The tumour microenvironment is an integrated network of various cell types including cancer, stromal, vascular, and immune cells. Tumor cells display aberrant cell growth and signaling patterns to create an environment that favors evasion of the immune system. Such permissive conditions are required for tumor growth, angiogenesis, progression, and metastasis, and immense efforts are underway to understand and counteract these adaptations. However, the complex interplay between cells makes the tumor microenvironment a particularly difficult area of investigation that requires advanced tools for deeper analysis.
Solid tumours are infiltrated by many different types of immune cells; especially the collected tumour infiltrating lymphocytes (TILs). This group includes both mononuclear and polymorphonuclear immune cells, (i.e., CD8+ T cells, B cells, natural killer cells, macrophages, neutrophils, dendritic cells, mast cells, eosinophils, basophils, etc.) in variable proportions. Their abundance varies with tumor type and stage and the presence of lymphocytes in tumors is often associated with better clinical outcomes. Conversely, tumours also contain many different cell types that suppress the anti-tumour immune response. Many cell types are thought to contribute to the generation of an immunosuppressive tumor microenvironment including cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), mesenchymal stem cells, vascular endothelial cells, and lymphatic endothelial cells.
Researchers are increasingly turning to techniques that allow visualization of cell types and states in a highly specific and sensitive manner, at the single-cell level and in an intact environment in order to provide morphological context. The RNAscope assay, from ACDbio and In Vitro Technologies, is a valuable approach to visualize and evaluate various cell types and states present in the local tumor environment by detecting key functional molecules such as cytokines and chemokines in addition to cell lineage markers. The RNAscope technology enables rapid and efficient detection of co-expression profiles of any target mRNAs, including checkpoint and cell-specific markers, with single-molecule sensitivity and high specificity in formalin-fixed paraffin-embedded (FFPE) tissues.
The RNAscope assay delivers quantitative, sensitive and specific molecular detection of RNA species on a cell-by-cell basis with morphological context in a robust assay. This enables researchers to visualize which genes are expressed, localize where they are expressed, and quantify the level of expression down to a single transcript of RNA. It is also possible to perform simultaneous detection of target RNA and protein (dual ISH-IHC). This opens up powerful avenues of analysis such as identifying a secreted protein and its cell or origin, or uncovering differential regulation of transcription and translation.
Watch the webinar on "Characterization of immune checkpoint expression & infiltrating immune cells in TME by RNAscope ISH".
Watch the webinar on "Surveying expression of immune checkpoint markers in the tissue microenvironment".
Click on the images below to find out more about other immune cell types.