Po-309 Characterisation of the immune microenvironment of colorectal cancer using a novel high-plex protein analysis technology

Abstract

IntroductionSpatial characterisation of the immune microenvironment within tumours enables a better understanding of immunology and oncology. However, it has proven difficult to perform such studies in a highly multiplexed manner using limited samples. To address this unmet need, we have developed an imaging and tissue-sampling platform designed to simultaneously analyse up to hundreds of tumour and immune proteins in a single FFPE tissue section with spatial resolution. This novel technology, called Digital Spatial Profiling (DSP) was applied to the characterisation of the therapeutic response of colorectal cancer patients to immunotherapy.Material and methodsFFPE colorectal tumour specimens were subjected to DSP to determine the spatial expression of 30+immune related proteins. Following antigen retrieval, sections were stained with a cocktail of 30+DNA barcoded antibodies in combination with fluorescently labelled antibodies which were used to define the immune-enriched regions of the tumour. Using the fluorescent signal as a guide, regions of interest (ROI) were delineated followed by UV excitation of the defined ROI’s, which releases the antibody-bound DNA barcodes for downstream quantitation on the NanoString nCounter technology.Results and discussionsComparing colorectal tumours characterised by Microsatellite stable (MSS), DSP was able to differentiate immune hot and cold tumours despite MSS status. Since there is a subset of patients with MSS colorectal cancer that still responds to immunotherapy, this suggests DSP could ultimately be used to identify unique spatial biology and immune characteristics that might further expand beyond MSS and MSI status to help predict patients‘ response to therapy.ConclusionUsing this novel approach, we demonstrate multiplexed protein analysis of defined micro-regions within a tumour enabling systematic interrogation of the immune microenvironment within the tumour. We demonstrate the ability of this technology to reveal immune biology that can point to novel biomarkers or therapeutic targets.