PIK3CA and head and neck squamous cell carcinoma: Various genes have been highlighted as highly significant oncogenic drivers for HNSCC survival [46], including the four known driver genes PIK3CA, PRKCI, SOX2 and TP63. In silico analysis of TCGA HNSCC data included in Supplementary Figure S4 further illustrates that co-amplification of these four genes occurs frequently in HNSCC, thus showing that 3q26 amplification in HNSCC is not restricted to the SOX2 gene.