PIK3CA and head and neck squamous cell carcinoma: When examining responses to inhibitors of upstream and downstream members of the PIK3CA pathway, the FAK inhibitor PF-562271 (upstream) demonstrated a trend towards selective inhibition of PIK3CA HNSCC mutant cell lines (LFDR = 0.079, Figure 4B), while no effect was observed for downstream inhibitors including three AKT inhibitors (AKT inhibitor VIII, MK-2206, A-443654) and four mTOR inhibitors (Rapamycin, Temsirolimus, JW-7-52-1, AZD8055).