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

Genetic architecture of mammographic density as a risk factor for breast cancer: a systematic review

BACKGROUND

Mammography Density (MD) is a potential risk marker that is influenced by genetic polymorphisms and can subsequently modulate the risk of breast cancer. This qualitative systematic review summarizes the genes and biological pathways involved in breast density and discusses the potential clinical implications in view of the genetic risk profile for breast density.

METHODS

The terms related to "Common genetic variations" and "Breast density" were searched in Scopus, PubMed, and Web of Science databases. Gene pathways analysis and assessment of protein interactions were also performed.

RESULTS

Eighty-six studies including 111 genes, reported a significant association between mammographic density in different populations. ESR1, IGF1, IGFBP3, and ZNF365 were the most prevalent genes. Moreover, estrogen metabolism, signal transduction, and prolactin signaling pathways were significantly related to the associated genes. Mammography density was an associated phenotype, and eight out of 111 genes, including COMT, CYP19A1, CYP1B1, ESR1, IGF1, IGFBP1, IGFBP3, and LSP1, were modifiers of this trait.

CONCLUSION

Genes involved in developmental processes and the evolution of secondary sexual traits play an important role in determining mammographic density. Due to the effect of breast tissue density on the risk of breast cancer, these genes may also be associated with breast cancer risk.

Mammographic breast density and IGF-1 gene polymorphisms rs1520220, rs2946834 and rs6219 in Polish women

Aim of the study

The aim of the study was to analyze three single nucleotide polymorphisms – rs1520220, rs2946834, rs6219 – of the IGF-1 gene in the context of breast mammographic density.

Material and methods

The research material included 202 samples of the peripheral blood of women with increased mammographic breast density and 238 samples of the epithelium from the oral mucosa of women without diagnosed pathological changes of the breast and with no family history of breast and/or ovarian cancer. The real-time polymerase chain reaction method was applied for analysis of polymorphisms.

Results

rs1520220 polymorphism was associated with increased mammographic density of the breasts. The presence of the CC genotype in the IGF-1 gene increased the risk of developing higher breast density visible in mammography by 2.43-fold. CC homozygotes (rs1520220) correlated with higher Breast Imaging-Reporting and Data System scale (3 vs. 4 and 5) (OR = 5.6; 95% CI: 1.82–16.3, p = 0.001). In the present study no relationship was detected between rs6219 and rs2946834 polymorphism and mammographic breast density.

Conclusions

The results suggest that the rs1520220 polymorphism of the IGF-1 gene plays an important role in the occurrence of increased mammographic breast density.

Single nucleotide polymorphisms of insulin-like growth factor gene and mammographic breast density

Aim of the study

To analyze six single nucleotide polymorphisms (SNPs): rs1520220, rs2945834, rs5747694, rs6214, rs6219, rs5742678. An attempt was made to assess the significance of the above IGF-1 gene polymorphisms as prognostic and predictive factors in Polish women with diagnosed increased breast mammographic density.

Material and methods

The study included women diagnosed with an increased breast mammographic density (n = 98), breast cancer (n = 135) and women as a control group (n = 60). The method used to detect polymorphisms in the IGF-1 gene was the analysis of single-stranded DNA conformation polymorphism (SSCP-PCR) and Sanger’s sequencing.

Results

In the case of rs1520220 polymorphism, the genotype CC was found to increase the risk of breast cancer (OR = 2.6 95% CI 1.01-6.5, p = 0.04). Analysis of the rs2945834 polymorphism revealed that the occurrence of the G allele reduced the risk of breast cancer, while the occurrence of the A allele increased the risk of disease almost twice (OR = 0.55 95% CI). Among women who are heterozygous in terms of rs5747694 polymorphism (TG), the risk of breast cancer is twice as high as in the control group. The SNPs in the study group did not correlate with mammographic breast density.

Conclusions

The results obtained in the course of the analysis indicate that polymorphisms rs1520220, rs2946834, rs5747694 gene IGF-1 are associated with the occurrence of breast cancer but not with increased mammographic density. Summing up, the association between the polymorphisms of IGF-1 and the risk of developing breast cancer is independent of mammographic density.

Interaction between CA repeat microsatellites and HIF1α regulated the transcriptional activity of porcine IGF1 promoter

Insulin-like growth factor 1 (IGF1) is pivotal in the regulation of animal growth. Highly polymorphic CA repeat microsatellites have been identified in the IGF1 promoter region of different breeds of pigs. Previous studies showed that CA repeat microsatellites are associated with circulating IGF1 level. However, the mechanisms by which CA repeat microsatellites regulate IGF1 expression remain unclear. This study aimed to detect the association of CA repeat microsatellites with the transcriptional regulation of porcine IGF1 and the possible mechanisms. Results revealed that the number of CA repeats in porcine IGF1 promoter was 14-18, and a promoter with 14 or 15 CA repeats had a higher transcriptional activity (P < 0.01). Transcription factor hypoxia-inducible factor 1 subunit alpha (HIF1α) was confirmed to bind to the binding site upstream of CA repeat microsatellites. The microsatellites with 14 or 15 CA repeats were more sensitive to changes in the HIF1α expression level (P < 0.01). These results suggested that CA repeat microsatellites and HIF1α affected the transcriptional activity of each other in the regulation of IGF1 expression, thereby implying an interaction between them. Overall, this study provided novel evidence for elucidating the effects of CA repeat microsatellites on the transcriptional regulation of porcine IGF1.

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.

No association between genetic or epigenetic variation in insulin growth factors and antipsychotic-induced metabolic disturbances in a cross-sectional sample

AIM

Second-generation antipsychotics (SGA) are known to induce metabolic disturbances. Genetic pathways, such as the IGF pathway could be associated with increased metabolic syndrome (MetS). Additionally, IGF2 methylation varies as a function of environmental influences and is associated with schizophrenia and MetS. The current study aims to evaluate whether genetic and epigenetic variation in genes of the IGF pathway are associated with metabolic disturbances in patients under treatment with SGAs.

METHODS

Cross-sectional metabolic data from 438 patients with schizophrenia spectrum disorder was analyzed. Using the Sequenom MassARRAY iPLEX(TM) platform, 27 SNPs of the IGF1 and IGF2 genes and the IGF receptors IGF1R and IGF2R were genotyped. Methylation status of seven IGF2 CpG dinucleotides was evaluated using a Sequenom MALDI-TOF spectrometer.

RESULTS & CONCLUSION

There was a significant association between IGF2 methylation and genotype, but no significant association between genetic or epigenetic variability and metabolic parameters in the present study.

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.

Functional interaction between SNPs and microsatellite in the transcriptional regulation of insulin-like growth factor 1

A CA-repeat microsatellite in insulin-like growth factor 1 (IGF1) promoter was associated with interindividual variation of circulating IGF1 level. Previously, we reported that such association was due to variation of haplotype unit in a linkage disequilibrium block composed of microsatellite and single-nucleotide polymorphisms (SNPs), suggesting the presence of an interaction between them. In this study, reporter assays were performed to investigate the regulatory effect and interaction of genetic variants on gene expression. We used an in vitro system to compare the transcriptional activities of haplotypes (rs35767:T>C, the CA-repeat microsatellite, rs5742612:T>C, and rs2288377:T>A) in evolutionarily conserved region of IGF1 promoter. In haplotype C-T-T, a longer microsatellite had a lower transcriptional activity (17.6 ± 2.4-fold for 17 repeats and 8.3 ± 1.1-fold for 21 repeats), whereas in haplotype T-C-A, such trend could not be observed, as the microsatellite with 21 repeats had the highest transcriptional activity (17.5 ± 2.3-fold). Because the microsatellite and SNPs affected the transcriptional activity of each other, there may be an interaction between them in the regulation of IGF1 expression. For the first time, we demonstrated that a noncoding microsatellite polymorphism could act as a functional unit and interact with SNPs in the regulation of transcription in human genome.

Genetic variability in IGF-1 and IGFBP-3 and body size in early life

Background

Early life body size and circulating levels of IGF-1 and IGFBP-3 have been linked to increased risks of breast and other cancers, but it is unclear whether these exposures act through a common mechanism. Previous studies have examined the role of IGF-1 and IGFBP-3 genetic variation in relation to adult height and body size, but few studies have examined associations with birthweight and childhood size.

Methods

We examined whether htSNPs in IGF-1 and the IGFBP-1/IGFBP-3 gene region are associated with the self-reported outcomes of birthweight, body fatness at ages 5 and 10, and body mass index (BMI) at age 18 among healthy women from the Nurses’ Health Study (NHS) and NHSII. We used ordinal logistic regression to model odds ratios (ORs) and 95% confidence intervals (CI) of a one category increase for birthweight and somatotypes at ages 5 and 10. We used linear regression to model associations with BMI at age 18.

Results

Among 4567 healthy women in NHS and NHSII, we observed no association between common IGF-1 or IGFBP-1/IGFBP-3 SNPs and birthweight, body fatness at ages 5 and 10, or BMI at age 18.

Conclusions

Common IGF-1 and IGFBP-1/IGFBP-3 SNPs are not associated with body size in early life.

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.

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.

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.