Disruption of the NF-κB/IL-8 Signaling Axis by Sulconazole Inhibits Human Breast Cancer Stem Cell Formation

Breast cancer stem cells (BCSCs) are tumor-initiating cells that possess the capacity for self-renewal. Cancer stem cells (CSCs) are responsible for poor outcomes caused by therapeutic resistance. In our study, we found that sulconazole-an antifungal medicine in the imidazole class-inhibited cell proliferation, tumor growth, and CSC formation. This compound also reduced the frequency of cells expressing CSC markers (CD44(high)/CD24(low)) as well as the expression of another CSC marker, aldehyde dehydrogenase (ALDH), and other self-renewal-related genes. Sulconazole inhibited mammosphere formation, reduced the protein level of nuclear NF-kappa B, and reduced extracellular IL-8 levels in mammospheres. Knocking down NF-kappa B expression using a p65-specific siRNA reduced CSC formation and secreted IL-8 levels in mammospheres. Sulconazole reduced nuclear NF-kappa B protein levels and secreted IL-8 levels in mammospheres. These new findings show that sulconazole blocks the NF-kappa B/IL-8 signaling pathway and CSC formation. NF-kappa B/IL-8 signaling is important for CSC formation and may be an important therapeutic target for BCSC treatment.