Evaluation of the Expression of Immune Functional Markers in the Tumor Microenvironment

Recent clinical successes with immune checkpoint blockade have provided promising immune-based therapeutic approaches for controlling malignancy. While therapeutic antibodies against CTLA-4 and PD-1/PD-L1 have resulted in potent and durable clinical responses in many patients, there remains an urgent need to develop biomarker assays to identify patients who may benefit from these approaches while avoiding toxicity and without compromising efficacy. While gene and protein expression of immune cell and checkpoint markers can be obtained through traditional techniques, insight regarding spatial and cell-specific expression within the tumor microenvironment is lacking, particularly in regard to secreted proteins with key immune functions. RNAscope™ in situ hybridization assays allow the visualization of single-cell gene expression, targeting mRNA sequences directly in tissues. This approach permits the detection of secreted markers, including cytokines and chemokines.