Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 21, 2016; 22(15): 3992-4001
Published online Apr 21, 2016. doi: 10.3748/wjg.v22.i15.3992
CacyBP/SIP nuclear translocation regulates p27Kip1 stability in gastric cancer cells
Ying-Lin Niu, Ya-Jun Li, Jing-Bo Wang, Yuan-Yuan Lu, Zhen-Xiong Liu, Shan-Shan Feng, Jian-Guo Hu, Hui-Hong Zhai
Ying-Lin Niu, Department of Gastroenterology, Beijing Friendship Hospital Affiliated to Capital Medical University, Beijing 100050, China
Ya-Jun Li, Shan-Shan Feng, Jian-Guo Hu, Hui-Hong Zhai, Department of Digestive Diseases, General Hospital of Ningxia Medical University, Yinchuan 750004, Ningxia Hui Autonomous Region, China
Jing-Bo Wang, Yuan-Yuan Lu, Zhen-Xiong Liu, State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi’an 710032, Shaanxi Province, China
Author contributions: Niu YL, Hu JG and Zhai HH conducted laboratory studies, prepared figures and tables and drafted the manuscript; Li YJ and Wang JB conducted Western blot and co-IP; Liu ZX conducted cell cycle analysis; Lu YY and Feng SS constructed truncated fusion protein and transfected cells; all authors read and approved the manuscript.
Supported by the National Natural Science Foundation of China, No. 81072040; and the Specialized Research Fund for the Doctoral Program of Ningxia Medical University.
Institutional review board statement: The study was reviewed and approved by General Hospital of Ningxia Medical University Review Board.
Conflict-of-interest statement: The authors declare that they have no conflicts of interest.
Data sharing statement: Technical appendix, statistical code and dataset available from the corresponding author at zhaihuihong@263.net. Participants have informed consent for data sharing.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Hui-Hong Zhai, MD, PhD, Department of Digestive Diseases, General Hospital of Ningxia Medical University, 804 Shengli Street, Xingqing Area, Yinchuan 750004, Ningxia Hui Autonomous Region, China. zhaihuihong@263.net
Telephone: +86-951-6744442 Fax: +86-951-4082981
Received: May 23, 2015
Peer-review started: May 25, 2015
First decision: August 26, 2015
Revised: November 10, 2015
Accepted: December 12, 2015
Article in press: December 14, 2015
Published online: April 21, 2016
Processing time: 315 Days and 20.5 Hours
Abstract

AIM: To investigate the mechanism of calcyclin binding protein/Siah-1 interacting protein (CacyBP/SIP) nuclear translocation in promoting the proliferation of gastric cancer (GC) cells.

METHODS: The effect of CacyBP/SIP nuclear translocation on cell cycle was investigated by cell cycle analysis. Western blot analysis was used to assess the change in expression of cell cycle regulatory proteins and proteasome-mediated degradation of p27Kip1. Co-immunoprecipitation (co-IP) analysis was performed to examine the binding of CacyBP/SIP with Skp1. A CacyBP/SIP truncation mutant which lacked the Skp1 binding site was constructed and fused to a fluorescent protein. Subsequently, the effect on Skp1 binding with the fusion protein was examined by co-IP, while localization of fluorescent fusion protein observed by confocal laser microscopy, and change in p27Kip1 protein expression assessed by Western blot analysis.

RESULTS: CacyBP/SIP nuclear translocation induced by gastrin promoted progression of GC cells from G1 phase. However, while CacyBP/SIP nuclear translocation was inhibited using siRNA to suppress CacyBP/SIP expression, cell cycle was clearly inhibited. CacyBP/SIP nuclear translocation significantly decreased the level of cell cycle inhibitor p27Kip1, increased Cyclin E protein expression whereas the levels of Skp1, Skp2, and CDK2 were not affected. Upon inhibition of CacyBP/SIP nuclear translocation, there were no changes in protein levels of p27Kip1 and Cyclin E, while p27Kip1 decrease could be prevented by the proteasome inhibitor MG132. Moreover, CacyBP/SIP was found to bind to Skp1 by immunoprecipitation, an event that was abolished by mutant CacyBP/SIP, which also failed to stimulate p27Kip1 degradation, even though the mutant could still translocate into the nucleus.

CONCLUSION: CacyBP/SIP nuclear translocation contributes to the proliferation of GC cells, and CacyBP/SIP exerts this effect, at least in part, by stimulating ubiquitin-mediated degradation of p27Kip1.

Keywords: Calcyclin binding protein/Siah-1 interacting protein; Gastric cancer; Cell cycle; P27kip1; Ubiquitin

Core tip: Calcyclin binding protein/Siah-1 interacting protein (CacyBP/SIP) is a component of the ubiquitination pathway. Our study showed that defects in G1 arrest led to an increase in embryonic fibroblast growth rate in SIP-/- mice, and CacyBP/SIP could promote G1/S transition of pancreatic cancer cells and regulate the glucose limitation-induced p27 degradation. In gastric cancer (GC) tissue, CacyBP/SIP was identified to be expressed in the nuclei and could translocate into the nucleus after induction with gastrin and promote cell proliferation; however, the mechanism remains unclear. In the present investigation, the mechanism of CacyBP/SIP nuclear translocation in promoting the growth of GC cells was studied.