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Previous data have shown that the type II cGMP‑dependent protein kinase (PKG II) inhibits the EGF‑induced MAPK signaling pathway. In order to thoroughly investigate PKG, it is necessary to elucidate the function of another type of PKG, PKG I. The aim of this study was to investigate the possible inhibitory effect of PKG II and PKG I activity on the basic fibroblast growth factor (bFGF)‑induced proliferation and migration of U251 human glioma cells and the possible underlying mechanisms. U251 cells were infected with adenoviral constructs encoding cDNA of PKG I (Ad‑PKG I) or PKG II (Ad‑PKG II) to increase the expression levels of PKG I or PKG II and then treated with 8‑Br‑cGMP and 8‑pCPT‑cGMP, respectively, to activate the enzyme. An MTT assay was used to detect the proliferation of the U251 cells. The migration of the U251 cells was analyzed using a Transwell migration assay. Western blot analysis was used to detect the phosphorylation/activation of the fibroblast growth factor receptor (FGFR), MEK and ERK and the nuclear distribution of p-ERK. The results showed that bFGF treatment increased the proliferation and migration of U251 cells, accompanied by increased phosphorylation of FGFR, MEK and ERK. Furthermore, the nuclear distribution of p-ERK increased following bFGF treatment. Increasing the activity of PKG II through infection with Ad-PKG II and stimulation with 8-pCPT-cGMP significantly attenuated the aforementioned effects of the bFGF treatment, while increased PKG I activity did not inhibit the effects of bFGF treatment. These data suggest that increased PKG II activity attenuates bFGF‑induced proliferation and migration by inhibiting the MAPK/ERK signaling pathway, whereas PKG I does not.

The scaffold protein IQGAP1 is closely related to certain Rho GTPases. Research has revealed that IQGAP1 acts as an effector of Cdc42 and Rac1 in the regulation of cell activity such as proliferation and migration. However, whether IQGAP1 is associated with RhoC, another important Rho GTPase, is unclear. Previous results from our laboratory indicated that IQGAP1 and RhoC are highly expressed in gastric cancer tissues and cells. This study was designed to investigate the possible interaction between IQGAP1 and RhoC in the regulation of the migration of cancer cells. The expression of IQGAP1 and RhoC in gastric cancer tissues and cell lines was detected by Western blotting. siRNAs targeting IQGAP1 or RhoC were transfected into gastric cancer cells to knock down the expression of the proteins. Adenoviral constructs encoding full length IQGAP1, the C‑terminal fragment of IQGAP1, and the constitutively active RhoC gene were used to infect gastric cancer cells to increase the expression of the proteins. The migratory activity of a gastric cancer cell line was measured by a transwell migration assay. Western blotting revealed that the IQGAP1 and RhoC proteins were highly expressed in gastric cancer tissues and cells. Spearman's rank correlation analysis indicated that the increases in the expression of IQGAP1 and RhoC were closely correlated. The transwell migration assay revealed that both IQGAP1 and RhoC stimulated the migration activity of the gastric cancer cell line AGS. The knockdown of IQGAP1 expression by siRNA blocked the migration‑stimulating activity of RhoC, while the knockdown of RhoC expression had no effect on the migration-stimulatory activity of IQGAP1. Co-IP results showed that RhoC and IQGAP1 bound to each other. These results reveal a previously unrecognized interaction between IQGAP1 and RhoC, and demonstrate that IQGAP1 is a downstream effector of RhoC in the regulation of the migration activity of gastric cancer cells.

Vasodilator stimulated phosphoprotein (VASP) is known as an actin-binding protein. The phosphorylation of VASP plays an important role in its function. In a previous study, serine 157 phosphorylated VASP (p-VASP S157) was shown to be co-localized with α-tubulin on the spindle of SGC-7901 cells. In the present study, we demonstrated that the level of p-VASP S157 increases and has a peak which coincides with serine 10 phosphorylated histone 3 (p-H3 S10) during mitotic progression in a human cervical cancer cell line (HeLa cells). Application of protein kinase A inhibitor H89, protein kinase G inhibitor KT5823 and protein kinase C inhibitor Go6983, or a combination of these inhibitors, caused a partial decrease in p-VASP S157 and a delay in G2/M progression. Depletion of p-VASP S157 by VASP siRNA resulted in an increase in binucleated cells and x4n cells, a further delay in G2/M progression and the inhibition of HeLa cell proliferation. These results suggest that p-VASP S157 may play an important role in the G2/M transition and the completion of cytokinesis in HeLa cells.

Our previous studies have demonstrated that the expression and activity of protein kinase G (PKG) II are significantly lower in human gastric cancer cell lines than in normal cells. This study was designed to investigate the effect of PKG II activation on the proliferation of human cultured BGC-823 gastric cancer cells. An adenoviral construct encoding the PKG II gene (Ad-PKG II) was used to infect BGC-823 cells, and the activity of the enzyme was induced by cGMP analogue 8-pCPT-cGMP. The proliferation-inhibitory effect of PKG II was analyzed by the MTT assay, BrdU incorporation assay and detection of proliferating cell nuclear antigen (PCNA) expression. Colony formation in soft agarose was performed to analyze the effect of PKG II on the anchorage-independent growth of the cells. The effect of PKG II in vivo was investigated in an immunocompromised nude mice model, and its effect on the cell cycle was analyzed by flow cytometry. The results showed that Ad-PKG II infection increased the expression of PKG II in BGC-823 cells. The activation of PKG II by 8-pCPT-cGMP caused a significant decrease in the number of live cells and inhibited DNA synthesis in individual cells. PKG II activation inhibited the EGF-induced increase in PCNA expression. The activation of PKG II also caused a significant inhibition of colony formation in soft agarose and significantly suppressed the in vivo growth of BGC-823 cells in immunocompromised nude mice. There was substantial cell arrest at the G1 phase and a decrease in the number of S phase cells in the Ad-PKG II/8-pCPT-cGMP-treated cells. These data indicate that the activation of PKG II by 8-pCPT-cGMP inhibits the proliferation of human gastric cancer cells.