PMCH and head and neck squamous cell carcinoma: Among the nine immunotherapy-related DEGs (SPINK5, SEMA3E, ROBO2, BMP5, ORM1, CRP, CTSE, PMCH, and CCL3L1), differential analysis showed that SPINK5 was significantly overexpressed in head and neck squamous cell carcinoma (HNSCC) samples compared to that in normal tissues, and SPINK5 expression levels were positively associated with Treg cells in the tumor microenvironment (39).