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Modified citrus pectin inhibited bladder tumor growth through downregulation of galectin-3

Authors: Tian Fang1, Dan-dan Liu2,3, He-ming Ning2,3,4, Dan Liu5, Jing-ya Sun2, Xiao-jing Huang5, Yu Dong2,6, Mei-yu Geng2,3,4, Shi-feng Yun1, Jun Yan5,7, Rui-min Huang2,3
1 Department of Comparative Medicine, Jinling Hospital, Clinical School of Medical College of Nanjing University, Nanjing 210002, China
2 Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
3 University of Chinese Academy of Sciences, Beijing 100049, China
4 Shanghai Tech University, Shanghai 201210, China
5 State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center of Nanjing University, Nanjing 210061, China
6 Shanghai University, Shanghai 200444, China
7 Collaborative Innovation Center of Genetics and Development, Shanghai 200438, China
Correspondence to: Shi-feng Yun: yunshifeng1@163.com, Jun Yan: yanjun@nju.edu.cn, Rui-min Huang: rmhuang@simm.ac.cn,
DOI: 10.1038/s41401-018-0004-z
Received: 25 September 2017
Accepted: 8 January 2018
Advance online: 16 May 2018

Abstract

Modified citrus pectin (MCP) is a carbohydrate enriched complex, which has been implicated in cancer treatment and prevention. However, the effects of MCP on urinary bladder cancer (UBC) are unknown. In this study, MCP was first tested in T24 and J82 human UBC cells and showed the inhibition of cell viability by the sulforhodamine B (SRB) assay. The MCP-treated UBC cells exhibited G2/M phase arrest with the decrease of Cyclin B1 and phosphorylated Cdc2. Caspase-3 was also activated, leading to the cleavage of Caspase-3 and PARP. We further explored the possible molecular mechanisms upon MCP treatment in UBC cells. Reduction of galectin-3 was observed and followed with the inactivation of Akt signaling pathway. Of note, galectin-3 knockdown by RNA interference recapitulated the MCP-mediated anti-proliferation, cell cycle arrest and apoptosis. Moreover, oral administration of MCP to the T24 xenograft-bearing nude mice inhibited the tumor growth significantly (P < 0.05). Quantification analysis of immunohistochemistry staining for Ki67 and cleaved Caspase-3 confirmed the decrease of proliferation index (P < 0.05) and the increase of apoptosis index (P < 0.01) in 700 mg/kg MCP-fed UBC xenografts. Using the information from TCGA database, we revealed that the overexpression of galectin-3 was associated with high tumor grade with lymph node metastasis, poor overall survival in UBC patients. Considering the remarkable inhibitory effects of MCP on UBC cell proliferation and survival in vitro and in vivo mainly through galectin-3, which is upregulated in UBCs, MCP may become an attractive agent, as a natural dietary fiber, for prevention and therapy of UBCs.
Keywords: modified citrus pectin; urinary bladder cancer; galectin-3; xenograft; cell survival

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