Abstract 4248: Patient-derived MTAP-deleted bladder cancer organoid model: A unique platform for drug development
Authors: Schwermann Maximilian , Carneiro Benedito , Lu Shaolei , De Souza Andre , Hadfield Matthew , Mega Anthony , Lagos Galina , Khaleel Sari , Golijanin Dragan , Holder Sheldon , Srinivasan Praveen , MacDonald William , George Andrew , Zhou Lanlan , Zhang Leiqing , El-Deiry Wafik 
Published: March 2024

Abstract
Introduction: Approximately 30% of advanced bladder cancer (BCa) tumors exhibit MTAP gene deletion, which has been associated with luminal subtype BCa, poor response to chemotherapy, and shorter progression to metastatic disease (De Souza 2023). MTAP deletion has been proposed as a potential biomarker for response to pemetrexed and an emerging class of PRMT5 and MAT2A inhibitors in development for MTAP-deleted tumors. Here, we describe the first patient-derived 3D model of BCa with MTAP deletion and its translational potential as a drug sensitivity platform.
Methods: A patient (pt) with metastatic BCa harboring MTAP deletion underwent a pelvic lymph node biopsy. A fresh tumor sample was processed under collagenase/dispase solution for 30 minutes and filtered through a 70-um cell strainer. Cells were cultures in low attachment plates with MammoCult™ Basal Medium (Stem Cell Technologies). After 5 passages and 3D spheroid formation, immunostaining for cytokeratin (CK) 5 and 6, GATA3, CK20, and Ki67 staining were performed to confirm the urothelial origin. The MTAP-del was confirmed by a western blot of the organoid specimen and compared to other BLCa cell lines (UMUC, RT4, J82, and 5637). The viability assays were performed using the CellTiter-Glo® 3D Cell kit. Next-generation sequencing (NGS) of primary BCa tumor revealed deletion of MTAP, CDKN2A, CDKN2B, and mutations in p53, TERT, and KDM6A.
Results: The patient organoid sample was positive for the luminal CK5/6 markers and negative for GATA3. Ki67 and CK20 were primarily expressed in the nucleus of the same sample. The organoid retained morphologic and immunohistochemical features of the patient’s primary bladder tumor, showing the same squamous differentiation and similar Ki-67 proliferative index. The organoid displayed no evidence of the MTAP protein by western blot (similar findings with the MTAP-del cell lines UMUC and RT4). The organoid showed sensitivity to pemetrexed [pemetrexed IC50=0.12 uM (other MTAP-del BLCa IC50: 0.1-0.23 uM)] and resistance to gemcitabine and cisplatin [Gem IC50=55 nM (other BLCa IC50: 1-29 nM), Cis IC50=90.5 uM (other BLCa IC50: 2-17 uM).
Conclusions: We describe the first patient-derived MTAP-deleted BCa organoid recapitulating the features of the primary tumor. The organoid displayed sensitivity to pemetrexed as described with MTAP-deleted BCa. The organoid represents a unique platform for testing novel therapeutic strategies for MTAP-deleted BCa.
Citation Format: Maximilian Schwermann, Benedito Carneiro, Shaolei Lu, Andre De Souza, Matthew Hadfield, Anthony Mega, Galina Lagos, Sari Khaleel, Dragan Golijanin, Sheldon Holder, Praveen Srinivasan, William MacDonald, Andrew George, Lanlan Zhou, Leiqing Zhang, Wafik El-Deiry. Patient-derived MTAP-deleted bladder cancer organoid model: A unique platform for drug development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4248.