A: Two representative cell lines were treated with neratinib 0.01 µM, taselisib 0.01 µM and the combination of both (neratinib 0.01 µM and taselisib 0.01 µM) collected 24 hours and 48 h (B) after treatment. Cells were used for Western blotting analyses of phosphorylated HER2, EGFR, AKT and S6. Neratinib was able to reduce levels of p-HER2 and p-EGFR in both cell lines tested. Combination treatment led to reduced levels of p-AKT and p-S6 in USPC-ARK-1 cells, while a decrease in p-S6 but not p-AKT was found in combination-treated USPC-ARK-2 cells. Expression of GAPDH was used as loading control. C: USPC-ARK-1 single agent resistant cell lines. Two weeks exposure to neratinib induced significant increase in phosphorylated AKT, while two weeks exposure to taselisib induced a significant increase phosphorylated HER2, EGFR and ERK.