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

Metabolic syndrome and breast cancer risk: a case-cohort study nested in a multicentre italian cohort

Background

Metabolic syndrome (defined as at least three among abdominal obesity, high blood triglycerides, low high-density lipoprotein cholesterol, high blood glucose, and high blood pressure) is emerging as a risk factor for breast cancer; however few studies – most confined to postmenopausal women – have investigated associations between breast cancer risk and metabolic syndrome. The purpose of this study was to examine the association between metabolic syndrome and its components, and risk of breast cancer in postmenopausal and premenopausal women.

Methods

We performed a case-cohort study on 22,494 women recruited in 1993-1998 to four Italian centres (Turin, Varese, Naples, Ragusa) of the European Prospective Investigation into Cancer and Nutrition (EPIC) and followed-up for up to 15 years. A random subcohort of 565 women was obtained and 593 breast cancer cases were diagnosed. Hazard ratios (HR) with 95% confidence intervals (CI), adjusted for potential confounders, were estimated by Prentice-weighted Cox proportional hazards models.

Results

Presence of metabolic syndrome was associated with significantly increased breast cancer risk in all women (HR 1.52, 95%CI 1.14-2.02). When the analyses were repeated separately for menopausal status, the association was limited to postmenopausal women (HR 1.80, 95%CI 1.22-2.65) and absent in premenopausal women (HR 0.71, 95%CI 0.43-1.16); P for interaction between metabolic syndrome and menopausal status was 0.001. Of metabolic syndrome components, only high blood glucose was significantly associated with increased breast cancer risk in all women (HR 1.47, 95%CI 1.13-1.91) and postmenopausal women (HR 1.89, 95%CI 1.29-2.77), but not premenopausal women (HR 0.80, 95%CI 0.52-1.22; P interaction=0.004).

Conclusions

These findings support previous data indicating that metabolic syndrome is an important risk factor for breast cancer in postmenopausal women, but not in premenopausal women, and suggest that prevention of metabolic syndrome through lifestyle changes could confer protection against breast cancer.

An exercise trial targeting African-American women with metabolic syndrome and at high risk for breast cancer: Rationale, design, and methods

BACKGROUND

Metabolic syndrome and obesity are known risk factors for breast cancers. Exercise interventions can potentially modify circulating biomarkers of breast cancer risk but evidence in African-Americans and women with metabolic syndrome is lacking.

METHODS/DESIGN

The Focused Intervention on Exercise to Reduce CancEr (FIERCE) trial is a prospective, 6-month, 3-arm, randomized controlled trial to examine the effect of exercise on obesity, metabolic syndrome components, and breast cancer biomarkers among African-American women at high risk of breast cancer. Two hundred-forty inactive women with metabolic syndrome and absolute risk of breast cancer ≥ 1.40 will be randomized to one of the three trial arms: 1) a supervised, facility-based exercise arm; 2) a home-based exercise arm; and 3) a control group that maintains physical activity levels through the course of the trial. Assessments will be conducted at baseline, 3 months, and 6 months. The primary outcome variables are anthropometric indicators of obesity, metabolic syndrome components, and inflammatory, insulin-pathway, and hormonal biomarkers of breast cancer risk.

DISCUSSION

The FIERCE trial will provide evidence on whether a short-term exercise intervention might be effective in reducing breast cancer risk among African-American women with comorbidities and high breast cancer risk--a group traditionally under-represented in non-therapeutic breast cancer trials.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02103140.

Consumption of sweet foods and mammographic breast density: a cross-sectional study

BACKGROUND

The increasing consumption of sugar worldwide seems to lead to several health problems, including some types of cancer. While some studies reported a positive association between sweet foods intake and breast cancer risk, little is known about their relation to mammographic density (MD), a strong breast cancer risk factor. This study examined the association of sweet foods and drinks intake with MD among 776 premenopausal and 779 postmenopausal women recruited at mammography.

METHODS

A food-frequency questionnaire was used to assess intake of sweet foods, sugar-sweetened beverages and spoonsful of sugar added. Percent and absolute breast density were estimated using a computer-assisted method. Multivariate generalized linear models were used to evaluate associations. All models were adjusted for potential confounders, including age and body mass index.

RESULTS

For increasing quartiles of sugar-sweetened beverages intake, adjusted-mean absolute density was respectively 32, 34, 32 and 36 cm2 among all women (P(trend) = 0.040) and 43, 46, 44 and 51 cm2 among premenopausal women (P(trend) = 0.007). For increasing quartiles of sweet foods intake, adjusted-mean percent density was respectively 16, 16, 17 and 19% among postmenopausal women (P(trend) = 0.036). No association was shown between intake of spoonsful of sugar added and MD.

CONCLUSION

Our results suggest that an increase in sweet foods or sugar-sweetened beverage intake is associated with higher MD.

Does mammographic density reflect the expression of breast cancer markers?

Mammographic density reflects variation in breast tissue composition as detected on mammogram. It is associated with a number of well-known breast cancer risk factors and itself is considered one of the strongest risk factors for breast cancer. If the expression of several proteins and genes within the breast tissue influences mammographic density in the same way as it influences breast cancer risk, then mammographic density might serve as an intermediate biomarker in future epidemiological studies on breast cancer. This has the potential to provide a quick means for predicting the effect of changes in the breast microenvironment on breast cancer risk without having to wait for an eventual development of breast cancer. In this review, the expression of several proteins and genes (growth factors, enzymes, proteoglycans and pro-inflammatory markers) within the breast tissue is shown to be associated with mammographic density. These proteins and genes are suspected to play a role in breast carcinogenesis. More studies assessing differential expression of proteins and genes in mammary epithelium and stroma and their association with mammographic density among premenopausal and postmenopausal women are required. Identification of proteins and genes influencing mammographic density may provide further insight on the molecular causes of breast cancer.

Insulin-like growth factor-I:vitronectin complex-induced changes in gene expression effect breast cell survival and migration

Recent studies have demonstrated that IGF-I associates with vitronectin (VN) through IGF-binding proteins (IGFBP), which in turn modulate IGF-stimulated biological functions such as cell proliferation, attachment, and migration. Because IGFs play important roles in transformation and progression of breast tumors, we aimed to describe the effects of IGF-I:IGFBP:VN complexes on breast cell function and to dissect mechanisms underlying these responses. In this study we demonstrate that substrate-bound IGF-I:IGFBP:VN complexes are potent stimulators of MCF-7 breast cell survival, which is mediated by a transient activation of ERK/MAPK and sustained activation of phosphoinositide 3-kinase/AKT pathways. Furthermore, use of pharmacological inhibitors of the MAPK and phosphoinositide 3-kinase pathways confirms that both pathways are involved in IGF-I:IGFBP:VN complex-mediated increased cell survival. Microarray analysis of cells stimulated to migrate in response to IGF-I:IGFBP:VN complexes identified differential expression of genes with previously reported roles in migration, invasion, and survival (Ephrin-B2, Sharp-2, Tissue-factor, Stratifin, PAI-1, IRS-1). These changes were not detected when the IGF-I analogue ([L(24)][A(31)]-IGF-I), which fails to bind to the IGF-I receptor, was substituted; confirming the IGF-I-dependent differential expression of genes associated with enhanced cell migration. Taken together, these studies have established that IGF-I:IGFBP:VN complexes enhance breast cell migration and survival, processes central to facilitating metastasis. This study highlights the interdependence of extracellular matrix and growth factor interactions in biological functions critical for metastasis and identifies potential novel therapeutic targets directed at preventing breast cancer progression.

Metabolic syndrome is an independent risk factor for breast cancer

OBJECTIVE

This study was aimed to assess the prevalence of metabolic syndrome in patients with breast cancer and the independent effect of metabolic syndrome on breast cancer risk.

METHODS

Eighty-one women aged 40-80 years with breast cancer and 81 controls of similar age were screened for metabolic syndrome prevalence and breast cancer risk factors, including age at diagnosis, age at menarche, reproductive status, live births, breastfeeding, family history of breast cancer, physical activity, cigarette smoking, body mass index, and metabolic syndrome parameters. Each variable was first assessed for baseline comparisons using the univariate model, and significant variables were then added to the multivariate conditional logistic regression model.

RESULTS

Prevalence of metabolic syndrome was 59.2% in breast cancer patients, and 37% in the control group (p < 0.005). A positive and independent association was observed between metabolic syndrome and breast cancer risk (odds ratio = 2.49; 95% confidence interval 1.17-5.30).

CONCLUSION

Metabolic syndrome is more prevalent in breast cancer patients and is an independent risk factor for breast cancer.

Association of diabetes with mammographic breast density and breast cancer in the Minnesota breast cancer family study

Data from the Minnesota Breast Cancer Family Study cohort (n=6,130 women) were used to examine the association of type II diabetes with mammographic percent density and incident breast cancer (BC). Exposures and outcomes were self-reported. The first set of analyses evaluated diabetes (DM) as a risk factor for breast cancer. A total of 403 women (6.6%) reported a diagnosis of type II diabetes and 333 women reported an incident breast cancer. Women who reported type II diabetes had an age-adjusted relative risk (RR) for breast cancer of 1.44 (95% CI 0.89-2.32) compared to those who did not. Adjustment for covariates strengthened the association (RR 1.61, 95% CI 0.98-2.62). Mammograms were retrieved on women over the age of 40 and percent density was estimated with a user-assisted thresholding program. Cross-sectional analyses revealed that mean levels of mammographic density were not statistically significantly different between diabetic and non-diabetic women. Results were similar within strata of menopausal status. Breast cancer cases with diabetes did not have a significantly higher percent density than cases without diabetes. Our findings suggest that breast cancer risk may be increased among women with type II diabetes, but that type II diabetes does not significantly influence mammographic breast density.

Insulin growth factor-I and epidermal growth factor receptors recruit distinct upstream signaling molecules to enhance AKT activation in mammary epithelial cells

IGF-I and epidermal growth factor (EGF) stimulate both normal mammary epithelial cell (MEC) growth and tumorigenesis. Whereas both growth factors increase DNA synthesis in MECs, how they evoke a greater response in combination when they activate similar signaling pathways remains unknown. In the present study, we investigated the signaling pathways by which these mitogens act in concert to increase DNA synthesis. Only EGF activated the MAPK pathway, and no further increase in MAPK activation was observed when both mitogens were added together. Both growth factors activated the phosphatidylinositol-3 kinase pathway, and simultaneous treatment enhanced phosphorylation of both AKT and its downstream target, p70S6K. The enhanced activation of AKT was observed at multiple time points (5 and 15 min) and growth factor concentrations (2.5-100 ng/ml). IGF-I activated AKT via insulin receptor substrate-1 and p85, the regulatory subunit of phosphatidylinositol-3 kinase. Treatment with EGF had no effect on insulin receptor substrate-1; however, it activated the EGF receptor, SHC, and c-Src. EGF treatment caused the association of SHC with Grb2 and Gab2 with phospho-SHC, phospho-Gab1, Grb2, and p85. Interestingly, inhibition of Src activation blocked the ability of EGF, but not IGF-I, to activate AKT. This corresponded with a decrease in phosphorylation of the EGF receptor and its association with phospho-SHC as well as downstream signaling. Unexpectedly, inhibition of Src increased basal MAPK activation. This is the first study to show that EGF and IGF-I use separate upstream components within a given MEC line to enhance AKT phosphorylation, contributing to increased DNA synthesis.

Insulin-Like Growth Factor-I, IGF-Binding Protein-3, and Mammographic Breast Density

Some studies have suggested that insulin-like growth factor (IGF) pathway is related to premenopausal breast density, one of the strongest known breast cancer risk factors. This study was designed specifically to test the hypothesis that higher levels of IGF-I and lower levels of IGF-binding protein (IGFBP)-3 are associated with high mammographic breast density among premenopausal but not among postmenopausal women. A total of 783 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Blood samples were collected at the time of mammography, and plasma IGF-I and IGFBP-3 levels were measured by ELISA. Mammographic breast density was estimated using a computer-assisted method. Spearman's partial correlation coefficients (r(s)) were used to evaluate the associations. Adjusted mean breast density was assessed by joint levels of IGF-I and IGFBP-3 using generalized linear models. Among premenopausal women, high levels of IGF-I and low levels of IGFBP-3 were independently correlated with high breast density (r(s) = 0.083; P = 0.021 and r(s) = -0.124; P = 0.0005, respectively). Correlation of IGF-I with breast density was stronger among women in the lowest tertile of IGFBP-3 than among those in the highest tertile of IGFBP-3 (r(s) = 0.138; P = 0.027 and r(s) = -0.039; P = 0.530, respectively). In contrast, the correlation of IGFBP-3 with breast density was stronger among women in the highest tertile of IGF-I than among those in the lowest tertile of IGF-I (r(s) = -0.150; P = 0.016 and r(s) = -0.008; P = 0.904, respectively). Women in the combined top tertile of IGF-I and bottom tertile of IGFBP-3 had higher mean breast density than those in the combined bottom tertile of IGF-I and top tertile of IGFBP-3 (53.8% versus 40.9%; P = 0.014). No significant association was observed among postmenopausal women. Our findings confirm that IGF-I and IGFBP-3 are associated with breast density among premenopausal women. They provide additional support for the idea that, among premenopausal women, these growth factors may affect breast cancer risk, at least in part, through their influence on breast tissue morphology as reflected on mammogram.