Aim To investigate the effect of prodigiosin on the proliferation, migration, cell cycle and apopto- sis of adriamycin-resistant breast cancer cell line MCF- 7/ADR.Methods CCK-8, colony formation assay, scratch test and Transwell were used to detect the pro¬liferation and migration of MCF-7/ADR after treatment with different concentrations of prodigiosin.How cy¬tometry and DAP1 staining were used to detect the cell cycle and apoptosis of MCF-7/ADR cell line after treatment with different concentrations of prodigiosin.Western blot was used to detect the effect of prodigiosin on the expression of caspase-3, Bax and Bcl-2 in MCF- 7/ADR cells.Results Prodigiosin inhibited the pro¬liferation and migration of MCF-7/ADR cell line in a concentration- and time-dependent manner ( P <0.05 ).In addition, prodigiosin enhanced the in¬hibitor}' effect of adriamycin on MCF-7/ADR cell line.Prodigiosin arrested MCF-7/ADR cell line cycle in the S phase and induced cell apoptosis in a time- and dose- dependent manner.The percentage of S phase cells treated with 2 mg • L 1 prodigiosin for 48 hours in¬creased to 35.3% , and the apoptotic rate was as high as 64.83% , which were statistically significant com¬pared with the control group ( P < 0.05 ).Prodigiosin could up-regulate the expression of apoptosis protein caspase-3 and Bax and inhibit the expression of Bcl-2 protein in MCF-7/ADK cell.Conclusions Prodigio¬sin can effectively inhibit the proliferation, migration and promote cell apoptosis and regulate cell cycle in adriamvcin-resistant breast cancer cell line MCF-7/ ADR.Prodigiosin can enhance the sensitivity of MCF- 7/ADR cell line to adriamycin.