-7, human-vimentin, CD31) were performed. To determine conservation of the mutation profile, copy number alterations and transcription profile, whole exome sequencing (WES), whole-genome low-coverage sequencing and RNA sequencing were executed.
Results: Using the adapted protocol of EUS-derived FNB, we achieved an engraftment rate of 60% whereas all surgical samples were successfully transplanted. Despite a decrease in desmoplastic stromal reaction, the general morphology of EUS-derived FNB PDXs, as assessed by histology, was conserved compared to that of the primary tumor. Also at the genetic level, there was no obvious difference compared to surgery-derived xenografts. In particular, despite some heterogeneity, somatic mutation and copy number profiles were largely shared between xenografts regardless of whether they were obtained by EUS or surgery.
Conclusion: We show that it is technically feasible to establish pancreatic PDXs from patients with locally advanced or metastatic disease by a minimal-invasive sampling technique such as EUS FNB. By acquiring a limited amount of tumor tissue, we demonstrated that tumor morphology, differentiation grade and genetic profile are largely maintained across the different passages suggesting that EUS-derived FNB xenografts may be useful to study pancreatic tumor biology and develop novel therapies in this patient population with a high clinical need. In addition, our approach could potentially be translated to establish PDXs in other unresectable tumor types.
Citation Format: Els Hermans, Schalk Van der Merwe, Jeroen Depreeuw, Jeroen Dekervel, Enrico Radaelli, Baki Topal, Diether Lambrechts, Frédéric Amant. The successful application of endoscopic ultrasound guided fine needle biopsy to establish pancreatic patient-derived tumor xenografts. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A26.