Identifying and overcoming CAR T cell barriers in the colorectal carcinoma microenvironment

• Applicants: Professor Dr. Christian Buchholz; Privatdozent Dr. Henner Farin
• Subject Area: Gastroenterology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547793263

Microsatellite stable colorectal cancer (CRC) is characterized by low mutational burden and an immunosuppressive tumor microenvironment (TME). This "cold tumor" type is refractory to checkpoint inhibitors and systemic therapy mainly depends on classical radio-/chemotherapy. Cellular immunotherapy using chimeric antigen receptor (CAR)-modified T-cells could improve treatment options for progressed CRC. Patient-derived tumor organoids (PDTOs) recapitulating the molecular and phenotypic characteristics of CRC have previously been used to identify autologous tumor- reactive T cells. However, this strategy has so far only been successful in a small fraction of microsatellite instable cases. In addition, the TME poses a major barrier to effective CAR-T strategies in CRC as in other solid tumors. To obtain a deeper insight into the reactivity of CAR-T cells against CRC, we here propose to investigate immuno-organoid co-cultures. In particular, we will determine how T lymphocytes change when co-cultivated with PDTOs and how other stromal cells such as cancer-associated fibroblasts influence cytotoxic responses. Autologous CAR-T cells will be generated in tumor explants by making use of the applicant’s unique technology to deliver CAR genes selectively into T lymphocytes. We will follow CAR-T activity and PDTO killing and characterize single cell molecular profiles to identify processes that interfere with CAR-T recruitment and activity. To study the spectrum of therapeutic responses and identify resistance phenotypes, we will take advantage of an established CRC organoid biobank and blood from multiple allogenic donors. This way, we will aim to identify potential molecular barriers and in turn overcome these by pharmacologic and/or biologic strategies to improve CAR-T function in the TME.

• DFG Programme: Research Grants