Mammalian target of rapamycin pathway promotes tumor-induced angiogenesis in adenoid cystic carcinoma: its suppression by isoliquiritigenin through dual activation of c-Jun NH2-terminal kinase and inhibition of extracellular signal-regulated kinase.

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 microM) 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 NH(2)-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.

• Authors: Zhi-Jun Sun, Gang Chen, Wei Zhang, Xiang Hu, Cong-Fa Huang, Yu-Fan Wang, Jun Jia, Yi-Fang Zhao
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 334 Issue 2 Pg. 500-12 (Aug 2010) ISSN: 1521-0103 [Electronic] United States
• PMID: 20484154 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Angiogenesis Inhibitors
• Chalcones
• Intracellular Signaling Peptides and Proteins
• Vascular Endothelial Growth Factor A
• isoliquiritigenin
• MTOR protein, human
• mTOR protein, mouse
• Protein Serine-Threonine Kinases
• TOR Serine-Threonine Kinases
• Extracellular Signal-Regulated MAP Kinases
• JNK Mitogen-Activated Protein Kinases

Topics

• Angiogenesis Inhibitors (therapeutic use)
• Animals
• Carcinoma, Adenoid Cystic (blood supply, drug therapy, pathology)
• Cell Line, Tumor
• Cell Movement (drug effects)
• Cell Proliferation (drug effects)
• Chalcones (therapeutic use)
• Endothelial Cells (drug effects, physiology)
• Endothelium, Vascular (drug effects, physiology)
• Enzyme Activation
• Extracellular Signal-Regulated MAP Kinases (antagonists & inhibitors)
• Female
• Humans
• Intracellular Signaling Peptides and Proteins (physiology)
• JNK Mitogen-Activated Protein Kinases (metabolism)
• Mice
• Mice, Nude
• Neoplasm Transplantation
• Neovascularization, Pathologic (drug therapy, pathology)
• Protein Serine-Threonine Kinases (physiology)
• Salivary Gland Neoplasms (blood supply, drug therapy, pathology)
• TOR Serine-Threonine Kinases
• Transplantation, Heterologous
• Vascular Endothelial Growth Factor A (biosynthesis)