Abstract 2483: Generation of patient-specific and genome-edited MEN2A patient-derived induced pluripotent stem cells as novel tools for drug screening

Introduction MEN2A is a cancer-predisposing syndrome that affects patients with germline RET mutations. Animal models do not faithfully recapitulate the full clinical spectrum of the disease. Moreover, it has been suggested that primitive malignant stem cells could be at the origin of resistances and relapses in patients treated with standard chemotherapy. In order to modelling MEN2A malignant primitive stem cells, we have induced to pluripotency MEN2A peripheral blood mononuclear cells from patients who developed medullary thyroid carcinoma harboring “high risk” or “moderate risk” RET mutation. Methods PBMC from patients with germline RETC620R and RetC634Y mutations were reprogrammed into pluripotent stem cells using Sendai-virus mediated Oct4, Sox2, Klf4 and c-Myc gene transfer. An isogenic IPSC line was generated by genome editing, using CRISPR-Cas9 to correct the “high risk” RETC634Y mutation. Hallmarks of pluripotency, genotype and phenotypes were characterized. Results Pluripotency behaviour of each IPSC line was confirmed in vitro (EBs, and pluripotent markers) and in vivo (teratoma assay in immunodeficient mice). Genome edition of the RETC634Y iPSC led to the generation of the RETY634C isogenic control iPSC. Ret expression was confirmed on both RETC634Y and RETY634C. In order to determine the accuracy and absence of off-target effects, we have performed a whole exome sequencing of both RET-mutated and RET-corrected IPSCs. These experiments revealed some off target effects of the CRISPR-mediated gene edition. Gene-array datas revealed an increased expression of neuronal development-related set of genes in RETC634Y iPSC, as compared to RETY634C control, that may account for the development of certain MEN2A features. Treatment of IPSC with vandetanib, a Ret inhibitor, led to a decrease of iPSC colonies formation in RETC634Y mutated iPSC compared to RETY634C, suggesting that RET-iPSC could serve as a plateform drug screening model. The comprehensive pathological assessment of IPSC RET-mutated and corrected derived-teratoma did not reveal, at this point, any neuroendocrine tumor-reminiscent structure. Conclusion We report here the first MEN2A-iPSC from “high risk” RETC634Y iPSC and its genome-edited isogenic normal IPSC, with their genomic profiling by whole exome sequencing. These well caracterized RET-IPSC will allow to develop cell-based assays in high throughput screening for drug discovery and to model MEN2A. Citation Format: Julien Hadoux, Christophe Desterke, Olivier Feraud, Mathieu Guibert, Roberta Francesca De Rose, Paule Opolon, Dominique Divers, Emilie Gobbo, Frank Griscelli, Martin Schlumberger, Annelise Bennaceur-Griscelli, Ali Turhan. Generation of patient-specific and genome-edited MEN2A patient-derived induced pluripotent stem cells as novel tools for drug screening. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2483.