SPHK1 and head and neck squamous cell carcinoma: On the day of tumor capture, IFN-γ and TNF-α ELISAs were performed on sera from HNSCC mouse models with knockout or overexpression of SPHK1/MMP1, with the results showing that SPHK1/MMP1 expression was negatively correlated with IFN-γ and TNF-α (Figure 6L-M).