Genotypes and haplotypes in the insulin-like growth factors, their receptors and binding proteins in relation to plasma metabolic levels and mammographic density

IGF1 and Insulin Receptor Single Nucleotide Variants Associated with Response in HER2-Negative Breast Cancer Patients Treated with Neoadjuvant Chemotherapy with or without a Fasting Mimicking Diet (BOOG 2013-04 DIRECT Trial)

AIM

We aimed to investigate associations between IGF1R and INSR single nucleotide variants (SNVs) and clinical response in patients with breast cancer treated with neoadjuvant chemotherapy with or without a fasting mimicking diet (FMD) from the DIRECT trial (NCT02126449), since insulin-like growth factor 1 (IGF1) and the insulin pathway are heavily involved in tumor growth and progression.

METHODS

Germline DNA from 113 patients was tested for 17 systematically selected candidate SNVs in IGF1R and INSR with pathological and radiological response.

RESULTS

IGF1R variants A > G (rs3743259) and G > A (rs3743258) are associated with worse pathological response compared to reference alleles p = 0.002, OR = 0.42 (95%CI: 0.24; 0.73); p = 0.0016; OR = 0.40 (95%CI: 0.23; 0.70). INSR T > C (rs1051690) may be associated with worse radiological response p = 0.02, OR = 2.92 (95%CI: 1.16; 7.36), although not significant after Bonferroni correction. Exploratory interaction analysis suggests that IGF1R SNVs rs2684787 and rs2654980 interact negatively with the FMD group regarding radiological response p = 0.036, OR = 5.13 (95%CI: 1.12; 23.63); p = 0.024, OR = 5.71 (95%CI: 1.26; 25.85).

CONCLUSIONS

The IGF1R variants rs3743259 and rs3743258 are negatively associated with pathological response in this cohort, suggesting potential relevance as a predictive biomarker. Further research is needed to validate these findings and elucidate the underlying mechanisms and interaction with FMD.

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.

2q35-rs13387042 variant and the risk of breast cancer: a case-control study

BACKGROUND

Breast Cancer is the most frequent neoplasm diagnosed among women worldwide. Genetic background and lifestyle/environment play a significant role in the disease etiology. According to Genome-wide association studies, some single-nucleotide polymorphisms such as 2q35-rs13387042-(G/A) have been introduced to be associated with breast cancer risk and features. In this study, we aimed to evaluate the association between this variant and the risk of breast cancer in a cohort of Iranian women.

METHODS

Demographics and clinical information were collected by interview and using patients' medical records, respectively. DNA was extracted from 506 blood samples, including 184 patients and 322 controls, and genotyping was performed using allele specific-PCR. SPSS v16 was used for statistical analysis.

RESULT

Statistically significant association was observed between AA genotype and disease risk in all patients [p_adj = 0.048; OR_adj = 2.13, 95% CI (1.01-4.50)] and also ER-positive breast cancers [p_adj = 0.015; OR_adj = 2.12, 95% CI (1.16-3.88)]. There was no association between rs13387042 and histopathological characteristics of the disease. Furthermore, overall survival was not statistically associated with genotype and allelic models even after adjustment for stage and receptor status (p > 0.05).

CONCLUSION

There is a statistically significant association between 2q35-rs13387042 and breast cancer risk. rs13387042-AA genotype might be a risk-conferring factor for breast cancer development in the Iranian population. However, further consideration is suggested to confirm its role in risk assessment and probable association with other genetic markers.

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.

Maternal transmission of an Igf2r domain 11: IGF2 binding mutant allele (Igf2rI1565A) results in partial lethality, overgrowth and intestinal adenoma progression

The cation-independent mannose 6-phosphate/insulin-like growth factor-2 receptor (M6P/IGF2R or IGF2R) traffics IGF2 and M6P ligands between pre-lysosomal and extra-cellular compartments. Specific IGF2 and M6P high-affinity binding occurs via domain-11 and domains-3-5-9, respectively. Mammalian maternal Igf2r allele expression exceeds the paternal allele due to imprinting (silencing). Igf2r null-allele maternal transmission results in placenta and heart over-growth and perinatal lethality (>90%) due to raised extra-cellular IGF2 secondary to impaired ligand clearance. It remains unknown if the phenotype is due to either ligand alone, or to both ligands. Here, we evaluate Igf2r specific loss-of-function of the domain-11 IGF2 binding site by replacing isoleucine with alanine in the CD loop (exon 34, I1565A), a mutation also detected in cancers. Igf2rI1565A/+p maternal transmission (heterozygote), resulted in placental and embryonic over-growth with reduced neonatal lethality (<60%), and long-term survival. The perinatal mortality (>80%) observed in homozygotes (Igf2rI1565A/I1565A) suggested that wild-type paternal allele expression attenuates the heterozygote phenotype. To evaluate Igf2r tumour suppressor function, we utilised intestinal adenoma models known to be Igf2 dependent. Bi-allelic Igf2r expression suppressed intestinal adenoma (ApcMin). Igf2rI1565A/+p in a conditional model (Lgr5-Cre, Apcloxp/loxp) resulted in worse survival and increased adenoma proliferation. Growth, survival and intestinal adenoma appear dependent on IGF2R-domain-11 IGF2 binding.

High-Resolution Bisulfite-Sequencing of Peripheral Blood DNA Methylation in Early-Onset and Familial Risk Breast Cancer Patients

PURPOSE

Understanding and explaining hereditary predisposition to cancer has focused on the genetic etiology of the disease. However, mutations in known genes associated with breast cancer, such as BRCA1 and BRCA2, account for less than 25% of familial cases of breast cancer. Recently, specific epigenetic modifications at BRCA1 have been shown to promote hereditary breast cancer, but the broader potential for epigenetic contribution to hereditary breast cancer is not yet well understood.

EXPERIMENTAL DESIGN

We examined DNA methylation through deep bisulfite sequencing of CpG islands and known promoter or regulatory regions in peripheral blood DNA from 99 patients with familial or early-onset breast or ovarian cancer, 6 unaffected BRCA mutation carriers, and 49 unaffected controls.

RESULTS

In 9% of patients, we observed altered methylation in the promoter regions of genes known to be involved in cancer, including hypermethylation at the tumor suppressor PTEN and hypomethylation at the proto-oncogene TEX14. These alterations occur in the form of allelic methylation that span up to hundreds of base pairs in length.

CONCLUSIONS

Our observations suggest a broader role for DNA methylation in early-onset, familial risk breast cancer. Further studies are warranted to clarify these mechanisms and the benefits of DNA methylation screening for early risk prediction of familial cancers.

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.

An intergenic risk locus containing an enhancer deletion in 2q35 modulates breast cancer risk by deregulating IGFBP5 expression

Breast cancer is the most diagnosed malignancy and the second leading cause of cancer mortality in females. Previous association studies have identified variants on 2q35 associated with the risk of breast cancer. To identify functional susceptibility loci for breast cancer, we interrogated the 2q35 gene desert for chromatin architecture and functional variation correlated with gene expression. We report a novel intergenic breast cancer risk locus containing an enhancer copy number variation (enCNV; deletion) located approximately 400Kb upstream to IGFBP5, which overlaps an intergenic ERα-bound enhancer that loops to the IGFBP5 promoter. The enCNV is correlated with modified ERα binding and monoallelic-repression of IGFBP5 following oestrogen treatment. We investigated the association of enCNV genotype with breast cancer in 1,182 cases and 1,362 controls, and replicate our findings in an independent set of 62,533 cases and 60,966 controls from 41 case control studies and 11 GWAS. We report a dose-dependent inverse association of 2q35 enCNV genotype (percopy OR = 0.68 95%CI 0.55-0.83, P = 0.0002; replication OR = 0.77 95% CI 0.73-0.82, P = 2.1 × 10-19) and identify 13 additional linked variants (r2 > 0.8) in the 20Kb linkage block containing the enCNV (P = 3.2 × 10-15 - 5.6 × 10-17). These associations were independent of previously reported 2q35 variants, rs13387042/rs4442975 and rs16857609, and were stronger for ER-positive than ER-negative disease. Together, these results suggest that 2q35 breast cancer risk loci may be mediating their effect through IGFBP5.

The role of the insulin-like growth factor-1 system in breast cancer

IGF-1 is a potent mitogen of major importance in the mammary gland. IGF-1 binding to the cognate receptor, IGF-1R, triggers a signaling cascade leading to proliferative and anti-apoptotic events. Although many of the relevant molecular pathways and intracellular cascades remain to be elucidated, a growing body of evidence points to the important role of the IGF-1 system in breast cancer development, progression and metastasis. IGF-1 is a point of convergence for major signaling pathways implicated in breast cancer growth. In this review, we provide an overview and concise update on the function and regulation of IGF-1 as well as the role it plays in breast malignancies.

Circulating IGF1 and IGF2 and SNP genotypes in men and pregnant and non-pregnant women

Circulating IGFs are important regulators of prenatal and postnatal growth, and of metabolism and pregnancy, and change with sex, age and pregnancy. Single-nucleotide polymorphisms (SNPs) in genes coding for these hormones associate with circulating abundance of IGF1 and IGF2 in non-pregnant adults and children, but whether this occurs in pregnancy is unknown. We therefore investigated associations of plasma IGF1 and IGF2 with age and genotype at candidate SNPs previously associated with circulating IGF1, IGF2 or methylation of the INS-IGF2-H19 locus in men (n=134), non-pregnant women (n=74) and women at 15 weeks of gestation (n=98). Plasma IGF1 concentrations decreased with age (P<0.001) and plasma IGF1 and IGF2 concentrations were lower in pregnant women than in non-pregnant women or men (each P<0.001). SNP genotypes in the INS-IGF2-H19 locus were associated with plasma IGF1 (IGF2 rs680, IGF2 rs1004446 and IGF2 rs3741204) and IGF2 (IGF2 rs1004446, IGF2 rs3741204 and H19 rs217727). In single SNP models, effects of IGF2 rs680 were similar between groups, with higher plasma IGF1 concentrations in individuals with the GG genotype when compared with GA (P=0.016), or combined GA and AA genotypes (P=0.003). SNPs in the IGF2 gene associated with IGF1 or IGF2 were in linkage disequilibrium, hence these associations could reflect other genotype variations within this region or be due to changes in INS-IGF2-H19 methylation previously associated with some of these variants. As IGF1 in early pregnancy promotes placental differentiation and function, lower IGF1 concentrations in pregnant women carrying IGF2 rs680 A alleles may affect placental development and/or risk of pregnancy complications.

First pregnancy events and future breast density: modification by age at first pregnancy and specific VEGF and IGF1R gene variants

Purpose

Pregnancy characteristics have been associated with breast cancer risk, but information is limited on their relationship with breast density. Our objective was to examine the relationship between first pregnancy characteristics and later life breast density, and whether the association is modified by genotype.

Methods

The Marin Women’s Study was initiated to examine breast cancer in a high-incidence mammography population (Marin County, CA). Reproductive characteristics and pregnancy information including pregnancy-induced hypertension (PIH) were self-reported at the time of mammography. Forty-seven candidate single nucleotide polymorphisms were obtained from saliva samples; seven were assessed in relation to PIH and percent fibroglandular volume (%FGV). Breast density assessed as %FGV was measured on full-field digital mammograms by the San Francisco Mammography Registry.

Results

A multivariable regression model including 2,440 parous women showed that PIH during first pregnancy was associated with a statistically significant decrease in %FGV (b = −0.31, 95 % CI −0.52, −0.11), while each month of breast-feeding after first birth was associated with a statistically significant increase in %FGV (b = 0.01, 95 % CI 0.003, 0.02). PIH and breast-feeding associations with %FGV were modified by age at first birth. In a subsample of 1,240 women, there was evidence of modification in the association between PIH and %FGV by specific vascular endothelial growth factor (VEGF) (rs3025039) and insulin growth factor receptor-1 (IGFR1) (rs2016347) gene variants.

Conclusion

These findings suggest that first pregnancy characteristics may exert an influence on extent of breast density later in life and that this influence may vary depending on inherited IGFR1 and VEGF genotypes.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-014-0386-2) contains supplementary material, which is available to authorized users.

New genetic variants improve personalized breast cancer diagnosis

Recent large-scale genome-wide association studies (GWAS) have identified a number of new genetic variants associated with breast cancer. However, the degree to which these genetic variants improve breast cancer diagnosis in concert with mammography remains unknown. We conducted a case-control study and collected mammography features and 77 genetic variants which reflect the state of the art GWAS findings on breast cancer. A naïve Bayes model was developed on the mammography features and these genetic variants. We observed that the incorporation of the genetic variants significantly improved breast cancer diagnosis based on mammographic findings.

Genetic variants improve breast cancer risk prediction on mammograms

Several recent genome-wide association studies have identified genetic variants associated with breast cancer. However, how much these genetic variants may help advance breast cancer risk prediction based on other clinical features, like mammographic findings, is unknown. We conducted a retrospective case-control study, collecting mammographic findings and high-frequency/low-penetrance genetic variants from an existing personalized medicine data repository. A Bayesian network was developed using Tree Augmented Naive Bayes (TAN) by training on the mammographic findings, with and without the 22 genetic variants collected. We analyzed the predictive performance using the area under the ROC curve, and found that the genetic variants significantly improved breast cancer risk prediction on mammograms. We also identified the interaction effect between the genetic variants and collected mammographic findings in an attempt to link genotype to mammographic phenotype to better understand disease patterns, mechanisms, and/or natural history.

Racial differences in the association of insulin-like growth factor pathway and colorectal adenoma risk

PURPOSE

Insulin resistance is believed to play an important role in the link between energy imbalance and colon carcinogenesis. Emerging evidence suggests that there are substantial racial differences in genetic and anthropometric influences on insulin-like growth factors (IGFs); however, few studies have examined racial differences in the associations of IGFs and colorectal adenoma, precursor lesions of colon cancer.

METHODS

We examined the association of circulating levels of IGF-1, IGFBP-3 and IGFBP-1, and SNPs in the IGF-1 receptor (IGF1R), IGF-2 receptor (IGF2R), and insulin receptor genes with risk of adenomas in a sample of 410 incident adenoma cases and 1,070 controls from the Case Transdisciplinary Research on Energetics and Cancer (TREC) Colon Adenomas Study.

RESULTS

Caucasians have higher IGF-1 levels compared to African Americans; mean IGF-1 levels are 119.0 ng/ml (SD = 40.7) and 109.8 ng/ml (SD = 40.8), respectively, among cases (p = 0.02). Mean IGF-1 levels are also higher in Caucasian controls (122.9 ng/ml, SD = 41.2) versus African American controls (106.9, SD = 41.2), p = 0.001. We observed similar differences in IGFBP3 levels by race. Logistic regression models revealed a statistically significant association of IGF-1 with colorectal adenoma in African Americans only, with adjusted odds ratios (ORs) of 1.68 (95 % CI 1.06-2.68) and 1.68 (95 % CI 1.05-2.71), respectively, for the second and third tertiles as compared to the first tertile. One SNP (rs496601) in IGF1R was associated with adenomas in Caucasians only; the per allele adjusted OR is 0.73 (95 % CI 0.57-0.93). Similarly, one IGF2R SNP (rs3777404) was statistically significant in Caucasians; adjusted per allele OR is 1.53 (95 % CI 1.10-2.14).

CONCLUSION

Our results suggest racial differences in the associations of IGF pathway biomarkers and inherited genetic variance in the IGF pathway with risk of adenomas that warrant further study.

Circulating concentrations of insulin-like growth factor-I, insulin-like growth factor-binding protein-3, genetic polymorphisms and mammographic density in premenopausal Mexican women: results from the ESMaestras cohort

The insulin-like growth factor (IGF) axis plays an essential role in the development of the mammary gland. High circulating levels of IGF-I and of its major binding protein IGFBP3 have been related with increased mammographic density in Caucasian premenopausal women. Some common single nucleotide polymorphisms (SNPs) in genes of the IGF pathway have also been suggested to play a role in mammographic density. We conducted a cross-sectional study nested within the large Mexican ESMaestras cohort to investigate the relation between circulating levels of IGF-I, IGFBP-3, the IGF-I/IGFBP-3 ratio, five common SNPs in the IGF-1, IGFBP-3 and IGF-1R genes and mammographic density in 593 premenopausal Mexican women. Mean age at mammogram was 43.1 (standard deviation, SD = 3.7) years, and average body mass index (BMI) at recruitment was 28.5 kg/m(2). Mean percent mammographic density was 36.5% (SD: 17.1), with mean dense tissue area of 48.3 (SD: 33.3) cm(2) . Mean IGF-I and IGFBP-3 concentrations were 15.33 (SD: 5.52) nmol/l and 114.96 (SD: 21.34) nmol/l, respectively. No significant associations were seen between percent density and biomarker concentrations, but women with higher IGF-I and IGF-I/IGFBP-3 concentrations had lower absolute dense (p(trend) = 0.03 and 0.09, respectively) and nondense tissue areas (p(trend) < 0.001 for both parameters). However, these associations were null after adjustment by BMI. SNPs in specific genes were associated with circulating levels of growth factors, but not with mammographic density features. These results do not support the hypothesis of a strong association between circulating levels of growth hormones and mammographic density in Mexican premenopausal women.

Variation in inflammatory cytokine/growth-factor genes and mammographic density in premenopausal women aged 50-55

Background

Mammographic density (MD) has been found to be an independent risk factor for breast cancer. Although data from twin studies suggest that MD has a strong genetic component, the exact genes involved remain to be identified. Alterations in stromal composition and the number of epithelial cells are the most predominant histopathological determinants of mammographic density. Interactions between the breast stroma and epithelium are critically important in the maturation and development of the mammary gland and the cross-talk between these cells are mediated by paracrine growth factors and cytokines. The potential impact of genetic variation in growth factors and cytokines on MD is largely unknown.

Methods

We investigated the association between 89 single nucleotide polymorphisms (SNPs) in 7 cytokine/growth-factor genes (FGFR2, IGFBP1, IGFBP3, TGFB1, TNF, VEGF, IL6) and percent MD in 301 premenopausal women (aged 50 to 55 years) participating in the Norwegian Breast Cancer Screening Program. We evaluated the suggestive associations in 216 premenopausal Singapore Chinese Women of the same age.

Results

We found statistically significant associations between 9 tagging SNPs in the IL6 gene and MD in Norwegian women; the effect ranged from 3–5% in MD per variant allele (p-values = 0.02 to 0.0002). One SNP in the IL6 (rs10242595) significantly influenced MD in Singapore Chinese women.

Conclusion

Genetic variations in IL6 may be associated with MD and therefore may be an indicator of breast cancer risk in premenopausal women.

Maternal transmission of a humanised Igf2r allele results in an Igf2 dependent hypomorphic and non-viable growth phenotype

The cation independent mannose 6-phosphate/insulin-like growth factor 2 receptor (IGF2R) functions in the transportation and regulation of insulin-like growth factor 2 (IGF2) and mannose 6-phosphate modified proteins. The relative and specific titration of IGF2 by high affinity binding of IGF2R represents a mechanism that supports the parental conflict theory of genomic imprinting. Imprinting of Igf2 (paternal allele expressed) and Igf2r (maternal allele expressed) arose to regulate the relative supply of both proteins. Experiments in the mouse have established that loss of the maternal allele of Igf2r results in disproportionate growth and peri-natal lethality. In order to systematically investigate the consequences of loss of function and of hypomorphic alleles of Igf2r on growth functions, we introduced a conditional human IGF2R exon 3–48 cDNA into the intron 2 region of murine Igf2r. Here we show that the knock-in construct resulted in over-growth when the humanised Igf2r allele was maternally transmitted, a phenotype that was rescued by either paternal transmission of the humanised allele, expression of a wild-type paternal allele or loss of function of Igf2. We also show that expression of IGF2R protein was reduced to less than 50% overall in tissues previously known to be Igf2 growth dependent. This occurred despite the detection of mouse derived peptides, suggesting that trans-splicing of the knock-in human cDNA with the endogenous maternal mouse Igf2r allele. The phenotype following maternal transmission of the humanised allele resulted in overgrowth of the embryo, heart and placenta with partial peri-natal lethality, suggesting that further generation of hypomorphic Igf2r alleles are likely to be at the borderline of maintaining Igf2 dependent viability.

Insulin-like growth factor axis gene polymorphisms modify risk of pancreatic cancer

OBJECTIVE

Insulin-like growth factor (IGF)-axis genes plays a critical role in cancer development and progression via their impact on the RAS/MAPK/ERK and PI3K/AKT/mTOR signaling pathways. We hypothesized that IGF-axis genetic variants modify individual susceptibility to pancreatic cancer.

METHODS

We retrospectively genotyped 41 single-nucleotide polymorphisms of 10 IGF-axis genes (IGF1, IGF2, IGF1R, IGF2R, IGFBP1, IGFBP3, IGFBP5, IRS1, IRS2, and IRS4) in 706 pancreatic cancer patients and 706 cancer-free controls using Sequenom and TaqMan technology. The association between genotype and pancreatic cancer risk was evaluated using multivariate logistic regression. A P value ≤.007 at a false discovery rate of 10% was set as the significance level.

RESULTS

We observed that the IGF1 *10212C>A and Ex4+2776G>A and IGF1R IVS2-70184A>G and IVS2+46329T>C variant genotypes were significantly associated with decreased pancreatic cancer risk (odds ratio [OR] range, 0.60-0.75) and that IGFBP1 Ex4+111A>G (I253M) was significantly associated with increased pancreatic cancer risk (OR=1.46) after adjusted for other risk factors and multiple comparisons (P≤.007). IGF2R and IGFBP3 variant haplotypes were associated with increased and decreased pancreatic cancer risk, respectively (P<.001). We also observed a weak interaction of the IGF1R IVS2+46329T>C and IGF2R Ex45+11C>T (L2222L) genotypes with diabetes (P(interaction)=.05) and interaction of IGF2R and IRS1 genotypes with alcohol consumption (P(interaction)=.03 and .019, respectively) on increased pancreatic cancer risk.

CONCLUSION

These findings support our hypothesis that polymorphic variants of IGF-axis genes act alone or jointly with other risk factors to affect susceptibility to pancreatic 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.

Polymorphisms of insulin-like growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) contribute to pathologic progression in childhood IgA nephropathy

Previous studies have suggested that insulin-like growth factor-1 (IGF-1) signaling might play an important role in renal fibrosis and regulation of the proliferation of mesangial cells and podocytes. We conducted the present study to investigate association between single nucleotide polymorphisms (SNPs) of IGF-1 (IGF-1) and IGF-1 receptor (IGF-1R) genes and childhood immunoglobulin (Ig) A nephropathy (IgAN). We analyzed five SNPs of IGF-1 and IGF-1R in 188 pediatric IgAN patients and in 263 healthy controls. We compared variations in SNPs in several sets of IgAN subgroups that were designated based on the presence of nephrotic range proteinuria (>40 mg/m2 per h), podocyte foot process effacement, and pathological progression. Genotyping of IgAN patients and controls revealed differences in IGF-1R rs2229765. Moreover, the rs2195239, rs978458, and rs1520220 SNPs of IGF-1 showed significant association with pathological progression. Thus, in the present study, we observed associations between the IGF-1/1R pathway, susceptibility to IgAN, and the pathologic progression of IgAN.

A randomized, placebo-controlled trial (NCIC CTG MAP.2) examining the effects of exemestane on mammographic breast density, bone density, markers of bone metabolism and serum lipid levels in postmenopausal women

We hypothesized that exemestane (EXE) would reduce mammographic breast density and have unique effects on biomarkers of bone and lipid metabolism. Healthy postmenopausal women were randomized to EXE (25 mg daily) or placebo (PLAC) for 12 months and followed for a total of 24 months. The primary endpoint was change in percent breast density (PD) between the baseline and 12-month mammograms and secondary endpoints were changes in serum lipid levels, bone biomarkers, and bone mineral density (BMD). Ninety-eight women were randomized (49 to EXE; 49 to PLAC) and 65 had PD data at baseline and 12 months. Among women treated with EXE, PD was not significantly changed from baseline at 6, 12, or 24 months and was not different from PLAC. EXE was associated with significant percentage increase from baseline in N-telopeptide at 12 months compared with PLAC. No differences in percent change from baseline in BMD (lumbar spine and femoral neck) were observed between EXE and PLAC at either 12 or 24 months. Patients on EXE had a significantly larger percent decrease in total cholesterol than in the PLAC arm at 6 months and in HDL cholesterol at 3, 6, and 12 months. No significant differences in percent change in LDL or triglycerides were noted at any time point between the two treatment arms. EXE administered for 1 year to healthy postmenopausal women did not result in significant changes in mammographic density. A reversible increase in the bone resorption marker N-telopeptide without significant change in bone specific alkaline phosphatase or BMD during the 12 months treatment period and 1 year later was noted. Changes in lipid parameters on this trial were modest and reversible.