PIK3CA and nasopharyngeal carcinoma: Furthermore, we observed that the sensitivity to PQR309 remained unchanged despite siRNA targeting PI3K p110α or p110β. This was evident from the comparable half-maximal IC50 values of PQR309 in NPC cell lines, whether or not they had undergone genetic downregulation of PI3K p110α or p110β (Supplementary Fig. S2S, T).