Exogenous administration of protease-resistant,non-matrix-binding IGFBP-2 inhibits tumour growth in a murine model of breast cancer

Background:

Insulin-like growth factors (IGF-I and IGF-II) signal via the type 1 IGF receptor (IGF-1R) and IGF-II also activates the insulin receptor isoform A (IR-A). Signalling via both receptors promotes tumour growth, survival and metastasis. In some instances IGF-II action via the IR-A also promotes resistance to anti-IGF-1R inhibitors. This study assessed the efficacy of two novel modified IGF-binding protein-2 (IGFBP-2) proteins that were designed to sequester both IGFs. The two modified IGFBP-2 proteins were either protease resistant alone or also lacked the ability to bind extracellular matrix (ECM).

Methods:

The modified IGFBP-2 proteins were tested in vitro for their abilities to inhibit cancer cell proliferation and in vivo to inhibit MCF-7 breast tumour xenograft growth.

Results:

Both mutants retained low nanomolar affinity for IGF-I and IGF-II (0.8–2.1-fold lower than IGFBP-2) and inhibited cancer cell proliferation in vitro. However, the combined protease resistant, non-matrix-binding mutant was more effective in inhibiting MCF-7 tumour xenograft growth and led to inhibition of angiogenesis.

Conclusions:

By removing protease cleavage and matrix-binding sites, modified IGFBP-2 was effective in inhibiting tumour growth and reducing tumour angiogenesis.     

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.

     

Arthralgia induced by endocrine treatment for breast cancer: A prospective study of serum levels of insulin like growth factor-I,its binding protein and oestrogens

BackgroundAromatase inhibitors (AIs) frequently induce or enhance musculoskeletal problems (AI-induced musculoskeletal syndrome (AIMSS)) which sometimes are debilitating. Apart from low oestrogen levels, underlying mechanisms are unknown and likely multiple. We previously hypothesised a role for the growth hormone/insulin like growth factor-I (IGF-I) axis. Here, we report the effect of tamoxifen and AI on IGF-I, IGF binding protein-3 (IGFBP-3) and oestrogen levels from a prospective study.Materials and methodsPostmenopausal women with an early breast cancer scheduled to start adjuvant endocrine therapy with an AI or tamoxifen were recruited. A rheumatologic questionnaire was completed and serum was collected for assessment of IGF-I, IGFBP-3 and oestrogen levels. Re-evaluation was done after 3, 6 and 12 months of therapy.Results84 patients started on tamoxifen (n = 42) or an AI (n = 42). 66% of the latter group experienced worsening of pre-existing or de novo complaints in joint and/or muscle, compared to 29% of tamoxifen-treated patients. AI therapy resulted in elevated IGF-I levels with a statistically significant increase at 6 months (p = 0.0088), whereas tamoxifen users were characterised by a decrease in IGF-I levels at all follow-up times (p < 0.0004). No effect on IGFBP-3 was seen in the latter group. AI-users, however, showed decreased IGFBP-3 levels at 12 months (p = 0.0467). AIMSS was characterised by a decrease in IGFBP-3 levels (p = 0.0007) and a trend towards increased IGF-I/IGFBP-3 ratio (p = 0.0710).ConclusionThese findings provide preliminary evidence that AI-induced musculoskeletal symptoms are associated with changes in the growth hormone (GH)/IGF-I axis.     

The relation between adiposity throughout the life course and variation in IGFs and IGFBPs: evidence from the ProtecT (Prostate testing for cancer and Treatment) study

Objective

Adiposity is positively associated with advanced, metastatic, and fatal prostate cancer. Obesity-related variations in insulin-like growth factors (IGF-I and -II) and their binding proteins (IGFBPs) could underlie these associations.

Methods

We investigated associations of adiposity throughout the life course (determined retrospectively) with serum levels of IGF-I, IGF-II, IGFBP-2 and IGFBP-3 in a population-based study of 1,106 healthy men.

Results

IGF-I and IGF-II showed inverted U-shaped associations with adult body mass index (BMI) (p quadratic model = 0.04 and 0.06, respectively), although differences between quartiles with the highest and lowest IGF-I levels were small (no more than 5 ng/ml). IGFBP-2 was strongly inversely related to adult BMI (?22% change per SD increase in BMI; 95% confidence interval (CI) ?24% to ?19%) and waist circumference (?18% change per SD increase in waist circumference; 95% CI ?20% to ?15%) (p < 0.001). IGFBP-3 was positively related to BMI (63.5 ng/ml increase per SD increase in BMI; 95% CI ?2.69 to 129.8, p = 0.06). IGFBP-2 and IGFBP-3 were strongly related to body shape change from childhood to adulthood, with men who gained the most weight having the lowest IGFBP-2 (9% lower per category body shape change; 95% CI ?11% to ?7%, p < 0.001) and the highest IGFBP-3 (50 ng/ml increase per category; 95% CI 8 to 92, p = 0.02).

Conclusions

We provide evidence that adiposity and change in body shape through the life course are related to the IGF system, with the largest effect of adiposity being to lower IGFBP-2, a possible marker of insulin resistance. The results suggest that circulating IGF-I levels may not be important mediators of the association of adiposity with aggressive prostate cancer, but the role of IGFBP-2 deserves further investigation.     

Relation of serum insulin-like growth factor-I (IGF-I) and IGF binding protein-3 to risk of prostate cancer (United States)

Objective: Insulin-like growth factor I (IGF-I) exerts potent mitogenic and antiapoptotic effects on prostatic epithelial cells. Insulin-like growth factor binding protein-3 (IGFBP-3) modulates the effects of IGF-I, and independently induces apoptosis and inhibits cell growth. Previous studies have inconsistently associated IGF-I and IGFBP-3 with prostate cancer. To try and further clarify these potential associations, we undertook a sibling-matched case–control study. Methods: Serum IGF-I and IGFBP-3 were determined for 845 men (408 cases and 437 sibling controls). Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between the serum IGF levels and prostate cancer. Results: Among all study subjects, only the molar ratio of IGF-I to IGFBP-3 was associated with prostate cancer: comparing those in the highest to lowest quartiles gave an OR = 1.62 (95% CI = 1.02–2.57, trend-p = 0.04). Among men with clinically less aggressive disease, we observed positive associations between prostate cancer and high levels of IGF-I (OR = 2.78, 95% CI = 1.06–6.80, trend-p = 0.03), and IGFBP-3 (OR = 2.68, 95% CI = 1.08–6.80, trend-p = 0.04). Simultaneously modeling both left the IGF-I result essentially unchanged, while substantially weakening the IGFBP-3 association. Conclusions: We found that a high IGF-I to IGFBP-3 molar ratio was associated with an increased risk of prostate cancer. Furthermore, high IGF-I was associated with increased risk of prostate cancer among men with less advanced disease at diagnosis. These results lend support to the hypothesis that IGF-I, or the IGF-I to IGFBP-3 molar ratio, is an important risk factor for prostate cancer.     

Insulin-like growth factors and risk of kidney cancer in men

Background:

Insulin-like growth factor-I (IGF-I) has been shown to increase kidney growth, glomerular filtration rate, and renal function.

Methods:

In the prospective Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) study of 29 133 Finnish male smokers aged 50–69 years, serum concentrations of IGF were measured in samples collected in 1985–1988. A total of 100 men with kidney cancer diagnosed ⩾5 years after blood collection through 1997 were compared with a subcohort of 400 men; logistic regression models were used to estimate the risk of developing kidney cancer.

Results:

Men with IGF-I levels >113 ng ml⁻¹ were 59% less likely to develop kidney cancer than men with levels ⩽113 ng ml⁻¹ (odds ratio=0.41; 95% confidence interval=0.23–0.75). The IGF binding protein-3 (IGFBP-3) levels did not alter the association. No association was observed between IGFBP-3, or molar ratio of IGF-I/IGFBP-3, and kidney cancer.

Conclusions:

Low serum IGF-I levels in this cohort of older middle-aged male smokers are associated with increased kidney cancer risk, independent of IGFBP-3.     

Free insulin-like growth factor-I and breast cancer risk

Insulin-like growth factor-I (IGF-I) has mitogenic and anti-apoptotic effects on breast cancer cells. Epidemiologic studies have shown that high plasma levels of IGF-I and low levels of IGF binding protein (BP)-3 are associated with increased risk of breast cancer in premenopausal women. The actions of IGF-I are mediated through the IGF-I receptor (IGF-IR) and are regulated by IGFBPs. In circulation, most of the IGF-I binds to IGFBP-3, and binding of IGF-I to IGFBP-3 inhibits the actions of IGF-I. Since free IGF-I, which does not bind to IGFBPs, can readily cross the endothelial barrier to interact with IGF-IR, circulating free IGF-I is thought to be more relevant to the biologic activity of IGF-I. To examine the association of free IGF-I with breast cancer, we compared free IGF-I levels between 40 newly diagnosed breast cancer patients and 40 age- and race-matched healthy controls. Plasma levels of free IGF-I, total IGF-I and IGF-II, as well as total, intact and fragment IGFBP-3, were measured using commercial immunoassay kits. The association between IGF-I and breast cancer was examined using the conditional logistic regression analysis. Analysis of correlation (Spearman) showed that free IGF-I was correlated with total IGF-I and IGFBP-3 but not with IGF-II. The odds ratios for breast cancer patients having high plasma IGF-I (> or = median) after adjusting for menopausal status and IGFBP-3 were 2.00 (p < o r = 0.376) for total IGF-I and 6.31 (p < or = 0.047) for free IGF-I. A high ratio of IGF-I to IGFBP-3 was also associated with breast cancer (p < 0.05). No association was found for IGF-II, nor for total, intact and fragment IGFBP-3. The findings of this study suggest that measuring free IGF-I in circulation is more useful than measuring total IGF-I with respect to evaluation of an association between IGF-I and breast cancer risk.     

Serum insulin-like growth factor-I and insulin-like growth factor binding protein-3 levels with risk of malignant melanoma

We examined the relationship of insulin-like growth factor-I (IGF-I) and its primary growth factor, IGF binding protein-3 (IGFBP-3) with malignant melanoma using interview data and sera from cases (n = 286) and controls (n = 289) in a population-based case–control study conducted in 1986–1992 on Oahu, Hawaii. Serum IGF-I and IGFBP-3 concentrations were measured by ELISA. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression and adjusting for age, sex, education, number of blistering sunburns, ability to tan, hair color, energy intake, BMI, height, smoking status, and drinking status. An inverse relationship was found between IGF-I concentration and melanoma (OR for upper vs. lower tertile: 0.44, 95% CI: 0.25–0.79), but clear associations were not observed between malignant melanoma and upper tertiles of IGFBP-3 and the IGF-1/IGFBP-3 molar ratio. The inverse association with IGF-I was strongest among subjects who did not report a history of non-melanoma skin cancer (NMSC) (OR for ≥ vs. < median: 0.39, 95% CI: 0.24–0.65), and a positive association was found among those with such a history (OR: 3.6, 95% CI: 1.0–13; p _interaction = 0.0035). Our findings observed here between serum IGF-I and malignant melanoma warrants replication in studies with a larger sample size and a prospective design.     

Circulating insulin-like growth factor axis and the risk of pancreatic cancer in four prospective cohorts

Insulin-like growth factor (IGF)-I induces growth in pancreatic cancer cells and blockade of the IGF-I receptor has antitumour activity. The association of plasma IGF-I and IGF binding protein-3 (IGFBP-3) with pancreatic cancer risk has been investigated in two small studies, with conflicting results. We conducted a nested case-control study within four large, prospective cohorts to investigate whether prediagnostic plasma levels of IGF-I, IGF-II, and IGFBP-3 were associated with pancreatic cancer risk. Plasma levels in 212 cases and 635 matched controls were compared by conditional logistic regression, with adjustment for other known pancreatic cancer risk factors. No association was observed between plasma levels of IGF-I, IGF-II, or IGFBP-3 and incident diagnosis of pancreatic cancer. Relative risks for the highest vs the lowest quartile of IGF-I, IGF-II, and IGFBP-3 were 0.94 (95% confidence interval (CI), 0.60-1.48), 0.96 (95% CI, 0.61-1.52), and 1.21 (95% CI, 0.75-1.92), respectively. The relative risk for the molar ratio of IGF-I and IGFBP-3, a surrogate measure for free IGF-I, was 0.84 (95% CI, 0.54-1.31). Additionally, no association was noted in stratified analyses or when requiring longer follow-up. In four prospective cohorts, we found no association between the risk of pancreatic cancer and prediagnostic plasma levels of IGF-I, IGF-II, or IGFBP-3.     

Mitogenic properties of insulin-like growth factors I and II,insulin-like growth factor binding protein-3 and epidermal growth factor on human breast epithelial cells in primary culture

Insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II) are growth factors implicated in mammary gland development and are believed to be involved in breast cancer. However, the interactions between components of the IGF system and breast epithelial cells, which give rise to breast cancer, are not well understood. We have investigated the mitogenic properties of IGF-I, IGF-II, IGF binding protein-3 (IGFBP-3) and epidermal growth factor (EGF) on human breast epithelial cells (HBEC) in primary culture. We show that, under serum-free conditions, HBEC are stimulated to grow in response to IGF-I and IGF-II in a dose-dependent manner. IGF-I and EGF, a potent stimulator of HBEC growth in primary culture and also associated with breast cancer, appear to stimulate HBEC in a synergistic manner. IGFBP-3 inhibits the stimulation by IGF-I, IGF-II and IGF-I plus EGF. In addition, it appears that IGFBP-3 has an inhibitory effect on HBEC growth that is IGF-independent. This study is the first to address the effects of IGF-I, IGF-II and IGFBP-3 alone and in combination with EGF on HBEC growth in primary culture. Characterizing the role of the IGF system in normal breast biology is significant because the system has been implicated in breast cancer and a number of the anti-estrogens used in treatment are believed to function through the IGF system.     

Mitogenic Properties of Insulin-Like Growth Factors I and II, Insulin-like Growth Factor Binding Protein-3 and Epidermal Growth Factor on Human Breast Stromal Cells in Primary Culture

Insulin-like growth factors I and II (IGF-I and IGF-II) are growth factors implicated in both normal mammary gland development and breast cancer. We have previously reported on the effects of components of the IGF system on breast epithelial cells. Since data suggests that stromal-epithelial interactions play a crucial role in breast cancer, we have now investigated the mitogenic properties of IGF-I, IGF-II, insulin-like growth factor binding protein-3 (IGFBP-3) and epidermal growth factor (EGF) on human breast stromal cells in primary culture. We show that, under serum-free conditions, stromal cells are stimulated to grow in response to IGF-I and IGF-II in a dose-dependent manner. IGF-I and EGF, a potent stimulator of human breast epithelial cell growth in primary culture and also associated with breast cancer, appear to stimulate stromal cell growth in a synergistic manner. IGFBP-3 does not inhibit the stimulation of growth by IGF-I, or IGF-I plus EGF. However, IGFBP-3 does inhibit the stimulation of growth by IGF-II. In contrast to our previous results with human breast epithelial cells, IGFBP-3 does not have an IGF-independent inhibitory effect on stromal cell growth. This study is the first to address the effects of IGF-I, IGF-II and IGFBP-3 alone and in combination with EGF on human breast stromal cell growth in primary culture. Characterizing the role of the IGF system in both normal breast epithelial cells and stromal cells will aid in our understanding of the mechanisms behind the role of the IGF system in breast cancer.     

Cancer risk factors associated with insulin-like growth factor (IGF)-I and IGF-binding protein-3 levels in healthy women: effect modification by menopausal status

Insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) appear to influence breast cancer risk and are hypothesized to mediate the effects of several cancer risk factors that depend on menopausal status. We investigated associations among cancer risk factors and plasma IGF-I and IGFBP-3 in 882 healthy control women (426 premenopausal, 456 postmenopausal) from two population-based breast cancer case–control studies. Interactions with menopausal status were statistically tested. We observed associations with non-modifiable (age, benign breast disease) and modifiable factors [body mass index (BMI), physical activity, smoking habits, alcohol consumption]. Furthermore, we demonstrated statistical interactions with menopausal status. Premenopausal IGFBP-3 levels increased and postmenopausal levels decreased with age (p-interaction = 0.001). Overweight postmenopausal women had higher IGF-I (p = 0.049) and IGFBP-3 (p = 0.005) levels than women with lower BMI. Postmenopausal IGF-I levels were positively associated with physical activity (p-trend = 0.012, p-interaction = 0.050). Postmenopausal current smokers had lower IGF-I (p = 0.014) and IGFBP-3 levels (p = 0.011). Increasing alcohol consumption was associated with lower premenopausal IGF-I (p-trend = 0.002, p-interaction = 0.004) and higher postmenopausal IGFBP-3 levels (p = 0.019). Benign breast disease was associated with higher premenopausal (p = 0.044) and postmenopausal (p = 0.002) IGF-I levels. IGF-I and/or IGFBP-3 potentially mediate changes in breast cancer risk associated with BMI, benign breast disease, and perhaps alcohol consumption. Other observed associations suggest that neither IGF-I nor IGFBP-3 alone acts as mediator. Consideration of menopausal status may help disentangle carcinogenic pathways involving IGF proteins.     

Effects of tamoxifen and octreotide LAR on the IGF-system compared with tamoxifen monotherapy

The insulin-like growth factor (IGF)-system was evaluated in 150 breast cancer patients participating in a randomised phase III trial comparing octreotide pamoate and tamoxifen with tamoxifen+placebo. Alterations in the IGF-system in the two treatment arms and individual changes with respect to outcome were compared. Serum IGF-I and -II, free IGF-I, and insulin-like growth factor binding protein 1-3 (IGFBP1-3) were measured by radioimmmunoassay (RIA)/immunoradiometric assay (IRMA) and IGFBPs by Western ligand blots (WLB) before and during treatment. Combined treatment caused a higher increase in IGFBP-1 and larger suppression of total and free IGF-I, IGF-II, and IGFBP-3 (P<0.01 for all), but less suppression of IGFBP-2 (P<0.05) compared with tamoxifen monotherapy. An increase in IGFBP-2 25% was associated with decreased progression-free survival (PFS) in the total patient population and combined treatment group. Similar response rates and time to progression in the treatment arms suggests moderate suppression of circulating IGF-I has no influence on clinical outcome.     

Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-I and IGF-binding protein-3

BACKGROUND: Insulin-like growth factor-I (IGF-I) is a potent mitogen for normal and neoplastic cells, whereas IGF-binding protein-3 (IGFBP-3) inhibits cell growth in many experimental systems. Acromegalics, who have abnormally high levels of growth hormone and IGF-I, have higher rates of colorectal cancer. We therefore examined associations of plasma levels of IGF-I and IGFBP-3 with the risk of colorectal cancer in a prospective case-control study nested in the Physicians' Health Study. METHODS: Plasma samples were collected at baseline from 14916 men without diagnosed cancer. IGF-I, IGF-II, and IGFBP-3 were assayed among 193 men later diagnosed with colorectal cancer during 14 years of follow-up and among 318 age- and smoking-matched control subjects. All P values are two-sided. RESULTS: IGFBP-3 levels correlated with IGF-I levels (r=.64) and with IGF-II levels (r=.90). After controlling for IGFBP-3, age, smoking, body mass index (weight in kg/[height in m]2), and alcohol intake, men in the highest quintile for IGF-I had an increased risk of colorectal cancer compared with men in the lowest quintile (relative risk [RR]=2.51; 95% confidence interval [CI]=1.15-5.46; P for trend = .02). After controlling for IGF-I and other covariates, men with higher IGFBP-3 had a lower risk (RR=0.28; 95% CI=0.12-0.66; P for trend = .005, comparing extreme quintiles). The associations were consistent during the first and the second 7-year follow-up intervals and among younger and older men. IGF-II was not associated with risk. CONCLUSIONS: Our findings suggest that circulating IGF-I and IGFBP-3 are related to future risk of colorectal cancer.     

Plasma insulin-like growth factor binding protein-3 proteolysis is increased in primary breast cancer.

Fasting blood samples were obtained before definitive surgery or biopsy in 128 patients referred to the department of surgery with suspected or manifest breast cancer. Insulin-like growth factor (IGF)-I, IGF-II and free IGF-I were measured by radioimmunoassay/immunoradiometric assay, while IGFBP-3 proteolysis was evaluated by Western immunoblot. 12 patients had ductal carcinoma in situ benign conditions, while staging revealed metastatic disease in 15 of 16 patients with invasive cancers. IGFBP-3 proteolysis above the normal range was recorded in 19 patients with invasive cancers, but in none of the patients suffering from DCIS/benign conditions. Increased IGFBP-3 proteolysis was most frequently recorded in patients harbouring large tumours and metastatic disease (Stage I: 0/19, 0%; Stage II: 3/45, 7%, Stage III: 9/37, 24%, and Stage IV: 7/15, 47%). IGFBP-3 proteolysis was significantly higher in Stage III (P =0.01) and IV (P< 0.001) patients compared to the other stage groups (P = 0.001). IGF-I and IGF-II correlated negatively to IGFBP-3 proteolysis and age. Plasma levels of IGF-I and -II were significantly lower in patients with elevated IGFBP-3 proteolysis compared to those within the normal range. Our findings reveal alterations in the IGF-system among a substantial number of patients with large primary breast cancers.     

Factors associated with circulating levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in 740 women at risk for breast cancer

Prospective studies have shown an association between elevated plasma levels of insulin-like growth factor-I (IGF-I) and/or decreased levels of its major circulating carrier protein insulin-like growth factor binding protein-3 (IGFBP-3) and increased risk of major cancers. Identifying the factors which affect these biomarkers is of particular interest as subjects at increased risk could benefit from lifestyle changes, and/or chemoprevention intervention. We evaluated the association between constitutional, hormonal and clinical factors and IGF-I and IGFBP-3 in 740 women, including 376 unaffected women and 364 women with intraepithelial neoplasia (IEN) or early invasive breast cancer enrolled in breast cancer chemoprevention trials, conducted at a single institution. Age, body mass index (BMI), height, waist to hip girth ratio (WHR), parity, menopausal status, age at menarche, number of affected first degree relatives, number of biopsies and breast cancer status were considered in the analysis. Women with early breast cancer had 21% higher IGF-I levels ( p=0.033) and 19% higher IGF-I/IGFBP-3 molar ratio ( p=0.047) than unaffected women. In unaffected women, age was negatively associated with IGF-I ( p=0.002) and IGF-I/IGFBP-3 ( p=0.001), while age at menarche was negatively associated with IGFBP-3 levels ( p=0.043). In women with IEN or early breast cancer, IGF-I levels were negatively associated with age ( p < 0.001), and positively associated with prior biopsies for benign disease ( p=0.013), while age, parity and menopausal status were significant predictors of IGF-I/IGFBP-3 molar ratio. We conclude that circulating IGF-I levels are higher in women with prior breast cancer compared to unaffected women, and that IGF-I and/or IGFBP-3 levels are influenced by age and by reproductive and hormonal factors. These findings support their putative role as breast cancer risk biomarker.     

Effect of diet and exercise on serum insulin,IGF-I,and IGFBP-1 levels and growth of LNCaP cells in vitro (United States)

Objective: Accumulating evidence indicates that prostate cancer is associated with high levels of serum IGF-I. This study was conducted to determine whether a low-fat diet and exercise (DE) intervention may modulate the IGF axis and reduce prostate cancer cell growth in vitro. Methods: Fasting serum was obtained from 14 men (age 60 ± 3 years) participating in an 11-day DE program and from eight similarly aged men who had followed the DE program for 14.2 ± 1.7 years (long-term). Insulin, IGF-I, IGFBP-1, and IGFBP-3 were measured by ELISA, and serum was used to stimulate LNCaP cell growth in vitro. Results: Serum IGF-I levels decreased by 20% while IGFBP-1 increased by 53% after 11-day DE. In the long-term group, IGF-I was 55% lower, while IGFBP-1 was 150% higher relative to baseline. Serum insulin decreased by 25% after 11-day DE and was 68% lower in the long-term group, relative to baseline. No changes in serum IGFBP-3 were observed. Serum-stimulated LNCaP cell growth was reduced by 30% in post-11-day serum and by 44% in long-term serum relative to baseline. LNCaP cells incubated with post-DE serum showed increased apoptosis/necrosis, compared to baseline. Conclusions: A low-fat diet and exercise intervention induces in-vivo changes in the circulating IGF axis and is associated with reduced growth and enhanced apoptosis/necrosis of LNCaP tumor cells in vitro.     

Determinants of circulating insulin-like growth factor (IGF)-I and IGF binding proteins 1–3 in premenopausal women: physical activity and anthropometry (Netherlands)

Objective: Epidemiologic studies suggest that subjects with elevated plasma concentrations of IGF-I are at increased risk of developing cancer. The objective of our study was to assess whether cancer risk factors such as lack of physical activity, obesity, and central body fat distribution are associated with plasma levels of IGF-I and related proteins (i.e. IGF binding proteins 1–3 and C-peptide). Methods: A cross-sectional study was conducted in a population of 225 premenopausal women, aged 49–57, participating in the Prospect–EPIC study in the Netherlands. Plasma concentrations of IGF-I, IGFBP-1, IGFBP-2, IGFBP-3, and C-peptide were determined. On the day of blood collection height, weight, and waist and hip circumference were measured. Habitual physical activity was assessed using a validated self-administered questionnaire. Results: Mean concentrations of plasma IGF-I, IGFBP-1, IGFBP-2, IGFBP-3, and C-peptide were 156.1, 14.3, 434.4, 3062, and 2.86 ng/ml, respectively. Women in the highest tertile for physical activity had lower plasma concentrations of IGF-I, IGFBP-3, and C-peptide, and higher concentrations of IGFBP-1 and IGFBP-2, as compared to women in the lowest tertile. However, these differences were not statistically significant. BMI and related measures were significantly inversely associated with IGFBP-1 and IGFBP-2, and positively with IGFBP-3 and C-peptide. Linear regression analyses showed that the non-significant association of physical activity with components of the plasma IGF system was further attenuated by adjusting for obesity and central body fat distribution. Conclusions: Our data suggest that an active lifestyle is not independently associated with the plasma IGF system. We did confirm that a lean body shape is associated with higher concentrations of IGFBP-1 and IGFBP-2, and possibly also with lower concentrations of IGF-I and IGFBP-3.     

Insulin-like growth factors and liver cancer risk in male smokers

Background:

The liver is the primary source of circulating insulin-like growth factor (IGF)-I, yet the relation between IGFs and liver cancer is uncertain.

Methods:

In a case–cohort study within a cohort of 29 133 male smokers we examined associations of serum IGF-I and IGF binding protein (IGFBP)-3 with liver cancer (50 cases).

Results:

Nonlinear associations between liver cancer and IGF-I and IGFBP-3 were observed (P=0.04 and P<0.01, respectively), strongest association at lowest levels (odds ratio (OR)=0.2, 95% confidence interval (CI)=0.1–0.7 for 80 vs 30 ng ml⁻¹ of IGF-I; OR=0.2, 95% CI=0.1–0.6 for 1400 vs 700 ng ml⁻¹ of IGFBP-3).

Conclusions:

Low IGF-I and IGFBP-3 levels in male smokers are associated with increased risk of liver cancer.