TP53 and head and neck squamous cell carcinoma: 24R,25-dihydroxyvitamin D3, when acting on human head and neck squamous cell carcinoma cell line with estrogen receptor α66 negativity (UM-SCC-11A cells), suppresses proliferation, upregulates apoptosis-related markers (TUNEL positivity, p53 expression, and BAX/BCL2 ratio), and downregulates metastasis-associated markers, with these effects collectively reflecting its tumor-suppressive capacity (17).