Objective:To investigate effects of capecitabine metronomic chemotherapy combined with exemestane on the proliferation of breast cancer MCF-7 cells and PI3-K/AKT signaling pathway.Methods:MCF-7 cells cultured in vitro were divided into the control group (adding DMEM without drugs), 30 μmol/L exemestane group, capecitabine metronomic chemotherapy combined drugs group [30 μmol/L exemestane combined with different concentrations (50, 33, 17 μmol/L) of capecitabine]. CCK-8 assay was used to detect the cell proliferation inhibition rate, the half-maximal inhibitory concentration ( IC50) was calculated, and the changes of cell cycle and apoptosis rate of MCF-7 in different drug groups were assessed by using flow cytometry. The related-protein expression of PI3K-AKT signaling pathway of MCF-7 cells was detected by using Western blot. Results:The IC50 of capecitabine and exemestane on MCF-7 cells for 72 h was 101.2 μmol/L and 60.6 μmol/L, respectively. The proliferation inhibition rate of MCF-7 cells in 30 μmol/L exemestane for 24 h and 48 h combined with 50, 33 and 17 μmol/L capecitabine group was higher than that in 30 μmol/L exemestane group (all P<0.01). The apoptosis rates were (18.1±2.6)%, (34.6±3.0)%, (27.6±1.3)%, (23.1±1.6)%, respectively in 30 μmol/L exemestane group, 30 μmol/L exemestane + 50 μmol/L capecitabine group, 30 μmol/L exemestane + 33 μmol/L capecitabine group, 30 μmol/L exemestane + 17 μmol/L capecitabine group, and the difference was statistically significant ( F = 23.652, P<0.01). Compared with the control group, the proportion of MCF-7 cells in phase G 2 of 30 μmol/L exemestane group was increased [(16.7±2.6)% vs. (10.6±2.2)%], while that in phase G 1 was decreased [(53.3±4.0)% vs. (56.3±3.2)%]. The proportion of MCF-7 cells in phase S of 30 μmol/L exemestane + 50 μmol/L capecitabine group was increased [(39.0±3.6)% vs. (33.1±2.0)%]. MCF-7 cells of 30 μmol/L of exemestane + 33 μmol/L capecitabine group were more blocked in phase S [(51.7±4.1)%], and cells in phase G 2 were nearly disappeared [(1.2±0.5)%]; the cell proportion MCF-7 cells in phase G 2 of 30 μmol/L exemestane plus 17 μmol/L capecitabine group was increased [(26.2±3.1)%]. Western blot analysis showed that low dose capecitabine metronomic chemotherapy promoted exemestane to inhibit the expression of PI3K, motivated AKT serine phosphorylated at protein 473 [the increased expression of p-AKT (473)], promoted S6 protein expression at downstream of signaling pathway and increased its phosphorylation level (the increased expression of p-S6), thereby activating apoptosis signal. Conclusion:Capecitabine metronomic chemotherapy combined with exemestane can synergistically inhibit the proliferation of breast cancer MCF-7 cells and activate apoptosis mechanisms of MCF-7 cells through affecting PI3K-AKT signaling pathway.