1667P - Multiplexed spatial analysis by imaging mass cytometry to immunologically characterize checkpoint inhibitor colitis

Background

Immune checkpoint inhibitor (ICI) colitis is among the most prevalent immune-related adverse events (irAEs) of immune checkpoint blockade (ICB). Deeper pathophysiological understanding can contribute to evidence-based management of ICI colitis. While single-cell RNA sequencing studies lack tissue architectural insight, we used imaging mass cytometry (IMC) to study ICI colitis spatially in high immunological detail.

Methods

Formalin-fixed paraffin embedded colon biopsies of 18 patients with ICI colitis (4 αCTLA-4, 5 αPD-1, 9 combined [C]ICB) and 5 patients with ulcerative colitis were included. After DAPI imaging of nuclei, IMC was performed on ∼1 mm² regions of stained tissue. Cells were segmented with the MATISSE pipeline combining DAPI and IMC data. We developed a data normalization, data clean-up and supervised cell lineage determination pipeline. To consolidate tissue findings, serum proteomic data (Olink® Target 96 Immuno-Oncology panel) in a partially overlapping cohort of 80 ICB-treated patients, of whom 14 with ICI colitis, were included. All P values are corrected for multiple testing.

Results

CD8⁺ T cells (CD8s) dominated the infiltrate of both αPD-1 and CICB colitis. CICB colitis showed the highest CD8 granzyme B (GzmB) production across groups (P < .01). Considering only the 14 patients with ICI colitis in the proteomics cohort, serum GzmB was also higher in CICB than αPD-1 colitis. A mixed-effects model showed that activated CD8s with CD69^hiCD103^hi tissue resident (T_RM) like phenotype, more abundant in epithelium than lamina propria, mainly explained high GzmB levels in CICB colitis. CTCAE grade colitis had no effect. Within the CD4⁺ pool, we found elevated T_H1/T_H17 balance in CICB vs αCTLA-4 (P = .04), with αPD-1 T_H1/T_H17 balance in between αCTLA-4 and CICB. Consistently, T_H1-associated serum protein levels of IFN-γ, TNF-α, GzmB/H/A and IL12Rβ1 were increased in CICB vs αPD-1 patients with any high-grade irAE (all P < .05).

Conclusions

Our data demonstrate that epithelial cytotoxic CD8⁺ T_RM cells, as well as local T_H1 skewing, are associated with the highest cytotoxicity in CICB colitis. These findings indicate that tissue T_RM cells are direct targets of ICB and play an important role in colitis development.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Dutch Society of Gastroenterology (NVGE; Gastrostart grant).

Disclosure

K.P.M. Suijkerbuijk: Financial Interests, Institutional, Advisory Board: Novartis, BMS, AbbVie, Pierre Fabre, MSD; Financial Interests, Institutional, Invited Speaker: Roche; Financial Interests, Institutional, Research Grant: Novartis, TigaTx. All other authors have declared no conflicts of interest.