Gastric Cancer
Copyright ©2005 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 7, 2005; 11(1): 61-68
Published online Jan 7, 2005. doi: 10.3748/wjg.v11.i1.61
Association between endogenous gene expression and growth regulation induced by TGF-β1 in human gastric cancer cells
Xue Li, Yun-Yan Zhang, Qi Wang, Song-Bin Fu
Xue Li, Qi Wang, Song-Bin Fu, Laboratory of Medical Genetics, Harbin Medical University, Harbin 150086, Heilongjiang Province, China
Yun-Yan Zhang, Third Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China
Author contributions: All authors contributed equally to the work.
Supported by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions by Ministry of Education and the National Natural Science Foundation of China, No. 30370783 and the Key Project of Science and Technology from Heilongjiang Province, No. GB03C601-1
Correspondence to: Song-Bin Fu, Laboratory of Medical Genetics, Harbin Medical University, Harbin 150086, Heilongjiang Province, China. fusb@ems.hrbmu.edu.cn
Telephone: +86-451-86674798 Fax: +86-451-86677243
Received: February 2, 2004
Revised: February 8, 2004
Accepted: March 18, 2004
Published online: January 7, 2005
Abstract

AIM: To investigate the association between endogenous gene expression and growth regulation including proliferation and apoptosis induced by transforming growth factor-β1 (TGF-β1) in human gastric cancer (GC) cells.

METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was performed to detect the main components of the TGF-β1/Smads signal pathway in human poorly differentiated GC cell line BGC-823. Localization of Smad proteins was also determined using immunofluorescence. Then, the BGC-823 cells were cultured in the presence or absence of TGF-β1 (10 ng/mL) for 24 and 48 h, and the effects of TGF-β1 on proliferation and apoptosis were measured by cell growth curve and flow cytometry (FCM) analysis. The ultrastructural features of BGC-823 cells with or without TGF-β1 treatment were observed under transmission electron microscope. The apoptotic cells were visualized by means of the terminal deoxynucleotidyl transferase (TdT)-mediated dTUP in situ nick end-labeling (TUNEL) method. Meanwhile, the expression levels of endogenous p15,p21 and Smad7 mRNA and the corresponding proteins in the cells were detected at 1, 2 and 3 h after culture in the presence or absence of TGF-β1 (10 ng/mL) by semi-quantitative RT-PCR and Western blot, respectively.

RESULTS: The TGF-β1/Smad signaling was found to be intact and functional in BGC-823 cells. The growth curve revealed the most evident inhibition of cell proliferation by TGF-β1 at 48 h, and FCM assay showed G1 arrest accompanied with apoptosis induced by TGF-β1. The typical morphological changes of apoptosis were observed in cells exposed to TGF-β1. The apoptosis index (AI) in TGF-β1-treated cells was significantly higher than that in the untreated controls (10.7±1.3% vs 0.32±0.06%, P<0.01). The levels of p15,p21 and Smad7 mRNA and corresponding proteins in cells were significantly up-regulated at 1 h, but gradually returned to basal levels at 3 h following TGF-β1 (10 ng/mL) treatment.

CONCLUSION: TGF-β1 affects both proliferation and apoptosis of GC cells through the regulation of p15 and p21, and induces transient expression of Smad 7 as a negative feedback modulation of TGF-β1 signal. Our results suggest a novel functional role of p21 as an accelerant of TGF-β1-mediated apoptosis in GC cells.

Keywords: Gastric cancer; Transforming growth factor-β1; Apoptosis; Gene expression