Camalexin, an indole phytoalexin, inhibits cell proliferation, migration, and mammosphere formation in breast cancer cells via the aryl hydrocarbon receptor.

Breast cancer is the most commonly diagnosed cancer among women worldwide. Despite a variety of drugs available for the treatment of patients with breast cancer, drug resistance remains a significant clinical problem. Therefore, there is an urgent need to develop drugs with new mechanisms of action.

Activation of the aryl hydrocarbon receptor by 3-methylcholanthrene, but not by indirubin, suppresses mammosphere formation via downregulation of CDC20 expression in breast cancer cells.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates various toxicological and biological functions. We reported previously that 3-methylcholanthrene (3MC), an exogenous AhR agonist, inhibited tumorsphere (mammosphere) formation from breast cancer cell lines, while the endogenous AhR agonist, indirubin, very weakly inhibited this process. However, the difference in inhibition mechanism of mammosphere formation by 3MC or indirubin is still unknown.