Modulation of Estrogen Receptor Activity by the Phytoalexin Tuberosin Produced from Elicited Kudzu (Pueraria lobata)

Kudzu’s invasive nature has contributed to its classification as a weed, as it frequently outcompetes native plant species, leading to extensive overgrowth. Efforts to control kudzu have proven challenging, with moderate success using physical or biological agents. In this study, we evaluated the effects of two such control agents, ultraviolet C radiation and Myrothecium verrucaria, to significantly increase the production of tuberosin, a phytoalexin isoflavone. Our findings demonstrate that estrogenic activity of tuberosin is cell-type-dependent, displaying antagonist or competitive inhibition when combined with 17-β-estradiol in the estrogen receptor (ER) positive cell lines MCF-7 and T-47D, while showing dose-dependent agonist activity in HEK293 cells transfected to express both ER receptors (α and β). Tuberosin was shown to modulate ER pathways, alter ER-mediated gene expression, and increase cell proliferation in a dose-dependent manner while maintaining expression of the ERα protein. Binding affinity and docking simulations confirmed tuberosin binding to the ERα pocket in a similar but weaker manner compared to synthetic estrogen. Tuberosin-treated endothelial cells suppressed vascular network assembly and maturation without affecting the cellular proliferative capacity. The presented studies leverage current kudzu management methods to naturally produce tuberosin, examine cell-type-specific effects, and support further investigation as an antiestrogen for breast cancer treatment.