| Tumour metastasis is the process of tumour cells migrating from primary site to other areas by lymphatic vessel,blood vessel or body cavity and continuing to grow in other areas. The incidence rate of gastric cancer is the highest in malignant tumors. Its high mortality is closely related with tumour metastasis.Therefore, the reduction of the mortality of gastric cancer in advanced stages is required for its therapy.Recently,molecular targeted therapy became the first choice in the treatment of malignant tumour because of its higher pertinence and lower damaging to normal cells.The study on the roles of signal molecules in tumour metastasis could then provided the theoretical foundation for screening effective molecular targets for cancer treatment.Phosphoinositide-specific phospholipase-γ1(PLC-γ1) plays an important role in tumour metastasis. It could be activated by platelet derived growth factor (PDGF), epidermal growth factor (EGF) and (FGF) through a phophorylation mechanism. The activation mobilizes internal calcium stores and engages multiple protein kinase pathways that control or modulate cell division, transformation, differentiation, shape, motility, and apoptosis. In this study, the role of PLC-γ1in regulating the metastasis of gastric cancer cells was investigated in human gastric adenocarcinoma cell lines BGC823and SGC7901and clinical specimens.First of all, we analyzed fresh human gastric adenocarcinoma tissues,human normal gastric mucosa tissues, and tissue assay by western blotting and immunohistochemistry.The result displayed that PLC-γ1expression was higher in human gastric adenocarcinoma tissues specificially in advanced gastric adenocarcinoma tissues Which indicating the involvement of PLC-γ1in the metastasis of gastric adenocarcinoma. In order to explore the regulatory mechanism of PLC-γ1in the metastasis of gastric adenocarcinoma.Gastric cancer cells, BGC823and SGC7901were treated by the PLC-γ1inhibitor-U73122or sh-PLC-γ1,followed by the detections of cell migration, such as Wound healing and Transwell and Ruffling assay western blotting. At the same time, the expression levels of MMP9 protein and mRNA were monitored by RT-PCR and Western blotting. The results in-dicated that the migration of gastric adenocarcinoma cells par-tly depended on PLC-yl activity.In addition, the roles of IP3/Ca2+/CaMKII and DAG/PKC of PLC-yl were investigated in BGC823cells which were treated with different inhibitors CaMKII or DAG or shRNA. The results indicated that the two classical signal axises, IP3/Ca2+/CaMKII and DAG/PKC, activated ERK and up-regulated MMP9expression.Previous studies showed that Akt binded to and phosphorylated PLC-yl in response to EGF in cos-7cell line. Here, we found that although Akt couldn’t bind to PLC-γ1in BGC823cells, the reciprocal inhibition/stimulation was observed by the treatment of their inhibitors, U73122and TCN or si-PLC-γ1and si-Akt. Furthermore, the overexpression of Akt increased the expression and activity of PLC-γ1.However, the overexpression of PLC-γ1inhibited the activity of Akt. Combined with other authors’ study on the regulatory mechnisms of PLC-γ1and Akt in other cancer cells, we inferred that there is a loop between PLC-γ1and Akt:on one hand, PI3K could activate Akt and PLC stimutaneously, while Akt might serve as an upstream to regulate PLC-γ1because of the substrate sequence(S1248)in PLC-γ1; on the other hand, the overexpression of PLC-yl could negatively feedback on PI3K or Akt, leading to the inhibition of Akt activity. The result of immunochemistry in clinical specimens showed that PLC-γ1had a higher expression than Akt in lymph node metastasis of gastric carcinoma, indicating the predominance of PLC-γ1on cell migration of gastric adenocarcinoma.In conclusion, it was demonstrated that PLC-γ1was related to the dissemination of gastric adenocarcimoma. The cell migration with actin cytoskeleton reorganization partly depended on PLC-γ1activation in gastric adenocarcinoma cell line. Both of the classical downstream pathway IP3/Ca2+/CaMKII and DAG/PKC regulates cell migration by ERK/MMP9. Furthermore, there is a loop between PLC-γ1and Akt:on one hand, PI3K could activate Akt and PLC stimutaneously, while Akt might serve as an upstream to regulate PLC-γ1because of the substrate sequence(S1248)in PLC-γ1; on the other hand, the overexpression of PLC-γ1could negatively feedback on PI3K or Akt, leading to the inhibition of Akt activity. The role of the loop between PI3K or Akt in cell migration of gastric adenocarcinoma is further studied. The data suggest that PLC-yl may serve as one of targets for treatment of gastric adenocarcinoma. |
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