SMPD3 and head and neck squamous cell carcinoma: In head and neck squamous cell carcinoma, the expression of cl8-Cer is significantly reduced [59]; in addition, Cer metabolism-related enzymes, such as neutral SM hydrolase 2 (nSMase2 or SMPD3), can increase the level of Cer by hydrolyzing SM to inhibit cell proliferation and prolong cell cycle.