| Background and Aim:Gastric cancer is the fifth most common malignant tumor in the world, leading to the third tumor associated death,nearly one million new cases increasing per year.Seventy percent of the financial burden falls in the developing countries, especially in Asia. Hp infection is the main risk factor of gastric cancer. A large number of researches have demonstrated that Hp plays important roles in the initiation and the progression of the gastric mucosal canceration the process of which include the chronic atrophic gastritis, intestinal metaplasia, dysplasia and gastric cancer.However, the underlying mechanism of Hp infection in gastric cancer still remains unclear. Most related studies revealed that the NF-κB signal pathway is activated after the infection of Hp, which subsequently is closely related with the gastritis,gasric ulcer and the incidence, development, survival and prognosis of gastric cancer.NF- κ B is an important multifunctional nuclear transcription factor. In the resting state,the NF-κB dimer p50/p65 combines with the inhibitory proteins IκB to form a complexand exsit in the cytoplasm in an inactivated state. Many extracellular stimuli lead to the phosphorylation of IκB proteins and promote their ubiquitination and subsequent degradation by proteasome. This process leads to the translocation of p65 from the cytoplasm to the nucleus, where it initiates the transcription of a series of target genes. Then it plays an important role in the inflammation、immunity and tumor. Therefore, it may provide new thought for the prevention of clinical gastric cancer by illustrating the exact activating and regulating mechnism of NF-κB signal pathway after Hp infection.Recent research revealed that RACK1 was a new negative regulator of NF-κB signal pathway and could inhibit gastric cancer as a suppressor gene, and it could interact with the Vac A which is a virulence factor of Hp. Moreover,studies have confirmed the NF- κ B could induce the expression of RACK1 and RACK1 is adownstream gene of the NF-κB, which could promote cell survival. Therefore, we speculate RACK1 may play a role in the activation of NF- κ B signal pathway induced by Hp infection. For our hypothesis, our subject would adopt the immunohistochemical detect the human gastric mucosa cancerous tissue, aiming to preliminarily discuss the expression of RACK1 and NF- κ B signaling pathway related protein in Hp infection and their correlation analysis. Moreover, we further have a validation in the experiment of cells wherther the trend of the expression of RACK1 and NF- κ B signaling pathway related proteins is consistent with the organisation after Hp infection. If the experiment come to the desired, it can provide new idea and reliable theoretical basis for further clarify the Hp carcinogenic mechanism.Methods:1. Immunohistochemical analysis of the RACK1, IκBα and p-IκBα proteins in different gastric mucosal injury tissues.2. After incubation with Hp at a MOI of 50 for 0h, 30 min, 45 min, 1h, 3h or 6h in GES-1, Western blot were applied to detect the expression level of RACK1 and NF-κB related proteins.Results:1. The expression of RACK1、IκBα and p-IκBα in different stages of gastric lesions and the correlation analysis.(1) The expression of RACK1: The highest level of RACK1 were observed in GNAC, with the progess of gastric lesions, the expression of RACK1 show a decreasing trend(p<0.01). The expression of RACK1 was low in EGC and AGC and no significant difference was found(75% vs 62.5%,p>0.05). When the CNAG and the precancerous lesions(IM and Dys) were devided into Hp positive sub-group and Hp negative sub-group, significant difference was shown in the other stages of gastric lesion(100% vs 87.5%;90% vs 90%,p<0.05)and the RACK1 expression of each stage of gastric lesion showed a decreasing trend.(2) The expression of IκBα: The highest level of IκBαwas observed inGNAC, with the progess of gastric lesions, the expression of I κ B α show a decreasing trend(p<0.01). The expression of IκBαwas low in EGC and AGC and no significant difference was found(47.5% vs 45%,p>0.05). When dividing the CNAG and the precancerous lesions(IM and Dys) into Hp positive sub-group and Hp negative sub-group, significant difference was shown in the Hp positive sub-group(100% vs 72.5%,p<0.01)and the IκBαexpression showed a decreasing trend, however, the expression of IκBαshowed no significant difference in the Hp positive sub-group(85% vs 67.5%,p>0.05)The expression of p-IκBα: the expression level of p-IκBαwas highest in EGC and lowest in CNAG, and increasing from CNAG to GC. The expression level between EGC and AGC group showed no significant difference(62.5% vs 45%,p >0.05). When dividing the CNAG and precancerous lesions( IM and Dys) into Hp positive sub.group and Hp negative sub-group, the expression level in Hp negative sub-group showed no significant difference(45% vs 75%,p>0.05). But significant difference was shown in the Hp positive sub-group(40% vs 77.5%,p<0.01)and the p-IκBαexpression showed a increasing trend(3)The relationship with Hp infection:The CNAG and precancerous lesions were divided into Hp positive sub-group and negative sub-group. The result revealed the expressions of IκBαand p-IκBαhad no significant difference(p>0.05), but the expression of RACK1 in the Hp positive sub-group was higher than the Hp negatie sub-group in the two gastirc lesions and significant difference was showed(100% vs 90%;87.5 vs 90%,p<0.05).(4)The relationship of RACK1、IκBαand p-IκBαin gastric cancer tissue:The expression of RACK1 was positively associated with the expression of IκBαin gastric cancer(p<0.01),but negatively related with the expression of p-IκBα(p<0.01)。2. The expression of RACK1 and the NF-κB related proteins after incubation of Hp with GES-1 cells.The GES-1 cells were incubated with Hp at a MOI of 50 for different time points, followed by Western blot to detect the expression of RACK1, p65、p-p65(Ser536) and p-p65(Ser276). The amout of RACK1 started to accumulate 30 min postinfection with Hp(p<0.01), and reached the plateau 3 hours post infection. No obvious difference(p > 0.05) was observed for p65 expression. The expression of p-p65(Ser276) was significantly higher with Hp treated samples than that of Hp non-treated samples. The amount of p-p65(Ser276) started to accumulate 30 min post infection with Hp(p<0.01), and reached the plateau 3 hours post infection, the amout of p-p65(Ser536) reached the plateau 3 hours(p<0.01)post infection and the expression level of 6h was higher than 0h(p<0.05).Conclusions:1. The reduced expression of RACK1 and the activated NF-κB signal pathway were involved in the process of human gastric carcinogenesis.2. Hp infection associated gastric mucosal carcinogenesis could upregulate RACK1 in the early phase, which was needed to discuss whether it was involved in Hp infection associated gastric mucosal carcinogenesis or not. |
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