Nutrition and breast cancer risk: can an effect via insulin resistance be demonstrated?

Unexploited Antineoplastic Effects of Commercially Available Anti-Diabetic Drugs

The development of efficacious antitumor compounds with minimal toxicity is a hot research topic. Numerous cancer cell targeted agents are evaluated daily in laboratories for their antitumorigenicity at the pre-clinical level, but the process of their introduction into the market is costly and time-consuming. More importantly, even if these new antitumor agents manage to gain approval, clinicians have no former experience with them. Accruing evidence supports the idea that several medications already used to treat pathologies other than cancer display pleiotropic effects, exhibiting multi-level anti-cancer activity and chemosensitizing properties. This review aims to present the anticancer properties of marketed drugs (i.e., metformin and pioglitazone) used for the management of diabetes mellitus (DM) type II. Mode of action, pre-clinical in vitro and in vivo or clinical data as well as clinical applicability are discussed here. Given the precious multi-year clinical experience with these non-antineoplastic drugs their repurposing in oncology is a challenging alternative that would aid towards the development of therapeutic schemes with less toxicity than those of conventional chemotherapeutic agents. More importantly, harnessing the antitumor function of these agents would save precious time from bench to bedside to aid the fight in the arena of cancer.

Physical activity and postmenopausal breast cancer: proposed biologic mechanisms and areas for future research

Convincing evidence now supports a probable preventive role for physical activity in postmenopausal breast cancer. The mechanisms by which long-term physical activity affect risk, however, remain unclear. The aims of this review were to propose a biological model whereby long-term physical activity lowers postmenopausal breast cancer risk and to highlight gaps in the epidemiologic literature. To address the second aim, we summarized epidemiologic literature on 10 proposed biomarkers, namely, body mass index (BMI), estrogens, androgens, sex hormone binding globulin, leptin, adiponectin, markers of insulin resistance, tumor necrosis factor-alpha, interleukin-6, and C-reactive protein, in relation to postmenopausal breast cancer risk and physical activity, respectively. Associations were deemed "convincing," "probable," "possible," or "hypothesized" using set criteria. Our proposed biological model illustrated the co-occurrence of overweight/obesity, insulin resistance, and chronic inflammation influencing cancer risk through interrelated mechanisms. The most convincing epidemiologic evidence supported associations between postmenopausal breast cancer risk and BMI, estrogens, and androgens, respectively. In relation to physical activity, associations were most convincing for BMI, estrone, insulin resistance, and C-reactive protein. Only BMI and estrone were convincingly (or probably) associated with both postmenopausal breast cancer risk and physical activity. There is a need for prospective cohort studies relating the proposed biomarkers to cancer risk and for long-term exercise randomized controlled trials comparing biomarker changes over time, specifically in postmenopausal women. Future etiologic studies should consider interactions among biomarkers, whereas exercise trials should explore exercise effects independently of weight loss, different exercise prescriptions, and effects on central adiposity.

Weight, height, body mass index and risk of breast cancer in postmenopausal women: a case-control study

Background

Many women in Iran have a relatively high body mass index. To investigate whether the condition contributes to excess breast cancer cases, a case-control study was conducted to assess the relationships between anthropometric variables and breast cancer risk in Tehran, Iran.

Methods

All incident cases of breast cancer in the Iranian Centre for Breast Cancer (ICBC) were identified through the case records. Eligible cases were all postmenopausal women with histological confirmed diagnosis of breast cancer during 1996 to year 2000. Controls were randomly selected postmenopausal women attending the ICBC for clinical breast examination during the same period. The body mass index (BMI) was calculated based on weights and heights as measured by the ICBC nursing staff. Both tests for trend and logistic regression analysis were performed to calculate odds ratios and 95% confidence intervals as measures of relative risk.

Results

In all, 116 breast cancer cases and 116 controls were studied. There were no significant differences between cases and control with regard to most independent variables studied. However, a significant difference was observed between cases and controls indicating that the mean BMI was higher in cases as compared to controls (P = 0.004). Performing logistic regression analysis while controlling for age, age at menopause, family history of breast cancer and parity, the results showed that women with a BMI in the obese range had a three fold increased risk of breast cancer [odds ratio (OR) = 3.21, 95% confidence interval (CI): 1.15–8.47].

Conclusion

The results suggest that obesity in postmenopausal women could increase risk of breast cancer and it merits further investigation in populations such as Iran where it seems that many women are short in height, and have a relatively high body mass index.

Obesity and prognosis of breast cancer

Obesity has a complicated relationship to both breast cancer risk and the clinical behaviour of the established disease. It is suggested that obesity is associated with both an increased risk of developing breast cancer risk and worse prognosis after disease onset. In post-menopausal women, various measures of obesity such as body mass index, weight, weight gain and waist : hip ratio have all been positively associated with risk of developing breast cancer. In most but not all case-control and prospective cohort studies, an inverse relationship has been found between weight and breast cancer among pre-menopausal women. Some data suggest that adult weight gain and central obesity increase the risk of pre-menopausal breast cancer. Obesity at the time of diagnosis is thought to be significant as a poor prognostic factor. Obesity is associated with adverse outcomes in both pre- and post-menopausal women with breast cancer. Many cancer survivors seek ways to minimize the risk of recurrence and death because of breast cancer. Despite complex and at times controversial data, enough evidence is available at present to suggest that weight management should be a part of the strategy to prevent the occurrence, recurrence and death because of breast cancer. In this review the effect of obesity on the prognosis of breast cancer is examined in detail.

Obesity as a risk factor for development and poor prognosis of breast cancer

The evidence that obesity adversely affects women's health is overwhelming and indisputable. The risk of postmenopausal breast cancer increases with obesity; measured as weight gain, body mass index, waist-hip ratio or percent body fat. It is also established that obesity is associated with poor prognosis of breast cancer. This review examines in detail the possible mechanisms by which obesity causes poor prognosis of breast cancer such as estrogenic activity, advanced or more aggressive disease at diagnosis and high likelihood of both local and systemic treatment failure. After careful consideration of the available evidence, the author concludes that obesity contributes towards development and poor prognosis of breast cancer; therefore, weight management should be an integral part of any strategy to prevent and improve the outcome of breast cancer.

Insulin and IGF-1 regulate the expression of the pituitary tumor transforming gene (PTTG) in breast tumor cells

The pituitary tumor transforming Gene (PTTG) is an oncogene that is highly expressed in most tumors analyzed to date. Here, we report the effects of insulin and the insulin like growth factor-1 (IGF-1) on the expression of PTTG. Using MCF-7 cells, a human breast cancer cell line, we observed that both insulin and IGF-1 upregulate the expression of PTTG mRNA by approximately 2.5-fold. Induction of PTTG mRNA expression by insulin or IGF-1 was completely blocked by the specific phosphatidylinositol (PI) 3 kinase inhibitor LY294002, but partially blocked by the MAP kinase inhibitor PD98059. Pretreatment of MCF-7 cells with actinomycin D completely blocked the stimulatory effect of insulin. Transfection of MCF-7 cells with a PTTG promoter-luciferase reporter construct revealed the dose-dependent stimulation of PTTG promoter activity by insulin, suggesting that the increase in PTTG expression by insulin is a result of activation of transcription of the PTTG gene. Taken together, our results suggest that insulin and IGF-1 regulate the expression of PTTG in MCF-7 cells primarily through the activation of PI3K/AKT cascade.

Gene 33 inhibits apoptosis of breast cancer cells and increases poly(ADP-ribose) polymerase expression

The structure of the Gene 33 protein suggests that it plays a role in intracellular signaling and Gene 33 is induced by many mitogenic and stressful stimuli. Previously, we found that Gene 33 expression is significantly induced by retinoic acid (RA), insulin and synergistically by both in a liver-derived cell line. In the present study, we investigated the basal expression and regulation of Gene 33 in multiple human breast cancer cell lines. These cell lines expressed different levels of Gene 33 protein, but Gene 33 protein was not regulated by RA or insulin, either alone, or in combination. However, epidermal growth factor (EGF) induced Gene 33 expression in SK-BR-3 cells and this induction was inhibited by co-treatment with RA. There was a strong correlation between endogenous basal Gene 33 expression and doubling time. Exogenous expression of Gene 33 in MCF-7 cells did not affect cell cycle distribution, but inhibited apoptosis and specifically increased the level of Poly(ADP-ribose) Polymerase (PARP-1) protein. This suggests that Gene 33 promotes breast cancer cell growth by an anti-apoptotic rather than a mitogenic effect, possibly involving up-regulation of PARP-1.

Altered metabolic profiles among older mothers with a history of preeclampsia

Preeclampsia has been linked to increased risk for cardiovascular disease and, more recently, to reduced risk for breast cancer later in life. The altered chronic disease risk associated with prior preeclampsia may reflect underlying metabolic differences. In this case-control study, we examined the metabolic profiles of older mothers with and without a history of preeclampsia in their first pregnancies. At the time of the study, subjects were non-pregnant, non-smoking women who completed their first pregnancies at age 30 or older, were pre-menopausal, and were free of serious chronic disease. Cases were 13 women who experienced preeclampsia in their first pregnancies; controls were 13 women with uncomplicated first pregnancies, frequency matched to cases on race/ethnicity, current age, and age at delivery. A fasting blood sample was collected from each subject during the luteal phase (day 19-22) of the menstrual cycle and assayed for specific factors thought to be linked to hypertensive disease or breast cancer. Compared to women with uncomplicated pregnancies, those with a history of preeclampsia had significantly elevated levels of fasting serum triglycerides, insulin and glucose, and a higher fasting insulin resistance index, suggesting that women with prior preeclampsia were relatively insulin resistant. In addition, cases had higher levels of insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) and a higher molar ratio of IGFBP-3 to IGF-1 than did controls. Adjustment for obesity and other potential confounders did not appreciably alter the magnitude of these associations. This preliminary study suggests that women with a history of preeclampsia have persistent metabolic abnormalities consistent with their observed excess risk for cardiovascular morbidity and mortality, and their apparent reduced risk for breast cancer later in life.

Improvement of metabolism among obese breast cancer survivors in differing weight loss regimens

OBJECTIVE

To compare the efficacy of different weight loss regimens on body weight loss and metabolic improvement in breast cancer survivors.

RESEARCH METHODS AND PROCEDURES

Forty-eight obese breast cancer survivors were randomly divided into four groups and were followed for 1 year: 1) the Control group (subjects did not receive specific nutrition counseling); 2) the Weight Watchers group (subjects were given free coupons to attend weekly Weight Watchers meetings); 3) the Individualized group (a registered dietitian provided one-on-one nutritional counseling); and 4) the Comprehensive group (subjects received individualized dietary counseling and free coupons for the weekly Weight Watchers meetings). At baseline and 3-, 6-, and 12-month data collection visits, a fasting blood sample was obtained for assays. A three-day dietary record was kept during the week before these visits and dietary intake was analyzed.

RESULTS

Subjects in the three intervention groups lost weight (Control: 1.1 +/- 1.7 kg; Weight Watchers: -2.7 +/- 2.1 kg; Individualized: -8.0 +/- 1.9 kg; Comprehensive: -9.5 +/- 2.7 kg) and percentage body fat, but only the Individualized and Comprehensive groups had significant losses. Subjects in the Comprehensive group showed the most improvement in cholesterol levels and had reductions in blood leptin levels.

DISCUSSION

Because insulin resistance and high blood leptin levels are associated with breast cancer, losing weight to improve these parameters may reduce the risk of recurrence. Only subjects in the Comprehensive group showed significant reductions in body weight and fat, energy intake, and leptin levels. For breast cancer survivors, different weight loss strategies should be considered to assist them in losing weight.

Insulin, Macronutrient Intake, and Physical Activity: Are Potential Indicators of Insulin Resistance Associated with Mortality from Breast Cancer?

High levels of insulin have been associated with increased risk of breast cancer, and poorer survival after diagnosis. Data and sera were collected from 603 breast cancer patients, including information on diet and physical activity, medical history, family history, demographic, and reproductive risk factors. These data were analyzed to test the hypothesis that excess insulin and related factors are directly related to mortality after a diagnosis of breast cancer. The cohort was recruited from breast cancer patients treated at the British Columbia Cancer Agency between July 1991 and December 1992. Questionnaire and medical record data were collected at enrolment and outcomes were ascertained by linkage to the BC Cancer Registry after 10 years of follow-up. The primary outcome of interest was breast cancer-specific mortality (n = 112). Lifestyle data were analyzed using Cox proportional hazards regression models to relate risk factors to outcomes, controlling for potential confounders, such as age and stage at diagnosis. Data for biological variables were analyzed as a nested case-control study due to limited serum volumes, with at least one survivor from the same cohort as a control for each breast cancer death, matched on stage and length of follow-up. High levels of insulin were associated with poorer survival for postmenopausal women [odds ratio, 1.9; 95% confidence interval (CI), 0.7-6.6, comparing highest to lowest tertile, P trend = 0.10], while high dietary fat intake was associated with poorer survival for premenopausal women (relative risk, 4.8; 95% CI, 1.3-18.1, comparing highest to lowest quartile). Higher dietary protein intake was associated with better survival for all women (relative risk, 0.4; 95% CI, 0.2-0.8, comparing highest to lowest quartile).

Obesity and breast cancer: a review of the literature

A woman's build, the risk of breast cancer and its subsequent prognosis seem to be related. In most but not all case-control and prospective cohort studies, an inverse relationship has been found between weight and breast cancer among premenopausal women. However, most large epidemiological studies have found that overweight or obese women are at increased risk of developing postmenopausal breast cancer. It is suggested that higher body mass index is associated with a more advanced stage of breast cancer at diagnosis in terms of tumour size but data on lymph node status is not so consistent. All treatment modalities for breast cancer such as surgery, radiotherapy, chemotherapy and hormonal treatment may be adversely affected by the presence of obesity. The overall and disease-free survival is worse in most but not all studies of prognosis of obese pre- and postmenopausal women with breast cancer.

Weight Change and the Risk of Late-Onset Breast Cancer in the Original Framingham Cohort

OBJECTIVE

Adult weight gain has been associated with a twofold risk of postmenopausal breast cancer. Data are limited regarding whether weight gain at specific periods of marked changes in estrogen- and insulin-related hormones have different risk associations. This study assesses the relation of adult weight change overall and at specific, hormonally relevant times with diagnosis of a first breast cancer after age 55 (late onset).

METHODS

Framingham study data were used to assess premenopausal (25-44 yr), perimenopausal (45-55 yr), postmenopausal (after 55 yr), and adult lifetime (from 25 yr) weight change in relation to late-onset breast cancer in 2,873 women followed for up to 48 yr, with 206 late-onset breast cancers.

RESULTS

Adult lifetime weight gain was associated with an increased risk of late-onset breast cancer (P trend = 0.046). Weight gain during specific time periods was not associated with breast cancer. Data suggested a possible decreased risk of breast cancer with weight loss from ages 25 to 44 and 45 to 55 yr (relative risk = 0.4 [0.2-1.2] and 0.5 [0.3-0.9], respectively).

CONCLUSION

These data confirm prior reports of an association between adult lifetime weight gain and increased risk of late-onset breast cancer and support current recommendations to avoid adult weight gain.

Insulin: a novel factor in carcinogenesis

Cancer is a leading cause of mortality in the United States. Despite much research on specific carcinogens, the cause of many cancers remains unclear. The identification of novel causative agents offers the potential for cancer prevention. Diseases such as obesity and diabetes mellitus, characterized by hyperinsulinemia, are associated with increased risk of endometrial, colorectal, and breast carcinomas. There is increasing evidence that insulin is a growth factor for tumor formation. The mechanisms underlying insulin-mediated neoplasia may include enhanced DNA synthesis with resultant tumor cell growth, inhibition of apoptosis, and altered sex hormone milieu. The reduced insulin levels seen with physical activity, weight loss, and a high fiber diet may account for decreased cancer risk. The role of newer drugs that restore sensitivity to insulin, thereby reducing hyperinsulinemia, is an exciting potential area of cancer prevention. In this review, we discuss the potential role of insulin as a tumor growth factor.

Effect of insulin on cell cycle progression in MCF-7 breast cancer cells. Direct and potentiating influence

We recently demonstrated that in MCF-7 breast cancer cells, insulin promoted the phosphorylation and activation of geranylgeranyltransferase I (GGTI-I), increased the amounts of geranylgeranylated Rho-A and potentiated the transactivating activity of lysophosphatidic acid (LPA) (Chappell, J., Golovchenko, I., Wall, K., Stjernholm, R., Leitner, J., Goalstone, M., and Draznin, B. (2000) J. Biol. Chem. 275, 31792-31797). In the present study, we explored the mechanism of this potentiating effect of insulin on LPA. Insulin (10 nm) potentiated the ability of LPA to stimulate cell cycle progression and DNA synthesis in MCF-7 cells. The potentiating effect of insulin appears to involve increases in the expression of cyclin E and decreases in the expression of the cyclin-dependent kinase inhibitor p27Kip1. All potentiating effects of insulin were inhibited in the presence of an inhibitor of GGTase I, GGTI-286 (3 microm) or by an expression of a dominant negative mutant of Rho-A. In contrast to its potentiating action, a direct mitogenic effect of insulin in MCF-7 cells involves activation of phosphatidylinositol 3-kinase and increased expression of cyclin D1. We conclude that the ability of insulin to increase the cellular amounts of geranylgeranylated Rho-A results in potentiation of the LPA effect on cyclin E expression and degradation of p27Kip1 and cell cycle progression in MCF-7 breast cancer cells.

Biomarkers in disease and health

Biomarkers have considerable potential in aiding the understanding of the relationship between diet and disease or health. However, to assess the role, relevance and importance of biomarkers on a case by case basis it is essential to understand and prioritise the principal diet and health issues. In the majority of cases, dietary compounds are only weakly biologically active in the short term, have multiple targets and can be both beneficial and deleterious. This poses particular problems in determining the net effect of types of foods on health. In principle, a biomarker should be able to contribute to this debate by allowing the measurement of exposure and by acting as an indicator either of a deleterious or of an enhanced health effect prior to the final outcome. In this review, the examples chosen - cancer (stomach, colon/rectal, breast); coronary heart disease and osteoporosis - reflect three major diet-related disease issues. In each case the onset of the disease has a genetic determinant which may be exacerbated or delayed by diet. Perhaps the most important factor is that in each case the disease, once manifest, is difficult to influence in a positive way by diet alone. This then suggests that the emphasis for biomarker studies should focus on predictive biomarkers which can be used to help in the development of dietary strategies which will minimise the risk and be of greater benefit.

Risk of breast cancer in relation to anthropometry, blood pressure, blood lipids and glucose metabolism: a prospective study within the Malmö Preventive Project

Insulin resistance may be a risk factor for breast cancer, possibly through increased levels of oestrogens or insulin-like growth factor I. Insulin resistance has been associated with obesity, hypertension, dyslipidaemia and impaired glucose tolerance. We studied the relation of these factors to breast cancer risk in a prospective cohort study of 9738 women. Menopausal status was defined a priori, and 112 cases of invasive breast carcinoma occurred in women who were premenopausal at baseline and 157 cases in subjects who were peri/postmenopausal. Relative risks (RR) for breast cancer were calculated by Cox's proportional hazards analysis for different quartiles of height, weight, body mass index, blood pressure, pulse rate and serum levels of total cholesterol, triglycerides, fasting blood glucose and glucose at 120 min after an oral dose of glucose. Peri/postmenopausal women had a significantly increased age-adjusted relative risk of breast cancer associated with height (RR = 1.78 for the highest versus lowest quartile), and the RR was increased over quartiles of cholesterol levels (P-value for trend: 0.05). No other significant associations were found. Adjustments for potential confounding factors or restriction of the analysis to cases and person-years before 55 years of age (premenopausal women), or after 55 years (peri/postmenopausal women), did not change

Susceptibility of lean and obese Zucker rats to tumorigenesis induced by N-methyl-N-nitrosourea

To address the possible involvement of hyperinsulinemia in breast cancer development, we have examined the susceptibility of lean and obese Zucker rats to N-methyl-N-nitrosourea (MNU)-induced mammary cancer. Fifty-day-old female lean or obese Zucker rats received intraperitoneal (i.p.) injections of 37.5 or 20 mg/kg MNU, respectively. We showed in separate experiments that these doses produce similar levels of DNA methylation in the mammary epithelial cells of the lean and obese animals. Over the course of 29 weeks following MNU treatment, half of the lean rats developed carcinomas of the mammary gland, demonstrating that they are of intermediate susceptibility to mammary tumorigenesis. During this period, the obese rats developed hyperinsulinemia and insulin resistance as expected. Although palpable tumors developed at a similar rate in the lean and obese rats, only 10% of the obese animals developed mammary carcinomas. The obese rats, however, developed a high incidence (63.3%) of epidermal cysts that occurred mainly in the region of the mammary glands. A 13.3% incidence of colon carcinomas was also found in the obese rats. These results suggest that the development of hyperinsulinemia does not render the obese Zucker rats more susceptible to mammary gland carcinogenesis. Our observation of colon carcinomas in obese, but not lean rats, however, is consistent with evidence that hyperinsulinemia promotes colon cancer in rodents and humans.

Diabetes mellitus and cancer

Although an association between diabetes and cancer was found over 100 years ago, the issue underwent different interpretations over the subsequent decades, and only modern, prospective, epidemiological cohort and case-control studies conducted in several countries have provided reliable evidence of an increased cancer risk in diabetic patients, mainly in those with type 2 diabetes. This risk varies according to the tumor site: it is the greatest for primary liver cancer, moderately elevated for pancreatic cancer, and relatively low for colorectal, endometrial, breast, and renal cancers. The cause of the association is not clear and remains the subject of different hypotheses. The most frequently cited reason is the potential effect of insulin. Found in high concentrations, due to insulin resistance in most patients with type 2 diabetes, this hormone is believed to express a mitogenic effect. This hypothesis needs to be confirmed in appropriately programmed prospective studies, but it may already be helpful in choosing an adequate treatment for type 2 diabetes to achieve optimal metabolic control with a simultaneous reduction in hyperinsulinemia, such as diet, physical exercise, metformin, and acarbose.

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.

Obesity, weight change, fasting insulin, proinsulin, C-peptide, and insulin-like growth factor-1 levels in women with and without breast cancer: the Rancho Bernardo Study

Postmenopausal overweight women have an increased risk of breast cancer. The link between obesity and breast cancer could be mediated through hyperinsulinemia. Insulin and insulin-like growth factor-1 (IGF-1) stimulate mammary cell proliferation in vitro, and cell proliferation is directly linked to the risk of breast cancer. Our objective was to investigate the relationship between breast cancer and body composition, IGF-1, proinsulin, C-peptide, and fasting insulin. A case-control study was conducted of 438 community-dwelling women aged 53-90 years in 1992-1994 who had no history of cancer at the baseline visit in 1972-1974. Women were excluded who were using estrogen replacement therapy (ERT) or tamoxifen at the 1992-1994 visit, when IGF-1, proinsulin, fasting insulin, and C-peptide levels were measured. Prior ERT, alcohol and tobacco use, exercise, and reproductive history were recorded. Weight, height, and waist/hip ratio were measured. The 45 women with breast cancer had similar baseline body mass indices to the 393 women without breast cancer but had gained significantly more weight between the baseline visit in 1972-1974 and 1992-1994, (age-adjusted relative risk [RR] 1.05/kg, 95% confidence interval [CI] 1.01-1.09, p = 0.016). Proinsulin, fasting insulin, and C-peptide were each significantly positively correlated with both current weight and weight gain. However, levels of these hormones and IGF-1 did not differ significantly between women with and without breast cancer (all 95% CI within 0.996-1.004). Past ERT was significantly more common among women with breast cancer (p = 0.015), and duration of use was significantly longer (age-adjusted RR 1.13 per year of use, 95% CI 1.08-1.18, p = 0.000). The risk of breast cancer was significantly increased in women who had gained weight or used ERT. This increased risk was not associated with circulating levels of IGF-1, fasting insulin, proinsulin, or C-peptide.

Alcohol intake and late-stage promotion of breast cancer

Breast cancer risk in women rises with increasing alcohol intake and is widely assumed to be mediated by increased oestrogen concentrations. However, observations that mechanisms and risk are likely to differ between pre- and postmenopausal women suggest that the postmenopausal disease in particular, may involve a promoting role for concomitants of hyperinsulinaemia which is commonly associated with alcoholic cirrhosis of the liver. The MEDLINE database and ongoing studies were examined for clinical, epidemiological and laboratory data on; (a) alcohol-related increase in the incidence of breast cancer in relation to menopausal status, oestrogen concentrations and the oestrogen receptor (ER) status of the tumour; (b) activation of insulin-like growth factor 1 receptor (IGF1R) in mammary tissue by alcohol-related hyperinsulinaemia; (c) interaction between ER and IGF1R in breast cancer cell systems. Epidemiological association between alcohol intake and increased breast cancer risk is more clearly seen in postmenopausal than premenopausal women, and a significant risk is associated with intake of more than two drinks (over 30 g) daily over a period of years. Alcohol-related hyperinsulinaemia is reported to increase with increasing degrees of cirrhosis and damage to liver function. Laboratory evidence suggests that hyperinsulinaemia can stimulate expression of IGF1R in mammary tissue, and this protein is likely to have a crucial role in mitogenesis and transformation to an oestrogen-independent malignant phenotype. It is postulated that in women with a history of long-term intake of moderate quantities of alcohol, the concomitants of hyperinsulinaemia may help to stimulate progression in precancerous breast lesions in the years leading up to the menopause and may increase the risk of breast cancer manifesting after the menopause.

Risk of endometrial and breast cancer in patients with diabetes mellitus

Diabetes mellitus patients have metabolic and endocrine alterations that could contribute to an increased incidence of hormone-related cancers. We assessed the incidence of endometrial and breast cancer among 80,005 women and the incidence of breast cancer among 73,847 men (total of 153,852 patients) identified in the Swedish In-patient Register as having been hospitalized for diabetes mellitus in the period 1965-1983. These patients underwent follow-up through 1989 via the Swedish Cancer Register and other nation-wide Swedish registers. The outcome measures were standardized incidence ratios (SIR) based on age-, sex- and calendar period-specific incidence rates from the entire Swedish population. To minimise the effect of selection bias, we excluded from the calculation of incidence ratios the first year of observation and cases diagnosed incidentally at autopsy. Only first cancers were considered for the estimates. A total of 328 endometrial cancers (SIR = 1.8; 95% confidence interval [CI] = 1.6-2.0), 1,145 female breast cancers (SIR = 1.3; 95% CI = 1.2-1.4) and 13 male breast cancers (SIR = 2.0; 95% CI = 1.0-3.4) were observed. We conclude that compared with the general population, patients with diabetes mellitus have an increased incidence of endometrial and breast cancers.

Insulin injections promote the growth of aberrant crypt foci in the colon of rats

The main objective of the present study was to test the hypothesis that exogenous insulin would enhance colon carcinogenesis. Thirty-six female Fischer 344 rats were fed ad libitum a low-fat rodent chow and given a single azoxymethane injection (20 mg/kg); one week later, they were randomized into two groups. Control rats were given a subcutaneous saline injection, 5 days/wk, and experimental rats were given Ultralente bovine insulin (20 U/kg). The promoting effect of insulin injections was assessed by the multiplicity (number of crypts) of aberrant crypt foci after 100 days of treatment (72 injections). The rats given insulin ate more and were heavier than controls (215 +/- 11 vs. 182 +/- 7 g, p < 0.001). Insulin injections also increased the amount of abdominal fat, plasma triglycerides, and insulinemia and decreased blood glucose (all p < 0.05). The number of aberrant crypt foci was the same in both groups, but their multiplicity was significantly increased by the insulin injections (2.8 +/- 0.3 vs. 2.5 +/- 0.2 crypt/focus in controls, p = 0.007). In addition, the proportion of sialomucin-producing foci was higher in insulin-injected rats than in controls (p = 0.04). These data show that exogenous insulin can promote colon carcinogenesis in rats and suggest that life-style and diets leading to low blood insulin might protect humans against colorectal cancer.