ObjectiveTo study the apoptotic induction effect of Thapsigargin on estrogen receptor positive human breast cancer cell lines MCF7. MethodsCells were treated with Thapsigargin and 5FU in vitro. The rate of cell apoptosis and distribution of cell cycle were detected on flow cytometry. The cell viability was measured by MTT assay and ultrastructural changes in apoptotic cells were confirmed by transmission electron microscopy.ResultsThapsigargin could increase the rates both of cell apoptosis and growth supression of MCF7 cells induced by 5FU and alter the distribution of cell cycle. Under electron microscope, apoptotic bodies in MCF7 cells considerably increased.ConclusionThapsigargin apparently enhances the effect of apoptotic induction of 5FU on MCF7 cells, it is worthy of being further studied.