Detection of immune cell checkpoint and functional markers in the tumor microenvironment by the RNA in situ hybridization RNAscope® assay

The RNAscope® assay is a unique RNA ISH technology that identifies RNA expression at the single cell level with morphological context. Here we present the use of RNAscope® for the detection of RNA targets in the tumor microenvironment (TME) that are involved in tumor immunology and immunotherapy:

• Checkpoint markers
• Immune cell markers
• Cytokines and chemokines

Detection of these RNA targets with the RNAscope® assay can aid in determining:

• Localization of specific immune cell types (i.e., cytotoxic lymphocytes and regulatory T cells) in the TME
• Spatial relationships between different cell types in the TME
• Characterization of secreted proteins (i.e., cytokines and chemokines)
• Evaluation of immune function in TME beyond enumeration of tumor infiltrating lymphocytes

Introduction

The field of cancer immunotherapy has expanded rapidly in recent years with promising clinical results by immune checkpoint inhibitors and other therapeutic approaches such as cancer vaccines and chimeric antigen receptor (CAR) therapy. Despite the dramatic and durable responses seen in many patients, our understanding of the immune response to cancer is still limited, and we cannot reliably predict who will or will not benefit from these new interventions. To better stratify patients for immunotherapy treatments, the series of events and biomarkers involved in the cancer‑immunity cycle need to be better understand^(1-3). In addition, spatially mapped expression data at the single-cell level is crucial to understanding the cellular organization and cell-to-cell interactions in the tumor and its complex microenvironment (TME).