First, we checked SLFN11 mRNA expression by quantitative RT-PCR in five HNSCC cell lines (HSC-2, HSC-3, HSC-4, SCC-9, and SCC-25) and found that SLFN11 expression in HSC-2, HSC-3, and HSC-4 cells was higher than that in SCC-9 and SCC-25 cells (Supplementary Figure 2A). Here, SLFN11 is linked to head and neck squamous cell carcinoma.