ABSTRACT
Objective: To investigate the effect of PKG II (cGMP-dependent protein kinase II) on cell proliferation-related MAPK (mitogen-activated protein kinase)/ERK (extracellular signal-regulated kinase) downstream targets RSK1 (ribosomal S6 kinase 1) and proto-oncogenes c -Jun and c -Fos in gastric cancer SGC-7901 cells. Methods: Gastric cancer SGC-7901 cells were infected with Ad-LacZ and Ad- PKG II adenovirus, and then the PKG II was overexpressed in SGC-7901 cells. These cells were treated with PKG II specific activator - 8-pCPT-cGMP [8-(p-chlorophenylthio)-cyclic GMP], and then they were stimulated with EGF (epidermal growth factor). The proliferation of SGC-7901 cells was examined by MTT method, and the mRNAs expression levels of c-Jun and c-Fos and the protein expression levels of p-RSK1, c-Jun and c-Fos were examined by RT-PCR and Western blotting, respectively. The nuclear accumulation of p-RSK1 was observed under an immunofluorescence microscope. Results: EGF-induced increase of cell proliferation and the elevation of expressions of c-Jun and c-Fos mRNAs and proteins as well as p-RSK1 (Ser380-) protein in SGC-7901 cells which were infected with PKG II were significantly inhibited after treatment with 8-pCPT-cGMP. The phosphorylation of RSK1 (Ser380) was decreased, and the accumulation of p-RSK1 (Ser380) in nuclei of SGC-7901 cells was increased after stimulation with EGF, while it was decreased after treatment with 8-pCPT-cGMP. Conclusion: Activated PKG II can inhibits the proliferation of gastric cancer cells, phosphorylation of RSK1 (Ser380), nuclear accumulation of p-RSK1(Ser380) and the expressions of c -Jun and c -Fos genes which were induced by EGF. Copyright © 2012 by TUMOR.
ABSTRACT
<p><b>BACKGROUND AND OBJECTIVE</b>Nitric oxide (NO) is involved in many physiologic and pathologic processes. As an important biologic mediator, NO has been the focus of cancer study for its function in tumorigenesis, tumor progression, and death. This study investigated the effect of NO donor sodium nitroprusside (SNP) on the growth and proliferation of gastric cancer cell line AGS.</p><p><b>METHODS</b>The growth inhibition of AGS cells was analyzed using MTT assay. The cell cycle was measured using flow cytometry. The changes of mRNA expression of proliferating cell nuclear antigen (PCNA) and caspase-3 were examined using reverse transcriptase polymerase chain reaction (RT-PCR), and the protein expressions of PCNA and caspase-3 were analyzed using Western blot.</p><p><b>RESULTS</b>Dose-dependent SNP inhibited cell growth and proliferation. When the AGS cells were treated with SNP at 100, 500, 1000, 1500, and 2000 mumol/L for 24 h, the growth inhibition rates were (2.02 +/- 2.96)%, (10.82 +/- 2.21)%, (18.95 +/- 3.35)%, (26.88 +/- 2.54)%, and (42.57 +/- 1.27)%, respectively (P < 0.05). SNP altered the cell cycle in AGS cells. Compared with the control group, treatment with SNP at 100, 500, 1000, 1500, and 2000 mumol/L for 24 h reduced the number of cells in the S phase by 2.29%, 7.8%, 11.34%, 20.49%, and 23.6%, respectively, and enhanced the number of cells in the G1/G0 phases by 3.33%, 9.3%, 13.46%, 21.37%, and 24.73%, respectively (P < 0.05). With the increasing concentration and action time of SNP, the expressions of PCNA mRNA and protein decreased. The expression of caspase-3 mRNA remained unchanged, but procaspase-3 was activated.</p><p><b>CONCLUSION</b>NO not only inhibits cell growth and proliferation, but also induces apoptosis in gastric cancer cells, and such effects of NO showed significant dose-dependent activity.</p>
