Document Detail

Overexpression of the N-terminal end of the p55gamma regulatory subunit of phosphatidylinositol 3-kinase blocks cell cycle progression in gastric carcinoma cells.
MedLine Citation:
PMID:  15809724     Owner:  NLM     Status:  MEDLINE    
pRb and its family members p130 and p107 regulate cell cycle progression and direct G1/S transition in mammalian cells through interaction with the transcription factor E2F. Phosphatidylinositol 3-kinase (PI3K) is an essential component of growth factor-regulated pathways and plays a crucial role in the regulation of cellular proliferation and differentiation. It has been demonstrated that PI3K can regulate cell cycle progression via Akt-mediated pathway. However, the possible interactions between PI3K and Rb pathways remain to be defined. It was reported that the unique 24-amino-acid N-terminal end of the p55 regulatory subunits of PI3K is an Rb-binding domain and affects Rb action or Rb-E2F interaction. The 24 N-terminal amino acids of p55gamma encoded by a cDNA construct could compete with the endogenous p55gamma for binding to Rb, which influences Rb-mediated signaling and blocks cell cycle progression. In the current study, we investigated the effects of this 24-peptide on cell proliferation in human gastric carcinoma MKN-28 cells by means of cell cycle analysis, BrdU incorporation, and determining the levels of cell cycle regulatory molecule expression. Our results showed that p55gammaPI3K and the Rb family members p130 and p107 exist in MKN-28 cells, while the p110PI3K was not detected. Moreover, p55gammaPI3K was found binding to p130/p107 in these cells. We demonstrated that the introduction of the plasmid N24p55-GFP (harboring the cDNA for the 24 N-terminal amino acids of p55gamma) into MKN-28 cells caused cell cycle arrest at G1. Furthermore, we showed that the over-expression of the 24-peptide in MKN-28 cells decreased the population of cells incorporating BrdU and reduced the levels of cyclin D1 and cyclin A. These observations suggest that PI3K can regulate cell cycle progression and cell proliferation in human gastric tumor cells via Rb-mediated pathway, and that this effect of PI3K is mediated through a direct association with Rb via the N-terminal end of its p55 kDa regulatory subunits and modulating Rb-E2F interactions. Taken together with previous studies, our data provide a new therapeutic target in human stomach cancer. Strategies targeting PI3K signal transduction or the association of PI3K with Rb, or regulating PI3K-Rb interactions could be employed for gene therapy or chemotherapy of gastric cancer and other tumors.
Junbo Hu; Shuangyou Liu; Jing Wang; Xuelai Luo; Xia Gao; Xianmin Xia; Yongdong Feng; Deding Tao; Gangduo Wang; Xiping Li; Jinshun Zhao; Hong Ding; Eddie Reed; Qingdi Q Li; Jianping Gong
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  International journal of oncology     Volume:  26     ISSN:  1019-6439     ISO Abbreviation:  Int. J. Oncol.     Publication Date:  2005 May 
Date Detail:
Created Date:  2005-04-05     Completed Date:  2005-07-12     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9306042     Medline TA:  Int J Oncol     Country:  Greece    
Other Details:
Languages:  eng     Pagination:  1321-7     Citation Subset:  IM    
Institute for Cancer Research, Tongji Hospital, Tongji Medical College, Central China University of Science and Technology, Wuhan, Hubei 430030, P.R. China.
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MeSH Terms
1-Phosphatidylinositol 3-Kinase / biosynthesis*
Carcinoma / genetics*,  pathology*
Cell Cycle / genetics*,  physiology*
Cell Proliferation
DNA, Complementary / genetics
Peptide Fragments
Retinoblastoma Protein / metabolism
Signal Transduction
Stomach Neoplasms / genetics*,  pathology*
Tumor Cells, Cultured
Grant Support
P20RR16440-010003/RR/NCRR NIH HHS
Reg. No./Substance:
0/DNA, Complementary; 0/Peptide Fragments; 0/Retinoblastoma Protein; EC 3-Kinase

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