Abstract: AIM: To investigate the effects of xy9902 on the proliferation in MCF-7 cells and its mechanism. METHODS: Effects of xy9902 on the proliferation of MCF-7 cellswere determined by MTT measurement.Cell cycle was examined by flow cytometry.Competitive estro-gen-receptor binding assay was used to investigate the af-finity of xy9902 to ER.RESULTS: xy9902 induced cell proliferation of MCF-7 cells at a lower concentration with an increase of the number of cells in S phase.On the contrary, inhibited cell proliferation at higher concentra-tionswith a decrease of the number of cells in S phase. Tamoxifen could block the stimulation of proliferation ef-fect of MCF-7 induced by xy9902.The relative binding affinity of xy9906 for ERαand ERβ showed an IC₅₀ of 8.45 ×10^-6 and 1.66 ×10^-6 mol·L^-1 respectively. CONCLUSION: xy9902 directly stimulates cell prolifer-ation of MCF-7 cells through ligand-receptor binding at a low concentrations and inhibits cell proliferation at high concentrations.

Key words: benzaodihydropyran, derivative, xy9902, MCF-7 cells, estrogen receptor, proliferation