PCLO and head and neck squamous cell carcinoma: 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).