CTLA4 and head and neck squamous cell carcinoma: In order to investigate if the negative association between CTLA4 promoter methylation and tumor immune infiltration is a tumor entity-independent phenomenon, we analyzed CTLA4 promoter methylation and tumor-infiltrating immune cells in a cohort of N = 138 patients with HNSCC (UKB Non-ICB cohort) by means of quantitative methylation-specific PCR (qMSP).