Role of the insulin-like growth factor family in cancer development and progression

Diet and breast cancer

Obesity, overweight, and a sedentary lifestyle-all common conditions in breast cancer patients-are likely to be associated with poor survival and poor quality of life in women with breast cancer. Diet-related factors are thought to account for about 30% of cancers in developed countries. Most studies of diet and healthcare have focused on the role of single nutrients, foods, or food groups in disease prevention or promotion. Recent cancer guidelines on nutrition and physical activity emphasize diets that promote maintenance of a healthy body weight and a prudent dietary pattern that is low in red and processed meats and high in a variety of vegetables, fruits, and whole grains. Except for dietary fat, few nutritional factors in adult life have been associated with breast cancer. Extensive data from animal model research, international correlations linking fat intake and breast cancer rates, and case-control studies support the hypothesis that a high-fat diet is conducive to the development of breast cancer in postmenopausal women. Conflicting findings from cohort studies, however, have created uncertainty over the role of dietary fat in breast cancer growth and recurrence. Results from large-scale nutritional intervention trials are expected to resolve such issues. As new and improved data on dietary factors and patterns accumulate, dietary guidelines for cancer risk reduction will become more focused.

Anti-oestrogenic chemoprevention of breast cancer-the need to progress

Clinical trials of the selective oestrogen receptor modulator (SERM), tamoxifen, have shown an early reduction in risk of breast cancer in healthy women of approximately 40%, but with associated risks and benefits to normal tissues. An overall clinical benefit and the identification of the women at risk of breast cancer who may gain benefit from tamoxifen has not been clearly established. The identification of those women at risk who are most likely to gain benefit, and the development of other SERMs and aromatase inhibitors which might be more active and have a more beneficial spectrum of activity on normal tissues in healthy women is essential, if the aim of preventing breast cancer in healthy women is to be achieved.

Methodologic and statistical considerations regarding use of biomarkers of nutritional exposure in epidemiology

In nutritional epidemiology, accurate quantification of nutritional exposure is critical. Even moderate flaws in measurement can lead to sizeable distortions in estimations of the effects of exposure. In many situations, this will lead to inaccurate direct estimation of exposure effects. In others, it will make it difficult to control for the confounding effects of nutritional exposure. Biomarkers offer important opportunities to advance research in nutritional epidemiology; their objectivity and potentially greater accuracy give them the potential to substantially lessen distortions that might result from imperfect measurements. Clearly, the accuracy of biomarkers as indicators of nutritional exposure is critical to their value. It is likely that establishing the accuracy of biomarkers will require some reference to self-reports, even if those reports are not as accurate as the biomarkers they are used to test. The goal of this paper is to describe aspects of accuracy-reproducibility, reliability and validity-as they apply to biomarkers in nutritional epidemiology.

Identification of bioactive molecules by adipogenesis profiling of organic compounds

An important step in the postgenomic drug discovery is the construction of high quality chemical libraries that generate bioactive molecules at high rates. Here we report a cell-based approach to composing a focused library of biologically active compounds. A collection of bioactive non-cytotoxic chemicals was identified from a divergent library through the effects on the insulin-induced adipogenesis of 3T3-L1 cells, one of the most drastic and sensitive morphological alterations in cultured mammalian cells. The resulting focused library amply contained unique compounds with a broad range of pharmacological effects, including glucose-uptake enhancement, cytokine inhibition, osteogenesis stimulation, and selective suppression of cancer cells. Adipogenesis profiling of organic compounds generates a focused chemical library for multiple biological effects that are seemingly unrelated to adipogenesis, just as genetic screens with the morphology of fly eyes identify oncogenes and neurodegenerative genes.

Evolutionary medicine: from dwarf model systems to healthy centenarians?

Restriction of the number of calories consumed extends longevity in many organisms. In rodents, caloric restriction decreases the levels of plasma glucose and insulin-like growth factor I (IGF-1) and postpones or attenuates cancer, immunosenescence, and inflammation without irreversible side effects. In organisms ranging from yeast to mice, mutations in glucose or IGF-I-like signaling pathways extend life-span but also cause glycogen or fat accumulation and dwarfism. This information suggests a new category of drugs that could prevent or postpone diseases of aging with few adverse effects.

Serum insulin-like growth factor binding protein-3/prostate-specific antigen ratio is a useful predictive marker in patients with advanced prostate cancer

BACKGROUND

Insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) play an important role in regulation of prostate cancer cell growth. We studied the prognostic significance of serum IGF-1 and IGFBP-3 levels, and IGF-1/prostate-specific antigen (PSA) and IGFBP-3/PSA ratios in patients with prostate cancer.

METHODS

Serum levels of IGF-1, IGFBP-3, and PSA were determined in 112 patients diagnosed with prostate cancer. Serum samples from 32 patients with histologically confined benign prostatatic hyperplasia (BPH) served as control.

RESULTS

Serum IGF-1 levels were significantly higher in advanced prostate cancer (n = 84) than in BPH patients (P < 0.01). IGFBP-3 levels were significantly lower in patients with advanced prostate cancer than in localized tumor (n = 28) or BPH (P < 0.05, each). Univariate analysis showed that serum PSA, IGF-1/PSA ratio, IGFBP-3/PSA ratio, T, N and M classifications correlated significantly with relapse-free survival of advanced prostate cancer patients treated with hormonal therapy. Multivariate analysis identified IGFBP-3/PSA ratio as the only significant variable for relapse-free survival (odds ratio 5.81, 95% CI 1.57-21.51). IGFBP-3/PSA ratio was also an independent predictor of cause-specific survival (stepwise analysis, odds ratio 4.86, P < 0.01).

CONCLUSIONS

Our results suggested that IGFBP-3/PSA ratio might be a useful prognostic marker of advanced prostate cancer.

Session: whole cereal grains, fibre and human cancer wholegrain cereals and cancer in Italy

The relationship between frequency of consumption of whole-grain foods and cancer risk has been analysed using data from an updated series of case-control studies conducted in Northern Italy between 1983 and 1997. The overall dataset included the following incident histologically-confirmed neoplasms: oral cavity and pharynx 524, oesophagus 410, stomach 745, colon 955, rectum 625, liver 435, gallbladder 65, pancreas 402, larynx 388, soft tissue sarcomas 217, breast 3412, endometrium 750, ovary 971, prostate 127, bladder 431, kidney 190, thyroid 428, Hodgkin's disease 201, non-Hodgkin's lymphomas 529, multiple myelomas 185. Controls were 10 058 patients admitted to hospital for acute non-neoplastic conditions unrelated to long-term modifications in diet, tobacco or alcohol use. The multivariate odds ratios for the highest category of wholegrain cereal consumption were 0.3-0.5 for upper digestive tract and respiratory neoplasms and colon, 0.6 for rectum and liver, 0.4 for gallbladder, 0.8 for pancreas, 0.2 for soft tissue sarcomas, 0.9 for breast and endometrium, 0.7 for ovary, 0.7 for prostate, 0.4 for bladder and kidney, 1.1 for thyroid and about 0.5 for lymphomas and 0.6 for myelomas. In this population whole-grain food consumption is an indicator of reduced risk of several neoplasms.

Polymorphism of the insulin gene is associated with increased prostate cancer risk

High insulin levels are linked with increased cancer risk, including prostate cancer. We examined the associations between prostate cancer with polymorphisms of the insulin gene (INS) and its neighbouring genes, tyrosine-hydroxylase and IGF-II (TH and IGF2). In this study, 126 case-control pairs matched on age, race, and countries of origin were genotyped for +1127 INS-PstI in INS, -4217 TH-PstI in TH, and +3580 IGF2-MspI in IGF2. The homozygous CC genotype of +1127 INS-PstI occurred in over 60% of the population. It was associated with an increased risk of prostate cancer in nondiabetic Blacks and Caucasians (OR=3.14, P=0.008). The CC genotype was also associated with a low Gleason score <7 (OR=2.60, P=0.022) and a late age of diagnosis (OR=2.10, P=0.046). Markers in the neighbouring genes of INS showed only null to modest associations with prostate cancer. The polymorphism of INS may play a role in the aetiology of prostate cancer. Given the high prevalence of the CC genotype and its association with late age of onset of low-grade tumours, this polymorphism may contribute to the unique characteristics of prostate cancer, namely a high prevalence of indolent cancers and the dramatic increase in incidence with age.

Energy restriction early in life and colon carcinoma risk: results of The Netherlands Cohort Study after 7.3 years of follow-up

BACKGROUND

This study evaluated the effects of severe undernutrition during adolescence and subsequent colon carcinoma risk.

METHODS

The authors evaluated The Netherlands Cohort Study on Diet and Cancer (NLCS) among 62,573 women and 58,279 men aged 55-69 years at baseline. Information on diet and risk factors was collected by questionnaire in 1986. Additional information was collected concerning residence during the hunger winter (1944-1945), the World War II years (1940-1944), and father's employment status during the economic depression of 1932-1940, which were used as indicators of exposure. After 7.3 years of follow-up, 807 colon carcinoma cases (388 females and 419 males) were available for analysis.

RESULTS

Multivariate analysis showed that both men and women who had lived in a western city in 1944-1945 had a decreased colon carcinoma risk (men: relative risk [RR] = 0.85, 95% confidence interval [CI] = 0.62-1.16; women: RR = 0.80, 95% CI = 0.59-1.09). No association between colon carcinoma risk and urban versus rural residence was found during the war years (1940-1944). Having an unemployed father during the economic depression (1932-1940) was also associated with a small decrease in colon carcinoma risk for men (RR = 0.90, 95% CI =0.62-1.31) and women (RR = 0.75, 95% CI 0.49-1.14). In subgroup analyses, a decreased colon carcinoma risk for men and women who were in their adolescent growth spurt and living in a western city during the hunger winter of 1944-1945 was noted (men: RR = 0.72, 95% CI = 0.31-1.65; women: RR = 0.88, 95% CI = 0.40-1.96). No associations were statistically significant because of the limited study size.

CONCLUSIONS

In the current study, a weak inverse relation was found between energy restriction early in life and subsequent colon carcinoma risk for men and women. However, these findings need replication in a larger study.

Breast cancer prevention trials using retinoids

Retinoids have been studied as chemopreventive agents in clinical trials. Given their ability to inhibit mammary carcinogenesis in preclinical models. Fenretinide has extensively been investigated because of its favorable toxicological profile in humans. In a phase III secondary prevention trial, fenretinide showed a trend to a reduction of second breast malignancies in premenopausal women but not in postmenopausal women. This pattern was associated with a similar modulation of circulating IGF-I. A trend towards a reduction of ovarian cancer was also noted. Biomarker studies of fenretinide or novel selective retinoids alone and in combination with different nuclear receptor ligands are being conducted. These studies provide a model for testing the safety and tolerability, pharmacokinetics and pharmacodynamics, and biomarker modulation in high-risk women, and offer clues as to both the pathophysiology of carcinogenesis and the drug mechanisms of action, and help select new compounds and doses for testing in large randomized studies.

Dietary glycemic index, glycemic load and ovarian cancer risk: a case-control study in Italy

BACKGROUND

Dietary carbohydrates vary in their ability to raise blood glucose and insulin levels, which, in turn, influence levels of sex hormones and insulin-like growth factors. We analyzed the effect of type and amount of carbohydrates on ovarian cancer risk, using the glycemic index (GI) and the glycemic load (GL) measurement in a large case-control study conducted in Italy.

MATERIALS AND METHODS

Cases included 1031 women with incident, histologically confirmed epithelial ovarian cancer, from four Italian regions. Controls included 2411 women admitted to the same hospital networks for acute, non-neoplastic conditions. Average daily GI and GL were calculated from a validated food frequency questionnaire. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were computed using multiple logistic regression.

RESULTS

Ovarian cancer was directly associated with dietary GI (OR for highest versus lowest quartile = 1.7, 95% CI 1.3-2.1) and GL (OR = 1.7, 95% CI 1.3-2.1). The associations were observed in pre- and postmenopausal women, and they remained consistent across strata of major covariates identified.

CONCLUSIONS

This study supports the hypothesis of a direct association between GI and GL and ovarian cancer risk and, consequently, of a possible role of hyperinsulinemia/insulin resistance in ovarian cancer development.

Fibre intake and laryngeal cancer risk

BACKGROUND

Consumption of vegetables, fruit and whole grain cereals has been inversely related to laryngeal cancer risk. Among the potential protective agents found in these foods, information on dietary fibres and laryngeal cancer risk are scanty.

PATIENTS AND METHODS

A multi-centric, hospital-based case-control study was conducted on 527 patients with squamous-cell carcinoma of the larynx and 1,297 non-neoplastic controls. Cases and controls, frequency matched by age, sex and study centre, were interviewed using a validated food frequency questionnaire.

RESULTS

Compared with the lowest quintile of fibre intake, the odds ratios (ORs) for the highest quintile were 0.3 [95% confidence interval (CI) 0.2-0.4] for total fibre, 0.3 (95% CI 0.2-0.5) for soluble non-cellulose polysaccharides (NCP) and for total insoluble fibre, including cellulose (OR = 0.3, 95% CI 0.2-0.4) and insoluble NCP (OR = 0.4, 95% CI 0.3-0.7). The ORs were 0.2 (95% CI 0.1-0.4) for fibre from vegetables, 0.5 (95% CI 0.3-0.7) from fruit and 1.1 (95% CI 0.6-1.9) from grains. The inverse association observed was similar among different subsites of laryngeal cancer, and consistent across strata of various covariates.

CONCLUSIONS

This study found a strong inverse association between fibre intake and laryngeal cancer risk, which points to fibre as one of the beneficial components of vegetables and fruit.

Serum insulin-like growth factors, insulin-like growth factor-binding protein-3, and risk of lung cancer death: a case-control study nested in the Japan Collaborative Cohort (JACC) Study

To elucidate the roles of insulin-like growth factors (IGFs) in the development of lung cancer, we conducted a case-control study nested within the Japan Collaborative Cohort Study. Serum samples were collected at baseline from 39140 men and women between 1988 and 1990. We measured serum IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3) in 194 case subjects who subsequently died from lung cancer during an 8-year follow-up and in 9351 controls. The odds ratios (ORs), adjusted for smoking and other covariates, were smaller with higher levels of IGF-II and IGFBP-3. The ORs across quartiles were 0.41 (95% confidence interval [CI], 0.27-0.63), 0.47 (0.31-0.71), and 0.67 (0.46-0.98) for IGF-II (trend P=0.018), and 0.55 (95% CI, 0.37-0.81), 0.54 (0.36-0.82), and 0.67 (0.45-1.01) for IGFBP-3 (trend P=0.037). These peptides were not independently related to lung cancer risk when mutually adjusted. The risk was increased in the highest vs. the lowest quartile of IGF-I only after controlling for IGFBP-3 (OR, 1.74; 95% CI, 1.08-2.81). Limiting subjects to those followed for 3 years strengthened the negative associations of IGF-II and IGFBP-3, whereas the ORs for IGF-I generally decreased. A higher level of circulating IGFBP-3 and / or IGF-II may decrease lung cancer risk. Elevated serum IGF-I may increase the risk, but this could partly be attributable to latent tumors.

Physical activity and cancer prevention: etiologic evidence and biological mechanisms

Scientific evidence is accumulating on physical activity as a means for the primary prevention of cancer. Nearly 170 observational epidemiologic studies of physical activity and cancer risk at a number of specific cancer sites have been conducted. The evidence for decreased risk with increased physical activity is classified as convincing for breast and colon cancers, probable for prostate cancer, possible for lung and endometrial cancers and insufficient for cancers at all other sites. Despite the large number of studies conducted on physical activity and cancer, most have been hampered by incomplete assessment of physical activity and a lack of full examination of effect modification and confounding. Several plausible hypothesized biological mechanisms exist for the association between physical activity and cancer, including changes in endogenous sexual and metabolic hormone levels and growth factors, decreased obesity and central adiposity and possibly changes in immune function. Weight control may play a particularly important role because links between excess weight and increased cancer risk have been established for several sites, and central adiposity has been particularly implicated in promoting metabolic conditions amenable to carcinogenesis. Based on existing evidence, some public health organizations have issued physical activity guidelines for cancer prevention, generally recommending at least 30 min of moderate-to-vigorous intensity physical activity on > or =5 d/wk. Although most research has focused on the efficacy of physical activity in cancer prevention, evidence is increasing that exercise also influences other aspects of the cancer experience, including cancer detection, coping, rehabilitation and survival after diagnosis.

Prostate cancer: another aspect of the insulin-resistance syndrome?

Insulin resistance and compensatory hyperinsulinaemia are thought to be the underlying factors in the metabolic or insulin-resistance syndrome and can be controlled by diet and exercise. Hyperinsulinaemia has been shown to have a direct effect on the live, suppressing the production of sex hormone-binding globulin (SHBG) and insulin-like growth factor-binding proteins 1 and 2 (IGFBP-1, -2) while stimulating the production of insulin-like growth factor 1 (IGF-1). These factors have been proposed to be important modulators of hormone-related cancers, such as prostate cancer. Men adopting a low-fat diet and daily exercise reduced their levels of serum insulin and IGF-1, while increasing their levels of IGFBP-1 and sex hormone-binding globulin (SHBG). Cell-culture studies with LNCaP prostate cancer cells showed apoptosis of tumour cells and a reduction in serum-stimulated cell growth in the post diet and exercise serum. These results suggest that prostate cancer may be another aspect of the insulin-resistance syndrome and that adopting a low-fat diet combined with regular exercise may reduce the risk for prostate and other hormone-related cancers. This needs to be tested with prospective studies.

Tomatoes, lycopene intake, and digestive tract and female hormone-related neoplasms

Tomato consumption showed a consistent inverse relation with the risk of digestive tract neoplasms in Italy in an integrated series of studies conducted in the 1980s. Another series of case-control studies was conducted between 1992 and 1999 in different areas of Italy. Cases were patients below age 80 with incident, histologically confirmed cancer of the oral cavity and pharynx (n = 754), esophagus (n = 304), colorectum (n = 1953), breast (n = 2529), and ovary (n = 1031). The comparison group involved, overall, over 5000 patients below age 80 with acute, non-neoplastic, nonhormone-related diseases, unrelated to long-term diet modifications and admitted to the same network of hospitals. Information was collected in hospital by trained interviewers using a validated food frequency questionnaire, including 78 foods or groups of foods, various alcoholic beverage, and fat-intake pattern. The multivariate relative risk (RR) of oral, pharyngeal, and esophageal cancer decreased across subsequent levels of lycopene intake to reach 0.7 (95% confidence interval [CI] 0.4-1.0) for oral and pharyngeal, and 0.7 (95% CI 0.4-1.1) for esophageal cancer in the highest quintile of intake. Both trends in risk were of borderline statistical significance. With reference to colorectal, breast, and ovarian cancer, although no consistent association was observed for lycopene (RR = 1.0 for colorectal, 1.2 for breast, and 1.1 for ovary in the highest quintile), tomato intake was inversely and significantly related with colorectal cancer (RR = 0.8). The inverse relation between lycopene and upper digestive tract neoplasms was not explained by alcohol or tobacco, sociodemographic factors, or total energy intake. The interpretation of such an inverse relation, however, remains open to discussion because it may be related to an effect of lycopene due to its antioxidant effect and/or a potential role of lycopene in decreasing insulin growth factor I, which is a promoter in the process of carcinogenesis.

Insulin-like growth factor (IGF)-I, IGF-binding protein-3 and colorectal adenomas in Japanese men

Several epidemiological studies have found that high levels of plasma insulin-like growth factor (IGF)-I and low levels of IGF-binding protein (IGFBP)-3 are related to an increased risk of colorectal cancer or late-stage adenomas. We examined the relation of body mass index, fasting and 2-h postload plasma glucose levels and plasma concentrations of IGF-I and IGFBP-3 to colorectal adenomas in middle-aged Japanese men. The study subjects comprised 157 cases of histologically diagnosed colorectal adenomas and 311 controls with normal colonoscopy or non-polyp benign lesions in a consecutive series of 803 men receiving a preretirement health examination at two hospitals of the Self Defense Forces (SDF). After adjustment for rank in the SDF, hospital, smoking and IGFBP-3, a statistically nonsignificant modest increase in the prevalence odds of colorectal adenomas was observed for the highest versus the lowest quartile level of IGF-I. The increase was slightly greater with further adjustment for 2-h glucose concentrations (adjusted odds ratio 1.8, 95% confidence interval 1.0-4.5, trend P=0.06). Men with high levels of IGFBP-3 showed only a minimal decrease in risk after adjustment for IGF-I. The association with IGF-I was less evident for advanced adenomas (>5 mm in size or tubulovillous/villous). Fasting and 2-h glucose and body mass index were more strongly positively associated with colorectal adenomas than IGF-I, especially with advanced adenomas, independently of IGF-I and IGFBP-3. The findings suggest that plasma IGF-I and IGFBP-3 may be involved in colorectal tumorigenesis regardless of the stage in growth of adenoma, but not as a mediator for the effects of being overweight or of hyperglycemia.

Type I insulin-like growth factor receptor expression on colorectal adenocarcinoma cell lines is decreased in response to the chemopreventive agent N-acetyl-l-cysteine

Increased expression of the type I insulin-like growth factor receptor (IGF-1R) is associated with colon cancer, while the antioxidant N-acetyl-l-cysteine (NAC) is known to suppress colonic proliferation. We demonstrate that NAC down-regulates the expression of IGF-1R on three colorectal adenocarcinoma cell lines (HT29, SW480, and LoVo). NAC also abrogates the proliferative effect of IGF-I on HT29 cells. This indicates a novel mechanism for the therapeutic effects of NAC.

Circulating levels of insulin-like growth factor-I and risk of ovarian cancer

Insulin-like growth factor (IGF)-I, a mitogenic and anti-apoptotic peptide, has been implicated in the development of several cancers. We hypothesized that high circulating IGF-I concentrations may be associated with an increased risk of ovarian cancer. A case-control study was nested within 3 prospective cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). One hundred thirty-two women with primary invasive epithelial ovarian cancer diagnosed at least 1 year after blood donation were case subjects. For each case, 2 control subjects were selected, matching the case subject on cohort, menopausal status, age and date of recruitment (n = 263). Only women who did not use exogenous hormones at blood donation were included in the study. There was no association between IGF-I concentrations and ovarian cancer risk in the study group as a whole. In analyses restricted to subjects who had developed ovarian cancer at a young age (<55), circulating IGF-I was directly and strongly associated with ovarian cancer risk (OR = 4.97; 95% CI = 1.22-20.2 for the top vs. the bottom IGF-I tertile after adjustment for parity, BMI categories and smoking). There was no significant association of IGF binding protein-3 with ovarian cancer risk. We found a strong direct relationship between circulating IGF-I levels and risk of developing ovarian cancer before age 55. Additional, larger studies of this association are needed to provide more precise estimates of effect.

Overexpression of interleukin-15 induces skeletal muscle hypertrophy in vitro: implications for treatment of muscle wasting disorders

Interleukin-15 (IL-15) is a novel anabolic factor for skeletal muscle which inhibits muscle wasting associated with cancer (cachexia) in a rat model. To develop a cell culture system in which the mechanism of the anabolic action of IL-15 on skeletal muscle could be examined, the mouse C2 skeletal myogenic cell line was transduced with a retroviral expression vector for IL-15 and compared to sister cells transduced with a control vector. Overexpression of IL-15 induced fivefold higher levels of sarcomeric myosin heavy chain and alpha-actin accumulation in differentiated myotubes. Secreted factors from IL-15-overexpressing myogenic cells, but not from control cells, induced increased myofibrillar protein accumulation in cocultured control myotubes. IL-15 overexpression induced a hypertrophic myotube morphology similar to that described for cultured myotubes which overexpressed the well-characterized anabolic factor insulin-like growth factor-I (IGF-I). However, in contrast to IGF-I, the hypertrophic action of IL-15 on skeletal myogenic cells did not involve stimulation of skeletal myoblast proliferation or differentiation. IL-15 induced myotube hypertrophy at both low and high IGF-I concentrations. Furthermore, in contrast to IGF-I, which stimulated only protein synthesis under these culture conditions, IL-15 both stimulated protein synthesis and inhibited protein degradation in cultured skeletal myotubes. These findings indicate that IL-15 action on skeletal myogenic cells is distinct from that of IGF-I. Due to the ability of IGF-I to stimulate cell division and its association with several forms of cancer, controversy exists concerning the advisability of treating cachexia or age-associated muscle wasting with IGF-I. Administration of IL-15 or modulation of the IL-15 signaling pathway may represent an alternative strategy for maintaining skeletal muscle mass under these conditions.

Effect of budesonide on the methylation and mRNA expression of the insulin-like growth factor 2 and c-myc genes in mouse lung tumors

The use of surrogate end-point biomarkers could help in the development of chemopreventive agents. To define potential surrogate end-point biomarkers, the ability of budesonide to decrease mRNA expression of the insulin-like growth factor-2 (Igf-II) and c-myc genes and to cause the remethylation of the genes was investigated in lung tumors. Lung tumors were induced in female strain A mice by administering i.p. 16 mg/kg vinyl carbamate for 2 consecutive wk or by a single dose of 100 mg/kg benzo[a]pyrene (B[a]P). Thirty-four weeks later, the mice given vinyl carbamate received budesonide (0.6 or 2.4 mg/kg diet) for 7 d and then were killed. Mice were killed 24 wk after administration of B[a]P. The mRNA expression of the Igf-II and c-myc genes was increased in lung tumors relative to normal lung tissue. Budesonide decreased mRNA expression of both genes in tumors. The methylation status of 27 CpG sites in the differentially methylated region 2 in the Igf-II gene was determined with the bisulfite-treated DNA-sequencing procedure. The numbers of methylated CpG sites were 17-21 in normal lung (70.4 +/- 2.6%); 0-2, and 1-2 in lung tumors induced by vinyl carbamate and B[a]P (4.9 +/- 1.2% and 4.6 +/- 1.2%, respectively); and 4-5 or 7-16 in tumors after treatment with 0.6 or 2.4 mg/kg budesonide (16.0 +/- 1.2% and 46.2 +/- 5.1%, respectively). Thus, lung tumors had strikingly less methylated CpG sites than normal lung tissue, while even limited treatment with budesonide resulted in remethylation of the CpG sites in tumors. With HpaII digestion followed by Southern blot analysis, the internal cytosine of CCGG sites in the c-myc gene was found to be methylated in normal lung tissue, whereas some of the sites were unmethylated in lung tumors. Treatment for 7 d with budesonide resulted in the remethylation of these sites. In conclusion, mouse lung tumors showed decreased methylation of the Igf-II and c-myc genes that was associated with increased expression of these genes. Budesonide treatment caused remethylation and decreased expression of both genes. The results support the possibility of using decreased mRNA expression and remethylation of the Igf-II and c-myc genes as biomarkers for the efficacy of budesonide.

Resistance to trastuzumab: a necessary evil or a temporary challenge?

The aim of this review article is to examine the potential mechanisms of resistance to trastuzumab. In the clinical setting, when trastuzumab is given as a single agent for first-line treatment of HER2-overexpressing metastatic breast cancer, it is associated with a 40% objective response rate. In the remaining cases, no tumor regression is observed, although HER2 protein is overexpressed and/or the corresponding gene is amplified. Hence, some other factors besides HER2 must play a role in determining the level of sensitivity to trastuzumab. The identification of the potential mechanisms of resistance to trastuzumab can be very helpful for the development of new compounds, which might overcome that resistance and/or have additive/synergistic antitumor effect when given in association with trastuzumab. Moreover, thorough understanding of the HER2 pathway is essential to the identification of new predictive markers of response to trastuzumab that will help to better define the patients who are most likely to benefit from this drug.

Effects of genetic blockade of the insulin-like growth factor receptor in human colon cancer cell lines

BACKGROUND & AIMS

Insulin-like growth factor (IGF)-I receptor (IGF-Ir) signaling is required for maintenance of growth and tumorigenicity of several tumor types. We have previously shown successful therapy in a lung cancer xenograft model using an adenovirus expressing antisense IGF-Ir. In this study, we sought to better dissect the mechanism and develop potentially more effective IGF-Ir-targeted therapeutics by developing and testing tetracycline-regulated and recombinant adenoviruses expressing dominant negative receptors.

METHODS

Truncated IGF-I receptors (IGF-Ir/tf; 482 and 950 amino acids long, respectively [IGF-Ir/482st and IGF-Ir/950st]) were cloned into tetracycline-regulated vectors and recombinant adenoviruses and then studied in colorectal cancer cells. We assessed the effect of IGF-Ir/tf on signaling blockade, colony formation, stress response (serum starvation and heat), chemotherapy-induced apoptosis, and in vivo therapeutic efficacy in xenografts.

RESULTS

Activation of IGF-Ir/tf expression by withdrawal of tetracycline suppressed tumorigenicity both in vitro and in vivo and up-regulated stressor-induced apoptosis. It effectively blocked both IGF-I- and IGF-II-induced activation of Akt-1. IGF-Ir/tf expression increased chemotherapy-induced apoptosis, and this combination therapy was very effective against tumors in mice. These findings were confirmed in a therapy model against established tumors using adenoviruses expressing IGF-Ir/tf. Moreover, IGF-Ir/482st was more effective than IGF-Ir/950st because of its bystander effect.

CONCLUSIONS

Anti-tumor activity of IGF-Ir/tf is mediated through inhibition of Akt-1 and enhances the efficacy of chemotherapy. Adenovirus IGF-Ir/482st may be a useful anticancer therapeutic for colorectal carcinoma.

Anti-oestrogenic prevention of breast cancer--the make or break point

Clinical trials have shown that giving anti-oestrogens to healthy women can reduce the early incidence of breast cancer by approximately 40%. However, the large numbers of women treated, compared with the few who get breast cancer, together with the not insignificant toxicity and the unknown long-term clinical benefits and risks, makes this strategy of prevention versus treatment precarious. So how can we improve the odds for the successful use of endocrine chemoprevention?

The effect of diet on risk of cancer

Diet-related factors are thought to account for about 30% of cancers in developed countries. Obesity increases the risk of cancers in the oesophagus, colorectum, breast, endometrium, and kidney. Alcohol causes cancers of the oral cavity, pharynx, larynx, oesophagus, and liver, and causes a small increase in the risk of breast cancer. Adequate intakes of fruit and vegetables probably lower the risk for several types of cancer, especially cancers of the gastrointestinal tract. The importance of other factors, including meat, fibre, and vitamins, is not yet clear. Prudent advice is to eat a varied diet including plenty of fruit, vegetables, and cereals to maintain a healthy bodyweight with the help of regular physical activity and to restrict consumption of alcohol.

Identification of differentially expressed genes in pulmonary adenocarcinoma by using cDNA array

No clear patterns in molecular changes underlying the malignant processes in lung cancer of different histological types have been found so far. To identify critical genes in lung cancer progression we compared the expression profile of cancer related genes in 14 pulmonary adenocarcinoma patients with normal lung tissue by using the cDNA array technique. Principal component analyses (PCA) and permutation test were used to detect the differentially expressed genes. The expression profiles of 10 genes were confirmed by semi-quantitative real-time RT-PCR. In tumour samples, as compared to normal lung tissue, the up-regulated genes included such known tumour markers as CCNB1, PLK, tenascin, KRT8, KRT19 and TOP2A. The down-regulated genes included caveolin 1 and 2, and TIMP3. We also describe, for the first time, down-regulation of the interesting SOCS2 and 3, DOC2 and gravin. We show that silencing of SOCS2 is not caused by methylation of exon 1 of the gene. In conclusion, by using the cDNA array technique we were able to reveal marked differences in the gene expression level between normal lung and tumour tissue and find possible new tumour markers for pulmonary adenocarcinoma.

Activation of BAD by therapeutic inhibition of epidermal growth factor receptor and transactivation by insulin-like growth factor receptor

Novel cancer chemotherapeutics are required to induce apoptosis by activating pro-apoptotic proteins. Both epidermal growth factor (EGF) and insulin-like growth factor (IGF) provide potent survival stimuli in many epithelia, and activation of their receptors is commonly observed in solid human tumors. Here we demonstrate that blockade of the EGF receptor by a new drug in phase III clinical trails for cancer, ZD1839, potently induces apoptosis in mammary epithelial cell lines and primary cultures, as well as in a primary pleural effusion from a breast cancer patient. We identified the mechanism of apoptosis induction by ZD1839. We showed that it prevents cell survival by activating the pro-apoptotic protein BAD. Moreover, we demonstrate that IGF transactivates the EGF receptor and that ZD1839 blocks IGF-mediated phosphorylation of MAPK and BAD. Many cancer therapies kill tumor cells by inducing apoptosis as a consequence of targeting DNA; however, the threshold at which apoptosis can be triggered through DNA damage is often different from that in normal cells. Our results indicate that by targeting a growth factor-mediated survival signaling pathway, BAD phosphorylation can be manipulated therapeutically to induce apoptosis.

Plasma from patients undergoing major open surgery stimulates in vitro tumor growth: Lower insulin-like growth factor binding protein 3 levels may, in part, account for this change

BACKGROUND

Plasma from laparotomized mice has been shown to stimulate in vitro tumor growth when compared to results with preoperative plasma. This study assessed the effect of plasma from patients who underwent major open (OS) or laparoscopic surgery (LS) on in vitro tumor cell growth.

METHODS

Eighty-four patients undergoing major abdominal surgery were studied (45 OS, 39 LS). Peripheral blood was collected preoperatively (PreOP) and on days 1 (POD1) and 3 (POD3) after operation. HT29 human colon cancer cells were plated with samples of the plasma. Proliferation was assessed by cell counts and the bromodeoxyuridine incorporation assay. Insulin-like growth factor binding protein 3 was detected in plasma by Western blot analysis.

RESULTS

Increased mitogenic activity was noted in POD1 OS plasma when compared to PreOP OS plasma results (P <.005). This increase correlated with the length of incision (r = 0.58, P <.01). No differences were noted when the PreOP LS and POD1 LS results were compared or for any of the POD3 versus PreOP comparisons.

CONCLUSIONS

Major OS is associated with alterations in plasma composition that promote HT29 tumor cell proliferation in vitro. As shown, this effect was due, at least in part, to surgery-related depletion of insulin-like growth factor binding protein 3 in peripheral blood.

Metastasis to bone: causes, consequences and therapeutic opportunities

The most common human cancers --lung, breast and prostate -- have a great avidity for bone, leading to painful and untreatable consequences. What makes some cancers, but not others, metastasize to bone, and how do they alter its physiology? Some of the molecular mechanisms that are responsible have recently been identified, and provide new molecular targets for drug development.

Trans-10,cis-12-conjugated linoleic acid inhibits Caco-2 colon cancer cell growth

A commercially available mixture of conjugated linoleic acid (CLA) isomers decreases colon cancer cell growth. We compared the individual potencies of the two main isomers in this mixture [cis-9,trans-11 (c9t11) and trans-10,cis-12 (t10c12)] and assessed whether decreased cell growth is related to changes in secretion of insulin-like growth factor II (IGF-II) and/or IGF-binding proteins (IGFBPs), which regulate Caco-2 cell proliferation. Cells were incubated in serum-free medium with different concentrations of the individual CLA isomers. t10c12 CLA dose dependently decreased viable cell number (55 +/- 3% reduction 96 h after adding 5 microM t10c12 CLA). t10c12 CLA induced apoptosis and decreased DNA synthesis, whereas c9t11 CLA had no effect. Immunoblot analysis of 24-h serum-free conditioned medium using a monoclonal anti-IGF-II antibody revealed that Caco-2 cells secreted both a mature 7,500 molecular weight (M(r)) IGF-II and higher M(r) forms of IGF-II. The levels of the higher M(r) and the mature form of IGF-II were decreased 50 +/- 3% and 22 +/- 2%, respectively, by 5 microM t10c12 CLA. c9t11 CLA had no effect. Ligand blot analysis of conditioned medium using 125I-labeled IGF-II revealed that t10c12 CLA slightly decreased IGFBP-2 production; c9t11 CLA had no effect. Exogenous IGF-II reversed t10c12 CLA-induced growth inhibition and apoptosis. These results indicate that CLA-inhibited Caco-2 cell growth is caused by t10c12 CLA and may be mediated by decreasing IGF-II secretion in Caco-2 cells.

Hormones and prostate cancer: current perspectives and future directions

Prostate cancer is the most commonly diagnosed non-skin cancer in men in most western countries. Despite the high morbidity and mortality from prostate cancer, its etiology remains obscure. Although compelling laboratory data suggest a role for androgens in prostate carcinogenesis, most epidemiologic data on humans are inconclusive. To provide insights and directions for future epidemiologic research on hormones and prostate cancer, this review focuses on current perspectives of serum-based studies and polymorphisms in relevant hormone-related genes. We highlight the importance of methodologic studies and investigations of hormone levels in the prostatic tissue to help clarify the often-contradictory data on serologic studies. We recommend careful analysis and cautious interpretation of studies of genetic markers, including repeats and single nucleotide polymorphisms (SNPs), as false positive and negative results may arise in many current and future studies with limited statistical power and non-representative samples from the population. The review also highlights the reasons to perform functional analyses of SNPs, a critical and often under-appreciated component of molecular epidemiologic investigations. The time is ripe for large-scale multidisciplinary investigations that incorporate molecular genetics, biochemistry, histopathology, and endocrinology into traditional epidemiologic studies. Such collaboration will lead to a deeper understanding of the etiologic pathways of prostate cancer, ultimately yielding better preventive, diagnostic, and therapeutic strategies.

Chemoprevention of breast cancer: implications for postmenopausal women

Estrogen administration is associated with reduction in perimenopausal symptoms and the risk for several conditions affecting postmenopausal women. As estrogen administration also increases the risk for breast cancer, a common dilemma facing many women and their physicians is whether to use estrogen replacement therapy (ERT), a selective estrogen receptor modulator (SERM) that antagonises estrogenic effects in breast tissue but retains some estrogen agonist properties in other organs, or neither. For women with average to moderate risk of breast cancer and with perimenopausal symptoms, ERT may be the best short-term choice. For very high-risk women (>1% per year) with menopausal symptoms, alternatives to ERT might be offered and tried first. A diagnosis of ductal carcinoma in situ or invasive breast cancer within the last 2 to 5 years should be considered a relative contraindication for ERT unless the tumour was estrogen receptor negative. High-risk women without menopausal symptoms are the best candidates for the only currently approved drug for breast cancer risk reduction, tamoxifen. Although the drug is approved for women with a 5-year risk of breast cancer > or = 1.7% (0.34% per year), postmenopausal women most likely to experience a favourable benefit/risk ratio are those with a Gail estimated risk of >0.5% per year without a uterus or >1% per year if they retain their uterus. Tamoxifen should not be used in women with prior history of thromboembolic or precancerous uterine conditions. Tamoxifen is often used in Europe in conjunction with transdermal ERT in hysterectomised women without obvious loss of efficacy or increased risk of thromboembolism. Raloxifene is a second generation SERM with estrogen-like agonist effects on bone but with less uterine estrogen agonist activity than tamoxifen. Raloxifene may have less potent breast antiestrogenic effects than tamoxifen, particularly in a moderate- to high-estrogen environment. Raloxifene is approved for use in reducing risk of osteoporosis, but not breast cancer. Whether it is as effective as tamoxifen in reducing breast cancer risk in postmenopausal women is the subject of a current trial. All women regardless of breast cancer risk are advised to employ nonpharmacological risk reduction measures, including normalisation of bodyweight, exercise, adequate calcium and vitamin D intake, and avoidance of smoking and alcohol. The preventive options are best weighed during an individualised consultation where a woman's menopausal symptoms and risk for breast cancer and other diseases can be examined, and the options for improving postmenopausal health can be discussed.

Insulin-like growth factors and risk of benign prostatic hyperplasia

BACKGROUND

Insulin-like growth factors (IGFs) have potent growth mitogenic and anti-apoptotic effects on prostate tissue, whereas IGF binding proteins (IGFBPs) inhibit growth of prostatic tissue. The IGF axis has been implicated in prostate cancer risk, but its role in benign prostatic hyperplasia (BPH) is unclear.

METHODS

Plasma levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3 were determined from the fasting bloods of 206 BPH cases admitted for treatment and 306 randomly selected population controls in Shanghai, China.

RESULTS

Relative to the lowest tertile, men in the highest tertile of IGF-I levels had a significantly elevated risk of BPH (odds ratio [OR] = 2.80, 95% confidence interval [95% CI] = 1.60-4.92; P(trend) < 0.001). Results for IGF-I were more pronounced after adjustment for serum androgens. In contrast, men in the highest IGFBP-3 tertile had a significantly reduced risk (OR = 0.40; 95% CI = 0.23-0.69; P(trend) < 0.001). No associations of BPH with IGF-II and IGFBP-1 were observed.

CONCLUSION

As has been previously observed for prostate cancer, we found that IGF-I and IGFBP-3 are associated with BPH risk in China. Further investigation is needed to elucidate the role of the IGF axis in BPH etiology.

Breast cancer chemoprevention: current challenges and a look toward the future

There is a need to develop new prevention agents for breast cancer risk reduction that would have fewer side effects than the approved agent, tamoxifen, and/or would be effective in preventing estrogen receptor-negative or tamoxifen-resistant, estrogen receptor-positive breast cancers. There also is a need to improve the accuracy of present risk assessment models and to incorporate tissue-based biomarkers to supplement risk prediction tools. Candidate risk biomarkers include the serum hormones insulin-like growth factor-1 and its binding protein-3, mammographic breast density, nipple aspirate fluid production, and breast tissue evidence of proliferative breast disease (intraepithelial neoplasia). A variety of techniques have been developed to randomly sample breast tissue to detect precancerous changes and/or detect modulation of proliferation in response to a prevention agent. Based on molecular abnormalities observed in breast intraepithelial neoplasia, a number of drug classes and combinations are suggested as potential chemoprevention approaches. Clinical trial models have been developed to select the appropriate drug dose for subsequent biomarker modulation chemoprevention trials in which the use of surrogate endpoint biomarkers as indicators of efficacy is being explored. If these biomarkers can be validated and shown to reliably predict and monitor response in phase I/II prevention trials, and if favorable modulation is correlated with subsequent decreased cancer incidence, biomarkers may replace cancer incidence as the endpoint in future phase III trials, dramatically reducing the time and expense associated with new prevention drug development.

Upper abdominal obesity, insulin resistance and breast cancer risk

PURPOSE

A majority of prospective studies show breast cancer risk to be higher in obese postmenopausal women with upper abdominal adiposity than in those with overall adiposity. The evidence is more limited and inconsistent in the case of premenopausal women. The review examines evidence that aberrant insulin signalling may be involved in the promotion of mammary carcinogenesis. The aetiology and concomitants of abdominal visceral obesity are examined.

MECHANISMS

Clinical and experimental evidence suggests that the higher breast cancer risk associated with greater abdominal visceral obesity may be related to aberrant insulin signalling through the insulin receptor substrate 1 pathway, leading to insulin resistance, hyperinsulinaemia and increased concentrations of endogenous oestrogen and androgen. The putative role of aberrant insulin signalling in the promotion of mammary carcinogenesis may help to explain clinical relationships between breast cancer risk and age at menarche, pregnancies and onset of obesity.

CONCLUSION

Overall adiposity in women adversely affects breast cancer risk mainly by greater exposure of mammary epithelial tissue to endogenous oestrogen. Upper abdominal adiposity appears to involve an additional effect related to the presence of insulin resistance. Aetiological factors in the development of hyperinsulinaemic insulin resistance are still uncertain but may involve aberrant susceptibility genes in adipocyte insulin receptors or in the insulin receptor substrate 1 pathway. Epigenetic factors are also likely to contribute, including high free fatty acid levels and obesity. Dietary fatty acids, particularly polyunsaturated fatty acids, are known to regulate adipocyte differentiation through the nuclear peroxisome proliferator-activated receptor gamma, and may also have a role in insulin resistance. These aetiological factors are likely to be relevant to the high risk of postmenopausal breast cancer in industrialised Western populations.

Case-control study of anthropometric measures and breast cancer risk

A population-based case-control study of 1,233 incident breast cancer cases and 1,241 controls was conducted in Alberta between 1995 and 1997 to examine the influence of anthropometric factors on the risk of breast cancer using several newly derived variables. Data on current height, weight and waist and hip circumference were collected by interviewers using standardized methods. Respondents recalled their body weight at each decade from age 20 to the referent year. Several variables were estimated, and unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations for any of the estimated variables with breast cancer risk for premenopausal women (462 cases, 475 controls) were found. The results for postmenopausal women (771 cases, 762 controls) in the highest vs. lowest quartiles were, for waist circumference, OR = 1.30 (95% CI 0.97-1.73); waist-hip ratio, OR = 1.43 (95% CI 1.07-1.93); weight gain since age 20, OR = 1.35 (05% CI 1.01-1.81); difference between maximum and minimum weights over adult lifetime, OR = 1.56 (95% CI 1.16-2.08); and the reference weight minus the minimum weight since age 20, OR = 1.47 (95% CI 1.10-1.97). Statistically significant trends in risk were observed for these variables. Effect modification with hormone replacement therapy use was found for most variables assessed for postmenopausal women, with much stronger associations found among never-users compared to ever-users. We found strong evidence that waist-hip ratio and weight gained over lifetime, as assessed by different variables, are postmenopausal breast cancer risk factors. These effects were independent of dietary intake and lifetime total physical activity.

Decreased production of insulin-like growth factor-binding protein (IGFBP)-6 by transfection of colon cancer cells with an antisense IGFBP-6 cDNA construct leads to stimulation of cell proliferation

BACKGROUND

: Previously, we have observed that highly unsaturated dietary (n-3) fatty acids inhibit cell proliferation in conjunction with stimulation of insulin-like growth factor-binding protein (IGFBP)-6 secretion in Caco-2 cells, a human colon carcinoma cell line.

METHODS

: To test the converse hypothesis that inhibition of endogenous IGFBP-6 secretion stimulates Caco-2 cell proliferation, cells were transfected with the antisense IGFBP-6 expression construct or pcDNA3 vector only, and single colonies resistant to G418 sulfate were isolated.

RESULTS

: Our initial studies indicated that three antisense clones grew faster and produced less IGFBP-6 than two pcDNA3 clones, so antisense IGFBP-6 #5 and pcDNA3 #8 were selected for further detailed analysis. Both the control and antisense clones grew in serum-free medium reaching a plateau density at day eight. However, the antisense clone grew at a rate faster than that of the control and reached a final density that was 31 +/- 3% higher than the control. Northern blot, ligand blot and immunoblot analyses revealed that accumulation of IGFBP-6 mRNA and concentrations of IGFBP-6 peptide produced by the antisense clone were decreased by 80-90% compared to the control. The doubling times of the antisense and control clones were 21.9 +/- 0.4 and 24.8 +/- 0.3 h (P < 0.05), respectively. Exogenous IGF-I and IGF-II (0.2-200 nmol/L) stimulated proliferation of both the control and antisense clones in a dose-dependent manner, but the relative potency and efficacy of IGF-II was higher in the antisense clone compared to the control. These results indicate that suppression of IGFBP-6 secretion correlates with an increase in the basal rate of Caco-2 cell growth.

CONCLUSIONS

: Our findings are consistent with the hypothesis that IGFBP-6 inhibits cell growth by binding to endogenously produced IGF-II, thereby preventing IGF-II from interacting with the IGF-I receptor to stimulate cellular proliferation by an autocrine mechanism.

Insulin-like growth factors and cancer

Interest in insulin-like growth factors (IGFs) and their effect on carcinogenesis has increased recently because high serum concentrations of IGF1 are associated with an increased risk of breast, prostate, colorectal, and lung cancers. Physiologically, IGF1 is the major mediator of the effects of the growth hormone; it thus has a strong influence on cell proliferation and differentiation and is a potent inhibitor of apoptosis. The action of IGF1 is predominantly mediated through the IGF1 receptor (IGF1R). IGF1R is involved in several oncogenic transformation processes. The availability of unbound IGF1 for interaction with IGF1R is modulated by IGF-binding proteins (IGFBP1-6). IGFBPs, especially IGFBP3, have independent effects on cell growth, for example, IGFBP3 has proapoptotic activities both dependent on and independent of p53.

IGF-1 in gynaecology and obstetrics: update 2002

Recent discoveries on endocrine, paracrine and autocrine involvement of insulin-like growth factor-1 (IGF-1) in the proliferation of many tissues raised the attention of its role in reproduction and in the growth of various cancers as well as of benign proliferations. The intention of this article is to focus on IGF-1 in the field of gynaecology. Perimenopausal women who exhibit high IGF-1 and low IGF binding protein (IGFBP) levels, like IGFBG-3, have an increased risk of developing breast cancer. A higher risk for cervical, ovarian and endometrial cancer is related to high IGF-1 levels in post- and premenopausal women. It has been shown that myomas, by far the most common benign uterine tumor in women, grow in the presence of IGF-1, in vitro as well as in vivo. Studies show that IGF-1 is involved in the differentiation of various reproductive tissues, like endometrium and ovarian tissues. Patients suffering from polycystic ovary syndrome (PCO) frequently show insulin resistance accompanied by an increase of IGF-1 in plasma. Plasma IGF-1 levels are higher in cases of severe endometriosis, however, in endometriosis and in PCO IGF levels locally in the endometrium are reduced, what might explain infertility. Recently, it was shown that IGF facilitates the implantation of the human embryo in the endometrium during IVF. Implantation is a paradox where different immune systems have to collaborate to make implantation and survival of the pregnancy possible. IGF seems to be the starter molecule so that the two epithelia can fuse. A disturbance can result in complications during pregnancy i.e. spontaneous miscarriage, preeclampsia as well as defects of the embryo. Therefore, IGF is a useful marker in successful pregnancy as well. A better mechanistic understanding of IGF-1 action on the cellular level not only provides more elegant mechanistic explanations for the scientist, but the practitioner might find it interesting to utilize its diagnostic potential as a marker for various diseases. The relation between systemic IGF levels and local tissue IGF-1 levels has not yet been determined for all conditions.

Mind-body effect: insulinlike growth factor-1; clinical depression; and breast, prostate, and other cancer risk-an unmeasured and masked mediator of potential significance?

A possible relation may exist between higher insulinlike growth factor (IGF)-1 levels and the risk of premenopausal breast, prostate, or other cancers from recent prospective and case-control studies. Separately, a large prospective study has shown a potential association between chronic depression and cancer risk, whereas other preliminary studies have suggested a link between increasing IGF levels with major depression. Other studies have found that certain standard cancer treatments reduce the effect and levels of IGF, and 1 small study has found that standard antidepressants may reduce IGF levels in some patients diagnosed with major depression. It is possible that IGF-1 (or other IGFs) may be a mediator between depression and cancer, because separately both have been implicated in the risk of various cancers. This hypothesis first and foremost relies on the unsettled notion that an actual relation already exists or may be found in the future. It requires more extensive investigation because several studies have not found an association between IGF or depression and cancer risk, and other limitations such as small sample sizes and other influential factors on IGF levels need to be elucidated. Whether or not a mind-body effect exists with cancer, as seems to be the case with other diseases, remains to be seen. Is depression a potential confounder of human studies that attempts to establish a relation between IGF and disease? All of the studies to date have attempted to at least determine the effect of a variety of factors on IGF levels-including age, sex, diet, family history, weight, smoking status-and then have adjusted their results accordingly. Depression has not been included in this list of potential factors that may need to be considered when analyzing IGF-1 data and cancer risks. The time seems ripe to at least define further the relation, if any, between IGF-1 and depression.

Short-term effects of anastrozole treatment on insulin-like growth factor system in postmenopausal advanced breast cancer patients

Insulin-like growth factors (IGFs) play a fundamental role in cancer development by acting in both an endocrinal and paracrinal manner, and hormone breast cancer treatments affect the IGF system by modifying circulating growth factor levels. We evaluated total IGF-1, IGF-2, IGF binding protein (IGFBP)-1 and IGFBP-3 in the blood of 34 postmenopausal advanced breast cancer patients (median age 63 years, range 41-85) treated with anastrozole, a non-steroidal structure aromatase inhibitor (NSS-AI). The plasma samples were obtained at baseline, and after 2, 4, 8 and 12 weeks of treatment. The IGFs were quantitated by means of sensitive radioimmunoassays (RIAs). IGF-1 significantly increased during anastrozole treatment (baseline versus 12 weeks, P=0.031), IGF-2 showed a trend towards an increase, and IGFBP-1 constantly but not significantly decreased; IGFBP-3 did not seem to be affected at all. The anastrozole-induced changes in IGFs and IGFBP-1 appeared to be different in the patients receiving a clinical benefit from those observed in non-responders. We have previously shown that letrozole (a different type of NSS-AI) modifies blood IGF-1 levels, and the results of this study of the biological effects of anastrozole on the components of the IGF system confirm our previous observations.

Regulation of insulin-like growth factor type I (IGF-I) receptor kinase activity by protein tyrosine phosphatase 1B (PTP-1B) and enhanced IGF-I-mediated suppression of apoptosis and motility in PTP-1B-deficient fibroblasts

The insulin-like growth factor type I (IGF-I) receptor (IGF-IR), activated by its ligands IGF-I and IGF-II, can initiate several signal transduction pathways that mediate suppression of apoptosis, proliferation, differentiation, and transformation. Here we investigated the regulation of IGF-IR activation and function by protein tyrosine phosphatase 1B (PTP-1B). Coexpression of PTP-1B with a beta-chain construct of the IGF-IR (betaWT) inhibited IGF-IR kinase activity in fission yeast Schizosaccharomyces pombe, in COS cells, and in IGF-IR-deficient fibroblasts. In both spontaneously immortalized and simian virus 40 T antigen-transformed embryonic fibroblast cell lines derived from PTP-1B knockout mice, IGF-I induced higher levels of IGF-IR autophosphorylation and kinase activity than were induced in PTP-1B-expressing control cells. PTP-1B-deficient cells exhibited enhanced IGF-I-mediated protection from apoptosis in response to serum withdrawal or etoposide killing, as well as enhanced plating efficiency and IGF-I-mediated motility. Reexpression of PTP-1B in spontaneously immortalized fibroblasts resulted in decreased IGF-IR and AKT activation, as well as decreased protection from apoptosis and decreased motility. These findings demonstrate that PTP-1B can regulate IGF-IR kinase activity and function and that loss of PTP-1B can enhance IGF-I-mediated cell survival, growth, and motility in transformed cells.

Molecular determinants for the tissue specificity of SERMs

Selective estrogen receptor modulators (SERMs) mimic estrogen action in certain tissues while opposing it in others. The therapeutic effectiveness of SERMs such as tamoxifen and raloxifene in breast cancer depends on their antiestrogenic activity. In the uterus, however, tamoxifen is estrogenic. Here, we show that both tamoxifen and raloxifene induce the recruitment of corepressors to target gene promoters in mammary cells. In endometrial cells, tamoxifen, but not raloxifene, acts like estrogen by stimulating the recruitment of coactivators to a subset of genes. The estrogen-like activity of tamoxifen in the uterus requires a high level of steroid receptor coactivator 1 (SRC-1) expression. Thus cell type- and promoter-specific differences in coregulator recruitment determine the cellular response to SERMs.

Food restriction inhibits the growth of intestinal polyps in multiple intestinal neoplasia mouse

The effect of food restriction (FR) on spontaneous intestinal carcinogenesis in multiple intestinal neoplasia (Min) mice was examined. Thirty male Min mice were allotted to ad libitum feeding control and 20% FR groups from six weeks of age until the end of the 13-week experimental period. Although the total number of visible intestinal polyps in the FR group was not significantly different from the control group value, a significant decrease in large-sized polyps (>2 mm) and an increase in small-sized polyps (< or =2 mm) were observed in the distal small intestine. In this segment, the percentage of apoptotic cells counted in intestinal polyps in the FR group was significantly higher than in the control group, the percentage of proliferating cell nuclear antigen (PCNA)-positive cells not being significantly different. These results indicate that the FR may inhibit the growth of intestinal polyps in the Min mouse, and that apoptosis contributed in part to the inhibitory effect.

The insulin-like growth factor system as a therapeutic target in colorectal cancer

The purpose of this review is to examine recent evidence that investigates the role of the insulin-like growth factor (IGF) system in colorectal cancer. We concentrate on the evidence that makes the case for the investigation of strategies that might be used to disrupt the IGF system in prevention and treatment. Even though the weight of evidence suggests that components of the IGF system may be appropriate targets, there are a lack of studies that make a systematic characterisation of all the system components in human colorectal cancer. It is anticipated that this information, and the new therapeutic molecules which follow, will impact on the prevention and treatment of patients with this disease.

Insulin-like growth factor-1, insulin-like growth factor binding protein-3, and body mass index: clinical correlates of prostate volume among Black men

OBJECTIVES

To examine the relationship between insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), and body mass index and prostate volume, as a surrogate marker for benign prostatic hyperplasia, in a community-based sample of black men. Epidemiologic studies examining the role of IGF-1 and IGFBP-3 suggest that increased levels of serum IGF-1 and decreased levels of serum IGFBP-3 are associated with an increased risk of prostate cancer. Few studies have examined these factors with respect to benign prostatic hyperplasia, and these have been limited to white men.

METHODS

The study population consisted of a sample of 364 black men, 40 to 79 years of age, residing in Genesee County, Michigan. Men with prostate cancer or prior prostate surgery were excluded. All subjects completed a clinical examination, which included a complete urologic examination with transrectal ultrasonography, anthropometric measurements, and serum assays for IGF-1 and IGFBP-3.

RESULTS

Multivariable regression models demonstrated that prostate volume increased with increasing age (P <0.0001) and body mass index (P = 0.03). IGFBP-3 rather than IGF-1 was positively associated with increasing prostate volume (P = 0.003).

CONCLUSIONS

This is the largest study describing the relationships between IGF-1, IGFBP-3, and body mass index and prostate volume, and the only study in black men. Although earlier studies demonstrated an association between IGF-1 and prostate cancer risk, our findings indicate that IGFBP-3 is more relevant for prostate enlargement, suggesting that IGF-1 and IGFBP-3 may play different pathophysiologic roles in benign and malignant prostatic conditions.