Background: Breast cancer is one of the most prevalent diseases threatening women's health today. Indepth
research on breast cancer (BC) pathogenesis and prevention and treatment methods are gradually receiving
attention. Chidamide is a novel histone deacetylase inhibitor (HDACi) that depresses the function of histone
deacetylase, consequently affecting the growth of BC cells through epigenetic modification. However, preclinical
and clinical studies show that chidamide is ineffective in long-term treatment. We demonstrated in previous experiments
that TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in BC cells and is significantly
less non-toxic to normal cells than chidamide. Therefore, in this study, we treated BC cells with chidamide and
TRAIL to explore a novel option to reduce the clinical toxicity through augmenting the sensitivity for BC cells.
Methods and Results: Results from the MTT and cell viability assays indicated that the combination of chidamide
and TRAIL in MCF-7 and MDA-MB-231 cells induced BC cell death, while maintaining a reduced concentration
of chidamide. Autophagy assay and annexin V analysis showed that the autophagosome microtubuleassociated
protein1light chain3-II (LC3-II) was abnormally increased and much more early and late phase of
apoptotic cells appeared during chidamide and TRAIL induction. Anti-tumor assays in a BC tumor xenograft
model displayed that the mixture of chidamide and TRAIL exhibited stronger effects on inhibiting tumor growth.
The data from real-time PCR and western blotting showed that the cytotoxic effect correlated with the expressions
of related apoptosis and autophagy factors.
Conclusion: Our data are the first to demonstrate the synergistic effects of chidamide and TRAIL in BC cells,
specifically, the pharmacological effects on cell death induction. These results lay a solid experimental and theoretical
basis to solve the clinical resistance of chidamide.