Abstract
The continued global rise in papillary thyroid carcinoma (PTC) combined with potential adverse effects of regular treatments calls for an alternative therapy. Prunella vulgaris L. (PV) is commonly used as a herbal remedy for thyroid diseases in China, but its influence on PTC is unclear. This study investigated the effect of PV aqueous extract on PTC and its underlying mechanism using a mouse xenograft model and the human PTC cell line K1. PV suppressed tumor growth in PTC-bearing mice at 0.05 and 0.1 g/kg bw, accompanied by improvements in autophagy-related protein expressions in xenografts. In K1 cells, PV inhibited cell growth and induced autophagic flux, manifesting as changes in autophagy-related proteins, the presence of autophagosomes, and a further increase in LC3-II by co-incubation with bafilomycin A1. Autophagy inhibitor 3-methyladenine ameliorated the autophagic cell death caused by PV. The mammalian target of rapamycin (mTOR) activator MHY1485 blocked the antiproliferative activity of PV by regulating mTOR, unc-51-like autophagy activating kinase 1 (ULK1), autophagosomes formation, and autophagy-related proteins. The adenosine monophosphate-activated protein kinase (AMPK) inhibitor compound C attenuated PV-induced inhibition of mTOR. Our results suggest that PV inhibits the growth of PTC in vivo and in vitro via autophagy, which is associated with the AMPK/mTOR/ULK1 pathway. Thus, PV has the potential to function as a therapeutic agent against PTC.
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