Celastrol enhances tamoxifen sensitivity in the treatment of triple negative breast cancer via mitochondria mediated apoptosis pathway.

OBJECTIVE: To investigate the enhancement of chemosensitivity of tamoxifen (TAM) in triple negative breast cancer (TNBC) by celastrol (CEL) through mitochondrial mediated pathway.

METHODS: Human TNBC MDA-MB-231 cells were divided to the control group (medium treatment), TAM-L group (low concentration TAM treatment, 0.5 μM TAM treatment), TAM-H group (1 μM TAM treatment), CEL-L group (low concentration CEL treatment, 1 μM CEL), CEL-H group (high concentration CEL treatment, 3 μM CEL), CEL-L+TAM group (low concentration CEL and TAM co-treatment) and CEL-H+TAM group (high concentration of CEL co-treated with TAM). The proliferation and invasion of cells in each cell group were detected by MTT assay and Transwell assay, respectively. Changes in mitochondrial membrane potential were determined by JC-1 staining. 2'-7'-dichlorofluorescein diacetate (DCFH-DA) fluorescence probe combined with flow cytometry was used to measure the levels of reactive oxygen species (ROS) in cells. The GSH/(GSSG+GSH) level in the cells was detected with glutathione (GSH)/oxidized glutathione (GSSG) enzyme-linked immunosorbent assay (ELISA) kit. The expression levels of the apoptosis-related proteins B lymphocytoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), sheared cysteine-containing aspartate protein hydrolase 3 (Cleaved Caspase-3), and cytochrome C (Cytc) in each group were measured by Western blot. The tumor model of subcutaneous transplantation of TNBC cells in nude mice was established. After administration, the volume and mass of tumors in each group were measured, and the tumor inhibition rate was calculated.

RESULTS: Compared with the Control group, cell proliferation inhibition rate (24 h, 48 h), apoptosis rate, ROS level, Bax, cleaved caspase-3 and Cytc protein expression were conspicuously increased in the TAM, CEL-L, CEL-H, CEL-L+TAM and CEL-H+TAM groups (all P < 0.05), and cell migration and invasion, mitochondrial membrane potential, GSH level, and Bcl-2 protein expression were conspicuously decreased (all P < 0.05). Compared with the TAM group, the cell proliferation inhibition rate (24 h, 48 h), apoptosis rate, ROS level, Bax, cleaved caspase-3 and Cytc protein expression were increased in the CEL-H+TAM group (all P < 0.05), and cell migration rate, cell invasion number, mitochondrial membrane potential, GSH level and Bcl-2 protein expression were decreased in the CEL-H+TAM group (all P < 0.05). Compared with the CEL-L group, the cell proliferation inhibition rate (24 h, 48 h), apoptosis rate, ROS level, Bax, cleaved caspase-3 and Cytc protein expression were significantly increased in the CEL-H group (all P < 0.05), and cell migration rate, cell invasion number, mitochondrial membrane potential, GSH level and Bcl-2 protein expression were decreased in the CEL-H group (all P < 0.05). Compared with the model group, the tumor volume of TAM group, CEL-H group, CEL-L+TAM group and CEL-H+TAM group decreased (all P < 0.05). Compared with TAM group, the tumor volume in CEL-H+TAM group decreased significantly (P < 0.05).

CONCLUSION: CEL can promote apoptosis and enhance the TAM sensitivity in TNBC treatment through a mitochondria-mediated pathway.