MTOR and head and neck squamous cell carcinoma: To evaluate the effects of rigosertib on PI3K/Akt/mTOR signaling in HNSCC, we incubated FaDu and UMSCC 47 cells with DMSO (vehicle control), 1.0 μM ON 01911.Na (inactive control compound), or rigosertib (0 – 10 μM) for 12 hours, and assessed PI3K activity by ELISA.