Aquaporin 9 inhibits hepatocellular carcinoma through up-regulating FOXO1 expression
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Chuan-Fei Li1,*, Wen-Guang Zhang1,*, Min Liu1,*, Lie-Wang Qiu2, Xiao-Feng Chen3, Lin Lv1, Zhe-Chuan Mei1
1Department of Gastroenterology, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
2Department of Gastroenterology, Yongchuan Hospital, Chongqing Medical University, Chongqing, China
3The First Branch of The First Affiliated Hospital, Chongqing Medical University, Chongqing, China
*These authors contribute equally to this work
Zhe-Chuan Mei, email: firstname.lastname@example.org
Keywords: liver cancer, aquaporin 9, cell cycle, apoptosis, FOXO1
Received: March 23, 2016 Accepted: June 03, 2016 Published: June 17, 2016
Aquaporin 9 (AQP9) is the main aquaglyceroporin in the liver. Few studies have been performed regarding the role of AQP9 in liver cancer. Here we report AQP9 expression and function in liver cancer. We found that AQP9 mRNA and protein levels were reduced in human hepatocellular cancer compared to the para-tumor normal liver tissues. Human hepatoma cell line SMMC7721 expressed low basal levels of AQP9. When AQP9 was overexpressed in SMMC7721 cell line, cell proliferation was inhibited due to cell cycle arrest at G1 phase and increased apoptosis. At the molecular level, AQP9 overexpression decreased the protein levels of phosphatidylinositol-3-kinase (PI3K), leading to reduced phosphorylation of Akt. Subsequently, the protein levels of forkhead box protein O1 (FOXO1) were increased, resulting in down-regulation of proliferating cell nuclear antigen (PCNA) expression and up-regulation of caspase-3 expression. AQP9 overexpression inhibited growth of subcutaneously xenografted liver tumors in nude mice. These findings suggest that AQP9 expression is down-regulated in liver cancer compared to the normal liver tissue and restoration of AQP9 expression can inhibit development of liver cancer.
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