Combined inhibition of Hhat and PI3K/mTOR effectively reduces breast cancer cell proliferation. A-C, T47D (A), MCF7 (B), and BT474 (C) cells were cultured for 6 days in the presence of 10 μM RU-SKI 43 alone or in combination with 10 μM LY294002 or 10nM rapamycin. Cell numbers were quantified and normalized to DMSO treated cells (100 x (drug/DMSO)). Bars represent mean ± SD (n = 3) for all panels. Three independent experiments were performed in duplicate using cells at three different passages. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001; Student’s t test.