Objective   This study aimed to investigate the effects and the molecular mechanism of JNJ-7706621 on cell cycle and apoptosis of breast cancer cell lines.

  Methods   Breast cancer cell lines T47D and MDA-MB-231 were cultured in vitro and treated with JNJ-7706621 at varying concentrations. MTT assay was used to measure cell proliferation. Flow cytometry was applied to analyze the distribution of cell cycle and apoptotic rates. Western blot was performed to analyze the expression of cyclin B1-CDK, the phosphorylation levels of CDK1Thr161 and CDK1Tyr15, as well as the expression of p53, Bcl-2, caspase3 and poly(ADP-ribose) polymerase (PARP).

  Results   JNJ-7706621 inhibited the proliferation of the T47D and MDA-MB-231 cells in a dose- and time-dependent manner. Flow cytometry showed that the T47D and the MDA-MB-231 cells in the G2/M-phase significantly increased after treatment at varying concentrations (0, 1, 2, 4 μM) of JNJ-7706621: the G2/M-phase rates at the corresponding concentrations were (12.66±1.55)%, (20.63± 1.32)%, (23.20±1.82)%, and (32.19±2.37)%, respectively, for the T47D cells (P < 0.05), and the G2/M-phase rates were (16.22±1.48)%, (21.45±0.85)%, (25.25±1.26)%, and (31.08±1.16)%, respectively, for the MDA-MB-231 cells (P < 0.05). The rates of apoptotic cells were also significantly increased (P < 0.05). Western blot results indicated that JNJ-7706621 exerted a slight effect on the expression of CDK1 and p53 and that the phosphorylation level of CDK1 decreased at the Thr161 site but increased at the Tyr15 site. In addition, cleaved caspase3 and PARP increased, whereas Bcl-2 and cyclinB1 decreased significantly.

  Conclusion  JNJ-7706621 can significantly inhibit the proliferation of breast cancer cell lines T47D and MDA-MB-231 by inducing cell cycle arrest and apoptosis, which may be associated with the downregulation of the CDK1 phosphorylation at the Thr161 site.