Abstract B104: Establishing patient derived organoids for high-grade serous ovarian cancer as representative models for pre-clinical research

Abstract Background: Patient derived organoids (PDOs) are in increasing use as pre-clinical models for high-grade serous ovarian cancer (HGSOC) and other solid malignancies given their proven phenotypic and genotypic similarities with in vivo tumor. Furthermore, their use as putative predictive biomarkers in clinical trials is being explored. We sought to characterize the extent of inter- and interpatient heterogeneity in PDOs from multiple sites in HGSOC patients undergoing primary cytoreductive surgery. Methods: Multi-site samples from within the peritoneal cavity were obtained from HGSOC patients undergoing primary cytoreductive surgery and processed for PDO growth. PDOs were grown using pre-existing published protocols with/without supplementation of the Wnt agonist R-spondin. Once established, PDOs responses to conventional and targeted therapeutics using IC50 and AUC were assessed. RNA sequencing was also performed to characterize transcriptomic differences between PDOs. Results: PDOs were cultured from multi-site samples (mean n=7) from 16 patients using freshly dissociated tumor cells or from viably frozen tissue, banked at time of surgery. PDOs were successfully established (≥5 passages) in 9/16 cases (56%). PDOs from 7 lines immortalized including 3 from different anatomical sites from the same patient. Significant inter-tumoral heterogeneity was observed with large variations in IC50 and AUC values for platinum compounds and PARP inhibitors seen between patients. Intra-tumoral variation was also observed with large variations demonstrated between different sites from the same patient. For example, cisplatin sensitivity varied up to 20-fold across 8 different patient PDO lines as an indication of intertumoral heterogeneity (p0. 0001). Carboplatin sensitivity varied by almost 10-fold between anatomical sites in one same case demonstrating intratumoral heterogeneity (p0. 0001). Variability in Rucaparib sensitivity was also demonstrated, with responses differing between patient cases and also between sites from the same case (p0. 001). Dependence on R-spondin media supplementation for growth was variable and influenced treatment sensitivity in one case. Treatment resistance was induced in 2 PDO lines following growth in low drug-dose conditions, with increments in AUC observed for cisplatin (p0. 01) and rucaparib (p0. 05) compared to matched vehicle controls in separate PDO lines. Differences in gene expression were observed between treatment categories. Conclusion: HGSOC is a genomically unstable and heterogenous tumor type and the extent of intra-patient heterogeneity observed is a likely contributory factor to the high rates of treatment resistance and relapse observed in the clinical setting. PDOs provide a reliable and medium-high throughput model for drug screening to model treatment responses and enable characterization of inter and intra patient heterogeneity ex vivo. Citation Format: James J. Clark, Jon Krell, Catriona Dickie, Lydia Kondyliou, Marc Lorentzen, Mark Lythgoe, Sofia Miron-Barroso, Lucy Gater, Rugile Januskeviciute, Christina Fotopoulou, Paula Cunnea. Establishing patient derived organoids for high-grade serous ovarian cancer as representative models for pre-clinical research 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 B104.