Abstract IA001: Patient-derived tumor organoids to probe the cancer immune interface
Authors: Dijkstra Krijn K 
Published: December 2023

Abstract
The development of rational (combination) immunotherapies is limited by an incomplete understanding of what determines a tumor’s sensitivity to immune attack. Despite great heterogeneity in resistance mechanisms between patients, functional model systems to study cancer/immune cell interactions at the level of individual patients have been lacking. Here we highlight the potential of organoid/immune cell co-cultures as individualized models of anti-tumor immunity. First, we established a co-culture platform of autologous tumor organoids and peripheral blood lymphocytes from patients with mismatch-repair deficient colorectal cancer (dMMR-CRC) and non-small-cell lung cancer (NSCLC). This allows enriching tumor-reactive T cells from peripheral blood of individual patients, and creating personalized test systems to evaluate their capacity to kill matched tumor organoids. Second, subclonal immune escape is a major barrier to achieving complete responses to cancer immunotherapies. While most tumours consist of multiple genetically distinct clones, directly investigating the potential for immune escape at the clonal level has been impossible so far, due to challenges in isolating and propagating individual tumour subclones from human cancers for functional studies. By leveraging the multi-region TRACERx study, we established multi-region organoid libraries of &gt;20 parallel sublines from patients with NSCLC. Co-cultures of each subline with autologous tumour infiltrating lymphocytes (TIL) reveal substantial heterogeneity in the capacity of individual clonal sublines to elicit a T-cell response. We show that subclonal immune escape can be mediated by antigen-dependent and -independent mechanisms. These results show (i) that tumour evolution can give rise to distinct cancer clones with intrinsic differences in immune evasion capacity and (ii) provide an approach to prospectively identify and isolate immune evading subclones from cancer patients. Third, analysis of a clinical cohort of patients treated with anti-PD1 therapy revealed that gamma delta T cells are critical mediators of the response in dMMR-CRC patients with genetic inactivation of beta-2-microglobulin (B2M). Co-cultures of organoids and gamma delta T cells provide direct evidence that loss of B2M increases reactivity of patient-derived gamma delta T cells towards tumor organoids. This highlights the need for functional models that move beyond conventional T cells. Future developments are directed towards establishment of complex co-culture systems to study how communication between organoids and immune cells is mediated by cell surface factors and secreted molecules, and how cellular crosstalk is altered in cancer.
Citation Format: Krijn K Dijkstra. Patient-derived tumor organoids to probe the cancer immune interface [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr IA001.