Type II cGMP-dependent protein kinase inhibits the migration, invasion and proliferation of several types of human cancer cells

Previous studies have indicated that type II cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG II) could inhibit the proliferation and migration of gastric cancer cells. However, the effects of PKG II on the biological functions of other types of cancer cells remain to be elucidated. Therefore, the aim of the present study was to investigate the effects of PKG II on cancer cells derived from various types of human tissues, including A549 lung, HepG2 hepatic, OS-RC-2 renal, SW480 colon cancer cells and U251 glioma cells. Cancer cells were infected with adenoviral constructs coding PKG II (Ad-PKG II) to up-regulate PKG II expression, and treated with 8-(4-chlorophenylthio) (8-pCPT)-cGMP to activate the kinase. A Cell Counting kit 8 assay was used to detect cell proliferation. Cell migration was measured using a Transwell assay, whereas a terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick-end labeling assay was used to detect cell apoptosis. A pull-down assay was used to investigate the activation of Ras-related C3 botulinum toxin substrate (Rac) 1 and western blotting was used to detect the expression of proteins of interest. The present results demonstrated that EGF (100 ng/ml, 24 h) promoted the proliferation and migration of cancer cells, and it suppressed their apoptosis. In addition, treatment with EGF enhanced the activation of Rac1, and up-regulated the protein expression of proliferating cell nuclear antigen, matrix metalloproteinase (MMP) 2, MMP7 and B-cell lymphoma (Bcl)-2, whereas it down-regulated the expression of Bcl-2-associated X protein. Transfection of cancer cells with Ad-PKG II, and PKG II activation with 8-pCPT-cGMP, was identified to counteract the effects triggered by EGF. The present results suggested that PKG II may exert inhibitory effects on the proliferation and migration of various types of cancer cells.