Then, we pharmacologically inhibited the IMPDH1 activity of HNSCC cells using a pan IMPDH inhibitor (MPA) and its pro-drug (MMF) to assess their anti-tumor effects.14,15 CCK8 assay showed that treatment with MPA or MMF dramatically decreased HNSCC cell viability (Fig. 6c, d). This evidence concerns the gene IMPDH1 and head and neck squamous cell carcinoma.