Wedelolactone, a Component from Eclipta prostrata (L.) L., Inhibits the Proliferation and Migration of Head and Neck Squamous Cancer Cells through the AhR Pathway

Background: Ecliptae prostrata (L.) L. has been widely used in East Asia with reported biological activities, including anti-cancer properties.

Objectives: We aimed to investigate the effect of ethyl acetate extract of Ecliptae prostrata (L.) L. (EAE) and its component wedelolactone on the proliferation and migration of head and neck squamous cancer cells.

Methods: The proliferation of human SCC-4 and mouse CU110-1 tongue squamous carcinoma cells was assessed using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) method. Scratch wound assays were performed to assess cell migration rates. The levels of Ecadherin and vimentin were used as markers of the epithelial-to-mesenchymal transition (EMT). AhR, CYP1A1, and CYP1B1 levels were examined to uncover the mechanism of inhibition of cell migration by wedelolactone.

Results: We found that EAE and wedelolactone decreased the proliferation of human SCC-4 cells and mouse CU110-1 cells at doses of EAE at > 25 μg/ml and wedelolactone at > 6.25 μg/ml. Similarly, both EAE and wedelolactone produced inhibitory effects against migration, but the effective doses that significantly inhibited migration were lower than those affecting proliferation. Wedelolactone below 12.5 μg/ml inhibited the epithelial-to-mesenchymal transition (EMT) with increased expression of E-cadherin and decreased expression of vimentin in SCC-4 and CU110-1 cells. Further analysis showed wedelolactone inhibited the expression of AhR and its downstream target molecules CYP1A1 and CYP1B1 in both squamous carcinoma cells at the same doses inhibiting cell migration. The addition of benzo (a)pyrene [B(a)P], an agonist of AhR, stimulated migration, especially in the CU110-1 cells with reported cancer stem cell-like characteristics. Instructively, B(a)P reversed the inhibitory effects of wedelolactone on AhR expression and cell migration, suggesting that wedelolactone antagonizes cell migration through the AhR pathway. Moreover, the higher activity of EAE and wedelolactone against the migration of cancer stem-like CU110-1 cells relative to SCC-4 cells suggests selective activity against cancer stem cells.

Conclusion: Our study identifies wedelolactone as a major active component of Ecliptae prostrata (L.) L. with promising anti-cancer properties against head and neck squamous cancer cells.