The significance of serum levels of insulin-like growth factor-1 in patients with prostate cancer

Are plasma Insulin-Like Growth Factor I (IGF-I) and Igf-Binding Protein 3 (Igfbp-3) Useful Markers of Prostate Cancer?

Increased concentrations of insulin-like growth factor I (IGF-I) and decreased insulin-like growth factor binding protein 3 (IGFBP-3) in serum have been proposed as markers of prostate cancer (CaP). The evidence for this, however, is contradictory. We assayed serum for IGF-I, IGFBP-3 and prostate-specific antigen (PSA) in patients with CaP and benign prostatic hyperplasia (BPH) and in healthy controls (HC). The mean ± SD concentration of IGF-I in CaP (98.3 ± 39.3 ng/mL; n=15) was lower than in BPH (119 ± 31.1 ng/mL; n=24) and HC (119 ± 36.1 ng/mL; n=46), but the differences between the three groups were not statistically significant (p>0.05). The mean IGFBP-3 concentrations in CaP (2691 ± 1105 ng/mL; n=16; p=0.029) and BPH (2618 ± 816 ng/mL; n= 26; p=0.006) patients were significantly lower than that of the HC (3119 ± 618 ng/mL; n=59), but the difference between the two groups of patients was not significant (p>0.05). PSA concentrations in CaP (median=80.8 ng/mL; n=25) were significantly higher than those in BPH (median=8.6 ng/mL; n=39) (p<0.001). Ninety-six percent of CaP and 72% of BPH patients had PSA concentrations >4.0 ng/mL; the proportions of patients with concentrations exceeding 20 ng/mL were 76% and 10%, respectively. We conclude that IGF-I and IGFBP-3 are inferior to PSA for CaP detection.

Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis

PURPOSE

To establish whether the association between milk intake and prostate cancer operates via the insulin-like growth factor (IGF) pathway (including IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3).

METHODS

Systematic review, collating data from all relevant studies examining associations of milk with IGF, and those examining associations of IGF with prostate cancer risk and progression. Data were extracted from experimental and observational studies conducted in either humans or animals, and analyzed using meta-analysis where possible, with summary data presented otherwise.

RESULTS

One hundred and seventy-two studies met the inclusion criteria: 31 examining the milk-IGF relationship; 132 examining the IGF-prostate cancer relationship in humans; and 10 animal studies examining the IGF-prostate cancer relationship. There was moderate evidence that circulating IGF-I and IGFBP-3 increase with milk (and dairy protein) intake (an estimated standardized effect size of 0.10 SD increase in IGF-I and 0.05 SD in IGFBP-3 per 1 SD increase in milk intake). There was moderate evidence that prostate cancer risk increased with IGF-I (Random effects meta-analysis OR per SD increase in IGF-I 1.09; 95% CI 1.03, 1.16; n = 51 studies) and decreased with IGFBP-3 (OR 0.90; 0.83, 0.98; n = 39 studies), but not with other growth factors. The IGFBP-3 -202A/C single nucleotide polymorphism was positively associated with prostate cancer (pooled OR for A/C vs. AA = 1.22; 95% CI 0.84, 1.79; OR for C/C vs. AA = 1.51; 1.03, 2.21, n = 8 studies). No strong associations were observed for IGF-II, IGFBP-1 or IGFBP-2 with either milk intake or prostate cancer risk. There was little consistency within the data extracted from the small number of animal studies. There was additional evidence to suggest that the suppression of IGF-II can reduce tumor size, and contradictory evidence with regards to the effect of IGFBP-3 suppression on tumor progression.

CONCLUSION

IGF-I is a potential mechanism underlying the observed associations between milk intake and prostate cancer risk.

Insulin/Insulin-Like Growth Factor-1 Pathway in Barrett's Carcinogenesis

OBJECTIVES

Obesity-associated carcinogenesis is postulated to be mediated through the proliferative actions of insulin and the insulin-like growth factor (IGF) family. The aim of this study was to determine whether the insulin/IGF-1 pathway is involved in the sequential progression from metaplastic Barrett's esophagus (BE) to dysplasia to esophageal adenocarcinoma (EAC).

METHODS

Fasting serum levels of insulin, glucose, IGF-1, insulin growth factor binding protein-1 (IGFBP1), and IGFBP3 were measured in 44 non-dysplastic, 9 low-grade dysplasia (LGD), 12 high-grade dysplasia (HGD), and 10 EAC subjects. Immunohistochemistry was performed on paraffin-embedded tissue derived from BE cases using rabbit monoclonal antibodies to p-mammalian target of rapamycin (mTOR) and p-AKT, mouse monoclonal antibody to Ki-67, and rabbit polyclonal antibody to p-insulin receptor substrate 1 (IRS1).

RESULTS

Nineteen of 44 (43.2%) BE, 5/9 (55%) LGD, 8/12 (66.7%) HGD and EAC 7/10 (70%) cases showed strong staining for p-IRS1. A significantly higher proportion of HGD/EAC subjects showed p-IRS1 staining when compared with BE/LGD subjects, 63.6% vs. 41.5%, P<0.05. p-IRS1 immunostaining was moderately correlated with strong immunostaining of the downstream mediators p-AKT and p-mTOR (Spearman correlation coefficient=0.167 and 0.27 for p-IRS1/p-AKT and for p-IRS1/p-mTOR, respectively) and the proliferation marker Ki-67 (Spearman correlation coefficient=0.20, P=0.09). However, systemic levels of insulin, IGF-1, or IGF-2 were not associated with tissue immunostaining of p-IRS1.

CONCLUSIONS

Activation of the insulin/IGF-1 pathway in BE may be associated with cellular proliferation and appears to have a role in the progression from metaplasia to cancer. The activation of the insulin/IGF-1 pathway at the tissue level is likely complex and does not have a simple association with systemic measures of insulin or IGF-1.

Serum levels of IGF-I and BRCA penetrance: a case control study in breast cancer families

High serum levels of insulin-like growth factor I (IGF-I) are associated with an increased risk of sporadic breast cancer (BC). The aim of the present work is to evaluate the association between IGF-I and hereditary BC risk, using a case-control approach. The work represents an "ad interim" cross-sectional analysis of an ongoing study with a prospective design whose aim is to recruit a cohort of women belonging to high genetic risk families to test potential modulators of penetrance and prognosis. The odd of exposure to high serum IGF-I levels among women with a previous diagnosis of BC ("cases") was compared with the odd among unaffected "controls". The odds ratio (OR) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression, controlling for confounders. We analysed 308 women (209 cases and 99 controls) at high genetic risk of BC. The adjusted OR of BC for the upper tertile of serum IGF-I versus the lowest one was 3.5 (95%CI 1.4-8.8). Excluding from the analysis 64 women under current Tamoxifen or GnRH analogues treatment, the adjusted OR of BC became 3.7 (95%CI 1.4-9.9). The association became stronger restricting the analysis to the 161 women (97 cases and 64 controls) with a proven BRCA mutation. If confirmed by a prospective approach, the association between IGF-I and familial BC will open further options for reducing BC risk in susceptible women.

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.

Disruption of growth hormone signaling retards prostate carcinogenesis in the Probasin/TAg rat

We asked whether down-regulation of GH signaling could block carcinogenesis in the Probasin/TAg rat, a model of aggressive prostate cancer. The Spontaneous Dwarf rat, which lacks GH due to a mutation (dr) in its GH gene, was crossed with the Probasin/TAg rat, which develops prostate carcinomas at 100% incidence by 15 wk of age. Progeny were heterozygous for the TAg oncogene and homozygous for either the wild-type GH gene (TAg/Gh(+/+)) or the dr mutation (TAg/Gh(dr/dr)). Prostate tumor incidence and burden were significantly reduced, and tumor latency was delayed in TAg/Gh(dr/dr) rats relative to TAg/Gh(+/+) controls. At 25 wk of age, loss of GH resulted in a 20 and 80% decrease in the area of microinvasive carcinoma in the dorsal and lateral lobes, respectively. By 52 wk of age, invasive prostate adenocarcinomas were observed in all TAg/Gh(+/+) rats, whereas the majority of TAg/Gh(dr/dr) did not develop invasive tumors. Suppression of carcinogenesis could not be attributed to alterations in prostate expression of TAg or androgen receptor or changes in serum testosterone levels. As carcinogenesis progressed in TAg/Gh(+/+) rats, prostate GHR mRNA and protein expression increased significantly, but prostate IGF-I receptor mRNA and protein levels dropped. Furthermore, serum IGF-I and prostate IGF-I levels did not change significantly over the course of carcinogenesis. These findings suggest that GH plays a dominant role in progression from latent to malignant prostate cancer driven by the powerful probasin/TAg fusion gene in rats and suggest that GH antagonists may be effective at treating human prostate cancer.

Serum insulin-like growth factor I/free prostate specific antigen (IGF-I/fPSA) ratio enhances prostate cancer detection in men with total PSA 4.0-10.0 ng/ml

BACKGROUND

Recent studies have suggested that IGF-I and IGFBP-3, in combination with PSA, may enhance PCa detection. This study was to investigate the use of serum IGF-I and IGFBP-3, and their combinations with prostate volume and fPSA in enhancing the discriminatory diagnosis of PCa in men with tPSA of 4.0-10.0 ng/ml.

METHODS

Serum IGF-I and IGFBP-3 were determined by ELISA from 586 men with tPSA between 4.0 and 10.0 ng/ml. Of them, 281 were diagnosed with PCa and 305 without. ROC, univariate and multivariate logistic regression analyses were performed to evaluate the predictive performance of those parameters.

RESULTS

IGF-I, IGFD, IGF-I/fPSA, and IGFBP-3/fPSA were significantly higher in PCa cases than benign controls, whereas the differences of IGFBP-3 and IGFBPD were statistically insignificant between the two groups, respectively. The AUC values indicated enhanced performance of IGF-I/fPSA ratio (AUC = 0.753) in PCa detection compared with the currently used f/tPSA (AUC = 0.689). Multivariate logistic regression confirmed the observed relationships and identified IGF-I/fPSA as independent factor in PCa presence.

CONCLUSION

Our data show that IGF-I/fPSA as a promising marker can enhance PCa detection in ambiguous cases often found in the tPSA between 4.0 and 10.0 ng/ml.

Growth hormone treatment and cancer risk

Increasing numbers of children receive growth hormone (GH) to treat a range of growth disorders, including those rendered GH deficient (GHD) by tumors or their treatment. Young persons with persistent growth hormone deficiency (GHD) and adults with severe GHD are also eligible to receive GH treatment. As in vitro and in vivo studies and epidemiologic observations provide some evidence that the GH--insulin like growth factor-I (IGF-I) axis is associated with tumorigenesis, it is important to assess, in practice, the incidence of tumors related to GH treatment. Reassuringly, surveillance studies in large cohorts of children and in smaller cohorts of adults indicate that GH is not associated with an increased incidence of tumor occurrence or recurrence. Nevertheless, all children who have received GH, in particular cancer survivors and those receiving GH in adulthood, should be in surveillance programs to assess whether an increased rate od late-onset and rare tumours may occur.

Insulin-Like Growth Factor (IGF) family and prostate cancer

There is abundant in vitro, animal and epidemiologic evidence to suggest that the Insulin-Like Growth Factor (IGF) family is a multi-component network of molecules which is involved in the regulation of both physiological and pathological growth processes in prostate. The IGF family plays a key role in cellular metabolism, differentiation, proliferation, transformation and apoptosis, during normal development and malignant growth. This family also seem essential in prostate cancer bone metastases, angiogenesis and androgen-independent progression. Therapeutic alternatives in men with progressive prostate cancer after androgen ablation are very limited. More effective therapies are needed for these patients. Pharmacologic interventions targeting the IGF family are being devised. Such strategies include reduction of IGF-I levels (growth hormone-releasing hormone antagonists, somatostatin analogs), reduction of functional IGF-I receptor levels (antisense oligonucleotides, small interfering RNA), inhibition of IGF-IR and its signalling (monoclonal antibodies, small-molecule tyrosine kinase inhibitors) and Insulin-Like Growth Factor Binding Proteins.

Disruption of growth hormone signaling retards early stages of prostate carcinogenesis in the C3(1)/T antigen mouse

Recent epidemiological studies suggest that elevated serum titers of IGF-I, which are, to a large degree, regulated by GH, are associated with an increase in prostate cancer risk. The purpose of the current study was to develop the first animal models to directly test the hypothesis that a normal, functional GH/IGF-I axis is required for prostate cancer progression. The GH receptor (GHR) gene-disrupted mouse (Ghr(-/-)), which has less than 10% of the plasma IGF-I found in GHR wild-type mice, was crossed with the C3(1)/T antigen (Tag) mouse, which develops prostatic intraepithelial neoplasia driven by the large Tag that progress to invasive prostate carcinoma in a manner similar to the process observed in humans. Progeny of this cross were genotyped and Tag/Ghr(+/+) and Tag/Ghr(-/-) mice were killed at 9 months of age. Seven of eight Tag/Ghr(+/+) mice harbored prostatic intraepithelial neoplasia lesions of various grades. In contrast, only one of the eight Tag/Ghr(-/-) mice exhibited atypia (P < 0.01, Fischer's exact test). Disruption of the GHR gene altered neither prostate androgen receptor expression nor serum testosterone titers. Expression of the Tag oncogene was similar in the prostates of the two mouse strains. Immunohistochemistry revealed a significant decrease in prostate epithelial cell proliferation and an increase in basal apoptotic indices. These results indicate that disruption of GH signaling significantly inhibits prostate carcinogenesis.

Prostate cancer risk and IRS1, IRS2, IGF1, and INS polymorphisms: strong association of IRS1 G972R variant and cancer risk

BACKGROUND

As cellular proliferation is central to the carcinogenic process, pathways that regulate proliferation may be important. Therefore, genes in the insulin and the insulin-like growth factor signaling pathways are plausible candidates for susceptibility genes for prostate cancer. We hypothesized that functional polymorphisms in INS, IRS1, IRS2, and IGF1 may be associated with prostate cancer.

METHODS

We studied 199 incident prostate cancer cases and 267 age-matched controls. Genotyping was performed for the INS +1127 Ins-PstI, IRS1 G972R, IRS2 G1079D, and the IGF1 CA-repeat polymorphisms. Outcomes were prostate cancer, Gleason score, and AJCC stage.

RESULTS

The IRS1 G972R GR/RR genotypes were associated with a significant 2.8-fold increased risk for prostate cancer (95% CI 1.5-5.1, P = 0.0007). The other variants were not significantly associated with prostate cancer. The IRS1 G972R GR/RR genotypes were also significantly associated with more advanced Gleason score (P = 0.001) and AJCC stage (P = 0.004).

CONCLUSIONS

These results support a role of the insulin and/or insulin-like growth factor pathways in the etiology of prostate cancer.

Putative role of serum insulin-like growth factor–1 (IGF-1) and IGF binding protein-3 (IGFBP-3) levels in the development of prostate cancer in Arab men

INTRODUCTION

The incidence of clinical prostate cancer in the Arab population is among the lowest in the world. High serum IGF-1 level has been implicated as a possible risk factor for the development of prostate cancer in Caucasians. The purpose of this study was to determine serum IGF-1 and IGFBP-3 levels in healthy Arab men and in Arab men with newly diagnosed benign prostatic hyperplasia (BPH) and prostate cancer, and to compare these values with values reported in Caucasians.

PATIENTS AND METHODS

Subjects were recruited in two groups: (a) indigenous, healthy Arab men aged 15-90 y (n = 383); (b) Arab men with newly diagnosed prostate cancer (n = 30) or BPH (n = 40). Blood was obtained from fasting patients and volunteers, between 8:00 a.m. and 12:00 noon. The serum concentrations of IGF-1 and IGFBP-3 were determined using Immunoradiometric assay (IRMA) kits.

RESULTS

As in Caucasians, serum IGF-1 and IGFBP-3 levels declined with age in Arab men. The mean +/- s.d. of serum IGF-1 levels in healthy Arab men in the age group 15-20, 51-60, 61-70 y were lower (376.2 +/- 153.2, 134.9 +/- 105.7 and 89.6 +/- 48.4 ng/ml, respectively), compared to values reported for similarly aged Caucasians. Arab men with newly diagnosed prostate cancer had significantly higher serum IGF-1 level (P < 0.01) and lower IGFBP-3 levels (P < 0.01) compared to age-matched Arabs without the disease.

CONCLUSIONS

Arab men have lower serum IGF-1 levels compared to Caucasians and this may be an important factor in the explanation of the low incidence of prostate cancer in the Arab population.

IGF1 (CA)19 Repeat and IGFBP3 -202 A/C Genotypes and the Risk of Prostate Cancer in Black and White Men

We investigated the relationship between the insulin-like growth factor-1 (IGF1) cytosine-adenine repeat (CA)(19) polymorphism located upstream of the gene's transcription start site, the insulin-like growth factor binding protein-3 (IGFBP3) -202 A/C promoter region polymorphism, and prostate cancer risk in Black and White men. Study subjects were U.S. veterans ages 41 to 75 years identified at the Durham Veterans Administration Medical Center over a 2.5-year period. Controls (n = 93) were frequency matched to cases (n = 100) based on race (Black or White) and age. Multivariable unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for the associations between the polymorphisms and prostate cancer risk. For Blacks and Whites combined, an inverse association between prostate cancer and being homozygous for the most common IGF1 repeat allele, (CA)(19), (adjusted OR, 0.3; 95% CI, 0.1-0.7) was observed. Similar associations were noted for both Blacks (OR, 0.2; 95% CI, 0.0-0.8) and Whites (OR, 0.4; 95% CI, 0.1-1.6) separately. No statistically significant associations between the IGFBP3 C allele and prostate cancer were noted for Blacks (adjusted OR, 2.3; 95% CI, 0.8-6.2) or Whites (OR, 1.0; 95% CI, 0.3-3.1). The prevalence of the homozygous IGF1 (CA)(19) genotype was much lower in Black controls (21%) than White controls (46%), which may, in part, explain the increased prostate cancer incidence in Black versus White men. Further research is needed to confirm these findings.

Insulin-like growth factor binding protein 2: an androgen-dependent predictor of prostate cancer survival

BACKGROUND

Evidence suggests that the insulin-like growth factor (IGF) family is important in prostate cancer. We evaluate the ability of IGF markers to predict biochemical recurrence-free survival (bRFS) following radical prostatectomy (RRP).

METHODS

Preoperative sera from 141 patients undergoing RRP were analyzed for IGF-I, IGFBP-1, IGFBP-2 and IGFBP-3. A multivariate Cox model was created to assess the ability of these markers to predict bRFS. Preoperative covariables included: biopsy Gleason score, clinical TNM stage, serum PSA and neoadjuvant hormonotherapy. Kaplan-Meier curves were stratifying by IGF cutpoints (determined by ROC analysis) and hormonotherapy status.

RESULTS

Average follow-up was 6.92 years, median PSA was 6.9 ng/ml and 85.1% of patients had cT2NxM0 disease. 49 patients experienced a PSA failure. Average levels of IGF-I, IGFBP-1, IGFBP-2 and IGFBP-3 were 156.5 ng/ml, 48.1 ng/ml, 396.8 ng/ml and 3303.7 ng/ml, respectively. IGFBP-2 was an independent predictor of PSA failure. Patients treated with neoadjuvant ADT (n=71) and whom had high IGFBP-2 levels experienced a 5-year bRFS that was better than those with low IGFBP-2 levels (77.7% vs. 53.3%). Patients without neoadjuvant ADT whom had high IGFBP-2 levels had a 5-year bRFS that was worse than those with low IGFBP-2 levels (64.5% vs. 82.7%).

CONCLUSIONS

Preoperative IGFBP-2 predicts post-radical prostatectomy bRFS and is independent of stage, Gleason score and PSA. Increased IGFBP-2 is associated with better survival in patients with neoadjuvant hormonotherapy but worse survival in those without, suggesting a dramatic switch in function of this protein dependent on the presence or absence of androgens.

Circulating free insulin-like growth factor (IGF)-I, total IGF-I, and IGF binding protein-3 levels do not predict the future risk to develop prostate cancer: results of a case-control study involving 201 patients within a population-based screening with a 4-year interval

Recent studies have reported that serum IGF-I levels in the highest quartile of the normal range and IGF binding protein-3 (IGFBP-3) in the lowest quartile of the normal range are associated with an increased risk of future prostate cancer and/or presence of prostate cancer. It has also been suggested that the measurement of circulating total IGF-I concentrations might be a useful tool for the early detection of prostate cancer in men with moderately increased prostate-specific antigen (PSA) levels. To determine whether circulating free IGF-I, total IGF-I, and IGFBP-3 levels can predict future prostate cancer risk, we prospectively studied prostate cancer characteristics in a cohort of men during two rounds (mean interval, 4 yr) of a population-based screening study for prostate cancer. Two hundred one prostate cancer cases were detected at the second-round screening (aged 55-70 yr), and all these subjects were enrolled in the case group for the present study. Prostate cancer had been confirmed by biopsy in all cases. These 201 subjects were matched with the 201 nonprostate cancer cases by age, serum PSA range at the first-round screening (PSA < 2 ng/ml, n = 67; PSA = 2-3 ng/ml, n = 67; and PSA = 3-4 ng/ml, n = 67), and residence area. At baseline, total IGF-I, free IGF-I, and IGFBP-3 levels and prostate volume of cases with prostate cancer were not different from those of healthy controls. PSA velocity was significantly different between cases and controls (P < 0.001).Stepwise forward logistic regression analysis showed that only PSA levels at baseline and PSA at round 2 after 4 yr are good predictors of prostate cancer, whereas total IGF-I, free IGF-I, and IGFBP-3 did not predict the development of prostate cancer. Only one of the 201 subjects with prostate cancer had metastases. Within the subjects with prostate cancer, there were no differences of IGF-I parameters with different tumor node metastasis categories and/or Gleason scores. Our study suggests that the measurement of serum IGF-I and/or IGFBP-3 concentrations in addition to PSA does not improve the identification of men at high risk to develop early stages of prostate cancer. In addition, our results indicate that the endocrine IGF-I system is not directly involved in the growth of the early stages of prostate cancer.

Dietary and Lifestyle Correlates of Plasma Insulin-Like Growth Factor-I (IGF-I) and IGF Binding Protein-3 (IGFBP-3): The Multiethnic Cohort

High circulating concentration of insulin-like growth factor-I (IGF-I) and low circulating concentration of IGF binding protein-3 (IGFBP-3) have been associated with increased risk for breast, prostate, and colorectal cancers. Building on previous work in the Multiethnic Cohort (MEC) showing significant differences in IGF-I levels across racial/ethnic groups, we investigated which lifestyle and dietary factors are associated with levels of IGF-I and IGFBP-3 in a random sample of 1,000 MEC participants, which included Native Hawaiian, African American, Japanese, Latino, and White men and women. Crude analyses confirmed the existence of differences in protein levels with race/ethnicity, sex, age, and body size. Reproductive, physical activity, smoking, and diet variables had less consistent effects. In multivariate analyses, IGF-I levels were lower and IGFBP-3 were higher in females versus males. IGF-I and IGFBP-3 declined with increasing age in both genders. Women in the highest quartile of body mass index showed depressed IGF-I and IGFBP-3 levels; in men, height was significantly positively associated with both proteins. In women, alcohol was directly associated with IGFBP-3. Both proteins were lowest among female Latinos. IGF-I was highest among female African Americans. In men, IGFBP-3 was lowest among African Americans. Overall, although these factors were statistically significant determinants of IGF-related protein levels, they did not explain much of the variation in these levels. A positive correlation was found between IGF-I levels (ng/mL) and colon cancer incidence rates (per 100,000) within the MEC by race/ethnicity for both sexes but not for either breast or prostate cancer.

High levels of circulating insulin-like growth factor-I increase prostate cancer risk: a prospective study in a population-based nonscreened cohort

PURPOSE

Insulin-like growth factor-I (IGF-I) stimulates proliferation and inhibits apoptosis in prostate cancer cells, and IGF-I has been associated with increased prostate cancer risk in some, but not all, epidemiologic studies.

SUBJECTS AND METHODS

We extended our previous case-control study nested in the Northern Sweden Health and Disease Cohort, a population-based cohort from a region where little prostate specific antigen (PSA) screening is done. Levels of IGF-I and IGF binding protein-3 (IGFBP-3) were measured in prediagnostic blood samples from a total of 281 men who were subsequently diagnosed with prostate cancer after recruitment (median, 5 years after blood collection) and from 560 matched controls.

RESULTS

Logistic regression analyses showed increases in prostate cancer risk with increasing plasma peptide levels, up to an odds ratio (OR) for top versus bottom quartile of IGF-I of 1.67 (95% CI, 1.02 to 2.71; Ptrend = .05), which was attenuated after adjustment for IGFBP-3 to an OR of 1.47 (95% CI, 0.81 to 2.64; P (trend) =.32). For men younger than 59 years at recruitment, OR for top versus bottom quartile of IGF-I was 4.12 (95% CI, 1.01 to 16.70; Ptrend = .002), which was significantly stronger than for men older than 59 years (P (interaction) = .006). For men with advanced cancer, OR for top versus bottom quartile of IGF-I was 2.87 (95% CI, 1.01 to 8.12; Ptrend = .10).

CONCLUSION

Our data add further support for IGF-I as an etiologic factor in prostate cancer and indicate that circulating IGF-I levels measured at a comparatively young age may be most strongly associated with prostate cancer risk.

Cancer Risk Following Growth Hormone Use in Childhood

The therapeutic use of growth hormone (GH) has caused concern, as it is anabolic and mitogenic, and its effector hormone, insulin-like growth factor (IGF)-I is anti-apoptotic. As both hormones can cause proliferation of normal and malignant cells, the possibility that GH therapy may induce cancer, increase the risk of tumour recurrence in those previously treated for a malignancy, or increase the risk of cancer in those with a predisposition, has resulted in concerns over its use. There are theoretical and epidemiological reasons that suggest GH and IGF-I may be important in tumour formation and proliferation. Malignant tumours have been induced in animals exposed to supraphysiological doses of GH, whereas hypophysectomy appears to protect animals from carcinogen-induced neoplasms. In vitro, proliferation and transformation of normal haemopoetic and leukaemic cells occurs with supraphysiological doses of GH, but not with physiological levels. IGF, IGF binding proteins (IGFBP) and IGFBP proteases influence the proliferation of cancer cells in vitro; however, GH is probably not involved in this process. Epidemiological studies have suggested an association between levels of IGF-I and cancer, and an inverse relationship between IGFBP-3 and cancer; however, these associations have been inconsistent. A number of studies have been undertaken to determine the risk of the development of cancer in children treated with GH, either de novo, or the recurrence of cancer in those previously treated for a malignancy. Despite early concerns following a report of a cluster of cases of leukaemia in recipients of GH, there appears to be no increased risk for the development of leukaemia in those treated with GH unless there is an underlying predisposition. Even in children with a primary diagnosis of cancer, subsequent GH use does not appear to increase the risk of tumour recurrence. However, a recent follow-up of pituitary GH recipients has suggested an increase in colorectal cancer. In addition, follow-up of oncology patients has suggested an increase in second neoplasms in those who also received GH therapy. These studies emphasise the importance of continued surveillance both internationally with established databases and also nationally through single-centre studies.

Serum insulin-like growth factor (IGF)-1 and IGF-binding protein-3 do not correlate with Gleason score or quantity of prostate cancer in biopsy samples

OBJECTIVE

To examine the relationship of serum insulin-like growth factor (IGF)-1 and IGF binding protein-3 (IGFBP-3) with histological cancer characteristics in men undergoing transrectal ultrasonography (TRUS)-guided biopsy.

PATIENTS AND METHODS

Patients (652), with either an elevated serum prostate-specific antigen level or an abnormal digital rectal examination, were initially evaluated by TRUS and sextant prostatic needle biopsy. Blood was drawn before biopsy, serum extracted and stored frozen until IGF-1 and IGFBP-3 were measured. In all, 241 patients had prostate cancer (37%) and were included in this study. The number of positive biopsies, the volume of tumour in each positive biopsy and the Gleason score were recorded.

RESULTS

Of the 241 patients, 37 had five or six positive biopsies (from six), 128 had two to four and 76 had one. Serum IGF-1 did not correlate with the number of positive biopsies, with means of 176.7, 178.3 and 164.4 ng/mL, respectively (P = 0.3), while the mean IGFBP-3 was 2695, 2795 and 2572 ng/mL, respectively (P = 0.09). The additive percentiles of tumour volume in positive biopsies were assessed for each patient but serum IGF-1 and IGFBP-3 did not correlate (P = 0.7 and 0.9, respectively). In all, 92 patients had a Gleason score of < 7, 80 a score of 7 and 69 a score of > 7; the mean (sd) IGF-1 levels for the three groups were 181 (39), 174.6 (35) and 176 (26) ng/mL, and the mean IGFBP-3 2798 (240), 2735 (284) and 2647 (221) ng/mL, respectively, none of the differences being statistically significant.

CONCLUSIONS

Serum IGF-1 and IGFBP-3 do not correlate with quantity of cancer or Gleason score in biopsy samples from patients with prostate cancer.

The role of nutrition in preventing prostate cancer: a review of the proposed mechanism of action of various dietary substances

BACKGROUND

Dietary modifications to prevent prostate cancer (PCa) continue to gain attention as research demonstrates that various dietary nutrients/supplements are related to decreased risk of developing prostate cancer (PCa). Several studies have focused on the antioxidant and nonantioxidant effects of various dietary substances in the prevention of PCa. Research into the mechanisms by which PCa is prevented, or its disease severity is reduced by dietary micronutrients and vitamins continues to enrich our understanding of the mechanisms by which PCa is initiated and progresses.

METHODS

We reviewed the literature on dietary nutrients with antioxidant properties that have been shown to have a positive effect in reducing the incidence or preventing the occurrence of PCa including carotenoids (e.g., lycopene), retinoids (e.g., vitamin A), vitamin E, vitamin C, selenium, and polyphenols. Other nutrients examined included vitamin D and calcium.

RESULTS

Many dietary micronutrients have demonstrated significant and complex effects on PCa cell proliferation, differentiation, and signaling related to the initiation, progression, and regression of PCa.

CONCLUSION

Understanding the mechanisms by which various dietary nutrients exert their effects on PCa may make it possible to design effective drugs for treating PCa and to promote better nutrition and lifestyle changes in those at risk for PCa.

Growth hormone-releasing hormone (GHRH) antagonists inhibit the proliferation of androgen-dependent and -independent prostate cancers

The antiproliferative effects of an antagonist of growth hormone-releasing hormone (GHRH) JV-1-38 were evaluated in nude mice bearing s.c. xenografts of LNCaP and MDA-PCa-2b human androgen-sensitive and DU-145 androgen-independent prostate cancers. In the androgen-sensitive models, JV-1-38 greatly potentiated the antitumor effect of androgen deprivation induced by surgical castration, but was ineffective when given alone. Thus, in castrated animals bearing MDA-PCa-2b cancers, the administration of JV-1-38 for 35 days virtually arrested tumor growth (94% inhibition vs. intact control, P < 0.01; and 75% vs. castrated control, P < 0.05). The growth of LNCaP tumors was also powerfully suppressed by JV-1-38 combined with castration (83% inhibition vs. intact control, P < 0.01; and 68% vs. castrated control, P < 0.05). However, in androgen-independent DU-145 cancers, JV-1-38 alone could inhibit tumor growth by 57% (P < 0.05) after 45 days. In animals bearing MDA-PCa-2b and LNCaP tumors, the reduction in serum prostate-specific antigen levels, after therapy with JV-1-38, paralleled the decrease in tumor volume. Inhibition of MDA-PCa-2b and DU-145 cancers was associated with the reduction in the expression of mRNA and protein levels of vascular endothelial growth factor. The mRNA expression for GHRH receptor splice variants was found in all these models of prostate cancer. Our results demonstrate that GHRH antagonists inhibit androgen-independent prostate cancers and, after combination with androgen deprivation, also androgen-sensitive tumors. Thus, the therapy with GHRH antagonist could be considered for the management of both androgen-dependent or -independent prostate cancers.

Insulin-like growth factor-1 and insulin-like growth factor binding protein-3 for prostate cancer detection in patients undergoing prostate biopsy

PURPOSE

Laboratory and epidemiological studies suggest that high circulating insulin-like growth factor (IGF)-1 and low IGF binding protein-3 are associated with increased prostate cancer risk. However, the usefulness of serum IGF-1 or IGF binding protein-3 for predicting pathology results in men undergoing prostate biopsy is unclear. We examined the relationships of serum IGF-1, IGF binding protein-3 and the results of prostate biopsy.

MATERIALS AND METHODS

A total of 652 consecutive patients with elevated serum prostate specific antigen (PSA) or abnormal digital rectal examination who were referred for transrectal ultrasound sextant prostate needle biopsy underwent blood sampling before biopsy. PSA, free PSA, IGF-1 and IGF binding protein-3 were measured. There were 244 men (37.4%) with cancer and 408 controls with benign conditions.

RESULTS

Mean IGF-1 plus or minus SD in the cancer and control groups was 176.1 +/- 58.3 and 178.7 +/- 54.7 ng./ml., respectively (p = 0.57). Mean IGF binding protein-3 in the cancer and control groups was 2,724 +/- 647 and 2,673 +/- 589 ng./ml., respectively (p = 0.3). Adjustment for age and PSA showed significantly lower IGF-1 in cancer cases, while IGF binding protein-3 was not significant. ROC values were significantly higher for free-to-total PSA and PSA than for crude and age adjusted IGF-1 and IGF binding protein-3.

CONCLUSIONS

Our data indicate that serum IGF-1 or IGF binding protein-3 does not predict the results of prostate biopsy in men with elevated PSA or abnormal digital rectal examination. This finding implies that while there is evidence that the IGF-1 level is a risk factor for prostate cancer, neither IGF-1 nor IGF binding protein-3 can be used as a tumor marker for this disease.

Serum levels of insulin-like growth factor-1 and insulin-like growth factor-1 binding proteins after radical prostatectomy

PURPOSE

Elevated serum levels of insulin-like growth factor-1 (IGF-1) have been consistently shown to be a risk factor for prostate cancer. Alterations in serum IGF-1 binding proteins 1 to 3 have also been associated with prostate cancer risk. A potentially important complication in these studies is that prostate tissue, perhaps especially malignant prostate tissue, may secrete IGF-1 and its binding proteins into serum. In fact, it is possible that altered levels of these proteins observed in subjects at risk for prostate cancer are the result of prostate cancer rather than related to its cause.

MATERIALS AND METHODS

The contribution of prostate cancer to serum levels of IGF-1 and IGF-1 binding proteins was determined by analyzing serum samples from 86 patients with prostate cancer 2 weeks before and 8 weeks after radical prostatectomy. Preoperative and postoperative values for IGF-1 and its 3 major binding proteins were analyzed using univariate and multivariate analysis models.

RESULTS

On univariate analysis significant increases and not decreases in IGF-1, IGF binding protein-1 and 3 were observed after prostatectomy. On multivariate analysis a significant post-prostatectomy increase was observed for IGF-1 binding proteins 1 and 3 but the increase in IGF-1 was not significant.

CONCLUSIONS

Increased levels of IGF-1 and IGF-1 binding proteins were unexpected after prostatectomy. This result makes it extremely unlikely that secretion from the prostate, even if it contains cancer, affects serum levels of these proteins. The implication of these findings is that endocrine production of IGF-1 is a factor in prostate cancer risk. Therefore, strategies to lower serum IGF-1 may be potentially useful.

IGFs and IGFBPs: role in health and disease

The insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), and IGFBP proteases are the main regulators of somatic growth and cellular proliferation. IGFs are involved in growth pre-natally and post-natally. Dysregulation of the IGF axis can lead to growth disorders such as growth hormone deficiency and acromegaly. Pre-natally, this dysregulation can lead to IUGR or macrosomia. IGFs also have an important mitogenic action and play a role in tumorigenesis and cancer. These actions are regulated by co-interactions with IGFBPs, especially IGFBP-3. In addition to somatic growth and mitogenic activity, IGFs have hypoglycaemic and insulin sensitizing actions, and their dysregulation is involved in diabetes and its complications. In this chapter, we examine the role of IGFs and IGFBPs in growth, tumorigenesis and diabetes, and discuss treatment modalities for each disease involving the GH-IGF-IGFBP axis, including discussion of current in vitro and in vivo investigations in this field.

The relationship of circulating insulin-like growth factor 1, its binding protein-3, prostate-specific antigen and C-reactive protein with disease stage in prostate cancer

OBJECTIVE

To assess the relationships among circulating insulin-like growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3), prostate-specific antigen (PSA) and C-reactive protein (an indicator of inflammatory systemic response) in patients with prostate disease and cancer of different stages.

PATIENTS AND METHODS

Circulating IGF-1, IGFBP-3, PSA and C-reactive protein concentrations were measured in patients with BPH (17) or stages T1/T2 (15), T3/T4 (16) and metastatic prostate cancer (12 patients).

RESULTS

IGF-1 and IGFBP-3 concentrations were similar between patients with BPH and those with cancer, and there was no difference between the groups with cancer. In the latter patients there was a significant correlation between age and IGFBP-3 concentrations (r = -0.400, P = 0.008) but not with IGF-1 concentrations. Controlling for age, there were significant partial correlations between C-reactive protein and IGF-1 (r = -0.412, P = 0.008) and IGFBP-3 (r = -0.277, P = 0.05).

CONCLUSIONS

These results indicate that circulating IGF-1 and IGFBP-3 concentrations do not change with disease stage in prostate cancer, but that they decrease with an increase in the systemic inflammatory response.

Association of preoperative plasma levels of insulin-like growth factor I and insulin-like growth factor binding proteins-2 and -3 with prostate cancer invasion, progression, and metastasis

PURPOSE

We tested the hypothesis that preoperative plasma levels of insulin-like growth factor (IGF) binding protein (BP)-2 or IGFBP-3 would predict cancer stage and prognosis in patients undergoing radical prostatectomy.

MATERIAL AND METHODS

Plasma levels of IGF-I, IGFBP-2, and IGFBP-3 were measured preoperatively in 120 consecutive patients who underwent radical prostatectomy for clinically localized disease, postoperatively in 51 of these patients, in 44 healthy men, in 19 patients with metastases to regional lymph nodes, and in 10 patients with bone metastases.

RESULTS

Plasma IGFBP-3 levels were lowest in patients with bone metastases (P < or = .043). IGFBP-2 levels were elevated in prostate cancer patients compared with healthy subjects (P < or = .006). However, within the group of prostatectomy patients, preoperative plasma IGFBP-2 levels were lower in patients with advanced disease (P < or = .033), were inversely correlated with prostatic tumor volume (P =.037), and declined after prostate removal (P =.044). Lower preoperative IGFBP-2 and IGFBP-3 levels and biopsy Gleason score were independent predictors of biochemical progression (P =.043, P =.040, and P =.020, respectively). In patients with disease progression, preoperative plasma IGFBP-3 levels were lower in those with aggressive than in those with nonaggressive failure (P =.042).

CONCLUSION

Elevation of plasma IGFBP-2 levels in prostate cancer patients apparently is due to increased release directly from the prostate. For patients with clinically localized prostate cancer, preoperative plasma IGFBP-2 levels are inversely associated with biologically aggressive disease and disease progression. Preoperative plasma IGFBP-3 levels were decreased in patients with prostate cancer metastases and were an independent predictor of biochemical progression after surgery, presumably because of an association with occult metastatic disease present at the time of radical prostatectomy.

Insulin-like growth factor-I and prostate cancer: a meta-analysis

Some, but not all, epidemiological found have shown that high circulating levels of insulin-like growth factor-I (IGF-I) are associated with an increased risk of prostate cancer. We performed a meta-analysis on all the studies reported so far to evaluate this association. In our Medline search, 14 case-control studies were identified. A standard protocol abstracted information for each study. Hedges' standardized mean difference (HSMD) and odds ratio (OR) were used to estimate the effect of IGF-I and IGF-binding proteins (IGFBP-3). The combined data showed that circulating levels of IGF-I were significantly higher in prostate cancer patients (HSMD = 0.194). The OR for prostate cancer was 1.47 (95% confidence interval (CI) 1.23-1.77) among men with high IGF-I compared to those with low IGF-I. The OR was 1.26 (95% CI 1.03-1.54) for IGFBP-3. Circulating levels of IGF-I and IGFBP-3 are likely to be higher in prostate cancer patients than in the controls. These findings support the suggestion that high IGF-I and IGFBP-3 are associated with an increased risk of prostate cancer.

Does the GH-IGF axis play a role in cancer pathogenesis?

Recent case-controlled studies have found increases in the serum levels of insulin-like growth factor-I (IGF-I) in subjects who had, or who eventually developed, prostate or premenopausal breast cancers. Since growth hormone (GH) increases IGF-I levels, concern has been raised regarding its potential role as a cancer initiation factor. The epidemiological studies, which indicate an association between serum IGF-I levels and cancer risk, have not established causality. In fact, several alternative explanations for the elevated serum IGF-I levels in cancer patients may be proposed based on human and animal models. First, an effect of IGF-I causing symptomatic benign tissue hyperplasia may result in an ascertainment bias leading to an initiation of procedures resulting in the diagnosis of asymptomatic cancers. Second, elevated serum IGF-I in cancer patients may originate within the tumor (as suggested by some animal studies). Thirdly, serum IGF-I may actually be a surrogate marker of tissue IGF-I levels or of nutritional factors, which are not under GH control and may be involved in cancer initiation. The role of GH in cancer initiation is further negated by the fact that in acromegaly, the incidence of cancer, other than possibly colonic neoplasia does not appear to be significantly increased. Furthermore, GH transgenic mice, with high IGF-I levels, do not develop breast, prostate, or colonic malignancies. It is known that IGFBP-3 can inhibit IGF action on cancer cells in vitro and also can induce apoptosis via an IGF-independent mechanism. Importantly, in addition to increasing IGF-I levels, GH also increases the serum levels of IGFBP-3 and serum IGFBP-3 levels have been shown to be negatively correlated with the risk of cancer in the above mentioned epidemiological studies and in a similar study on colon cancer. These studies suggest that cancer risk is increased in individuals in whom both high IGF-I levels and low IGFBP-3 levels are present. In subjects treated with GH, IGF-I and IGFBP-3 levels both rise together and are not within the elevated cancer-risk range, based on published studies. Long-term studies are needed to assess the potential risks, including the long-term cancer risk associated with GH therapy. These should take into account several factors, including the duration of exposure, the risk magnitude associated with the degree of serum IGF-I elevation, and the adjusted risk based on a concomitant increase in IGFBP-3 levels. Since GH treated patients often have sub-normal IGF-I serum levels, which normalize on therapy, one might predict that their cancer risk on GH therapy should not increase above the normal population. Until further research in the area dictates otherwise, on-going cancer surveillance and routine monitoring of serum IGF-I and IGFBP-3 levels in GH-recipients should be the standard of care. At present, the data that are available do not warrant a change in our current management of approved indications for GH therapy.