PD-L1 immunohistochemistry assay optimization to provide more comprehensive pathological information in classic...

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Programmed death-ligand 1 (PD-L1) expression is a predictive biomarker for anti-programmed death-1 (PD-1) therapy efficacy in classic Hodgkin lymphoma (CHL).
• Standardization and interpretation of PD-L1 immunohistochemistry (IHC) assays in CHL remain challenging and controversial.
• Optimizing PD-L1 IHC assays is essential for accurate patient stratification and treatment selection.

Purpose of the Study:

• To optimize the PD-L1 immunohistochemistry (IHC) assay for classic Hodgkin lymphoma (CHL).
• To compare the performance of different IHC antibodies and the RNAscope assay for PD-L1 detection in CHL.
• To analyze PD-L1 expression in Hodgkin and Reed-Sternberg (HRS) cells versus immune cells (ICs) and its association with tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs).

Main Methods:

• A tumor tissue microarray from 54 CHL cases was used for assay optimization.
• Three IHC antibodies (405.9A11, SP142, 22C3) were compared semi-quantitatively with the RNAscope assay.
• Expression levels of PD-L1, CD4, CD8, FOXP3, and CD163 were analyzed in HRS cells and various IC subgroups, including TAMs.

Main Results:

• The 405.9A11 antibody demonstrated superior specificity in HRS cells and sensitivity in ICs compared to other antibodies.
• PD-L1 expression was more frequently detected in ICs (85.2%) than in HRS cells (48.1%).
• PD-L1 expression on ICs showed the strongest association with the density of TAMs.

Conclusions:

• The 405.9A11 antibody provides the most reliable PD-L1 expression results in CHL.
• Pathologists should report PD-L1 expression by considering both HRS cell status and the percentage of PD-L1-positive ICs.
• Standardized PD-L1 IHC assays are critical for predicting anti-PD-1 therapy response in CHL.