TGFBR1*6A/9A polymorphism and cancer risk: a meta-analysis of 13,662 cases and 14,147 controls

Transforming growth factor-β in tumour development

Transforming growth factor-β (TGFβ) is a ubiquitous cytokine essential for embryonic development and postnatal tissue homeostasis. TGFβ signalling regulates several biological processes including cell growth, proliferation, apoptosis, immune function, and tissue repair following injury. Aberrant TGFβ signalling has been implicated in tumour progression and metastasis. Tumour cells, in conjunction with their microenvironment, may augment tumourigenesis using TGFβ to induce epithelial-mesenchymal transition, angiogenesis, lymphangiogenesis, immune suppression, and autophagy. Therapies that target TGFβ synthesis, TGFβ-TGFβ receptor complexes or TGFβ receptor kinase activity have proven successful in tissue culture and in animal models, yet, due to limited understanding of TGFβ biology, the outcomes of clinical trials are poor. Here, we review TGFβ signalling pathways, the biology of TGFβ during tumourigenesis, and how protein quality control pathways contribute to the tumour-promoting outcomes of TGFβ signalling.

TGFBR1*6A as a modifier of breast cancer risk and progression: advances and future prospects

There is growing evidence that germline mutations in certain genes influence cancer susceptibility, tumor evolution, as well as clinical outcomes. Identification of a disease-causing genetic variant enables testing and diagnosis of at-risk individuals. For breast cancer, several genes such as BRCA1, BRCA2, PALB2, ATM, and CHEK2 act as high- to moderate-penetrance cancer susceptibility genes. Genotyping of these genes informs genetic risk assessment and counseling, as well as treatment and management decisions in the case of high-penetrance genes. TGFBR1*6A (rs11466445) is a common variant of the TGF-β receptor type I (TGFBR1) that has a global minor allelic frequency (MAF) of 0.051 according to the 1000 Genomes Project Consortium. It is emerging as a high frequency, low penetrance tumor susceptibility allele associated with increased cancer risk among several cancer types. The TGFBR1*6A allele has been associated with increased breast cancer risk in women, OR 1.15 (95% CI 1.01–1.31). Functionally, TGFBR1*6A promotes breast cancer cell proliferation, migration, and invasion through the regulation of the ERK pathway and Rho-GTP activation. This review discusses current findings on the genetic, functional, and mechanistic associations between TGFBR1*6A and breast cancer risk and proposes future directions as it relates to genetic association studies and mechanisms of action for tumor growth, metastasis, and immune suppression.

The relation between anti-TGBFR1 immunohistochemical reaction and low Ki67, small tumor size and high estrogen receptor expression in invasive breast cancer

Most breast cancers are derived from the luminal epithelium, which composes the inside of the breast ductal structure. Ductal carcinoma in situ (DCIS) leads to invasive ductal carcinoma, but noncancerous intraductal proliferative lesions are also a risk factor for ductal carcinoma. The transforming growth factor beta (TGFB) signaling pathway behaves as a tumor suppressor in the early stage of cancer, and conversely as a tumor growth factor in invasive stages in several cancers. In this study, we performed immunohistochemistry with an antibody that detects the cytoplasmic region of TGFB receptor 1 (TGFBR1) and elucidated TGFBR1 protein expression in luminal epithelial cells of noncancerous breast ducts and in several cases of DCIS and invasive carcinoma. TGFBR1 expression was higher in noncancerous breast tissue than in cancerous tissue, and a difference in expression was also seen among histological subtypes. Comparing the expression level of TGFBR1 in cancer cells and clinico-pathological parameters, cases expressing low TGFBR1 tended to show low estrogen receptor expression, large tumor size (≥10 mm), and a high Ki67 labeling index. These data suggested that TGFBR1 protein expression may be related to the suppression of breast cancer cell growth.

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.

Immunomodulatory Effects of TGF-β Family Signaling within Intestinal Epithelial Cells and Carcinomas

TGF-β superfamily signaling is responsible for many critical cellular functions including control of cell growth, cell proliferation, cell differentiation, and apoptosis. TGF-β appears to be critical in gastrulation, embryonic development, and morphogenesis, and it retains pleiotropic roles in many adult tissues and cell types in a highly context-dependent manner. While TGF-β signaling within leukocytes is known to have an immunosuppressive role, its immunomodulatory effects within epithelial cells and epithelial cancers is less well understood. Recent data has emerged that suggests TGF-β pathway signaling within epithelial cells may directly modulate pro-inflammatory chemokine/cytokine production and resultant leukocyte recruitment. This immunomodulation by epithelial TGF-β pathway signaling may directly impact tumorigenesis and tumor progression through modulation of the epithelial microenvironment, although causal pathways responsible for such an observation remain incompletely investigated. This review presents the published literature as it relates to the immunomodulatory effects of TGF-β family signaling within intestinal epithelial cells and carcinomas.

Associations of TGFBR1 and TGFBR2 gene polymorphisms with the risk of hypospadias: a case-control study in a Chinese population

This case-control study investigated the association of transforming growth factor-β (TGF-β) receptor type I and II (TGFBR1 and TGFBR2) gene polymorphisms with the risk of hypospadias in a Chinese population. One hundred and sixty two patients suffering from hypospadias were enrolled as case group and 165 children who underwent circumcision were recruited as control group. Single nucleotide polymorphisms (SNPs) in TGFBR1 and TGFBR2 genes were selected on the basis of genetic data obtained from HapMap. PCR-restriction fragment length polymorphism (PCR-RFLP) was performed to identify TGFBR1 and TGFBR2 gene polymorphisms and analyze genotype distribution and allele frequency. Logistic regression analysis was conducted to estimate the risk factors for hypospadias. No significant difference was found concerning the genotype and allele frequencies of TGFBR1 rs4743325 polymorphism between the case and control groups. However, genotype and allele frequencies of TGFBR2 rs6785358 in the case group were significantly different in contrast with those in the control group. Patients carrying the G allele of TGFBR2 rs6785358 polymorphism exhibited a higher risk of hypospadias compared with the patients carrying the A allele (P<0.05). The TGFBR2 rs6785358 genotype was found to be significantly related to abnormal pregnancy and preterm birth (both P<0.05). The frequency of TGFBR2 rs6785358 GG genotype exhibited significant differences amongst patients suffering from four different pathological types of hypospadias. Logistic regression analysis revealed that preterm birth, abnormal pregnancy, and TGFBR2 rs6785358 were the independent risk factors for hypospadias. Our study provides evidence that TGFBR2 rs6785358 polymorphism might be associated with the risk of hypospadias.

Transforming growth factor-β signaling pathway-associated genes SMAD2 and TGFBR2 are implicated in metabolic syndrome in a Taiwanese population

The transforming growth factor-β (TGF-β) signaling pathway and its relevant genes have been correlated with an increased risk of developing various hallmarks of metabolic syndrome (MetS). In this study, we assessed whether the TGF-β signaling pathway-associated genes of SMAD family member 2 (SMAD2), SMAD3, SMAD4, transforming growth factor beta 1 (TGFB1), TGFB2, TGFB3, transforming growth factor beta receptor 1 (TGFBR1), and TGFBR2 are associated with MetS and its individual components independently, through complex interactions, or both in a Taiwanese population. A total of 3,000 Taiwanese subjects from the Taiwan Biobank were assessed. Metabolic traits such as waist circumference, triglyceride, high-density lipoprotein cholesterol, systolic and diastolic blood pressure, and fasting glucose were measured. Our results showed a significant association of MetS with the two single nucleotide polymorphisms (SNPs) of SMAD2 rs11082639 and TGFBR2 rs3773651. The association of MetS with these SNPs remained significant after performing Bonferroni correction. Moreover, we identified the effect of SMAD2 rs11082639 on high waist circumference. We also found that an interaction between the SMAD2 rs11082639 and TGFBR2 rs3773651 SNPs influenced MetS. Our findings indicated that the TGF-β signaling pathway-associated genes of SMAD2 and TGFBR2 may contribute to the risk of MetS independently and through gene-gene interactions.

Transforming Growth Factor β Superfamily Signaling in Development of Colorectal Cancer

Transforming growth factor (TGF)-β cytokines signal via a complex network of pathways to regulate proliferation, differentiation, adhesion, migration, and other functions in many cell types. A high percentage of colorectal tumors contain mutations that disrupt TGF-β family member signaling. We review how TGF-β family member signaling is altered during development of colorectal cancer, models of study, interaction of pathways, and potential therapeutic strategies.

Meta-analysis of transforming growth factor β receptor I 6A/9A gene polymorphism and breast cancer risk: the picture remains murky

Breast cancer is currently the second most common cancer worldwide and the most frequent malignant tumor among women. However, the exact contribution of various allelic alterations remains unclear. This meta-analysis was conducted to evaluate the association of the transforming growth factor β receptor I 6A/9A (TβR-I 6A/9A) gene polymorphism with breast cancer risk. Relevant studies were identified from PubMed and Cochrane Library on 1 October 2013, and eligible reports were recruited and synthesized. Eleven reports that included a total of 12 studies were recruited into this meta-analysis for the association of the TβR-I 6A/9A gene polymorphism and breast cancer risk. The results indicated that overall the TβR-I 6A allele was associated with breast cancer risk (OR = 1.33, 95% CI: 1.02-1.73, p = 0.04). However, the TβR-I 6A/6A and 9A/9A genotypes were not associated with an increased risk of developing breast cancer (6A/6A: OR = 1.71, 95% CI: 0.95-3.08, p = 0.07; 9A/9A: OR = 0.82, 95% CI: 0.66-1.02, p = 0.08). In the Caucasian population, no such association could be established. In conclusion, the TβR-I 6A allele might represent a risk factor for breast cancer risk, but significantly larger data sets from a larger number of studies, including studies that allow ethnicity, subgroup analysis and environmental impact evaluation, are required to maximize statistical significance and meta-analysis robustness.

Genetic Polymorphisms of TGFB1, TGFBR1, SNAI1 and TWIST1 Are Associated with Endometrial Cancer Susceptibility in Chinese Han Women

Endometrial cancer (EC) is a complex disease involving multiple gene-gene and gene-environment interactions. TGF-β signaling plays pivotal roles in EC development. This study aimed to investigate whether the genetic polymorphisms of TGF-β signaling related genes TGFB1, TGFBR1, SNAI1 and TWIST1 contribute to EC susceptibility. Using the TaqMan Genotyping Assay, 19 tagging-SNPs of these four genes were genotyped in 516 EC cases and 707 controls among Chinese Han women. Logistic regression (LR) showed that the genetic variants of TGFB1 rs1800469, TGFBR1 rs6478974 and rs10733710, TWIST1 rs4721745 were associated with decreased EC risk, and these four loci showed a dose-dependent effect (Ptrend < 0.0001). Classification and regression tree (CART) demonstrated that women carrying both the genotypes of TGFBR1 rs6478974 TT and rs10512263 TC/CC had the highest risk of EC (aOR = 7.86, 95% CI = 3.42-18.07, P<0.0001). Multifactor dimensionality reduction (MDR) revealed that TGFB1 rs1800469 plus TGFBR1 rs6478974 was the best interactional model to detect EC risk. LR, CART and MDR all revealed that TGFBR1 rs6478974 was the most important protective locus for EC. In haplotype association study, TGFBR1 haplotype CACGA carrier showed the lowest EC risk among women with longer menarche-first full term pregnancy intervals (˃11 years) and BMI˂24 (aOR = 0.39, 95% CI = 0.17-0.90, P = 0.0275). These results suggest that polymorphisms in TGFB1, TGFBR1, SNAI1 and TWIST1 may modulate EC susceptibility, both separately and corporately.

TGFBR1*6A polymorphism in sporadic and familial colorectal Carcinoma: a case-control study and systematic literature review

BACKGROUND

The role of genetic factors in colorectal cancer pathogenesis is widely accepted. Polymorphisms are actually thought to play a role in the unexplained colorectal cancer (CRC) susceptibility. There is conflicting data regarding the role of the transforming growth factor beta receptor 1 polymorphism 6A (TGFBR1*6A) in the increased incidence of CRC.

PURPOSE

Our aim is to test the association between this polymorphism and sporadic/familial CRC in the Lebanese population paying attention to lead time bias in the control group. This is a case-control study conducted in two Lebanese hospital centers.

MATERIALS AND METHODS

Cases were diagnosed with CRC during the period of 1 year prior to the study. Controls were healthy subjects aged >50 years with a history of normal colonoscopy during the period of 5 years prior to the beginning of the study. A total of 96 cases (57 sporadic/39 familial) and 97 controls were genotyped. The odds ratios for 6A carrier status was statistically significant for sporadic CRC, odds ratio (OR) = 2.314 (95 % confidence interval (CI) 1.030-5.195) but not for familial CRC.

RESULTS

No association was found between 6A carrier status and mean age at diagnosis of CRC. This is the first article in the literature to evaluate the association between 6A polymorphism and total, sporadic, and familial CRC in a single study with reduction of bias in the control group. Results are in conjunction with other studies and meta-analysis.

Genome-wide association study identifies new susceptibility loci for epithelial ovarian cancer in Han Chinese women

Ovarian cancer is the leading cause of death from gynaecological malignancies worldwide. Here we perform a three-stage genome-wide association study (GWAS) in Han Chinese women to identify risk genetic variants for epithelial ovarian cancer (EOC). We scan 900,015 single-nucleotide polymorphisms (SNPs) in 1,057 EOC cases and 1,191 controls in stage I, and replicate 41 SNPs (P(meta)<10(-4)) in 960 EOC cases and 1,799 controls (stage II), and an additional 492 EOC cases and 1,004 controls (stage III). Finally, we identify two EOC susceptibility loci at 9q22.33 (rs1413299 in COL15A1, P(meta) = 1.88 × 10(-8)) and 10p11.21 (rs1192691 near ANKRD30A, P(meta) = 2.62 × 10(-8)), and two consistently replicated loci at 12q14.2 (rs11175194 in SRGAP1, P(meta) = 1.14 × 10(-7)) and 9q34.2 (rs633862 near ABO and SURF6, P(meta) = 8.57 × 10(-7)) (P<0.05 in all three stages). These results may advance our understanding of genetic susceptibility to EOC.

Genome-wide association and sequencing studies on colorectal cancer

Colorectal cancer is a leading cause of morbidity and mortality worldwide. Understanding its genetic mechanisms is key to improving risk prediction, prognostication and treatment. Results from genome-wide association studies have engendered a growing list of colorectal cancer susceptibility genes whereas the application of genome-wide mutational analysis has enabled the depiction of mutational landscape of colorectal cancer at high resolution. The development of novel technologies, such as metagenomic and single-cell sequencing, is expected to have positive impact on future genetic studies. However, challenges remain to address the changing epidemiology of colorectal cancer, issues on genetic testing, and clinical utilization of genomic data.

Associations between genetic variants in the TGF-β signaling pathway and breast cancer risk among Hispanic and non-Hispanic white women

The TGF-β signaling pathway has a significant role in breast cancer initiation and promotion by regulating various cellular processes. We evaluated whether genetic variation in eight genes (TGF-β1, TGF-β2, TGF-βR1, TGF-βR2, TGF-βR3, RUNX1, RUNX2, and RUNX3) is associated with breast cancer risk in women from the Breast Cancer Health Disparities Study. A total of 3,524 cases (1,431 non-Hispanic whites (NHW); 2,093 Hispanics/Native Americans(NA)) and 4,209 population-based controls (1,599 NHWs; 2,610 Hispanics/NAs) were included in analyses. Genotypes for 47 single nucleotide polymorphisms (SNPs) were determined. Additionally, 104 ancestral informative markers estimated proportion of NA ancestry. Associations with breast cancer risk overall, by menopausal status, NA ancestry, and estrogen receptor (ER)/progesterone receptor tumor phenotype were evaluated. After adjustment for multiple comparisons, two SNPs were significantly associated with breast cancer risk: RUNX3 (rs906296 ORCG/GG = 1.15 95 % CI 1.04-1.26) and TGF-β1 (rs4803455 ORCA/AA = 0.89 95 % CI 0.81-0.98). RUNX3 (rs906296) and TGF-βR2 (rs3773644) were associated with risk in pre-menopausal women (p adj = 0.002 and 0.02, respectively) and in those with intermediate to high NA ancestry (p adj = 0.04 and 0.01, respectively). Self-reported race was strongly correlated with NA ancestry (r = 0.86). There was a significant interaction between NA ancestry and RUNX1 (rs7279383, p adj = 0.04). Four RUNX SNPs were associated with increased risk of ER- tumors. Results provide evidence that genetic variation in TGF-β and RUNX genes are associated with breast cancer risk. This is the first report of significant associations between genetic variants in TGF-β and RUNX genes and breast cancer risk among women of NA ancestry.

Int7G24A polymorphism (rs334354) and cancer risk

INTRODUCTION

The transforming growth factor β (TGF-β) signaling system plays an important role in carcinogenesis. Alteration of TGF-β receptors is a potential mechanism in the development and progression of human cancers. Several studies have investigated the association between TGFBR1 gene Int7G24A and cancer risk, but the results are still inconclusive, so a meta-analysis is needed to verify the association.

MATERIAL AND METHODS

We carried out a literature search using the PubMed database (up to January 2012) to identify all papers that investigated the association between the Int7G24A polymorphism (rs334354) and cancer risk. The inclusion criteria were: (1) evaluation of the Int7G24A polymorphism and cancer risk, (2) case-control studies, (3) sufficient published data about genotype frequency. Also the strength of the association between Int7G24A polymorphism and cancer was measured by odds ratio (OR), which was calculated according to the method of Woolf. A χ(2)-based Q statistic test was performed to assess the between-study heterogeneity.

RESULTS

There are 10 studies including 2398 cases and 3465 controls in the research. Our results indicate that the TGFBR1 gene Int7G24A polymorphism is associated with cancer risk (A vs. G: OR = 1.35, 95% CI = 1.10-1.66, A/A+G/A vs. G/G: OR = 1.34, 95% CI = 1.05-1.72).

CONCLUSIONS

This meta-analysis suggests that the TGFBR1 gene Int7G24A polymorphism might be associated with an increased risk of cancer.

TGFBR1 tagging SNPs and gastric cancer susceptibility: a two-stage case-control study in Chinese population

The transforming growth factor (TGF)-β is a potent growth inhibitor primarily responsible for cell growth, differentiation, and apoptosis, and frequently perturbed during development of tumors, including gastric cancer. TGF-β receptor type I (TGFβR1) may be a modifier of cancer risk by constitutively decreasing the TGF-β inhibitory signals during early tumorigenesis and increasing the TGF-β signals in tumor progression. In this study, we hypothesized that genetic variants of TGFBR1 may influence the risk of gastric cancer. We conducted a two-stage case-control study of gastric cancer, including 650 cases and 683 controls in the first stage and 484 cases and 348 controls in the second stage, and genotyped five tagging single nucleotide polymorphisms (SNPs) to represent common variants in the whole TGFBR1 gene. In the first stage, two SNPs rs6478974 and rs10512263 were found to be potentially associated with risk of gastric cancer (P = 3.35 × 10(-3) for rs6478974 AT vs. TT and P = 0.033 for rs10512263 CT vs. TT), which were further confirmed in the second stage with similar effects (P = 0.144 and 0.049, respectively). After combining the two stages, we found that these two SNPs were associated with a significantly increased risk of gastric cancer in dominant models [adjusted odds ratio (OR) = 1.36, 95% confidence interval (CI): 1.14-1.63 for rs6478974 AT/AA vs. TT; adjusted OR = 1.26, 95% CI: 1.05-1.50 for rs10512263 CT/CC vs. TT] or additive model (adjusted OR = 1.23, 95% CI: 1.08-1.40 for rs6478974). These findings indicate that TGFBR1 polymorphisms may be implicated with the development of gastric cancer in Han-Chinese population.

Association between TGFBR1 polymorphisms and cancer risk: a meta-analysis of 35 case-control studies

Background

Numerous epidemiological studies have evaluated the association between TGFBR1 polymorphisms and the risk of cancer, however, the results remain inconclusive. To derive a more precise estimation of the relation, we conducted a comprehensive meta-analysis of all available case-control studies relating the TGFBR1*6A and IVS7+24G>A polymorphisms of the TGFBR1 gene to the risk of cancer.

Methods

Eligible studies were identified by search of electronic databases. Overall and subgroup analyses were performed. Odds ratio (OR) and 95% confidence interval (CI) were applied to assess the associations between TGFBR1*6A and IVS7+24G>A polymorphisms and cancer risk.

Results

A total of 35 studies were identified, 32 with 19,767 cases and 18,516 controls for TGFBR1*6A polymorphism and 12 with 4,195 cases and 4,383 controls for IVS7+24G>A polymorphism. For TGFBR1*6A, significantly elevated cancer risk was found in all genetic models (dominant OR = 1.11, 95% CI = 1.04∼1.18; recessive: OR = 1.36, 95% CI = 1.11∼1.66; additive: OR = 1.13, 95% CI = 1.05∼1.20). In subgroup analysis based on cancer type, increased cancer risk was found in ovarian and breast cancer. For IVS7+24G>A, significant correlation with overall cancer risk (dominant: OR = 1.39, 95% CI = 1.15∼1.67; recessive: OR = 2.23, 95% CI = 1.26∼3.92; additive: OR = 1.43, 95% CI = 1.14∼1.80) was found, especially in Asian population. In the subgroup analysis stratified by cancer type, significant association was found in breast and colorectal cancer.

Conclusions

Our investigations demonstrate that TGFBR1*6A and IVS7+24G>A polymorphisms of TGFBR1 are associated with the susceptibility of cancer, and further functional research should be performed to explain the inconsistent results in different ethnicities and cancer types.

TGFBR1 intralocus epistatic interaction as a risk factor for colorectal cancer

In colorectal cancer (CRC), an inherited susceptibility risk affects about 35% of patients, whereas high-penetrance germline mutations account for <6% of cases. A considerable proportion of sporadic tumors could be explained by the coinheritance of multiple low-penetrance variants, some of which are common. We assessed the susceptibility to CRC conferred by genetic variants at the TGFBR1 locus. We analyzed 14 polymorphisms and the allele-specific expression (ASE) of TGFBR1 in 1025 individuals from the Spanish population. A case-control study was undertaken with 504 controls and 521 patients with sporadic CRC. Fourteen polymorphisms located at the TGFBR1 locus were genotyped with the iPLEX Gold (MassARRAY-Sequenom) technology. Descriptive analyses of the polymorphisms and haplotypes and association studies were performed with the SNPator workpackage. No relevant associations were detected between individual polymorphisms or haplotypes and the risk of CRC. The TGFBR1*9A/6A polymorphism was used for the ASE analysis. Heterozygous individuals were analyzed for ASE by fragment analysis using cDNA from normal tissue. The relative level of allelic expression was extrapolated from a standard curve. The cutoff value was calculated with Youden's index. ASE was found in 25.4% of patients and 16.4% of controls. Considering both bimodal and continuous types of distribution, no significant differences between the ASE values of patients and controls were identified. Interestingly, a combined analysis of the polymorphisms and ASE for the association with CRC occurrence revealed that ASE-positive individuals carrying one of the most common haplotypes (H2: 20.7%) showed remarkable susceptibility to CRC (RR: 5.25; 95% CI: 2.547–5.250; p<0.001) with a synergy factor of 3.7. In our study, 54.1% of sporadic CRC cases were attributable to the coinheritance of the H2 haplotype and TGFBR1 ASE. These results support the hypothesis that the allelic architecture of cancer genes, rather than individual polymorphisms, more accurately defines the CRC risk.

Debate about TGFBR1 and the susceptibility to colorectal cancer

Recent years have witnessed enormous progress in our understanding of the genetic predisposition to colorectal cancer (CRC). Estimates suggest that all or most genetic susceptibility mechanisms proposed so far, ranging from high-penetrance genes to low-risk alleles, account for about 60% of the population-attributable fraction of CRC predisposition. In this context, there is increasing interest in the gene encoding the transforming growth factor β receptor 1 (TGFBR1); first when over a decade ago a common polymorphism in exon 1 (rs11466445, TGFBR1*6A/9A) was suggested to be a risk allele for CRC, then when linkage studies identified the chromosomal region where the gene is located as susceptibility locus for familial CRC, and more recently when the allele-specific expression (ASE) of the gene was proposed as a risk factor for CRC. Published data on the association of TGFBR1 with CRC, regarding polymorphisms and ASE and including sporadic and familial forms of the disease, are often contradictory. This review gives a general overview of the most relevant studies in order to clarify the role of TGFBR1 in the field of CRC genetic susceptibility.

The association of polymorphisms on TGFBR1 and colorectal cancer risk: a meta-analysis

Epidemiological studies found inconsistent results on the association of two variants on TGFBR1 (TGFBR1*6A and Int7G24A) with colorectal cancer (CRC) risk. The present study was aimed to evaluate the association of these two variants with CRC susceptibility via the meta-analysis methods. For variant TGFBR1*6A, nine reports including 6,765 CRC patients and 8,496 unrelated controls were identified. The heterozygotes *6A/*9A showed a significant increased risk of CRC with the pooled OR was 1.12 (95% CI = 1.02-1.23), and the pooled OR for the homozygotes *6A/*6A was 1.13 (95% CI = 0.80-1.58) compared to the homozygotes *9A/*9A. However, under the dominant effect model, the TGFBR1*6A carriers showed a significantly increased CRC risk (pooled OR = 1.12, 95% CI = 1.03-1.23, *6A/*6A and *6A/*9A vs. *9A/*9A). For variant Int7G24A, three case-control studies with 1,074 cases and 1,945 controls were found. Although no significant association was found for heterozygosity Int7G24A carriers with CRC risk (pooled OR = 0.97, 95% CI = 0.67-1.42), the homozygosity A/A carriers showed a significant elevated risk of CRC (pooled OR = 1.68, 95% CI = 1.14-2.47) compared to G/G homozygotes. Under the recessive effect model, homozygotes A/A showed a 71% increase of CRC risk compared to the A/G and G/G genotype carriers (pooled OR = 1.71, 95% CI = 1.17-2.51). These data strongly suggested that the two polymorphisms of TGFBR1 may confer low-penetrance susceptibility of CRC risk.

Transforming growth factor β signaling pathway associated gene polymorphisms may explain lower breast cancer risk in western Indian women

Transforming growth factor β1 (TGFB1) T29C and TGF β receptor type 1 (TGFBR1) 6A/9A polymorphisms have been implicated in the modulation of risk for breast cancer in Caucasian women. We analyzed these polymorphisms and combinations of their genotypes, in pre menopausal breast cancer patients (N = 182) and healthy women (N = 236) from western India as well as in breast cancer patients and healthy women from the Parsi community (N = 48 & 171, respectively). Western Indian women were characterized by a higher frequency of TGFB1*C allele of the TGF β T29C polymorphism (0.48 vs 0.44) and a significantly lower frequency of TGFBR1*6A allele of the TGFBR1 6A/9A polymorphism (0.02 vs 0.068, p<0.01) as compared to healthy Parsi women. A strong protective effect of TGFB1*29C allele was seen in younger western Indian women (<40 yrs; OR = 0.45, 95% CI 0.25-0.81). Compared to healthy women, the strikingly higher frequencies of low or intermediate TGF β signalers in patients suggested a strong influence of the combination of these genotypes on the risk for breast cancer in Parsi women (for intermediate signalers, OR = 4.47 95%CI 1.01-19.69). The frequency of low signalers in Parsi healthy women, while comparable to that reported in Europeans and Americans, was three times higher than that in healthy women from western India (10.6% vs 3.3%, p<0.01). These observations, in conjunction with the low incidence rate of breast cancer in Indian women compared to White women, raise a possibility that the higher frequency of TGFB1*29C allele and lower frequency of TGFBR1*6A allele may represent important genetic determinants that together contribute to a lower risk of breast cancer in western Indian women.

Association of polymorphisms in transforming growth factor-β receptors with susceptibility to gastric cardia adenocarcinoma

Both transforming growth factor-β receptor I (TGFBR1) and receptor II (TGFBR2) are serine/threonine kinases and play important roles in TGF-β/Smads signal pathway. The case-control study was performed to evaluate the possible association of Int7G24A and *6A polymorphisms of TGFBR1 and G-875A polymorphism of TGFBR2 with susceptibility to gastric cardia adenocarcinoma (GCA) in a population of North China. Polymerase-chain reaction (PCR)-restriction fragment length polymorphism (RFLP) and PCR methods were used respectively to detect the genotype of Int7G24A, *6A and G-875A in 468 GCA and 584 healthy controls. Immunohistochemistry method was used to determine the protein expression of TGFBR1 and TGFBR2. Family history of upper gastrointestinal cancer (UGIC) significantly increased the risk of developing GCA. There were no differences in the genotype distribution of TGFBR1 *6A polymorphism among cases and controls. However, A allele of Int7G24A significantly elevated the risk of developing GCA (adjusted OR = 1.34, 95% CI 1.03-1.87) and A allele of G-875A significantly decreased the risk of developing GCA (adjusted OR = 0.73, 95% CI 0.49-0.92). When stratified for TNM stage, A allele of Int7G24A and G-875A allele carriers had a 1.41-fold (95% CI 1.05-1.98) increased and a 0.70-fold (95% CI 0.47-0.92) decreased risk of stage III and IV gastric cardia adenocarcinoma. The protein expression of TGFBR1 and TGFBR2 in GCA was not correlated with genotypes of them. In conclusions, TGFBR1 Int7G24A and TGFBR2 G-875A polymorphisms may play important roles in the risk of GCA in North China.

TNF-308 gene polymorphism and tuberculosis susceptibility: a meta-analysis involving 18 studies

A number of studies have investigated the association between TNF-308 (rs1800629 G/A) polymorphisms and the susceptibility towards tuberculosis (TB) in different populations. However, many of these studies provided inconsistent results. In this study, a systematic review and meta-analysis of the published studies was performed to gain a clearer understanding of this association. The PubMed, Embase, Web of Science and CNKI databases were searched for case-control studies published up to Jan 2011, we used no lower date limit. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. A total of 18 publications from 2001 to 2010, involving 2584 TB cases and 3817 controls were included. Overall, for the A allele carriers (G/A + A/A) vs. homozygote GG, the pooled OR was 1.03 (95% CI = 0.89-1.19; P = 0.912 for heterogeneity). For the allele A vs. allele G, the pooled OR was 1.07 (95% CI = 0.93-1.22; P = 0.013 for heterogeneity). In the stratified analysis by ethnicity, among Asians significant risk was found for allele A vs. allele G (OR = 1.22, 95% CI = 1.02-1.47; P = 0.152 for heterogeneity), no significant risks were found among Caucasians. This meta-analysis indicated that the TNF-308 polymorphism was not associated with the risk of TB in the total population, however the significant risk for TNF-308 A allele was found among Asians not Caucasians.

TGFBR1 signaling and breast cancer

Over the past decade mutations discovered in genes such as BRCA1, BRCA2, TP53 and PTEN, have emerged as high-penetrance susceptibility genes and are clinically relevant for determination of breast cancer risk. Genetic counseling and subsequent screening for mutations and gene rearrangement has improved patient outcome through early detection and prophylactic interventions in patients with familial breast cancer syndromes. However, these high-penetrance genes only account for a small fraction of the hereditary linked breast cancers. It is currently believed that low-penetrance susceptibility alleles and/or environmental factors may play an important role in the remaining cases. TGFBR1*6A (*6A) is a common hypomorphic variant of the type I TGF-β receptor gene (TGFBR1) that has been associated with risk for several forms of cancer, in particular breast cancer. Several epidemiological studies have suggested that patients who carry the *6A allele have an increased risk of breast cancer. Furthermore, functional analysis suggests that this mutation alters TGF-β signaling and promotes tumorigenesis. Although a decade of research has provided basic information in regards to the prevalence of this mutation in several cancer types and populations the molecular underpinning of its functional effects are poorly understood. A better understanding of the molecular mechanism of TGFBR1 signaling in breast cancer may have an impact on breast cancer risk assessment and breast cancer prevention.

TGF-β signaling pathway and breast cancer susceptibility

BACKGROUND

TGF-β acts as a suppressor of primary tumor initiation but has been implicated as a promoter of the later malignant stages. Here associations with risk of invasive breast cancer are assessed for single-nucleotide polymorphisms (SNP) tagging 17 genes in the canonical TGF-β ALK5/SMADs 2&3 and ALK1/SMADs 1&5 signaling pathways: LTBP1, LTBP2, LTBP4, TGFB1, TGFB2, TGFB3, TGFBR1(ALK5), ALK1, TGFBR2, Endoglin, SMAD1, SMAD2, SMAD3, SMAD4, SMAD5, SMAD6, and SMAD7 [Approved Human Gene Nomenclature Committee gene names: ACVRL1 (for ALK1) and ENG (for Endoglin)].

METHODS

Three-hundred-fifty-four tag SNPs (minor allele frequency > 0.05) were selected for genotyping in a staged study design using 6,703 cases and 6,840 controls from the Studies of Epidemiology and Risk Factors in Cancer Heredity (SEARCH) study. Significant associations were meta-analyzed with data from the NCI Polish Breast Cancer Study (PBCS; 1,966 cases and 2,347 controls) and published data from the Breast Cancer Association Consortium (BCAC).

RESULTS

Associations of three SNPs, tagging TGFB1 (rs1982073), TGFBR1 (rs10512263), and TGFBR2 (rs4522809), were detected in SEARCH; however, associations became weaker in meta-analyses including data from PBCS and BCAC. Tumor subtype analyses indicated that the TGFB1 rs1982073 association may be confined to increased risk of developing progesterone receptor negative (PR(-)) tumors [1.18 (95% CI: 1.09-1.28), 4.1 × 10(-5) (P value for heterogeneity of ORs by PR status = 2.3 × 10(-4))]. There was no evidence for breast cancer risk associations with SNPs in the endothelial-specific pathway utilizing ALK1/SMADs 1&5 that promotes angiogenesis.

CONCLUSION

Common variation in the TGF-β ALK5/SMADs 2&3 signaling pathway, which initiates signaling at the cell surface to inhibit cell proliferation, might be related to risk of specific tumor subtypes.

IMPACT

The subtype specific associations require very large studies to be confirmed.

CDH1 promoter polymorphism and stomach cancer susceptibility

The relationship of stomach cancer susceptibility and the presence of E-cadherin (CDH1) promoter -160 C/A polymorphism had been reported with conflicting results. To further explore the association of this polymorphism with stomach cancer susceptibility, we performed an extensive search of relevant studies and carried out a meta-analysis to obtain a more precise estimate. A total of 16 studies including 2,611 cases and 3,788 controls were involved in this meta-analysis. When all studies involved, the meta-analysis results suggest no statistically significant association between CDH1 -160 C/A polymorphism and stomach cancer risk (CA vs. CC: OR = 1.01, 95% CI: 0.85-1.19; AA vs. CC: OR = 1.05, 95% CI: 0.75-1.46; dominant model: OR = 1.02, 95% CI: 0.86-1.20; recessive model: OR = 1.04, 95% CI: 0.76-1.41). When subgroup analyses were performed by ethnicity, the A-allele carriers conferred a decreased stomach cancer risk in Asians (AA vs. CC: OR = 0.67, 95% CI: 0.47-0.96; dominant model: OR = 0.85, 95% CI: 0.72-0.99), but no statistically significant association was found in Caucasians. In conclusion, this meta-analysis suggests that CDH1 -160 A-allele may play a protective role of stomach cancer development in Asians but not in Caucasians.

Using epidemiology and genomics to understand osteosarcoma etiology

Osteosarcoma is a primary bone malignancy that typically occurs during adolescence but also has a second incidence peak in the elderly. It occurs most commonly in the long bones, although there is variability in location between age groups. The etiology of osteosarcoma is not well understood; it occurs at increased rates in individuals with Paget disease of bone, after therapeutic radiation, and in certain cancer predisposition syndromes. It also occurs more commonly in taller individuals, but a strong environmental component to osteosarcoma risk has not been identified. Several studies suggest that osteosarcoma may be associated with single nucleotide polymorphisms in genes important in growth and tumor suppression but the studies are limited by sample size. Herein, we review the epidemiology of osteosarcoma as well as its known and suspected risk factors in an effort to gain insight into its etiology.

Cyclin D1 G870A polymorphism and breast cancer risk: a meta-analysis comprising 9,911 cases and 11,171 controls

Cyclin D1 represents a key molecule in the regulation of cell cycle. CCND1 G870A (rs603965) polymorphism has drawn considerable attention as the A allele may generate a variant splice product with possible oncogenic actions. A meta-analysis examining the association between CCND1 G870A polymorphism and breast cancer risk was performed. Separate analyses on Caucasian and Chinese populations were also implemented. Eligible articles were identified for the period up to July 2010. Pooled odds ratios (OR) were appropriately derived from fixed-effects or random-effects models. Sensitivity analysis excluding studies whose genotype frequencies in controls significantly deviated from Hardy-Weinberg Equilibrium (HWE) was performed. Nine case-control studies on Caucasians (7,304 cases and 8,149 controls) and four case-control studies on Chinese (2,607 cases and 3,022 controls) were eligible. At the overall analysis the A allele seemed to be associated with elevated breast cancer risk; the effect seemed to be confined to homozygous carriers (pooled OR = 1.091, 95% CI: 1.008-1.179, P = 0.030, fixed effects) as heterozygous carriers did not exhibit significantly elevated breast cancer risk. No statistically significant associations were demonstrated in Caucasians. On the other hand, Chinese AA carriers exhibited marginally elevated breast cancer risk (pooled OR = 1.144, 95% CI: 0.984-1.329, P = 0.080, fixed effects). Nevertheless, the controls in two out of the four Chinese studies deviated from HWE. In conclusion, this meta-analysis suggests that the A allele of the CCND1 G870A polymorphism may confer additional breast cancer risk when it comes to homozygosity and Chinese populations. The need for additional, methodologically sound studies on Chinese populations seems warranted.

APE1 Asp148Glu gene polymorphism and lung cancer risk: a meta-analysis

Many studies have examined the association between the APE1 T1349G (Asp148Glu) gene polymorphisms and lung cancer risk in various populations, but their results have been inconsistent. To assess this relationship more precisely, a meta-analysis was performed. The PubMed, Embase, Web of Science, and CNKI database was searched for case-control studies published up to June 2010. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ultimately, ten studies, comprising 2,696 lung cancer cases and 3,948 controls were included. Overall, for the G allele carriers (TG + GG) versus homozygote TT, the pooled OR was 1.037 (95% CI = 0.928-1.159 P = 0.001 for heterogeneity), for GG versus TT the pooled OR was 0.997 (95% CI = 0.861-1.154 P = 0.005 for heterogeneity). In the stratified analysis by ethnicity, significantly risks were not found among Asians or Caucasians. However, in the subgroup analyses by smoking status, significantly risks were found among smokers not in non-smokers. This meta-analysis suggested that the APE1 T1349G (Asp148Glu) polymorphism was not associated with lung cancer risk among Asians or Caucasians. But, the APE1 G allele was an increased risk factor for developing lung cancer among smokers.

Tgf-beta signaling alterations and colon cancer

Colorectal cancer is the second most common cause of cancer-related death in the United States. Twin studies suggest that 35% of all colorectal cancer cases are inherited. High-penetrance tumor susceptibility genes account for at most 3-6% of all colorectal cancer cases and the remainder of the unexplained risk is likely due to a combination of low to moderate penetrance genes. Recent genome-wide association studies have identified several SNPs near genes belonging to the transforming growth factor beta (TGF-beta) superfamily such as GREM1 and SMAD7. Together with the recent discovery that constitutively decreased TGFBR1 expression is a potent modifier of colorectal cancer risk, these findings strongly suggest that germline variants of the TGF-beta superfamily may account for a sizeable proportion of colorectal cancer cases. The TGF-beta superfamily signaling pathways mediate many different biological processes during embryonic development, and in adult organisms they play a role in tissue homeostasis. TGF-beta has a central role in inhibiting cell proliferation and also modulates processes such as cell invasion, immune regulation, and microenvironment modification. Mutations in the TGF-beta type II receptor (TGFBR2) are estimated to occur in approximately 30% of colorectal carcinomas. Mutations in SMAD4 and BMPR1A are found in patients with familial juvenile polyposis, an autosomal dominant condition associated with an increased risk of colorectal cancer. This chapter provides an overview of the genetic basis of colorectal cancer and discusses recent discoveries related to alterations in the TGF-beta pathways and their role in the development of colorectal cancer.

Candidate gene association studies: successes and failures

Epidemiologic studies of twins indicate that 20-40% of common tumors such as breast, colorectal, and prostate cancers are inherited. However, the effect of high penetrance tumor susceptibility genes such as APC, BRCA1, BRAC2, MSH1, MLH2 and MSH6 only accounts for a small fraction of these cancers. Low to moderate penetrance tumor susceptibility genes likely account for the large remaining proportion of familial cancer risk. Candidate tumor susceptibility genes have been identified based on the discovery of tumor-specific mutations, in vitro experiments, as well as animal models of cancer. Translational studies based on in vitro and in vivo discoveries have led to the identification of novel phenotypes and genotypes associated with cancer in humans. Case-control studies followed by validation studies and meta-analyses have unveiled several novel tumor susceptibility genes, several of which belong to genes encoding metabolizing enzymes and genes from the TGF-beta signaling pathway. Together with genome-wide association studies, candidate gene approaches are likely to fill a large gap in our knowledge of the genetic basis of cancer within the next decade.

TNF-308 gene polymorphism is associated with COPD risk among Asians: meta-analysis of data for 6,118 subjects

Chronic obstructive pulmonary disease (COPD) is a complex polygenic disease in which gene-environment interactions play a critical role in disease onset and progression. The gene encoding tumor necrosis factor (TNF) is one of several candidate loci for the pathogenesis of COPD and is highly polymorphic. A number of studies have investigated the association between the TNF-308 polymorphisms and COPD risk in different populations, and resulted in inconsistent results. A systematic review and meta-analysis of the published studies were performed to gain a clearer understanding of this association. The PubMed, Embase, Web of Science, and CNKI databases were searched for case-control studies published from 1966 to April 2009. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Twenty-four eligible studies, comprising 2,380 COPD cases and 3,738 controls, were included in the meta-analysis. The pooled result showed that the TNF-308 polymorphisms were significantly associated with an increased risk of COPD (OR=1.335, 95% CI: 1.172-1.522, for allele A carriers versus G/G; OR=1.330, 95% CI=1.174-1.505, for allele A versus allele G). Subgroup analysis supported the results in the Asian populations, but not in the Caucasian populations. When the analysis was limited to only those studies in which the COPD cases and controls were smokers/ex-smokers, the pooled results supported the conclusion. This meta-analysis suggested that the TNF-308 A allele is a more significant risk factor for developing COPD among Asian populations, but not among Caucasians.

ARLTS1, MDM2 and RAD51 gene variations are associated with familial breast cancer

Genetic factors that contribute to the risk of breast cancer are largely not known and association studies have revealed several genes with low penetrance risk alleles for breast cancer. Analysis of these genes may provide important information on the risk factors affecting carcinogenesis. Variations in the ARLTS1, RAD51 and MDM2 genes have been associated with increased risk of different cancer types but for breast cancer the results are not consistent. In this study we investigated the role of the allelic variants in candidate genes acting in the tumor suppressor, DNA repair and p53 pathways as risk factors for familial breast cancer in 147 patients displaying characteristics of familial disease. Presence of the polymorphic variants were investigated by amplification of the corresponding regions and restriction fragment length polymorphism analysis. Genotype and allele frequencies in the patients were significantly different for all three variants. Our results indicate that the polymorphic variants might affect individual susceptibility towards breast cancer.