| Objective: Gastric cancer is a common malignant cancer, metastasis and reoccurrence are the most dangerous stage of its process. With further understanding for the metastatic pattern of gastric cancer, aggressive lymph node dissection and combined devisceration were carried out to treat this disease, and lymphatic metastasis and local recurrence have decreased in a great degree. However, the problem of peritoneal seeding after gastric cancer radical dissection is more and more serious, and become one of the biggest obstacles in the treatment of gastric cancer. In advanced gastric cancer, peritoneal metastasis is the most frequent (50%) type of recurrence after curative resection, as well as the death cause of most patients. The mechanism of peritoneal seeding of gastric cancer is not definite, and effective prevent and cure methods are not available. JAK-STAT(Janus kinase-signal transducer and activator of transcription) signaling pathway has been paid close attention recently. The abnormal activation of STAT3 had been observed in a variety of human malignancies development, including breast cancer, prostatic carcinoma, lung cancer and so on, but the relationship between JAK-STAT pathway and the generation and development of gastric cancer is recognized recently. Whether the activated JAK-STAT pathway could affect peritoneal seeding and metastasis of gastric cancer or not, and what downstream genes regulated by JAK-STAT pathway could induce the appearance of cancer cells invasive phenotype are not known. So, cancerous ascites or peritoneal irrigating solution of gastric cancer patients were collected. The expressions of STAT3 of cells in those samples were detected, and the relationships between the expression level and clinicpathologic parameter of tumors or surgery methods were investigated firstly. Secondly, the STAT3 decoy oligonucleotide was trasnsfected into gastric cancer cells MKN45 to block the activated STAT3 protein especially, and the repressive effects were observed. Finally, the animal model of peritoneal implantation was established in nude mice, changes of implantation capacity and the expressions of relative regulative factors in gastric cancer cells were observed. The study is to reveal the mechanism of STAT3 signals upon the course of gastric cancer peritoneal seeding, and provide new clinical thoughts and basement for tumor prevention and cure.Methods: (1) 66 peritoneal irrigating solution samples of tumor patients and 12 innocent ones were collected, peritoneal lavage cytology was used to exam the exfoliated cancer cells, nested RT-PCR was employed to detect the expression of STAT3 mRNA and CEA mRNA in samples, meanwhile relationships between STAT3 mRNA, CEA mRNA expression and relative clinico-pathological parameters were evaluated. (2) STAT3 specific decoy ODN was designed and transfected into MKN45 cells using Lipofectamine liposomal transfection reagent. The expressions of p-STAT3 protein were detected by western blot, meanwhile changes of STAT3 DNA binding activity were detected by Electrophoretic Mobility Shift Assay (EMSA). (3) The tumor animal peritoneal implantation model was established in nude mice, the capability of cancer cell's peritoneal seeding in nude mice was observed after transfection, changes in cellular proliferation activity, cellular affinity and the invasive and metastatic potentials in vitro after transfection were observed too. Then the expressions of E-cadherin, ICAM-1, CD44v6 and MMP-2/-9 in four groups were detected respectively using flowcytometry and cellular immunohistochemistry technology.Results: (1) The positive rate of PLC was 31.8%, the positive rate of CEA mRNA and STAT3 mRNA by nested RT-PCR were 48.48% and 43.94% respectively. There was a significant difference between the positive ratio of CEA mRNA, STAT3 mRNA and that of PLC (P = 0.000). With the degree of histologic differentiation of gastric cancer be more poor, depth of invasion increased, stage of TNM upgraded or lymph node metastasis appeared, positive rate of CEA mRNA and STAT3 mRNA in peritoneal lavage increased significantly (P < 0.05 or P < 0.01), meanwhile there was positive correlations between the expression of CEA mRNA and STAT3 mRNA(r = 0.999,P < 0.001). There was no significant difference about the expression of CEA mRNA and STAT3 mRNA in peritoneal lavage samples between open and laparoscope's groups. (2) After the transfection of STAT3 Decoy ODN into the gastric cancer cells, tumor cells` proliferation was inhibited in a time-dependent matter. Among the distribution of cell cycle, the ratio of G0/G1 was increased and the one of S and G2/M were decreased, the proliferation index was also decreased obviously (P < 0.05). After the transfection of STAT3 Decoy ODN into the MKN45 cells, the expression of activated p-STAT3 protein in nucleus was not different from the control group cells (P > 0.05), and there was a significant difference for STAT3 DNA-binding activity of nucleus protein between the Decoy ODN transfected group and the control group. (3) The gastric cancer cells peritoneal seeding model was observed, there were significant difference in volume of ascitic, tumor max diameter, max weight, quantity of tumor between the Decoy ODN transfected group and the control group (P < 0.05). There were also significant difference in survival time, survival ratio, survival prolonged ratio between two groups (P < 0.05). Among the distribution of cell cycle, the rate of G0/G1 was increased and the one of S and G2/M stages were decreased, the proliferation index is also decreased obviously (P < 0.05). The migrative and invasive ability of transfected MKN45 cells in vitro were decreased in some degree (P < 0.05 or P < 0.01). The expression of E-cadherin protein in transfected cells was higher than that of in control cells (P < 0.05), the expression of ICAM-1,CD44v6,MMP-2/MMP-9 protein in transfected cells is lower than that of in control cells (P < 0.05 or P < 0.01).Conclusions:â‘ As close correlations existed between the expression of STAT3 and the peritoneal implantation of gastric cancer, it could act as a standard for judging the invasive and metastatic state of gastric cancer and forecasting the prognostic of patients. Laparoscopic radical gastrectomy does not facilitate the peritoneal implantation of gastric cancer cells.â‘¡Positive correlations existed between the expressive intensity of STAT3 and the implantate and metastatic potentials of gastric cancer cells.â‘¢Restraint of STAT3 effects in nucleus could directly result in the impair of implantate and metastatic potentials of gastric cancer cells both in vitro and in vivo.â‘£Based on our studies and other researchers'reports, the effects of STAT3 on the implantate and metastasis of gastric cancer, mainly originated from dysfunction of the complex of E-cadherin-catenin and the up-regulated synthesis of ICAM-1,CD44v6,MMP-2/MMP-9 proteins, which were induced or promoted by STAT3 upstream.
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