Abstract 2352: Evaluation of alcohol, tobacco, and HPV’s synergistic regulation of HNSCC’s potential treatment response to PD-L1 checkpoint inhibitor treatment

Abstract Background: Enhanced PD-L1 (Programmed Death-Ligand 1) expression in tumor cells aids the evasion of immune surveillance. Nivolumab and pembrolizumab, PD-L1 blockade agents, have been applied in clinical settings to treat Head and Neck Squamous Cell Carcinoma (HNSCC), yet low response rates, unimproved prognosis, and treatment resistance necessitate further research into the underlying molecular mechanism. While alcohol, tobacco, and HPV exposure are the most prominent risk factors responsible for HNSCC pathogenesis, their synergistic influence on PD-L1 blockade treatment responses is largely unknown. In this study, we characterized how different combinations of the three etiologic factors alters the molecular landscape of HNSCC, influencing either favorable or adverse PD-L1 blockade treatment outcomes. Methods: HPV abundance was characterized in 498 primary HNSCC tumor samples. Together with alcohol and tobacco exposure history, samples were classified into 8 subgroups reflecting all possible combinations of the three exposure factors. Differential expression analysis was performed to examine both mRNA and miRNA regulation in relation to key PD-L1 signaling pathways (NF-κB, PI3K/Akt, and Ras/MEK/ERK). Tumor mutation burden (TMB) calculation and subgroup immune landscape profiling were performed to assess the potential response to PD-L1 blockade treatment. Gene Ontology (GO) and KEGG pathway enrichment analysis were then conducted to investigate genetic pathway and cellular processes associated with differential PD-L1 blockade treatment outcomes. Results: PD-L1 was significantly downregulated in the triple-exposure group (1.51 fold reduction, p < 0.05). Dysregulation of PD-L1-related genes, including JAK2 (triple-exposure group: 1.44 fold reduction, p < 0.05) and BRAF and ATR, was observed in multi-exposure subgroups (cigarette + HPV group: BRAF 0.781 fold reduction, p < 0.05; ATR 0.722 fold reduction, p < 0.05). miR-106, implicated in HPV pathogenesis, was most dysregulated in triple-exposure cases. miRNAs including miR-374b-5, miR-16, miR-29b, and miR-143, associated with poor prognosis, and key PD-L1 regulating pathways (PI3K/Akt and P53), were significantly altered in triple-exposure group. Pathway disruptions, including those related to histone regulation and chromosomal structure, increased with additional exposure factors. Tobacco-HPV dual exposure group showed the highest TMB with a 1.94-fold increase (p < 0.01) compared to the unexposed subgroup. The triple-exposure group exhibited the highest M2 macrophage enrichment (1.59 fold increase, p < 0.05) and CD8+ T-cell reduction (2.03 fold reduction, p < 0.05). Further studies are required to identify specified immunotherapeutic administration techniques to address the differential molecular landscapes in different exposure subgroups. Citation Format: Ruomin Xin, Omar Mokhashi, Miski Abdi, Riya Chhabra, Ling Duan, Alanna Sun, Daniel John, Wei Tse Li, Jessica Wang-Rodriguez, Weg M. Ongkeko. Evaluation of alcohol, tobacco, and HPV’s synergistic regulation of HNSCC’s potential treatment response to PD-L1 checkpoint inhibitor treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2352.