A functional polymorphism T309G in MDM2 gene promoter, intensified by Helicobacter pylori lipopolysaccharide, is associated with both an increased susceptibility and poor prognosis of gastric carcinoma in Chinese patients

The mouse double minute 2 polymorphism is associated with both decreased p53 expression and poor clinicopathological outcomes of gastric cancer

This study aimed to determine the mouse double minute 2 (MDM2) SNP309 polymorphism and to evaluate MDM2 and p53 expression and the association of MDM2 positivity in gastric cancer and clinicopathological outcomes. A total of 400 patients with chronic gastritis, precancerous lesions, and gastric cancer were used to identify the MDM2 SNP309 polymorphism by using the Taq Man SNP Genotyping assay. Immunohistochemistry was performed to evaluate MDM2 and p53 expression. The associations of polymorphisms, protein expression, clinicopathological outcomes, and gastric cancer risk were calculated by multivariate Cox proportional hazards regression model analysis and expressed by odds ratios (ORs) and 95% confidence intervals (CIs). The MDM2 SNP309 G/G homozygous polymorphism was significantly associated with expressed MDM2 in gastric cancer (OR = 1.57, 95% CI = 1.39-2.03, P = 0.039). Moreover, in gastric cancer, p53 was significantly decreased compared to MDM2 (P = 0.007). However, MDM2 and p53 expression were not significantly different among genotypes, and the G/G genotype can result in the altered protein expression of p53 in gastric cancer. Clinicopathological outcome was significantly associated with MDM2 expression, including tumor location in the upper gastric region (OR = 1.48, 95% CI = 1.25-3.54, P = 0.037), undifferentiated type (OR = 2.47, 95% CI = 1.38-4.14, P = 0.016), presence of lymphatic invasion (OR = 1.96, 95% CI = 1.22-3.19, P = 0.014), and unresectable tumor (OR = 3.39, 95% CI = 1.61-4.94, P = 0.017). Our study indicated associations of the MDM2 SNP309 G/G homozygous polymorphism, MDM2 and p53 expression. Therefore, G/G-associated MDM2 revealed that P53 expression was decreased in gastric cancer and poor clinicopathological outcomes. Understanding the genetic polymorphisms and expression of MDM2 may help explain gastric cancer risk.

Association of Murine Double Minute 2 polymorphisms with gastric cancer: A systematic review with meta-analysis

Gastric cancer (GC) is the 5th most common type of cancer, with the 3rd highest mortality rate worldwide in both sexes. Murine double minute 2 (MDM2) protein is the major negative regulator of p53, and genetic polymorphisms in this gene have shown to be associated with several types of cancer. In the present study, a literature search was performed using PubMed and Scopus with the following key word combinations 'gastric cancer AND polymorphism AND MDM2'. Studies were carefully revised according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify eligible studies that matched the inclusion criteria. Statistical analysis was performed to assess the association between the different genetic polymorphisms and GC risk, by calculating the odds ratios (OR) and the confidence intervals (CI), with a 5% level of significance. A total of 11 manuscripts studied MDM2 polymorphisms in GC: rs937283 (n=1), rs3730485 (n=1) and rs2279744 (n=9). Both the rs937283 and rs3730485 reports showed an association with GC; however, there was only one study on each of these polymorphisms in the literature. A meta-analysis was performed for the rs2279744 polymorphism, of which studies showed a positive association between the G allele and risk of GC, either in the dominant model (OR=1.46; 95% CI 1.21-1.75; P<0.001) or recessive model (OR 1.65; 95% CI 1.45-1.87; P<0.001). In conclusion, genetic polymorphisms in MDM2 seemed to be associated with an increased risk of GC development, nevertheless, the number of studies were relatively low and the studied populations were primarily Chinese. The present meta-analysis emphasizes the need for additional studies in other populations to corroborate the association of these polymorphisms with GC.

Manifold role of ubiquitin in Helicobacter pylori infection and gastric cancer

Infection with H. pylori induces a strong host cellular response represented by induction of a set of molecular signaling pathways, expression of proinflammatory cytokines and changes in proliferation. Chronic infection and inflammation accompanied by secretory dysfunction can result in the development of gastric metaplasia and gastric cancer. Currently, it has been determined that the regulation of many cellular processes involves ubiquitinylation of molecular effectors. The binding of ubiquitin allows the substrate to undergo a change in function, to interact within multimolecular signaling complexes and/or to be degraded. Dysregulation of the ubiquitinylation machinery contributes to several pathologies, including cancer. It is not understood in detail how H. pylori impacts the ubiquitinylation of host substrate proteins. The aim of this review is to summarize the existing literature in this field, with an emphasis on the role of E3 ubiquitin ligases in host cell homeodynamics, gastric pathophysiology and gastric cancer.

Roles of E3 ubiquitin ligases in gastric cancer carcinogenesis and their effects on cisplatin resistance

Although gastric cancer (GC) is one of the most common cancers with high incidence and mortality rates, its pathogenesis is still not elucidated. GC carcinogenesis is complicated and involved in the activation of oncoproteins and inactivation of tumor suppressors. The ubiquitin-proteasome system (UPS) is crucial for protein degradation and regulation of physiological and pathological processes. E3 ubiquitin ligases are pivotal enzymes in UPS, containing various subfamily proteins. Previous studies report that some E3 ligases, including SKP2, CUL1, and MDM2, act as oncoproteins in GC carcinogenesis. On the other hand, FBXW7, FBXL5, FBXO31, RNF43, and RNF180 exert as tumor suppressors in GC carcinogenesis. Moreover, E3 ligases modulate cell growth, cell apoptosis, and cell cycle; thus, it is complicated to confer cisplatin resistance/sensitivity in GC cells. The intrinsic and acquired cisplatin resistance limits its clinical application against GC. In this review, we explore oncogenic and tumor suppressive roles of E3 ligases in GC carcinogenesis and focus on the effects of E3 ligases on cisplatin resistance in GC cells, which will provide novel therapeutic targets for GC therapy, especially for cisplatin-resistant patients.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

Long telomeres cooperate with p53, MDM2, and p21 polymorphisms to raise pediatric solid tumor risk

BACKGROUND

While leukocyte telomere length has been linked with altered risk in adult cancer, limited information is available on its association with risk in pediatric solid tumors. We investigated the association of telomeric alterations with risk of pediatric solid tumors. We also investigated whether altered telomeres cooperated with the TP53 rs1042522, MDM2 rs2279744 and CDKN1A (p21^cip1 ) rs1059234 single-nucleotide polymorphisms to modify cancer risk.

METHODS

A total of 101 tumor patients and 202 controls were recruited for this age- and gender-matched case-control study. Relative telomere length (RTL) was determined in peripheral blood leukocytes using quantitative real-time polymerase chain reaction (PCR), and the polymorphisms were genotyped using PCR-restriction fragment length polymorphism.

RESULTS

Using median RTL in the healthy controls as a cut-off, children with longer telomeres were at an increased risk of developing a solid tumor (OR, 2.70; P < 0.01). When participants were categorized according to control RTL quartiles, a significant dose-response relationship was observed (χ²  = 10.95; P < 0.001). The risk for tumors increased nearly threefold (P = 0.001) for the triple interaction RTL × TP53 rs1042522 × p21^cip1 rs1059234 compared with the maximum effect of any single factor, although the interaction effect was less than additive. The MDM2 rs2279744 GG genotype reduced pediatric solid tumor risk significantly (OR, 0.51).

CONCLUSION

Combined analysis of telomeres and genetic polymorphisms in the TP53 pathway can provide important clues to understanding pediatric solid tumor etiology.

Investigation of the association between the MDM2 T309G polymorphism and gastric cancer

Murine double minute clone 2 oncoprotein (MDM2) is a key component in the regulation of the tumour suppressor p53. The association between the MDM2 polymorphism and gastric cancer (GC) has been investigated in Turkish population. In the present case-control study, the aim was to investigate the association between genetic polymorphisms of the MDM2 gene (a major regulator of p53 function) and primary GC risk in a Turkish population. The polymorphism, T309G (rs2279744) in the MDM2 gene was determined in patients with GC (n=65) and in healthy control subjects (n=67) using the polymerase chain reaction-restriction fragment length polymorphism method. The findings were evaluated using logistic regression and χ² tests. No statistically significant differences were observed between the control subjects and patients with GC regarding smoking status. A comparison between GC cases and control subjects indicated a statistically significant difference for family history of cancer [odds ratio (OR)=0.17; 95% confidence interval (CI), 0.05-0.56; χ²=0.19; P=0.01]. A significant difference was identified in the GG genotype distribution between GC patients and control subjects (OR=4.58; 95% CI, 1.18-17.79; P=0.022). Thus, the results of the present study indicate that the MDM2 gene T309G intron (GG) genotype may be an important risk factor for GC development in the Turkish population.

Correlations of MMP-2 and TIMP-2 gene polymorphisms with the risk and prognosis of gastric cancer

AIM

To investigate the correlations of MMP-2 and TIMP-2 polymorphisms with the risk and prognosis of gastric cancer (GC).

METHODS

With an incorporation of 254 GC patients in the case group and 250 healthy subjects enrolled as the control group, this experiment was conducted. Denaturing high performance liquid chromatography method was adopted to detect all genotypes under partial denaturation, haloptype analysis was completed with the Shesis software. Serum MMP-2 and TIMP-2 levels were determined by the immunohistochemical semi-quantitative analysis. The follow-up examination was conducted after the patients had completed systemic therapy and discharged.

RESULTS

The distribution frequencies of MMP-2-735C/T locus genotypes between groups were compared (P > 0.05). However, the distributions of alleles and genotype frequencies of MMP-2-1306C/T, TIMP-2-303G/A and -418G/C all exhibited statistical difference (all P < 0.05). The gene polymorphism of MMP-2-1306C/T was statistically correlated with the expression of MMP-2 protein (P < 0.05); the same result was also found regarding TIMP-2-303G/A (P < 0.05). The haplotype analysis revealed that the CGC frequency of the case group was apparently higher than that of the control group (P < 0.05), the positive survival rate of CGC was apparently lower than the negative one.

CONCLUSION

MMP-2-1306C/T, TIMP-2-303G/A and -418G/C variants might be correlated with GC susceptibility. Serum MMP-2 and TIMP-2 protein levels might be associated with GC susceptibility; Additionally, CGC haplotype might be the risk factor of GC.

The NFKB1 polymorphism (rs4648068) is associated with the cell proliferation and motility in gastric cancer

BACKGROUND

We have demonstrated previously that NFKB1 single nucleotide polymorphism (SNP) rs4648068 GG homozygote was associated with the increased risk of gastric cancer in Chinese Han population. In this study, we constructed the recombinant plasmid pGL3-AA, pGL3-GG, pGL3-AA-NFKB and pGL3-GG-NFKB to investigate the function of rs4648068 by cell biology experiments.

METHODS

Quantitative real-time PCR was used to detect NFKB1 SNP rs4648068 genotype in the patients with gastric cancer. Anti-NF-κB1 p50 polyclonal antibodies were used for immunohistochemical analysis of the tissue specimens. The subsection of NFKB1 containing the promoter site and adjacent three consecutive exons were obtained by PCR technique and subcloned into the vector pGL3-Basic. Dual-Luciferase reporter assay was used to detect the transcriptional activity of the constructed promoter. Effects of transcription factor NFKB1 on C/EBPβ expression were determined by chromatin immunoprecipitation and Western analysis. Furthermore, proliferation and invasion ability of the transduced cell were also measured and compared.

RESULTS

Intensive staining for p50 expression was observed in the tissues of GG genotype patients, compared with those of GA group and AA genotype patients. The transcriptional activity of rs4648068 (A > G) by dual-Luciferase reporter assay suggested that the luciferase activity of homozygote group (pGL3-GG) was greater than that of the control (pGL3-AA), especially at the stimulation of LPS. We found that the luciferase activity was also influenced by pGL3-GG levels. The effects of NFKB1 rs4648068 were enhanced by rs4648065 on the transduced cells. The interaction between NFKB1 promoter nucleotide sequence and C/EBPβ was regulated by the functional SNP rs4648068 in SGC-7901 cells. Our data indicated that the transduction of pGL3 expression plasmid pGL3-GG-NFKB improved the proliferation and motility of gastric cancer cells. Correspondingly, the homozygote GG of SNP rs4648068 strengthened the transcriptional activity of NFKB1 and influenced the cell biological activity.

CONCLUSION

The transcriptional activity of NFKB1 was associated with SNP rs4648068, and this functional SNP site has the important effects on cell proliferation and motility.

Role of E3 ubiquitin ligases in gastric cancer

E3 ubiquitin ligases have an important role in carcinogenesis and include a large family of proteins that catalyze the ubiquitination of many protein substrates for targeted degradation by the 26S proteasome. So far, E3 ubiquitin ligases have been reported to have a role in a variety of biological processes including cell cycle regulation, cell proliferation, and apoptosis. Recently, several kinds of E3 ubiquitin ligases were demonstrated to be generally highly expressed in gastric cancer (GC) tissues and to contribute to carcinogenesis. In this review, we summarize the current knowledge and information about the clinical significance of E3 ubiquitin ligases in GC. Bortezomib, a proteasome inhibitor, encouraged the evaluation of other components of the ubiquitin proteasome system for pharmaceutical intervention. The clinical value of novel treatment strategies targeting aberrant E3 ubiquitin ligases for GC are discussed in the review.

Meta-analysis of the MDM2 T309G polymorphism and gastric cancer risk

BACKGROUND

Mdm2 binds to the amino-terminus of p53 to induce its degradation and a single nucleotide polymorphism in the MDM2 promoter region (T309G) has been reported to increase the risk of several carcinomas, such as gastric cancer. However, the results of published studies to analyze the association between MDM2 T309G and gastric cancer havve often conflicted.

METHODS

To better illustrate the filiation between MDM2 T309G and gastric cancer, we performed a meta-analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the relationship. The pooled ORs were performed for 4 models, additive, recessive, co-dominant model, and dominant.

RESULTS

Nine published case-control studies including 3,225 gastric cancer cases and 4,118 controls were identified. The MDM2 T309G polymorphism was associated with a significantly increased risk of gastric cancer risk when all studies were pooled into the meta-analysis (GG versus TT, OR=1.57; 95%CI=1.57-2.12; p=0.003) and GG versus GT/TT, OR=1.52; 95%CI=1.217-1.90; p<0.001). Furthermore, Egger<s test did not show any evidence of publication bias (P = 0.608 for GG versus TT).

CONCLUSION

Our results suggest that the MDM2 T309G polymorphism is indeed associated with a significantly increased risk of gastric cancer.

A MDM2-dependent positive-feedback loop is involved in inhibition of miR-375 and miR-106b induced by Helicobacter pylori lipopolysaccharide

Dysregulation of microRNAs (miRNAs) has been linked to virulence factors of Helicobacter pylori and shown to contribute to the progression of gastric cancer. However, the mechanisms of these processes remain poorly understood. The aim of this study was to investigate the mechanisms by which lipopolysaccharide (LPS), a virulence factor of H. pylori, regulates miR-375 and miR-106b expression in gastric epithelial cells. The results show that LPS from H. pylori 26695 downregulated the expression of miR-375 and miR-106b in gastric epithelial cells, and low levels of Dicer were also observed. Downregulation of miR-375 was found to increase expression of MDM2 with SP1 activation. Overexpression of MDM2 inhibited Dicer by repressing p63 to create a positive-feedback loop involving SP1/MDM2/p63/Dicer that leads to inhibition of miR-375 and miR-106b expression. In addition, we demonstrated that JAK1 and STAT3 were downstream target genes of miR-106b. H. pylori LPS also enhanced the tyrosine phosphorylation of JAK1, JAK2 and STAT3. Together, these results provide insight into the regulatory mechanisms of MDM2 on H. pylori LPS-induced specific miRNAs, and furthermore, suggest that gastric epithelial cells treated with H. pylori LPS may be susceptible to JAK/STAT3 signal pathway activation via inhibition of miR-375 and miR-106b.

TP53 and MDM2 polymorphisms and the risk of endometrial cancer in postmenopausal women

The aim of the study was to determine an association of TP53 codon 72 (Arg72Pro, G>C transversion, rs1042522) and MDM2 SNP309 (T>G change, rs2279744) polymorphisms in endometrial cancer (EC) of postmenopausal women, regarding grading and staging of EC. In the study, endometrial samples from 202 postmenopausal female patients (the study group, n = 152, was women with EC; the control group, n = 50, cancer-free patients) were taken for the evaluation of two gene polymorphisms: TP53 codon 72 and MDM2 SNP309, respectively. Genotypic analyses were performed using the PCR-RFLP technique. There were significant differences in the frequency of TP53 and MDM2 genotypes in EC patients-increased EC occurrence was observed with the presence of MDM2 G/G and TP53 Arg/Arg genotypes, while allele Pro of TP53 decreased cancer risk. Analysis of combined MDM2/TP53 polymorphisms revealed that T/T-Pro/Arg genotype decreased EC risk, whereas G/G-Arg/Arg genotype increased it. Association of these genetic polymorphisms with histological grading showed increased MDM2 G/G homozygote and TP53 Arg/Arg homozygote frequencies in grading 2 as well as allele G overrepresentation in G1 and G3 EC patients. Finally, with clinical FIGO staging under evaluation, an increase in MDM2 G/G and TP53 Arg/Arg homozygote frequencies in staging I and TP53 Arg/Arg homozygote frequencies in staging II were observed. Co-occurrence of some MDM2 SNP309 and TP53 codon 72 polymorphisms seems to influence EC risk, involving grading and staging of this neoplasm at the same time.

MDM2 oncogene, E3 ubiquitin protein ligase T309G polymorphism and risk of oesophageal or gastric cancer: meta-analysis of 15 studies

OBJECTIVE

To investigate the association between potentially functional MDM2 oncogene, E3 ubiquitin protein ligase (MDM2) T309G polymorphism and susceptibility to oesophageal or gastric cancer.

METHODS

Two investigators independently searched the PubMed and Chinese National Knowledge Infrastructure databases for studies published before September 2013.

RESULTS

Pooled results showed that the variant homozygous 309 GG genotype (versus TT) was significantly associated with increased risk of both oesophageal (odds ratio [OR] 0.77; 95% confidence interval [CI] 0.65, 0.90) and gastric cancer (OR 0.52; 95% CI 0.38, 0.72). Subgroup analysis revealed a 309 GG-associated increased risk for both cancer types in Asian populations, particularly among Chinese and Japanese ethnicity. When stratified for Helicobacter pylori infection and histological type of gastric cancer, the 309 GG-related risk was higher in H. pylori-positive patients (T versus G: OR 0.37; 95% CI 0.22, 0.63) and the association was stronger with intestinal (TT + TG versus GG: OR 0.68; 95% CI 0.54, 0.87) rather than diffuse gastric-cancer type.

CONCLUSIONS

The MDM2 T309G polymorphism may be significantly associated with increased susceptibility to oesophageal or gastric cancer, particularly among Eastern Asian populations.

MDM2 SNP309 is an ethnicity-dependent risk factor for digestive tract cancers

Published data on the relationship between T309G polymorphism in the murine double minute 2 (MDM2) gene and susceptibility of digestive tract cancers (DTC) are inconclusive. Thus, the aim of this study is to determine whether MDM2 T309G polymorphism is associated with the risk of diverse DTC, including esophagus, stomach, liver, bile duct, pancreas, and colorectum cancers. Relevant studies were identified up to October 1, 2013. Crude odds ratio (OR) and 95% confidence interval (CI) were used as a measure of the strength of the association. The pooled result based on all studies showed that there was a statistically significant link between MDM2 T309G polymorphism and DTC susceptibility (T vs. G: OR = 0.82, 95%CI = 0.76-0.88). When stratified by race, significant associations were observed for all genetic models among Asians (especially in Chinese population), but not among Caucasians. Subgroup analyses according to tumor location indicated that the genetic variant was associated with esophageal (OR = 0.88, 95%CI = 0.81-0.96 for T vs. G), hepatocellular (OR = 0.69, 95%CI = 0.57-0.84 for T vs. G) and pancreatic cancer risk but not associated with cholangiocarcinoma or colorectum cancer susceptibility. Meanwhile, the G allele was also suggested to be associated with increased gastric cancer risk (OR = 0.68, 95%CI = 0.54-0.87 for TT + TG vs. GG for intestinal type of gastric cancer and OR = 0.18, 95%CI = 0.06-0.50 for TT vs. GG for Helicobacter pylori infection positive stomach cancer). Our study indicates that the MDM2 T309G polymorphism may be an ethnicity-dependent risk factor for DTC, especially for the upper gastrointestinal tract malignancies.

Meta-analysis of associations between MDM2 SNP309 polymorphism and gastric cancer risk

Epidemiological studies have been conducted to evaluate genetic variations of murine double minute 2 (MDM2) SNP309 associated with the risk of gastric cancer (GC), although evidence remains conflicting. To gain a better understanding of this relationship, a meta-analysis was performed. Several electronic databases were searched up to February 2013, in order to identify relevant case-control studies. Seven published case-control studies with 2,199 cases and 3,201 controls were included. In the overall analysis, significant associations between the MDM2 SNP309 variant and GC risk were found for G vs. T alleles (OR=1.35; 95% CI, 1.24-1.47), GG vs. TT (OR=1.88; 95% CI, 1.59-2.24), recessive model (OR=1.71; 95% CI, 1.49-1.96). Furthermore, stratified by cancer site, significant associations were observed in gastric cardia cancer for all the models, although no significant association was found in any of the models among non-gastric cardia cancer, with the exception of the recessive model. In the subgroup analysis by source of control, MDM2 SNP309 was associated with increased GC risk for the hospital-based case-control (HCC) study for the GG vs. TT, recessive model and for the population-based case-control (PCC) study for the GG vs. TT, recessive model. Following stratification by gender and infection status of Helicobacter pylori (HP) for the recessive model, a significant association was found only in the HP-positive infected individuals. However, no statistically significant association was observed in males, females or the HP-negative infected individuals. In summary, the association between MDM2 SNP309 and GC risk was statistically significant, particularly in gastric cardia cancer for the HP-positive population group.