Insulin-like growth factors and cancer: no role in screening. Evidence from the BUPA study and meta-analysis of prospective epidemiological studies

Circulating Levels of Insulin-like Growth Factor 1 and Insulin-like Growth Factor Binding Protein 3 Associate With Risk of Colorectal Cancer Based on Serologic and Mendelian Randomization Analyses

BACKGROUND & AIMS

Human studies examining associations between circulating levels of insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein 3 (IGFBP3) and colorectal cancer risk have reported inconsistent results. We conducted complementary serologic and Mendelian randomization (MR) analyses to determine whether alterations in circulating levels of IGF1 or IGFBP3 are associated with colorectal cancer development.

METHODS

Serum levels of IGF1 were measured in blood samples collected from 397,380 participants from the UK Biobank, from 2006 through 2010. Incident cancer cases and cancer cases recorded first in death certificates were identified through linkage to national cancer and death registries. Complete follow-up was available through March 31, 2016. For the MR analyses, we identified genetic variants associated with circulating levels of IGF1 and IGFBP3. The association of these genetic variants with colorectal cancer was examined with 2-sample MR methods using genome-wide association study consortia data (52,865 cases with colorectal cancer and 46,287 individuals without [controls]) RESULTS: After a median follow-up period of 7.1 years, 2665 cases of colorectal cancer were recorded. In a multivariable-adjusted model, circulating level of IGF1 associated with colorectal cancer risk (hazard ratio per 1 standard deviation increment of IGF1, 1.11; 95% confidence interval [CI] 1.05-1.17). Similar associations were found by sex, follow-up time, and tumor subsite. In the MR analyses, a 1 standard deviation increment in IGF1 level, predicted based on genetic factors, was associated with a higher risk of colorectal cancer risk (odds ratio 1.08; 95% CI 1.03-1.12; P = 3.3 × 10-4). Level of IGFBP3, predicted based on genetic factors, was associated with colorectal cancer risk (odds ratio per 1 standard deviation increment, 1.12; 95% CI 1.06-1.18; P = 4.2 × 10-5). Colorectal cancer risk was associated with only 1 variant in the IGFBP3 gene region (rs11977526), which also associated with anthropometric traits and circulating level of IGF2.

CONCLUSIONS

In an analysis of blood samples from almost 400,000 participants in the UK Biobank, we found an association between circulating level of IGF1 and colorectal cancer. Using genetic data from 52,865 cases with colorectal cancer and 46,287 controls, a higher level of IGF1, determined by genetic factors, was associated with colorectal cancer. Further studies are needed to determine how this signaling pathway might contribute to colorectal carcinogenesis.

When Is Enough, Enough? When Are More Observational Epidemiologic Studies Needed to Resolve a Research Question: Illustrations Using Biomarker-Cancer Associations

BACKGROUND

Research reproducibility is vital for translation of epidemiologic findings. However, repeated studies of the same question may be undertaken without enhancing existing knowledge. To identify settings in which additional research is or is not warranted, we adapted research synthesis metrics to determine number of additional observational studies needed to change the inference from an existing meta-analysis.

METHODS

The fail-safe number (FSN) estimates number of additional studies of average weight and null effect needed to drive a statistically significant meta-analysis to null (P ≥ 0.05). We used conditional power to determine number of additional studies of average weight and equivalent heterogeneity to achieve 80% power in an updated meta-analysis to detect the observed summary estimate as statistically significant. We applied these metrics to a curated set of 98 meta-analyses on biomarkers and cancer risk.

RESULTS

Both metrics were influenced by number of studies, heterogeneity, and summary estimate size in the existing meta-analysis. For the meta-analysis on Helicobacter pylori and gastric cancer with 15 studies [OR = 2.29; 95% confidence interval (CI), 1.71-3.05], FSN was 805 studies, supporting futility of further study. For the meta-analysis on dehydroepiandrosterone sulfate and prostate cancer with 7 studies (OR = 1.29; 95% CI, 0.99-1.69), 5 more studies would be needed for 80% power, suggesting further study could change inferences.

CONCLUSIONS

Along with traditional assessments, these metrics could be used by stakeholders to decide whether additional studies addressing the same question are needed.

IMPACT

Systematic application of these metrics could lead to more judicious use of resources and acceleration from discovery to population-health impact.

Higher IGFBP3 is associated with increased incidence of colorectal cancer in older men independently of IGF1

OBJECTIVE

Insulin-like growth factor 1 (IGF1) has anabolic and growth-promoting effects, raising concerns regarding its potential to promote tumour growth. Circulating IGF1 is bound to binding proteins, which modulate bioavailability of IGF1. This study assessed the associations of IGF1 and its binding proteins 1 (IGFBP1) and 3 (IGFBP3) with cancer risk.

DESIGN

A prospective cohort study of 4042 men aged ≥70 years.

METHODS

Plasma total IGF1, IGFBP1 and IGFBP3 were measured between 2001 and 2004. Cancer-related outcomes were assessed until 20 June 2013 using data linkage. Analyses were performed using proportional hazards models with death as a competing risk, and adjustments were made for potential confounders. Results are expressed as subhazard ratios (SHR).

RESULTS

There were 907 men who were diagnosed with cancer during a median of 9-year follow-up. Of these, there were 359, 139 and 125 prostate, colorectal and lung cancers, respectively. After adjustments, total IGF1 was not associated with the incidence of any cancer, prostate, lung or colorectal cancer. In the fully-adjusted model, higher IGFBP3 was associated with increased incidence of colorectal cancer (SHR = 1.20, 95% CI 1.01-1.43; P = .041 for every 1 standard deviation increase in IGFBP3) but not other cancers. This effect was not attenuated by inclusion of total IGF1 into the multivariate model (SHR = 1.28, 95% CI 1.03-1.58; P = .025). Neither total IGF1, IGFBP1 nor IGFBP3 were associated with cancer-related deaths.

CONCLUSION

Higher IGFBP3 predicted increased incidence of colorectal cancer in older men independent of conventional risk factors and total IGF1. Further studies are warranted to explore potential underlying mechanisms.

Serum Insulin-Like Growth Factor Axis and the Risk of Pancreatic Cancer: Systematic Review and Meta-Analysis

Objective: To investigate the association between serum concentration of insulin-like growth factor (IGF) and the risk of pancreatic cancer (PaC). Methods: We identified eligible studies in Medline and EMBASE databases (no reference trials from 2014 to 2016) in addition to the reference lists of original studies and review articles on this topic. A summary of relative risks with 95% confidence intervals (CI) was calculated using a random-effects model. The heterogeneity between studies was assessed using Cochran Q and I² statistics. Results: Ten studies (seven nested case-control studies and three retrospective case-control studies) were selected as they met our inclusion criteria in this meta-analysis. All these studies were published between 1997 and 2013. The current data suggested that serum concentrations of IGF-I, IGF-II and insulin-like growth factor binding protein-3 (IGFBP-3)in addition to the IGF-I/IGFBP-3 ratio were not associated with an increased risk of PaC (Summary relative risks (SRRs) = 0.92, 95% CI: 0.67–1.16 for IGF-I; SRRs = 0.84, 95% CI: 0.54–1.15 for IGF-II; SRRs = 0.93, 95% CI: 0.69–1.17 for IGFBP-3; SRRs = 0.97, 95% CI: 0.71–1.23 for IGF-I/IGFBP-3 ratio). There was no publication bias in the present meta-analysis. Conclusion: Serum concentrations of IGF-I, IGF-II, IGFBP-1 and IGFBP-3 as well as the IGF-I/IGFBP-3 ratio were not associated with increased risk of PaC.

Is there a role for IGF-1 in the development of second primary cancers?

Cancer survival rates are increasing, and as a result, more cancer survivors are exposed to the risk of developing a second primary cancer (SPC). It has been hypothesized that one of the underlying mechanisms for this risk could be mediated by variations in insulin-like growth factor-1 (IGF-1). This review summarizes the current epidemiological evidence to identify whether IGF-1 plays a role in the development of SPCs. IGF-1 is known to promote cancer development by inhibiting apoptosis and stimulating cell proliferation. Epidemiological studies have reported a positive association between circulating IGF-1 levels and various primary cancers, such as breast, colorectal, and prostate cancer. The role of IGF-1 in increasing SPC risk has been explored less. Nonetheless, several experimental studies have observed a deregulation of the IGF-1 pathway, which may explain the association between IGF-1 and SPCs. Thus, measuring serum IGF-1 may serve as a useful marker in assessing the risk of SPCs, and therefore, more translational experimental and epidemiological studies are needed to further disentangle the role of IGF-1 in the development of specific SPCs.

A Meta-analysis of Individual Participant Data Reveals an Association between Circulating Levels of IGF-I and Prostate Cancer Risk

The role of insulin-like growth factors (IGF) in prostate cancer development is not fully understood. To investigate the association between circulating concentrations of IGFs (IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3) and prostate cancer risk, we pooled individual participant data from 17 prospective and two cross-sectional studies, including up to 10,554 prostate cancer cases and 13,618 control participants. Conditional logistic regression was used to estimate the ORs for prostate cancer based on the study-specific fifth of each analyte. Overall, IGF-I, IGF-II, IGFBP-2, and IGFBP-3 concentrations were positively associated with prostate cancer risk (Ptrend all ≤ 0.005), and IGFBP-1 was inversely associated weakly with risk (Ptrend = 0.05). However, heterogeneity between the prospective and cross-sectional studies was evident (Pheterogeneity = 0.03), unless the analyses were restricted to prospective studies (with the exception of IGF-II, Pheterogeneity = 0.02). For prospective studies, the OR for men in the highest versus the lowest fifth of each analyte was 1.29 (95% confidence interval, 1.16-1.43) for IGF-I, 0.81 (0.68-0.96) for IGFBP-1, and 1.25 (1.12-1.40) for IGFBP-3. These associations did not differ significantly by time-to-diagnosis or tumor stage or grade. After mutual adjustment for each of the other analytes, only IGF-I remained associated with risk. Our collaborative study represents the largest pooled analysis of the relationship between prostate cancer risk and circulating concentrations of IGF-I, providing strong evidence that IGF-I is highly likely to be involved in prostate cancer development. Cancer Res; 76(8); 2288-300. ©2016 AACR.

Genetic variants in insulin-like growth factor binding protein-3 are associated with prostate cancer susceptibility in Eastern Chinese Han men

Background

Growing evidence has indicated that insulin-like growth factor binding protein-3 (IGFBP-3) polymorphisms are associated with altered risk of prostate cancer (PCa). However, few studies have been conducted in Chinese population to validate this association.

Materials and methods

Herein, we examined the association between genetic variants in the IGFBP-3 gene and PCa risk in the Chinese Han population based on a genome-wide association study (1,417 cases and 1,008 controls), and replicated three genetic variants loci in an independent case-control study (1,755 cases and 1,523 controls) using Sequenom platform. Logistic regression analyses were performed to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results

We found that in the discovery stage, rs9691259 (OR =0.691, 95% CI: 0.587–0.814, P<0.001) and rs6950179 (OR =1.420, 95% CI: 1.201–1.677, P<0.001) were significantly associated with PCa risk, whereas rs2854744 showed a marginal association with PCa risk. In the replication stage, the association between rs9691259 and rs6950179 and PCa risk was not replicated, whereas rs2854744 conferred a significant association with PCa risk (OR =1.399, 95% CI: 1.010–1.937, P=0.043). After combining the two stages, we found that rs9691259, rs6950179, and rs2854744 were all significantly associated with PCa risk.

Conclusion

This study suggests that IGFBP-3 genetic variants are significantly associated with PCa risk in the Chinese population.

The Influence of Exercise on the Insulin-like Growth Factor Axis in Oncology: Physiological Basis, Current, and Future Perspectives

Exercise and physical activity have been shown to reduce the risk of many common cancers and strongly influence tumor biology. A cause-effect mechanism explaining this relationship is dependent on cellular pathways that can influence tumor growth and are exercise responsive. The insulin-like growth factor (IGF) axis is reported to promote the development and progression of carcinomas through cellular signaling in cancerous tissues. This review summarizes the physiologic basis of the role of the IGF axis in oncology and the influence of exercise on this process. We examined the effects of exercise prescription on the IGF axis in cancer survivors by evaluating the current scope of the literature. The current research demonstrates a remarkable heterogeneity and inconsistency in the responses of the IGF axis to exercise in breast, prostate, and colorectal cancer survivors. Finally, this review presents an in-depth exploration of the physiologic basis and mechanistic underpinnings of the seemingly disparate relationship between exercise and the IGF axis in oncology. Although there is currently insufficient evidence to categorize the effects of exercise prescription on the IGF axis in cancer survivors, the inconsistency of results suggests a multifaceted relationship, the complexities of which are considered in this review.

Circulating levels of IGF-1, IGFBP-3, and IGF-1/IGFBP-3 molar ratio and colorectal adenomas: A meta-analysis

BACKGROUNDS

Insulin-like growth factor-1(IGF-1) promotes cell proliferation and inhibits apoptosis, and is thereby implicated in carcinogenesis. Insulin-like growth factor binding protein-3 (IGFBP-3) may antagonize IGF-1 action, leading to inhibition of the potential tumorigenicity of IGF-1. We conducted this meta-analysis to estimate the association between IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio and the risk of colorectal adenomas (CRAs). Further, we investigated whether this association was different between occurrent and recurrent CRA, by adjustment for obesity, and by advanced CRA.

MATERIALS AND METHODS

Pubmed and Embase were searched up to April, 2015 to identify relevant observational studies and summary odds ratio (OR) and the corresponding 95% confidence interval (95% CI) was estimated using a random-effects model.

RESULTS

A total of 12 studies (11 studies including 3038 cases for IGF-1, 12 studies including 3208 cases for IGFBP-3, and 7 studies including 1867 cases for IGF-1/IGFBP-3 ratio) were included in this meta-analysis. The summary ORs of occurrent CRA for the highest versus lowest category of IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio were 1.13 (95% CI: 0.95-1.34), 0.99 (0.84-1.16), and 1.05 (0.86-1.29), respectively. Higher IGF-1 and IGF-1/IGFBP-3 ratio were significantly associated with decreased risk of recurrent CRA (OR for IGF-1=0.60 [95% CI: 0.42-0.85]; IGF-1/IGFBP-3 ratio=0.65 [0.44-0.96]). A stratified analysis by advancement of occurrent CRA produced a significant summary OR of IGF-1 for advanced CRA (OR=2.21 [1.08-4.52]) but not for non-advanced CRA (OR=0.89 [0.55-1.45]). We did not find significant publication bias or heterogeneity.

CONCLUSION

Circulating levels of IGF-1, IGFBP-3 and their molar ratio were not associated with the risk of occurrence of CRA, but IGF-1 was associated with the increased risk for occurrence of advanced CRA.

Application of credibility ceilings probes the robustness of meta-analyses of biomarkers and cancer risk

OBJECTIVES

Meta-analyses of biomarkers often present spurious significant results and large effects. We applied sensitivity analyses with the use of credibility ceilings to assess whether and how the results of meta-analyses of biomarkers and cancer risk would change.

STUDY DESIGN AND SETTING

We evaluated 98 meta-analyses, 43 (44%) of which had nominally statistically significant results. We assumed that any single study cannot give more than a maximum certainty 100 - c% (c, credibility ceiling) that the effect estimate [odds ratio (OR)] exceeds 1 (null) or 1.2.

RESULTS

Nominal statistical significance was maintained for 21 (21%) meta-analyses, for c = 10% and OR >1, and these proportions changed to 7%, 3%, and 6% with ceilings of 20%, 30%, and 40%, respectively. For ceilings for OR >1.2, the respective proportions were 37%, 21%, 7%, and 3%. Seven meta-analyses on infectious agents retained statistical significance even with a high ceiling of c = 20% for OR >1.00. Meta-analyses without other hints of bias (large between-study heterogeneity, small-study effects, excess significance) were more likely to retain statistical significance than those that had such hints of bias.

CONCLUSION

Credibility ceilings may be helpful in meta-analyses of biomarkers to understand the robustness of the results to different levels of uncertainty.

Type 2 diabetes: a protective factor for prostate cancer? An overview of proposed mechanisms

Diabetes mellitus and prostate cancer are 2 of the most important public health concerns, especially in the elderly population. Although diabetes has been recognized as a potent risk factor for many types of cancers, there is a large amount of evidence that shows that it has a protective role against prostate cancer. The underlying cause of this protective role is not fully understood, however, some mechanisms have been proposed in this area. In the present study we have reviewed these mechanisms and some new mechanisms are also proposed.

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.

Genetic variation in insulin pathway genes and distal colorectal adenoma risk

BACKGROUND

Insulin, glucose, and other insulin-related proteins that mediate insulin signaling are associated with colorectal neoplasia risk, but associations with common genetic variation in insulin axis genes are less clear. In this study, we used a comprehensive tag single-nucleotide polymorphisms (SNPs) approach to define genetic variation in six insulin axis genes (IGF1, IGF2, IGFBP1, IGFBP3, IRS1, and IRS2) and three genes associated with estrogen signaling (ESR1, ESR2, and PGR).

METHODS

We assessed associations between SNPs and distal colorectal adenoma (CRA) risk in a case-control study of 1,351 subjects. Cases were individuals with one or more adenomas diagnosed during sigmoidoscopy, and controls were individuals with no adenomas at the sigmoidoscopy exam. We used unconditional logistic regression assuming an additive model to assess SNP-specific risks adjusting for multiple comparisons with P (act).

RESULTS

Distal adenoma risk was significantly increased for one SNP in IGF2 [per minor allele OR = 1.41; 95 % confidence interval (CI) = 1.16, 1.67; P (act) = 0.005] and decreased for an ESR2 SNP (per minor allele OR = 0.78; 95 % CI = 0.66, 0.91; P (act) = 0.041). There was no statistically significant heterogeneity of these associations by race, sex, BMI, physical activity, or, in women, hormone replacement therapy use. Risk estimates did not differ in the colon versus rectum or for smaller (<1 cm) versus larger (>1 cm) adenomas.

CONCLUSIONS

These data suggest that selected genetic variability in IGF2 and ESR2 may be modifiers of CRA risk.

Association between circulating levels of IGF-1 and IGFBP-3 and lung cancer risk: a meta-analysis

Background

The insulin-like growth factor (IGF) system was documented to play a predominant role in neoplasia. As lung cancer is one of the most malignant cancers, we conducted a meta-analysis in order to investigate the strength of association between circulating IGF-1 and IGFBP-3 levels and lung cancer.

Methodology/Principal Findings

A systematic literature search was conducted to identify all prospective case-control studies and case-control studies on circulating IGFs and IGFBPs levels. Six nested case-control studies (1 043 case subjects and 11 472 control participants) and eight case-control studies (401 case subjects and 343 control participants) were included in this meta-analysis. Pooled measure was calculated as the inverse variance-weighted mean of the natural logarithm of multivariate adjusted OR with 95% CIs for highest vs. lowest levels to assess the association of circulating IGF-1 and IGFBP-3 concentrations and lung cancer. Standard mean difference (SMD) was also calculated to indicate the difference of the circulating IGF-1 and IGFBP-3 concentrations between the lung cancer case group and the control group. Of the nested case-control studies, ORs for the highest vs. lowest levels of IGF-1 and IGFBP-3 were 1.047 (95% CI: [0.802,1.367], P = 0.736) and 0.960 (95%CI: [0.591,1.559], P = 0.868) respectively; and SMDs were −0.079 (95%CI:[ −0.169, 0.011], P = 0.086) and −0.097 (95%CI:[ −0.264,0.071], P = 0.258) for IGF-1 and IGFBP-3 respectively. As to the case-control studies, SMDs were 0.568 (95%CI:[ −0.035, 1.171], P = 0.065) and −0.780 (95%CI:[ −1.358, −0.201], P = 0.008) for IGF-1 and IGFBP-3 respectively.

Conclusions/Significance

Inverse association was shown between IGFBP-3 and lung cancer in the case-control studies,and the circulating level of IGFBP-3 underwent a decline during tumorogenesis and development of lung cancer, which suggested IGFBP-3 a promising candidate for the biomarker of lung cancer.

Apigenin Modulates Insulin-like Growth Factor Axis: Implications for Prevention and Therapy of Prostate Cancer

Aberrant changes to the insulin-like growth factor (IGF) axis promote prostate cancer development and progression, adaptation for growth and survival in a castrate environment, and invasive metastasis. Natural and/or synthetic compounds that target the IGF axis to prevent or reverse theses abnormalities may be extremely useful in the chemoprevention and/or chemotherapy of prostate cancer. Apigenin, a naturally-occurring flavone found in many fruits and vegetables, is one such compound that can correctively modulate the IGF axis to induce growth arrest and apoptosis in many pre-clinical in vitro and in vivo models of prostate cancer. Because of its known mechanism of action, low toxicity, and effectiveness at physiologically relevant levels in animal models of prostate cancer, apigenin is an excellent candidate for a pilot study to determine the effect of apigenin supplementation on prostate cancer development and progression in humans.

Evaluation of excess statistical significance in meta-analyses of 98 biomarker associations with cancer risk

BACKGROUND

Numerous biomarkers have been associated with cancer risk. We assessed whether there is evidence for excess statistical significance in results of cancer biomarker studies, suggesting biases.

METHODS

We systematically searched PubMed for meta-analyses of nongenetic biomarkers and cancer risk. The number of observed studies with statistically significant results was compared with the expected number, based on the statistical power of each study under different assumptions for the plausible effect size. We also evaluated small-study effects using asymmetry tests. All statistical tests were two-sided.

RESULTS

We included 98 meta-analyses with 847 studies. Forty-three meta-analyses (44%) found nominally statistically significant summary effects (random effects). The proportion of meta-analyses with statistically significant effects was highest for infectious agents (86%), inflammatory (67%), and insulin-like growth factor (IGF)/insulin system (52%) biomarkers. Overall, 269 (32%) individual studies observed nominally statistically significant results. A statistically significant excess of the observed over the expected number of studies with statistically significant results was seen in 20 meta-analyses. An excess of observed vs expected was observed in studies of IGF/insulin (P ≤ .04) and inflammation systems (P ≤ .02). Only 12 meta-analyses (12%) had a statistically significant summary effect size, more than 1000 case patients, and no hints of small-study effects or excess statistical significance; only four of them had large effect sizes, three of which pertained to infectious agents (Helicobacter pylori, hepatitis and human papilloma viruses).

CONCLUSIONS

Most well-documented biomarkers of cancer risk without evidence of bias pertain to infectious agents. Conversely, an excess of statistically significant findings was observed in studies of IGF/insulin and inflammation systems, suggesting reporting biases.

Serum IGF1, IGF2 and IGFBP3 and risk of advanced colorectal adenoma

The insulin-like growth factor (IGF) signaling pathway is involved in cell proliferation and differentiation. Elevated serum IGF1 levels have been associated with increased colorectal cancer risk; however, studies of this association with colorectal adenoma are inconclusive. We examined serum IGF1, IGF2 and IGFBP3 levels in relation to risk of advanced colorectal adenoma in a case-control study within the prostate, lung, colorectal and ovarian cancer screening trial. A total of 764 advanced, left-sided colorectal adenoma cases and 775 controls frequency-matched on gender and ethnicity, without evidence of a left-sided polyp on sigmoidoscopy were included in the current study. Serum levels of IGF1, IGF2 and IGFBP3 were measured using an enzyme linked immunosorbent assay in serum samples collected at baseline. Logistic regression was used to estimate the odds ratios (OR) and 95% confidence intervals (CI) for the associations adjusting for age, race, sex, year of blood draw, body mass index, smoking and education. Higher IGF1 levels were associated with increased adenoma risk: ORs = 1.58 (95% CI = 1.16-2.16), 1.42 (95% CI = 1.04-1.93), and 1.80 (95% CI = 1.30-2.47) for the second, third and fourth quartiles, respectively (p(trend) = 0.002). Elevated IGF2 levels were also associated with increased adenoma risk (OR = 1.43, 95% CI = 1.05-1.96 for the fourth vs. first quartile, p(trend) = 0.02), but the association was no longer significant after adjustment for IGF1 (p(trend) = 0.28). IGFBP3 levels were not associated with adenoma risk. Our analysis showed a significant positive association between circulating IGF1 levels and risk of advanced colorectal adenoma, suggesting that IGF1 is associated with the pivotal precursor to colorectal cancer.

Primary study authors of significant studies are more likely to believe that a strong association exists in a heterogeneous meta-analysis compared with methodologists

OBJECTIVE

To assess the interpretation of a highly heterogeneous meta-analysis by authors of primary studies and by methodologists.

STUDY DESIGN AND SETTING

We surveyed the authors of studies on the association between insulin-like growth factor 1 (IGF-1) and prostate cancer, and 20 meta-analysis methodologists. Authors and methodologists presented with the respective meta-analysis results were queried about the effect size and potential causality of the association. We evaluated whether author responses correlated with the number of IGF-related articles they had published and their study results included in the meta-analysis. We also compared authors' and methodologists' responses.

RESULTS

Authors who had published more IGF-related papers offered more generous effect size estimates for the association (ρ(s)=0.61, P=0.01) and higher likelihood that the odds ratio (OR) was greater than 1.20 (ρ(s)=0.63, P=0.01). Authors who had published themselves studies with statistically significant effects for a positive association were more likely to believe that the true OR is greater than 1.20 compared with methodologists (median likelihood 50% versus 2.5%, P=0.01).

CONCLUSION

Researchers are influenced by their own investment in the field, when interpreting a meta-analysis that includes their own study. Authors who published significant results are more likely to believe that a strong association exists compared with methodologists.

Genetic variants, prediagnostic circulating levels of insulin-like growth factors, insulin, and glucose and the risk of colorectal cancer: the Multiethnic Cohort study

BACKGROUND

Increased exposure of colonic and rectal epithelial cells to the promitotic and antiapoptotic effects of insulin and insulin-like growth factors (IGF) is hypothesized to increase colorectal cancer risk.

METHODS

In a case-control study nested within the Multiethnic Cohort, we attempted to replicate associations for five genetic variants associated with IGF system biomarkers, insulin, or glucose and to examine their association with the risk of colorectal cancer. In a subset of participants, the association between circulating biomarkers and colorectal cancer risk was examined. Unconditional logistic regression was used to calculate ORs and 95% confidence intervals (CI) for genetic variants (1,954 cases/2,587 controls) and serum biomarkers (258 cases/1,701 controls).

RESULTS

Associations with circulating biomarkers were replicated in the Multiethnic Cohort for IGF1 rs35767 and for IGFBP3 rs2854744, rs2854746, and rs3110697 (P < 0.05). Homozygous carriers of the glucokinase regulator (GCKR) rs780094 variant T-allele were at a decreased risk of colorectal cancer (OR, 0.77; 95% CI, 0.64-0.92). In risk factor-adjusted models, participants with the highest prediagnostic IGF-II levels were at an increased risk [OR (T1 vs. T3), 1.58; 95% CI, 1.09-2.28; P(trend) = 0.011] and participants with the highest prediagnostic IGF-binding protein (IGFBP)-3 levels were at a decreased risk of colorectal cancer (OR, 0.53; 95% CI, 0.34-0.83; P(trend) = 0.003).

CONCLUSION

These data provide further support for a role of prediagnostic IGF and insulin levels in the etiology of colorectal cancer.

IMPACT

Future studies attempting to replicate the association between the GCKR rs780094 variant and the risk of colorectal cancer are warranted.

Height and cancer incidence in the Million Women Study: prospective cohort, and meta-analysis of prospective studies of height and total cancer risk

Background

Epidemiological studies have shown that taller people are at increased risk of cancer, but it is unclear if height-associated risks vary by cancer site, or by other factors such as smoking and socioeconomic status. Our aim was to investigate these associations in a large UK prospective cohort with sufficient information on incident cancer to allow direct comparison of height-associated risk across cancer sites and in relation to major potential confounding and modifying factors.

Methods

Information on height and other factors relevant for cancer was obtained in 1996–2001 for middle-aged women without previous cancer who were followed up for cancer incidence. We used Cox regression models to calculate adjusted relative risks (RRs) per 10 cm increase in measured height for total incident cancer and for 17 specific cancer sites, taking attained age as the underlying time variable. We also did a meta-analysis of published results from prospective studies of total cancer risk in relation to height.

Findings

1 297 124 women included in our analysis were followed up for a total of 11·7 million person-years (median 9·4 years per woman, IQR 8·4–10·2), during which time 97 376 incident cancers occurred. The RR for total cancer was of 1·16 (95% CI 1·14–1·17; p<0·0001) for every 10 cm increase in height. Risk increased for 15 of the 17 cancer sites we assessed, and was statistically significant for ten sites: colon (RR per 10 cm increase in height 1·25, 95% CI 1·19–1·30), rectum (1·14, 1·07–1·22), malignant melanoma (1·32, 1·24–1·40), breast (1·17, 1·15–1·19), endometrium (1·19, 1·13–1·24), ovary (1·17, 1·11–1·23), kidney (1·29, 1·19–1·41), CNS (1·20, 1·12–1·29), non-Hodgkin lymphoma (1·21, 1·14–1·29), and leukaemia (1·26, 1·15–1·38). The increase in total cancer RR per 10 cm increase in height did not vary significantly by socioeconomic status or by ten other personal characteristics we assessed, but was significantly lower in current than in never smokers (p<0·0001). In current smokers, smoking-related cancers were not as strongly related to height as were other cancers (RR per 10 cm increase in height 1·05, 95% CI 1·01–1·09, and 1·17, 1·13–1·22, respectively; p=0·0004). In a meta-analysis of our study and ten other prospective studies, height-associated RRs for total cancer showed little variation across Europe, North America, Australasia, and Asia.

Interpretation

Cancer incidence increases with increasing adult height for most cancer sites. The relation between height and total cancer RR is similar in different populations.

Funding

Cancer Research UK and the UK Medical Research Council.

Plasma insulin-like growth factor 1 is positively associated with low-grade prostate cancer in the Health Professionals Follow-up Study 1993-2004

The insulin-like growth factor (IGF) axis plays a role in growth and progression of prostate cancer. High circulating IGF-1 levels have been associated with an increased risk of prostate cancer. Results for IGF binding protein 3 (IGFBP-3) are inconclusive. Some studies have indicated that the positive association with IGF-1 is observed only for low-grade prostate cancer (Gleason sum < 7). We previously reported in the Health Professionals Follow-up Study (HPFS) a direct positive association between ELISA-measured plasma IGF-1 and IGFBP-3 and risk of prostate cancer (462 cases diagnosed after providing a blood specimen (between 1993 and 1995), but before February 1998). With additional follow-up through January 31st 2004, and 1,331 case-control pairs in total, we were now able to investigate low-grade (Gleason sum < 7, n = 635) and high-grade (Gleason sum ≥ 7, n = 515) prostate cancer separately. Matched odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression. ORs of total prostate cancer comparing top to bottom quartiles were 1.41 (95% CI 1.12-1.78, p-trend = 0.001) for IGF-1 and 1.58 (95% CI 1.24-2.01, p-trend = 0.003) for IGFBP-3. IGF-1 was more strongly associated with low-grade (OR = 1.61 top versus bottom quartile, 95% CI 1.16-2.25, p-trend = 0.01), than with high-grade (OR = 1.29, 95% CI 0.89-1.88, p-trend = 0.12) prostate cancer (p-heterogeneity = 0.08). We hypothesize that these findings reflect that high-grade prostate cancers are more autonomous, and, thus, less sensitive to the action of IGF-1 than low-grade cancers.

Genes in the insulin and insulin-like growth factor pathway and odds of metachronous colorectal neoplasia

Insulin and insulin-like growth factor (IGF) genes are implicated in colorectal carcinogenesis. Gene-by-gene interactions that influence the insulin/IGF pathways were hypothesized as modifiers of colorectal neoplasia risk. We built a classification tree to detect interactions in 18 IGF and insulin pathway-related genes and metachronous colorectal neoplasia among 1,439 subjects pooled from two chemoprevention trials. The probability of colorectal neoplasia was greatest (71.8%) among carriers of any A allele for rs7166348 (IGF1R) and AA genotype for rs1823023 (PIK3R1). In contrast, carriers of any A at rs7166348 (IGF1R), any G for the PIK3R1 variant, and AA for rs10426094 (INSR) had the lowest probability (14.3%). Logistic regression modeling showed that any A at rs7166348 (IGF1R) with the AA genotype at rs1823023 (PIK3R1) conferred the highest odds of colorectal neoplasia (OR 3.7; 95% CI 2.2-6.5), compared with carriage of GG at rs7166348 (IGF1R). Conversely, any A at rs7166348 (IGFR1), any G allele at rs1823023 (PIK3R1), and the AA genotype at rs10426094 (INSR) conferred the lowest odds (OR 0.22; 95% CI 0.07-0.66). Stratifying the analysis by parent study and intervention arm showed highly consistent trends in direction and magnitude of associations, with preliminary evidence of genotype effects on measured IGF-1 levels in a subgroup of subjects. These results were compared to those from multifactor dimensionality reduction, which identified different single nucleotide polymorphisms in the same genes (INSR and IGF1R) as effect modifiers for colorectal neoplasia. These results support a role for genetic interactions in the insulin/IGF pathway genes in colorectal neoplasia risk.

Growth hormone, the insulin-like growth factor axis, insulin and cancer risk

Growth hormone (GH), insulin-like growth factor (IGF)-I and insulin have potent growth-promoting and anabolic actions. Their potential involvement in tumor promotion and progression has been of concern for several decades. The evidence that GH, IGF-I and insulin can promote and contribute to cancer progression comes from various sources, including transgenic and knockout mouse models and animal and human cell lines derived from cancers. Assessments of the GH-IGF axis in healthy individuals followed up to assess cancer incidence provide direct evidence of this risk; raised IGF-I levels in blood are associated with a slightly increased risk of some cancers. Studies of human diseases characterized by excess growth factor secretion or treated with growth factors have produced reassuring data, with no notable increases in de novo cancers in children treated with GH. Although follow-up for the vast majority of these children does not yet extend beyond young adulthood, a slight increase in cancers in those with long-standing excess GH secretion (as seen in patients with acromegaly) and no overall increase in cancer with insulin treatment, have been observed. Nevertheless, long-term surveillance for cancer incidence in all populations exposed to increased levels of GH is vitally important.

Prostate cancer and acromegaly

Acromegalic patients have an increased prevalence of prostatic disorders compared to age-matched healthy subjects. Increased size of the whole prostate or the transitional zone, together with an elevated incidence of other structural changes, such as nodules, cysts, and calcifications, have been reported. Prostate enlargement in young acromegalic patients with low testosterone levels due to central hypogonadism supports the hypothesis that chronic GH and IGF-I excess cause prostate hyperplasia. The relationship between prostatic carcinoma and acromegaly is, until now, only circumstantial. Long-term follow-up of these patients is necessary since epidemiologic studies showed association between serum IGF-I levels in the upper normal limit and prostate cancer in the general population. This review approaches prostate diseases in patients with acromegaly.

IGF-I, insulin and prostate cancer

Prostate cancer is the second most frequent malignancy diagnosed in adult men. Androgens are considered the primary growth factors for prostate normal and cancer cells. However, other non-androgenic growth factors are involved in the growth regulation of prostate cancer cells. The association between IGF-I and prostate cancer risk is well established. However, there is no evidence that the measurement of IGF-I enhances the specificity of prostate cancer detection beyond that achievable by serum prostate-specific antigen (PSA) levels. Until now, there is no consensus on the possible association between IGFBP-3 and prostate cancer risk. Although not well established, it seems that high insulin levels are particularly associated with risk of aggressive prostatic tumours. This review describes the physiopathological basis, epidemiological evidence, and animal models that support the association of the IGFs family and insulin with prostate cancer. It also describes the potential therapies targeting these growth factors that, in the future, can be used to treat patients with prostate cancer.

A comprehensive analysis of common IGF1, IGFBP1 and IGFBP3 genetic variation with prospective IGF-I and IGFBP-3 blood levels and prostate cancer risk among Caucasians

The insulin-like growth factor (IGF) pathway has been implicated in prostate development and carcinogenesis. We conducted a comprehensive analysis, utilizing a resequencing and tagging single-nucleotide polymorphism (SNP) approach, between common genetic variation in the IGF1, IGF binding protein (BP) 1, and IGFBP3 genes with IGF-I and IGFBP-3 blood levels, and prostate cancer (PCa) risk, among Caucasians in the NCI Breast and Prostate Cancer Cohort Consortium. We genotyped 14 IGF1 SNPs and 16 IGFBP1/IGFBP3 SNPs to capture common [minor allele frequency (MAF) >or= 5%] variation among Caucasians. For each SNP, we assessed the geometric mean difference in IGF blood levels (N = 5684) across genotypes and the association with PCa risk (6012 PCa cases/6641 controls). We present two-sided statistical tests and correct for multiple comparisons. A non-synonymous IGFBP3 SNP in exon 1, rs2854746 (Gly32Ala), was associated with IGFBP-3 blood levels (P(adj) = 8.8 x 10(-43)) after adjusting for the previously established IGFBP3 promoter polymorphism A-202C (rs2854744); IGFBP-3 blood levels were 6.3% higher for each minor allele. For IGF1 SNP rs4764695, the risk estimates among heterozygotes was 1.01 (99% CI: 0.90-1.14) and 1.20 (99% CI: 1.06-1.37) for variant homozygotes with overall PCa risk. The corrected allelic P-value was 8.7 x 10(-3). IGF-I levels were significantly associated with PCa risk (P(trend) = 0.02) with a 21% increase of PCa risk when compared with the highest quartile to the lowest quartile. We have identified SNPs significantly associated with IGFBP-3 blood levels, but none of these alter PCa risk; however, a novel IGF1 SNP, not associated with IGF-I blood levels, shows preliminary evidence for association with PCa risk among Caucasians.

Insulin, insulin resistance, obesity, and cancer

Epidemiologic studies have proposed a link between obesity, type 2 diabetes, and cancer. The pathophysiologic mechanisms involved in the development of type 2 diabetes, namely hyperinsulinemia and insulin resistance, have also been implicated in cancer development. Patients with type 2 diabetes are reported to have a worse response to cancer chemotherapy, have more complications, and have a poorer prognosis than patients with cancer without diabetes. Studies also have reported that insulin, insulin secretagogues, and metformin may have effects on tumor growth. Given the escalating worldwide prevalence of obesity and type 2 diabetes, their relationship to cancer has generated great interest and research across many fields of medicine.

IGF-I and IGFBP-3 and the risk of lung cancer: a meta-analysis based on nested case-control studies

BACKGROUND

Lung cancer is the leading cause of death from cancer worldwide. Conventional studies mainly think that insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) may promote and inhibit tumor growth, respectively. However, there are many different results about their function in some recent epidemiological studies. To evaluate the relationship between circulating serum levels of IGF-I, IGFBP-3 and lung cancer, a systematic review and meta-analysis of the published data was performed.

METHODS

Literatures searched on PubMed and Embase databases were enrolled in the Meta-analysis. The Meta-analysis of all eligible studies was applied with Stata 10.0 software, and the pooled odds ratio(OR) and weighted mean difference (WMD) value were obtained. The Q test, Egger's test and Begg's funnel plot were used to evaluate the heterogeneity and publication bias between the studies.

RESULTS

There are no statistically significant heterogeneity and publication bias between the studies. For IGF- I, the pooled OR and WMD were 0.87(95%CI: 0.60 approximately 1.13,) and -3.04(95%CI: -7.10 approximately 1.02, P = 0.14), respectively. For IGFBP-3, the pooled OR and WMD were 0.68(95%CI: 0.48 approximately 0.88,) and -112.28(95%CI: -165.88 approximately -58.68, P < 0.0001), respectively.

CONCLUSION

The association between circulating IGF- I levels and the risk of lung cancer were not statistically significant; IGFBP-3, acts as a tumor suppressor and has a inverse correlation with the risk of lung cancer.

Value of insulin-like growth factor binding protein 2 in early diagnosis of nonalcoholic fatty liver disease

AIM: To study the value of quantitative determination of insulin-like growth factor binding protein 2 in the diagnosis of nonalcoholic fatty liver disease (NAFLD).

METHODS: ELISA was used to measure the serous IGFBP2 of patients with NAFLD, chronic hepatitis, and hepatic cirrhosis, primary carcinoma of the liver and healthy adults. The results were statistically analyzed.

RESULTS: The serous IGFBP2 was significantly higher in NAFLD group than in other groups (6.89 ± 2.37 µg/L, 4.86 ± 1.97 µg/L vs 1.77 ± 1.56 µg/L, 1.67 ± 1.36 µg/L, 1.76 ± 1.52 µg/L, 1.52 ± 1.43 µg/L, all P < 0.05). The serum IGFBP2 in mild NAFLD group was significantly higher than in middle or sever NAFLD groups (P < 0.05).

CONCLUSION: The study suggests that screening test of serous IGFBP2 is a useful marker for recognizing the stage and degree of NAFLD.

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

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

Circulating insulin-like growth factor peptides and prostate cancer risk: a systematic review and meta-analysis

Insulin-like growth factors (IGF-I, IGF-II) and their binding proteins (IGFBP-1-6) play a key role in cell proliferation, differentiation and apoptosis, suggesting possible involvement in carcinogenesis. Several epidemiological studies show associations of IGFs with prostate cancer. We searched the published literature for all studies relating levels of IGFs or IGFBPs with prostate cancer. We performed random effects meta-analysis to calculate summary odds ratios. The number of studies (prostate cancer cases) included in each meta-analysis were 42 (7,481) IGF-I; 10 (923) IGF-II; 3 (485) IGFBP-1; 5 (577) IGFBP-2; 29 (6,541) IGFBP-3 and 11 (3,545) IGF-1:IGFBP-3 ratio. The pooled odds ratios (95% confidence intervals) per standard deviation increase in peptide were: IGF-I, OR = 1.21 (1.07, 1.36); IGF-II, OR = 1.17 (0.93, 1.47); IGFBP-1, OR = 1.21 (0.62, 2.33); IGFBP-2, OR = 1.18 (0.90, 1.54); IGFBP-3, OR = 0.88 (0.79, 0.98); IGFI:IGFBP-3 ratio, OR = 1.10 (0.97, 1.24). For all exposures, there was substantial heterogeneity (all I(2) > 75%), partly explained by study design: the magnitude of associations was smaller in prospective vs. retrospective studies, and for IGFBP-3, the inverse association with prostate cancer risk was seen in retrospective but not prospective studies. There was weak evidence that associations of IGF-I and IGFBP-3 with prostate cancer were stronger for advanced disease. Our meta-analysis confirms that raised circulating lGF-I is positively associated with prostate cancer risk. Associations between IGFBP-3 and prostate cancer were inconsistent, and there was little evidence for a role of IGF-II, IGFBP-1 or IGFBP-2 in prostate cancer risk.

Expression of insulin-like growth factor system components in colorectal tissue and its relation with serum IGF levels

CONTEXT

The insulin-like growth factor (IGF)-system has been implicated in colorectal tumor carcinogenesis. Although both tumor expression levels and serum concentrations of IGF-system components are related to colorectal cancer risk, it is unknown whether IGF levels in tissue and serum are correlated.

OBJECTIVE

The objective of this study was to determine expression levels of various IGF-system components in different locations of the colorectum, and to investigate whether normal tissue IGF expression levels are correlated with serum IGF-I and IGF-II concentrations.

DESIGN

Biopsies from macroscopically normal mucosa at four locations in the colorectum (ascending, transverse, sigmoid colon, and rectum) and a fasting serum sample were obtained from 48 asymptomatic patients at increased risk of colorectal cancer. Expression levels of IGF-I, IGF-II, IGF-IR, IGF-IIR, and IGFBP-3 messenger RNA (mRNA) in tissue were quantitatively evaluated using real-time RT-PCR. Expression of IGF-IR protein in the ascending colon and rectum tissue specimens was assessed semi-quantitatively by immunohistochemistry. Serum IGF-I and IGF-II concentrations were determined using immunometric assays.

RESULTS

With the exception of IGF-IIR, mRNA levels of all the IGF-system components investigated, as well as IGF-IR protein expression, were significantly higher in the rectum compared with the ascending colon (p<or=0.001). Serum IGF-I and IGF-II concentrations did not correlate with any of the parameters studied in colorectal tissues.

CONCLUSIONS

Our results indicate that in humans IGF-system components are differentially expressed in the colorectum. Moreover, our findings suggest that local and circulating components of the IGF-system are differentially regulated. However, due to large intra-individual variation in mRNA expression, we cannot formally exclude undetected but existing routes of co-regulation.

Insulin-like growth factor-1 receptor-targeted therapy for non-small cell lung cancer: a mini review

Lung cancer leads all other cancers in both incidence and mortality. Recent advances in underlying molecular pathogenesis have validated a panel of protein tyrosine kinases as new targets in lung cancer treatment. Insulin-like growth factor-1 receptor (IGF-1R) is an important tyrosine kinase receptor involved in cell proliferation, differentiation, metabolism, apoptosis, and angiogenesis. Aberrant activation of IGF-1R is frequently found in patients with lung cancer and contributes to malignant transformation and poor prognosis for patients with lung cancer. In this review, we focused on recent progress in the research of IGF-1R's role in lung cancer development and progression, including its structure and biological function, potential mechanisms of aberrant activation, and related oncogenic effects. We also discussed effective IGF-1R antagonists that are currently registered for clinic trials or are undergoing preclinical study with special emphasis on their antibodies and small molecule tyrosine kinase inhibitors.

Insulin-like growth factors, their binding proteins, and prostate cancer risk: analysis of individual patient data from 12 prospective studies

BACKGROUND

Some, but not all, published results have shown an association between circulating blood levels of some insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) and the subsequent risk for prostate cancer.

PURPOSE

To assess the association between levels of IGFs and IGFBPs and the subsequent risk for prostate cancer.

DATA SOURCES

Studies identified in PubMed, Web of Science, and CancerLit.

STUDY SELECTION

The principal investigators of all studies that published data on circulating concentrations of sex steroids, IGFs, or IGFBPs and prostate cancer risk using prospectively collected blood samples were invited to collaborate.

DATA EXTRACTION

Investigators provided individual participant data on circulating concentrations of IGF-I, IGF-II, IGFBP-II, and IGFBP-III and participant characteristics to a central data set in Oxford, United Kingdom.

DATA SYNTHESIS

The study included data on 3700 men with prostate cancer and 5200 control participants. On average, case patients were 61.5 years of age at blood collection and received a diagnosis of prostate cancer 5 years after blood collection. The greater the serum IGF-I concentration, the greater the subsequent risk for prostate cancer (odds ratio [OR] in the highest vs. lowest quintile, 1.38 [95% CI, 1.19 to 1.60]; P < 0.001 for trend). Neither IGF-II nor IGFBP-II concentrations were associated with prostate cancer risk, but statistical power was limited. Insulin-like growth factor I and IGFBP-III were correlated (r = 0.58), and although IGFBP-III concentration seemed to be associated with prostate cancer risk, this was secondary to its association with IGF-I levels. Insulin-like growth factor I concentrations seemed to be more positively associated with low-grade than high-grade disease; otherwise, the association between IGFs and IGFBPs and prostate cancer risk had no statistically significant heterogeneity related to stage or grade of disease, time between blood collection and diagnosis, age and year of diagnosis, prostate-specific antigen level at recruitment, body mass index, smoking, or alcohol intake.

LIMITATIONS

Insulin-like growth factor concentrations were measured in only 1 sample for each participant, and the laboratory methods to measure IGFs differed in each study. Not all patients had disease stage or grade information, and the diagnosis of prostate cancer may differ among the studies.

CONCLUSION

High circulating IGF-I concentrations are associated with a moderately increased risk for prostate cancer.

Targeted deletion of hepatic Igf1 in TRAMP mice leads to dramatic alterations in the circulating insulin-like growth factor axis but does not reduce tumor progression

The role of systemic and local insulin-like growth factor I (IGF-I) in the development of prostate cancer is still controversial. Transgenic adenocarcinoma mouse prostate (TRAMP) mice express the SV40 T-antigen under the control of the probasin promoter, and spontaneously develop prostate cancer. We crossed TRAMP mice with liver IGF-deficient (LID) mice to produce LID-TRAMP mice, a mouse model of prostate cancer with low serum IGF-I, to allow us to study the effect of circulatory IGF-I levels on the development of prostate cancer. LID mice have a targeted deletion of the hepatic Igf1 gene but retain normal expression of Igf1 in extrahepatic tissues. Serum IGF-I and IGFBP-3 levels in LID and LID-TRAMP mice were measured using novel assays, which showed that they are approximately 10% and 60% of control L/L- mice, respectively. Serum growth hormone (GH) levels of LID-TRAMP mice were 3.5-fold elevated relative to L/L-TRAMP mice (P < 0.001), but IGFBP-2 levels were not different. Surprisingly, rates of survival, metastasis, and the ratio of genitourinary tissue weight to body weight were not significantly different between LID-TRAMP and L/L-TRAMP mice. There was also no difference in the pathologic stage of the prostate cancer between the two groups at 9 to 19 weeks of age. LID-TRAMP tumors displayed increased levels of GH receptors and increased Akt phosphorylation. These results are in striking contrast with the published model of the GH-deficient lit/lit-TRAMP, which has smaller tumors and improved survival, and indicate that the reduction in systemic IGF-I is not sufficient to inhibit prostate cancer tumor progression in the TRAMP model, which may require a reduction of GH levels as well.

Assessing the potential usefulness of IGF-related peptides and adiponectin for predicting disease risk

OBJECTIVE

Insulin-like growth factors (IGF), their binding proteins and adiponectin have been investigated as potential blood-based biomarkers for a variety of diseases. Before these circulating proteins can be considered as biomarkers, their variation within and between individuals and between published studies must be critically assessed. The purpose of this study was to use the D-value to predict the potential usefulness of IGF-related peptides and adiponectin as biomarkers for the diagnosis of colorectal cancer (CRC).

DESIGN

Intra- and inter-individual variation of total IGF-I and -II, IGF binding protein 1 (IGFBP-1), -2 and -3 and adiponectin, was examined in 10 healthy subjects over a 5 week period. This data was analysed in conjunction with previous publications to provide a D-value, which is a theoretical value that identifies the usefulness of the analyte individually and as a panel, as a biomarker for CRC.

RESULTS

A single measurement of total IGF-I and -II, and adiponectin provided a reproducible representation of their circulating concentrations. The D-value for total IGF-II and IGFBP-3 were 0.5 and 0.47, respectively, which corresponded to area under the curve (AUC) values of 64 and 63%. Combining these analytes into a panel only slightly improved the D-value to 0.63 (AUC was 67%).

CONCLUSIONS

Although serum levels of total IGF-I, total IGF-II and IGFBP-3 are stable and reproducible, the D-value calculations indicate that they have limited importance when used as biomarkers of CRC.

Correlations of dietary patterns with prostate health

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve alpha-methylacyl-CoA racemase activity (required for beta-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.

IGF-1 and IGFBP-3: Risk of prostate cancer among men in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial

IGF-1 and IGFBP-3 may influence risk of prostate cancer through their roles in cellular growth, metabolism and apoptosis, however, epidemiologic results have been inconsistent. The role of obesity in prostate cancer risk is not clearly understood, but hyperinsulinemia-related increases in bioactive IGF-1 levels, associated with obesity, could be a component of the relationship between the IGF-axis and prostate cancer. We conducted a nested case-control study in the prospective Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial to examine associations between IGF-1 and IGFBP-3 and risk of prostate cancer. A total of 727 incident prostate cancer cases and 887 matched controls were selected for this analysis. There was no clear overall association between IGF-1, IGFBP-3 and IGF-1:IGFBP-3 molar ratio (IGFmr) and prostate cancer risk, however, IGFmr was associated with risk in obese men (BMI > 30, p-trend = 0.04), with a greater than 2-fold increased risk in the highest IGFmr quartile (OR 2.34, 95% CI 1.10-5.01). Risk was specifically increased for aggressive disease in obese men (OR 2.80, 95% CI 1.11-7.08). In summary, our large prospective study showed no overall association between the insulin-like growth factor axis and prostate cancer risk, however, IGFmr was related to risk for aggressive prostate cancer in obese men.

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.

Lycopene supplementation elevates circulating insulin-like growth factor binding protein-1 and -2 concentrations in persons at greater risk of colorectal cancer

BACKGROUND

Higher circulating insulin-like growth factor I (IGF-I) concentrations have been related to a greater risk of cancer. Lycopene intake is inversely associated with cancer risk, and experimental studies have shown that it may affect the IGF system, possibly through an effect on IGF-binding proteins (IGFBPs).

OBJECTIVE

The objective of our study was to investigate the effect of an 8-wk supplementation with tomato-derived lycopene (30 mg/d) on serum concentrations of total IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3.

DESIGN

We conducted a randomized, placebo-controlled, double-blinded crossover study in 40 men and 31 postmenopausal women with a family history of colorectal cancer, a personal history of colorectal adenoma, or both.

RESULTS

Lycopene supplementation significantly (P = 0.01) increased serum IGFBP-1 concentrations in women (median relative difference between serum IGFBP-1 concentrations after lycopene supplementation and after placebo, 21.7%). Serum IGFBP-2 concentrations were higher in both men and women after lycopene supplementation than after placebo, but to a lesser extent (mean relative difference 8.2%; 95% CI: 0.7%, 15.6% in men and 7.8%; 95% CI: -5.0%, 20.6% in women). Total IGF-I, IGF-II, and IGFBP-3 concentrations were not significantly altered by lycopene supplementation.

CONCLUSIONS

This is the first study known to show that lycopene supplementation may increase circulating IGFBP-1 and IGFBP-2 concentrations. Because of high interindividual variations in IGFBP-1 and IGFBP-2 effects, these results should be confirmed in larger randomized intervention studies.

Serum Insulin-like Growth Factor (IGF)-I and IGF-Binding Protein-3 Concentrations and Prostate Cancer Risk: Results from the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Some studies suggest that elevated serum insulin-like growth factor (IGF)-I concentrations are associated with an increased risk of prostate cancer and, in particular, with an increased risk of advanced-stage prostate cancer.

METHODS

We analyzed the association between prediagnostic serum concentrations of IGF-I and IGF-binding protein-3 (IGFBP-3) and prostate cancer risk in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition. This study includes 630 incident prostate cancer cases and 630 matched control subjects. Odds ratios and their 95% confidence intervals (95% CI) were calculated for prostate cancer risk associated with increasing IGF-I and IGFBP-3 concentrations using conditional logistic regression.

RESULTS

The risk of total prostate cancer in the highest versus the lowest third of serum peptide concentration was 1.35 (95% CI, 0.99-1.82; Ptrend = 0.08) for IGF-I, 1.39 (95% CI, 1.02-1.89; Ptrend = 0.12) for the IGF-I residuals after adjusting for IGFBP-3, 1.22 (95% CI, 0.92-1.64; Ptrend = 0.38) for IGFBP-3, and 1.01 (95% CI, 0.74-1.37; Ptrend = 0.75) for the IGFBP-3 residuals after adjusting for IGF-I. There was no significant difference in the association of peptide hormones and prostate cancer by stage of disease, although the association of serum IGF-I concentration with risk was slightly stronger for advanced-stage disease; the odds ratio for the highest versus the lowest third was 1.65 (95% CI, 0.88-3.08; Ptrend = 0.21) for IGF-I and 1.76 (95% CI, 0.92-3.40; Ptrend = 0.11) for IGF-I adjusted for IGFBP-3.

CONCLUSIONS

In this large nested case-control study, serum IGF-I concentration is not strongly associated with prostate cancer risk, although the results are compatible with a small increase in risk, particularly for advanced-stage disease; no association for IGFBP-3 was observed.

The effects of sex steroid replacement therapy on an expanded panel of IGF-related peptides

BACKGROUND

Oral estrogen alone (EA) decreases concentrations of total IGF-I while increasing IGFBP-1, but data on other IGF-related peptides are inconsistent and/or sparse. Combined oral estrogen and progestin (EP) may have differential effects on IGF-related peptides dependent on its progestin-associated androgenic activity. The aim of this study was to clarify these relationships, as circulating IGF-related peptides are potential surrogates of predisposition to common chronic diseases.

DESIGN

Using an open-labelled cross-sectional design within a bowel cancer screening trial (aged 55-64 years), we determined total IGF-I, IGF-II, IGFBP-2 and IGFBP-3 in fasted serum from 210 healthy women and free IGF-I (by ultrafiltration), insulin, IGFBP-1 and IGFBP-1:IGF-I binary complex in a selected subset of 92 women. Unadjusted and adjusted (using generalized linear models) means were compared.

RESULTS

Among EA users, mean concentrations for total IGF-I (adjusted P=0.004) and free IGF-I (P<0.001) were reduced, whereas mean concentrations of IGFBP-1 (P=0.001) and binary complex (P=0.01) were increased compared with non-users. Taken as a whole group, EP use was not associated with differences in concentrations of IGF-related peptides, but on sub-group analyses, mean concentrations associated with the use of progestins with reduced androgenic activity reflected the use of EA. By contrast, mean IGFBP-2 concentrations were significantly reduced among both EA (P=0.008) and EP (P=0.002) users, irrespective of androgenic activity. Neither EA nor EP influenced mean concentrations of IGF-II, insulin and IGFBP-3.

CONCLUSIONS

The uses of oral sex steroid replacements are associated with significant changes in several IGF-related analytes in a preparation-specific manner, suggesting different regulatory mechanisms. However, the directions of these changes do not fit simple correlative models of predisposition to common diseases.

Plasma C-peptide, insulin-like growth factor-I, insulin-like growth factor binding proteins and risk of colorectal cancer in a nested case-control study: the Japan public health center-based prospective study

The physical inactivity and obesity involved in hyperglycemia and hyperinsulinemia is supposed to lead to an increased bioavailability of insulin-like growth factor-I (IGF-I). The carcinogenic effect of IGF-I may be influenced by IGF binding proteins. We investigated the association between plasma levels of C-peptide, a surrogate biomarker of insulin, IGFBP-1, IGF-I or IGFBP-3, and the risk of colorectal cancer in a nested case-control study. During an 11.5-year follow-up, 375 newly diagnosed colorectal cancers were identified in a cohort of 38,373 adults who had returned the baseline questionnaire and provided blood samples. Two matched-controls for each case were selected from the cohort. The odds ratio (OR) of colorectal cancer for plasma levels of each protein was estimated using the conditional logistic regression model adjusted for potential confounding factors. We observed a statistically significant association of plasma C-peptide with colorectal cancer only in men. The ORs were 1.0, 2.3, 2.8 and 3.2 along with quartiles (p trend, 0.0072). The association was stronger in colon cancer (p trend, 0.025) than in rectal cancer (p trend, 0.24). Other peptides were not associated with the risk in either men or women. The results did not change when repeatedly analyzed by tumor invasion levels, tumor sites or follow-up periods. In conclusion, a higher plasma C-peptide may indicate a subsequent risk of colorectal cancer in Japanese men.