SPHK1 and head and neck squamous cell carcinoma: We further explored the effects of SPHK1/MMP1 on T-cell proliferation activity in HNSCC by co-culturing Jurkat cells with SAS and SCC15 HNSCC cell lines with knocked-down/overexpressed SPHK1/MMP1 for 24 h and then measuring the expression of IL2, a key signaling molecule for T-cell proliferation, in the culture supernatants.