Abstract
Colorectal cancer (CRC) is a devastating disease, ranking as the second leading cause of cancer-related deaths worldwide. Immune checkpoint inhibitors (ICIs) have emerged as promising treatments; however, their efficacy is largely restricted to a subgroup of microsatellite instable (MSI) CRCs. In contrast, microsatellite stable (MSS) CRCs, which account for the majority of cases, exhibit variable and generally weaker response to ICIs, with only a subset demonstrating exceptional responsiveness. Identifying novel cancer-specific tissue (CST) markers predictive of immunotherapy response is crucial for refining patient selection and overcoming treatment resistance. In this study, we developed clinically relevant CRC organoids and autologous immune system interaction platforms to model ICI response. We conducted a comprehensive molecular characterization of both responder and non-responder models, identifying CST markers that predict ICI response. Validation of these findings was performed using an independent cohort of patient specimens through multiplex immunofluorescence. Furthermore, we demonstrated that knocking out a key gene from the identified predictive signature in resistant organoids restored immune sensitivity and induced T-cell-mediated apoptosis. Overall, our results provide novel insights into the mechanisms underlying immunotherapy resistance and suggest new markers for enhancing patient selection. These findings may pave the way for new therapeutic options in MSS patients, potentially broadening the cohort of individuals eligible for immunotherapy.