Identification of upstream stimulatory factor binding sites in the human IGFBP3 promoter and potential implication of adjacent single-nucleotide polymorphisms and responsiveness to insulin

Association between endogenous sex steroid hormones and insulin-like growth factor proteins in US men

PURPOSE

Sex steroid hormone concentrations and insulin-like growth factor (IGF) proteins have been independently associated with risk of cancer, chronic diseases, and mortality. However, studies that evaluated the inter-relation between the sex hormones and IGF pathways have provided mixed results. We examined the association between endogenous sex hormones and sex hormone-binding globulin (SHBG) with IGF-1 and IGF-binding protein 3 (IGFBP-3) in a population-based sample of US men.

METHODS

Data from 1,135 men aged 20 years or older participating in the third National Health and Nutrition Examination Survey (NHANES III) were analyzed. Weighted linear regression was used to estimate geometric means and 95 % confidence intervals for IGF-1 and IGFBP-3 concentrations by sex steroid hormones and SHBG after adjusting for age, race/ethnicity, body mass index, waist circumference, alcohol consumption, cigarette smoking, physical activity, diabetes, and mutually adjusting for other sex hormones and SHBG.

RESULTS

No significant association was observed between sex steroid hormones, SHBG, and IGF-1 concentrations. Total estradiol (% difference in Q5 - Q1 geometric means -9.7 %; P-trend 0.05) and SHBG (% difference -7.3 %; P-trend 0.02) were modestly inversely associated with IGFBP-3. Total testosterone was modestly inversely associated with IGFBP-3 (% difference -6.2 %; P-trend 0.01), but this association disappeared after adjustment for total estradiol and SHBG (% difference 2.6 %; P-trend 0.23). Androstanediol glucuronide was not associated with IGFBP-3.

CONCLUSIONS

These findings suggest that there may be inter-relationships between circulating total estradiol, SHBG, and IGFBP-3 concentrations. Future research may consider these inter-relationships when evaluating potential joint effects of the sex hormones and IGF pathways.

Regulation of IGFBP3 gene expression in short children born small for gestational age

OBJECTIVE

Approximately 6% of newborns at term are small for gestational age (SGA) and present a birth weight and/or length less than -2SD from the mean. SGA infants are at increased risk for perinatal morbidity, associated psychological and/or mental problems, persistent short stature (about 15% of subjects) and metabolic alterations. Insulin-like growth factors (IGFs), their common receptor (IGF1R) and their binding proteins (IGFBPs) play a critical role in fetal and postnatal growth. In these genes common polymorphisms, such as single nucleotide polymorphisms and variable number of tandem repeats, have been investigated with conflicting results with respect to SGA-related outcomes, and the functional role of these gene variants remains to be elucidated.

DESIGN

The study group consisted of 100 pre-pubertal short children born SGA and 94 healthy controls, matched for sex and age, recruited at the Department of Biomedicine of Development Age of the Bari University and at the Paediatric Department of the Messina Hospital. In the present study we analyzed the allelic frequency of the polymorphisms -795 G/A, -667 G/A, -396 C/T in the IGFBP3 in SGA children and their influence on the basal and insulin-stimulated transcriptional activity of the gene.

RESULTS

We found that the polymorphisms -667 G/A and -396 C/T in the IGFBP3 promoter region are capable of having an effect on the transcriptional activity of the gene, although with opposing effects. Interestingly, the -667 G/A polymorphism has a negative impact on the IGFBP3 transcription, while the -396 C/T polymorphism determines an increase of the transcriptional activity of the IGFBP3 gene promoter. Interestingly, we found that the -396 C/T polymorphism correlates with lower birth length in SGA children. Most importantly, while the diminished IGFBP3 transcriptional activity induced by the -667A polymorphism was significantly recovered after insulin administration (p-value<0.05), the increased transcriptional activity caused by the -396T polymorphism was not restored to baseline levels by insulin.

CONCLUSIONS

Altogether our results demonstrated that the -667 G/A and the -396 C/T polymorphisms in IGFBP3 promoter region influence the basal transcriptional activity of the gene.

Common polymorphisms in the GH/IGF-1 axis contribute to growth in extremely tall subjects

CONTEXT/OBJECTIVE

The growth hormone (GH)/insulin-like growth factor-1(IGF-1) axis is the key regulator of somatic growth in humans and its genes are plausible candidates to study the genetics of height variation. Here, we studied polymorphic variation in the GH/IGF-1 axis in the extremely tall Dutch.

METHODS

Case-control study of 166 tall cases with height >2 SDS and 206 controls with normally distributed height <2 SDS. Excluded were subjects with endocrine disorders or growth syndromes. We analyzed genomic DNA at 7 common polymorphisms in the GH-1, GH receptor (GHR), IGF-1 and IGFBP-3 genes.

RESULTS

The association of the GH-1 1663 SNP with tall stature approached statistical significance, with the T-allele more present in the tall (allele frequency (AF): 0.44 vs. 0.36; p=0.084). Moreover, haplotype frequencies at this locus were significantly different between cases and controls, with the GGT haplotype most commonly seen in cases (p=0.01). Allele frequencies of GHR polymorphisms were not different. For the IGF-1 CA-repeat we observed a higher frequency of homozygous 192-bp carriers among tall males compared to control males (AF: 0.62 vs. 0.55; p=0.02). The IGFBP-3 -202 C-allele occurred more frequently in cases than in controls (AF: 0.58 vs. 0.50; p=0.002). Within cases, those carrying one or two copies of the -202 C-allele were significantly taller than AA genotype carriers (AC, p=0.028 and CC, p=0.009). Serum IGFBP-3 levels were highest in AA genotype carriers, the -202 SNP explained 5.8% of the variation.

CONCLUSION

Polymorphic variation in the GH-1, IGF-1 and IGFBP-3 genes is associated with extremely tall stature. In particular, the IGFBP-3 -202 SNP is associated not only with being very tall but also with height variation within the tall.

Wnt signaling exerts an antiproliferative effect on adult cardiac progenitor cells through IGFBP3

RATIONALE

Recent work in animal models and humans has demonstrated the presence of organ-specific progenitor cells required for the regenerative capacity of the adult heart. In response to tissue injury, progenitor cells differentiate into specialized cells, while their numbers are maintained through mechanisms of self-renewal. The molecular cues that dictate the self-renewal of adult progenitor cells in the heart, however, remain unclear.

OBJECTIVE

We investigate the role of canonical Wnt signaling on adult cardiac side population (CSP) cells under physiological and disease conditions.

METHODS AND RESULTS

CSP cells isolated from C57BL/6J mice were used to study the effects of canonical Wnt signaling on their proliferative capacity. The proliferative capacity of CSP cells was also tested after injection of recombinant Wnt3a protein (r-Wnt3a) in the left ventricular free wall. Wnt signaling was found to decrease the proliferation of adult CSP cells, both in vitro and in vivo, through suppression of cell cycle progression. Wnt stimulation exerted its antiproliferative effects through a previously unappreciated activation of insulin-like growth factor binding protein 3 (IGFBP3), which requires intact IGF binding site for its action. Moreover, injection of r-Wnt3a after myocardial infarction in mice showed that Wnt signaling limits CSP cell renewal, blocks endogenous cardiac regeneration and impairs cardiac performance, highlighting the importance of progenitor cells in maintaining tissue function after injury.

CONCLUSIONS

Our study identifies canonical Wnt signaling and the novel downstream mediator, IGFBP3, as key regulators of adult cardiac progenitor self-renewal in physiological and pathological states.

Association between insulin-like growth factor binding protein-3 promoter polymorphism of -1590 C>A and lung cancer susceptibility in a Chinese Han population

Recent studies have identified a negative correlation between serum levels of insulin-like growth factor binding protein-3 (IGFBP-3) and the risk of lung cancer. In this study, polymorphisms present at the -1590 site of the IGFBP-3 promoter were evaluated in relation to lung cancer risk in a Chinese Han population. A total of 248 nonsmall cell lung cancer (NSCLC) cases and 29 small cell lung cancer cases were compared with 252 matched, healthy controls. Polymerase chain reaction-based restriction fragment length polymorphism assays were used to detect polymorphisms present. The A/A genotype and an A allele were both associated with an increased risk of NSCLC after being adjusted for age and gender (adjusted odds ratio = 2.296, 95% confidence interval = 1.133-4.655; and adjusted odds ratio = 1.390, 95% confidence interval = 1.042-1.854, respectively). In conclusion, the A/A genotype and A allele of the IGFBP-3 promoter -1590 site may represent a genetic risk factor for NSCLC, with the A/A genotype being associated with a higher risk for squamous cell carcinoma than adenocarcinoma.

IGFBP1 and IGFBP3 polymorphisms predict circulating IGFBP-3 levels among women from high-risk breast cancer families

The insulin-like growth factor (IGF) pathway has been implicated as risk modifier in premenopausal breast cancer. In this study, associations between single nucleotide polymorphisms (SNPs) and diplotypes in the IGFBP1 and IGFBP3 genes and circulating IGFBP-3 levels, BRCA family status and breast cancer among women from high-risk breast cancer families were investigated. Nine IGFBP1 and IGFBP3 SNPs were genotyped with PCR-based methods in 323 women. Nine IGFBP1 and ten IGFBP3 diplotypes were identified. Plasma IGFBP-3 levels obtained during cycle day 18-23 were available for 231 women, 87 current users of combined oral contraceptives and 144 non-users. IGFBP1 (rs1995051 and rs4988515) and IGFBP3 (rs2471551 and rs2854744) SNPs were associated with circulating IGFBP-3 levels (P < 0.05). IGFBP1 (low) diplotypes were associated with lower IGFBP-3 levels and were more common in BRCA2 families OR 2.05 (95%CI 0.97-4.30). IGFBP3 (high) diplotypes were associated with higher IGFBP-3 levels and were more common in BRCAX families OR 1.68 (95%CI 1.04-2.74). After adjusting the models for BRCA family status, both the BRCA1 and BRCA2 family status (P ≤ 0.006) and the IGFBP1 diplotype GTAC/ACAT (P = 0.004) were associated with lower IGFBP-3 levels. Similarly, both the BRCA1 and BRCA2 family status (P ≤ 0.03) and the IGFBP-3 diplotypes GCA/GCG (P = 0.007) and GCG/CCG (P = 0.002) were significantly associated with lower IGFBP-3 levels, adjusted for age, weight, OC use, and other IGFBP diplotypes. No individual SNP was associated with breast cancer. There were 23 cases of breast cancer and one IGFBP1 diplotype was associated with a decreased risk of breast cancer after age 18 (log rank P=0.05). In conclusion, independent effects from IGFBP1, IGFBP3 diplotypes, and BRCA family status on IGFBP-3 levels were observed. These factors may influence the risk of breast cancer among women from high-risk breast cancer families.

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.

Associations of insulin-like growth factor binding protein-3 gene polymorphisms with IGF-I activity and lipid parameters in adolescents

OBJECTIVE

Childhood obesity is a growing global epidemic. Recent studies indicate that obesity and related metabolic traits are highly heritable. Increasing evidence suggests that growth hormone (GH) and the insulin-like growth factor-I (IGF-I) axis have important functions in regulating adiposity and insulin sensitivity. Five single-nucleotide polymorphisms (SNPs) at IGF-binding protein-3 (IGFBP3) were genotyped to find their associations with IGF-1 activity level and common clinical metabolic traits.

PATIENTS AND METHODS

We examined the associations of five SNPs at IGFBP3 with serum IGF-I and IGFBP-3 levels, as well as with obesity-related metabolic traits in 981 Hong Kong Chinese adolescents. Factor analysis was used to reduce the intercorrelated variables to five factor scores indicating body composition, blood pressure, IGF-I activity, triglyceride (TG)+high-density lipoprotein cholesterol (HDL-C) and total cholesterol (TC)+low-density lipoprotein cholesterol (LDL-C) factor scores.

RESULTS

There was a strong association between the -202A/C polymorphism (rs2854744) and IGF-I activity (P=1.2 x 10(-6)) and TC+LDL-C factor scores (P=0.0085), corrected for age and sex. The C allele was associated with decreased IGFBP-3 levels (P=1.21 x 10(-13)), increased IGF-I/IGFBP-3 molar ratio (P=5.22 x 10(-6)) and decreased LDL-C (P=0.020). There was also a significant association between a G/A polymorphism at the 3' flanking sequence (rs13223993) of the IGFBP3 gene and the TG+HDL-C factor score (P=0.0013). The minor A allele carriers of rs13223993 had a lower HDL-C (P=0.0067) level and a tendency toward a high TG level. Haplotype analysis did not increase the significance of associations between single SNPs and phenotypes.

CONCLUSION

Our results support the function of IGFBP3 gene polymorphisms in modulating IGF-I activity and lipid levels in adolescents. Given the prognostic significance of IGF-I, IGFBPs and lipids on risk of diabetes, obesity and cancer, long-term studies are required to clarify the clinical meaning of these findings.

Elevated MAL expression is accompanied by promoter hypomethylation and platinum resistance in epithelial ovarian cancer

We previously found that the gene encoding the Myelin and Lymphocyte protein, MAL, was among the most highly expressed genes in serous ovarian cancers from short-term survivors (<3 years) relative to those of long-term survivors (>7 years). In the present study, we have found that this difference in expression is partially attributable to differences in DNA methylation at a specific region within the MAL promoter CpG island. While MAL was largely unmethylated at the transcription start site (Region 1; -48 to +73 bp) in primary serous ovarian cancers, methylation of an upstream region (Region 2; -452 to -266 bp) was inversely correlated with MAL transcription in the primary cancers (R = -0.463) and ovarian cancer cell lines (R = -0.444). Following treatment of the OVCA432 cell line with 5-azacytidine, methylation of Region 2 decreased from 73.3% to 34.7% (p = 0.007) while Region 1 was unaffected. This was accompanied by a 10-fold increase in MAL expression. Since MAL transcripts are elevated in tumors from short-term survivors, all of whom were treated with platinum-based therapy, MAL may have a role in cisplatin response. We therefore determined the 50% growth inhibitory dose of cisplatin in 30 ovarian cancer cell lines and compared this to MAL expression. MAL transcript levels were higher in the resistant ovarian cell lines (p = 0.04). MAL methylation status may therefore serve as a marker of platinum sensitivity while MAL protein may be a target for development of novel therapies aimed at enhancing sensitivity to platinum-based drugs in ovarian cancer.

Unraveling insulin-like growth factor binding protein-3 actions in human disease

The IGF system plays critical roles in somatic growth in an endocrine fashion (somatomedin hypothesis) as well as proliferation and differentiation of normal and malignant cells in a paracrine/autocrine fashion. IGFBP-3 is known to modulate the actions of IGFs in circulation as well as the immediate extracellular environment. Interestingly, apart from the ability to inhibit or enhance IGF actions, IGFBP-3 also exhibits very clear, distinct biological effects independent of the IGF/IGF-I receptor axis. Over the past decade it has become widely appreciated that IGF/IGF-IR-independent actions of IGFBP-3 (antiproliferative and proapoptotic effects) contribute to improving the pathophysiology of a variety of human diseases, such as cancer, diabetes, and malnutrition. Recent studies have implicated interaction of IGFBP-3 with a variety of proteins or signaling cascades critical to cell cycle control and apoptosis; however, the actual mechanism of IGFBP-3 action is still unclear. This review reinforces the concept in support of the IGF/IGF-IR axis-independent actions of IGFBP-3 and delineates potential underlying mechanisms involved and subsequent biological significance, focusing in particular on functional binding partners and the clinical significance of IGFBP-3 in the assessment of cancer risk.

Genetic and epigenetic variability in the gene for IGFBP-3 (IGFBP3): correlation with serum IGFBP-3 levels and growth in short children born small for gestational age

CONTEXT

IGF-I and IGFBP-3 play a central role in fetal and postnatal growth and levels are low in short SGA children. The -202 A/C and -185 C/T SNPs are located near elements involved in directing IGFBP3 promoter activity and expression. Changes in promoter CpG methylation status affect transcription factor binding and transcriptional activation of IGFBP3 in vitro.

OBJECTIVE

To assess the relationship between IGFBP3 promoter SNPs, IGFBP-3 levels, spontaneous growth and growth response to GH treatment in short prepubertal SGA children. To assess promoter methylation status in a subgroup of short SGA subjects and controls.

PATIENTS

292 Short prepubertal SGA children, 39 short young SGA adults and 85 young adults with normal stature.

INTERVENTION

Short prepubertal SGA children received GH 1mg/m(2)/day.

OUTCOME MEASURES

Fasting levels of IGF-I and IGFBP-3, baseline and delta height SDS.

RESULTS

At baseline, IGFBP-3 levels were highest in SGA children with -202 AA genotype and lower in children with 1 or 2 copies of the C-allele (P<0.001). Children with C(-202)/C(-185) haplotype, compared to children with A(-202)/C(-185) haplotype, had lower IGFBP-3 levels (P=0.003) and were shorter (P=0.03). During GH treatment, children with C(-202)/C(-185) haplotype showed a significantly greater increase in IGFBP-3 SDS and in height SDS than children with A(-202)/C(-185) haplotype, resulting in similar IGFBP-3 levels and similar height SDS after 12 months of GH treatment. CpG methylation patterns showed a trend towards more methylation of CpGs involved in transcription factor binding in short young SGA adults compared to controls.

CONCLUSION

Polymorphic variation in the IGFBP3 promoter region is correlated with IGFBP-3 levels, spontaneous growth and response to GH treatment in short SGA children.