Pexmetinib suppresses osteoclast formation and breast cancer induced osteolysis via P38/STAT3 signal pathway.

Breast cancer metastases to the bone can lead to a series of bone-related events that seriously affect the quality of life. Pexmetinib, a novel p38 mitogen-activated protein kinase (p38) inhibitor that has been evaluated in phase I clinical trials for myelodysplastic syndrome, but the effects of Pexmetinib on breast cancer induced osteolysis haven't been explored. Here, we found that Pexmetinib inhibited receptor activator of nuclear factor-κB ligand-induced osteoclast formation and bone resorption in vitro. Pexmetinib suppressed p38-mediated signal transducer and activator of transcription 3 (STAT3), which direct regulated transcription of the nuclear factor of activated T cells 1 (NFATc1), leading to reduced osteoclast formation. Moreover, Pexmetinib exerted anti-tumor effects in breast cancer cells in vitro via suppressing p38-mediated STAT3 activation and matrix metalloproteinases (MMPs) expression. Furthermore, Pexmetinib suppressed breast cancer-associated osteolysis in vivo. These results suggest that Pexmetinib may be a promising drug for the treatment of breast cancer-induced osteolysis.