TLR4 and head and neck squamous cell carcinoma: In addition, we also assayed the mRNA expression level in the HNSCC cell lines SCC4, CAL27 (Fig. 1C), SCC9 and SCC25 (Figure S1), in which the basal expression level of RIG-I was much higher than that of MDA-5, and RIG-I was more potently induced than MDA-5 upon stimulation with the TLR4 ligand lipopolysaccharide (LPS), or transfection with 3p-RNA.