Does Immune Suppression in the Pre-malignant Microenvironment of Colorectal Neoplastic Lesions Associate with Development of Metachronous Polyp and Cancer Risk?

Early detection and removal of colorectal neoplastic lesions, such as adenomas and serrated polyps, is beneficial in lowering incident and mortality of colorectal cancer (CRC). Up to 50% of patients develop metachronous lesions and/or CRC. Therefore, predicting cases at higher risk of developing future lesions is key to optimising overall clinical outcomes. While immune suppression is well established as a mechanism of cancer progression in the advanced stages, its involvement in pre-malignant neoplastic lesions is largely unknown. In this study, we have investigated whether immune suppression in the pre-malignant colorectal neoplastic tissues could influence metachronous polyp and cancer risk. Tissue microarrays containing index polyps from 338 patients collected under the Integrated Technologies for Improved Polyp Surveillance (INCISE) project (West of Scotland Research Ethics Committee 22/WS/0020) were subjected to multiplex immunofluorescence staining with CD3, CD8, FOXP3, CD68, αSMA and Pan-cytokeratin antibodies using Opal fluorophores. Images were obtained by Phenoimager-HT (Akoya Biosciences), undergone spectral unmixing by InForm and analysed by QuPath using its machine learning modalities. T lymphocytes were observed in both epithelial and stromal compartments of the polyps. The majority of CD68+ macrophages and aSMA+ fibroblasts were in the stroma, however, some of the macrophages were found at the epithelial interface. Isolated aSMA+ signals were occasionally observed in the epithelium. A higher level of CD3+CD8+ T cells were associated with a lower risk of metachronous polyp within 6 years (p=0.007 stroma, p=0.011 epithelium), while that of CD3+FOXP3+ showed a higher risk (p=0.031 stroma, p=0.030 epithelium). The results indicate that pre-malignant neoplastic colorectal lesions can be immune suppressed by infiltration of CD3+FOXP3+ T cells, and that such status could be useful in risk predication at the point of the index polypectomy.