Mice bearing BT-474 tumors (n=14) are orally administered 50 mg/kg of Everolimus on a daily basis for 31 days and then randomized. After randomization, the mice are orally administered 50 mg/kg of Everolimus (n=4) and 12.5 mg/kg (n=5), and 25 mg/kg (n=5) of Izorlisib on a daily basis for 7 days. C, the vehicle-, Everolimus, and CH5132799-treated (25 mg/kg) tumors are resected at 4 hours after terminal administration in B, lysed, and analyzed by Western blotting. Izorlisib administration leads to a remarkable regression in a dose-dependent manner of the tumors regrown after the long-term Everolimus treatment. The tumors are resected at the end of treatment and analyzed by Western blotting with respect to PI3K pathway inhibition. Izorlisib suppresses various effectors in the PI3K pathway, including Akt, FoxO1, S6K, S6, and 4E-BP1, whereas Everolimus inhibits only phosphorylation of S6K and S6, both downstream effectors of mTORC1[1].
