PD-L1 expression and CD8 positive lymphocytes in human neoplasms: A tissue microarray study on 11,838 tumor samples

Area of Science:

• Oncology
• Immunology
• Pathology

Background:

• Programmed death ligand 1 (PD-L1) is a key target for immune checkpoint inhibitor therapies.
• Understanding PD-L1 expression across diverse cancer types is crucial for effective treatment strategies.
• Current data on PD-L1 expression patterns in human cancers is not uniform.

Purpose of the Study:

• To comprehensively analyze PD-L1 expression in a large cohort of human tumor types.
• To investigate the relationship between PD-L1 expression and tumor-infiltrating CD8+ lymphocytes.
• To identify specific cancer types with high PD-L1 expression.

Main Methods:

• Immunohistochemical analysis of PD-L1 expression was performed on 11,838 samples.
• The study encompassed 118 distinct human tumor types.
• Statistical analysis examined the correlation between PD-L1 expression and CD8+ lymphocyte infiltration.

Main Results:

• PD-L1 positivity in tumor cells (≥10% cutoff) was observed in 72% of 118 tumor types.
• High PD-L1 expression was noted in thymoma (100%), Hodgkin's lymphoma (93%), and anaplastic thyroid carcinoma (76%).
• PD-L1 was detected in immune cells in 87% of tumor types, with high prevalence in hematopoietic and lymphoid tissues (75-100%).
• PD-L1 positivity significantly correlated with intratumoral CD8+ lymphocytes across numerous cancer types (p<0.0001).

Conclusions:

• PD-L1 expression is prevalent in both tumor and inflammatory cells across a broad spectrum of human cancers.
• The strong correlation between PD-L1 and CD8+ lymphocytes suggests that antitumor immune responses may induce PD-L1 expression.
• These findings have implications for the broader application of PD-L1 targeted immunotherapies.