Meta-Analysis Of P53 Gene Mutations And Gastric Cancer Clinicopathological Characteristics As Well As Study On The Transcriptional Regulation Of IASPP In Gastric Cancer Cell Lines

Gastric cancer remains one of the most common malignant tumors and its pathogenesis has not been fully elucidated. Inactivation of tumor suppressor genes is one of critical steps of tumorigenesis. The tumor suppressor gene p53 is frequently inactivated in gastric carcinoma by loss of heterozygosity (LOH) and gene mutations. In addition, the dysfunction mechanisms of wild-type P53 gene in carcinogenesis have been explored intensively. The present study includes the following two parts:PARTâ… META-ANALYSIS OF P53 GENE MUTATIONS AND CLINICOPATHOLOGICAL FEATURES IN PATIENTS WITH GASTRIC CANCERBackground and purpose P53 gene mutations have an important role of development in gastric cancer (GC). Studies investigating the relationship of P53 gene mutations and gastric cancer clinicopathological features report conflicting results. The objective of this study was to quantitatively summarize the evidence for such a relationship.Material and methodsTwo investigators independently searched the literature published in the Chinese Biomedical Literature Database (CBM), PUBMED, EMBASE, and ISI Web of Knowledge database and other literature until to 2010. We systematically reviewed all original articles that analyzed the role of P53 gene mutations in patients with gastric cancer. Information was carefully extracted from eligible studies independently including age, gender, tumor size, clinical staging, histological type, differentiation, metastasis, HP infection, etc. All statistical analysis was performed using the statistical software Stata10.0.ResultsWe identified 30 studies that met the inclusion criteria including 2674 cases of gastric cancer patients. Of these, 884 cases (33.06%) showed P53 mutations, and 1790 cases (66.94%) showed wild-type p53. The frequency of P53 gene mutation in gastric cancer was 0.3442 (95% CI 0.181-0.5074). The combined results based on all studies showed that there was a significant association of P53 gene mutations in gastric cancer and tumor stage (early, advanced), Laurèn's type, metastasis. The combined ORs for P53 mutation in early gastric cancer, advanced gastric cancer, intestinal type, diffuse type, GC with lymph node metastasis and GC with distant metastasis were 0.6 (95% CI 0.45-0.80), 1.66 (95% CI 1.25-2.21), 1.93 (95% CI 1.53 -2.44), 0.55 (95% CI 0.42-0.71), 1.46 (95% CI 1.02-2.10) and 2.72 (95% CI 1.21-6.09), respectively. Meta-analysis showed that there was no association between P53 mutation and sex, tumor location and differentiation of GC. Further study is needed for the association between P53 mutation and age, TNM stage and HP infection of GC.ConclusionsThe rate of P53 gene mutation in gastric carcinoma accounts for about one-third, and most patients is still with wild-type P53 gene. P53 gene mutations in gastric cancer correlated with tumor stage and metastasis, suggesting that P53 gene mutations have a role in the progress of gastric cancer. This study helps to understand the relationship of P53 gene mutation and clinical features of gastric cancer in a whole, and provide the basis date for further explore the role of P53 pathway in the development of gastric cancer. PARTâ…¡PRELIMINARY STUDY ON THE TRANSCRIPTIONAL REGULATION OF IASPP----A KEY INHIBITOR OF P53 IN GASTRIC CANCER CELL LINESBackground and ObjectiveInactivation of p53 is a crucial step in development and progression of gastric cancer. Previous study showed that iASPP protein could inhibit the apoptotic function of p53, leading to abnormal cell proliferation and tumorigenesis. However, regulation mechanism of iASPP expression is unclear. Transcription factor KLF4, one of the tumor suppressor genes in gastric mucosa, could interaction with P53. Also, KLF4 and iASPP have a common subcellular localization. Thus we hypothesize that KLF4 could regulate the expression of iASPP in stomach. We conducted to explore whether KLF4 could regulation the transcriptional expression of iASPP.MethodsBioinformatics prediction was used to scan cis-acting elements in iASPP promoter. Three gastric cancer cell lines (AGS, MKN-45, and SGC-7901) and one non-malignant gastric cell line (GES-1) were cultured in RPMI1640 with 10% fetal bovine serum. Expression of KLF4 and iASPP in gastric cancer cell lines and GES-1 were measured by RT-PCR. The correlation of their expression was analyzed by statistical method. Human iASPP promoter DNA was amplified by PCR. The 1.3 kilobase pairs of iASPP promoter DNA was ligated into pMD 18-T vector. The pGL3-Basic vector was used to construct the expression vectors by subcloning PCR-amplified DNA of the iASPP promoter into the kpnI/HindIII site of the pGL₃-Basic vector (pGL₃-iASPP-PRO). Then Gastric cancer cell line was co-transfected with iASPP promoter constructs and KLF4 expression vector for luciferase assays.ResultsBioinformatics analysis showed that KLF4 was a potential transcription factor of iASPP gene. RT-PCR results showed that the iASPP mRNA expression was significantly higher in SGC7901 and MKN45 than in GES-1; the KLF4 mRNA expression was lower in AGS and MKN45 than in GES-1. The KLF4 mRNA expression was inversely correlated with the iASPP mRNA expression in MKN45 and GES-1. The iASPP promoter activity was reduced by Transient Transfection of cells with KLF4 expression vector.ConclusionsOur preliminary results indicate that that KLF4 is a negative regulatory factor of iASPP gene at the transcriptional level by Luciferase assays in MKN45. Interactions among KLF4, iASPP and P53 may be one of the mechanisms of gastric tumorigenesis with wild-type P53.