Of the 15 most recurrently mutated HNSCC or GB-SCC genes, 8 genes (PCLO, SYNE2, FAT3, EP300, KMT2B, SMG1, TRPM3 and UNC13C) were mutated in >10% of smokeless tobacco associated GB-SCC tumours of ICGC6 but not in the cigarette smoking associated HNSCC of TCGA study13 and may be considered as smokeless tobacco associated genes (Fig. 5A,B). This evidence concerns the gene SMG1 and head and neck squamous cell carcinoma.