Insulin-like growth factors and prostate cancer

Insulin-like growth factor family and prostate cancer: new insights and emerging opportunities

Prostate cancer is the second most commonly diagnosed cancer in men. The mammalian insulin-like growth factor (IGF) family is made up of three ligands (IGF-I, IGF-II, and insulin), three receptors (IGF-I receptor (IGF-1R), insulin receptor (IR), and IGF-II receptor (IGF-2R)), and six IGF-binding proteins (IGFBPs). IGF-I and IGF-II were identified as potent mitogens and were previously associated with an increased risk of cancer development including prostate cancer. Several reports showed controversy about the expression of the IGF family and their connection to prostate cancer risk due to the high degree of heterogeneity among prostate tumors, sampling bias, and evaluation techniques. Despite that, it is clear that several IGF family members play a role in prostate cancer development, metastasis, and androgen-independent progression. In this review, we aim to expand our understanding of prostate tumorigenesis and regulation through the IGF system. Further understanding of the role of IGF signaling in PCa shows promise and needs to be considered in the context of a comprehensive treatment strategy.

The antitumor potential of Interleukin-27 in prostate cancer

Prostate cancer (PCa) is of increasing significance worldwide as a consequence of the population ageing. Fragile elderly patients may particularly benefit from noninvasive and well tolerable immunotherapeutic approaches. Preclinical studies have revealed that the immune-regulatory cytokine IL-27 may exert anti-tumor activities in a variety of tumor types without discernable toxicity. We, thus, investigated whether IL-27 may function as anti-tumor agent in human (h) PCa and analyzed the rationale for its clinical application.

In vitro, IL-27 treatment significantly inhibited proliferation and reduced the angiogenic potential of hPCa cells by down-regulating the pro-angiogenesis-related genes fms-related tyrosine kinase (FLT)1, prostaglandin G/H synthase 1/cyclooxygenase-1 (PTGS1/COX-1) and fibroblast growth factor receptor (FGFR)3. In addition, IL-27 up-regulated the anti-angiogenesis-related genes such as CXCL10 and TIMP metallopeptidase inhibitor 3 (TIMP3). In vivo, IL-27 reduced proliferation and vascularization in association with ischemic necrosis of tumors developed after PC3 or DU145 cell injection in athymic nude mice. In patients' prostate tissues, IL-27R was expressed by normal epithelia and low grade PCa and lost by high tumor grade and stages. Nevertheless, IL-27R was expressed by CD11c⁺, CD4⁺ and CD8⁺ leukocytes infiltrating the tumor and draining lymph nodes.

These data lead to the conclusion that i) IL-27's anti-PCa potential may be fully exploited in patients with well-differentiated, localized IL-27R positive PCa, since in this case it may act on both cancerous epithelia and the tumor microenvironment; ii) PCa patients bearing high grade and stage tumor that lack IL-27R may benefit, however, from IL-27's immune-stimulatory properties.

Safety, tolerability, and pharmacokinetics of single and multiple doses of intravenous cixutumumab (IMC-A12), an inhibitor of the insulin-like growth factor-I receptor, administered weekly or every 2 weeks in patients with advanced solid tumors

BACKGROUND

Type 1 insulin-like growth factor receptor (IGF-IR) signaling is often dysregulated in cancer. Cixutumumab, a fully human IgG1 monoclonal antibody, blocks IGF-IR and inhibits downstream signaling. The current study determined the recommended dose, safety, and pharmacokinetic (PK) profile of weekly or every-2-week dosing of cixutumumab.

PATIENTS AND METHODS

Two open-label, multicenter phase I studies evaluated weekly (3-15 mg/kg) or every-2-weeks (6-15 mg/kg) dosing of cixutumumab in patients with advanced solid tumors. Serial blood samples for PK were collected up to 168-336 h (day 8-15) following the first administration of cixutumumab. Efficacy was evaluated as best overall tumor response.

RESULTS

A total of 24 and 16 patients were enrolled in the weekly and every-2-week dosing studies, respectively. Treatment-emergent adverse events (≥10%) included hyperglycemia, fatigue, anemia, nausea, and vomiting. Severe adverse events (AE) were infrequent; one serious AE (grade 3 electrocardiogram QT prolongation) was deemed possibly cixutumumab-related (10 mg/kg every-2-weeks). One death occurred due to disease progression (6 mg/kg weekly cohort). Maximum serum concentrations increased with dose. A maximum tolerated dose was not identified; pre-determined target serum minimum concentrations (60 μg/mL) were achieved with ≥6 mg/kg weekly and ≥10 mg/kg every-2-week dosing. Cixutumumab terminal elimination half-life is approximately a week (individual range, t1/2 = 4.58-9.33 days based upon 10 mg/kg every 2 weeks). Overall, stable disease was achieved in 25% of all patients.

CONCLUSIONS

Cixutumumab was associated with favorable safety and PK profiles. A dosing regimen of 10 mg/kg every 2 weeks was recommended for subsequent disease-focused clinical trials.

Carbohydrate intake, glycemic index and prostate cancer risk

BACKGROUND

Reported associations between dietary carbohydrate and prostate cancer (PC) risk are poorly characterized by race.

METHODS

We analyzed the association between carbohydrate intake, glycemic index (GI), and PC risk in a study of white (N = 262) and black (N = 168) veterans at the Durham VA Hospital. Cases were 156 men with biopsy-confirmed PC and controls (N = 274) had a PSA test but were not recommended for biopsy. Diet was assessed before biopsy with a self-administered food frequency questionnaire. Logistic regression models were used to estimate PC risk.

RESULTS

In multivariable analyzes, higher carbohydrate intake, measured as percent of energy from carbohydrates, was associated with reduced PC risk (3rd vs. 1st tertile, OR = 0.41, 95% CI 0.21-0.81, P = 0.010), though this only reached significance in white men (p-trend = 0.029). GI was unrelated to PC risk among all men, but suggestively linked with reduced PC risk in white men (p-trend = 0.066) and increased PC risk in black men (p-trend = 0.172), however, the associations were not significant. Fiber intake was not associated with PC risk (all p-trends > 0.55). Higher carbohydrate intake was associated with reduced risk of high-grade (p-trend = 0.016), but not low-grade PC (p-trend = 0.593).

CONCLUSION

Higher carbohydrate intake may be associated with reduced risk of overall and high-grade PC. Future larger studies are needed to confirm these findings.

Expression levels of insulin-like growth factors 1 and 2 in head and neck squamous cell carcinoma

Insulin-like growth factors (IGF) 1 and 2 are known as potential mitogens for normal and neoplastic cells. IGF2 is a main fetal growth factor while IGF1 is activated through growth hormone action during postnatal growth and development. However, there is strong evidence that activation of IGF2 by its E2F transcription factor 3 (E2F3) is present in different types of cancer. Also high levels of IGF1 strongly correlate with cancer development due to anti-apoptotic properties and enhancement of cancer cell differentiation, which can be attenuated by IGFBP3. Head and neck cancer is known as one of the six most common human cancers. The main risk factor for head and neck cancer is consumption of tobacco and alcohol as well as viral infection and bacterial infection by stimulation of chronic local inflammation. There is also a genetic basis for this form of cancer; however, the genetic markers are not yet established. In this study we investigated the levels of the expression of IGF2, IGF1, E2F3 and IGFBP3 in human cancers and healthy tissues surrounding the tumor obtained from each of 41 patients. Our study indicated that there is no alteration of the levels of expression of IGF2, E2F3 and IGF1 in head and neck squamous cell carcinoma (HNSCC) cases studied in selected experimental population, but there was evidence for upregulation of pro-apoptotic IGFBP3 in cancer when comparing to healthy tissue. These important findings indicate that insulin-growth factors are not directly associated with HNSCC showing some variability between patients and location of tumor. However, elevated level of IGFBP3 suggests possible regulatory role of IGF signal by its binding protein in this type of tumor.

Coffee consumption and prostate cancer risk: an updated meta-analysis

PURPOSE

Many epidemiological studies have been conducted to explore the association between coffee consumption and prostate cancer. However, the results remain inconsistent. We performed a large meta-analysis of relevant studies to derive a more precise estimation of this relationship.

METHODS

Systematic searches of PubMed and several other databases up to June 2013 were retrieved. All epidemiologic studies regarding coffee consumption and prostate cancer risk were included, and odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated to estimate the strength of the association.

RESULTS

Twelve case-control studies involving 7,909 prostate cancer cases and 9,461 controls and nine cohort studies involving 455,123 subjects were included in our analysis. Compared with the lowest category, the unstratified highest category of coffee consumption showed a significance reduction in prostate cancer risk of a fixed-effects model (OR 0.91, CI 0.86-0.97). A borderline significant influence was also found when the stratified highest category (US ≥ 4, Europe ≥ 5) of coffee consumption was compared with the reference category (OR 0.96, CI 0.92-1.00), but no relationships were observed for the other two categories. In another analysis conducted by coffee consumption and prostate cancer stage and Gleason grade, our results showed a significant inverse association in all categories of prostate cancer except Gleason <7 grade in a fixed-effects model; the results remained the same, except for advanced prostate cancer, in a random-effects model.

CONCLUSIONS

Our meta-analysis suggests that high (e.g., highest ≥ 4 or 5 cups/day) coffee consumption may not only be associated with a reduced risk of overall prostate cancer, but also inversely associated with fatal and high-grade prostate cancer.

Epidemiological study of prostate cancer (EPICAP): a population-based case-control study in France

BACKGROUND

Prostate cancer is the most common cancer in male in most Western countries, including France. Despite a significant morbidity and mortality to a lesser extent, the etiology of prostate cancer remains largely unknown. Indeed, the only well-established risk factors to date are age, ethnicity and a family history of prostate cancer. We present, here, the rationale and design of the EPIdemiological study of Prostate CAncer (EPICAP), a population-based case-control study specifically designed to investigate the role of environmental and genetic factors in prostate cancer. The EPICAP study will particularly focused on the role of circadian disruption, chronic inflammation, hormonal and metabolic factors in the occurrence of prostate cancer.

METHODS/DESIGN

EPICAP is a population-based case-control study conducted in the département of Hérault in France. Eligible cases are all cases of prostate cancers newly diagnosed in 2012-2013 in men less than 75 years old and residing in the département of Hérault at the time of diagnosis. Controls are men of the same age as the cases and living in the département of Hérault, recruited in the general population.The sample will include a total of 1000 incident cases of prostate cancer and 1000 population-based controls over a 3-year period (2012-2014).The cases and controls are face-to-face interviewed using a standardized computed assisted questionnaire. The questions focus primarily on usual socio-demographic characteristics, personal and family medical history, lifestyle, leisure activities, residential and occupational history. Anthropometric measures and biological samples are also collected for cases and controls.

DISCUSSION

The EPICAP study aims to answer key questions in prostate cancer etiology: (1) role of circadian disruption through the study of working hours, chronotype and duration/quality of sleep, (2) role of chronic inflammation and anti-inflammatory drugs, (3) role of hormonal and metabolic factors through a detailed questionnaire, (4) role of individual genetic susceptibility of genes involved in biological pathways of interest. The EPICAP study will also allow us to study prognostic factors and tumor aggressiveness.Taken together, the EPICAP study will provide a comprehensive framework to go further in the understanding of prostate cancer occurrence and its prognosis.

Plasma and tissue insulin-like growth factor-I receptor (IGF-IR) as a prognostic marker for prostate cancer and anti-IGF-IR agents as novel therapeutic strategy for refractory cases: a review

Cancer database analysis indicates that prostate cancer is one of the most seen cancers in men meanwhile composing the leading cause of morbidity and mortality among developed countries. Current available therapies are surgery, radiotherapy and androgene ablation for prostate carcinoma. The response rate is as high nearly 90% however, most of these recur or become refractory and androgene independent (AI). Therefore recent studies intensified on molecular factors playing role on development of prostate carcinoma and novel treatment strategies targetting these factors and their receptors. Insulin-like growth factor-I (IGF-I) and its primary receptor insulin-like growth factor receptor-I (IGF-IR) are among these factors. Biologic functions and role in malign progression are primarily achieved via IGF-IR which is a type 2 tyrosine kinase receptor. IGF-IR plays an important role in mitogenesis, angiogenesis, transformation, apoptosis and cell motility. It also generates intensive proliferative signals leading to carcinogenesis in prostate tissue. So IGF-IR and its associated signalling system have provoked considerable interest over recent years as a novel therapeutic target in cancer. In this paper it is aimed to sum up the lately published literature searching the relation of IGF-IR and prostate cancer in terms of incidence, pathologic features, and prognosis. This is followed by a discussion of the different possible targets within the IGF-1R system, and drugs developed to interact at each target. A systems-based approach is then used to review the in vitro and in vivo data in the published literature of the following compounds targeting IGF-1R components using specific examples: growth hormone releasing hormone antagonists (e.g. JV-1-38), growth hormone receptor antagonists (e.g. pegvisomant), IGF-1R antibodies (e.g. CP-751,871, AVE1642/EM164, IMC-A12, SCH-717454, BIIB022, AMG 479, MK-0646/h7C10), and IGF-1R tyrosine kinase inhibitors (e.g. BMS-536942, BMS-554417, NVP-AEW541, NVP-ADW742, AG1024, potent quinolinyl-derived imidazo (1,5-a)pyrazine PQIP, picropodophyllin PPP, nordihydroguaiaretic acid Insm-18/NDGA). And the other end point is to yield an overview on the recent progress about usage of this receptor as a novel anticancer agent of targeted therapies in treatment of prostate carcinoma.

Dietary carbohydrate, glycemic index, glycemic load, and risk of prostate cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort

OBJECTIVE

To evaluate the associations between dietary carbohydrate, glycemic index (GI), glycemic load (GL), and incident prostate cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort.

METHODS

Between September 1993 and September 2000, 38,343 men were randomized to the screening arm of the trial at one of 10 PLCO centers. A food frequency questionnaire administered at baseline assessed usual dietary intake over the preceding 12 months. Prostate cancer was ascertained by medical follow-up of suspicious screening results and annual mailed questionnaires and confirmed with medical records. Cox proportional hazards regression was used to model the associations of carbohydrate, GI, and GL with prostate cancer risk.

RESULTS

During follow-up (median = 9.2 years), 2,436 incident prostate cancers were identified among 30,482 eligible participants. Overall, there were no associations of baseline carbohydrate, GI, or GL with incident prostate cancer in minimally or fully adjusted models. There were no associations when the 228 advanced and 2,208 non-advanced cancers were analyzed separately.

CONCLUSIONS

Dietary carbohydrate, GI, and GL were not associated with incident prostate cancer in PLCO. The narrow range of GI in this cohort may have limited our ability to detect associations, an issue that future studies should address.

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.

Leukemia, non-Hodgkin's lymphoma, and Wilms tumor in childhood: the role of birth weight

There is emerging evidence that higher birth weight is associated with increased risk of cancer, in particular childhood leukemia. The purpose of this paper is to study whether this correlation is also significant with other childhood cancer. For this, we conducted a case-control study including 410 childhood cancer patients and 1,575 matched controls to investigate birth weight as a risk factor for leukemia, Wilms tumor, and non-Hodgkin's lymphoma. The estimated risk for all cancers has been found to be statistically and significantly higher in birth weight of more than 4,000 g (odds ratio, 2.50 and 95% confidence intervals (CI), 1.72-3.63). For leukemia, the estimated risk was 1.86 (95% CI, 1.04-3.30), for non-Hodgkin lymphoma, 1.99 (95% CI, 1.08-3.69), and being more remarkable for Wilms tumor, 4.76 (95% CI, 2.73-8.28). Moreover, moderate increased risk of both leukemia and non-Hodgkin lymphoma was also associated with birth weight between 3,000 and 3,999 g. High birth weight was associated with all cancers also when adjusted by gestational age, length at birth, and gender (odds ratio, 6.10 and 95% CI, 1.15-32.57). No associations were found for maternal alcohol consumption during pregnancy, maternal smoking, or smoking by other people at home or presence of obstetric variables (e.g., gestational diabetes, preeclampsia, and abruptio placentae). The present study supports the hypothesis that high birth weight is an independent risk factor for childhood Wilms tumor, leukemia, and non-Hodgkin lymphoma. Further studies should explore biological reasons to explain this relationship and, ultimately, to expand our knowledge about prenatal influences on the occurrence of this disease.

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.

Enterolactone inhibits insulin-like growth factor-1 receptor signaling in human prostatic carcinoma PC-3 cells

Enterolactone, a major metabolite of plant-based lignans, has been shown to inhibit prostate cancer growth and development, but the mechanistic basis for its anticancer activity remains largely unknown. Activation of insulin-like growth factor-1 (IGF-1) receptor (IGF-1R) signaling is critical for prostate cancer cell growth and progression. This study examined whether the growth inhibitory effect of enterolactone was related to changes in the IGF-1/IGF-1R system in PC-3 prostate cancer cells. At nutritionally relevant concentrations (20-60 micromol/L), enterolactone inhibited IGF-1-induced activation of IGF-1R and its downstream AKT and mitogen-activated protein kinase/extracellular-signal regulated kinase signaling pathways. Inhibition of AKT by enterolactone resulted in decreased phosphorylation of its downstream targets, including p70S6K1 and glycogen synthase kinase-3 beta. Enterolactone also inhibited cyclin D1 expression. As a result, enterolactone inhibited proliferation and migration of PC-3 cells. Knockdown of IGF-1R by plasmids with siRNA (si) against IGF-1R mRNA resulted in inhibition of proliferation of PC-3 cells and cell numbers did not differ when the si-IGF-1R groups (cells transfected with plasmids containing siRNA against IGF-1R mRNA) were treated or untreated with enterolactone. These results suggest that enterolactone suppresses proliferation and migration of prostate cancer cells, at least partially, through inhibition of IGF-1/IGF-1R signaling. The finding of this study provides new insights into the molecular mechanisms that enterolactone exerts against prostate cancer.

Insulin receptor expression by human prostate cancers

BACKGROUND

Although recent laboratory and population studies suggest that prostate cancer may be responsive to insulin, there is a gap in knowledge concerning the expression of insulin receptors on benign or malignant prostate tissue.

METHODS

We immunostained 644 cores on tissue microarrays prepared from 29 prostate tissue samples without malignancies, 78 Gleason grade 3 cancers, 21 Gleason grade 4 cancers and 33 Gleason grade 5 cancers with antibodies against the insulin-like growth factor I receptor and the insulin receptor.

RESULTS

We observed immunoreactivity with both antibodies, which implies the presence of hybrid receptors as well as IGF-I receptors and insulin receptors. Insulin receptor staining intensity was significantly (P < 0.001) higher on malignant than benign prostate epithelial cells. Analysis of information from public gene expression databases confirmed that co-expression of insulin receptor mRNA and IGF-I receptor mRNA is common in prostate cancer specimens. RT-PCR methods provided evidence for the presence of mRNA for both IR-A and IR-B insulin receptor isoforms.

CONCLUSION

These observations document the presence of insulin receptors on primary human prostate cancers. The findings are relevant not only to ongoing clinical trials of drug candidates that target IGF-I and/or insulin receptors, but also to the hypothesis that obesity-associated hyperinsulinemia mediates the adverse effect of obesity on prostate cancer prognosis.

The insulin-like growth factor system and its receptors: A potential novel anticancer target

The current generation of novel anticancer therapies that are in preclinical and clinical development are based on exploiting our increasing understanding of the molecular and cellular basis of cancer development and progression. Accelerated rates of cell division and proliferation have been postulated to predispose to the development of malignant disease. The insulin-like growth factor (IGF) signaling system has an important physiological role in regulating cellular proliferation and apoptosis. This function has led to considerable interest in its relevance to neoplasia over the last decade. In this review, we give an overview of the IGF system physiology, discuss the epidemiological significance of IGF signaling and neoplasia, and review the preclinical and clinical studies in targeting IGF receptors as cancer therapies.

Molecular alterations in prostate cancer as diagnostic, prognostic, and therapeutic targets

Prostatic adenocarcinoma is extremely common in Western nations, representing the second leading cause of cancer death in American men. The recent application of increasingly sophisticated molecular approaches to the study of prostate cancer in this "postgenomic" era has resulted in a rapid increase in the identification of somatic genome alterations and germline heritable risk factors in this disease. These findings are leading to a new understanding of the pathogenesis of prostate cancer and to the generation of new targets for diagnosis, prognosis, and prediction of therapeutic response. Although we are still in the very early phase of clinical development, some of the molecular alterations identified in prostate cancer are being translated into clinical practice. The purpose of this review is to update the practicing surgical pathologist, and residents-in-training in pathology, regarding recent findings in the molecular pathobiology of prostate cancer. We will highlight some of the somatic molecular alterations associated with prostate cancer development and progression, with a focus on newer discoveries. In addition, recent studies in which new molecular diagnostic approaches have been applied in the clinic will be discussed.

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.

Insulin-like growth factor-I, insulin-like growth factor binding protein-3 and risk of benign prostate hyperplasia in the prostate cancer prevention trial

BACKGROUND

We investigated whether peptides involved in cellular proliferation and apoptosis, [insulin-like growth factor I (IGFI) and its major binding protein (insulin-like growth factor binding protein 3)], predicted risk of benign prostate hyperplasia (BPH).

METHODS

We conducted a nested-case-control study in the placebo arm of the prostate cancer prevention trial (PCPT). Cases (n = 727) were men with surgical or medical treatment for BPH; two or more IPSS scores >14; or two scores of at least five points over baseline one of which was >or=12. Controls (n = 727) were frequency matched by age to cases, reported no BPH treatment, and no IPSS score >8. Cases and controls remained on the PCPT placebo and were followed closely until their 7-year PCPT anniversary. Baseline serum was analyzed for IGFI and IGFBP3. Unconditional logistic regression and polytomous regression estimated the multivariate-adjusted odds ratio (OR) for BPH risk.

RESULTS

IGFBP3 was inversely and the IGFI:IGFBP3 ratio was positively associated with BPH risk, but findings were statistically significant only for men with severe symptoms (OR = 0.60, 95% CI = 0.40-0.90 for the fifth vs. first quintile of IGFBP3, P-trend = 0.01). Associations did not differ by age (<65 or >or=65 years), and there was a suggestion that the IGFI:IGFBP3 - BPH risk association may be stronger among overweight men.

CONCLUSIONS

A high IGFI:IGFBP3 ratio was associated with increased BPH risk, and high serum IGFBP3 was associated with decreased BPH risk among men with severe symptoms. These results confirm findings from other recent studies.

Inhibitory effects of nordihydroguaiaretic acid (NDGA) on the IGF-1 receptor and androgen dependent growth of LAPC-4 prostate cancer cells

BACKGROUND

Nordihydroguaiaretic acid (NDGA) is an inhibitor of the IGF-1 receptor (IGF-1R) in breast and other cancers, and concomitantly inhibits tumor growth both in cultured cells and animals. The current study evaluates the effect of NDGA on the androgen-stimulated growth of human prostate cancer cells.

METHODS

LAPC-4 prostate cancer cells in tissue culture were androgen starved for 3 days, 1 nM dihydrotestosterone (DHT) and other androgens were then added for up to 7 days, and cell proliferation measured. IGF-1R protein expression was measured by Western blot, and IGF-1R mRNA expression by quantitative PCR. IGF-1R receptor kinase activation was measured by ELISA.

RESULTS

After 7 days, LAPC-4 growth was doubled by 1 nM DHT. NDGA had a rapid effect to inhibit IGF-1R autophosphorylation induced by IGF-1. DHT increased the expression of IGF-1R protein and mRNA levels. Maximal IGF-1R protein levels were observed 3 days after the addition of androgen. In addition, NDGA, at 10 microM or less, inhibited DHT-induced proliferation in both cells grown in plates and cells grown in soft agar. Androgen receptor (AR) studies by FRET revealed that NDGA had no conformational effects on the AR in response to ligand.

CONCLUSIONS

NDGA blocks the DHT-induced growth of LAPC-4 prostate cancer cells by several mechanisms including rapid inhibition of the IGF-1R kinase, and a dose-dependent inhibition of androgen stimulation of IGF-1R expression. Clinical studies of this agent will determine its efficacy in the setting of androgen-dependent prostate cancer.

Glycemic status and risk of prostate cancer

BACKGROUND

To examine the risk of prostate cancer and glucose tolerance in a large, racially diverse cohort.

METHODS

We conducted a cohort study of 47,209 male members of Kaiser Permanente Northern California who had completed at least one Multiphasic Health Checkup (MHC) between 1964 and 1973. The MHC provided information on diabetes, serum glucose 1 h after a 75-g oral glucose challenge test, demographics, and other health conditions. Cox proportional hazards were used to estimate relative risks (RR) while adjusting for confounders.

RESULTS

During a median follow-up of 18.4 years, a total of 2,833 men developed prostate cancer. At baseline, 4.6% (n = 2,159) of the cohort had diabetes and 33% had serum glucose of >or=200 mg/dL. After adjusting for age, race, birth year, and body mass index, RR (95% confidence interval) of prostate cancer associated with 1-h serum glucose >or=200 mg/dL and diabetes were 0.90 (0.81-1.01) and 0.71 (0.62-0.79), respectively, when compared with those with serum glucose <140 mg/dL. During the first 10 years of follow-up, risk was increased among those with serum glucose >or=200 mg/dL or diabetes [RR (95% confidence interval), 1.42 (0.95-2.13) and 1.56 (0.91-2.67), respectively]. In contrast, inverse associations between serum glucose >or=200 mg/dL and diabetes and prostate cancer risk were observed [0.87 (0.77-0.97) and 0.68 (0.52-0.88), respectively] when follow-up began 10 years after MHC.

CONCLUSION

Our findings are consistent with the hypothesis that prostate cancer risk differs by time since diabetes diagnosis or occurrence of metabolic aberrations associated with impaired glucose tolerance.

CYP1B1 variants are associated with prostate cancer in non-Hispanic and Hispanic Caucasians

Cytochrome P450 1B1 (CYP1B1) is involved in the activation of many carcinogens and in the metabolism of steroid hormones. We compared allele, genotype and haplotype frequencies of six single-nucleotide polymorphisms (SNPs) within CYP1B1 among non-Hispanic Caucasians (496 cases and 498 controls) and Hispanic Caucasians (153 cases and 240 controls). In the Hispanic Caucasians, the GG genotype for rs1056836 decreased the risk for prostate cancer (PCa) when compared with the CC genotype [odds ratio (OR) = 0.31, P = 0.04, 95% confidence interval (CI) = 0.10–0.96]. Among non-Hispanic Caucasian men with more aggressive PCa, the prevalence of several SNPs (rs2567206, rs2551188, rs2617266, rs10012 and rs1056836) was significantly associated with the disease status. A common C-G-C-C-G-A haplotype for rs2567206-rs2551188-rs2617266-rs10012-rs1056836-rs1800440 showed an inverse association with PCa risk in Hispanic Caucasians (OR = 0.19, P = 0.04, 95% CI = 0.04–0.95) and with aggressive disease status (i.e. Gleason score ≥7) in non-Hispanic Caucasian cases (OR = 0.64, P = 0.008, 95% CI = 0.47–0.89). In the non-Hispanic Caucasian cases, a second major haplotype T-A-T-G-C-A was positively associated with the high-grade disease status (OR = 1.77, P = 0.002, 95% CI = 1.24–2.53). Our findings suggest that genetic polymorphisms in CYP1B1 may modify the risk for PCa and support the role of CYP1B1 as a candidate gene for PCa.

Association of RNASEL variants with prostate cancer risk in Hispanic Caucasians and African Americans

PURPOSE

The RNASEL gene at 1q25 has been identified as a hereditary prostate cancer susceptibility gene, but to date, no study has investigated the role of RNASEL variants in Hispanic Caucasian men with prostate cancer.

EXPERIMENTAL DESIGN

Two RNASEL common variants, located at amino acids 462 and 541, were genotyped in non-Hispanic Caucasian, Hispanic Caucasian, and African American prostate cancer cases and controls.

RESULTS

The RNASEL 462 AA genotype was found to increase prostate cancer risk over 4-fold in Hispanic Caucasians [odds ratio (OR), 4.43; 95% confidence interval (95% CI), 1.68-11.68; P = 0.003] and over 10-fold in African Americans (OR, 10.41; 95% CI, 2.62-41.40; P = 0.001) when compared with the GG genotype. Analysis of the RNASEL 541 variant showed that Hispanic Caucasian patients with the GG genotype had a statistically significant increase in their risk for developing prostate cancer when compared with the TT and GT genotypes (OR, 1.91; 95% CI, 1.16-3.14; P = 0.01). A common G-T haplotype for the combination of the RNASEL 462 and 541 variants was found to occur more frequently in controls compared with cases in African Americans (P = 0.04) but not in non-Hispanic Caucasians or Hispanic Caucasians.

CONCLUSIONS

This is the first study that investigates the association of prostate cancer risk with RNASEL variants in Hispanic men. Our data support the role of RNASEL as a predisposition gene for prostate cancer and showed a significant association between the RNASEL 462 variant and prostate cancer risk in African Americans and Hispanic Caucasians.

IMC-A12, a human IgG1 monoclonal antibody to the insulin-like growth factor I receptor

Targeted monoclonal antibody therapy is an important strategy in cancer therapeutics. Among the most promising characteristics of therapeutic targets are those that modulate the growth and survival of malignant neoplasms and their sensitivity to anticancer therapies. The insulin-like growth factor-I receptor (IGF-IR) is overexpressed in many types of solid and hematopoietic malignancies, and has been implicated as a principal cause of heightened proliferative and survival signaling. IGF-IR has also been shown to confer resistance to cytotoxic, hormonal, and targeted therapies, suggesting that therapeutics targeting IGF-IR may be effective against a broad range of malignancies. IMC-A12 (ImClone Systems Incorporated), a fully human monoclonal IgG1 antibody that binds with high affinity to the IGF-IR, inhibits ligand-dependent receptor activation and downstream signaling. IMC-A12 also mediates robust internalization and degradation of the IGF-IR. In human tumor xenograft models, IGF-IR blockade by IMC-A12 results in rapid and profound growth inhibition of cancers of the breast, lung, colon, and pancreas, and many other neoplasms. Although promising single-agent activity has been observed, the most impressive effects of targeting the IGF-IR with IMC-A12 have been noted when this agent was combined with cytotoxic agents or other targeted therapeutics. The results with IMC-A12 to date suggest that it may be an effective therapeutic in a diverse array of oncologic indications.

Dietary feeding of silibinin inhibits prostate tumor growth and progression in transgenic adenocarcinoma of the mouse prostate model

Herein, for the first time, we evaluated the chemopreventive efficacy of dietary silibinin against prostate cancer (PCa) growth and progression in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice from two different genetic backgrounds [C57BL/6 (TRAMP) x FVB; C57BL/6 (TRAMP) x C57BL/6]. At 4 weeks of age, mice were fed control or 0.1% to 1% silibinin-supplemented diets until 23 to 24 weeks of age. Silibinin-fed groups had a lower tumor grade and higher incidence of prostatic intraepithelial neoplasia (PIN) at the expense of a strong decrease in adenocarcinoma incidence. Prostate tissue showed a 47% (P < 0.001) decrease in proliferating cell nuclear antigen (PCNA)-positive cells and an approximately 7-fold (P < 0.001) increase in apoptotic cells at the highest silibinin dose. As potential mechanisms of silibinin efficacy, an approximately 50% (P < 0.05) decrease in insulin-like growth factor (IGF) receptor type I beta and an approximately 13-fold (P < 0.001) increase in IGF-binding protein 3 (IGFBP-3) protein levels were also observed. These changes were specific to tumors as they were not reflected in circulating IGF-IGFBP-3 system. Additionally, silibinin decreased protein expression of cyclin-dependent kinases (Cdk) by more than 90% (P < 0.001) with a concomitant increase in Cdk inhibitors, Cip1/p21 and Kip1/p27 (P < 0.05, for both). A dose-dependent decrease was also observed in cyclin B1, cyclin E, and cyclin A protein levels by silibinin. Together, these findings suggest that oral silibinin blocks PCa growth and progression at PIN stage in TRAMP mice via modulation of tumor IGF-IGFBP-3 axis and cell cycle regulation, and therefore it has practical and translational potential in suppressing growth and neoplastic conversion of PIN to PCa in humans.

The association between paternal prostate cancer and type 2 diabetes

Objective

Increasing evidence indicates that type 2 diabetic patients are at elevated risk for developing different kinds of cancers. However, diabetes mellitus may be a protective factor for prostate cancer since both were found to be negatively associated. Based on the same genetic background, parents of diabetic patients might show similar risks concerning cancers.

Research design and methods

We conducted a case-control study, where familiy history of 794 type 2 diabetic cases and 775 non-diabetic controls was ascertained. Then, we expanded our study up to 801 type 2 diabetic cases and 1267 non-diabetic controls.

Results

Concerning the 794 type 2 diabetic patients and 775 controls, we observed that cancer of cervix uteri was elevated among mothers of controls (odds ratio (OR) 0.19; 95% confidence interval (CI) 0.02 to 0.88; p = 0.033). Mothers of diabetic patients showed an increased history of cancers of the liver and biliary tract (OR 5.23; 95% CI 1.87 to 19.9; p = 0.0009) and stomach (OR 3.84; 95% CI 1.47 to 12.4; p = 0.0049). Pancreatic cancers were found to be elevated in fathers of diabetic patients (OR 4.92; 95% CI 1.07 to 46.7; p = 0.039). Most notably, a lower number of prostate cancers was observed in fathers of diabetic patients (OR 0.47; 95% CI 0.22 to 0.94; p = 0.032). Since diabetic patients were 14.3 years older than the controls, higher levels of cancer history among parents of diabetic patients would have been expected. Thus, the observed lower level of history of prostate cancer can be regarded as highly reliable.

The analysis of 801 type 2 diabetics and 1267 controls showed that cancer of stomach was elevated among mothers of controls (OR 2.67; p = 0.0106). In addition, stomach cancers were found to be elevated in fathers of diabetic patients (OR 2.10; p = 0.0141). In accordance with the previous investigation, we again obseved a lower number of prostate cancers in fathers of diabetic patients (OR 0.49; p = 0.0279).

However, the application of the statistical method of Mantel-Haenszel showed no significant result concerning any of the cancer histories.

Conclusion

Fathers of patients suffering from type 2 diabetes were diagnosed less frequently with prostate cancer compared to fathers of non-diabetic controls. As first-degree relatives, e.g. diabetic patients and their fathers, share 50% of their genes, it appears plausible that genetic factors may play an important role in the negative association between diabetes and prostate cancer. However, different statistic analyses showed controversial results concerning the effect of type 2 diabetes on prostate cancers.

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.

Features of the metabolic syndrome and prostate cancer in African-American men

BACKGROUND

Metabolic syndrome refers to a cluster of conditions that includes hypertension, dyslipidemia, central adiposity, and high blood glucose levels. Over the past decade, a growing body of literature suggests that metabolic syndrome may be associated with several different forms of cancer. Because prostate cancer risk is highest among African Americans, and these men, similarly, are more prone to developing specific features of the metabolic syndrome, including hypertension and type-2 diabetes, any relationships would have a significant impact on developing strategies for the primary prevention of prostate cancer.

METHODS

The Flint Men's Health Study is a community-based, case-control study of prostate cancer conducted exclusively among African Americans. Prostate cancer cases and controls completed an interviewer-administered questionnaire that asked about the respondent's history of high blood pressure and diabetes. All men also participated in a physical examination in which several measures of body composition, including waist circumference, were collected.

RESULTS

Hypertension was reported more commonly among men with prostate cancer (cases) compared with men in the control group (odds ratio [OR]. 2.4; 95% confidence interval [95% CI], 1.5-3.7), and cases were more likely to have a waist circumference >102 cm (OR, 1.8; 95% CI, 1.2-2.9). However, self-reported diabetes was not associated with prostate cancer risk. The men with prostate cancer also were more likely than controls to exhibit multiple syndrome characteristics (OR, 1.9; 95% CI, 1.2-3.0).

CONCLUSIONS

The current results indicated that features of the metabolic syndrome, specifically abdominal obesity and hypertension, are associated with prostate cancer in African-American men. This relationship, if it is proved causal, suggests that prevention or control of these conditions eventually may lead to a reduction in the incidence of prostate cancer in this high-risk minority group.

Impact of nutrients on insulin-like growth factor-I, insulin-like growth factor binding protein-3 and their ratio in African American and white males

OBJECTIVE

Higher levels of insulin-like growth factor-I (IGF-I) and lower levels of IGF binding protein-3 (IGFBP-3) have been associated with an increased risk of prostate cancer. Nutrition is known to partially regulate IGF levels and it is possible that nutritional factors mediate the impact of IGF levels on prostate cancer risk.

DESIGN

A cross-sectional analysis of the impact of nutritional factors measured by a dietary questionnaire on plasma levels of IGF-I, IGFBP-3 and their molar ratio. Multiple linear regression analysis was used to test for effects of nutrients on IGF levels.

SETTING

Prostate cancer screening at the Hollings Cancer Center in Charleston, South Carolina.

SUBJECTS

Ninety-five African American and 138 white males aged 33-83 years attending the screening.

RESULTS

In whites, intakes of total, saturated and monounsaturated fats were positively associated with an increase in the molar ratio, while there was no association in African Americans. In African Americans, we found that increasing intake of calcium and dairy servings was positively associated with IGF-I levels. Increased vegetable intake was positively associated with IGFBP-3 in African Americans, while there was no effect in whites. A higher percentage of alcohol in the total diet was significantly associated with a decrease in the molar ratio and an increase in IGFBP-3 in both groups.

CONCLUSIONS

Our results confirm previous findings of nutritional determinants of IGF levels. Additionally, we found the impact of several nutrients on IGF levels to be different in whites and African Americans, which warrants further investigation.

Serum levels of insulin-like growth factors (IGFs) and their binding proteins (IGFBPs), -1, -2, -3, in oral cancer

INTRODUCTION

Insulin-like growth factor (IGF) possesses mitogenic properties promoting cellular proliferation and inhibiting cellular apoptosis. Reported evidence suggests that cancer (non-oral) is associated with high circulating levels of IGF-1 and low levels of IGFBP-3.

AIMS

This study measured circulating levels of IFG-1 and IGFBPs -1, -2 and -3 in oral cancer patients.

METHODOLOGY

Blood was collected from surgical patients and controls. Samples were assayed for IGF-1 and IGFBPs -1, -2, -3, using commercially available enzyme-linked immunosorbant assays (ELISA; R&D Systems Europe, Oxon, UK).

RESULTS

Twenty-seven oral cancer and 31 age- and sex-matched patients were recruited. Mean IGF-1 and IGFBP-3 levels were significantly lower in cancer patients than controls (85.3 ng/ml and 2008 ng/ml versus 191 ng/ml and 2935 ng/ml, P<0.001). In contrast, levels of IGFBPs 1 and 2 were significantly higher in cancer patients than in controls. No significant association was demonstrated with tumour size or nodal metastases.

DISCUSSION

This study has shown that in contrast to other cancers, circulating levels of IGF-1 and IGFBP-3 may both be lowered in patients with head and neck cancer.

Haplotype-Based Association Studies of IGFBP1 and IGFBP3 with Prostate and Breast Cancer Risk: The Multiethnic Cohort

Collective evidence suggests that the insulin-like growth factor (IGF) system plays a role in prostate and breast cancer risk. IGF-binding proteins (IGFBP) are the principal regulatory molecules that modulate IGF-I bioavailability in the circulation and tissues. To examine whether inherited differences in the IGFBP1 and IGFBP3 genes influence prostate and breast cancer susceptibility, we conducted two large population-based association studies of African Americans, Native Hawaiians, Japanese Americans, Latinos, and Whites. To thoroughly assess the genetic variation across the two loci, we (a) sequenced the IGFBP1 and IGFBP3 exons in 95 aggressive prostate and 95 advanced breast cancer cases to ensure that we had identified all common missense variants and (b) characterized the linkage disequilibrium patterns and common haplotypes by genotyping 36 single nucleotide polymorphisms (SNP) spanning 71 kb across the loci ( approximately 20 kb upstream and approximately 40 kb downstream, respectively) in a panel of 349 control subjects of the five racial/ethnic groups. No new missense SNPs were found. We identified three regions of strong linkage disequilibrium and selected a subset of 23 tagging SNPs that could accurately predict both the common IGFBP1 and IGFBP3 haplotypes and the remaining 13 SNPs. We tested the association between IGFBP1 and IGFBP3 genotypes and haplotypes for their associations with prostate and breast cancer risk in two large case-control studies nested within the Multiethnic Cohort [prostate cases/controls = 2,320/2,290; breast cases (largely postmenopausal)/controls = 1,615/1,962]. We observed no strong associations between IGFBP1 and IGFBP3 genotypes or haplotypes with either prostate or breast cancer risk. Our results suggest that common genetic variation in the IGFBP1 and IGFBP3 genes do not substantially influence prostate and breast cancer susceptibility.

Risk factors for prostate cancer: A national case-control study

Statutory notification of cancer in New Zealand provided an opportunity to investigate risk factors for prostate cancer in a large national population-based case-control study. We analyzed data obtained from telephone interviews with 923 cases and 1,224 controls. For inclusion in the study, all subjects had to have been married at some time. We found an increased risk of prostate cancer among those with a history of prostate cancer in first degree relatives (RR 2.6; 95% CI, 1.9-3.7) and an increased risk of prostate cancer with length of marriage among men married only once and still married at interview. For a consecutive subgroup of 550 cases and 819 controls, data on height and weight at age 20 and at 5 years before interview were collected. Men less than or equal to 1.7 m in height at age 20 years had a lower risk of prostate cancer than men taller at that age. There was no association between weight or body mass index and risk of prostate cancer.

What can geography tell us about prostate cancer?

One of the most striking characteristics of prostate cancer is the degree of geographic variation in its patterns of occurrence and progression; this variation is apparent at local, national, and international levels. Although geographic theory, methods, and data are increasingly utilized for public health research, epidemiologic research in prostate cancer etiology and progression has not taken full advantage of the spatial sciences as partner disciplines. This article reviews the known factors influencing the biology and epidemiology of prostate cancer and some of the ways in which findings to date have benefited from geography. A model is presented for geographically integrated research in prostate cancer, with discussion of how spatially referenced data and methods could enhance approaches to answering remaining questions in prostate cancer.

GH/IGF e neoplasia: o que há de novo nesta associação

Estudos in vitro e em animais sugerem que os membros do sistema insulin-like growth factors (IGFs), incluindo IGF-I, IGF-II, receptores de IGF-I e IGF-II (IGF-IR e IGF-IIR), e as IGF-binding proteins (IGFBPs) podem ter um importante envolvimento no desenvolvimento e na progressão de neoplasias. Mais especificamente, as IGFs promovem a progressão do ciclo celular e inibem a apoptose tanto por ação direta com outros fatores de crescimento como por ação indireta interagindo com outros sistemas moleculares intracelulares envolvidos na promoção e/ou progressão do câncer. Além disso, inúmeros estudos epidemiológicos têm sugerido que concentrações elevadas das IGFs, independente das alterações nas IGFBPs, podem estar associadas a um aumento no risco de desenvolver determinadas neoplasias. Esta revisão tem como objetivo apresentar o envolvimento do sistema IGF na regulação tumoral, os principais estudos epidemiológicos realizados e o risco de desenvolvimento de neoplasia em pacientes (com ou sem história pessoal de neoplasia prévia) que receberam hormônio de crescimento (rhGH). É importante salientar que o uso clínico de rhGH, nas indicações aprovadas internacionalmente, é seguro e não existem evidências, até o momento, da associação com o desenvolvimento de neoplasias.

IGF-I and IGFBP-3 polymorphisms and risk of prostate cancer

BACKGROUND

Insulin-like growth factor-I (IGF-I) is a potent mitogen for both normal and malignant prostate epithelial cells. The majority of circulating IGF-I is bound in a complex with IGF binding protein-3 (IGFBP-3), which in turn limits IGF-I bioavailability. Multiple studies suggest that higher IGF-I and/or lower IGFBP-3 serum levels are positively associated with prostate cancer risk. Several polymorphisms within the IGF-I and IGFBP-3 coding regions have been associated with increased serum protein levels.

METHODS

To ascertain the potential relationship between serum levels and polymorphism, and prostate cancer risk, we investigated the role of two polymorphisms the IGF-I cytosine-adenosine (CA)-repeat and the IGFBP-3 Ala32Gly, and prostate cancer in a population-based, case-control, study of middle-aged men.

RESULTS

We found no significant association between the IGFBP-3 Ala32Gly polymorphism and prostate cancer risk, even though the presence of at least one Gly allele did correlate with increased serum levels of IGFBP-3. For IGF-I, more controls (42%) than cases (38%) were homozygous for 19-CA-repeats (odds ratio, OR = 0.85; 95% confidence interval (CI) = 0.66-1.09). After stratifying by disease characteristics, 19-CA-repeat homozygous men displayed a decreased risk of low-grade disease (OR = 0.50; 95% CI = 0.27-0.93), but no associations were observed with more aggressive features of disease. Additionally, there was no correlation between mean serum IGF-I protein levels and IGF-I genotype in controls.

CONCLUSIONS

Further evaluation of the IGF-I CA-repeat polymorphism and prostate cancer is necessary to determine if the modest risk reduction associated with the 19-CA-repeat homozygous state is observed in other study populations.

Effects of 9-cis-retinoic acid on the insulin-like growth factor axis in former smokers

PURPOSE

Insulin-like growth factor (IGF) axis has been associated with the risk of lung cancer. 9-cis-retinoic acid (9-cis-RA) has shown potential chemopreventive activities in former smokers. This study was designed to evaluate the effects of 9-cis-RA on IGF axis in former smokers to identify any benefit the retinoid may have in preventing lung cancer.

PATIENTS AND METHODS

Serum concentrations of IGF-I, IGF binding protein (IGFBP)-3, and their molar ratio (IGF-I/IGFBP-3) were measured with radioimmunoassay kits in stored blood samples from the participants of an original chemoprevention trial. The participants had ceased smoking for at least 12 months and were randomly assigned to receive 3 months of daily oral 9-cis-RA (100 mg) or placebo. All statistical tests were two-sided.

RESULTS

A total of 111 samples from the study's baseline and 84 samples from the 3 months treatment were analyzed. The serum concentrations of IGF-I and IGF-I/IGFBP-3 at baseline were significantly lower in female than in male participants. After 3 months of treatment, the serum level of IGF-I and IGF-I/IGFBP-3 were significantly lower in the 9-cis-RA group than in the placebo group (P = .03 and P < .01, respectively), but the IGFBP-3 level was significantly higher (P = .03).

CONCLUSION

9-cis-RA treatment modulated the IGF axis in former smokers, suggesting that the IGF axis is a potential target for the chemopreventive activities of 9-cis-RA and that the serum concentrations of IGF, IGFBP-3, and IGF-I/IGFBP-3 could serve as surrogate end point biomarkers of 9-cis-RA treatment.

A germ line mutation that delays prostate cancer progression and prolongs survival in a murine prostate cancer model

Circulating insulin-like growth factor-I (IGF-I) levels have been shown to be related to risk of prostate cancer in epidemiologic studies. While specific genetic loci responsible for interindividual variation in circulating IGF-I levels in normal men have not been identified, candidate genes include those involved in the growth hormone (GH)-IGF-I axis such as the hypothalamic factors GH releasing hormone (GHRH) and somatostatin and their receptors. To investigate the role of the GH-IGF-I axis on in vivo prostate carcinogenesis and neoplastic progression, we generated mice genetically predisposed to prostate cancer (the TRAMP model) to be homozygous for lit, a mutation that inactivates the GHRH receptor (GHRH-R) and reduces circulating levels of GH and IGF-I. The lit mutation significantly reduced the percentage of the prostate gland showing neoplastic changes at 35 weeks of age (P=0.0005) and was also associated with improved survival (P<0.01). These data provide an example of a germ line mutation that reduces risk in an experimental prostate carcinogenesis model. The results suggest that prostate carcinogenesis and progression may be influenced by germ line variation of genes encoding signalling molecules in the GH-IGF-I axis.

Serum Insulin-Like Growth Factor-I Levels and Prostatic Intraepithelial Neoplasia: A Clue to the Relationship Between IGF-I Physiology and Prostate Cancer Risk

Serum insulin-like growth factor-I (IGF-I) levels at the higher end of the reference range have been associated with increased risk for the future development of prostate cancer. We determined whether high serum IGF-I levels are associated with precancerous lesions of the prostate. We conducted a case-control study to determine whether high serum IGF-I levels were associated with the presence of high-grade prostatic intraepithelial neoplasia (HGPIN) among patients who presented for prostate biopsy because of an abnormal serum prostate-specific antigen level or digital rectal exam. We measured serum IGF-I and insulin-like growth factor binding protein-3 (IGFBP-3) prior to prostate biopsy and compared them between 103 men with HGPIN (cases) and 205 men with normal prostate histology (controls). The mean IGF-I level in patients with HGPIN (130.2 ng/mL) was significantly higher compared with controls (118.8 ng/mL, P = 0.01). The mean IGFBP-3 level in patients with HGPIN (2,393.9 ng/mL) was also higher compared with controls (2,276.0 ng/mL, P = 0.06). After adjusting for age, prostate-specific antigen, digital rectal examination, and ethnic background, the odds ratio for a HGPIN diagnosis among men in the highest relative to the lowest quartile of serum IGF-I level was 1.94 (95% confidence interval, 1.0-3.7; P = 0.04). The potential association between a high serum IGF-I level and the presence of HGPIN may represent an important clue to understanding the basis for the relationship between IGF-I physiology and prostate cancer risk. Larger studies will be required to confirm this relationship.

Role of lycopene and tomato products in prostate health

Epidemiological evidence associating the decreased risk of prostate cancer with frequent consumption of tomato products inspired us to conduct a small intervention trial among patients diagnosed with prostate adenocarcinoma. Tomato sauce pasta was consumed daily for 3 weeks before their scheduled prostatectomy, and biomarkers of tomato intake, prostate cancer progression and oxidative DNA damage were followed in blood and the available prostate tissue. The whole food intervention was so well accepted by the subjects that the blood lycopene (the primary carotenoid in tomatoes responsible for their red color) doubled and the prostate lycopene concentration tripled during this short period. Oxidative DNA damage in leukocytes and prostate tissues was significantly diminished, the latter mainly in the tumor cell nuclei, possibly due to the antioxidant properties of lycopene. Quite surprising was the decrease in blood prostate-specific antigen, which was explained by the increase in apoptotic death of prostate cells, especially in carcinoma regions. Prostate cancer cell cultures (LNCaP) were also sensitive to lycopene in growth medium, which caused an increased apoptosis and arrested the cell cycle. A possible explanation of these promising results may reside in lycopene effects on the genes governing the androgen stimulation of prostate growth, cytokines and on the enzymes producing reactive oxygen species, all of which were recently discovered by nutrigenomic techniques. Other phytochemicals in tomato may act in synergy with lycopene to potentiate protective effects and to help in the maintenance of prostate health.

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.

Diabetes Mellitus and the Risk of Prostate Cancer in Italy

OBJECTIVE

We investigated the relation between diabetes and the risk of prostate cancer, as epidemiological results are controversial.

METHODS

A hospital-based case-control study was conducted in Italy between 1991 and 2002. Cases were 1294 men, aged <75 years, with incident histologically confirmed prostate cancer, and controls were 1451 men, aged <75 years, admitted to hospital for acute non-neoplastic diseases. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were estimated using unconditional multiple logistic regression models.

RESULTS

No material association between diabetes and prostate cancer was observed, with a multivariate OR of 1.02 (95%CI 0.75-1.40). Prostate cancer was not related to time since diagnosis of diabetes (OR 0.82 and 0.97 for <5 and >/=15 years since diagnosis respectively). The OR were respectively 1.63 (95%CI 0.70-3.81) and 0.96 (95%CI 0.68-1.34) in men diagnosed with diabetes at age <45 or >/=45 years. The risk estimates were similar across strata of age at interview, body mass index and, among cases, of Gleason score.

CONCLUSIONS

This study shows no material association between diabetes and prostate cancer risk.

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.

Longitudinal Associations of Age, Anthropometric and Lifestyle Factors with Serum Total Insulin-Like Growth Factor-I and IGF Binding Protein-3 Levels in Black and White Men: the CARDIA Male Hormone Study

Although several studies have assessed cross-sectional correlates of serum insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3), there are no longitudinal studies of the correlates of long-term changes in these measures. We examined the 8-year longitudinal associations of age, body mass index (BMI), waist circumference, physical activity, number of cigarettes smoked per day, and alcohol intake with serum total IGF-I and IGFBP-3 concentrations in 622 Black and 796 White male participants of the Coronary Artery Risk Development in Young Adults Study who were ages 20 to 34 years at the time of the first IGF measurement. In generalized estimating equation analyses, IGF-I decreased by 5.6 and 5.9 ng/mL per year increase in age for Black and White men, respectively (P&lt; 0.0001), and there was an age-related decline in IGFBP-3 that was stronger in Whites (P &lt; 0.0001) than Blacks (P = 0.21). Average IGF-I (β = −17.51 ng/mL) and IGFBP-3 (β = −355.4 ng/mL) levels across all three exams were lower in Blacks than Whites (P &lt; 0.0001). Increased BMI was associated with decreased IGF-I (P &lt; 0.0002), but was not associated with IGFBP-3. There were no meaningful associations with waist circumference. Increased physical activity was associated with a decrease in IGFBP-3 (P &lt; 0.05), but was not associated with IGF-I. In White men, there were weak inverse associations between the number of cigarettes smoked per day with IGF-I (P=0.15) and with IGFBP-3 (P = 0.19), and in Black men, increased alcohol intake was associated with a decrease in IGF-I (P = 0.011). In conclusion, these results support an age-related decline and Black-White difference in serum IGF-I and IGFBP-3 levels. Importantly, they suggest that IGF-I and/or IGFBP-3 levels could be influenced by changes in BMI, and perhaps by physical activity, alcohol intake, and cigarette smoking.

Finding prostate cancer susceptibility genes

Prostate cancer is a heterogeneous disease with multiple loci contributing to susceptibility. Traditionally, genome-wide scans using high-risk families have utilized stratification by number of affected individuals, family history of other cancers, or family age at diagnosis to improve genetic homogeneity. In addition to locus heterogeneity, for later onset diseases such as prostate cancer, a major limitation to mapping efforts is that key parental DNA samples are rarely available. The lack of available samples from upper generations reduces inheritance information, and as a result, the standard 10-cM genome scan does not provide full power to detect linkage. To increase the ability to find disease-associated loci, much denser genome-wide scans must be undertaken in multiple ethnic groups. In addition, new ways of defining homogenous subsets of families need to be developed.

Lycopene reduced gene expression of steroid targets and inflammatory markers in normal rat prostate

Epidemiological evidence links consumption of lycopene, the red carotenoid of tomato, to reduced prostate cancer risk. We investigated the effect of lycopene in normal prostate tissue to gain insight into the mechanisms, by which lycopene can contribute to primary prostate cancer prevention. We supplemented young rats with 200 ppm lycopene for up to 8 wk, measured the uptake into individual prostate lobes, and analyzed lycopene-induced gene regulations in dorsal and lateral lobes after 8 wk of supplementation. Lycopene accumulated in all four prostate lobes over time, with all-trans lycopene being the predominant isoform. The lateral lobe showed a significantly higher total lycopene content than the other prostate lobes. Transcriptomics analysis revealed that lycopene treatment mildly but significantly reduced gene expression of androgen-metabolizing enzymes and androgen targets. Moreover, local expression of IGF-I was decreased in the lateral lobe. Lycopene also consistently reduced transcript levels of proinflammatory cytokines, immunoglobulins, and immunoglobulin receptors in the lateral lobe. This indicates that lycopene reduced inflammatory signals in the lateral prostate lobe. In summary, we show for the first time that lycopene reduced local prostatic androgen signaling, IGF-I expression, and basal inflammatory signals in normal prostate tissue. All of these mechanisms can contribute to the epidemiologically observed prostate cancer risk reduction by lycopene.

Lycopene: modes of action to promote prostate health

Epidemiological evidence strongly suggests that lycopene consumption contributes to prostate cancer risk reduction. Preclinical studies show that lycopene acts via different mechanisms, which have the potential to cooperate in reducing the proliferation of normal and cancerous prostate epithelial cells, in reducing DNA damage, and in improving oxidative stress defense. The mechanisms include inhibition of prostatic IGF-I signaling, IL-6 expression, and androgen signaling. Moreover, lycopene improves gap-junctional communication and induces phase II drug metabolizing enzymes as well as oxidative defense genes. These findings provide plausible explanations for the epidemiological findings how lycopene can contribute to reduced prostate cancer risk. The novel finding that lycopene reduces local androgen signaling in the prostate suggests also efficacy in prevention of benign prostate hyperplasia. Intervention trials in humans are required to finally prove clinical efficacy of the lycopene molecule in prostate health.

Diet and cancer prevention

Dietary effects are presumed to underlie many of the large international differences in incidence seen for most cancers. Apart from alcohol and a few micronutrients, however, the role of specific nutritional factors remains ill-defined. The evidence for a role of energy balance, physical inactivity, and obesity has strengthened, while for dietary fat it has weakened. Phytochemicals such as folate, lycopene and flavonoids are still the subject of active research. As the mechanisms underlying human carcinogenesis are better understood, dietary research will focus increasingly on intermediate markers such as the insulin-like growth factors and potentially carcinogenic metabolites.