PKGII inhibits downstream targets of proliferation-related MAPK/ERK in gastric cancer cell line SGC-7901

Objective: To investigate the effect of PKGⅡ (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 PKGⅡ was overexpressed in SGC-7901 cells. These cells were treated with PKGⅡ 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 PKGⅡ 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 PKGⅡ 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. DOI:10.3781/j.issn.1000-7431.2012.11.002