The combination of BEZ235 with either anti-HER2 agents or an MEK inhibitor reduces cell proliferation and induces apoptosis. (a) Cell proliferation assay of BT474, SKBR3 and BT474-Tr cells treated with BEZ235 (B, 10 n), lapatinib (L, 20 n), trastuzumab (T, 1 n), AZD6244 (A, 2 μ) or the indicated combinations for 15 days. Cell proliferation was quantified by crystal violet. The fold difference of viable cells is shown relative to the viable cells treated with BEZ235. In order to better visualize the differences between BEZ235-treated cells as single agent or in combination with the aforementioned agents, proliferation of control, trastuzumab and AZD6244-treated cells has been omitted. (b) Cell death expressed as sub-G0/G1 of BT474, SKBR3 and BT474-Tr cells treated with BEZ235 (B, 100 n), lapatinib (L, 100 n), trastuzumab (T, 50 n), AZD6244 (A, 2 μ) or the indicated combinations for 72 h. The subG0/G1 population was quantified by FACS analysis and related to the amount of apoptotic cells upon BEZ235 treatment. Error bars indicate SE of two (a) or three (b) independent experiments. *P<0.05.