Polymorphic CA repeats in the IGF-I gene and breast cancer

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

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.

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.

Obesity and Breast Cancer: Molecular Interconnections and Potential Clinical Applications

Obesity is an important risk factor for breast cancer (BC) in postmenopausal women; interlinked molecular mechanisms might be involved in the pathogenesis. Increased levels of estrogens due to aromatization of the adipose tissue, inflammatory cytokines such as tumor necrosis factor-α, interleukin-6, and prostaglandin E2, insulin resistance and hyperactivation of insulin-like growth factors pathways, adipokines, and oxidative stress are all abnormally regulated in obese women and contribute to cancerogenesis. These molecular factors interfere with intracellular signaling in the mitogen-activated protein kinase and phosphatydilinositol-3-phosphate/mammalian target of rapamycin (mTOR) pathways, which regulate the progression of the cell cycle, apoptosis, and protein synthesis. In this context, structural defects of typical genes related to both BC and obesity, such as leptin, leptin receptor, serum paraoxonase/arylesterase 1, the fat mass and obesity-associated gene and melanocortin receptor 4, have been associated with a high or low risk of BC development. The early detection of these gene alterations might be useful as risk predictors in obese women, and targeting these pathways involved in the BC pathogenesis in obese women is a potential therapeutic tool. In particular, mTOR pathway deregulation concurs in both obesity and BC, and inhibition of this might disrupt the molecular interlinks in a similar manner to that of metformin, which exerts definite anticancer activity and is currently used as an antidiabetic drug with a weight-reducing property. The identification of both genetic and pharmacological implications on the prevention and management of BC is the ultimate aim of these studies.

IMPLICATIONS FOR PRACTICE

Obese women are at risk of breast cancer, but clinicians lack concrete tools for the prevention or early diagnosis of this risk. The present study, starting from the biology and the molecular defects characterizing both obesity and breast cancer, analyzed the potential molecules and genetic defects whose early identification could delineate a risk profile. Three steps are proposed that are potentially achievable in the clinical assessment of obese women, namely the evaluation of altered levels of serum molecules, the identification of genetic polymorphisms, and the study of the transcriptomic profile of premalignant lesions. Finally, the therapeutic implications of this molecular assessment were evaluated.

Role of IGF1R in Breast Cancer Subtypes, Stemness, and Lineage Differentiation

Insulin-like growth factor (IGF) signaling is fundamental for growth and survival. A large body of evidence (laboratory, epidemiological, and clinical) implicates the exploitation of this pathway in cancer. Up to 50% of breast tumors express the activated form of the type 1 insulin-like growth factor receptor (IGF1R). Breast cancers are categorized into subtypes based upon hormone and ERRB2 receptor expression and/or gene expression profiling. Even though IGF1R influences tumorigenic phenotypes and drug resistance across all breast cancer subtypes, it has specific expression and function in each. In some subtypes, IGF1R levels correlate with a favorable prognosis, while in others it is associated with recurrence and poor prognosis, suggesting different actions based upon cellular and molecular contexts. In this review, we examine IGF1R expression and function as it relates to breast cancer subtype and therapy-acquired resistance. Additionally, we discuss the role of IGF1R in stem cell maintenance and lineage differentiation and how these cell fate influences may alter the differentiation potential and cellular composition of breast tumors.

Novel single nucleotide polymorphisms of the insulin-like growth factor-I gene and their associations with growth traits in common carp (Cyprinus carpio L.)

Insulin-like growth factor-I (IGF-I) plays an important role in the growth and development of vertebrates. To study polymorphisms of IGF-I, we screened a total of 4555 bp of genomic sequences in four exons and partial introns for the discovery of single nucleotide polymorphism (SNP) in common carp (Cyprinus carpio). Three SNPs (g.3759T>G, g.7627T>A and g.7722T>C) in intron 2 and a nonsynonymous SNP (g.7892C>T) in exon 3 were identified in a pilot population including random parents and their progenies. 289 progenies were further genotyped for studying possible associations between genotypes or combined genotypes and growth traits. The results showed that the locus g.7627T>A was significantly associated with body weight and body length, and fish with genotype AA had a mean body weight 5.9% higher than those with genotype TT. No significant associations were observed between genotypes of other loci and growth traits. However, when both g.7627T>A and g.7722T>C were considered, the combined genotype TT/TT was extremely associated with the lowest values of body length and body weight and the highest K value in comparison with other diplotypes (p < 0.01). These results suggest that genotype AA at g.7627T>A and its combined genotypes with alleles from another locus have positive effects on growth traits, which would be a candidate molecular marker for further studies in marker-assisted selection in common carp.

Role of IGF1-(CA)19 promoter microsatellite in the clinical presentation of acromegaly

BACKGROUND

A highly polymorphic Cytosine-Adenosine (CA) repeat sequence microsatellite has been identified in the promoter region of IGF1 gene. Several studies investigated the relationship between IGF1-(CA)n polymorphism and IGF1 levels, with conflicting results. Aim of this study was to investigate the influence of this polymorphism on clinical and biochemical characteristics of acromegalic patients.

METHODS

Eighty-eight acromegalic patients and 104 normal subjects were included in the study. Blood DNA was extracted and analysed by microsatellite technique using capillary electrophoresis. Patients and controls were subdivided in 19/19 [homozygous for the (CA)19 allele], 19/X [heterozygous for the (CA)19 allele] and X/X (any other genotype).

RESULTS

The genotype frequency was significantly different between patients and controls, the proportion of 19/19 being lower (28·4% vs. 50·0%) and 19/X and X/X higher in acromegalic patients than in controls (P = 0·004). There were no significant differences in age, gender, basal and nadir GH, IGF1-SDS, tumour size, metabolic parameters, outcome and treatment among the three groups. The different frequency of genotypes in acromegalic patients vs. controls, as well as the lack of relationship between IGF1-(CA)n polymorphism and clinical and biochemical data in acromegalic patients, was confirmed using an additional alternative genotyping considering (CA)19 and (CA)20 homozygotes and heterozygotes vs. alleles with more than 19 of 20 repeats or less.

CONCLUSIONS

Our results do not support the hypothesis that IGF-(CA)n alleles may have a significant role in determining clinical, biochemical and outcome of patients with acromegaly. The possible role of IGF1 polymorphism on susceptibility to acromegaly remains to be investigated.

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.

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.

Functional polymorphisms in the insulin-like binding protein-3 gene may modulate susceptibility to differentiated thyroid carcinoma in Caucasian Americans

The insulin-like growth factor (IGF) pathway is believed to play a pivotal role in thyroid carcinogenesis. Polymorphisms of IGF-1 and IGF binding protein-3 (IGFBP-3) have been associated with modulation of risk for the emergence of assorted common malignancies, but studies of the influence of such polymorphisms on risk of differentiated thyroid carcinoma (DTC) are lacking. In a case-control study of 173 DTC patients, 101 patients with benign thyroid disease, and 401 controls, an unconditional logistical regression model adjusted for age and sex was applied to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between polymorphisms of IGF-1 and IGFBP-3 and DTC risk. IGFBP-3 rs2132572 GA/AA genotypes were associated with a decreased risk of DTC (adjusted OR = 0.6, 95% CI: 0.4-0.9), particularly multifocal DTC (adjusted OR = 0.3, 95% CI: 0.1-0.7). The association with DTC was more evident in subjects with a first-degree family history of cancer (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction)  = 0.013) and non-drinkers (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction)  = 0.028). A four single nucleotide polymorphism haplotype of IGFBP-3 was associated with a decreased risk of DTC (adjusted OR = 0.7, 95% CI: 0.5-1.0, P = 0.030). Our study suggests that polymorphic IGFBP-3 may be involved in susceptibility to DTC.

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.

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.

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.

IGF(CA)19 and IGFBP-3-202A/C gene polymorphism in patients with acromegaly

OBJECTIVE

We aimed to investigate IGF-1 and IGFBP-3 gene polymorphisms in patients with acromegaly.

DESIGN

We included 34 patients with acromegaly and 37 healthy subjects to study. At baseline examinations, antropometric measurements were done. Genomic DNA from the patients and controls were prepared. Serum, glucose, insulin, total cholesterol, triglyceride, HDL cholesterol, LDL cholesterol, growth hormone (GH), Insulin-like growth factor I (IGF-I) and IGFBP-3 levels of subjects were analyzed.

RESULTS

The frequency of genotype IGF-1(CA)19 and IGFBP3-202 A/C gene was significantly different between control and patients. In acromegalic patients, a significant difference in the serum IGF-1 levels and LDL cholesterol levels among the three IGF(CA)19 genotype. LDL levels were positively correlated with IGF-1. Subjects having >194 bp genotype had higher IGF-1 and LDL cholesterol levels. We observed that the patients with 194 bp genotype have more invasive and bigger tumors and they require adjunctive therapies. Clinical characteristics among the three IGFBP3-202 A/C genotype, AA, AC and CC, did not display any significant difference.

CONCLUSIONS

In our study, 194 bp allele (20 CA repeats) of the IGF-I promoter have higher circulating IGF-I levels than others. We have found that the patients with 194 bp genotype are the resistant patients with active disease and they required high dose medication. We think this study may help to define the patients, who are resistant to drug therapy, and possible cardiovascular disease.

A population-based study of IGF axis polymorphisms and the esophageal inflammation, metaplasia, adenocarcinoma sequence

BACKGROUND & AIMS

Insulin-like growth factor (IGF) axis plays a key role in cell development, proliferation, and survival and is implicated in the etiology of several cancers. Few studies have examined the relationship between genetic variation of this axis and esophageal adenocarcinoma (EAC) or its precursors.

METHODS

In a population-based case-control study, we investigated the association of common polymorphisms of IGF-1, IGF-2, IGF-1 receptor, IGF binding protein-3, growth hormones (GH) 1 and GH2, and GH receptor with reflux esophagitis (RE), Barrett esophagus (BE), and EAC. Two hundred and thirty RE, 224 BE, 227 EAC cases, and 260 controls were studied. Gene polymorphisms were identified using publicly available online resources; 102 IGF axis tag and putatively functional single-nucleotide polymorphisms (SNPs) were analyzed using MassARRAY iPLEX and Taqman assays. Results were analyzed using Haploview.

RESULTS

Three polymorphisms were disease-associated. IGF1 SNP rs6214 was associated with BE (adjusted P = .039). Using GG genotype as reference, odds ratio for BE in AA (wild-type) was 0.43 (95% confidence interval [CI], 0.24-0.75). GH receptor SNP rs6898743 was associated with EAC (adjusted P = .0112). With GG as reference, odds ratio for EAC in CC (wild-type) genotype was 0.42 (95% CI, 0.23-0.76). IGF1 (CA)(17) 185-bp allele was associated with RE (adjusted P = .0116). Using IGF1(non17) as reference, odds ratio for RE in IGF1(17) carriers was 7.29 (95% CI, 1.57-46.7).

CONCLUSIONS

In this study, 3 polymorphisms of IGF genes were associated with EAC or its precursors. These polymorphisms may be markers of disease risk; independent validation of our findings is required. These results suggest the IGF pathway is involved in EAC development.

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.

IGF and insulin receptor signaling in breast cancer

Major molecular abnormalities in breast cancer include the deregulation of several components of the IGF system. It is well recognized that the epithelial breast cancer cells commonly overexpress the IGF-I receptor while IGF-II is expressed by the tumor stroma. In view to the fact that the IGF-IR has mitogenic, pro-invasive and anti-apoptotic effects and mediates resistance to a variety of anti-cancer therapies, breast cancer is expected to be a candidate to therapeutic approaches aimed to inhibit the IGF-IR. However, there is increasing awareness that IGF system in cancer undergoes signal diversification by various mechanisms. One of these mechanisms is the aberrant expression of insulin receptor (IR) isoform A (IR-A), which is a high affinity receptor for both insulin and IGF-II, in breast cancer cells. Moreover, overexpression of both IGF-IR and IR-A in breast cancer cells, leads to overexpression of hybrid IR/IGF-IR receptors (HRs) as well. Upon binding to IGF-II, both IR-A and HRs may activate unique signaling patterns, which predominantly mediate proliferative effects. A better understanding of IGF system signal diversification in breast cancer has important implications for cancer prevention measures, which should include control of insulin resistance and associated hyperinsulinemia. Moreover, in addition to the IGF-IR, both IR-A and HRs should be also considered as molecular targets for anti-cancer therapies.

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.

The emerging role of the insulin-like growth factor pathway as a therapeutic target in cancer

The insulin-like growth factor signaling pathway is important in many human cancers based on data from experimental models as well as epidemiological studies. Important therapies targeted at this pathway have been or are being developed, including monoclonal antibodies to the insulin-like growth factor-I receptor and small molecule inhibitors of the tyrosine kinase function of this receptor. These investigational therapies are now being studied in clinical trials. Emerging data from phase I trials are encouraging regarding the safety of the monoclonal antibodies. In this manuscript, the rationale for targeting the insulin-like growth factor system is reviewed in addition to a summary of the available clinical trial data.

Insulin-like growth factor I (CA) repeats are associated with higher melanoma's Breslow index but not associated with the presence of the melanoma. A pilot study

BACKGROUND

IGF-I-(CA) repeats have been previously analysed in few types of cancer and the results, although discordant in different studies, showed possible associations between cancer and IGF-I(CA)(19) repeats. Aim of this pilot study was to detect a possible association between some of the IGF-I(CA) repeats and the presence of malignant melanoma and its Breslow index.

METHODS

Two hundred patients affected with cutaneous malignant melanoma and 100 control healthy subjects were analysed for IGF-I(CA) repeats by fragment analysis sequencing and, partially, confirmed by direct sequencing.

RESULTS

A significant association of IGF-I(CA)(19) repeats was observed with melanoma higher Breslow indices (P<0.001), while no association between melanoma patients and the different genotypes of IGF-I(CA) was found. The above mentioned association was confirmed after Bonferroni's correction for multiple comparisons and also by logistic regression analysis adjusted for age, sex and BMI variables. A slight, significant difference (P=0.03) was observed for serum IGF-I values in IGF-I(CA)(19)-positive or IGF-I(CA)(19)-negative subjects.

DISCUSSION

The association observed for IGF-I(CA)(19) and malignant melanoma is in keeping with similar results obtained in prostate or breast cancers, suggesting that this type of repeat may be directly or indirectly important in controlling cancer induction and its severity.

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.

Mechanisms of disease: signaling of the insulin-like growth factor 1 receptor pathway--therapeutic perspectives in cancer

The insulin-like growth factor 1 (IGF1) signaling pathway is implicated in the development of cancer. High levels of circulating IGF1 and certain genetic polymorphisms of IGF1 and IGFBP3 are associated with an increased risk of several common cancers. The IGF1 receptor (IGF1R) has been shown to be expressed in a wide range of tumors, and IGF1R signaling is crucial for tumor transformation and the survival of malignant cells. Several monoclonal antibodies and small-molecule inhibitors have been tested in preclinical studies and early-phase clinical studies. IGF1R signaling interferes with numerous growth factors and receptors such as VEGF and EGFR. In the experimental system, IGF1R signaling has been found to correlate with resistance to therapies based on the inhibition of EGFR and HER2. This Review highlights the most relevant studies in this exciting area of research, focusing in particular on the role of IGF1R in resistance to other receptor-targeted therapies for cancer.

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.

Diabetic retinopathy and IGF-1 gene polymorphic cytosine-adenine repeats in a Southern Indian cohort

BACKGROUND/AIMS

Growth factors have been implicated in the pathogenesis of diabetic retinopathy (DR). IGF-1 is known to trigger a critical cascade of molecular events that initiate retinal angiogenesis. Increased vitreous IGF-1 levels have been correlated with the severity of ischemia-associated diabetic retinal neovascularization. In the present study, a cytosine-adenine (CA)(n) repeat in the promoter of the IGF-1 gene is studied for association with DR.

METHODS

A total of 127 patients with retinopathy (cases: DR+) and 81 patients without retinopathy (controls: DR-) who had type 2 diabetes were recruited for the study. Patients underwent detailed clinical examination and DR was graded based on stereoscopic digital fundus photographs. Frequencies of alleles and genotypes between the two groups were analyzed for significance using relevant statistical tests. (CA)(17) and (CA)(18) repeats were the more frequent alleles.

RESULTS

The frequency of the 18-repeat genotype was significantly higher in DR+ patients when compared to DR- patients and found to confer a 2.4 times (95% CI: 1.2-5.0) and 2.8 times (95% CI: 1.1-7.5) higher risk for developing DR and proliferative DR, respectively, when compared to <18-repeat genotypes.

CONCLUSIONS

Our study suggests that the 18-repeat genotype is a susceptibility genotype for DR and its clinical severity in a Southern Indian cohort.

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.

An IGF-I gene polymorphism modifies the risk of developing persistent microalbuminuria in type 1 diabetes

OBJECTIVE

Derangements of the GH-IGF-I axis have been associated with microalbuminuria (MA) in type 1 diabetes. The aim of this study was to investigate whether an IGF-I gene promoter polymorphism influenced the development of persistent MA in type 1 diabetes.

DESIGN

A prospective follow-up study of a cohort of 277 patients with newly diagnosed type 1 diabetes consecutively enrolled between September 1979 and August 1984.

METHODS

Urinary albumin excretion rate over 24 h was measured in each patient at least once a year. Persistent MA was defined as a urinary albumin excretion rate between 30 and 300 mg/24 h.

RESULTS

During a median follow-up of 18.0 years (range 1.0-21.5), 79 of 277 patients developed persistent MA. IGF-I gene genotype was available for 216 subjects; in 73% of the subjects, the wild-type genotype of this IGF-I gene polymorphism was present, while 27% had the variant type. At baseline, there were no differences in IGF-I levels and HbA(1c) values between subjects with the wild type and subjects with variant type. By Kaplan-Meier analysis, subjects with the variant type of this polymorphism had during follow-up a higher risk of development of MA compared subjects with the wild type (P = 0.03).

CONCLUSIONS

Subjects with the variant type of an IGF-I gene polymorphism had a significantly increased risk of developing MA. This risk was not mediated through changes in circulating IGF-I levels. Our study suggests that in type 1 diabetes, this IGF-I gene polymorphism is a risk factor of MA.

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.

Impact of IGF-I and CYP19 gene polymorphisms on the survival of patients with metastatic prostate cancer

PURPOSE

The prognosis of metastatic prostate cancer significantly differs among individuals. While various clinical and biochemical prognostic factors for survival have been suggested, the progression and response to treatment of those patients may also be defined by host genetic factors. In this study, we evaluated genetic polymorphisms as prognostic predictors of metastatic prostate cancer.

PATIENTS AND METHODS

One hundred eleven prostate cancer patients with bone metastasis at the diagnosis were enrolled in this study. Thirteen genetic polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism or an automated sequencer with a genotyping software.

RESULTS

Among the polymorphisms, the long allele (over 18 [CA] repeats) of insulin-like growth factor-I (IGF-I) and the long allele (over seven [TTTA] repeats) of cytochrome P450 (CYP) 19 were significantly associated with a worse cancer-specific survival (P = .016 and .025 by logrank test, respectively). The presence of the long allele of either the IGF-I or CYP19 polymorphisms was an independent risk factor for death (P = .019 or .026, respectively). Furthermore, the presence of the long allele of both the IGF-I and CYP19 polymorphisms was a stronger predictor for survival (P = .001).

CONCLUSION

The prognosis of metastatic prostate cancer patients is suggested to be influenced by intrinsic genetic factors. The IGF-I (CA) repeat and CYP19 (TTTA) repeat polymorphisms may be novel predictors in prostate cancer patients with bone metastasis at the diagnosis.

Polymorphisms of genes coding for insulin-like growth factor 1 and its major binding proteins, circulating levels of IGF-I and IGFBP-3 and breast cancer risk: results from the EPIC study

Insulin-like growth factor I (IGF-I) stimulates cell proliferation and can enhance the development of tumours in different organs. Epidemiological studies have shown that an elevated level of circulating IGF-I is associated with increased risk of breast cancer, as well as of other cancers. Most of circulating IGF-I is bound to an acid-labile subunit and to one of six insulin-like growth factor binding proteins (IGFBPs), among which the most important are IGFBP-3 and IGFBP-1. Polymorphisms of the IGF1 gene and of genes encoding for the major IGF-I carriers may predict circulating levels of IGF-I and have an impact on cancer risk. We tested this hypothesis with a case–control study of 807 breast cancer patients and 1588 matched control subjects, nested within the European Prospective Investigation into Cancer and Nutrition. We genotyped 23 common single nucleotide polymorphisms in IGF1, IGFBP1, IGFBP3 and IGFALS, and measured serum levels of IGF-I and IGFBP-3 in samples of cases and controls. We found a weak but significant association of polymorphisms at the 5′ end of the IGF1 gene with breast cancer risk, particularly among women younger than 55 years, and a strong association of polymorphisms located in the 5′ end of IGFBP3 with circulating levels of IGFBP-3, which confirms previous findings. Common genetic variation in these candidate genes does not play a major role in altering breast cancer risk in Caucasians.

IGF1 gene polymorphism and risk for hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder caused by germline mutations in DNA mismatch repair (MMR) genes. Insulin-like growth factor-I (IGF-I) is involved in colorectal carcinogenesis, and elevated plasma IGF-I levels are associated with sporadic colorectal cancer (CRC) risk. We investigated the relationship between IGF1 promoter cytosine-adenine (CA) dinucleotide-repeat polymorphism length and CRC risk in 121 MMR gene mutation carriers using Cox regression and Kaplan-Meier analysis. All statistical tests were two-sided. Time to onset for CRC increased for each decrease in CA-repeat number (median = 19 repeats, range = 12-22 repeats; hazard ratio [HR] = 1.17, 95% confidence interval [CI] = 1.05 to 1.31; P = .006). Patients carrying a CA(< or = 17) repeat allele had a statistically significantly higher CRC risk (HR = 2.36; 95% CI = 1.28 to 4.36; P = .006) than all others and were younger at onset (44 years versus 56.5 years; P = .023). These findings indicate a statistically significant association between shorter IGF1 CA-repeat lengths and increased risk for CRC in HNPCC. This is the first report, to our knowledge, to show that IGF1 variant genotypes modify risk of a hereditary form of cancer.

Insulin-like growth factor polymorphisms and colorectal cancer risk

Several modifiable lifestyle factors, such as physical activity, obesity, and postmenopausal hormone use, have been associated with colorectal cancer risk. It has been hypothesized that some or all of these factors may mediate their effects through alterations in insulin-like growth factor-1 (IGF-1) and its binding proteins (IGFBP). To evaluate the role of IGFs in colorectal cancer, we examined the relationship of two common genetic polymorphisms in IGF-1 (a cytosine-adenosine dinucleotide repeat) and IGFBP-3 (a G --> C single nucleotide polymorphism) with colorectal cancer risk, as well as their potential modification by physical activity, body mass index (BMI), and postmenopausal hormone use. Subjects included 782 male and female colorectal cancer cases diagnosed between 1998 and 2002 and reported to the statewide registry in the metropolitan Seattle area, and 503 age- and sex-matched cancer-free population controls. Colorectal cancer was modestly associated with having an IGF-1 genotype other than homozygous for 19 repeats (odds ratio, 1.3; 95% confidence interval, 1.0-1.6) and having the GG IGFBP-3 genotype (odds ratio, 1.3; 95% confidence interval, 1.0-1.8). There was evidence that IGF-1 genotype modified the relationship between BMI and colorectal cancer among women, such that high BMI increased risk of colorectal cancer only among those with the 19/19 genotype (P(interaction) = 0.02). IGFBP-3 genotype was also a significant effect modifier of the relationship between risk factors and colorectal cancer: The positive association between BMI and colorectal cancer was observed only among men (P(interaction) < 0.01) and women (P(interaction) = 0.06) with the GG genotype; the inverse association between postmenopausal hormone use and colorectal cancer was observed only among women with the GG genotype (P = 0.01) and the inverse association between physical activity and colorectal cancer was observed only among men who carried the C allele (P < 0.01). The current study provides some support for a role of IGFs in colorectal cancer etiology, particularly in mediating the relationship of common risk factors (physical activity, BMI, and postmenopausal hormone use).

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

Insulin-like growth factor I (IGF-I) is an important regulator of growth and differentiation and is a potent mitogen for human breast cancer cells. Recent investigations suggest an association between cytosine-adenine dinucleotide (CA)n repeat polymorphisms of the IGF1 gene and IGF-I levels and further evidence indicates that genotype may influence breast cancer risk. We assessed the relation between IGF1 (CA)n repeats and breast cancer, and evaluated modification of genotype effects according to traditional breast cancer risk factors in 1028 breast cancer cases and 1086 controls. An increased risk of breast cancer was seen for genotypes that included alleles with fewer than (CA)19 repeats when compared to (CA)19 repeat carriers, an association that was particularly strong among premenopausal women [odds ratio (OR)=3.31; 95% confidence interval (CI)=1.47, 7.48]. No significant association was observed between an IGF1 genotype with no (CA)19 repeat compared to (CA)19 repeat genotypes in either pre- or postmenopausal women overall. However, when traditional breast cancer risk factors were considered, premenopausal women with genotypes that lacked a (CA)19 repeat had a nearly 60% increased risk of breast cancer among those who had ever used hormonal birth control, while never users had a significantly reduced risk (Pinteraction=0.01). Among postmenopausal women, those with genotypes lacking a (CA)19 repeat allele had significantly increased breast cancer risk among subjects with a lower than median body mass index (BMI) (OR=1.77 95% CI=1.09, 2.87), while no association for IGF1 genotype was seen among women with a higher than median BMI (Pinteraction=0.04). Our results demonstrate a role for alleles with fewer than (CA)19 repeats as a risk factor for breast cancer and also suggest that several traditional breast cancer risk factors modify the association of the IGF1 (CA)19 repeat genotype.

Polymorphisms in the IGF-1 and IGFBP3 promoter and the risk of breast cancer

Binding of IGF-1 to the type I IGF receptor starts a signalling cascade that plays an important role in regulating cell proliferation, differentiation and apoptosis. The interaction between the IGF-1 and its receptor is mainly regulated by a binding protein, IGFBP 3. We studied a CA repeat polymorphism 969 bp upstream of the transcription start site in the IGF-1 gene and an A-202 C polymorphism in the IGFBP 3 gene and tested their association with breast cancer risk using four case-control series with a total of 787 cases and 900 controls. We did not find any association between the breast cancer risk and the IGF-1 repeat length (19 versus non-19) or the IGFBP 3 A-202 C polymorphism in the postmenopausal breast cancer series or in women diagnosed for breast cancer under the age of 50. In the familial breast cancer series we observed a non-significantly increased odds-ratio (OR) in homozygotes for the non-19 alleles of the IGF-1 gene (OR 1.51, 95% CI 0.96-2.39, p=0.07). Similarly, in the familial breast cancer series we detected an increased frequency of the IGFBP 3 -202 C allele carriers (OR 1.50, 95% CI 1.05--2.14, p=0.03). The association was stronger in individuals homozygous for these alleles (OR 3.76, 95% CI 1.44-v-9.81, p=0.006). Thus, the polymorphisms in the IGF-1 and IGFBP 3 genes associated with an increased risk of breast cancer in familial cases carrying the variant alleles.

Dinucleotide repeats negatively modulate the promoter activity of Cyr61 and is unstable in hepatocellular carcinoma patients

Cyr61 is a secreted, cysteine-rich, heparin-binding protein that mediates diverse functions including extracellular matrix formation, differentiation, cell proliferation, adhesion, migration, survival, as well as angiogenesis and tumorigenesis. In this study, we found that Cyr61 gene expression is significantly downregulated in the tumors of hepatocellular carcinoma (HCC) patients. To elucidate its mechanism of gene regulation, we examined the promoter of Cyr61 which contains two long stretches of repeats, each comprising d(CA) dinucleotide repeats downstream of HNF3beta- and ATF-binding sites. We hypothesized that the d(CA) repeats may play an important role in regulating Cyr61 promoter activity and performed promoter reporter assays to examine this. We found that a greater number of d(CA) repeats resulted in significantly lower promoter activity of the Cyr61 gene in the KB3-1 and HepG2 cell lines, but not in the MCF-7 cell line. In addition, the d(CA) repeats, but not other random sequences, were found to be important for Cyr61 promoter activity. We further demonstrate that the ATF- and HNF3beta-binding sites upstream the d(CA) repeats positively and negatively modulate Cyr61 promoter activity, respectively. An examination of the d(CA) dinucleotide patterns in the Cyr61 promoter in HCC patients revealed that approximately 32% of these patients exhibited either loss of heterozygosity or somatic mosaicism in either the tumors, adjacent normal liver tissues or both.

Muscle strength response to strength training is influenced by insulin-like growth factor 1 genotype in older adults

Strength training (ST) is considered an intervention of choice for the prevention and treatment of sarcopenia. Reports in the literature have suggested that the insulin-like growth factor I protein (IGF-I) plays a major role in ST-induced skeletal muscle hypertrophy and strength improvements. A microsatellite repeat in the promoter region of the IGF1 gene has been associated with IGF-I blood levels and phenotypes related to IGF-I in adult men and women. To examine the influence of this polymorphism on muscle hypertrophic and strength responses to ST, we studied 67 Caucasian men and women before and after a 10-wk single-leg knee-extension ST program. One repetition maximum strength, muscle volume via computed tomography, and muscle quality were assessed at baseline and after 10 wk of training. The IGF1 repeat promoter polymorphism and three single-nucleotide polymorphisms were genotyped. For the promoter polymorphism, subjects were grouped as homozygous for the 192 allele, heterozygous, or noncarriers of the 192 allele. After 10 wk of training, 1-repetition maximum, muscle volume, and muscle quality increased significantly for all groups combined ( P < 0.001). However, carriers of the 192 allele gained significantly more strength with ST than noncarriers of the 192 allele ( P = 0.02). There was also a nonsignificant trend for a greater increase in muscle volume in 192 carriers than noncarriers ( P = 0.08). No significant associations were observed for the other polymorphisms studied. Thus these data suggest that the IGF1 promoter polymorphism may influence the strength response to ST. Larger sample sizes should be used in future studies to verify these results.