PIK3CA and cancer: To identify the co-occurrence mutation signature between CC and HNSCC, 289 common co-occurrence mutation genes were merged (Figure 5E, Supplementary Table 5), which were enriched in some cancer pathways, such as proteoglycans in cancer (P = 3.55e-05), positive regulation of phosphatidylinositol 3-kinase (PI3K) signaling (P = 9.77e-05), microtubule-based movement (P = 4.79e-05), and chromosome segregation (P = 0.0002), et al. (Figure 5F).