Energy‑stress‑mediated Activation of AMPK Sensitizes MPS1 Kinase Inhibition in Triple‑negative Breast Cancer

Monopolar spindle 1 kinase (Mps1, also known as TTK protein kinase) inhibitors exert marked anticancer effects against triple‑negative breast cancer (TNBC) by causing genomic instability and cell death. As aneuploid cells are vulnerable to compounds that induce energy stress through adenosine monophosphate‑activated protein kinase (AMPK) activation, the synergistic effect of Mps1/TTK inhibition and AMPK activation was investigated in the present study. The combined effects of CFI‑402257, an Mps1/TTK inhibitor, and AICAR, an AMPK agonist, were evaluated in terms of cytotoxicity, cell‑cycle distribution, and xenograft models. Additional molecular mechanistic studies were conducted to elucidate the mechanisms underlying apoptosis and autophagic cell death. The combination of CFI‑402257 and AICAR showed selective cytotoxicity in a TNBC cell line. The formation of polyploid cells was attenuated, and apoptosis was increased by the combination treatment, which also induced autophagy through dual inhibition of the PI3K/Akt/mTOR and mitogen‑activated protein kinase (MAPK) signaling pathways. Additionally, the combination therapy showed strongly improved efficacy in comparison with CFI‑402257 and AICAR monotherapy in the MDA‑MB‑231 xenograft model. The present study suggested that the combination of CFI‑402257 and AICAR is a promising therapeutic strategy for TNBC.