Abstract PO-082: Antigen presentation and inflammatory effects on immune surveillance: Window of opportunity metformin monotherapy trial for squamous cell carcinoma of the head and neck (HNSCC)

Abstract Introduction: The tumor microenvironment frequently displays dysregulated cellular metabolism, which contributes to aggressive behavior of the tumor. Though the mechanism of effect is unclear, clinical data suggest an association between metformin and improved outcomes in head and neck squamous cell carcinoma (HNSCC). The aim of this study is to investigate post-metformin treatment effects on the tumor microenvironment (TME) of HNSCC by using spatial RNA sequencing data from a metformin monotherapy window-of-opportunity clinical trial. Methods: This was a single-center prospective clinical trial of metformin in patients with HNSCC and a plan for definitive surgical resection. Primary lesions were biopsied prior to treatment and compared to matched post-treatment surgical specimens. Following biopsy-proven HNSCC diagnosis, metformin was initiated at 500 mg/day and increased to 1,000 mg twice daily by day 6. Spatial RNA sequencing of 18,000+ genes in CD45, CD163, and PanCK segments was conducted using Nanostring’s GeoMx digital spatial profiling (DSP). Sequencing data was analyzed by using unbiased gene set enrichment analysis (GSEA) and reported as a rank in gene list from 18,000+ total genes for post- vs pre-treatment analyses. Results: In all HPV positive, post-treatment samples in all three segments, GSEA demonstrated enrichment of antigen presenting cell types including NK cells, monocytes, and dendritic cells (q< 0.001). Inflammatory and metabolism signatures (IFN-y, IFN-a, oxidative phosphorylation) were enriched after metformin monotherapy in HPV+ samples within the PanCK positive segment (q< 0.001). Epithelial mesenchymal transition (EMT) was noted to be positively enriched while plasma cell signatures were negatively enriched within in HPV- post-treatment samples in the CD163 segment (q< 0.001). Within the CD45 positive segment, enriched expression of mRNAs for ribosomal-protein subsets were noted in T-cell gene sets and not in B-cell gene sets; in the CD45 segment, cytoplasmic ribosomal proteins is the second-most enriched gene set from C2 canonical pathways gene sets. Conclusion: Antigen presentation, inflammation, and ribosomal protein encoding genes were enriched with metformin monotherapy in the window of opportunity setting for HNSCC. Ribosomal proteins may also play a role in antigen presentation and immune surveillance in the post-treatment setting. Further research is required to describe the TME effects of metformin monotherapy and its effects on treatment response. Citation Format: Derek S. Mann, Sruti Tekumalla, Amiti Jain, Jacob Riordan, Alban Linnenbach, Diana Menezes, Ubaldo Martinez-Outschoorn, Joseph M. Curry. Antigen presentation and inflammatory effects on immune surveillance: Window of opportunity metformin monotherapy trial for squamous cell carcinoma of the head and neck (HNSCC) [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-082.