Expression of PD-L1, PD-L2, and inflammatory gene expression profile in locally advanced head and neck squamous cell carcinoma.

Background: The tumor immune microenvironment in cancer treatment response and resistance is of increasing interest. This retrospective study characterized and investigated programmed death-ligand 1 (PD-L1), PD-L2, and the immune gene expression signature and their association with clinical outcomes in locoregionally advanced head and neck squamous cell carcinoma (LA HNSCC).
Patients and Methods: PD-L1 and PD-L2 expression on tumor and immune-infiltrating cells (positivity defined as combined positive score or immunohistochemistry proportion score >1) and T-cell-inflamed gene expression profile (Tcell _inf GEP) were evaluated in patients with LA HNSCC treated in South Korea from 2000 to 2015. Correlations among the three biomarkers and their associations with overall survival and recurrence-free survival were assessed.
Results: Among 366 patients, 38.8% had human papillomavirus-positive disease. PD-L1-positive, PD-L2-positive, and high Tcell _inf GEP (≤-0.162) status were observed in 83.6%, 85.4%, and 73.2% of patients, respectively; 4.1% were posttreatment samples. Correlation between PD-L1 and PD-L2 scores was moderate (r _Spearman  = 0.50), and each biomarker was slightly less correlated with Tcell _inf GEP (0.41-0.45). PD-L1 expression and high Tcell _inf GEP status were associated with human papillomavirus positivity. Higher levels of all biomarkers were observed in oral cavity and oropharyngeal cancers compared with other HNSCC sites. In a multivariable analysis that simultaneously adjusted for all three biomarkers, only high Tcell _inf GEP was significantly associated with longer overall survival (adjusted hazard ratio, 0.57; 95% confidence interval 0.33-0.98) and recurrence-free survival (adjusted hazard ratio, 0.41; 95% confidence interval 0.23-0.74).
Conclusion: High Tcell _inf GEP status, but not PD-L1 or PD-L2 expression, was independently associated with longer survival in patients with LA HNSCC. Results may have implications for evaluating therapies targeting programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) in HNSCC.
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