Abstract B014: Patient-derived organoid models for drug screening in molecular subtypes of endometrial cancer

Abstract Introduction: The lack of reliable pre-clinical models has significantly impeded the progress of drug discovery for specific molecular subtypes of endometrial cancer. This study aimed to develop patient-derived organoid models for use in preclinical screening of novel and repurposed therapies in endometrial cancer molecular subtypes. Method: Endometrial cancer tissue (n=27) and ascites fluid (n=1) were collected for this study (ethics approval SESLHD HREC 2021ETH11975 and 19/001) from patients of various subtypes (17 endometrioid, 3 high grade serous, 2 carcinosarcoma, 2 clear cell, 3 mixed) undergoing treatment at the Royal Hospital for Women and Prince of Wales Private Hospital in Sydney, Australia. Tumor cells were isolated, embedded in 70% Matrigel and cultured in defined culture medium to form organoids. Molecular subtyping of organoids and matched parental tissue was undertaken by mismatch repair (MMR) and p53 immunohistochemistry (IHC), and sequencing of POLE exonuclease domain mutations (EDMs). A unique matched two-dimensional (2D) cell line and three-dimensional (3D) organoid culture derived from ascites isolated from a high grade serous endometrial cancer patient was established. These molecularly stratified pre-clinical models were then used to test drug activity. As a proof of principle, response to paclitaxel and carboplatin was undertaken. Result: 20 organoids representing all major molecular subtypes were established (71% success rate), including one derived from ascites fluid. Organoids are presented with either a cystic or solid structure that highly resembles the morphology of the original tissue. Organoid culture can faithfully retain key features including MMR, p53 status as well as POLE EDMs of the parental tissue. The drug screening results identified contrasting responses of 2D and 3D models obtained from the same patient tissue, highlighting the importance of selecting appropriate pre-clinical models for drug development and testing. Conclusion: This study demonstrated that patient-derived organoids can successfully recapitulate the molecular characterization of endometrial cancer. Molecularly defined organoids represent a promising preclinical resource for drug screening in endometrial cancer. In addition, the model structure should be taken into account while conducting drug screening. Citation Format: Dongli Liu, Elyse Powell, King Man Wan, Ramanand Athavale, Christine Loo, Caroline E. Ford. Patient-derived organoid models for drug screening in molecular subtypes of endometrial cancer abstract. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30 (5Suppl): Abstract nr B014.