Med Oncol (2015) 32:401 DOI 10.1007/s12032-014-0401-1
ORIGINAL PAPER
Genetic association of single nucleotide polymorphisms in P53 pathway with gastric cancer risk in a Chinese Han population Guo-cong Wu • Zhong-tao Zhang
Received: 21 August 2014 / Accepted: 21 November 2014 / Published online: 6 December 2014 Ó Springer Science+Business Media New York 2014
Abstract The tumor suppressor gene P53 plays an important role in carcinogenesis, and the P53 pathway is central both in reducing cancer frequency and in mediating the response of cancer therapies. MDM2, MDM4 and Hausp genes are all critical regulators of the tumor suppressor P53. Many studies have evaluated the association of single nucleotide polymorphisms (SNPs) in P53 pathway with the risk of common cancers. However, the results are still inconclusive. In this work, we analyzed the association of SNPs in P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes with gastric cancer in a hospital-based Chinese Han population (642 cases and 720 cancer-free controls). We found that the polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) are associated with gastric cancer risk, whereas no significant association was observed between variant genotype of other two polymorphisms (MDM4 rs1380576 and Hausp rs1529916) and gastric cancer risk. Keywords P53 pathway Polymorphism Gastric cancer Chinese Han
Introduction Gastric cancer is the fourth most frequently diagnosed cancer and the second leading cause of cancer death
G. Wu Z. Zhang (&) Department of General Surgery, Beijing Friendship Hospital Affiliated with Capital Medical University, Beijing 100050, China e-mail: [email protected] G. Wu e-mail: [email protected]
worldwide [1]. It was estimated that over 70 % of newly diagnosed cases occur in developing countries. Like other complex diseases, gastric cancer is one of the complicated traits caused by both environmental and genetic factors [2]. In addition to exogenous factors, genetic polymorphisms in the carcinogen detoxification, DNA repair and cell proliferation processes are crucial in the development of gastric cancer. Recent genome-wide association studies have reported that some SNPs are associated with the susceptibility of gastric cancer [3, 4]. However, additional polymorphism sites that contribute to the susceptibility of gastric cancer require further investigation. The tumor suppressor P53 is involved in multiple pathways including apoptosis, cell cycle regulation, DNA repair and the maintenance of genetic integrity [5]. P53 has been proved to be one of the most commonly mutated genes in various types of cancers. The mutations of P53 gene can result in inactive state which is unable to initiate appropriate stress responses, leading to enhanced tumorigenic potential. Murine double minute 2 (MDM2) is one of the negative regulators of the tumor suppressor P53, which has been documented to be mutated in a variety of cancers [6]. It has been reported that MDM2 gene can bind to the N-terminus of P53 protein and inhibit its activity, resulting in P53 protein degradation via the ubiquitination pathway [7]. MDM4, a structural homologue of MDMD2, can bind to the amino terminus of P53 and function as an inhibitor of P53 activity [8]. Hausp (herpes virus-associated ubiquitin-specific protease) can stabilize MDM2, MDM4 and P53 via its deubiquitinase activity [9]. Many evidences have proved that abnormalities of genes in P53 pathway play a pivotal role in cancer [10]. Moreover, polymorphisms in these genes are important for the modulation of P53 function. For example, the polymorphism (rs2278744, T309G) in the promoter region of MDM2 gene can
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increase affinity for binding stimulatory protein 1 and result in an elevated expression level of MDM2 gene. The polymorphisms in P53 pathway have been suggested to be associated with the susceptibility of diverse cancers [11–19]. In this work, we genotyped four SNPs (P53 rs1042522, MDM2 rs2279744, MDM4 rs1380576 and Hausp rs1529916) in a hospital-based case–control study with the attempt to evaluate the association of polymorphisms and gastric cancer risk in a Chinese Han population.
Materials and methods Study subjects A total of 642 consecutive patients (366 males and 276 females) with newly diagnosed gastric cancer recruited at the Beijing Friendship Hospital, China, from May 2010 to October 2013 were enrolled as gastric cancer cases for this work. The 720 cancer-free controls (423 males and 297 females), who are free from any cancers, were randomly selected from healthy participants who visited the general health checkup division in the hospital. These case and control people are all Han Chinese from the same geographical region. Written informed consents were obtained from all case and control subjects, and the protocol was approved by the Research Ethics Committees of Beijing Friendship Hospital Affiliated with Capital Medical University. Genotyping A blood sample of 2–5 ml was drawn from each case or control subject. Genomic DNA was extracted from peripheral blood samples using QIAamp DNA Blood Mini Kit (Qiagen, Valencia, CA, USA) according to the manufacturer’s protocol. The 384-well ABI 7900HT RT-PCR System (Applied Biosystems, Foster City, CA, USA) was used for the TaqMan SNP genotyping assay. For experimental confirmation, results were repeated by sequencing the randomly selected 10 % PCR products. Statistical analyses The Hardy–Weinberg equilibrium (HWE) of alleles was evaluated for controls using the Chi-square test. The differences between gastric cancer cases and cancer-free controls were evaluated by Student’s t test (continuous variables) and Chi-square test (categorical variables). The associations of sequence polymorphisms and gastric cancer risk were measured by the odds ratios (ORs) with 95 % confidence intervals (CIs) using unconditional logistic regression. All data analyses were conducted at P value = 0.05 level of significance.
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Results Study characteristics The tumor characteristics of subjects between gastric cancer cases and cancer-free controls are summarized in Table 1. We totally analyzed a series of 642 gastric cancer patients and 720 cancer-free controls from a Chinese Han population for the polymorphisms of P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes. There were no significant differences in the distribution of age (P = 0.76), sex (P = 0.74), smoking habit (P = 0.76) and drinking habit (P = 0.78) between cases and controls. However, gastric cancer cases were significantly more likely to report a family history of cancer than the cancer-free controls (P \ 0.001). As for the tumor stage, 54 (8 %) cases were at I stage, 294 (45.9 %) cases were at II stage, 198 (31 %) cases were at III stage, and 96 (15.1 %) cases were at III stage. Association of polymorphisms and gastric cancer risk The genotype distribution of sequence polymorphisms of P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes in cases and controls is shown in Table 2. The genotype distributions in the control subjects were all in agreement with the HWE for all four SNPs (P = 0.61 for P53 rs1042522; P = 0.32 for MDM2 Table 1 Descriptive characteristics of gastric cancer cases and cancer-free controls Variables
Cases (n = 642) N (%)
Controls (n = 720) N (%)
P
Ages Sex
60.2 ± 11.2
61.4 ± 10.6
0.76
Male
366 (57 %)
423 (58.7 %)
0.74
Female
276 (43 %)
297 (41.3 %)
Smoking status Never
213 (33.2 %)
231 (32.1)
Ever
429 (66.8 %)
489 (67.9)
0.76
Drinking status Never
180 (28.4 %)
153 (21.3 %)
Ever
462 (71.6 %)
567 (78.7 %)
No
468 (73.1 %)
672 (93.3 %)
Yes
174 (26.9 %)
48 (6.7 %)
0.78
Family history
Tumor stage I
54 (8 %)
II
294 (45.9 %)
III IV
198 (31 %) 96 (15.1 %)
\0.001
Med Oncol (2015) 32:401
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rs2279744; P = 0.46 for MDM4 rs1380576 and P = 0.12 for Hausp rs1529916). The genotype distributions in gastric cancer cases are not quite significantly different from cancer-free controls (Table 2). Further logistic regression analysis revealed that the polymorphisms of P53 (rs1042522) and MDM2 (rs22797 44) are significantly associated with gastric cancer risk (P53 rs1042522: OR 1.69, 95 % CI 1.27–2.24 for CC vs. GG; OR 1.51, 95 % CI 1.17–1.94 for GC vs. GG; MDM2 rs2279744: OR 1.96, 95 % CI 1.47–2.61 for GG vs. TT; OR 1.63, 95 % CI 1.26–2.11 for TG vs. TT). However, no significant associations were observed between variant genotype of other two SNPs (MDM4 rs1380576 and Hausp rs1529916) and gastric cancer risk. We further evaluated the effect of polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) on gastric cancer risk in the subgroup stratified by age, sex, smoking habit and drinking habit. As shown in Tables 3 and 4, these two polymorphisms were associated with a significantly elevated risk of gastric cancer risk among older people (P53 rs1042522: OR 2.32, 95 % CI 1.70–3.16; MDM2 rs2279744: OR 1.75, 95 % CI 1.30–2.36), men (P53 rs1042522: OR 2.10, 95 % CI 1.52–2.90; MDM2 rs2279744: OR 2.48, 95 % CI 1.74–3.53), smokers (P53 rs1042522: OR 1.65, 95 % CI 1.23–2.22; MDM2 rs2279744: OR 1.97, 95 % CI 1.46–2.65) and drinkers (P53 rs1042522: OR 2.47, 95 % CI 1.83–3.35; MDM2 rs2279744: OR 2.54, 95 % CI 1.89–3.41). In addition, results from the multivariable logistic regression analysis showed that polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) are associated with gastric cancer (Table 5).
Table 3 Stratification analyses between P53 polymorphism and gastric cancer risk Variables
Cases (n = 642)
Controls (n = 720)
GG
GC ?CC
GG
GC ?CC
C60
92
312
154
225
2.32 (1.70, 3.16)
\60
73
165
100
241
0.93 (0.65, 1.34)
Male
77
289
152
271
2.10 (1.52, 2.90)
Female
88
188
102
195
1.11 (0.78, 1.58)
Age
Sex
Smoking status Never
67
146
93
138
1.46 (0.99, 2.17)
Ever
98
331
161
328
1.65 (1.23, 2.22)
Drinking status Never
89
91
68
85
0.81 (0.53, 1.26)
Ever
76
386
186
381
2.47 (1.83, 3.35)
Table 4 Stratification analyses between MDM2 polymorphism and gastric cancer risk Variables
Cases (n = 642)
Controls (n = 720)
P
0.096
OR (95 % CI)
GG
165
254
GC
285
291
1.51 (1.17, 1.94)
1.00
CC
192
175
1.69 (1.27, 2.24)
MDM2 (rs2279744) TT
153
255
TG
288
294
1.63 (1.26, 2.11)
GG
201
171
1.96 (1.47, 2.61)
0.088
1.00
MDM4 (rs1380576) 188 281
212 290
GG
173
218
Controls (n = 720)
TT
TG ? GG
TT
Adjusted OR (95 %)
TG ? GG
C60
98
310
160
288
1.75 (1.30, 2.36)
\60
67
167
94
178
1.31 (0.90, 1.92)
Sex Male
55
311
129
294
2.48 (1.74, 3.53)
110
166
125
172
1.09 (0.78, 1.53)
Smoking status Never
75
138
86
145
1.09 (0.74, 1.60)
Ever
90
339
168
321
1.97 (1.46, 2.65)
Drinking status
P53 (rs1042522)
CC CG
Cases (n = 642)
Age
Female Table 2 Distribution of genotypes of polymorphisms and gastric cancer cases and cancer-free controls
Adjusted OR (95 %)
0.497
1.00 1.09 (0.84, 1.41) 0.89 (0.67, 1.18)
Hausp (rs1529916) CC
172
222
TC
276
284
0.086
1.00 1.25 (0.97, 1.62)
TT
194
214
1.17 (0.89, 1.54)
Never
83
97
53
100
0.61 (0.39, 0.96)
Ever
82
380
201
366
2.54 (1.89, 3.41)
Gene–gene interaction between P53 and MDM2 polymorphisms Next, we examined whether there was a significant interaction between the P53 and MDM2 polymorphisms. As shown in Table 6, the presence of MDM2 TG genotype and P53 CC genotype is associated with an even higher risk of gastric cancer (OR 2.22, 95 % CI 1.30–3.76). Furthermore, the combinations of MDM2 GG genotype and P53 genotypes (GG, GC and CC) were also associated with gastric cancer risk (OR 2.36, 95 % CI 1.34–4.15; OR 1.61, 95 % CI 1.01–2.60; OR 1.77, 95 % CI 1.03–3.06), respectively. Our results indicated a super-multiplicative interaction
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Med Oncol (2015) 32:401
Table 5 Multivariable logistic regression analysis for gastric cancer risk Variable
P value
OR (95 % CI)
Age
0.21
1.01 (0.99, 1.12)
Sex
0.16
0.88 (0.94, 1.47)
Smoking status
0.89
0.92 (0.69, 1.28)
Drinking status
0.76
0.95 (0.92, 1.22)
P53 (rs1042522)
\0.001
1.31 (1.14, 1.66)
MDM2 (rs2279744)
\0.001
1.42 (1.18, 1.53)
Table 6 Interaction of MDM2 genotypes by P53 genotypes on gastric cancer risk MDM2 (rs2279744)
P53 (rs1042522)
Cases
Controls
OR (95 % CI)
TT
GG
44
68
1.00 (reference)
TT
GC
70
122
0.88 (0.54, 1.43)
TT
CC
39
65
0.92 (0.53, 1.60)
TG
GG
78
80
1.50 (0.92, 2.46)
TG
GC
141
166
1.31 (0.84, 2.04)
TG
CC
69
48
2.22 (1.30, 3.76)
GG
GG
55
36
2.36 (1.34, 4.15)
GG
GC
92
88
1.61 (1.01, 2.60)
GG
CC
54
47
1.77 (1.03, 3.06)
between P53 and MDM2 polymorphisms in the risk of gastric cancer in Chinese Han population.
Discussion This study investigated the possible association between polymorphisms in P53 signaling pathway P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) with gastric cancer risk in a Chinese Han population with cancer patients and cancer-free subjects. Our results indicated that the genotypes of P53 and MDM2 polymorphisms are statistically associated with gastric cancer risk. In addition, the association between the polymorphisms of P53 and MDM2 and the gastric cancer risk played a multiplicative gene–gene interaction, which rendered the cases carrying both polymorphisms to have an elevated risk of gastric cancer. Tumor suppressor protein P53 plays a pivotal role in coordinating cellular responses and maintaining genomic stability [20]. P53 is one of the most mutated genes in human tumors, and over 50 % of tumors harbor mutations in the p53 gene [21]. Genes, such as MDM2, MDM4 and Hausp, that interfere with the p53 pathway can also function as modifiers of cancer risk [22]. Association metaanalyses have been performed for P53 and MDM2
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polymorphisms with several other cancer risks [23–29]. Evidences suggested that it might have a significant correlation with elevated risk of breast, hepatocellular, leukemia and endometrial cancers. Therefore, these two polymorphisms might play different roles in different malignancies. MDM4 and Hausp are two important P53 regulators. Recent works have described the haplotype structure analysis and indicated the presence of functional polymorphisms in MDM4 and Hausp genes [30]. As for gastric cancer, several case–control studies have demonstrated inconsistent and even inverse relationship between polymorphisms of P53 and MDM2 genes and susceptibility of gastric cancer [19, 31, 32]. In the present study, it has been shown that the polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) have significant association with gastric cancer risk, whereas no evidence was found for the polymorphisms of MDM4 (rs1380576) and Hausp (rs1529916). Meta-analyses showed that P53 (rs1042522) and MDM2 (rs2279744) polymorphisms are both associated with gastric cancer risk in Asians [33, 34], which is consistent with our results. However, several potential limitations of our work should be taken into consideration. At first, our work is a hospital-based case–control study. So, it is difficult to completely exclude the selection bias, and the subjects may not be representative of the general population; second, male predominance can be observed from the gastric cancer patients (366 vs. 276), which might be explained by the fact that gastric cancer always occurs more commonly in male than in female. However, no significant difference was observed between gastric cancer patients and control subjects, indicating no influence of this variable on the conclusion; third, our results were generated from a Chinese Han population, and the possibility of confounding from ethnicity was reduced. It does not permit the extrapolation of our results to other ethnicities. In conclusion, the present study demonstrated that P53 and MDM2 polymorphisms are associated with gastric cancer risk in a Chinese Han population. Although the result does not permit extrapolation to other ethnic groups, the present conclusion might provide potential genetic modifiers for the gastric cancer in Chinese Han population. Acknowledgments This work was supported by Scientific Program of the Department of Education, Beijing, China (BJ4472014). Conflict of interest peting interests.
The authors declare that they have no com-
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ORIGINAL PAPER
Genetic association of single nucleotide polymorphisms in P53 pathway with gastric cancer risk in a Chinese Han population Guo-cong Wu • Zhong-tao Zhang
Received: 21 August 2014 / Accepted: 21 November 2014 / Published online: 6 December 2014 Ó Springer Science+Business Media New York 2014
Abstract The tumor suppressor gene P53 plays an important role in carcinogenesis, and the P53 pathway is central both in reducing cancer frequency and in mediating the response of cancer therapies. MDM2, MDM4 and Hausp genes are all critical regulators of the tumor suppressor P53. Many studies have evaluated the association of single nucleotide polymorphisms (SNPs) in P53 pathway with the risk of common cancers. However, the results are still inconclusive. In this work, we analyzed the association of SNPs in P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes with gastric cancer in a hospital-based Chinese Han population (642 cases and 720 cancer-free controls). We found that the polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) are associated with gastric cancer risk, whereas no significant association was observed between variant genotype of other two polymorphisms (MDM4 rs1380576 and Hausp rs1529916) and gastric cancer risk. Keywords P53 pathway Polymorphism Gastric cancer Chinese Han
Introduction Gastric cancer is the fourth most frequently diagnosed cancer and the second leading cause of cancer death
G. Wu Z. Zhang (&) Department of General Surgery, Beijing Friendship Hospital Affiliated with Capital Medical University, Beijing 100050, China e-mail: [email protected] G. Wu e-mail: [email protected]
worldwide [1]. It was estimated that over 70 % of newly diagnosed cases occur in developing countries. Like other complex diseases, gastric cancer is one of the complicated traits caused by both environmental and genetic factors [2]. In addition to exogenous factors, genetic polymorphisms in the carcinogen detoxification, DNA repair and cell proliferation processes are crucial in the development of gastric cancer. Recent genome-wide association studies have reported that some SNPs are associated with the susceptibility of gastric cancer [3, 4]. However, additional polymorphism sites that contribute to the susceptibility of gastric cancer require further investigation. The tumor suppressor P53 is involved in multiple pathways including apoptosis, cell cycle regulation, DNA repair and the maintenance of genetic integrity [5]. P53 has been proved to be one of the most commonly mutated genes in various types of cancers. The mutations of P53 gene can result in inactive state which is unable to initiate appropriate stress responses, leading to enhanced tumorigenic potential. Murine double minute 2 (MDM2) is one of the negative regulators of the tumor suppressor P53, which has been documented to be mutated in a variety of cancers [6]. It has been reported that MDM2 gene can bind to the N-terminus of P53 protein and inhibit its activity, resulting in P53 protein degradation via the ubiquitination pathway [7]. MDM4, a structural homologue of MDMD2, can bind to the amino terminus of P53 and function as an inhibitor of P53 activity [8]. Hausp (herpes virus-associated ubiquitin-specific protease) can stabilize MDM2, MDM4 and P53 via its deubiquitinase activity [9]. Many evidences have proved that abnormalities of genes in P53 pathway play a pivotal role in cancer [10]. Moreover, polymorphisms in these genes are important for the modulation of P53 function. For example, the polymorphism (rs2278744, T309G) in the promoter region of MDM2 gene can
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increase affinity for binding stimulatory protein 1 and result in an elevated expression level of MDM2 gene. The polymorphisms in P53 pathway have been suggested to be associated with the susceptibility of diverse cancers [11–19]. In this work, we genotyped four SNPs (P53 rs1042522, MDM2 rs2279744, MDM4 rs1380576 and Hausp rs1529916) in a hospital-based case–control study with the attempt to evaluate the association of polymorphisms and gastric cancer risk in a Chinese Han population.
Materials and methods Study subjects A total of 642 consecutive patients (366 males and 276 females) with newly diagnosed gastric cancer recruited at the Beijing Friendship Hospital, China, from May 2010 to October 2013 were enrolled as gastric cancer cases for this work. The 720 cancer-free controls (423 males and 297 females), who are free from any cancers, were randomly selected from healthy participants who visited the general health checkup division in the hospital. These case and control people are all Han Chinese from the same geographical region. Written informed consents were obtained from all case and control subjects, and the protocol was approved by the Research Ethics Committees of Beijing Friendship Hospital Affiliated with Capital Medical University. Genotyping A blood sample of 2–5 ml was drawn from each case or control subject. Genomic DNA was extracted from peripheral blood samples using QIAamp DNA Blood Mini Kit (Qiagen, Valencia, CA, USA) according to the manufacturer’s protocol. The 384-well ABI 7900HT RT-PCR System (Applied Biosystems, Foster City, CA, USA) was used for the TaqMan SNP genotyping assay. For experimental confirmation, results were repeated by sequencing the randomly selected 10 % PCR products. Statistical analyses The Hardy–Weinberg equilibrium (HWE) of alleles was evaluated for controls using the Chi-square test. The differences between gastric cancer cases and cancer-free controls were evaluated by Student’s t test (continuous variables) and Chi-square test (categorical variables). The associations of sequence polymorphisms and gastric cancer risk were measured by the odds ratios (ORs) with 95 % confidence intervals (CIs) using unconditional logistic regression. All data analyses were conducted at P value = 0.05 level of significance.
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Results Study characteristics The tumor characteristics of subjects between gastric cancer cases and cancer-free controls are summarized in Table 1. We totally analyzed a series of 642 gastric cancer patients and 720 cancer-free controls from a Chinese Han population for the polymorphisms of P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes. There were no significant differences in the distribution of age (P = 0.76), sex (P = 0.74), smoking habit (P = 0.76) and drinking habit (P = 0.78) between cases and controls. However, gastric cancer cases were significantly more likely to report a family history of cancer than the cancer-free controls (P \ 0.001). As for the tumor stage, 54 (8 %) cases were at I stage, 294 (45.9 %) cases were at II stage, 198 (31 %) cases were at III stage, and 96 (15.1 %) cases were at III stage. Association of polymorphisms and gastric cancer risk The genotype distribution of sequence polymorphisms of P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) genes in cases and controls is shown in Table 2. The genotype distributions in the control subjects were all in agreement with the HWE for all four SNPs (P = 0.61 for P53 rs1042522; P = 0.32 for MDM2 Table 1 Descriptive characteristics of gastric cancer cases and cancer-free controls Variables
Cases (n = 642) N (%)
Controls (n = 720) N (%)
P
Ages Sex
60.2 ± 11.2
61.4 ± 10.6
0.76
Male
366 (57 %)
423 (58.7 %)
0.74
Female
276 (43 %)
297 (41.3 %)
Smoking status Never
213 (33.2 %)
231 (32.1)
Ever
429 (66.8 %)
489 (67.9)
0.76
Drinking status Never
180 (28.4 %)
153 (21.3 %)
Ever
462 (71.6 %)
567 (78.7 %)
No
468 (73.1 %)
672 (93.3 %)
Yes
174 (26.9 %)
48 (6.7 %)
0.78
Family history
Tumor stage I
54 (8 %)
II
294 (45.9 %)
III IV
198 (31 %) 96 (15.1 %)
\0.001
Med Oncol (2015) 32:401
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rs2279744; P = 0.46 for MDM4 rs1380576 and P = 0.12 for Hausp rs1529916). The genotype distributions in gastric cancer cases are not quite significantly different from cancer-free controls (Table 2). Further logistic regression analysis revealed that the polymorphisms of P53 (rs1042522) and MDM2 (rs22797 44) are significantly associated with gastric cancer risk (P53 rs1042522: OR 1.69, 95 % CI 1.27–2.24 for CC vs. GG; OR 1.51, 95 % CI 1.17–1.94 for GC vs. GG; MDM2 rs2279744: OR 1.96, 95 % CI 1.47–2.61 for GG vs. TT; OR 1.63, 95 % CI 1.26–2.11 for TG vs. TT). However, no significant associations were observed between variant genotype of other two SNPs (MDM4 rs1380576 and Hausp rs1529916) and gastric cancer risk. We further evaluated the effect of polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) on gastric cancer risk in the subgroup stratified by age, sex, smoking habit and drinking habit. As shown in Tables 3 and 4, these two polymorphisms were associated with a significantly elevated risk of gastric cancer risk among older people (P53 rs1042522: OR 2.32, 95 % CI 1.70–3.16; MDM2 rs2279744: OR 1.75, 95 % CI 1.30–2.36), men (P53 rs1042522: OR 2.10, 95 % CI 1.52–2.90; MDM2 rs2279744: OR 2.48, 95 % CI 1.74–3.53), smokers (P53 rs1042522: OR 1.65, 95 % CI 1.23–2.22; MDM2 rs2279744: OR 1.97, 95 % CI 1.46–2.65) and drinkers (P53 rs1042522: OR 2.47, 95 % CI 1.83–3.35; MDM2 rs2279744: OR 2.54, 95 % CI 1.89–3.41). In addition, results from the multivariable logistic regression analysis showed that polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) are associated with gastric cancer (Table 5).
Table 3 Stratification analyses between P53 polymorphism and gastric cancer risk Variables
Cases (n = 642)
Controls (n = 720)
GG
GC ?CC
GG
GC ?CC
C60
92
312
154
225
2.32 (1.70, 3.16)
\60
73
165
100
241
0.93 (0.65, 1.34)
Male
77
289
152
271
2.10 (1.52, 2.90)
Female
88
188
102
195
1.11 (0.78, 1.58)
Age
Sex
Smoking status Never
67
146
93
138
1.46 (0.99, 2.17)
Ever
98
331
161
328
1.65 (1.23, 2.22)
Drinking status Never
89
91
68
85
0.81 (0.53, 1.26)
Ever
76
386
186
381
2.47 (1.83, 3.35)
Table 4 Stratification analyses between MDM2 polymorphism and gastric cancer risk Variables
Cases (n = 642)
Controls (n = 720)
P
0.096
OR (95 % CI)
GG
165
254
GC
285
291
1.51 (1.17, 1.94)
1.00
CC
192
175
1.69 (1.27, 2.24)
MDM2 (rs2279744) TT
153
255
TG
288
294
1.63 (1.26, 2.11)
GG
201
171
1.96 (1.47, 2.61)
0.088
1.00
MDM4 (rs1380576) 188 281
212 290
GG
173
218
Controls (n = 720)
TT
TG ? GG
TT
Adjusted OR (95 %)
TG ? GG
C60
98
310
160
288
1.75 (1.30, 2.36)
\60
67
167
94
178
1.31 (0.90, 1.92)
Sex Male
55
311
129
294
2.48 (1.74, 3.53)
110
166
125
172
1.09 (0.78, 1.53)
Smoking status Never
75
138
86
145
1.09 (0.74, 1.60)
Ever
90
339
168
321
1.97 (1.46, 2.65)
Drinking status
P53 (rs1042522)
CC CG
Cases (n = 642)
Age
Female Table 2 Distribution of genotypes of polymorphisms and gastric cancer cases and cancer-free controls
Adjusted OR (95 %)
0.497
1.00 1.09 (0.84, 1.41) 0.89 (0.67, 1.18)
Hausp (rs1529916) CC
172
222
TC
276
284
0.086
1.00 1.25 (0.97, 1.62)
TT
194
214
1.17 (0.89, 1.54)
Never
83
97
53
100
0.61 (0.39, 0.96)
Ever
82
380
201
366
2.54 (1.89, 3.41)
Gene–gene interaction between P53 and MDM2 polymorphisms Next, we examined whether there was a significant interaction between the P53 and MDM2 polymorphisms. As shown in Table 6, the presence of MDM2 TG genotype and P53 CC genotype is associated with an even higher risk of gastric cancer (OR 2.22, 95 % CI 1.30–3.76). Furthermore, the combinations of MDM2 GG genotype and P53 genotypes (GG, GC and CC) were also associated with gastric cancer risk (OR 2.36, 95 % CI 1.34–4.15; OR 1.61, 95 % CI 1.01–2.60; OR 1.77, 95 % CI 1.03–3.06), respectively. Our results indicated a super-multiplicative interaction
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Table 5 Multivariable logistic regression analysis for gastric cancer risk Variable
P value
OR (95 % CI)
Age
0.21
1.01 (0.99, 1.12)
Sex
0.16
0.88 (0.94, 1.47)
Smoking status
0.89
0.92 (0.69, 1.28)
Drinking status
0.76
0.95 (0.92, 1.22)
P53 (rs1042522)
\0.001
1.31 (1.14, 1.66)
MDM2 (rs2279744)
\0.001
1.42 (1.18, 1.53)
Table 6 Interaction of MDM2 genotypes by P53 genotypes on gastric cancer risk MDM2 (rs2279744)
P53 (rs1042522)
Cases
Controls
OR (95 % CI)
TT
GG
44
68
1.00 (reference)
TT
GC
70
122
0.88 (0.54, 1.43)
TT
CC
39
65
0.92 (0.53, 1.60)
TG
GG
78
80
1.50 (0.92, 2.46)
TG
GC
141
166
1.31 (0.84, 2.04)
TG
CC
69
48
2.22 (1.30, 3.76)
GG
GG
55
36
2.36 (1.34, 4.15)
GG
GC
92
88
1.61 (1.01, 2.60)
GG
CC
54
47
1.77 (1.03, 3.06)
between P53 and MDM2 polymorphisms in the risk of gastric cancer in Chinese Han population.
Discussion This study investigated the possible association between polymorphisms in P53 signaling pathway P53 (rs1042522), MDM2 (rs2279744), MDM4 (rs1380576) and Hausp (rs1529916) with gastric cancer risk in a Chinese Han population with cancer patients and cancer-free subjects. Our results indicated that the genotypes of P53 and MDM2 polymorphisms are statistically associated with gastric cancer risk. In addition, the association between the polymorphisms of P53 and MDM2 and the gastric cancer risk played a multiplicative gene–gene interaction, which rendered the cases carrying both polymorphisms to have an elevated risk of gastric cancer. Tumor suppressor protein P53 plays a pivotal role in coordinating cellular responses and maintaining genomic stability [20]. P53 is one of the most mutated genes in human tumors, and over 50 % of tumors harbor mutations in the p53 gene [21]. Genes, such as MDM2, MDM4 and Hausp, that interfere with the p53 pathway can also function as modifiers of cancer risk [22]. Association metaanalyses have been performed for P53 and MDM2
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polymorphisms with several other cancer risks [23–29]. Evidences suggested that it might have a significant correlation with elevated risk of breast, hepatocellular, leukemia and endometrial cancers. Therefore, these two polymorphisms might play different roles in different malignancies. MDM4 and Hausp are two important P53 regulators. Recent works have described the haplotype structure analysis and indicated the presence of functional polymorphisms in MDM4 and Hausp genes [30]. As for gastric cancer, several case–control studies have demonstrated inconsistent and even inverse relationship between polymorphisms of P53 and MDM2 genes and susceptibility of gastric cancer [19, 31, 32]. In the present study, it has been shown that the polymorphisms of P53 (rs1042522) and MDM2 (rs2279744) have significant association with gastric cancer risk, whereas no evidence was found for the polymorphisms of MDM4 (rs1380576) and Hausp (rs1529916). Meta-analyses showed that P53 (rs1042522) and MDM2 (rs2279744) polymorphisms are both associated with gastric cancer risk in Asians [33, 34], which is consistent with our results. However, several potential limitations of our work should be taken into consideration. At first, our work is a hospital-based case–control study. So, it is difficult to completely exclude the selection bias, and the subjects may not be representative of the general population; second, male predominance can be observed from the gastric cancer patients (366 vs. 276), which might be explained by the fact that gastric cancer always occurs more commonly in male than in female. However, no significant difference was observed between gastric cancer patients and control subjects, indicating no influence of this variable on the conclusion; third, our results were generated from a Chinese Han population, and the possibility of confounding from ethnicity was reduced. It does not permit the extrapolation of our results to other ethnicities. In conclusion, the present study demonstrated that P53 and MDM2 polymorphisms are associated with gastric cancer risk in a Chinese Han population. Although the result does not permit extrapolation to other ethnic groups, the present conclusion might provide potential genetic modifiers for the gastric cancer in Chinese Han population. Acknowledgments This work was supported by Scientific Program of the Department of Education, Beijing, China (BJ4472014). Conflict of interest peting interests.
The authors declare that they have no com-
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