Identifying the Role of Regulatory Immune Cell Populations in HPV+ and HPV- Head and Neck Squamous Cell Carcinoma and Characterization of Changes during PD-1, CTLA-4, and LAG-3 Immunotherapy

• Applicant: Dr. Matthias Brand
• Subject Area: Otolaryngology, Phoniatrics and Audiology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 522169450

Despite the achievements of modern medicine, head and neck squamous cell carcinoma (HNSCC) still has a poor 5-year survival rate. To improve this outlook, the interaction of the immune system with HNSCC is currently the subject of intense research. In addition to conventional treatments such as surgery, radiation, and chemotherapy, enhancement of anti-tumor immune responses within the tumor microenvironment (TME) using immunotherapies (e.g., immune checkpoint inhibitors (ICI)) has shown great curative potential. The response rate of HNSCC patients under ICI is limited to approximately 20%. The reasons for the lack of response in such a large cohort of patients are ambiguous. In addition to tumor and stromal cells, the TME consists of anti-tumor immune cells (e.g., CD8+/CD4+ T cells, NK cells, and macrophages) and pro-tumor immune cells that suppress an immune response (e.g., regulatory B (Breg) and T (Treg) cells and M2 macrophages). The density and composition of the immune infiltrate within the TME is a prognostic marker for patient survival. In this work, the role of immunosuppressive cells in the TME of HPV+ and HPV- HNSCC patients is presented in Aim 1. HNSCC tumors will be analyzed for different immunosuppressive cell populations by flow cytometry, immunofluorescence microscopy and single-cell RNA sequencing (scRNAseq). We hypothesize that significant differences in density and quality of regulatory immune cell populations will be observed in the TME of HPV+ and HPV- HNSCC. Furthermore, the poorly described Breg will be genetically characterized and their function in ICI resistance will be deciphered. We will explore whether Breg are a prognostic biomarker for attenuated anti-tumor immune responses in the TME and worse clinical outcomes in HNSCC patients receiving ICI. In Aim 2, the impact of immunosuppressive cell populations receiving ICI will be investigated. Tissue specimens acquired from HNSCC patients enrolled in an innovative neoadjuvant trial (HCC# 18-139) will be used. The aim of this accruing clinical trial is to enhance the anti-tumor activity of anti-PD1 (nivolumab) by combining it with anti-LAG3 (relatlimab) or anti-CTLA-4 (ipilimumab) in locally advanced treatment-naive HNSCC patients. By comparing blood and tumor specimens acquired prior to and after neoadjuvant treatment, we aim to analyze the effects of these therapies on the quality and robustness of tumor immune infiltrate, particularly of immunosuppressive populations. Through these two Aims, this project will shed light on how specific immune-regulatory cell populations mold resistance to ICI, and may identify new druggable targets specific for immunosuppressive cell populations for future therapeutic approaches.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Robert Ferris, Ph.D.