Abstract A029: Development of a new iPSC-derived organoid platform to model FTE-derived HGSOC onset and progression

Abstract High Grade Serous Ovarian Cancer (HGSOC) is one of the deadliest and most aggressive types of ovarian cancer. It is characterized by specific genetic mutations, such as in the genes TP53 and BRCA1 and BRCA2, that account, respectively, for 90% and 11-13% of all cases. Also, given its late-stage diagnosis, the mechanisms underlying HGSOC initiation and progression remain elusive. Recently, three-dimensional organoid models derived from human induced pluripotent stem cells (iPSCs) have emerged as a promising new tool for disease modelling. These organoids can be obtained by differentiation into multiple lineages and are capable of recapitulating physiologically relevant processes in vitro. iPSCs engeneering with known genetic mutations can help researchers in understanding how these mutations can contribute to tumor initiation and, possibly, progression. This has been shown for iPSC derived from germline carriers of BRCA1 mutations and differentiated towards the fallopian tube, that were shown to give rise to both serous tubal intraepithelial carcinomas (STICs), pre-neoplastic lesions of HGSOC, and over time full-fledged tumor organoids, that showed response to PARP inhibitor treatment. Here we generalize this experimental framework, aiming at the engineering of iPSC to carry heterozygous inactivating mutations in the TP53 gene by CRISPR/Cas9, since it is mutated in virtually all HGSOC patients, and differentiating pluripotent cells toward FTE organoids. To induce tumorigenesis in the resulting tumor-prone FTE organoids, we will force the system into accumulation of mutations and tumor transformation by the use of radio-mimetics, chemicals that induce DNA double strand breaks. In the context of TP53 deletion, this damage will be tolerated and will lead to progressive transformation of cells. The hypothesis is that over time we will be able to recapitulate molecularly and phenotypically the longitudinal progression of the disease, from normal cells to tumor-prone cells, to STIC and finally HGSOC. To investigate such aspect, we will perform single cell multiomic profiling at each stage of differentiation/tumor progression to define the molecular features associated with this process. We will integrate newly generated data with i) publicly available datasets, that we are aggregating to generate a reference HGSOC atlas; ii) in-house generated single-cell datasets derived from primary FTE and FTE organoids. Then, we will compare tumoroids to both patient-derived organoids and primary HGSOC samples. Finally, we will evaluate whether the transcriptional/genetic profiles of newly generated tumoroids can recapitulate human disease by interrogating public clinically annotated HGSOC cohorts. This study will provide crucial insights into the early molecular events of HGSOC development and the potential of exploiting an archetypic tumoral model of the Fallopian tube for mechanistic studies and target/treatment discovery. Citation Format: Simone Roverselli, Pietro Lo Riso, Marta Sallese, Giuseppe Testa. Development of a new iPSC-derived organoid platform to model FTE-derived HGSOC onset and progression abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr A029.