OBJECTIVE: To probe into the impacts of total glycosides of Ranunculus japonicus (TGRJ) on biological behavior of breast cancer (BC) cells and the molecular mechanism. STUDY DESIGN: Paired cancerous tissue and adjacent tissue were collected from 37 patients with BC. circPGAM1 and miR-32-5p were detected by real-time fluorescence quantitative PCR. T47D cells were randomized into control group, low-, medium-, and high-concentration groups of TGRJ, si-circPGAM1 group, si-NC group, and TGRJ+pcDNA-circPGAM1 group. The cell multiplication inhibition rate was determined by MTT assay, apoptosis was detected by flow cytometry, colony formation number by colony formation experiment, and the healing rate of cell scratches by wound-healing assay. Measurement of cleaved caspase-3 protein employed western blot, and verification of the targeting relationship between circPGAM1 and miR-32-5p adopted double luciferase reporter assay. RESULTS: circPGAM1 and miR-32-5p were negatively correlated, and circPGAM1 was increased while miR-32-5p was decreased in BC tissue as compared with adjacent tissue (p<0.05). The multiplication inhibition rate and apoptosis rate of T47D cells increased gradually with the increasing concentrations of TGRJ, and the wound healing rate and colony formation number reduced gradually. Cleaved caspase-3 and miR-32-5p elevated while circPGAM1 declined in a concentration-dependent manner (p<0.05). Inhibition of circPGAM1 led to increased miR-32-5p and cleaved caspase-3, declined wound healing rate and colony formation number, as well as increased multiplication inhibition rate and apoptosis rate of T47D cells (p<0.05). CircPGAM1 targeted miR-32-5p. Overexpression of circPGAM1 reversed the impacts of TGRJ on multiplication, apoptosis, and migration of T47D cells. CONCLUSION: TGRJ can suppress the malignant biological behavior of BC cells by modulating the circPGAM1/miR-32-5p. © Science Printers and Publishers, Inc.