Genotyping of single nucleotide polymorphism in MDM2 genes by universal fluorescence primer PCR and capillary electrophoresis

Exploring the significance of MDM2 gene promoter variants in chronic myeloid leukemia

Tyrosine kinase inhibitors (TKIs) targeting BCR::ABL1 are highly successful in chronic myeloid leukemia (CML). However, extensive interpatient variability in therapeutic responses and resistance supports the need to find new prognostic biomarkers. We have previously reported that TP53 SNP215 variant affects CML risk and clinical outcome. We aimed to evaluate the role of MDM2 genetic variants in CML susceptibility and treatment response to TKIs. We genotyped five MDM2 promoter variants (del1518, SNP309, SNP285, SNP288 and SNP344) in 135 CML patients and 136 healthy individuals. Our study showed that MDM2 variants alone or in combination had no effect on CML susceptibility. The analysis of MDM2 genotypes in relation to patients' clinical parameters revealed that individuals with SNP309 G/G genotypes were at a significantly increased risk of undergoing molecular response failure (p = 0.044). Improved overall survival was also observed for non-responders with the alternative MDM2 del1518 del allele (p = 0.017) as well as for MDM2 del1518-SNP309 combinations with alternative genotypes (p = 0.014). In addition, combinatorial analysis demonstrated that alternative MDM2 SNP309 and TP53 SNP215 genotypes together are associated with faster achievement of MR2 (p = 0.029) and MMR (p = 0.042) in non-responders, suggesting a relationship with a favorable outcome. Overall, our study highlights the influence of MDM2 variants on clinical outcome, supporting that specific genotypes, alone or in combination, underlie the treatment-responsive phenotype.

Single-Round DNA Aptamer Selection by Combined Use of Capillary Electrophoresis and Next Generation Sequencing: An Aptaomics Approach for Identifying Unique Functional Protein-Binding DNA Aptamers

In DNA aptamer selection, existing methods do not discriminate aptamer sequences based on their binding affinity and function and the reproducibility of the selection is often poor, even for the selection of well-known aptamers like those that bind the commonly used model protein thrombin. In the present study, a novel single-round selection method (SR-CE selection) was developed by combining capillary electrophoresis (CE) with next generation sequencing. Using SR-CE selection, a successful semi-quantitative and semi-comprehensive aptamer selection for thrombin was demonstrated with high reproducibility for the first time. Selection rules based on dissociation equilibria and kinetics were devised to obtain families of analogous sequences. Selected sequences of the same family were shown to bind thrombin with high affinity. Furthermore, data acquired from SR-CE selection was mined by creating sub-libraries that were categorized by the functionality of the aptamers (e. g., pre-organized aptamers versus structure-induced aptamers). Using this approach, a novel fluorescent molecular recognition sensor for thrombin with nanomolar detection limits was discovered. Thus, in this proof-of-concept report, we have demonstrated the potential of a "DNA Aptaomics" approach to systematically design functional aptamers as well as to obtain high affinity aptamers.

Genetic polymorphisms of TP53 (rs1042522) and MDM2 (rs2279744) and colorectal cancer risk: An updated meta-analysis based on 59 case-control studies

OBJECTIVE

Several earlier reports implicated TP53 (rs1042522) and MDM2 (rs2279744) variants in outcome of colorectal cancer (CRC), but with inconclusive findings. This current meta-analysis designed to uncover the role of these variants in CRC risk.

METHODOLOGY

Two independent investigators extracted 59 eligible case-control studies from different electronic databases involving Scopus, Web of Science and PubMed prior to June 2019. Pooled odds ratios (ORs) and "95% confidence intervals (CIs)" were computed for different hereditary models. Stratification and heterogeneity analyses, and "Begg's funnel plots" were conducted. In silico data analyses of the functional and structural properties of the study variants were applied.

RESULTS

In general, 47 and 16 case-control reports for TP53 (11,589 patients and 13,622 controls) and MDM2 (6841 CRC patients and 8792 healthy controls), respectively were enrolled in this meta-analysis. A significant association of TP53 (rs1042522) variant with increased CRC risk in overall pooled subjects under recessive model [(CC vs. GC + GG, OR = 1.134, 95% CI = 1.006-1.278, P = 0.039)] was observed. Moreover, an evidence of MDM2 (rs2279744) association with increased CRC risk in overall pooled subjects under dominant and heterozygote models [(TG + GG vs. TT, OR = 1.120, 95% CI = 1.003-1.250, P = 0.044) and (TG vs. TT, OR = 1.189, 95% CI = 1.076-1.313, P = 0.001), respectively] was reported. Additionally, TP53 (rs1042522) and MDM2 (rs2279744) showed an association with CRC risk among Asians and Africans under a recessive model, and among Asians under different genetic models, respectively, by stratification analysis.

CONCLUSION

TP53 (rs1042522) and MDM2 (rs2279744) variants might represent candidate risk factors for CRC susceptibility.

Correlations between MDM2 gene SNP309 polymorphism and susceptibility to leukemia

BACKGROUND

The objective of this study was to perform a systematic review of correlations between the single-nucleotide polymorphism at nucleotide 309 (single-nucleotide polymorphism, SNP309) in the murine double-minute 2 (MDM2) gene promoter and susceptibility to leukemia.

MATERIAL/METHODS

We performed a computer search of relevant case-control studies published from January 1990 to Jan 2014 in databases such as Ovid, EBSCO, PubMed, CNKI, CBMDISC, VIP, and WanFang Data. The literature was screened based on inclusion and exclusion criteria. The data were retrieved, and the quality of the methodology used in the studies was evaluated. A meta-analysis was performed by calculating the combined odds ratios (OR) and 95% confidence intervals (CI) using RevMan 5.0 and Stata 10.0 software. Sensitivity was analyzed and publication bias was assessed.

RESULTS

A total of ten case-control studies from nine research papers were selected in this study, which included 1889 cases and 5707 controls. Meta-analysis showed that people who carried the G allele had increased susceptibility to leukemia compared to people who carried the T allele [OR=1.24, 95% CI (1.06, 1.45), P=0.007]. In a recessive model, the GG homozygotic population had a higher risk of leukemia than the heterozygotic GT+TT population [OR=1.47, 95% CI (1.11, 1.96), P=0.008]. We did not find significant difference in a dominant model [GG+GT vs. TT: OR=1.22, 95% CI (0.98, 1.52), P=0.07]. Publication bias was not significant.

CONCLUSIONS

SNP309 polymorphism in the MDM2 gene is associated with susceptibility to leukemia. The G allele may be a risk factor for leukemia.

Association between the MDM2 T309G polymorphism and leukemia risk: a meta-analysis

Several studies have suggested associations between MDM2 (mouse double minute 2 homolog) polymorphisms and leukemia risk, but they reported contradictory results. For better understanding of the effect of MDM2 T309G polymorphism on leukemia risk, we performed a meta-analysis. All eligible studies were identified through a search of PubMed, Web of Science, EMBASE, and Chinese Biomedical Literature (CBM) databases before May 2014. Assessment of associations between the MDM2 T309G polymorphism and leukemia risk was conducted by odds ratios (ORs) and 95% confidence intervals (95% CIs). Finally, a total of 11 publications covering 12 case-control studies with 2, 362 cases and 5, 562 controls concerning MDM2 T309G polymorphism with respect to leukemia were included in the meta-analysis. Significant associations were found between MDM2 T309G polymorphism and leukemia risk in four models in overall populations (G vs T: OR=1.29, 95% CI=1.11- 1.49, p=0.001; GG vs TT: OR=1.67, 95% CI=1.21-2.30, p=0.002; GG vs TG/TT: OR=1.56, 95% CI=1.21-2.00, p=0.001; GG/TG vs TT: OR=1.28, 95% CI=1.05-1.57, p=0.015). In the sub-group analysis according to ethnicity, increased leukemia risks were observed in three genetic models among Asians but not Caucasians. In conclusion, the results of our meta-analysis suggest that the MDM2 T309G polymorphism can increase the risk of leukemia, especially among Asian populations.

MDM2 SNP309 polymorphism is associated with colorectal cancer risk

The human murine double minute 2 (MDM2) is known as an oncoprotein through inhibiting P53 transcriptional activity and mediating P53 ubiquitination. Therefore, the amplification of MDM2 may attenuate the P53 pathway and promote tumorigenesis. The SNP309 T>G polymorphism (rs2279744), which is located in the intronic promoter of MDM2 gene, was reported to contribute to the increased level of MDM2 protein. In this hospital-based case-control study, which consisted of 573 cases and 588 controls, we evaluated the association between MDM2 SNP309 and the risk of colorectal cancer (CRC) in a Chinese population by using the TaqMan method to genotype the polymorphism. We found that the MDM2 SNP309 polymorphism was significantly associated with CRC risk. In addition, in our meta-analysis, we found a significant association between MDM2 SNP309 and CRC risk among Asians, which was consistent with our results. In conclusion, we demonstrated that the MDM2 SNP309 polymorphism increased the susceptibility of CRC in Asian populations.

An updated meta-analysis on the association of MDM2 SNP309 polymorphism with colorectal cancer risk

BACKGROUND

The mouse double minute 2 (MDM2) gene encodes a phosphoprotein that interacts with P53 and negatively regulates its activity. The SNP309 polymorphism (T-G) in the promoter of MDM2 gene has been reported to be associated with enhanced MDM2 expression and tumor development. Studies investigating the association between MDM2 SNP309 polymorphism and colorectal cancer (CRC) risk reported conflicting results. We performed a meta-analysis of all available studies to explore the association of this polymorphism with CRC risk.

METHODS

All studies published up to July 2013 on the association between MDM2 SNP309 polymorphism and CRC risk were identified by searching electronic databases PubMed, EMBASE, and Chinese Biomedical Literature database (CBM) databases. The association between the MDM2 SNP309 polymorphism and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

RESULTS

A total of 14 case-control studies including 4460 CRC cases and 4828 controls were identified. We did not find a significant association between the MDM2 SNP309 polymorphism and CRC risk in all genetic models in overall population. However, in subgroup analysis by ethnicity, significant associations were found in Asians (TG vs. TT: OR = 1.197, 95% CI = 1.055-1.358, P=0.005; GG+TG vs. TT: OR = 1.246, 95% CI = 1.106-1.404, P=0.000) and Africans. When stratified by HWE in controls, significantly increased risk was also found among the studies consistent with HWE (TG vs. TT: OR = 1.166, 95% CI = 1.037-1.311, P= 0.010). In subgroup analysis according to p53 mutation status, and gender, no any significant association was detected.

CONCLUSIONS

The present meta-analysis suggests that the MDM2 is a candidate gene for CRC susceptibility. The MDM2 SNP309 polymorphism may be a risk factor for CRC in Asians.

Current evidence on the relationship between SNP309 polymorphism in the MDM2 gene and colorectal cancer risk

It has been demonstrated that MDM2 is a well-established negative regulator of the p53 protein and might be associated with a significantly earlier age of onset of several tumors, including colorectal cancer (CRC). In recent years, a T to G substitution (SNP309) in the promoter of MDM2 has been extensively studied as a potential CRC risk factor; however, the results are inconsistent. To derive a more precise estimation of association between MDM2 SNP309 polymorphism and CRC risk, we conducted a meta-analysis of 11 studies with 4,050 CRC cases and 3,688 controls. For MDM2 SNP309 polymorphism, no obvious associations were found for all genetic models when all studies were pooled into the meta-analysis. In the subgroup analyses by ethnicity, source of controls, and Hardy-Weinberg equilibrium (HWE) in controls, a significantly increased risk was observed among Asians (heterozygous model: odds ratio (OR) = 1.21, 95% confidence interval (CI) = 1.06-1.39, P = 0.005), population-based studies (heterozygous model: OR = 1.17, 95% CI = 1.02-1.34, P = 0.027), and among studies without the HWE (recessive model: OR = 1.42, 95% CI = 1.03-1.94, P = 0.030). When excluding three studies deviated from HWE, the significant results were also observed for heterozygous model in overall population (OR = 1.16, 95% CI = 1.02-1.31, P = 0.020). No publication bias was found in the present study. In conclusion, this meta-analysis suggests that MDM2 SNP309 polymorphism was associated with CRC susceptibility, especially among Asians. Further research is needed to assess possible gene-gene or gene-environment-lifestyle interactions on CRC.

MDM2 promoter polymorphism and p53 codon 72 polymorphism in chronic myeloid leukemia: the association between MDM2 promoter genotype and disease susceptibility, age of onset, and blast-free survival in chronic phase patients receiving imatinib

The genetic or functional inactivation of the p53 pathway plays an important role with regards to disease progression from the chronic phase (CP) to blast phase (BP) and imatinib treatment response in chronic myeloid leukemia (CML). Two functional single nucleotide polymorphisms (SNPs), p53 R72P and MDM2 SNP309, are associated with alternation of p53 activity, however the association regarding CML susceptibility and BP transformation under imatinib treatment is unclear. The MDM2 SNP309 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism and confirmed by direct sequencing from 116 CML patients, including 104 in the CP at diagnosis, and 162 healthy Taiwanese controls. The p53 R72P polymorphism was examined in all CML patients. The SNP309 G/G genotype was associated with an increased risk of CML susceptibility (OR: 1.82, 95% CI: 1.03-3.22, P = 0.037), and an earlier age of disease onset (log-rank P = 0.005) compared with the T/T + T/G genotypes. Higher MDM2 mRNA expression was found in G/G genotype compared with T/T (P = 0.034) and T/T + T/G (P = 0.056) genotypes. No associations were found between the p53 R72P genotypes and clinical parameters and survival outcomes. Among 62 CP patients receiving imatinib as first-line therapy, the G/G genotype was associated with a shorter blast-free survival (log-rank P = 0.048) and more clonal evolution compared with the T/T + T/G genotypes. In patients with advanced diseases at diagnosis, the G/G genotype was associated with a poor overall survival (log-rank P = 0.006). Closely monitoring CML patients harboring the G/G genotype and further large-scale studies are warranted.

Quantitative analysis of multiple genes' expressions based on a novel competitive RT-PCR assay

We established a novel gene expression analysis platform, Multiplex Competitive RT-PCR Using Fluorescent Universal Primers (MCF-PCR), to study multi-gene expression patterns simultaneously. This platform combines fluorescent universal primers, multiplex competitive RT-PCR, and capillary electrophoretic separation, which ensures MCF-PCR a reliable, medium-throughput, cost-effective technology for gene expression profiling. With cloned standard DNAs, the detection limits, precision, and sensitivity of MCF-PCR were evaluated and compared with that of the assay without adding competitive templates and real-time PCR, respectively. The results showed that detection limit was 3.125 × 10(3) to 3.2 × 10(6) copies, and 10 % copy differences between two samples can be detected by MCF-PCR. To validate MCF-PCR, we analyzed expression profile of five genes in interleukin (IL)-4/IL-13 pathway in peripheral blood of 20 healthy adults and 20 allergic dermatitis patients; three genes including IL-4, IL-13, and STAT6 were found differentially expressed in the two sample groups, which maybe key players in IL-4/IL-13 immunological signaling pathway and need further function analysis.

Capillary electrophoretic genotyping of epidermal growth factor receptor for pharmacogenomic assay of lung cancer therapy

In this research, a universal multiplex PCR method combining capillary gel electrophoresis was established for simultaneous analysis of mutations in exons 18-21 of EGFR kinase domain gene. After rinsing of the gel solution (1 × TBE buffer containing 2% HEC and 1.5% HPC), the diluted PCR sample was electrokinetically injected and separated at 35°C. Several parameters were investigated for method optimization, including the kinds of polymer, capillary temperature and separation voltage. Under optimal conditions, time taken for analyzing mutations of EGFR kinase domain gene in lung cancer patients was short (within 15 min). A total of 50 lung cancer patients' tumor tissues were analyzed, and two frequent mutations associated with therapeutic efficiency of lung cancer were identified, including deletion of exon 19 (8/50) and L858R point mutation in exon 21 (12/50). This method is feasible for application in pharmacogenomic assay of lung cancer therapy. By applying this simple and effective method for genotyping of lung cancer patients, the information of pharmacogenomics was supplied for lung cancer therapy and to assist diagnosis to prolong patients' lives.

MDM2 SNP309 variation contributes to leukemia risk: meta-analyses based on 7259 subjects

Evidence implicates MDM2 (murine double minute-2) T309G polymorphism as a risk factor for several cancers. Increasing numbers of studies have been carried out on the association of MDM2 T309G polymorphism with susceptibility to leukemia and have generated conflicting results. The aim of the present study was to derive a more precise estimation of the relationship. Meta-analyses assessing the association of MDM2 T309G variation with leukemia were conducted. Separate analyses on ethnicity and clinical types were also performed. Eligible studies were identified for the period up to February 2012. Consequently, seven publications including eight case-control studies with 1777 cases and 5482 controls were selected for analysis. The overall data indicated a significant association of the MDM2 T309G polymorphism with leukemia risk (GG vs. TT: odds ratio [OR] = 1.62; 95% confidence interval [CI] = 1.14-2.29; dominant model: OR = 1.20; 95% CI = 1.06-1.36; recessive model: OR = 1.47; 95% CI = 1.07-2.03). In subgroup analysis by ethnicity, the G allele may increase leukemia susceptibility among Asians (GG vs. TT: OR = 3.06; 95% CI = 2.05-4.56; dominant model: OR = 1.82; 95% CI = 1.31-2.51; recessive model: OR = 2.32; 95% CI = 1.69-3.19) but not Caucasians. In subgroup analysis by clinical types, data suggested increased risk for acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) under additive and recessive models, respectively. Similarly, elevated risk for chronic lymphocytic leukemia (CLL) was shown under the dominant model. Collectively, the results of the present study suggest that MDM2 T309G polymorphism might be a low-penetrant risk factor for leukemia among Asians but not Caucasians. The G allele might increase CLL susceptibility and homozygous GG might elevate AML and CML risk.

MDM2 SNP309 contributes to tumor susceptibility: a meta-analysis

The potentially functional polymorphism, SNP309, in the promoter region of MDM2 gene has been implicated in cancer risk, but individual published studies showed inconclusive results. To obtain a more precise estimate of the association between MDM2 SNP309 and risk of cancer, we performed a meta-analysis of 70 individual studies in 59 publications that included 26,160 cases with different types of tumors and 33,046 controls. Summary odds ratios (OR) and corresponding 95% confidence intervals (CIs) were estimated using fixed- and random-effects models when appropriate. Overall, the variant genotypes were associated with a significantly increased cancer risk for all cancer types in different genetic models (GG vs. TT: OR, 1.123; 95% CI, 1.056-1.193; GG/GT vs. TT: OR, 1.028; 95% CI, 1.006-1.050). In the stratified analyses, the increased risk remained for the studies of most types of cancers, Asian populations, and hospital- /population-based studies in different genetic models, whereas significantly decreased risk was found in prostate cancer (GG vs. TT: OR, 0.606; 95% CI, 0.407-0.903; GG/GT vs. TT: OR, 0.748; 95% CI, 0.579-0.968). In conclusion, the data of meta-analysis suggests that MDM2 SNP309 is a potential biomarker for cancer risk.

Cost-effective interrogation of single nucleotide polymorphisms using the mismatch amplification mutation assay and capillary electrophoresis

The ability to characterize SNPs is an important aspect of many clinical diagnostic, genetic and evolutionary studies. Here, we designed a multiplexed SNP genotyping method to survey a large number of phylogenetically informative SNPs within the genome of the bacterium Bacillus anthracis. This novel method, CE universal tail mismatch amplification mutation assay (CUMA), allows for PCR multiplexing and automatic scoring of SNP genotypes, thus providing a rapid, economical and higher throughput alternative to more expensive SNP genotyping techniques. CUMA delivered accurate B. anthracis SNP genotyping results and, when multiplexed, saved reagent costs by more than 80% compared with TaqMan real-time PCR. When real-time PCR technology and instrumentation is unavailable or the reagents are cost-prohibitive, CUMA is a powerful alternative for SNP genotyping.

MDM2 309 T/G polymorphism is associated with colorectal cancer risk especially in Asians: a meta-analysis

The murine double minute 2 (MDM2) gene encodes an important regulator which mainly functions as an E3 ligase. The role of the MDM2 protein in the P53 pathway has been especially well-studied. In this study, our aim was to explore the relationship between MDM2 gene 309 T/G polymorphism and colorectal cancer risk. Performing both the overall meta-analysis and the subgroup meta-analysis based on ethnicity and source of controls with a total of 7 eligible studies (2,543 cases and 2,115 controls in all), we detected a significant colorectal cancer risk variation for TG versus GG (OR=0.73, 95% CI=0.62-0.86) in the overall analysis and another significant colorectal cancer risk variation for TG versus GG (OR=0.70, 95% CI=0.59-0.83) in the population-based controls' subgroup as well. Moreover, in the subgroup analysis based on ethnicity, significant associations were observed for all genetic models in Asians (OR=0.51, 95% CI=0.41-0.64 for TT versus GG; OR=0.64, 95% CI=0.53-0.78 for TG versus GG; OR=0.59, 95% CI=0.49-0.71 for dominant model; OR=0.69, 95% CI=0.57-0.82 for recessive model), while in Caucasians there was no obvious association. In summary, according to the results of our meta-analysis, the MDM2 309 G allele probably acts as a colorectal cancer risk factor, especially in Asians.