However, expression of activating PIK3CA mutants endogenously in Detroit 562 HNSCC cells or ectopically in Cal27 cells reverted this activity (Fig. 2b), which was extended to other HNSCC cells (HN12 and SCC47) expressing PIK3CA mutants (Supplementary Fig. 2). Here, PIK3CA is linked to head and neck squamous cell carcinoma.