IHC is not sufficient enough to generate the necessary information from the comprehensive landscape of the TME
When we consider digital pathology applications most of our current knowledge has been gleaned from Immunohistochemistry (IHC). While this technique has helped identify targets and cell types as part of the tumor microenvironment (TME), the data has been limited by laborious protocols to only 1-2 markers. Its become clear that IHC is not sufficient enough to generate the necessary information from the comprehensive landscape of the TME and indeed to date, one has to superimpose multiple slides of data to achieve the level of multiplexing required.
Current clinical stratification for NSCLC immunotherapy regimens requires a positive measurement of tumor cell surface PD-L1 expression and a derived tumor proportion score (TPS) score. However co-localization analysis of the immune checkpoint marker PD-L1 and other immune markers ideally requires the detection of multiple markers on the same tissue slide. The goal of the study was to perform a comparison of DNA-barcoding mIF using Vizgen’s InSituPlex technology and conventional IHC to assess PD-L1 status and other immune cell types in NSCLC tumors
Greater detail and insights into cellular identity and biomarker expression were achieved using mIF
Traditional IHC of PD-L1 was performed using the PD-L1 kit (PD-L1 22C3, Dako) and multiplexed PD-L1 together with expression of CD68, CD8 and PanCK/Sox10 was enabled by the Vizgen FixVUE PD-L1 pre-optimized kit.
Findings from the study demonstrated a high correlation in immune cell densities and TPS between IHC and mIF. However greater detail and insights into cellular identity and biomarker expression were achieved using mIF. Specifically, simultaneous detection of both PD-L1+ and cytokeratin epithelial cell marker+ (CK+) using ISP technology enabled differentiation of PD-L1+ tumor cells from PD-L1+ T cells and PD-L1+ macrophages.
Further, detection of PD-L1+CK+ and CK+ cells permitted calculation of a quantitative rather than a qualitative TPS. Studies also showed that the calculation of TPS using mIF compared favorably to the TPS calculated using IHC and pathologist review.