Tonkinensine B induces apoptosis through mitochondrial dysfunction and inactivation of the PI3K/AKT pathway in triple-negative breast cancer cells.

Objectives Tonkinensine B, a novel compound with cytisine-pterocarpan skeleton isolated from the root of Sophora tonkinensis Gagnep, was reported to have a significant antitumor effect. The effect and intrinsic mechanism of tonkinensine B on tumour need to be further investigated. Methods With the help of cell cytotoxicity, the effect of tonkinensine B on MDA-MB-231 cells was investigated. By observing mitochondrial function changes, the intrinsic mechanism was further studied. The levels of key apoptosis-associated proteins Bcl-2, Bax, caspase-9, caspase-3 and AKT in MDA-MB-231 cells were analysed to determine whether tonkinensine B caused apoptosis via the mitochondrial pathway. Key findings After treated with tonkinensine B, MDA-MB-231 cells multiplication was repressed, and the decreased mitochondrial membrane potential, loss of ATP synthesis and elevated ROS generation were detected. Furthermore, the proportions of Bax/Bcl-2, cleaved caspase-3 and caspase-9 proteins production were up-regulated, indicating that tonkinensine B acted on intrinsic mitochondrial-mediated apoptosis pathway. In addition, tonkinensine B also reduced phosphorylation levels of AKT, and thus the activation of apoptosis might likewise be correlated with the inhibition of the PI3K/AKT pathway. Conclusions Tonkinensine B may be a hopeful candidate for human triple-negative breast cancer, and further structural optimization is expected to improve its anti-tumour activity.