An novel inhibitor of TGF-β type I receptor, IN-1130, blocks breast cancer lung metastasis through inhibition of epithelial–mesenchymal transition

• IN-1130 inhibited Smad/TGF-β signaling, EMT, cell migration, and invasion.
• IN-1130 inhibited lung metastasis of mammary tumor in mice models.
• IN-1130 prolonged the life span of tumor bearing mice.

TGF-β signaling plays an important role in breast cancer progression and metastasis. Epithelial–mesenchymal transition (EMT) is an important step in the progression of solid tumors to metastatic disease. We previously reported that IN-1130, a novel transforming growth factor-β type I receptor kinase (ALK5) inhibitor, suppressed renal fibrosis in obstructive nephropathy (Moon et al., 2006). Here, we show that IN-1130 suppressed EMT and the lung metastasis of mammary tumors in mouse models. Treating human and mouse cell lines with IN-1130 inhibited TGF-β-mediated transcriptional activation, the phosphorylation and nuclear translocation of Smad2, and TGF-β-induced-EMT, which induces morphological changes in epithelial cells. Additionally, we demonstrated that IN-1130 blocked TGF-β-induced 4T1 mammary cancer cell migration and invasion. The TGF-β-mediated increase in matrix metalloproteinase (MMP)-2 and MMP-9 expression was restored by IN-1130 co-treatment with TGF-β in human epithelial cells and in 4T1 cells. Furthermore, we found that lung metastasis from primary breast cancer was inhibited by IN-1130 in both 4T1-xenografted BALB/c mice and MMTV/c-Neu transgenic mice without any change in primary tumor volume. IN-1130 prolonged the life span of tumor-bearing mice. In summary, this study indicated that IN-1130 has therapeutic potential for preventing breast cancer metastasis to the lung.