Association Of The MDM2 And 53BP1 Polymorphisms With Esophageal Squamous Cell Carcinoma And Gastric Cardiac Adenocarcinoma

Objective: p53, one of the tumor suppressor proteins, plays a key role in cell cycle regulation and cell stabilization. The mutation, deletion or inactivation of p53 gene has been found in at least half of all human tumors. MDM2 (mouse double minute 2) and 53BP1 (p53 binding protein 1) are two associated proteins of p53. They can affect p53 functions through binding to p53. This study was to investigate the correlation of MDM2 SNP309, Del1518, 53BP1 T885G,P909L and W1488G single nucleotide polymorphisms (SNPs) to susceptibilities of esophageal squamous cell carcinoma (ESCC) and gastric cardiac adenocarcinoma (GCA) in a high risk area of Hebei Province of China.Methods: This population-based case-control study included 563 cancer patients (351 with ESCC and 212 with GCA) and 642 healthy controls. Genomic DNA was extracted by using proteinase K digestion followed by a salting out procedure. MDM2 and 53BP1 polymorphisms were analyzed by polymerase chain reaction restriction fragment length polymorphism analysis (PCR-RFLP) and primer-introduced restriction analysis-polymerase chain reaction (PIRA-PCR) respectively.Statistical analysis was performed using SPSS11.5 software package. P<0.05 was considered significant for all statistical analyses. Hardy-Weinberg analysis was performed by the software package from internet (http://www.kursus.kvl.dk/ shares/vetgen/_Popgen/genetik/applets/kitest.htm).Comparison of the MDM2 and 53BP1 genotype distribution in the study groups was performed by means of two-sided contingency tables using Chi-square test. The MDM2 haplotype frequencies and linkage disequilibrium coefficient were estimated by using EH linkage software and 2LD software. The odds ratio (OR) and 95% confidence Interval (CI) were calculated using an unconditional logistic regression model and adjusted by age, sex, smoking status and UGIC (upper gastrointestinal cancer) history accordingly.Results:1 MDM2 SNP309 and Del15181.1 The frequency of positive family history of upper gastrointestinal cancer (UGIC) in ESCC (47%) and GCA (49.1%) patients was significantly higher than that in healthy controls (34.4%) (χ~2=15.13 P=0.000 andχ~2=14.48, P=0.000). The proportion of smokers in ESCC and GCA patients (39.9% and 46.7% respectively) was not significantly different from that in healthy controls (42.8%) (χ~2=0.81,P=0.37 andχ~2=0.97,P=0.33,respectively). 1.2 The distribution of the MDM2 and 53BP1 polymorphisms among ESCC, GCA patients and healthy conctrols did not significantly deviate from those expected by Hardy-Weinberg equilibrium (P>0.05). The genotype distribution of the MDM2 SNP309 and Del1518 in overall ESCC patients were not significantly different from that in healthy controls (P>0.05). However, in GCA patients, freqency of the individuals with MDM2 SNP309T allelotype (G/T+T/T genotype) and with Del1518- allelotype (+/- + +/+genotype) (52.8% and 37.7, respectively) was lower than that in healthy controls (64.8% and 51.7%, respectively) (χ~2=9.67,P=0.002 andχ~2=12.47,P=0.001). Compared with SNP309 G/G genotype, the SNP309T allelotype (G/T+T/T genotype) had lower risk to develop GCA (adjusted OR=0.62, 95%CI=0.45～0.87); the Del1518- allelotype (+/- + +/+ genotype) can decrease the risk of developing GCA, compared with the -/- genotype (ajusted OR=0.57, 95%CI=0.41～0.78).1.3 When sratified by smoking status, compared with MDM2 SNP309 G/G, individuals with T allele (G/T+T/T genotype) were not susceptible to GCA among non-smokers (OR=0.50, 95%CI=0.32～0.77); compared with MDM2 Del1518+/+, individuals with Del1518- allele (+/- and -/- genotype) had lower risk to develop GCA among non-smokers (OR=0.52, 95%CI=0.33~0.80). But stratification analysis according to smoking status did not show any influence of MDM2 SNP309 or Del1518 on the development of ESCC. 1.4 When stratified by family history of UGIC, a significant association of the MDM2 SNP309 T allele (G/T+T/T) with decreased risk of GCA was observed in group with positive family history, compared with T/T genotype (OR=0.53, 95%CI=0.33~0.86); compared with Del1518+/+ genotype, in positive and negative familly history groups, Del1515- allele (+/- + +/+) can decrese the risk of developing GCA, respectively (OR=0.59, 95%CI=0.37~0.96 and OR=0.56, 95%CI=0.36~0.86). However, there was no difference between ESCC patients and healthy controls in MDM2 SNP309 and Del1518 polymorphisms.1.5 The combined effect of MDM2 SNP309 and Del1518 on ESCC and GCA was analyzed by EH and 2LD softwares. It was shown that two polymophisms were in linkage disquilibrium (D'=0.76,χ~2=440.41, P=0.000). Thus, the MDM2 SNP309 T and Del1518- alleles were in linkage disequilibrium. The haplotype distribution was significantly different between the overall GCA and healthy controls (χ~2=20.44, P=0.000), whereas the haplotype distribution between the overall ESCC and healthy controls was similar (P>0.05). Compared with the SNP309G/Del1518+ haplotype, the SNP309 T/Del1518- haplotype distinctly decreased susceptbility to GCA (OR=0.51, 95%CI=0.38~0.70).2 53BP1 P909L,W1488G and T885G2.1 The frequency of positive family history of upper gastrointestinal cancer (UGIC) in ESCC (47.3%) and GCA (46.2%) patients was significantly higher than that in healthy controls (34.6%) (χ2=15.09 P=0.00 andχ2=10.83, P=0.00). The proportion of smokers in ESCC and GCA patients (40.1% and 48.0% respectively) was not significantly different from that in healthy controls (43.0%) (χ2=0.77,P=0.38 andχ2=1.95,P=0.16,respectively).2.2 53BP1 P909L Pro/Pro and W1488G Gly/Gly genotypes were detected in our study. The overall 53BP1 T885G genotype distributions were not significantly different between ESCC,GCA patients and healthy controls (P>0.05).2.3 When stratified by smoking status and family history of UGIC, T885G also did not significantly associated with the development of ESCC and GCA (P>0.05).2.4 Stratified analysis by P53 Arg72Pro genotypes, 53BP1 T885G G/G genotype could reduce susceptibility to GCA among the individuals with Pro allele (Arg/Pro+Pro/Pro genotype) (OR=0.74, 95%CI=0.57~0.95 ). But there was no influnence on ESCC.Conclusions:1 Family history of UGIC significantly increases the risk of developing ESCC and GCA.2 Compared with MDM2 SNP309 G/G genotype, individuals with T allele (G/T+T/T) had significantly lower risk to develop GCA. 3 Compared with MDM2 Del1518 +/+ genotype, individuals with Del1518- allele (+/- + +/+) had significantly lower risk to develop GCA, too.4 The MDM2 SNP309 and Del1518 are in linkage disequilibrium in northern china population. The SNP309G allele tends to be linked to the Del1518+ allele. The SNP309T/Del1518- haplotype significantly decreased the risk of developing GCA, compared with SNP309G/Del1518+ haplotype.5 Only one allele of 53BP1 P909L and W1488G was detected, respectively. So these two SNPs fail to screen disease. Additionaly the 53BP1 T885G alone may not be associated with ESCC and GCA development.6 53BP1 T885G G/G genotype could reduce susceptibility to GCA among the individuals with the P53 Pro allele.