Transforming growth factor-beta1 genotype in sporadic breast cancer patients from India: status of enhancer, promoter, 5'-untranslated-region and exon-1 polymorphisms

A meta-analysis and in silico analysis of polymorphic variants conferring breast cancer risk in the Indian subcontinent

Background: Genetic association studies on breast cancer on the Indian subcontinent have yielded conflicting results, and the precise effect of these variants on breast cancer pathogenesis is not known. Methods: Genomic variants, as obtained from selected studies from the Indian subcontinent, were subjected to random-effects and fixed-effect meta-analysis. Functional annotation of the relevant variants was done through a tried and tested in silico pipeline. Results: We found rs4646903/CYP1A1, rs1799814/CYP1A1, rs61886492/GCPII, del2/GSTM1, rs4680/COMT and rs1801394/MTRR to be associated with breast cancer. The del2/GSTM1 holds the association in premenopausal women. Conclusions: This is the first study of its kind from the Indian subcontinent analysing the extent of association of variants across populations followed by their functional annotation in the disease pathway.

Association of TGF-β1 Polymorphisms with Breast Cancer Risk: A Meta-Analysis of Case-Control Studies †

Reports on the association of TGF-β1 polymorphisms with breast cancer (BC) have been conflicting, inconsistent, inconclusive, and controversial. PubMed, EMBASE, and Google Scholar were used to identify studies on TGF-β1 polymorphisms and BC risk. Data were extracted independently, and of the initial 3043 studies, 39 case-control studies were eligible for inclusion in the meta-analysis. Information from these studies was extracted, and the overall associations of three TGF-β1 polymorphisms (TGF-β1 29>T/C, TGF-β1-509 C/T, and TGF-β1*6A) with BC risk were analyzed using overall allele, homozygous, heterozygous, recessive, and dominant models. None of the three TGF-β1 polymorphisms studied had a significant influence on the development of BC. However, stratified analysis revealed a positive correlation between the TGF-β1 29T>C polymorphism and BC risk according to a heterozygous model of the Asian population (odds ratio (OR) = 1.115, 95% confidence interval (CI) = 1.006–1.237, p = 0.039). Interestingly, this polymorphism was associated with lower odds of BC according to a heterozygous model of the Middle Eastern population (OR = 0.602, 95% CI = 0.375–0.966, p = 0.035). Thus, our analysis of large datasets indicates that the TGF-β1 29T>C polymorphism is significantly associated with BC risk in the Asian population. In contrast, the TGF-β1*6A and TGF-β1-509 C/T polymorphisms failed to show an association with BC.

Transforming growth factor beta 1 polymorphisms and haplotypes associated with breast cancer susceptibility: A case-control study in Tunisian women

Variable association of transforming growth factor beta 1 (TGFβ1) in breast cancer (BC) pathogenesis was documented, and the contribution of specific TGFB1 polymorphisms to the progression of BC and associated features remains poorly understood. We investigated the contribution of TGFB1 rs1800469, rs1800470, rs1800471, and rs1800472 variants and 4-locus TGFB1 haplotypes on BC susceptibility, and pathological presentation of BC subtypes. Study subjects comprised 430 female BC cases, and 498 cancer-free control women. BC-associated pathological parameters were also evaluated for correlation with TGFB1 variants. Results obtained showed that the minor allele frequency (MAF) of rs1800471 (+74G>C) was higher seen in BC cases than in control subjects, and was associated with increased risk of BC. Significant differences in rs1800471 and rs1800469 (-509C>T) genotype distribution were noted between BC cases and controls, which persisted after controlling for key covariates. TGFB1 rs1800472 was positively, while rs1800470 was negatively associated with triple negativity, while rs1800470 positively correlated with menarche, but negatively with tumor size and molecular type, and rs1800469 correlated positively with menstrual irregularity, distant metastasis, nodal status, and hormonotherapy. Heterogeneity in LD pattern was noted between the tested TGFB1 variants. Four-locus (rs1800472-rs1800471-rs1800470-rs1800469) Haploview analysis identified haplotype TGCT to be negatively associated, and haplotypes CGTT and CCCC to be positively associated with BC. This association of CGTT and CCCC, but not TGCT, with BC remained significant after controlling for key covariates. In conclusion, TGFB1 alleles and specific genotypes, and 4-locus TGFB1 haplotypes influence BC susceptibility, suggesting dual association imparted by specific SNP, consistent with dual role for TGFB1 in BC pathogenesis.

Novel alleles of the transforming growth factor β-1 regulatory region and exon 1

Transforming growth factor β-1, encoded by the TGFB1 gene, is a cytokine that plays a central role in many physiologic and pathogenic processes with pleiotropic effects. Regulatory activity for this gene has been shown for 3.0 kb between positions -2665 and +423 from its translational start site. At least 17 TGFB1 regulatory region and exon 1 alleles have been defined on the basis of 18 polymorphic sites. Polymorphisms in TGFB1's regulatory region have been associated with differential levels of expression of this cytokine and to genetic risk in cancer and transplantation. In this report, we present 19 novel TGFB1 regulatory region and exon 1 alleles: p018-p036. Amplification of TGFB1's regulatory region was performed with an in-house protocol, and novel alleles were defined by either allele-specific amplification and/or molecular cloning of the amplicons, followed by sequencing in isolation. Three of these novel alleles (p018, p019, and p020) are shown to be formed by novel combinations of the aforementioned known polymorphic positions. Another 16 novel alleles are shown to carry additional known and unknown single-nucleotide polymorphisms. Polymorphism in TGFB1's regulatory region could have an impact on important processes, including embryogenesis, hematopoiesis, carcinogenesis, angiogenesis, fibrosis, immune responses, and transplantation, making its characterization necessary.

Correlation between TGF-β1 gene 29 T > C single nucleotide polymorphism and clinicopathological characteristics of osteosarcoma

Transforming growth factor (TGF)-β1 is the most abundant growth factor in human bone. Several polymorphisms have been described in the TGF-β1 gene. To explore the correlation between TGF-β1 gene single nucleotide polymorphism and the clinicopathological characteristics of osteosarcoma. TaqMAN PCR technique was used to detect the TGF-β1 gene polymorphism of 124 patients with osteosarcoma from last follow-up and 136 healthy controls. The difference of gender, age, and allele frequency between patient group and control group with χ (2) text were tested. The relationship between single nucleotide polymorphism and the risk of osteosarcoma with logistic regression and different survival rates of different genotypic patients with osteosarcoma through Kaplan-Meier were analyzed. There is no remarkable difference of the three genotypes in TGF-β1 gene 509C > T locus between the patient group and control group (P = 0.26). However, there are significant distributive differences in 29 T > C genotype (P = 0.04), which shows that patients carrying TT genotype have more risk to get osteosarcoma than patients carrying CC genotype (odds ratio (OR) = 2.10, 95 % confidence interval (CI) = 1.08-4.05). The percentage of T allele frequency of patient group, as 60.1 %, is larger than the control group, as 48.9 %. By comparing with patients carrying CC genotype, patients carrying TT genotype have two times risk of metastasis (OR = 2.30, 95 % CI = 1.05-5.06), and most of them are in the period of Enneking IIB (OR = 2.54, 95 % CI = 1.18-5.51). The survival analysis indicates that there is no any significant decrease when there is recurrence in patients carrying TT genotype. The morbidity and metastasis of osteosarcoma are relevant to TGF-β1 gene 29 T > C single nucleotide polymorphism.

Apoptosis regulatory protein-protein interaction demonstrates hierarchical scale-free fractal network

Dysregulation or inhibition of apoptosis favors cancer and many other diseases. Understanding of the network interaction of the genes involved in apoptotic pathway, therefore, is essential, to look for targets of therapeutic intervention. Here we used the network theory methods, using experimentally validated 25 apoptosis regulatory proteins and identified important genes for apoptosis regulation, which demonstrated a hierarchical scale-free fractal protein-protein interaction network. TP53, BRCA1, UBIQ and CASP3 were recognized as a four key regulators. BRCA1 and UBIQ were also individually found to control highly clustered modules and play an important role in the stability of the overall network. The connection among the BRCA1, UBIQ and TP53 proteins was found to be important for regulation, which controlled their own respective communities and the overall network topology. The feedback loop regulation motif was identified among NPM1, BRCA1 and TP53, and these crucial motif topologies were also reflected in high frequency. The propagation of the perturbed signal from hubs was found to be active upto some distance, after which propagation started decreasing and TP53 was the most efficient signal propagator. From the functional enrichment analysis, most of the apoptosis regulatory genes associated with cardiovascular diseases and highly expressed in brain tissues were identified. Apart from TP53, BRCA1 was observed to regulate apoptosis by influencing motif, propagation of signals and module regulation, reflecting their biological significance. In future, biochemical investigation of the observed hub-interacting partners could provide further understanding about their role in the pathophysiology of cancer.

Strong impact of TGF-β1 gene polymorphisms on breast cancer risk in Indian women: a case-control and population-based study

Introduction

TGF-β1 is a multi-functional cytokine that plays an important role in breast carcinogenesis. Critical role of TGF-β1 signaling in breast cancer progression is well documented. Some TGF-β1 polymorphisms influence its expression; however, their impact on breast cancer risk is not clear.

Methods

We analyzed 1222 samples in a candidate gene-based genetic association study on two distantly located and ethnically divergent case-control groups of Indian women, followed by a population-based genetic epidemiology study analyzing these polymorphisms in other Indian populations. The c.29C>T (Pro10Leu, rs1982073 or rs1800470) and c.74G>C (Arg25Pro, rs1800471) polymorphisms in the TGF-β1 gene were analyzed using direct DNA sequencing, and peripheral level of TGF-β1 were measured by ELISA.

Results

c.29C>T substitution increased breast cancer risk, irrespective of ethnicity and menopausal status. On the other hand, c.74G>C substitution reduced breast cancer risk significantly in the north Indian group (p = 0.0005) and only in the pre-menopausal women. The protective effect of c.74G>C polymorphism may be ethnicity-specific, as no association was seen in south Indian group. The polymorphic status of c.29C>T was comparable among Indo-Europeans, Dravidians, and Tibeto-Burmans. Interestingly, we found that Tibeto-Burmans lack polymorphism at c.74G>C locus as true for the Chinese populations. However, the Brahmins of Nepal (Indo-Europeans) showed polymorphism in 2.08% of alleles. Mean TGF-β1 was significantly elevated in patients in comparison to controls (p<0.001).

Conclusion

c.29C>T and c.74G>C polymorphisms in the TGF-β1 gene significantly affect breast cancer risk, which correlates with elevated TGF-β1 level in the patients. The c.29C>T locus is polymorphic across ethnically different populations, but c.74G>C locus is monomorphic in Tibeto-Burmans and polymorphic in other Indian populations.

Association of TGF-β1 -509C/T polymorphisms with breast cancer risk: evidence from an updated meta-analysis

Epidemiological studies have evaluated the association between transforming growth factor-β1 (TGF-β1) -509C/T polymorphisms and breast cancer risk. However, the results remain conflicting rather than conclusive. The aim of this study was to comprehensively clarify the association between TGF-β1 -509C/T polymorphisms and breast cancer risk. All relevant studies were searched in the electronic databases. The potential sources of heterogeneity were detected with the chi-square-based Q test. The strength of associations between TGF-β1 -509C/T polymorphisms and breast cancer risk was measured by odds ratio (OR) and 95 % confidence intervals (CI). Publication bias was tested by Begg's test and Egger's test. A total of 10 studies including 10,913 cases and 14,187 controls were included in the meta-analysis. Overall, there was no evidence of significant association of TGF-β1 -509C/T polymorphisms with breast cancer risk (TT vs. CC [OR = 0.97, 95 % CI = 0.83-1.14]; CT vs. CC [OR = 1.05, 95 % CI = 0.90-1.22]; TT + CT vs. CC [OR = 0.99, 95 % CI = 0.91-1.08]; T allele vs. C allele [OR = 0.99, 95 % CI = 0.93-1.06]). Similar results were also found in the subgroup analyses by ethnicity and source of control. When stratified by estrogen receptor (ER) status, TT genotype and T allele were associated with a decreased ER-positive breast cancer risk (OR = 0.66, 95 % CI = 0.49-0.90 and OR = 0.85, 95 % CI = 0.75-0.96, respectively). The present meta-analysis results suggest that TGF-β1 -509C/T variants may not contribute to the risk of breast cancer overall. However, T allele may be a potential protective factor for developing ER-positive breast cancer. Well-designed studies with larger sample size were required to verify our findings further.

Transforming growth factor beta-1 C-509T polymorphism and cancer risk: a meta-analysis of 55 case-control studies

AIM

To investigate the association of transforming growth factor-beta 1 (TGF-β1) C-509T polymorphism and susceptibility to cancer by means of meta-analysis.

METHODS

An extensive search was performed to identify eligible case-control studies investigating such a link. The strength of the association between TGF-β1 C-509T polymorphism and cancer risk was assessed by pooled odds ratios (ORs) and 95%confidence intervals (95%CIs) in fixed or random effects models.

RESULTS

55 published case-control studies with a total number of 21,639 cases and 28,460 controls were included. Overall, there was no association between TGF-β1 C-509T and cancer risk in all genetic comparison models (TT vs. CC: OR=1.01, 95%CI=0.89-1.15; T vs. C: OR=1.01, 95%CI=0.94-1.07). However, a stratified analysis by cancer type indicated -509 T allele was significantly associated with decreased risk of colorectal cancer (CRC) (TT vs. CT/CC: OR=0.85, 95%CI=0.76-0.95), especially for Caucasians (TT vs. CT/CC: OR=0.83, 95%CI=0.71-0.98) and for population-based studies (TT vs. CT/CC: OR=0.78, 95%CI=0.68- 0.89).

CONCLUSION

This meta-analysis suggested that TGF-β1 C-509T polymorphism might contribute to a decreased risk on colorectal cancer susceptibility, especially for Caucasians.

Relationship between a TGF-β1 gene polymorphism and HBV infection and familial clustering of hepatocellular carcinoma

AIM: To investigate the relationship between a single nucleotide polymorphism (SNP) of the TGF-β1 gene (rs1800469) and HBV infection and familial clustering of hepatocellular carcinoma in Guangxi, China.

METHODS: Blood samples collected from 114 family members (FHCC) whose families have had two or even more hepatocellular carcinoma patients and 114 healthy controls (FNC) who come from the families without any cancer. SNP genotyping was performed in these subjects using DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism.

RESULTS: There were no statistical differences between the FHCC group and FNC group in the frequencies of the alleles (T, C) and genotypes (CC, TC, TT) at the rs1800469 locus, and in the distribution of the alleles (T, C) and frequencies of genotypes (TC, TT) between subjects who were infected by chronic hepatitis B (HBsAg positive) and those who were not infected (HBsAg negative) (all P > 0.05). However, there was a statistical difference in the frequency of genotype CC between the HBsAg-positive and -negative groups (P < 0.05).

CONCLUSION: The alleles (T, C) and genotypes (CC, TC, TT) at the rs1800469 locus in the TGF-β1 gene are not associated with familial clustering of hepatocellular carcinoma in families in Guangxi Province. The genotype CC at the rs1800469 locus might increase the risk for HBV infection.

Association of functional -509C>T polymorphism in the TGF-β1 gene with infiltrating ductal breast carcinoma risk in a Russian Western Siberian population

BACKGROUND

Transforming growth factor β1 (TGF-β1) is a multifunctional cytokine that plays an important role in human mammary carcinogenesis. The purpose of this study was to investigate the association between -509C>T single nucleotide polymorphism (SNP) of the TGF-β1 gene and infiltrating ductal breast carcinoma risk in Russian patients of Western Siberian region.

MATERIALS AND METHODS

Blood samples collected from 218 women with histologically confirmed infiltrating ductal breast carcinoma and 290 healthy female controls were analyzed through polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

The -509TT genotype was significantly associated with a decreased risk for ductal breast carcinoma (OR=0.47, CI: 0.26-0.82, P=0.004). Similarly, the -509T was significantly less in ductal breast cancer patients (34.4%) than in control individuals (41.6%; OR=0.74, CI: 0.57-0.96, P=0.02). With the exception of association between the -509TT genotype and large tumor size (P=0.01), there was no significant association between the studied polymorphism and clinicopathological characteristics.

CONCLUSION

The results of this study suggest that polymorphism of TGF-β1 -509C>T gene may modify individual susceptibility to infiltrating ductal breast carcinoma in Russian women of Western Siberian region.

Investigation of DNA damage response and apoptotic gene methylation pattern in sporadic breast tumors using high throughput quantitative DNA methylation analysis technology

Background-

Sporadic breast cancer like many other cancers is proposed to be a manifestation of abnormal genetic and epigenetic changes. For the past decade our laboratory has identified genes involved in DNA damage response (DDR), apoptosis and immunesurvelliance pathways to influence sporadic breast cancer risk in north Indian population. Further to enhance our knowledge at the epigenetic level, we performed DNA methylation study involving 17 gene promoter regions belonging to DNA damage response (DDR) and death receptor apoptotic pathway in 162 paired normal and cancerous breast tissues from 81 sporadic breast cancer patients, using a high throughput quantitative DNA methylation analysis technology.

Results-

The study identified five genes with statistically significant difference between normal and tumor tissues. Hypermethylation of DR5 (P = 0.001), DCR1 (P = 0.00001), DCR2 (P = 0.0000000005) and BRCA2 (P = 0.007) and hypomethylation of DR4 (P = 0.011) in sporadic breast tumor tissues suggested a weak/aberrant activation of the DDR/apoptotic pathway in breast tumorigenesis. Negative correlation was observed between methylation status and transcript expression levels for TRAIL, DR4, CASP8, ATM, CHEK2, BRCA1 and BRCA2 CpG sites. Categorization of the gene methylation with respect to the clinicopathological parameters showed an increase in aberrant methylation pattern in advanced tumors. These uncharacteristic methylation patterns corresponded with decreased death receptor apoptosis (P = 0.047) and DNA damage repair potential (P = 0.004) in advanced tumors. The observation of BRCA2 -26 G/A 5'UTR polymorphism concomitant with the presence of methylation in the promoter region was novel and emerged as a strong candidate for susceptibility to sporadic breast tumors.

Conclusion-

Our study indicates that methylation of DDR-apoptotic gene promoters in sporadic breast cancer is not a random phenomenon. Progressive epigenetic alterations in advancing tumors result in aberrant DDR-apoptotic pathway thereby promoting tumor development. We propose, since pathological epigenetic changes of the DDR-apoptotic genes are reversible modifications, these could further be targeted for therapeutic interventions.

Polymorphisms in cytokine genes and serum cytokine levels among New Mexican women with and without breast cancer

Among New Mexican Hispanic women, breast cancer is detected at a more advanced stage than compared to Non-Hispanic White women. One central factor that has been little studied is the role of critical cytokines. We genotyped incident breast cancer cases and their age-, gender- and smoking-matched controls (N=40 matched pairs) for 25 single nucleotide polymorphisms (SNPs) in cytokine genes. We measured corresponding serum cytokine levels as well. Five cytokines (IL-1beta, IL-5, TNF-alpha, IL-6 and IL-2) were significantly associated with disease and based on their serum levels, concentrations were higher in the cases than in the controls. Disease odds ratios corresponding to one standard deviation change in log-transformed concentrations of these cytokines were 18.87, 4.10, 3.61, 3.27 and 2.52. Three most statistically significant SNPs were rs2069705, located in the promoter region of the interferon gamma gene (INF-gamma); rs2243248, in the promoter of IL-4 (rs2243248); and rs1800925, in the promoter of the IL-13 gene. Increased serum cytokine levels at diagnosis are indicative for immunological alterations and possibly related to genetic susceptibility markers as well. These findings might guide us to understand the presence of SNPs in cytokine genes and serum concentrations among breast cancer patients and potentially in other cancers.

Transforming growth factorβ1 L10P variant plays an active role on the breast cancer susceptibility in Caucasian: evidence from 10,392 cases and 11,697 controls

In view of the essential role of transforming growth factorβ1 (TGFB1) on both inhibiting the development of early benign breast tumors as well as promoting tumor invasion, the association of TGFB1 L10P polymorphism and breast cancer risk has been widely reported, but results of previous studies were somewhat contradictory and underpowered. To overcome the limitations of individual study and to understand the real situation, we conducted a systematic review and meta-analysis towards the association between TGFB1 L10P polymorphism and breast cancer. Through retrieving MEDLINE, PubMed, Embase, and Web of Science, a total of 16 studies with 10,392 cases and 11,697 controls were identified. The results showed that significant association was found in the recessive genetic model for Caucasian (OR = 1.152, 95% CI = 1.020-1.301). However, we did not find any associations in additive genetic model (PP vs. LL for total: OR = 1.026, 95% CI = 0.940-1.121), allele contrast (L vs. P for total: OR = 1.004, 95% CI = 0.966-1.044), and dominant genetic model (PP + LP vs. LL for total: OR = 1.001, 95% CI = 0.946-1.061). Conclusively, this meta-analysis strongly suggests that TGFB1 L10P polymorphism may play a low penetrance role in breast cancer susceptibility in Caucasian. Large well-designed epidemiological studies will be necessary to validate the risk identified in the current meta-analysis.

Lack of significant association between TGF-β1-590C/T polymorphism and breast cancer risk: a meta-analysis

Transforming growth factor β1 (TGF-β1) is a cytokine that plays an important role in the control of cell proliferation and differentiation in breast cancer. The -509C/T polymorphism in the TGF-β1 gene has been implicated in breast cancer risk. However, studies on the association between this polymorphism and breast cancer risk have produced conflicting results. To derive a more precise estimation of the relationship, a meta-analysis of the -509C/T polymorphism (5,825 cases and 7,953 controls) from seven published case-control studies was performed. Our analysis suggests that -509C/T has no association with breast cancer risk when using either dominant [odds ratio (OR) = 1.01, 95% confidence intervals (CI): 0.82-1.24], or recessive models (OR = 0.91, 95% CI: 0.66-1.27), or other genetic models to analyze the data. In ethnic subgroups analysis, -509C/T also did not appear to be a risk factor for breast cancer. However, larger scale primary studies are still required to further evaluate the interaction of TGF-β1 -509C/T polymorphism and breast cancer risk in specific populations.

Transforming growth factor-beta1 polymorphisms and breast cancer risk: a meta-analysis based on 27 case-control studies

The association between transforming growth factor-beta1 (TGF-beta1) gene polymorphisms and breast cancer risk has been widely reported, but results were somewhat controversial and underpowered. To derive a more precise estimation of the relationship between TGF-beta1 polymorphisms and breast cancer risk, we conducted a meta-analysis of all available case-control studies relating the T869C and/or C-509T polymorphisms of the TGF-beta1 gene to the risk of developing breast cancer. Eligible articles were identified by search of databases including MEDLINE, PubMed, Web of Science, EMBASE, and Chinese Biomedical Literature database (CBM) for the period up to March 2010. Finally, a total of 17 articles involving 27 case-control studies were identified, 25 with 20,022 cases and 24,423 controls for T869C polymorphism and eight with 10,633 cases and 13,648 controls for C-509T polymorphism. The pooled ORs were performed for the allele contrasts, additive genetic model, dominant genetic model and recessive genetic model, respectively. Subgroup analysis was also performed by ethnicity for T869C polymorphism. With respect to T869C polymorphism, no association was found in overall analysis (C vs. T: OR = 1.033, 95% CI = 0.996-1.072). In the subgroup analysis by ethnicity, significantly increased risk was found in Caucasian population (C vs. T: OR = 1.051, 95% CI = 1.018-1.085; CC vs. TT + TC: OR = 1.083, 95% CI = 1.019-1.151), but not in Asian population (C vs. T: OR = 1.054, 95% CI = 0.983-1.130). With respect to C-509T polymorphism, no significant association with breast cancer risk was demonstrated in overall analysis (T vs. C: OR = 0.986, 95% CI = 0.936-1.039). It can be concluded that potentially functional TGF-Beta1 T869C polymorphism may play a low penetrance role in breast cancer susceptibility in an ethnicity-specific manner.

An empirical comparison of meta-analyses of published gene-disease associations versus consortium analyses

PURPOSE

Consortia of investigators currently compile sufficiently large sample sizes to investigate the effects of low-risk susceptibility genetic variants. It is not clear how the results obtained by consortia compare with those derived from meta-analyses of published studies.

METHODS

We performed meta-analyses of published data for 16 genetic polymorphisms investigated by the Breast Cancer Association Consortium, and compared sample sizes, heterogeneity, and effect sizes. PubMed, Web of Science, and Human Genome Epidemiology Network databases were searched for breast cancer case-control association studies.

RESULTS

We found that meta-analyses of published data and consortium analyses were based on substantially different data. Published data by non-consortium teams amounted on average to 26.9% of all available data (range 3.0 -50.0%). Both approaches showed statistically significant decreased breast cancer risks for CASP8 D302H. The meta-analyses of published data demonstrated statistically significant results for five other genes and the consortium analyses for two other genes, but the strength of this evidence, evaluated on the basis of the Venice criteria, was not strong.

CONCLUSIONS

Because both approaches identified the same gene out of 16 candidates, the methods can be complimentary. The expense and complexity of consortium-based studies should be considered vis-à-vis the potential methodological limitations of synthesis of published studies.

Genetic polymorphisms in the transforming growth factor-beta signaling pathways and breast cancer risk and survival

The transforming growth factor (TGF)-beta signaling pathway plays a critical role in breast cancer development and progression. Limited data from human studies, however, are currently available to link biomarkers in this pathway directly to the risk and survival of breast cancer. Most of the previous epidemiologic studies have focused on evaluating polymorphisms in the TGFB1 gene (T+29C, rs1982073) and the TGFBR1 gene (9A/6A), and the results have been inconsistent. The present review summarizes epidemiologic evidence regarding the association of genetic polymorphisms in the TGF beta pathway genes with breast cancer risk and survival and provides rationale and new approaches to continuing the research in this area.

Cytokine gene polymorphisms, cancer susceptibility, and prognosis

IL-10 is a multifunctional cytokine with both immunosuppressive and antiangiogenic functions and may have both tumor-promoting and -inhibiting properties. A large number of polymorphisms (primarily single-nucleotide polymorphisms) have been identified in the IL10 gene promoter. Convincing evidence that certain of these polymorphisms are associated with differential expression of IL-10 in vitro and in some cases in vivo was obtained, and a number of studies investigated associations between IL10 polymorphisms and cancer susceptibility and prognosis. The results from 22 studies in 13 different malignancies are reviewed. In 17 of these studies, positive associations between IL10 genotype or haplotype and disease susceptibility, progression, or both were reported. In some of these cancers genotypes associated with low IL-10 expression were a risk factor for disease or disease progression, whereas in others genotypes associated with high IL-10 expression were a risk factor. Published findings in breast cancer are as yet conflicting. Most but not all of the studies reviewed are based on small sample sizes and a limited number of IL10 polymorphisms. However, the preliminary data indicate that larger studies are required in a number of cancers to confirm initial results, extend studies to include more detailed genotype and haplotype analysis, and combine genotype and gene expression studies in the same subjects. Such studies will contribute significantly to our understanding of the biological role of IL-10 in cancer development.

Transforming-growth factor beta1 Leu10Pro polymorphism and breast cancer morbidity

TGF-beta1 has a dual role in carcinogenesis. In this gene, a leucine to proline substitution in codon 10 leads to higher circulating levels of TGF-beta1. This variant has been studied in relationship to the risk for breast cancer yielding contradicting results. We aim to unravel the relationship of this polymorphism and the risk of breast cancer. Women participating in the Rotterdam Study including 143 patients with incident breast cancer were genotyped for this polymorphism. We carried out a logistic regression and a survival analysis using age as the time variable. The logistic regression analysis showed an increased risk of breast cancer for Proline carriers (OR=1.4; 95% confidence interval (CI)=1.1-2.0) versus non-carriers. The survival analysis showed that carriers of the same allele had an increased risk of breast cancer (HR=1.4, 95% CI=1.1-2.0) against non-carriers. Our data suggest that the TGF-beta1 Leu10Pro polymorphism might play a role in breast cancer risk.

Interleukin-10 polymorphisms, cancer susceptibility and prognosis

Interleukin-10 (IL-10) is a multifunctional cytokine with both immunosuppressive and anti-angiogenic functions and may have both tumour-promoting and -inhibiting properties. A large number of polymorphisms (primarily single nucleotide polymorphisms (SNPs)) have been identified in the IL-10 gene promoter. Convincing evidence that certain of these polymorphisms are associated with differential expression of IL-10 in vitro and in some cases in vivo has been obtained and a number of studies have investigated associations between IL-10 polymorphisms and cancer susceptibility/prognosis. The results from 22 studies in 13 different malignancies are reviewed. In 17 of these studies, positive associations between IL-10 genotype or haplotype and disease susceptibility and/or progression were reported. In some of these cancers genotypes associated with low IL-10 expression were a risk factor for disease or disease progression, while in others genotypes associated with high IL-10 expression were a risk factor. Published findings in breast cancer are as yet conflicting. Most, but not all of the studies reviewed are based on small sample sizes and a limited number of IL-10 polymorphisms. However, the preliminary data obtained thus far indicate that larger studies are required in a number of cancers, in order to confirm initial results, extend studies to include more detailed genotype/haplotype analysis and combine genotype and gene expression studies in the same subjects. Such studies will contribute significantly to our understanding of the biological role of IL-10 in cancer development.

A molecular mechanism for the differential regulation of TGF-beta1 expression due to the common SNP -509C-T (c. -1347C > T)

Transforming growth factor beta1 (TGF-beta1) levels influence many cellular, immunologic and pathologic processes. Activator protein 1 (AP1) and hypoxia are key regulators of TGF-beta1 expression levels. The common TGFB1 promoter SNP c.-1347C > T (-509C-T, rs1800469) has been linked to a nearly twofold difference in plasma levels among individuals and with risk, progression, and outcome of numerous diseases. We demonstrate exclusive in vitro and in vivo recruitment of AP1 containing JunD to -1347C. This study also is the first to demonstrate hypoxia inducible factor 1 (HIF-1) binding to the TGFB1 promoter. HIF-1 was found to associate with both -1347C and -1347T and compete with AP1 for binding to -1347C. Reporter constructs demonstrate that expression differences between -1347C and -1347T are due to selective AP1 recruitment to the TGFB1 promoter. As AP1 is known to down-regulate transcription of other genes, we suggest that the molecular mechanism for the difference in TGF-beta1 plasma levels linked to -1347 is due to transcriptional suppression by AP1 binding to -1347C. These data should aid in our understanding of the association of the -1347 SNP with the pathogenesis of certain TGF-beta1-related diseases.

Allelic diversity in the TGFB1 regulatory region: characterization of novel functional single nucleotide polymorphisms

Altered TGF-beta1 expression due to polymorphisms affects a wide variety of normal cellular and disease processes such as T cell activation and proliferation, tumor progression, and asthma. In this study, a comprehensive examination of function and diversity was undertaken for the TGFB1 promoter region and exon 1 (-2,665 to +423). The known TGF-beta1 promoter was extended to encompass 463 bases by the identification of a strong enhancer activity for a distal segment (-2,665 to -2,204). Ten novel polymorphisms and 14 novel alleles were identified. Most single nucleotide polymorphisms (SNPs) appear to be randomly associated except c.-768_-769insC and c.+74G > C and a set of five novel polymorphisms present in a single allele in persons of African descent. The TGFB1 alleles clustered into three phylogenetic groups based on the common functional SNPs c.-1347C > T (commonly known as -509C-T) and c.+29T > C (commonly known as +869T-C) suggesting three phenotypic groups. Two SNPs unique to African-Americans affect the TGFB1 regulatory region. The c.-1287G > A SNP in the promoter alters the binding affinity of two unidentified transcription factor complexes which translates into a significant difference in reporter gene expression and the c.-387C > T SNP in the 5' UTR alters the binding of Stimulating protein 1 and 3. Thus, TGFB1 possesses a highly polymorphic, extensive regulatory region that likely impacts the pathogenesis of numerous TGF-beta1 related diseases.