Introduction:
The aim of this study was to investigate the proliferation and apoptosis of T24 after treatment with isoliquiritigenin (ISL) and to explore the underlying mechanism.

Material and methods:
T24 cells were divided into 6 groups and cultured. The five experimental groups were seeded into medium with 10, 20, 40, 80, and 160 µM ISL and the control group was administered with 0.01% DMSO. The cell morphology was observed using an optical microscope. The proliferation of cells and half maximal inhibitory concentration (IC50) were determined and calculated by MTS. Cell cycle and apoptosis were evaluated by flow cytometry. The migration ability of cells was detected by wound healing assay. The expression of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and proliferating cell nuclear antigen (PCNA) was determined by RT-qPCR and western blot.

Results:
At 24 h after treatment with ISL, morphology revealed that cell number diminished and the cell volume shrank with increasing concentration. According to the results of MTS, ISL significantly inhibited the T24 cell proliferation in a dose- and time-dependent manner. Flow cytometry showed that ISL could block the replication of T24 cell DNA from S phase to G2, therefore promoting cell apoptosis. Wound healing assay showed that at 48 h after treatment with ISL, the migration of T24 cells was remarkably inhibited. The results of RT-qPCR and Western blot revealed that after 24 h of treatment, the expression levels of Bcl-2 and PCNA were down-regulated, and the expression level of Bax was increased in the different dose of the ISL treated group.

Conclusions:
ISL possesses detrimental effects on the viability of BC cell T24 in a dose-dependent manner via blocking the cell cycle and inducing apoptosis by down-regulation of PCNA and Bcl-2 expression and up-regulation of Bax expression.