Abstract 4576: 3D in vitro models uncover malignant cell intrinsic and extrinsic mechanisms of CAR-T cell resistance in high grade serous ovarian cancer
Authors: Joy Joash Dominic , Malacrida Beatrice , Laforêts Florian , Kotantaki Panoraia , Maniati Eleni , Hopkins Sarah , Garrobo-Calleja Ianire , Gautrot Julien , Balkwill Frances 
Published: April 2023

Abstract
Chimeric antigen receptor (CAR)-T cell therapies have promising outcomes in hematologic malignancies but limited activity in solid tumors. We used 3-dimentional (3D) in vitro human cell models of increasing complexity to investigate resistance to CAR-T cell therapy in high grade serous ovarian cancer (HGSOC), a disease with poor response to immunotherapy. We identified mucin-1 (MUC1) and TnMUC1 as target antigens in HGSOC omental metastasis and the HGSOC cell lines, OvCAR3 and G164. We then generated CAR-T cells against these targets and tested them in spheroids, collagen gels and microfluidic models. In spheroids, OvCAR3 cells were killed by CAR-T cells whereas, G164 cells were resistant to CAR-T cell cytotoxicity. RNA sequencing suggested that the impaired apoptotic signaling in G164 cells caused malignant cell-intrinsic resistance to CAR-T cell cytotoxicity. Treating G164 spheroids with birinapant, an antagonist of cellular inhibitor of apoptosis protein, induced CAR-T cell cytotoxicity. Moreover, when resistant cells were co-cultured as spheroids with primary omental fibroblasts from ovarian cancer patients, CAR-T cells were activated and cytotoxic. G164 spheroids cultured in fibroblast-conditioned medium also induced CAR-T cell cytotoxicity due to C-C motif chemokine ligand 2 (CCL2) produced by fibroblasts. CCL2 activated CCR2/4+ CAR-T cells to induce cytotoxicity in an antigen-dependent manner. We then investigated CAR-T cell migration and cytotoxicity in malignant cell/fibroblast co-culture collagen gels. CAR-T cell migrated into OvCAR3 gels and were cytotoxic against the malignant cells. However, a dense extracellular matrix (ECM) produced primarily by fibroblasts prevented CAR-T cell migration and cytotoxicity in G164 gels. Treating G164 gels with transforming growth factor beta (TGFβ) receptor inhibitor SB431542 reduced ECM content and altered ECM structure, thus stimulating CAR-T cell penetration and restoring cytotoxicity against G164 cells. We also developed an ovarian cancer-on-a-chip model which involved culturing cell-seeded collagen gels in vascularized tri-channel microfluidic devices. CAR-T cells successfully penetrated and killed malignant cells in co-culture collagen gels when delivered through vascularized microfluidic devices. To our knowledge, this is the first report to use microfluidic tumor models to successfully deliver CAR-T cells. Using these different human 3D in vitro models, we uncovered malignant cell-intrinsic factors and novel mechanisms involving fibroblasts which may influence CAR-T cell activity. Complex human cell models may accelerate preclinical research into CAR-T cell therapies in solid tumors.
Citation Format: Joash Dominic Joy, Beatrice Malacrida, Florian Laforêts, Panoraia Kotantaki, Eleni Maniati, Sarah Hopkins, Ianire Garrobo-Calleja, Julien Gautrot, Frances Balkwill. 3D in vitro models uncover malignant cell intrinsic and extrinsic mechanisms of CAR-T cell resistance in high grade serous ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4576.