Abstract A063: Multidimensional cytometric analysis of colorectal cancer reveals novel and diverse mediators of antitumor immunity

Abstract Checkpoint blockade has revived the potential of immunotherapy for cancer treatment. For optimal application and development of cancer immunotherapies, a comprehensive understanding of the antitumor immune response is required. We unraveled local and systemic immune profiles of colorectal cancer by multidimensional mass cytometric analysis of 36 immune cell markers at the single-cell level in tumor tissues, tumor-associated lymph nodes, adjacent normal mucosa, and peripheral blood samples from CRC patients. We identified 218 phenotypically distinct immune cell clusters, including a previously neglected innate lymphoid cell (CD7+CD3-CD127-CD45RO+CD56+) population with cytotoxic potential. This subset demonstrated a tissue-resident (CD69+, CD103+) phenotype, and was most abundant in the immunogenic mismatch repair deficient (MMRd) cancers. Furthermore, tumor-resident immune cell populations were identified across the adaptive (CD4+ and CD8+) and innate (gammadelta) T-cell compartments showing a highly similar activated (HLA-DR+, CD38+, PD-1+) phenotype. PD-1 intermediate and PD-1 high CD8+ T-cell subsets represented distinct states of T-cell activation that further discriminated immunogenic from non-immunogenic colorectal cancers. Remarkably, activated gammadelta T-cells were specific for MMRd cancers, and their potential role in the response to PD-1 checkpoint blockade requires further clarification. The nonactivated counterparts of the tumor-resident CD103+PD-1+ cytotoxic and gammadelta T-cells were present in both tumor and healthy colorectal tissues. We did not detect any of the aforementioned tumor-resident immune cell populations in lymph node samples, with the exception of a tumor-positive lymph node. This indicates that the critical immune cell populations with antitumor activity reside in the colorectal mucosa, and that the role of lymph nodes in the antitumor immune response should be revisited. Finally, by applying imaging mass cytometry we demonstrated that the cytotoxic anti-tumor response in colorectal cancer is highly diverse and not restricted to cytotoxic T-cells, which opens new avenues for the management of this disease.The findings presented here advance the paradigm of antitumor immunity in colorectal cancer and provide a blueprint for the detailed characterization of the involved immune cell subsets. The coordinated action of innate and adaptive immune cell populations suggests a multitargeted exploitation of their antitumor properties in a therapeutic setting. Citation Format: Noel F. de Miranda, Natasja L. de Vries, Vincent van Unen, Tamim Abdelaal, Marieke E. Ijsselsteijn, Ruud van der Breggen, Arantza Farina-Sarasqueta, Koen C.M.J. Peeters, Thomas Höllt, Boudewijn P.F. Lelieveldt, Frits Koning. Multidimensional cytometric analysis of colorectal cancer reveals novel and diverse mediators of antitumor immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A063.