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Human Cancer Biology |
Authors' Affiliations: 1 Department of Biosciences at Novum, Karolinska Institute, Huddinge, Sweden, 2 Division of Molecular Genetic Epidemiology, German Cancer Research Center and 3 Institute of Human Genetics, University of Heidelberg, Heidelberg, Germany, 4 Department of Public Health and Clinical Medicine/Nutritional Research, Umeå University and 5 Department of Oncology, Norrlands University Hospital, Umeå, Sweden, 6 Department of Tumor Biology, 7 I Clinics of Radiotherapy, and 8 Clinics of Chemotherapy, Centre of Oncology, Maria Sklodowska-Curie Institute, Gliwice, Poland
Requests for reprints: Qianren Jin, Department of Biosciences at Novum, Karolinska Institute, SE-141 57, Huddinge, Sweden. Phone: 46-8-608-9238; Fax: 46-8-608-1501; E-mail: qianren.jin{at}cnt.ki.se.
| Abstract |
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Experimental Design: We examined three polymorphisms in the VEGF gene (2578C/A, 1154G/A, and +936C/T) in 571 familial breast cancer cases from Poland and Germany and 2578C/A, 634G/C, and +936C/T polymorphisms in 974 unselected breast cancer cases from Sweden together with ethnically and geographically selected controls.
Results: None of the polymorphisms or any haplotype was significantly associated with either familial or unselected breast cancers. Our study suggests that the +936C/T polymorphism is unlikely to be associated with breast cancer. We also analyzed the unselected cases for genotypes or haplotypes that associated with tumor characteristics. The 634CC genotype and the 2578/634 CC haplotype were significantly associated with high tumor aggressiveness (large tumor size and high histologic grade, P < 0.01) and the 2578AA genotype and the 2578/634 AG haplotype with low histologic grade tumors (P = 0.04). The genotypes and haplotypes were not related with other tumor characteristics such as regional or distant metastasis, stage at diagnosis, or estrogen or progesterone receptor status.
Conclusions: Although none of the polymorphisms studied in the VEGF gene was found to influence susceptibility to breast cancer significantly, some of the VEGF genotypes and haplotypes may influence tumor growth through an altered expression of VEGF and tumor angiogenesis.
Key Words: VEGF genotype haplotype case-control study
In the present study, we investigated the relationship between genetic polymorphisms in the VEGF gene and the development of breast cancer in patients from Poland, Germany, and Sweden. Five of the polymorphisms were located in the promoter region at positions 2578, 2549, 2489, 2447, and 1154, one in the 5' untranslated region at position 634 relative to the translation starting site, and the seventh one in the 3'untranslated region at position +936, according to the numbering used by Renner et al. (ref. 8; Fig. 1). From these seven polymorphisms, four were selected for further analysis to evaluate their possible influence on the risk to breast cancer and the prognostic characteristics of the tumors.
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| Materials and Methods |
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RFLP analysis. The 2578C/A, as a marker for the completely linked polymorphisms 2578C/A, 2549del/ins 18 bp, 2489C/T, and 2447del G, and +936C/T polymorphisms were analyzed in the familial sample sets using RFLP analysis. The assays were set up after PCR as described (16). PCR products were digested with the MvaI and Hsp92II restriction endonuleases, respectively, using the buffers and temperatures recommended by the manufacturers. The digested PCR products were resolved on a 10% polyacrylamide gel (Bio-Rad, Hercules, CA) and stained with ethidium bromide for visualization under UV light.
ALF express fragment analysis. ALF express fragment analysis was employed to analyze the 1154G/A polymorphism in the VEGF gene. The forward primer was labeled with a Cy5 fluorescence dye. After digestion with MnlI, PCR products were electrophoresed and detected using an automated ALF Express sequencer (Amersham Pharmacia). The results were analyzed using software package Fragment Manager as described earlier (17).
The genotyping results after the RFLP and ALF Express analyses were read by two independent individuals. About 10% of the PCR-RFLP and PCR-ALF assays were randomly repeated and the results were checked for concordance.
Taqman assay. The 2578C/A, 634G/C, +936C/T polymorphisms were analyzed in the Swedish populations by the Umeå Center for Genome Research, Medical and Clinical Genetics, Umeå University, Sweden, using Taqman PCR. The primers and probes were designed using the Assay-by-Design service (Applied Biosystems, Foster City, CA) and the sequences are available by the corresponding author upon request. The assays were carried out using the standard method recommended by Applied Biosystems. The results were automatically read using the ABI PRISM 7900 HT Sequence Detection System.
DNA sequencing. DNA sequencing on three random samples from each genotype for all the polymorphisms was used to confirm the genotypes following PCR-RFLP, PCR-ALF, and Taqman assays as described (16).
Haplotype and linkage disequilibrium analysis. Haplotypes and linkage disequilibrium between the polymorphisms of the VEGF gene were determined based on the genotypes of all individuals participating in the study using a Haploview program (version 2.05, http://www.broad.mit.edu/personal/jcbarret/haploview/).
Statistical analysis. The differences in the genotype and haplotype frequencies of the studied polymorphisms in the breast cancer cases and controls were compared for statistical significance by the Yates corrected
2 test. The statistical significance for deviations from Hardy-Weinberg equilibrium was tested using the Pearson
2 test. Odds ratios and 95% confidence intervals were calculated for associations between genotypes and breast cancer and tumor characteristics. The joint analyses were carried out using a Mantel-Haenszel adjustment with each series as a separate stratum. For a polymorphism with a variant allele frequency between 10% and 50%, the study had >90% power to detect a 1.8- to 1.5-fold increase of relative risk in all familial cases and a 1.5- to 1.3-fold increased risk in all cases. All the statistical tests were carried out using Epi Info 2000 software (http://www.cdc.gov/epiinfo).
| Results |
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The genotype distribution of all studied polymorphisms followed the Hardy-Weinberg equilibrium in every sample set (P = 0.13-1.00). The genotype and allele distributions among the breast cancer cases and control subjects are shown in Table 2. The number of samples analyzed for each polymorphism was not exactly equal because of unsuccessful amplification of a few samples. No differences in the allele or genotype frequencies between the breast cancer cases and controls were detected in any population. Nor did the joint analysis show any differences between the breast cancer cases and controls (Table 2). The lack of association remained when the data were stratified by age (data not shown).
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0.005). There was a significant trend to larger tumor size with the increasing copy number of the haplotype (Ptrend = 0.008), and individuals with two copies of the haplotype had both significantly larger and higher-grade tumors (P = 0.005). A less significant association was observed between the haplotype 2578/634 AG and a lower tumor grade (P = 0.04) and only in carriers of two copies of this haplotype. Carriers of the 634 C allele tended to have more often estrogen receptorpositive tumors than carriers of the GG genotype. Because this effect was linked only to heterozygous carriers, the results are difficult to interpret. There were no indications that the polymorphisms would have any effects on the other tumor characteristics (Table 3). Addition of the information of the +936C/T polymorphism data did not change the results (data not shown).
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| Discussion |
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The allele and genotype distributions of the four polymorphisms were in close agreement with those previously published for healthy Caucasian individuals (8, 11, 12, 1821). In a previous study among 500 Caucasian breast cancer cases and 500 controls, Krippl et al. have shown a decreased risk of breast cancer in individuals who were +936 T allele carriers (9). However, the genotypes in patients did not follow the Hardy-Weinberg equilibrium. In another study, no association between the +936 polymorphism and risk to breast cancer among 862 cases and 713 controls could be observed (21). Here, we did a large case-control study of 1,489 women with breast cancer, including 565 women with familial breast cancer from Poland and Germany and 924 unselected breast cancer cases from Sweden. The use of familial cases can substantially increase the power of association studies as shown earlier (22, 23). We observed no differences in the allele or genotype frequencies between either the familial or unselected breast cancer case and respective control groups, nor did the joint analyses show any differences between the cases and controls (odds ratio, 0.99; 95% confidence interval, 0.85-1.15; P = 0.93). To our knowledge, no other studies on the effect of the other polymorphisms on the risk of breast cancer have been published. In our study, no significant differences in the allele, genotype or haplotype distribution of the polymorphisms in the VEGF gene between the familial and unselected breast cancer cases and respective controls were detected. Being the largest study thus far, and with one third being familial cases, our study provided strong evidence that the +936 T allele or the other studied polymorphisms do not modify the risk of breast cancer. This result is not surprising, because VEGF, as a key mediator of angiogenesis, is more likely to alter the aggressiveness of the tumor than susceptibility to cancer.
Among the unselected breast cancer cases, we observed a significant correlation between the 634CC genotype and a larger tumor size and a higher histologic grade of the tumors. In addition, the haplotype 2578/634 CC was associated with more aggressive tumors. In addition, our results showed that the 634GG genotype correlated with less aggressive tumors and the 2578AA genotype and the haplotype 2578/634 AG with low-grade tumors. Our results are in contrast to the study of Howell et al. who have reported an association between the rare 2578/1154/634 CAC haplotype and a less advanced melanoma (11). However, our results are in agreement with the reports regarding the effect of the polymorphisms on VEGF production. The 634CC genotype has been reported to be associated with higher serum levels of VEGF than the GG genotype (7) and the two common haplotypes 2578/1154/634 AAG and AGG with a decreased transcription of the VEGF gene and lower circulating levels of VEGF (19). Moreover, the 2578CC genotype and the 2578C allele have been reported to correlate with a higher VEGF production than the A allele in vitro (5, 6).
In summary, the present study investigated polymorphisms in the VEGF gene in a large case-control study. None of the polymorphisms alone or in combination with each other was found to influence the risk of breast cancer, either in the familial or unselected cases. Our study provided evidence that the +936C/T polymorphism is not associated with breast cancer risk. However, some genotypes and haplotypes in the VEGF gene may have an effect on breast tumor growth. Functional studies of the haplotypes and an independent study are needed to confirm our results. The polymorphisms should also be studied in relation to metastasis and survival and whether they influence therapeutic effects.
| Acknowledgments |
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| Footnotes |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 9/ 3/04; revised 2/ 3/05; accepted 2/22/05.
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