mTORC1 is a target of nordihydroguaiaretic acid to prevent breast tumor growth in vitro and in vivo
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Nordihydroguaiaretic acid (NDGA) is a natural phenolic compound isolated from the creosote bush Larrea divaricata, which has anti-tumor activities both in vitro and in vivo. Its analogs are in clinical development for use in refractory solid tumors. But the mechanisms underlying the anti-cancer effect of NDGA are not fully understood. In this study, we identified mammalian target of rapamycin complex 1 (mTORC1) as a target of NDGA both in cultured breast cancer cells and in xenograft models. NDGA effectively inhibited basal level of mTORC1 but not mTORC2 activity in breast cancer cell lines. NDGA also suppressed mTORC1 downstream signaling such as expression of cyclin D1, hypoxia-inducible factor-α and VEGF, and prevented proliferation in breast cancer cells. Although NDGA stimulated AMP-activated protein kinase (AMPK)/tuberous sclerosis complex 2 (TSC2) signaling, which negatively regulates mTORC1, AMPK and TSC2 deletion could not diminish the inhibition of mTORC1 by NDGA. Subsequent studies revealed that NDGA may also direct target mTORC1 complex because NDGA suppressed amino acids- and insulin-stimulated mTORC1 and acted like rapamycin to disrupt mTOR–Raptor interaction. Most importantly, NDGA repressed breast tumor growth and targeted mTORC1 and its downstream signaling in xenograft models. Together our data provide a novel mechanism for NDGA activity which could help explain its anti-cancer activity. Disruption of mTOR–Raptor complex and activation of AMPK/TSC signaling may contribute to inhibitory effects of NDGA against mTORC1. Our data also raise the possibility that NDGA, as an mTORC1 inhibitor, may have a broad spectrum of action on breast cancers.
KeywordsNordihydroguaiaretic acid Mammalian target of rapamycin complex 1 Breast cancer Raptor AMP-activated protein kinase Tuberous sclerosis complex 2
The authors greatly appreciate the gift of TSC2+/+ and TSC2−/− MEFs from Dr. David J. Kwiatkowski (Brigham and Women’s Hospital). This work was supported by the State Key Development Program for Basic Research of China (2009CB 918904, 2013CB 945203), Program for Changjiang Scholars and Innovative Research Team in University (IRT1142), and National Natural Sciences Foundation of China (30900555 and 91029727).
Conflict of interest
The authors declared no conflict of interest.
- 7.Meyer GE, Chesler L, Liu D, Gable K, Maddux BA, Goldenberg DD, Youngren JF, Goldfine ID, Weiss WA, Matthay KK, Rosenthal SM (2007) Nordihydroguaiaretic acid inhibits insulin-like growth factor signaling, growth, and survival in human neuroblastoma cells. J Cell Biochem 102(6):1529–1541PubMedCrossRefGoogle Scholar
- 11.Youngren JF, Gable K, Penaranda C, Maddux BA, Zavodovskaya M, Lobo M, Campbell M, Kerner J, Goldfine ID (2005) Nordihydroguaiaretic acid (NDGA) inhibits the IGF-1 and c-erbB2/HER2/neu receptors and suppresses growth in breast cancer cells. Breast Cancer Res Treat 94(1):37–46PubMedCrossRefGoogle Scholar
- 21.Awada A, Cardoso F, Fontaine C, Dirix L, De Greve J, Sotiriou C, Steinseifer J, Wouters C, Tanaka C, Zoellner U, Tang P, Piccart M (2008) The oral mTOR inhibitor RAD001 (everolimus) in combination with letrozole in patients with advanced breast cancer: results of a phase I study with pharmacokinetics. Eur J Cancer 44(1):84–91PubMedCrossRefGoogle Scholar
- 30.Inoki K, Ouyang H, Zhu T, Lindvall C, Wang Y, Zhang X, Yang Q, Bennett C, Harada Y, Stankunas K, Wang CY, He X, MacDougald OA, You M, Williams BO, Guan KL (2006) TSC2 integrates Wnt and energy signals via a coordinated phosphorylation by AMPK and GSK3 to regulate cell growth. Cell 126(5):955–968PubMedCrossRefGoogle Scholar
- 35.Zavodovskaya M, Campbell MJ, Maddux BA, Shiry L, Allan G, Hodges L, Kushner P, Kerner JA, Youngren JF, Goldfine ID (2008) Nordihydroguaiaretic acid (NDGA), an inhibitor of the HER2 and IGF-1 receptor tyrosine kinases, blocks the growth of HER2-overexpressing human breast cancer cells. J Cell Biochem 103(2):624–635PubMedCrossRefGoogle Scholar