Furthermore, CYP27A1 participate in synthesizing vitamin D.[13] In addition, B cells, T cells, antigen-presenting-cells and other immune cells both present vitamin D receptors.[14]Therefore, CYP27A1 may influence the synthesis of vitamin D and further regulate the T cells to affect the tumor immune microenvironment of HNSCC. This evidence concerns the gene VDR and head and neck squamous cell carcinoma.