Understanding the tumour immune microenvironment of stage III colorectal cancer using multiplexed imaging mass cytometry

Background/Aim: The tumour immune microenvironment is spatially heterogenous and plays a crucial role in cancer progression and response to therapy. Current histopathological examination cannot comprehensively assess the molecular heterogeneity in the tumour microenvironment. We aim to capture tissue morphology and single cell protein expression of cancer and immune cells within intact tissue sections of stage III colorectal tumours from 11 patients. Methods: Using Hyperion Image Mass Cytometry (IMC), we simultaneously profiled 16 protein markers from FFPE samples, including cancer (Ki-67, p53) and immune (CD3, CD4, CD8a, CD45RO, CD20, CD68, Granzyme B) cell markers. We integrated this with matched histopathological imaging and whole-exome-sequencing data. Results: We identified seven cancer, immune and stromal cell types and preserved their spatial organisation within the microenvironment. These cell types were validated on matched H&E histopathology. We found significant interactions of cancer cells with NK-cells and B-cells. Furthermore, we found that tumours with 17p deletion had significantly fewer NK-cells. Conclusion: Using IMC to acquire rich spatial data at single-cell resolution enabled us to assess the heterogeneity of tumour tissue by defining cell types, immune infiltration, and cancer-immune cell interaction within intact tissue sections. Integration of this data with H&E images could assist pathologists in cancer diagnosis.