The Expression And Clinical Significance Of ERp57 In Gastric Cancer And The Matchen Normal Gastric Mucosa

BackgroundDespite declining incidence and mortality,gastric cancer continues to be an acute health problem,remaining the second leading cause of cancer-related deaths in the world. In our country, gastric cancer is one of the most common cancers and the first leading cause of cancer related deaths.The carcinogenisis and development of stomach is a multistep process with involvement of many factors. In the process, it is involved in different pathological changes, including the chronic superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, atypical hyperplasisa and gastric cancer.Gastric cancer can be divided into two stages according to its progression.They are the early and advanced gastric cancers.With the development and general application of endoscopic technology, more patients with early gastric cancer, which is limited to the gastric mucosa and submucosa, are discovered and have good 5-year survival rates, which is over 90%. Compared with the early gastric cancer, the advanced gastric cancer invading through the muscularis propria into serosa, which have distant metastasis in the general, results in the bad prognosis. Unfortunately, most cases of gastric cancer are diagnosed at more advanced stages where effective systemic therapy is limited. The main cause of tumor related death is invasion and distant metastasis. Therefore, early diagnosis and treatment of gastric cancer is of great importance. However, the rate of early diagonosis of gastric cancer is still low as there is no specific tumor markers for it.At present, people have discovered that expressions of more and more genes and proteins in the gastric cancer events are abnormal with the development in molecular technique of tumors.These abnormal genes and proteins are closely correlated with the depth of tumor invasion, tumor size, histological classification,clinical stage,lymph node metastasis, distant metastasis and tumor prognosis. And they will take great breakthrough in the diagonosis and prognosis of the gastric cancer. Therefore, it is of great significance to have reseaches in the carcinogenisis and progress of gastric cancer.ERp57(Endoplasmic Reticulum Protein57) is a glycoprotein specific thiol oxidoreductase that is a member of the protein disulfide isomerase (PDI) family. In the structure, this protein contains several modification sites, a putative nuclear localization, a ER retrieval sequence and a signal peptide.ERp57 mediates numerous functions.Such as participating in the quality control of newly synthesized glycoproteins,peptide loading complex of MHC classⅠmolecules and so on.ERp57 is expressed in a wide variety of tissues and organs, with difference in different regions. The gene of ERp57 can be activated in many cases,such as endoplasmic reticulum stress inducers,pathological state, microenvironment of solid tumors, glycosylation antagonist and so on. The microenvironment of solid tumors includes glucose starvation,low pH, hypoxia and so on. As is known that a core of tumor tissues are not only hypoxic but also deprived of glucose. Therefore, ERp57 is activated and highly expressed in many solid tumors.ERp57 were reported to be upregulated in esophageal squamous cell carcinoma,ovary cancer, breast cancer, lung cancer and downregulated in colon cancer and liver cancer. In the rat renal cells, the level of ERp57 was upregulated after transferd with virus oncogenes. These have vertified that ERp57 is closely correlated with the tumor events.Up to now, the researches of ERp57 in gastric cancer tissues are relatively rare at home and abroad.Celli et.al discovered that the gene expressions of ERp57 were higher in gastric cancer tissues than the matched normal gastric mucosa.However, Charles et.al reported that ERp57 protein was downregulated in gastric cancer tissues,and lower ERp57 expression in tumors did correlate with increased depth of tumor invasion and advanced clinical stage of disease. In our coutry, someone detected that ERp57 was upregulated in the blood of gastric cancer compared with the healthy ones when screening the blood biomarkers. However, there are no research on the gastric cancer tissues.Therefore, it is still of some clinical significance in rearches on the expression and distribution of ERp57 in gastric cancer,the analysis of the relationships between ERp57 expression level and the clinicopathological features of patients and the exploration of the role of ERp57 in the events and prognosis of gastric cancer. Moreover, the present results showed the discrepancy between messenger RNA and protein level for ERp57. The phenomenon has been reported in the liver cancer. They detected that its cleavage led to release of selected cleaved products in the extracellular compartment. However, the discrepancy between messenger RNA and protein level for ERp57 in gastric cancer needs furher researches. Therefore, it is necessary to have research on the messenger RNA and protein level for ERp57 in gastric cancer simultaneously.ObjectivesTo explore the role of ERp57 expression in the progress of gastric cancer and to explore a new method for treatment and prevention of gastric cancer by examining the expression and distribution of ERp57 in gastric cancer tissues and the matched normal gastric mucosa and analyzing the relationship between the expression of ERp57 in gastric cancer and the clinicopathological features of patients.Methods1. We collected gastric cancer tissues and the matched normal gastric mucosa (respectively 30 cases) underwent gastrectomy from the patients without radiation and chemotherapy in NanFang Hospital of the southern medical university. All cases have been confirmed to be gastric cancer by the pathology.2. Reverse transcriptase-PCR (RT-PCR) and Western blot were used to detect expression levels of ERp57 in gastric cancer tissues and the matched normal gastric mucosa for further analyzing the correlation between the expression of ERp57 in gastric cancer tissues and the clinicopathological features.3. Immunohistochemistry was used to detect the distribution of ERp57 in gastric cancer tissues and the matched normal gastric mucosa.4. Statistical analysis:Statistical analysis was performed using software SPSS 13.0. The values presented as mean±SD. P<0.05 was considered as significant. Statistical comparisions of the expression of ERp57 in gastric cancer tissues and the matched normal gastric mucosa was performed using Paired Sample T Test.The difference of the ERp57 protein levels among the different locations of gastric cancer was performed using ONE-WAY-ANOVNE.Others were performed using Independent-Sample T Test.Results1. In all 30 cases of gastric cancer, there were 21 cases (70%) whose messenger RNA level of ERp57 was upregulated compared to the matched normal gastric mucosa (T/N>1).1 case (3.33%) was equivalent (T/N≈1)and 8 cases (26.67%) were lowerer(T/N<1). The level of ERp57 mRNA in gastric cancer tissues and the matched normal gastric mucosa were 0.9556±0.370,0.748±0.291 repectively, with a significant difference (P<0.05).2. In all 30 cases of gastric cancer, there were 4 cases (13.33%) whose protein level of ERp57 was upregulated (T/N>1).4 cases (13.33%) were equivalen(T/N≈1) and 22 cases (73.34%) were lowerer(T/N<1). The level of ERp57 protein in gastric cancer tissues and the matched normal gastric mucosa were 0.635±0.361, 0.899±0.245 repectively, with a significant difference (P<0.05).3. The comparative expression level of ERp57 gene and protein in T1+T2 was 1.191±0.437 and 0.879±0.404, respectively. In the group of T3+T4, it was 0.870±0.311 and 0.547±0.308. The difference between these two group was significant(P<0.05). The comparative expression level of ERp57 gene and protein inⅠ±Ⅱwas 1.121±0.348 and 0.816±0.332,respectively. In the group ofⅢ+Ⅳ, it was 0.790±0.323 and 0.454±0.300,respectively. The difference between these two group was significant P<0.05).It showed that the expression level of ERp57 in gastric cancer tissues has relationship with the depth of tumor invasion and the clinical stage of tumor, and has no relationships with gender, age, tumor location,tumor size,Histological classification,local lymph nodes metastasis and distant metastasis(P>0.05).4. The positive tumor cells of ERp57 are brown. The positive signals are in the cell cytoplasm. In the matched gastric mucosa,it is expressed in the two-thirds of the gastric gland. And the positive signals are mainly in the cytoplasm of chief cells, and it is lackness or weakness of ERp57 in parietal cells.Conclusion1. ERp57 is expressed in human gastric mucosa, and is downregulated in the gastric cancer. Its expression may be correlated with the carcinogenesis and progress of gastric cancer. The expression of ERp57 in the gastric cancer may act as a potential biomarker in respect to the determination of the stage of gastric cancer and the prognosis of tumor invasion.2. The discrepancy between messenger RNA and protein level of ERp57 in gastric cancer tissues may result from its cleavage leading to release of selected cleaved products into the blood or body fluid. However, it is only a speculation, which needs furher vertifications. 3. ERp57 is mainly expressed in the cytoplasm of chief cells, however it is lackness or weakness of ERp57 in parietal cells. The differences between these two cells may be correlated with different cell functions, which suggested that ERp57 may play a role in the process of synthesis and secretion of pepsinogen.