Abstract
Tumor-induced angiogenesis is essential for invasive growth and hematogenous metastasis of adenoid cystic carcinoma (ACC), a highly aggressive neoplasm mostly occurring in salivary glands. Previous studies have indicated that strategies directed against angiogenesis will help develop new therapeutic agents for ACC. The Chinese folk medicine licorice has been used for years as a natural remedy for angiogenesis-related diseases. In this study, we examined the effects of isoliquiritigenin (ISL), a flavonoid isolated from licorice, on the growth and viability of ACC cells and observed a concentration-dependent (0–20 μM) inhibition of cell growth without cell death at 24 h. In a further mimic coculture study, ISL effectively suppressed the ability of ACC cells to induce in vitro proliferation, migration, and tube formation of human endothelial hybridoma (EAhy926) cells as well as ex vivo and in vivo angiogenesis, whereas it exerted no effect on EAhy926 cells when added directly or in the presence of vascular endothelial growth factor (VEGF). The data also showed that the specific suppression of tumor angiogenesis by ISL was caused by down-regulation of mammalian target of rapamycin (mTOR) pathway-dependent VEGF production by ACC cells, correlating with concurrent activation of c-Jun NH2-terminal kinase (JNK) and inhibition of extracellular signal-regulated kinase (ERK). Most importantly, ISL also significantly decreased microvessel density within xenograft tumors, associating with the reduction of VEGF production and suppression of the mTOR pathway coregulated by JNK and ERK, as revealed by immunohistochemical studies and clustering analysis. Taken together, our results highlight the fact that ISL is a novel inhibitor of tumor angiogenesis and possesses great therapeutic potential for ACC.
Footnotes
This study was supported in part by the National Natural Science Foundation of China [Grants 30872894, 30973330, 30801305] (to Y.F.Z. and J.J.); and the National Undergraduate Innovative Experiment Project [Grant 091048654] (to G.C.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.167692.
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ABBREVIATIONS:
- ACC
- adenoid cystic carcinoma
- ISL
- isoliquiritigenin
- VEGF
- vascular endothelial growth factor
- mTOR
- mammalian target of rapamycin
- ERK
- extracellular signal-regulated kinase
- MAPK
- mitogen-activated protein kinase
- JNK
- c-Jun NH2-terminal kinase
- NSG
- normal salivary gland
- TSC
- tuberous sclerosis complex
- NF-κB
- nuclear factor-κB
- PBS
- phosphate-buffered saline
- p
- phospho
- MVD
- microvessel density
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- CM
- conditioned medium
- CAM
- chick chorioallantoic membrane
- RT
- reverse transcription
- PCR
- polymerase chain reaction
- bFGF
- basic fibroblast growth factor
- G-CSF
- granulocyte colony-stimulating factor
- PDGF
- platelet-derived growth factor
- ELISA
- enzyme-linked immunosorbent assay
- PI3K
- phosphatidylinositol 3-kinase
- IKK
- IκBα kinase
- GSK
- glycogen synthetase kinase
- SP600125
- anthra(1,9-cd)pyrazol-6(2H)-one-1,9-pyrazoloanthrone
- PD98059
- 2′-amino-3′-methoxyflavone.
- Received March 11, 2010.
- Accepted May 17, 2010.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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