Danusertib (Danu) is a pan-inhibitor of
Aurora kinases and a third-generation breakpoint cluster region-Abelson murine
leukemia viral oncogene homolog 1 (
Bcr-Abl) tyrosine kinase inhibitor, but its antitumor effect and underlying mechanisms in the treatment of human
breast cancer remain elusive. This study aimed to investigate the effects of Danu on the growth, apoptosis, autophagy, and epithelial-to-mesenchymal transition (EMT) and the molecular mechanisms in human
breast cancer MCF7 and MDA-MB-231 cells. The results demonstrated that Danu remarkably inhibited cell proliferation, induced apoptosis and autophagy, and suppressed EMT in both
breast cancer cell lines. Danu arrested MCF7 and MDA-MB-231 cells in G2/M phase, accompanied by the downregulation of
cyclin-dependent kinase 1 and
cyclin B1 and upregulation of p21 Waf1/Cip1, p27 Kip1, and p53. Danu significantly decreased the expression of
B-cell lymphoma-extra-large (Bcl-xl) and
B-cell lymphoma 2 (Bcl-2), but increased the expression of
Bcl-2-associated X protein (Bax) and p53-upregulated modulator of apoptosis (PUMA), and promoted the cleavage of
caspases 3 and 9. Furthermore, Danu significantly increased the expression levels of the membrane-bound
microtubule-associated protein 1A/1B-light chain 3 (LC3-II) and
beclin 1 in
breast cancer cells, two markers for autophagy. Danu induced the activation of
p38 mitogen-activated protein kinase (MAPK) and
extracellular signal-regulated kinases 1 and 2 (Erk1/2) and inhibited the activation of
protein kinase B (Akt)/
mammalian target of rapamycin (mTOR) signaling pathways in
breast cancer cells. Treatment with
wortmannin (a
phosphatidylinositol 3-kinase inhibitor) markedly inhibited Danu-induced activation of
p38 MAPK and conversion of cytosolic LC3-I to membrane-bound LC3-II. Pharmacological inhibition and
small interfering RNA-mediated knockdown of
p38 MAPK suppressed Akt activation, resulting in LC3-II accumulation and enhanced autophagy. Pharmacological inhibition and
small interfering RNA-mediated knockdown of Erk1/2 also remarkably increased the level of LC3-II in MCF7 cells. Moreover, Danu inhibited EMT in both MCF7 and MDA-MB-231 cells with upregulated
E-cadherin and
zona occludens
protein 1 (ZO-1) but downregulated
N-cadherin,
zinc finger E-box-binding homeobox 1 (TCF8/ZEB1), snail, slug,
vimentin, and β-
catenin. Notably, Danu showed lower cytotoxicity toward normal breast epithelial MCF10A cells. These findings indicate that Danu promotes cellular apoptosis and autophagy but inhibits EMT in human
breast cancer cells via modulation of
p38 MAPK/Erk1/2/Akt/mTOR signaling pathways. Danu may represent a promising
anticancer agent for
breast cancer treatment. More studies are warranted to fully delineate the underlying mechanisms, efficacy, and safety of Danu in
breast cancer therapy.