IGF1 CA repeat polymorphisms, lifestyle factors and breast cancer risk in the Long Island Breast Cancer Study Project

Genetic and molecular biology of breast cancer among Iranian patients

Abstract

Background, Breast cancer (BC) is one of the leading causes of cancer related deaths in Iran. This high ratio of mortality had a rising trend during the recent years which is probably associated with late diagnosis.

Main body

Therefore it is critical to define a unique panel of genetic markers for the early detection among our population. In present review we summarized all of the reported significant genetic markers among Iranian BC patients for the first time, which are categorized based on their cellular functions.

Conclusions

This review paves the way of introducing a unique ethnic specific panel of diagnostic markers among Iranian BC patients. Indeed, this review can also clarify the genetic and molecular bases of BC progression among Iranians.

The effects of genetic variants related to insulin metabolism pathways and the interactions with lifestyles on colorectal cancer risk

OBJECTIVES

Genetic variants in metabolic signaling pathways may interact with lifestyle factors, such as dietary fatty acids, influencing postmenopausal colorectal cancer (CRC) risk, but these interrelated pathways are not fully understood.

METHODS

In this study, we examined 54 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I/insulin traits and their signaling pathways and lifestyle factors in relation to postmenopausal CRC, using data from 6,539 postmenopausal women in the Women's Health Initiative Harmonized and Imputed Genome-Wide Association Studies. By employing a two-stage random survival forest analysis, we evaluated the SNPs and lifestyle factors by ranking them according to their predictive value and accuracy for CRC.

RESULTS

We identified four SNPs (IRS1 rs1801123, IRS1 rs1801278, AKT2 rs3730256, and AKT2 rs7247515) and two lifestyle factors (age and percentage calories from saturated fatty acids) as the top six most influential predictors for CRC risk. We further examined interactive effects of those factors on cancer risk. In the individual SNP analysis, no significant association was observed, but the combination of the four SNPs, age, and percentage calories from saturated fatty acid (≥11% per day) significantly increased the risk of CRC in a gene and lifestyle dose-dependent manner.

CONCLUSIONS

Our findings provide insight into gene-lifestyle interactions and will enable researchers to focus on individuals with risk genotypes to promote intervention strategies. Our study suggests the careful use of data on potential genetic targets in clinical trials for cancer prevention to reduce the risk for CRC in postmenopausal women.

Lack of association between genetic polymorphisms in IGF1 and IGFBP3 with twin births in a Brazilian population (Cândido Godói, Rio Grande do Sul)

Insulin-like growth factor (IGF-1) is an important peptide hormone involved in the reproduction and fetal development of mammals, and it is suggested that it may influence the human twinning rate. This study aimed to test such possible association, investigating the genetic polymorphisms IGF1 (CA)n and IGFBP3 rs2854744 in the population from Candido Godoi (CG), a small city located in the South of Brazil that has a high prevalence of twin births. A case-control study was performed comprising a total of 39 cases (representing about 40% of the mothers of twins who were born in CG after 1995) and 214 controls (mothers of non-twin children), 97 of whom were living in CG while 117 were living in Porto Alegre. DNA was extracted from blood leucocytes and genotyping was performed. According to the statistical analyses, there was no significant difference in the frequencies of both studied genetic polymorphisms when comparing case group with control group. Thus, our results pointed to a lack of association between IGF1 (CA)n and IGFBP3 rs2854744 polymorphisms and twin births in CG, but further investigations in other populations with different characteristics must be performed to confirm the role of IGF-I in human twinning.

Genetic Variants in Metabolic Signaling Pathways and Their Interaction with Lifestyle Factors on Breast Cancer Risk: A Random Survival Forest Analysis

Genetic variants in the insulin-like growth factor-I (IGF-I)/insulin resistance axis may interact with lifestyle factors, influencing postmenopausal breast cancer risk, but these interrelated pathways are not fully understood. In this study, we examined 54 single-nucleotide polymorphisms (SNP) in genes related to IGF-I/insulin phenotypes and signaling pathways and lifestyle factors in relation to postmenopausal breast cancer, using data from 6,567 postmenopausal women in the Women's Health Initiative Harmonized and Imputed Genome-Wide Association Studies. We used a machine-learning method, two-stage random survival forest analysis. We identified three genetic variants (AKT1 rs2494740, AKT1 rs2494744, and AKT1 rs2498789) and two lifestyle factors [body mass index (BMI) and dietary alcohol intake] as the top five most influential predictors for breast cancer risk. The combination of the three SNPs, BMI, and alcohol consumption (≥1 g/day) significantly increased the risk of breast cancer in a gene and lifestyle dose-dependent manner. Our findings provide insight into gene-lifestyle interactions and will enable researchers to focus on individuals with risk genotypes to promote intervention strategies. These data also suggest potential genetic targets in future intervention/clinical trials for cancer prevention in order to reduce the risk for breast cancer in postmenopausal women. Cancer Prev Res; 11(1); 44-51. ©2017 AACR.

IGF-1-mediated PKM2/β-catenin/miR-152 regulatory circuit in breast cancer

Dysregulation of miRNAs is important in breast cancer initiation and malignant progression. Recently we showed that miR-152 downregulation is associated with breast cancer development, yet the underlying mechanism of miR-152 remains to be well elucidated. In this study, we identified β-catenin as a new direct target of miR-152. MiR-152 inhibited cell proliferation by targeting and inhibiting both β-catenin and PKM2 expression. We found that miR-152 expression sensitized the breast cancer cells to paclitaxel treatment by inhibiting β-catenin and PKM2 expression. Intriguingly, IGF-1 induced β-catenin and PKM2 expression and enhanced β-catenin and PKM2 interaction. Subsequently, IGF-1-induced β-catenin and PKM2 complex translocated into the nucleus, which in turn activated expression of miR-152. These results suggested a regulatory circuit between miR-152, β-catenin and PKM2 in breast cancer. By using human clinical specimens, we also showed that miR-152 expression levels were negatively correlated with β-catenin and PKM2 levels in breast cancer tissues. Our findings provide new insights into a mechanism of miR-152 involved in β-catenin and PKM2 inhibition which would have clinical implication for the cancer development and new treatment option in the future.

Genetic variants and traits related to insulin-like growth factor-I and insulin resistance and their interaction with lifestyles on postmenopausal colorectal cancer risk

Genetic variants and traits in metabolic signaling pathways may interact with lifestyle factors such as obesity, physical activity, and exogenous estrogen (E), influencing postmenopausal colorectal cancer (CRC) risk, but these interrelated pathways are not fully understood. In this case-cohort study, we examined 33 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I (IGF-I)/ insulin resistance (IR) traits and signaling pathways, using data from 704 postmenopausal women in Women’s Health Initiative Observation ancillary studies. Stratifying by the lifestyle modifiers, we assessed the effects of IGF-I/IR traits (fasting total and free IGF-I, IGF binding protein-3, insulin, glucose, and homeostatic model assessment–insulin resistance) on CRC risk as a mediator or influencing factor. Six SNPs in the INS, IGF-I, and IGFBP3 genes were associated with CRC risk, and those associations differed between non-obese/active and obese/inactive women and between E nonusers and users. Roughly 30% of the cancer risk due to the SNP was mediated by IGF-I/IR traits. Likewise, carriers of 11 SNPs in the IRS1 and AKT1/2 genes (signaling pathway–related genetic variants) had different associations with CRC risk between strata, and the proportion of the SNP–cancer association explained by traits varied from 30% to 50%. Our findings suggest that IGF-I/IR genetic variants interact with obesity, physical activity, and exogenous E, altering postmenopausal CRC risk, through IGF-I/IR traits, but also through different pathways. Unraveling gene–phenotype–lifestyle interactions will provide data on potential genetic targets in clinical trials for cancer prevention and intervention strategies to reduce CRC risk.

Interaction of insulin-like growth factor-I and insulin resistance-related genetic variants with lifestyle factors on postmenopausal breast cancer risk

PURPOSE

Genetic variants and traits in metabolic signaling pathways may interact with obesity, physical activity, and exogenous estrogen (E), influencing postmenopausal breast cancer risk, but these inter-related pathways are incompletely understood.

METHODS

We used 75 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I (IGF-I)/insulin resistance (IR) traits and signaling pathways, and data from 1003 postmenopausal women in Women's Health Initiative Observation ancillary studies. Stratifying via obesity and lifestyle modifiers, we assessed the role of IGF-I/IR traits (fasting IGF-I, IGF-binding protein 3, insulin, glucose, and homeostatic model assessment-insulin resistance) in breast cancer risk as a mediator or influencing factor.

RESULTS

Seven SNPs in IGF-I and INS genes were associated with breast cancer risk. These associations differed between non-obese/active and obese/inactive women and between exogenous E non-users and users. The mediation effects of IGF-I/IR traits on the relationship between these SNPs and cancer differed between strata, but only roughly 35% of the cancer risk due to the SNPs was mediated by traits. Similarly, carriers of 20 SNPs in PIK3R1, AKT1/2, and MAPK1 genes (signaling pathways-genetic variants) had different associations with breast cancer between strata, and the proportion of the SNP-cancer relationship explained by traits varied 45-50% between the strata.

CONCLUSIONS

Our findings suggest that IGF-I/IR genetic variants interact with obesity and lifestyle factors, altering cancer risk partially through pathways other than IGF-I/IR traits. Unraveling gene-phenotype-lifestyle interactions will provide data on potential genetic targets in clinical trials for cancer prevention and intervention strategies to reduce breast cancer risk.

Insulin-like Growth Factor 1 gene polymorphism and breast cancer risk

Insulin-like Growth Factor-1 (IGF-1) gene polymorphism has been associated with an increased risk for breast cancer. IGF-1 is a key regulator of proliferation, cell differentiation and apoptosis. It has important mitogenic and anti-apoptotic activities in normal cells and in breast cancer cells, acting synergistically with estrogen to increase neoplastic cell proliferation. This review aims to present the recent finds of IGF-1 gene polymorphism and its relationship with the risk of breast cancer through following the polymorphic dinucleotide repeat cytosine-adenine (CA) and single nucleotide polymorphisms (SNPs) by searching in the PubMed database publications focused studies published from 2010 to 2015 related to IGF-1 gene polymorphism and breast cancer risk. A growing number of studies support an association between IGF-1 gene polymorphism and breast cancer risk with conflicting results, nevertheless elucidation of the patterns of IGF-1 gene expression may permit characterization of women at high-risk for breast cancer, as well as the development of strategies for early diagnosis and efficient treatment against the disease.

The mechanism of transactivation regulation due to polymorphic short tandem repeats (STRs) using IGF1 promoter as a model

Functional short tandem repeats (STR) are polymorphic in the population, and the number of repeats regulates the expression of nearby genes (known as expression STR, eSTR). STR in IGF1 promoter has been extensively studied for its association with IGF1 concentration in blood and various clinical traits and represents an important eSTR. We previously used an in-vitro luciferase reporter model to examine the interaction between STRs and SNPs in IGF1 promoter. Here, we further explored the mechanism how the number of repeats of the STR regulates gene transcription. An inverse correlation between the number of repeats and the extent of transactivation was found in a haplotype consisting of three promoter SNPs (C-STR-T-T). We showed that these adjacent SNPs located outside the STR were required for the STR to function as eSTR. The C allele of rs35767 provides a binding site for CCAAT/enhancer-binding-protein δ (C/EBPD), which is essential for the gradational transactivation property of eSTR and FOXA3 may also be involved. Therefore, we propose a mechanism in which the gradational transactivation by the eSTR is caused by the interaction of one or more transcriptional complexes located outside the STR, rather than by direct binding to a repeat motif of the STR.

A polymorphic repeat in the IGF1 promoter influences the risk of endometrial cancer

Due to the lack of high-throughput genetic assays for tandem repeats, there is a paucity of knowledge about the role they may play in disease. A polymorphic CA repeat in the promoter region of the insulin-like growth factor 1 gene (IGF1 has been studied extensively over the past 10 years for association with the risk of developing breast cancer, among other cancers, with variable results. The aim of this study was to determine if this CA repeat is associated with the risk of developing breast cancer and endometrial cancer. Using a case-control design, we analysed the length of this CA repeat in a series of breast cancer and endometrial cancer cases and compared this with a control population. Our results showed an association when both alleles were considered in breast and endometrial cancers (P=0.029 and 0.011, respectively), but this did not pass our corrected threshold for significance due to multiple testing. When the allele lengths were analysed categorically against the most common allele length of 19 CA repeats, an association was observed with the risk of endometrial cancer due to a reduction in the number of long alleles (P=0.013). This was confirmed in an analysis of the long alleles separately for endometrial cancer risk (P=0.0012). Our study found no association between the length of this polymorphic CA repeat and breast cancer risk. The significant association observed between the CA repeat length and the risk of developing endometrial cancer has not been previously reported.

Microsatellite polymorphism in the P1 promoter region of the IGF‑1 gene is associated with endometrial cancer

Endometrial carcinoma (EC) is the most common type of gynecological malignancy. Studies have demonstrated that the insulin growth factor (IGF) pathway is implicated in the development of endometrial tumors and that the serum levels of IGF-1 are affected by estrogen. Most EC cells with high microsatellite instability (MSI-H) accumulate mutations at a microsatellite sequence in the IGF-1 gene. The present study investigated the CA repeat polymorphism in the P1 promoter region of the IGF-1 gene among Caucasian females with endometrial hyperplasia, EC and healthy control subjects, whose blood serum and surgical tissue specimens were analyzed. Differences or correlations between the analyzed parameters [serum levels of IGF-1 and IGF binding protein (IGFBP)-1 and IGFBP-3 as well as estrogens among the polymorphisms] were verified using the χ², Mann-Whitney U, Kruskal-Wallis or Spearman's rank correlation tests. A PCR amplification and DNA sequencing analysis was used for identification of (CA)_n repeats in the P1 region of IGF-1. ELISA was used to determine the blood serum levels of IGF-1, IGFBP-1, IGFBP-3 and estrogens. Furthermore, IGF-1 was assessed in endometrial tissues by immunohistochemical analysis. The present study indicated no statistically significant differences between serum levels of IGF-1, IGFBP-1, IGFBP-3 and estrone, estriol and estradiol in the control and study groups. A significant correlation was identified between the IGF-1 levels and estrone levels in the MSI-H polymorphism (r=−0.41, P=0.012) as well as a highly negative correlation between IGF-1 levels and the estradiol levels in the MSI-H polymorphism (r=−0.6, P=0.002). Genotypes without the 19 CA allele were predominantly found in EC. Furthermore, statistical analysis indicated that the number of IGF-1-expressing cells was significantly elevated in MSI-H type 18-20 (P= 0.0072), MSI-L type 19-20 (P=0.025) and microsatellite-stable MSS type 19-19 (P=0.024) compared with those in the MSI-H 20-20 genotype. The present study suggested that it is rather likely that the polymorphisms in the IGF-1 promoter are associated with EC in Caucasian females with regard to its development. In the present study, polymorphisms of the IGF-1 promoter may have been introduced during the genesis of EC and contributed to it by leading to aberrant expression of IGF-1.

The IGF1 P2 promoter is an epigenetic QTL for circulating IGF1 and human growth

Background

Even if genetics play an important role, individual variation in stature remains unexplained at the molecular level. Indeed, genome-wide association study (GWAS) have revealed hundreds of variants that contribute to the variability of height but could explain only a limited part of it, and no single variant accounts for more than 0.3% of height variance. At the interface of genetics and environment, epigenetics contributes to phenotypic diversity. Quantifying the impact of epigenetic variation on quantitative traits, an emerging challenge in humans, has not been attempted for height. Since insulin-like growth factor 1 (IGF1) controls postnatal growth, we tested whether the CG methylation of the two promoters (P1 and P2) of the IGF1 gene is a potential epigenetic contributor to the individual variation in circulating IGF1 and stature in growing children.

Results

Child height was closely correlated with serum IGF1. The methylation of a cluster of six CGs located within the proximal part of the IGF1 P2 promoter showed a strong negative association with serum IGF1 and growth. The highest association was for CG-137 methylation, which contributed 13% to the variance of height and 10% to serum IGF1. CG methylation (studied in children undergoing surgery) was approximately 50% lower in liver and growth plates, indicating that the IGF1 promoters are tissue-differentially methylated regions (t-DMR). CG methylation was inversely correlated with the transcriptional activity of the P2 promoter in mononuclear blood cells and in transfection experiments, suggesting that the observed association of methylation with the studied traits reflects true biological causality.

Conclusions

Our observations introduce epigenetics among the individual determinants of child growth and serum IGF1. The P2 promoter of the IGF1 gene is the first epigenetic quantitative trait locus (QTL^epi) reported in humans. The CG methylation of the P2 promoter takes place among the multifactorial factors explaining the variation in human stature.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0062-8) contains supplementary material, which is available to authorized users.

Analysis of cytosine-adenine repeats in P1 promoter region of IGF-1 gene in peripheral blood cells and cervical tissue samples of females with cervical intraepithelial lesions and squamous cervical cancer

High oncogenic risk human papillomaviruses (HPVs) are closely associated with cancer of the cervix. However, HPV infection alone may not be sufficient to cause cervical cancer, and other factors or cofactors may have a cumulative effect on the risk of progression from cervical HPV infection to cancer. The present study investigates the cytosine-adenine (CA) repeat polymorphism in the P1 promoter region of the insulin-like growth factor-1 (IGF-1) gene among cervical precancerous and cancer patients and healthy control females. The association between these polymorphisms, tissue and blood serum levels of IGF-1, and cervical cancer risk and progression is evaluated. The material for analysis consisted of blood cells and postoperative tissues from patients diagnosed with low-grade squamous intraepithelial lesions (L-SILs), high-grade squamous intraepithelial lesions (H-SILs) and invasive cervical cancer (ICC). A polymerase chain reaction amplification and the sequencing of DNA were used for the identification of (CA)_n repeats in the IGF-1 P1 region and detection of HPV DNA. The blood serum concentration of IGF was determined by enzyme-linked immunosorbent assay. The identification of the IGF-1 protein in the cervical tissues was performed by immunohistochemical analysis. The range of the length of the CA repeats in the study DNA was 11 to 21. However, the most common allele length and genotype in the control and study patients from serum and tissues was 19 CA repeats and a homozygous genotype of CA19/19. Statistically significant differences in the concentration of IGF-1 in the blood serum were observed between H-SILs and controls, only (p=0.047). However, the concentration of IGF-1 in the group of females with CA19/19, CA19<19 and CA19>19 was significantly higher in the group of patients with H-SIL (P=0.041) and ICC (P=0.048) in comparison with the control group. An association was detected between CA repeat length <19 and/or >19, IGF concentration in blood serum and tissues and the development of cervical cancer.

Mitochondrial D-loop and cytochrome oxidase C subunit I polymorphisms among the breast cancer patients of Mizoram, Northeast India

Mitochondrial DNA (mtDNA) is known for its high frequencies of polymorphisms and mutations as it is prone to oxidative stress. The aim of the present study is to assess the novel mutations in mitochondrial genes from blood samples among the breast cancer patients from a less studied Northeast Indian population. D, B, L haplogroups were observed in the cancer samples and a total of 44 mtDNA D-loop sequence variations at 42 distinct nucleotide positions were found. All the sequence variations were transitional substitutions and 6 were heteroplasmic states, except for a cytosine copy number change (9C/8C) at np 303e309 in three samples examined. A total of 88 Cytochrome Oxidase C subunit I (COXI) sequence differences with respect to the Revised Cambridge Reference Sequence (rCRS) were identified including 20 missense variants with 100 % sample mutation frequency. All 20 missense mutations are highly conserved with a Cumulate Index of 100 %. Among 88 COXI mutations, 24 (13 were Non-Synonymous and 11 were Synonymous) were not previously reported (novel mutation) in the literature or the public mtDNA mutation databases. Analysis of three-dimensional structure of COXI open reading frame (ORF) predicted the effect of one single codon (96R > C, 217T > I, 224-225GG > EE and 227D > T) mutations located in the signal peptide binding position. Analysis of mitochondrial DNA mutations, as a viable alternative, has the advantage of being capable of detecting inherent risk factors for breast cancer development.

Insulin-like growth factor-I gene polymorphism in acne vulgaris

BACKGROUND

Acne vulgaris is a multifactorial disease of the skin. Several studies have shown that elevated levels of serum insulin-like growth factor-I (IGF-I) correlate with overproduction of sebum and acne. Recently functional relationship between IGF-I (CA) polymorphism and circulating IGF-I levels in adults has been reported.

AIMS

The aim of our study was to investigate for the first time whether IGF-I (CA) polymorphism might be involved in the pathogenesis of acne or not.

METHODS

We included 115 acne patients and 117 healthy subjects to the study. The clinical grade of acne was assessed based on the Global Acne Grading System. Participants were questioned about diabetes mellitus, PCOS and other systemic disease. We searched for the IGF-I (CA) 19 polymorphism in this study. The IGF-I (CA) 19 polymorphism was performed by polymerase chain reaction.

RESULTS

We categorized the IGF-I (CA) 19 polymorphism area into three groups as lower than 192 bp, 192–194 bp and higher than 194 bp. We found that the frequency of genotype IGF-1 (CA) 19 gene was significantly different between control and acne patients (P = 0.0002). A significant association between IGF-I (CA) genotypes and severity of acne was found (P = 0.015). No significant difference was found between male and female patients (P > 0.05).

CONCLUSIONS

Our results suggest that IGF-I (CA) 19 polymorphism may contribute to a predisposition to acne in Turkish patients.

Insulin-like growth factor 1 gene polymorphism and breast cancer risk among arab omani women: a case-control study

Breast cancer is the most common cancer worldwide with significant global burden. Insulin-like growth factor 1 (IGF1) is an important regulator of cellular growth, differentiation, and apoptosis and mitogenic and antiapoptotic activities. Some studies suggested an association between cytosine adenine (CA) repeats gene polymorphisms of IGF1 and the risk of developing breast cancer while other studies did not find such an association. This study aims investigate the role of IGF1 (CA) repeats gene polymorphisms in the risk of developing breast cancer among Omani women.

METHODS

We analyzed (CA) repeats gene polymorphisms of IGF1 by extraction of genomic DNA from the peripheral blood of 147 patients with breast cancer and 134 control participants and performed genotyping using DNA sequencing.

RESULTS

Approximately 46% of patients carried the IGF (CA)(19) repeat allele, with 31.3% carrying two copies of this allele and 50% of controls carried the IGF (CA)(19) repeat allele with 30.1% carrying two copies of this allele. The difference of the IGF CA repeat groups was significant between cases and controls with (P =0.02). In contrast, there was no difference in the distribution of (CA)(19) repeat allele, (CA)(18) repeat allele and (CA)(19) repeat allele between cases and controls. The difference of the CA groups was significant between cases and controls among postmenopausal women with (P =0.026), whereas no difference was observed among postmenopausal subjects (P =0.429). In both pre- and postmenopausal groups there was no difference in the distribution of (CA)(19) repeat allele, (CA)(18) repeat allele and (CA)(20) repeat allele between patients and control subjects. On further IGF1 genotypes classification, we found an association between progesterone receptor status and the genotypes group where the non carrier of (CA)(19) repeat group was compared to (CA)(19) repeat carrier group (OR =2.482; 95% CI =1.119-5.503; P value =0.023).

CONCLUSION

Overall there was no association between the IGF (CA)(19) repeat and breast cancer in Omani females.

Insulin-like growth factor I (Igf-1) gene polymorphism in patients with non-metastatic breast cancer

We aimed to assess the association between IGF-I gene (CA repeats) polymorphism in breast cancer patients and their clinicopathological features, as well as disease recurrence and survival. Seventy-six non-metastatic breast cancer patients were enrolled in the present study. The IGF-I (CA) repeats were studied with polymerase chain reaction by using proper primers belonging to these gene areas from DNA samples. Results show that the non 19- non 19 homozygote were more common in patients without lymph node involvement (p=0.04), with low histological grade (p=0.04), with positive hormone receptor status (p=0.01), and in patients without recurrence (p=0.06). These results suggest that the non 19-non 19 carriers have some favorable prognostic factors, and IGF-I gene polymorphism (CA repeats) may affect disease recurrence and overall survival.

IGF gene polymorphisms and breast cancer in African-American and Hispanic women

Previous studies from our group and others have shown that increased circulatory levels of the ligand insulin-like growth factor 1 (IGF-1) and decreased levels of the predominant IGF-1 binding protein 3 (IGFBP-3) are associated with an increased incidence of breast cancer and poor outcome. Some studies suggest that, in addition to the influence of environmental factors on the levels of IGF-1 and IGFBP-3, alterations in their gene polymorphisms may play a significant role in the risk of cancer. In this study, we investigated the association between gene polymorphisms along the IGF axis and breast cancer, including the IGF-1 (CA) dinucleotide repeat, IGFBP-3 A-202C single nucleotide polymorphism, and the 2-bp deletion and (AGG)n repeat polymorphisms in the IGF type 1 receptor (IGF-IR). A total of 654 subjects, including both African-American and Hispanic/Latino subjects, were screened for various gene polymorphisms. IGF gene polymorphism genotyping was performed by PCR-GeneScan and PCR-RFLP methods. Our results demonstrated a significant association between the non-19/non-19 IGF-1 (CA)n polymorphism and breast cancer (OR = 1.75; 95% CI = 1.07-2.88; P = 0.027). Furthermore, absence of the wild-type-19 allele and alleles <(CA)19 were strongly associated with breast cancer (OR = 1.82; 95% CI = 1.20-2.77; P = 0.005 and OR = 1.70; 95% CI = 1.19-2.43; P = 0.003, respectively). The association of the non-19/non-19 polymorphism with breast cancer was also more significant in premenopausal women (P = 0.04). We did not find any significant association of the IGFBP-3 polymorphism with breast cancer. In the case of IGF-1R polymorphisms, the only significant trend was in the (AGG)5 allele; however, the frequency of this allele was very rare. In summary, our study demonstrated a significant association of IGF-1 polymorphisms and breast cancer. Future studies are necessary to understand the mechanistic value of these polymorphisms in breast cancer risk.

Physical confirmation and mapping of overlapping rat mammary carcinoma susceptibility QTLs, Mcs2 and Mcs6

Only a portion of the estimated heritability of breast cancer susceptibility has been explained by individual loci. Comparative genetic approaches that first use an experimental organism to map susceptibility QTLs are unbiased methods to identify human orthologs to target in human population-based genetic association studies. Here, overlapping rat mammary carcinoma susceptibility (Mcs) predicted QTLs, Mcs6 and Mcs2, were physically confirmed and mapped to identify the human orthologous region. To physically confirm Mcs6 and Mcs2, congenic lines were established using the Wistar-Furth (WF) rat strain, which is susceptible to developing mammary carcinomas, as the recipient (genetic background) and either Wistar-Kyoto (WKy, Mcs6) or Copenhagen (COP, Mcs2), which are resistant, as donor strains. By comparing Mcs phenotypes of WF.WKy congenic lines with distinct segments of WKy chromosome 7 we physically confirmed and mapped Mcs6 to ∼33 Mb between markers D7Rat171 and gUwm64-3. The predicted Mcs2 QTL was also physically confirmed using segments of COP chromosome 7 introgressed into a susceptible WF background. The Mcs6 and Mcs2 overlapping genomic regions contain multiple annotated genes, but none have a clear or well established link to breast cancer susceptibility. Igf1 and Socs2 are two of multiple potential candidate genes in Mcs6. The human genomic region orthologous to rat Mcs6 is on chromosome 12 from base positions 71,270,266 to 105,502,699. This region has not shown a genome-wide significant association to breast cancer risk in pun studies of breast cancer susceptibility.

Polymorphic CA repeat length in insulin-like growth factor 1 and risk of breast cancer in Iranian women

To evaluate the association between breast cancer and cytosine-adenine (CA) dinucleotide repeat length polymorphisms in the promoter region of the Insulin-like Growth Factor 1 (IGF-1) gene, a case-control study of 215 breast cancer patients and 224 controls was conducted in Iranian women. The most common allele and genotype in both controls and patients were an allele length of 19 and a homozygous genotype of (CA)(19)/(CA)(19). Women with two alleles longer than 19 were found to be at a higher risk of breast cancer with an odds ratio of 4.1 (P = 0.0002). In contrast, women with two alleles shorter than 20 were at lower risk of breast cancer. These results suggest a novel association between CA repeat length in IGF-1 and risk of breast cancer.

Haplotype effect in the IGF1 promoter accounts for the association between microsatellite and serum IGF1 concentration

OBJECTIVE

Systemic insulin-like growth factor 1 (IGF1) level is an important risk factor for various diseases. The inter-individual variation of serum IGF1 is determined by environmental and genetic factors, which are attributed to a microsatellite in IGF1 promoter. However, the exact nature of the underlying regulatory elements accounting for this association has not been characterized. Here, we defined the haplotype patterns, including both SNPs and the microsatellite, in the Chinese population, and investigated their regulatory effect on serum IGF1 level. This is the first study in which haplotype patterns of the microsatellite and SNPs in the IGF1 promoter are examined together.

METHODS

The linkage disequilibrium (LD) patterns of IGF1 were examined using tagSNPs of the IGF1 regulatory region. The microsatellite, three tagSNPs and haplotypes were correlated with serum IGF1 concentration in 450 normal premenopausal Chinese women.

RESULTS

Common alleles of the microsatellite were in strong LD with the three tagSNPs and were associated with particular haplotypes composed of SNPs. Neither the CA repeat number nor SNPs alone showed a robust association with serum IGF1 concentration. On the other hand, the haplotype T-19-A-T was significantly associated with serum IGF1 level.

CONCLUSION

No association was found between SNPs and microsatellite alone. However, the haplotype showed better correlation with serum IGF1 level. The results indicate that the previously observed correlation with microsatellite was because of a haplotype effect in the IGF1 promoter. Microsatellite or tagSNPs alone are not the primary regulatory elements of IGF1 expression. The exact regulatory genetic variant needs to be defined by functional genetic studies.

The association between IGF1 CA repeat polymorphisms and breast cancer risk: a meta-analysis

IGF-I CA repeat polymorphisms have been reported to influence the risk for breast cancer in many studies; however, the results still remains controversial and ambiguous. Therefore, to determine more precise estimations for the relationship, a meta-analysis was performed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association. A total of 9 studies including 5641 cases and 10471 controls were involved in this meta-analysis. All studies investigated the association between (CA)19 repeat polymorphism and breast cancer risk. Of those, four studies investigated the association between (CA)20 repeat polymorphism and breast cancer risk (2585 cases and 2847 controls), and three studies were for (CA)17 repeat polymorphism (2122 cases and 2225 controls). The overall odds ratio (OR) for the (CA)19 versus non-(CA)19 allele was 1.002 (95% CI 0.972-1.033). There was no suggestion of an overall effect either in recessive or dominant modeling of (CA)19 allele effects (dominant model: OR = 1.000 95% CI 0.872-1.147; recessive model: OR = 0.959 95% CI 0.888-1.036). The comparison of (CA)19 homozygosity versus non-(CA)19 homozygosity also showed no differential susceptibility to breast cancer (OR = 0.974, 95% CI 0.838-1.132). In the subgroup analysis by menopausal status, no statistically significantly increased risk was found among premenopausal or postmenopausal women. When stratified by ethnicity, no significant association was found in all genetic models. Furthermore, there was no evidence that two other alleles associated with the risk of breast cancer (CA17 vs. non-CA17: OR = 1.165 95% CI 0.634-2.141; CA20 vs. non-CA20: OR = 1.019 95% CI 0.909-1.143). In conclusion, the current meta-analysis suggests that three IGF-I (CA) repeat polymorphisms had no association to breast cancer risk.

Germline HVR-II mitochondrial polymorphisms associated with breast cancer in Tunisian women

A high incidence of somatic mtDNA polymorphisms has been reported in a wide variety of human cancers; some of them have been proposed as markers for the early detection of breast cancer. However, little attention has been paid to the potential of germline mitochondrial sequence variations as genetic risk factors for cancer. We performed a case-control study of 70 unrelated Tunisian women with breast cancer and 80 healthy age- and gender-matched blood donors, taking into account clinicopathological data, to evaluate germline polymorphism of mitochondrial HVR-II region as a genetic risk factor for breast cancer. Through direct sequencing, we detected 351 polymorphisms in controls and 248 variants in patients, with 47 and 39 segregating sites, respectively. In both groups, more than 50% of the polymorphisms were due to four variants: 315 ins C, 309 ins C, 263 A>G, and 73 A>G. The HVR-II sequences were also classified into haplotypes on the basis of the polymorphisms. Fifty-nine different haplotypes were found, 20 of them shared between patients and controls. Both groups had specific haplotypes, 18 in breast cancer patients and 21 in controls. Statistical analysis revealed a weak protective effect against breast cancer risk for two mitochondrial polymorphisms - 152 T>C (odds ratio (OR) = 0.33, 95% confidence interval (CI) = 0.12-0.91) and 263 A>G (OR = 0.17, 95%CI = 0.06-0.47). In contrast, an increased risk of breast cancer was detected for the 315+C haplotype (OR = 11.66, 95%CI = 1.44-252.23). We conclude that mitochondrial variants can affect breast cancer risk. More extensive studies, involving different types of cancer and patients with different genetic makeup, will be required to improve our understanding of the effects of germline mtDNA polymorphisms on carcinogenesis.

LIMD1 is more frequently altered than RB1 in head and neck squamous cell carcinoma: clinical and prognostic implications

Introduction

To understand the role of two interacting proteins LIMD1 and pRB in development of head and neck squamous cell carcinoma (HNSCC), alterations of these genes were analyzed in 25 dysplastic head and neck lesions, 58 primary HNSCC samples and two HNSCC cell lines.

Methods

Deletions of LIMD1 and RB1 were analyzed along with mutation and promoter methylation analysis of LIMD1. The genotyping of LIMD1 linked microsatellite marker, hmlimD1, was done to find out any risk allele. The mRNA expression of LIMD1 and RB1 were analyzed by Q-PCR. Immunohistochemical analysis of RB1 was performed. Alterations of these genes were correlated with different clinicopathological parameters.

Results

High frequency [94% (78/83)] of LIMD1 alterations was observed in the samples studied. Compare to frequent deletion and methylation, mutation of LIMD1 was increased during tumor progression (P = 0.007). Six novel mutations in exon1 and one novel intron4/exon5 splice-junction mutation were detected in LIMD1 along with a susceptible hmlimD1 (CA)₂₀ allele. Some of these mutations [42% (14/33)] produced non-functional proteins. RB1 deletion was infrequent (27%). Highly reduced mRNA expression of LIMD1 (25.1 ± 19.04) was seen than RB1 (3.8 ± 8.09), concordant to their molecular alterations. The pRB expression supported this data. Tumors with LIMD1 alterations in tobacco addicted patients without HPV infection showed poor prognosis. Co-alterations of these genes led the worse patients' outcome.

Conclusions

Our study suggests LIMD1 inactivation as primary event than inactivation of RB1 in HNSCC development.

A microsatellite polymorphism in IGF1 gene promoter and longevity in a Han Chinese population

Background

Previous studies have suggested a probable association between the polymorphism of a microsatellite locus located in the promoter of IGF1 (Insulin-like growth factor 1) gene and the serum level of IGF1, as well as many age-related diseases. Based on these results, we hypothesized that this polymorphism may influence longevity in humans. We performed an association study in a Han Chinese population to test this hypothesis.

Findings

We recruited 493 elderly Han Chinese individuals (females ≥ 94; males ≥ 90) and 425 young individuals (controls) from Dujiangyan (Sichuan province, China). The genotype distributions and allele frequencies of the microsatellite site in the elderly and control groups were compared by chi square test.

Our results suggested that there was no association between the microsatellite polymorphism and longevity in our Han Chinese population. However, there were more male persons with 18/21 genotype in elderly group than that in control group (11.11 vs. 5.45%, p = 0.011). As the difference was not significant when corrected by Bonferroni method, we speculate that the 18/21 genotype can not be functional in longevity; however, it may link with the real functional loci as there is a long haplotype block embracing the microsatellite locus.

Conclusions

There was no association between polymorphism of the microsatellite in promoter of IGF1 gene and longevity in our study. Future association studies containing the long haplotype block are deserved and can test our speculation of the potential linkage of 18/21 genotype and functional loci.

Genetic variation in insulin-like growth factor signaling genes and breast cancer risk among BRCA1 and BRCA2 carriers

Introduction

Women who carry mutations in BRCA1 and BRCA2 have a substantially increased risk of developing breast cancer as compared with the general population. However, risk estimates range from 20 to 80%, suggesting the presence of genetic and/or environmental risk modifiers. Based on extensive in vivo and in vitro studies, one important pathway for breast cancer pathogenesis may be the insulin-like growth factor (IGF) signaling pathway, which regulates both cellular proliferation and apoptosis. BRCA1 has been shown to directly interact with IGF signaling such that variants in this pathway may modify risk of cancer in women carrying BRCA mutations. In this study, we investigate the association of variants in genes involved in IGF signaling and risk of breast cancer in women who carry deleterious BRCA1 and BRCA2 mutations.

Methods

A cohort of 1,665 adult, female mutation carriers, including 1,122 BRCA1 carriers (433 cases) and 543 BRCA2 carriers (238 cases) were genotyped for SNPs in IGF1, IGF1 receptor (IGF1R), IGF1 binding protein (IGFBP1, IGFBP2, IGFBP5), and IGF receptor substrate 1 (IRS1). Cox proportional hazards regression was used to model time from birth to diagnosis of breast cancer for BRCA1 and BRCA2 carriers separately. For linkage disequilibrium (LD) blocks with multiple SNPs, an additive genetic model was assumed; and for single SNP analyses, no additivity assumptions were made.

Results

Among BRCA1 carriers, significant associations were found between risk of breast cancer and LD blocks in IGF1R (global P = 0.011 for LD block 2 and global P = 0.012 for LD block 11). Among BRCA2 carriers, an LD block in IGFBP2 (global P = 0.0145) was found to be associated with the time to breast cancer diagnosis. No significant LD block associations were found for the other investigated genes among BRCA1 and BRCA2 carriers.

Conclusions

This is the first study to investigate the role of genetic variation in IGF signaling and breast cancer risk in women carrying deleterious mutations in BRCA1 and BRCA2. We identified significant associations in variants in IGF1R and IRS1 in BRCA1 carriers and in IGFBP2 in BRCA2 carriers. Although there is known to be interaction of BRCA1 and IGF signaling, further replication and identification of causal mechanisms are needed to better understand these associations.

Genetic variation in IGF-1 and breast cancer risk in Ashkenazi carriers and noncarriers of BRCA1/2 mutations

Earlier studies indicate that high circulating levels of insulin-like growth factor-1 (IGF-1) may be associated with premenopausal breast cancer. We studied variations in the IGF-1 gene and the growth hormone (GH1) gene in relation to risk of breast cancer in 667 Ashkenazi Jewish women (321 cases, 346 controls) from a population-based case-control study in Northern Israel, and a clinical series of 331 founder BRCA mutation carriers (161 affected, 170 unaffected). All participants were tested for six polymorphisms in the IGF-1 gene and one GH1 polymorphism. Logistic regression models were used to estimate odds ratios for haplotype-specific and genotype-specific age-adjusted risks. Two common IGF-1 haplotypes (ATTCAC, GAGTGT) were found, when compared with the most prevalent haplotype ATTCGC (32.5%), to be associated with a decreased risk of breast cancer in premenopausal noncarrier women only. Age-adjusted odds ratios were 0.5 (95% confidence interval: 0.28-0.92) for ATTCAC and 0.46 (95% confidence interval: 0.24-0.89) for GAGTGT. The GH1 polymorphism did not influence the risk of breast cancer in our study population. The IGF-1 gene seems to be associated with breast cancer risk in premenopausal Ashkenazi Jewish women who are not carriers of mutations in BRCA1/2 genes.

Phenotypes and genotypes of insulin-like growth factor 1, IGF-binding protein-3 and cancer risk: evidence from 96 studies

Insulin-like growth factor 1 (IGF1) and its main binding protein, IGF-binding protein 3 (IGFBP3), play an important role in cancer development. Circulating levels and functional polymorphisms of IGF1 and IGFBP3 may be biomarkers of cancer development. However, the results of published studies remain conflicting rather than conclusive. We searched MEDLINE and EMBASE databases for all published studies related to circulating levels and polymorphisms of IGF1 and IGFBP3 and cancer risk. In all, 96 studies and over 110,000 subjects were available for this meta-analysis. Higher IGF1 circulating levels significantly increased 15% of cancer risk (odds ratio (OR), 1.15, 95% confidence interval (CI), 1.03-1.29), especially among prostate, pre-menopausal breast and colorectal cancer patients, whereas higher concentrations of IGFBP3 significantly decreased the risk of advanced prostate cancer by 56% (OR, 0.44, 95% CI, 0.25-0.77). Meanwhile, IGFBP3 -202CC genotype was associated with an increased risk of prostate cancer with borderline significance (OR, 1.18, 95% CI, 0.99-1.41). Genotype-phenotype correlation analyses showed that circulating levels of IGFBP3 could be modified by its promoter polymorphism A-202C (P < 0.001). In conclusion, circulating levels of IGF1, IGFBP3 and IGFBP3 A-202C play a crucial role in carcinogenesis and could serve as susceptibility biomarkers for cancer development.

Consumption of sweet foods and breast cancer risk: a case-control study of women on Long Island, New York

Several epidemiologic studies have reported a positive association between breast cancer risk and high intake of sweets, which may be due to an insulin-related mechanism. We investigated this association in a population-based case-control study of 1,434 cases and 1,440 controls from Long Island, NY. Shortly after diagnosis, subjects were interviewed in-person to assess potential breast cancer risk factors, and self-completed a modified Block food frequency questionnaire, which included 11 items pertaining to consumption of sweets (sweet beverages, added sugars, and various desserts) in the previous year. Using unconditional logistic regression models, we estimated the association between consumption of sweets and breast cancer. Consumption of a food grouping that included dessert foods, sweet beverages, and added sugars was positively associated with breast cancer risk [adjusted odds ratio (OR) comparing the highest to the lowest quartile: 1.27, 95% confidence interval (CI): 1.00-1.61]. The OR was slightly higher when only dessert foods were considered (OR: 1.55, 95% CI: 1.23-1.96). The association with desserts was stronger among pre-menopausal women (OR: 2.00, 95% CI: 1.32-3.04) than post-menopausal women (OR: 1.40, 95% CI: 1.07-1.83), although the interaction with menopause was not statistically significant. Our study indicates that frequent consumption of sweets, particularly desserts, may be associated with an increased risk of breast cancer. These results are consistent with other studies that implicate insulin-related factors in breast carcinogenesis.

Non-B DNA conformations as determinants of mutagenesis and human disease

Repetitive DNA motifs may fold into non-B DNA structures, including cruciforms/hairpins, triplexes, slipped conformations, quadruplexes, and left-handed Z-DNA, thereby representing chromosomal targets for DNA repair, recombination, and aberrant DNA synthesis leading to repeat expansion or genomic rearrangements associated with neurodegenerative and genomic disorders. Hairpins and quadruplexes also determined the relative abundances of simple sequence repeats (SSR) in vertebrate genomes, whereas strong base stacking has permitted the expansion of purine.pyrimidine-rich SSR during evolutionary time. SSR are enriched in regulatory and cancer-related gene classes, where they have been actively recruited to participate in both gene and protein functions. SSR polymorphic alleles in the population are associated with cancer susceptibility, including within genes that appear to share regulatory circuits involving reactive oxygen species.

Family-based genetic association study of insulin-like growth factor I microsatellite markers and premenopausal breast cancer risk

Several studies suggest that higher circulating insulin-like growth factor I (IGF-I) levels are associated with premenopausal breast cancer risk. Breast cancer risk and circulating IGF-I concentration appear to be partly heritable, thus genetic variation at IGF1 could influence IGF-I levels and breast cancer risk. We investigated the association of IGF1 CA repeat variants with premenopausal breast cancer risk using a family-based design. The study sample included 840 families from the Ontario Familial Breast Cancer Registry (OFBCR) and the Australian Breast Cancer Family Registry (ABCFR). Three CA repeat variants, at 5', 3', and in intron 2 were genotyped (5'CA, 3'CA, In2CA). We found several nominally significant associations. The 5'CA-21 allele (P = 0.03) and In2CA-212 allele (P = 0.04) were associated with lower risk, and the In2CA-216 allele with higher risk (P = 0.04) for the combined ABCFR-OFBCR. These associations were not significant after taking into account multiple comparisons. In2CA-216 was more strongly associated with risk when we used a recessive instead of an additive model (P = 0.01). 5'CA alleles of repeat length 18-20 were associated with higher risk (P = 0.02), and 5'CA alleles of >20 repeats were associated with lower risk (P = 0.01). These associations were significant in the OFBCR (In2CA-216 recessive, P = 0.02; 5'CA 18-20 and >20 allele grouping, P = 0.01) but not strongly supported by the ABCFR (In2CA-216 recessive, P = 0.14; 5'CA 18-20, P = 0.25; 5'CA >20, P = 0.20). The associations we found could be due to chance as many comparisons were made. Our results do not strongly support an association between these IGF1 variants and breast cancer risk.

Association of mitochondrial DNA displacement loop (CA)n dinucleotide repeat polymorphism with breast cancer risk and survival among Chinese women

Mitochondrial genome alternations may be involved in carcinogenesis. The noncoding region of the mitochondrial DNA (mtDNA) displacement loop (D-loop) has emerged as a mutational hotspot. Using data from a population-based case-control study conducted among Chinese women in Shanghai, we evaluated associations of breast cancer risk and survival with the mtDNA D-loop (CA)(n) dinucleotide repeat polymorphism. Included in the study were 1,058 cases and 1,129 age frequency-matched community controls that participated in the Shanghai Breast Cancer Study between 1996 and 1998. Breast cancer patients were followed to determine intervals of overall survival and disease-free survival. Overall, there was no association between the mtDNA D-loop (CA)(n) repeat polymorphism and breast cancer risk. Patients with multiple alleles of the mtDNA D-loop (CA)(n) polymorphism (heteroplasmy) had significantly poorer disease-free survival than those with one allele of the mtDNA D-loop (CA)(n) polymorphism (hazard ratio 1.62; 95% confidence interval, 1.16-2.26). These results suggest that the mtDNA D-loop (CA)(n) repeat polymorphism may be associated with breast cancer survival. Additional studies with a larger sample size are warranted.

Association between IGF1 CA microsatellites and mammographic density, anthropometric measures, and circulating IGF-I levels in premenopausal Caucasian women

BACKGROUND

Results from several studies indicate that mammographic density, a strong risk factor for breast cancer, is greater in premenopausal women with higher circulating IGF-I levels. Both mammographic density and circulating IGF-I levels appear to be partly heritable traits. We hypothesized that in premenopausal women, IGF1 variants are associated with circulating IGF-I concentration, which in turn influences variation in breast density. Therefore, we examined the association of IGF1 polymorphisms with circulating IGF-I levels and mammographic density.

METHODS

Percentage density, amounts of dense and non-dense (fat) tissue, IGF-I levels, and BMI were measured in 163 premenopausal women. Three CA repeat polymorphisms were genotyped, one each at the 5' and 3' ends of IGF1 and one in intron 2.

RESULTS

The number of 19 alleles at the 5' polymorphism was associated with lower circulating levels of IGF-I (P = 0.02), whereas the number of 185 alleles at the 3' polymorphism was associated with higher percentage density (P = 0.03) and a smaller amount of non-dense tissue (P = 0.02). The strength of the effect of the 185 allele at 3' on percentage density was greatly reduced and statistical significance lost when BMI was included in regression models.

CONCLUSIONS

Our results suggest an association between the number of 185 alleles at 3' with percentage density. This association appears to be mediated by body composition and particularly body fat, as indicated by the association of 3' IGF1 genotype with non-dense (fat) tissue and the mediating effect of BMI on the association of 3' genotype with percentage density.

Genetic variation in IGFBP2 and IGFBP5 is associated with breast cancer in populations of African descent

The insulin-like growth factor (IGF) signaling pathway is thought to play a major role in the etiology of breast cancer. Although incidence rates of breast cancer overall are lower in African Americans than in Caucasians, African-American women have a higher incidence under age 40 years, are diagnosed with more advanced disease, and have poorer prognosis. We investigated the association of breast cancer and genetic variants in genes in the IGF signaling pathway in a population-based case-control study of African-American women. We found significant associations at a locus encompassing parts of the IGFBP2 and IGFBP5 genes on chromosome 2q35, which we then replicated in a case-control study of Nigerian women. Based on those initial findings, we genotyped a total of 34 single nucleotide polymorphisms (SNPs) across the region in both study populations. Statistically significant associations with breast cancer were observed across approximately 50 kb of DNA sequence encompassing three exons in the 3' end of IGFBP2 and three exons in the 3' end of IGFBP5. SNPs were associated with breast cancer risk with P values as low as P = 0.0038 and P = 0.01 in African-Americans and Nigerians, respectively. This study is the first to report associations between genetic variants in IGFBP2 and IGFBP5 and breast cancer risk.

How growth hormone may be linked to cancer: concerns and perspective

Recent evidence from epidemiology indicates that inter-individual variations in the growth hormone (GH)/IGF-I pathway affect the risk of individuals developing common epithelial cancers. This is supported by associations between normal common variants within genes from the pathway and these cancers, which excludes many potential confounding issues, such as reverse causality. This raises concern for the increasing numbers of patients treated with GH; although replacement therapy for GH-deficiency should aim to restore normality, which should then only incur a normal risk. The links with cancer also offers promising new opportunities. Clinical trials treating cancer patients with pharmaceuticals targeting the IGF-I receptor are well advanced with promising initial findings. In the future, there has to be much more emphasis within oncology on prevention and the GH/IGF-I pathway is one of few identified risk factors that are modifiable, not just by pharmaceutical, but also nutritional, interventions that may, in the long term, be more appropriate. Assessing the status of the GH/IGF-I pathway in individuals may also provide a means for targeting screening programs and preventative measures.

IGF-I in epithelial ovarian cancer and its role in disease progression

Insulin-like growth factor-I (IGF-I) is known to be involved in the development and progression of several types of solid tumors including ovarian cancer. IGF-I levels in local tissue is subject to both endocrine and paracrine/autocrine regulation. To investigate which regulation is more importantly involved in IGF-I action in ovarian cancer regarding tumor progression, we analyzed IGF-I mRNA expression (assuming only from paracrine/autocrine regulation) and peptide concentration (subject to both endocrine and paracrine/autocrine regulation) as well as a genetic polymorphism (CA dinucleotide repeats) in 215 epithelial ovarian cancer patients. Genomic DNA, total RNA and cytosol proteins were extracted from fresh tumor samples. Two alternatively spliced IGF-I transcripts (IGF-IA and IGF-IB) were analyzed using real-time PCR. Cytosol levels of free and total IGF-I were measured with enzyme-linked immunosorbent assay. DNA sizing analysis was performed to determine the CA polymorphism. The study showed that the CA polymorphism had a weak influence on IGF-I expression, but no effect on tumor progression. High levels of free, not total, IGF-I peptide were associated with elevated risk of disease progression (HR = 2.06; 95%CI: 1.22-3.50), and the association was independent of clinicopathologic features of the disease. One of the IGF-I transcripts (IGF-IA) had a similar but less significant impact on disease progression. Women with high IGF-I mRNA and peptide were at greater risk for disease progression compared to those with low in both (HR = 2.13; 95%CI: 1.13-3.95). These findings support the notion that IGF-I is involved in ovarian cancer progression and free IGF-I plays a more important role in the disease. The study also suggests that both endocrine and paracrine/autocrine are involved in the regulation of IGF-I activity in ovarian cancer.

Association of CA repeat polymorphism at intron 1 of insulin-like growth factor (IGF-I) gene with circulating IGF-I concentration, growth, and fatness in swine

Evidence is accumulating that intronic polymorphic cytosine-adenosine (CA) repeats may play a role in gene expression. In this work, we investigated whether a polymorphic CA short tandem repeat (STR) located at the first intron of the pig insulin-like growth factor I (IGF-I) gene influences plasma IGF-I concentration in pigs as well as phenotypic variation in growth and fatness traits. We measured plasma IGF-I levels at one to four time points from 35 to 215 days of age in 340 performance-tested Landrace and Duroc pigs previously genotyped for the IGF-I STR. Data were analyzed within breed with a linear mixed model with the number of CA repeats as a covariate. At least five alleles were segregating in each breed, differing in one to seven repeats. The results showed that in each breed, circulating IGF-I at 160 days of age increased with the length of the shortest allele, accounting for an average trend of 4.38 +/- 1.28 ng/ml of IGF-I per additional repeat (P = 0.001). Longer repeats were associated with early growth in Landrace boars (1.92 +/- 0.92 kg per CA at 160 days; P = 0.038) and with back fat thickness (-0.57 +/- 0.20 mm per CA; P = 0.005) and lean content (7.52 +/- 3.00 g/kg per CA at 105 kg; P = 0.013) adjusted for carcass weight in Duroc barrows, as expected from the effect of circulating IGF-I on these traits. The consistency of the results across populations supports the hypothesis that the length of the CA repeats at intron 1 of the IGF-I gene is associated with circulating IGF-I levels, and that this effect is not neutral with respect to growth and fatness.

IGF-1 CA repeat variant and breast cancer risk in postmenopausal women

IGF-I is an important growth factor for the mammary gland. We evaluated the relationship of the IGF-I CA(n) polymorphism with breast cancer risk in Caucasian postmenopausal women and performed a meta-analysis of published data. The IGF-I CA(n) polymorphism was genotyped in 4091 from the Rotterdam Study. A disease-free survival analysis was performed along with a meta-analysis of all available data on IGF-I CA(n) polymorphism and breast cancer risk. During follow-up 159 women were diagnosed with breast cancer. The disease-free survival analysis adjusted for age at entry, age at menopause, body mass index and waist hip ratio yielded a HR=0.97 (95% CI=0.59-1.58) for CA(19) non-carriers against carriers. The meta-analysis using the random-effects model gave a pooled OR of 1.26 (95% CI=0.95-1.82) for IGF-I CA(19) non-carriers versus CA(19) homozygous carriers. According to these results, the IGF-I CA(19) promoter polymorphism is not likely to predict the risk of breast cancer.

Polymorphisms of short tandem repeat of genes and breast cancer susceptibility

AIM

To explore the relationship of short tandem repeat polymorphisms and breast cancer susceptibility.

METHODS

We searched the MEDLINE database (up to June 2006) with the keywords of tandem repeat sequences, gene polymorphisms, breast cancer, cancer susceptibility and microsatellite instability. We reviewed the literature on gene polymorphisms, especially the relationship of short tandem repeat and breast cancer risk.

RESULTS

We focused on the candidate genes sex hormones, steroid hormone and receptors, carcinogen metabolism, cell proliferation regulation and other genes.

CONCLUSIONS

The functional effects of short tandem repeat polymorphisms on cancer susceptibility, especially on breast cancer risk, are identified. The importance of short tandem repeat polymorphisms on development and progression of breast cancer are discussed.

Absence of the common IGF1 19 CA-repeat allele is more common among BRCA1 mutation carriers than among non-carriers from BRCA1 families

BRCA1 mutations predispose to early-onset breast cancer. We previously reported an association between absence of the common IGF1 19 CA-repeat allele (IGF1-19/-19) and being a BRCA1 mutation carrier in young women from breast cancer high-risk families. Others have reported a four-fold risk of premenopausal breast cancer in women with a family history and the IGF1-19/-19 genotype. The aim of this study was to investigate whether the IGF1-19/-19 genotype was associated with being a BRCA1 mutation carrier among women from BRCA1 families. DNA was available from 268 women with known BRCA1 status from the South Swedish Health Care Region. IGF1 genotyping was successfully performed with fragment analysis in 211 women from 96 families. The IGF1-19/-19 genotype was significantly more common among BRCA1 mutation carriers (14.2%) than among non-carriers (4.8%), OR 3.3 (95%CI 1.11-9.78, P = 0.03) adjusted for family clustering. We confirmed our previous finding of an association between the IGF1-19/-19 genotype and BRCA1 mutation status. Since the IGF1-19/-19 genotype in combination with OC use or multiparity confers an increased risk for early onset breast cancer in high-risk women and in women from the general population, future studies are needed to elucidate the importance of the IGF1-19/-19 genotype concerning the variability in breast cancer risk among BRCA1 mutation carriers.

Absence of the common Insulin-like growth factor-1 19-repeat allele is associated with early age at breast cancer diagnosis in multiparous women

Multiparity decreases the risk of breast cancer in white women, whereas it is a risk factor in black women <50 years. Early-onset breast cancer (<50 years) has been associated with high insulin-like growth factor-1 (IGF-1) levels. Absence of the common IGF1 19 cytosine-adenine (CA)-repeat allele (IGF1-19/-19) inverts the effect of several non-genetic factors on breast cancer risk but the interaction between IGF1-19/-19 and multiparity on breast cancer risk is unknown. As IGF1-19/-19, multiparity and early-onset breast cancer are more common in black than in white women, we aimed to study whether multiparity combined with IGF1-19/-19 increases the risk of early-onset breast cancer. Four hundred and three breast cancer patients diagnosed in Lund, Sweden, at age 25-99 years were genotyped for the IGF1 CA-repeat length using fragment analysis. Overall, 12.9% carried the IGF1-19/-19 genotype. There was a highly significant interaction between multiparity and IGF1-19/-19 on age at breast cancer diagnosis (P=0.007). Among IGF1-19/-19 patients, multiparity was associated with a 9.2 year earlier age at diagnosis compared with uniparity or nulliparity (P=0.006). Multiparity combined with IGF1-19/-19 was associated with an early age at breast cancer diagnosis. If confirmed, IGF1-19/-19 may help identify a subgroup of women for earlier breast cancer screening.

The GH1/IGF-1 axis polymorphisms and their impact on breast cancer development

The growth hormone 1/insulin-like growth factor-1 (GH1/IGF-1) axis plays an essential role in the development of the breast by regulating cell proliferation, differentiation and apoptosis. Imbalances within this axis lead to an aberrant signalling and recent research has focussed on the overexpression of these growth factors and their involvement in breast cancer development. The increased understanding of the molecular mechanisms and signalling pathways connected to the GH1/IGF-1 axis has provided important insights into aetiology, prevention and therapy for breast cancer. However, to identify the contribution of the GH1/IGF-1 signalling pathway to cancer risk still remains a challenge since the results of various studies are controversial. Here, we discuss the influence of low-penetrance polymorphisms in the genes along the GH1/IGF-1 axis and their impact on hormone levels and cancer risk, especially breast cancer. We point out what is known about the effects of the variants and show how the interaction of genetic variants affects breast cancer risk.