A Clinically Integrated Pediatric Patient-Derived Xenograft Program Enables Evaluation of Cohort and Patient-Specific Biology and Therapeutic Strategies.

Abstract

Preclinical translational research has increasingly utilized patient-derived xenograft (PDX) models for mechanistic and experimental therapeutic studies. However, most existing models have been developed from adult cancer types. Here, we describe the establishment of a PDX program to expand the availability of pediatric-specific PDXs for preclinical research and enable studies of pediatric cancer histologies, including ultra-rare diseases. Processes for PDX generation were integrated into established clinical workflows to facilitate universal model generation. Methodologies for tissue procurement, processing, and cryopreservation were optimized to enable intra- and inter-institutional PDX model generation. Over a 6-year span, 388 PDX tumor models representing >40 diagnoses were generated, including ultra-rare tumors and longitudinal models established from pre-therapy, post-therapy, and relapse tumors from the same patient. Genomic characterization of these PDXs demonstrated excellent concordance and recapitulation of molecular alterations of the source tumor. Successful PDX generation was enhanced from relapsed samples, was higher in sarcomas compared to other solid tumor types, and was a negative prognosticator for clinical outcome. The utility of the broad portfolio of molecularly annotated models for validating cross-histology biomarker-driven therapeutic strategies was established by demonstrating anti-tumor activity of a MAT2A inhibitor in MTAP-deficient PDXs. Universal model creation also allowed for experimental validation of therapeutic hypotheses on a patient-specific basis, as highlighted by the characterization of a RAF1 fusion (EPB41L2::RAF1) in an osteosarcoma PDX. Overall, development of a diverse collection of pediatric PDX models enables hypothesis-driven and cross-histology studies that expand our understanding of cancer biology and aid ongoing drug prioritization efforts in rare tumors.