To assess whether depletion of SUV420H1 affects the proliferation of HPV-negative HNSCC cells, we utilized three different siRNAs targeting SUV420H1, but not other H4K20 methyltransferases, such as SUV420H2 and SETD8 (Supplementary Fig. 4). This evidence concerns the gene KMT5C and head and neck squamous cell carcinoma.