The Interactions of Obesity, Inflammation and Insulin Resistance in Breast Cancer.

Obese postmenopausal women have an increased breast cancer risk, the principal mechanism for which is elevated estrogen production by adipose tissue; also, regardless of menstrual status and tumor estrogen dependence, obesity is associated with biologically aggressive breast cancers. Type 2 diabetes has a complex relationship with breast cancer risk and outcome; coexisting obesity may be a major factor, but insulin itself induces adipose aromatase activity and estrogen production and also directly stimulates breast cancer cell growth and invasion. Adipose tissue inflammation occurs frequently in obesity and type 2 diabetes, and proinflammatory cytokines and prostaglandin E2 produced by cyclooxygenase-2 in the associated infiltrating macrophages also induce elevated aromatase expression. In animal models, the same proinflammatory mediators, and the chemokine monocyte chemoattractant protein-1, also stimulate tumor cell proliferation and invasion directly and promote tumor-related angiogenesis. We postulate that chronic adipose tissue inflammation, rather than body mass index-defined obesity per se, is associated with an increased risk of type 2 diabetes and postmenopausal estrogen-dependent breast cancer. Also, notably before the menopause, obesity and type 2 diabetes, or perhaps the associated inflammation, promote estrogen-independent, notably triple-negative, breast cancer development, invasion and metastasis by mechanisms that may involve macrophage-secreted cytokines, adipokines and insulin.

Breast cancer pathology, receptor status, and patterns of metastasis in a rural appalachian population.

Breast cancer patients in rural Appalachia have a high prevalence of obesity and poverty, together with more triple-negative phenotypes. We reviewed clinical records for tumor receptor status and time to distant metastasis. Body mass index, tumor size, grade, nodal status, and receptor status were related to metastatic patterns. For 687 patients, 13.8% developed metastases to bone (n = 42) or visceral sites (n = 53). Metastases to viscera occurred within five years, a latent period which was shorter than that for bone (P = 0.042). More women with visceral metastasis presented with grade 3 tumors compared with the bone and nonmetastatic groups (P = 0.0002). There were 135/574 women (23.5%) with triple-negative breast cancer, who presented with lymph node involvement and visceral metastases (68.2% versus 24.3%; P = 0.033). Triple-negative tumors that metastasized to visceral sites were larger (P = 0.007). Developing a visceral metastasis within 10 years was higher among women with triple-negative tumors. Across all breast cancer receptor subtypes, the probability of remaining distant metastasis-free was greater for brain and liver than for lung. The excess risk of metastatic spread to visceral organs in triple-negative breast cancers, even in the absence of positive nodes, was combined with the burden of larger and more advanced tumors.

Biochemical and molecular mechanisms for the association between obesity, chronic inflammation, and breast cancer.

Upper body obesity is a risk factor for postmenopausal breast cancer and is related to an aggressive tumor phenotype and a poor prognosis regardless of menopausal status. After the menopause, the major mechanism for the association with disease risk is elevated estrogen production by adipose tissue, due to a high level of aromatase activity: these hormone-dependent tumors express both estrogen and progesterone receptors. Other important biological factors of risk include leptin and adiponectin, adipokines with opposing endocrine and paracrine activities, and obesity-related hyperinsulinemia. Chronic inflammation of the breast adipose tissue, which occurs in some obese women and is indicated by the accumulation of macrophages around dead adipocytes ("crown-like structures"), rather than adiposity per se, may prove to be the pathological lesion responsible for both local aromatase induction, and enhanced invasiveness and metastatic capacity through biological mechanisms that involve leptin, tumor necrosis factor-α, and insulin. A causal association between obesity in premenopausal women and breast cell epithelial-mesenchymal transition, perhaps with the participation of the Wnt signaling pathway, and aggressive hormone-independent breast cancer is suggested by a number of experimental and clinical studies.

The obesity-inflammation-eicosanoid axis in breast cancer.

Inflammation of the adipose tissues occurs in association with obesity. This inflammatory process leads to the induction of cyclooxygenase-2 (COX-2) expression and a consequent elevation in prostaglandin (PG) production, which, together with proinflammatory cytokines, induce aromatase expression and estrogen synthesis. Infiltrating macrophages support the growth of breast epithelial cells and vascular endothelial cells by producing a milieu of cytokines and growth factors. This scenario creates a microenvironment favorable to breast cancer growth and invasion. The eicosanoids promote further development and growth of breast cancers indirectly by the induction of aromatase, particularly in estrogen positive breast cancers, or by direct stimulatory effect of PGE2 and lipoxygenase (LOX) products on the more aggressive, estrogen-independent tumors. Beyond this, the local production of estrogens and proinflammatory cytokines which occurs in association with breast adipose tissue inflammation, and consequent activation of the estrogen receptor and nuclear factor-κB, provides a mechanism by which breast cancers develop resistance to selective estrogen receptor modulation and aromatase inhibitor therapy. The obesity-inflammation-eicosanoid axis in breast cancer does offer a therapeutic target for the prevention of relapse in breast cancer by improving the efficacy of antiaromatase therapy using COX/LOX inhibitors; however, careful consideration of menopausal status and obesity in patients is warranted.

The cellular and molecular mechanisms by which insulin influences breast cancer risk and progression.

Epidemiological studies have related hyperinsulinemia and type 2 diabetes to an increased breast cancer risk, an aggressive and metastatic phenotype, and a poor prognosis. Furthermore, diabetic retinopathy arises from pathological angiogenesis, which is also essential for breast cancer growth and metastasis. Insulin stimulates the proliferation of some human breast cancer cell lines in vitro by mechanisms that use both the phosphatidylinositol-3 kinase and the mitogen-activated protein kinase/Akt signaling pathways; it is also a cell survival (anti-apoptotic) agent and enhances tumor cell migration and invasive capacity. Hyperinsulinemia affects breast cancer cells via the endocrine system, but experimental studies suggest the importance of paracrine mechanisms operating by the effects of insulin on the secretion of adipokines from tumor-associated adipose tissue. In such a system, one adipokine, leptin, has stimulatory paracrine effects on breast cancer cell proliferation and survival, while a second, adiponectin, is inhibitory. Leptin, vascular endothelial growth factor, another insulin-regulated adipokine, and insulin itself also stimulate angiogenesis. Insulin has complex interactions with estrogens: it induces adipose stromal cell aromatase and tumor cell sex steroid hormone receptor expression and suppresses sex hormone-binding globulin, which may enhance estrogen synthesis and bioactivity with consequent promotion of estrogen-dependent breast cancer. All these actions influence the later steps in breast cancer development but genetic studies are also revealing connections between gene abnormalities related to type 2 diabetes and the initiation stage of breast carcinogenesis. Understanding the various mechanisms by which insulin participates in breast cancer cell biology provides opportunities for novel approaches to treatment.

Type 2 diabetes and obesity metabolic interactions: common factors for breast cancer risk and novel approaches to prevention and therapy.

The objective was to review type 2 diabetes as a risk factor for breast cancer, its influence on tumor aggressiveness and prognosis, and the interactions with obesity. Consideration was given to the responsible biological mechanisms and how these relate to the potential of hypoglycemic agents, notably metformin, as breast cancer chemotherapeutic agents. Most epidemiological studies indicate that type 2 diabetes is a modest positive risk factor for postmenopausal, but not premenopausal, breast cancer; indeed before the menopause it may be associated with a reduced risk. This pattern of differing effects on risk according to menopausal status is well established in obesity; however, although most type 2 diabetics are obese, the relationship with postmenopausal breast cancer does not appear to be a function of the body mass index. We suggest that before menopause the protective effect of obesity may modify any adverse effects of the metabolic changes related to type 2 diabetes. Regardless of menopausal status, obesity is associated with breast cancers that exhibit aggressive biological characteristics at the time of diagnosis and have a poor prognosis; a similar relationship is emerging for type 2 diabetes. The two metabolic disorders share biological mechanisms for their associations with breast cancer, including a direct effect of insulin on breast cancer cell proliferation, increased extraglandular estrogen production and bioavailability, changes in the adipokines, notably adiponectin, and activation of the AMP-activated protein kinase pathway. These mechanistic considerations are consistent with metformin having high potential as a breast cancer chemopreventive and therapeutic agent.

Interaction between menopausal status and obesity in affecting breast cancer risk.

Obesity has a complex relationship to breast cancer risk that differs in premenopausal and postmenopausal women. Before the menopause, the level of adiposity is inversely related to risk, indicative of a protective effect, whereas in postmenopausal women, particularly the elderly, the association is a positive one, consistent with obesity being a risk factor. The importance of high estrogen production in adipose tissue, with consequent elevation of circulating biologically available estradiol, in the promotional effect of obesity on postmenopausal breast carcinogenesis is well established; the resulting tumors express both estrogen and progesterone receptors. The mechanism(s) for the protective effect in premenopausal women is less well understood, but the breast cancers that do develop in the presence of obesity are most often estrogen and progesterone receptor negative, consistent with the selection of non-estrogen-dependent tumor cells which are dependent on growth factors such as insulin, insulin-like growth factor-I and some adipokines. The influence of menopausal status on the relationships between adiposity and breast cancer appears to be modified within each category by age; the protective effect before the menopause may be limited to younger women (<35 years), and the adverse effect was found to apply specifically to older postmenopausal women. Although randomized trials of weight reduction for postmenopausal breast cancer prevention have not been performed, observational studies suggested that risk reduction does occur; in addition, other health benefits of weight control need to be considered regardless of menopausal status.

Influence of obesity on breast cancer receptor status and prognosis.

Pre-existing obesity and postoperative weight gain are related to a poor prognosis in breast cancer regardless of menopausal status. Delayed diagnosis may be one cause, but of more biological significance, especially in younger women, is the association of adiposity with estrogen receptor-negative tumors with a propensity for distant metastasis. After the menopause, the major mechanism for the relationship is the elevated estrogen synthesis by adipose tissue; these hormone-dependent tumors are estrogen receptor-positive. Insulin and some adipokines also stimulate breast cancer growth and metastasis, both directly and most probably by enhanced angiogenesis. Weight control is important, not only to target breast cancer progression, but also to reduce the risk of nonbreast cancer mortality risk associated with excess adiposity.

Angiogenesis, adipokines and breast cancer.

The prevalence of overweight and obesity is rapidly increasing world wide. Numerous epidemiological studies have shown that obesity is a risk factor for postmenopausal breast cancer and relapse. However, the biological factors that drive the growth and progression of these tumors and how obesity contributes to the tumor microenvironment are poorly understood. Tumor development and metastasis are dependent on the process of angiogenesis or the formation of new blood vessels. More importantly, a ready supply of adipose tissue-derived angiogenic adipokines, notably VEGF and leptin, and the production of inflammatory cytokines by infiltrating macrophages that occurs in adipose tissues with obesity, promotes the paracrine stimulation of vascular endothelial cell growth needed for adipogenesis, while maintaining a microenvironment that is favorable for breast tumorigenesis.

The influence of socioeconomic disparities on breast cancer tumor biology and prognosis: a review.

OBJECTIVE: Socioeconomic deprivation is associated with an increased risk of breast cancer mortality. This article summarizes the relationships between socioeconomic status (SES) and breast cancer in white European women compared with racial and ethnic groups in the United States. Furthermore, we examine the association between obesity and breast cancer within socioeconomic disparities. METHODS: Mortality rates were published by the American Cancer Society and the National Cancer Institute Surveillance, Epidemiology, and End Results Program. Obesity data were derived from the National Center for Health Statistics Behavioral Risk Factor Surveillance System. MEDLINE searches were performed using keywords, such as socioeconomic status, poverty, African American, Hispanic, race, and combined with related articles. RESULTS: Socioeconomic deprivation may be responsible for the increased risk of breast cancer mortality in African American and Hispanic patients, as they are more likely than white American patients to be diagnosed with advanced disease. Among white women, social deprivation is related to poor breast cancer prognosis, with increased prevalence rates of high-grade, estrogen receptor (ER)-negative tumors, similar to that of triple-negative breast cancers observed in African American and Hispanic women. Obesity is associated with advanced breast cancer at diagnosis, high tumor proliferation rates, and more triple-negative phenotypes, indicating that it may adversely contribute to prognosis. CONCLUSIONS: Most studies show an effect of SES on breast cancer incidence and prognosis. Research should focus on the influence of social deprivation on breast cancer characteristics, such as absence of ER expression, that occurs in African Americans and Hispanics and in white European women with a different genetic background.

Triple-negative breast cancer and obesity in a rural Appalachian population.

BACKGROUND: Our objective was to determine the clinicopathologic features of triple-negative (estrogen receptor, progesterone receptor, and human epidermal growth factor-2 receptor negative) breast cancer and their relationship to obesity in women drawn from a population with one of the highest obesity rates in the United States. METHODS: This retrospective study involved 620 White patients with invasive breast cancer in West Virginia. Hospital tumor registry, charts, and pathology records provided age at diagnosis, tumor histologic type, size, nodal status, and receptor status. Body mass index was calculated and a value of > or = 30 was considered indicative of obesity. RESULTS: Triple-negative tumors occurred in 117 (18.9%) of the 620 patients, most often in association with invasive ductal carcinomas. Patients with triple-negative tumors were younger than those with other receptor types, 44.5% and 26.7%, respectively, being diagnosed at age <50 years (P = 0.0004). The triple-negative tumors were larger (P = 0.0003), most notably in the younger women, but small tumors (<2.0 cm) were more often accompanied by lymph node metastases. Obesity was present in 49.6% of those with triple-negative tumors but in only 35.8% of those with non-triple-negative tumors (P = 0.0098). Lymph node metastases were more frequently associated with T(2) tumors in obese patients (P = 0.032) regardless of their receptor status. CONCLUSIONS: Triple-negative breast cancers within a White, socioeconomically deprived, population occurred in younger women, with later stage at diagnosis, and in association with obesity, which itself has been associated with a poor prognosis in breast cancer.

Adiposity, the metabolic syndrome, and breast cancer in African-American and white American women.

Breast cancer, the second most common cause of cancer-related deaths in American women, varies substantially in incidence and mortality according to race and ethnicity in the United States. Although the overall incidence of breast cancer among African-American (AA) women is lower than in white American women, this cancer is more common in young premenopausal AA women, and AA breast cancer patients of all ages are more likely to have advanced disease at diagnosis, higher risk of recurrence, and poorer overall prognosis. Epidemiological studies indicate that these differences may be attributable in part to variation in obesity and body fat distribution. Additionally, AA women more frequently exhibit breast cancer with an aggressive and metastatic phenotype that may also be attributable to the endocrine and metabolic changes associated with upper body obesity. These changes include both elevated estrogen and androgen bioactivity, hyperinsulinemia, and perturbations of the adipokines. Type 2 diabetes and the metabolic syndrome, which are more common in AA women, have also been associated with breast cancer risk. Moreover, each of the individual components of the syndrome has been associated with increased breast cancer risk, including low levels of the adipocytokine, adiponectin. This review explores the specific roles of obesity, body fat distribution (particularly visceral and sc adipose tissue), type 2 diabetes, metabolic syndrome, and adipocytokines in explaining the differential patterns of breast cancer risk and prognosis between AA and white American women.

Adipokines as endocrine, paracrine, and autocrine factors in breast cancer risk and progression.

Adipokines (leptin, adiponectin, and hepatocyte growth factor (HGF)) secreted from adipose tissue have come to be recognized for their contribution to the mechanisms by which obesity and related metabolic disorders influence breast cancer risk. In this review, we discuss the direct and indirect effects of these protein factors on the biological and clinical aspects of breast cancer biology, and emphasize their distinctive modes of action through endocrine-, paracrine-, and autocrine-mediated pathways. The stimulatory effects of leptin on breast cancer growth were considered to occur primarily via activation of the estrogen receptor; however, new evidence suggests that leptin may be acting on downstream cell signaling pathways in both estrogen-dependent and -independent cell types. Another secretory adipokine, HGF, may act largely not only to promote tumor cell invasion, but also to enhance tumor growth indirectly by stimulating angiogenesis. In contrast, adiponectin, an endogenous insulin sensitizer, exerts a direct growth-inhibitory effect on tumor cells by downregulating cell proliferation and upregulating apoptosis, and also inhibits tumor-related angiogenesis.

Obesity, adipokines, and prostate cancer in a prospective population-based study.

BACKGROUND: The purpose of this investigation was to examine the association of obesity and the adipokines leptin, adiponectin, and interleukin-6 (IL-6) with prostate cancer risk and aggressiveness. METHODS: One hundred twenty-five incident prostate cancer cases and 125 age-matched controls were sampled from among participants in the original San Antonio Center for Biomarkers of Risk of Prostate Cancer cohort study. The odds ratios (OR) of prostate cancer and high-grade disease (Gleason sum >7) associated with the WHO categories of body mass index (kg/m(2)) and with tertiles of serum concentrations of adiponectin, leptin, and IL-6 were estimated using multivariable conditional logistic regression models. RESULTS: Body mass index was not associated with either incident prostate cancer [obese versus normal; OR, 0.75; 95% confidence interval (95% CI), 0.38-1.48; P(trend) = 0.27] or high-grade versus low-grade disease (OR, 1.17; 95% CI, 0.39-3.52; P(trend) = 0.62). Moreover, none of the three adipokines was statistically significant associated with prostate cancer risk or high-grade disease, respectively: leptin (highest versus lowest tertile; OR, 0.77; 95% CI, 0.28-1.37; P(trend) = 0.57; OR, 1.20; 95% CI, 0.48-3.01; P(trend) = 0.85); adiponectin (OR, 0.87; 95% CI, 0.46-1.65; P(trend) = 0.24; OR, 1.93; 95% CI, 0.74-5.10; P(trend) = 0.85); IL-6 (OR, 0.84; 95% CI, 0.46-1.53; P(trend) = 0.98; OR, 0.84; 95% CI, 0.30-2.33; P(trend) = 0.17). CONCLUSIONS: Findings from this nested case-control study of men routinely screened for prostate cancer and who had a high prevalence of overweight and obesity do not provide evidence to support that prediagnostic obesity or factors elaborated by fat cells strongly influence prostate cancer risk or aggressiveness. However, due to the small sample population, a small or modest effect of obesity and adipokines on these outcomes cannot be excluded.

Obesity, adipokines, and prostate cancer (review).

Prostate cancer, the third most common cancer in men worldwide, varies substantially according to geographic region and race/ethnicity. Obesity and associated endocrine variation are foremost among the risk factors that may underlie these regional and ethnic differences. The association between obesity and prostate cancer incidence is complex and has yielded inconsistent results. Studies that have linked obesity with prostate cancer mortality, advanced stage disease, and higher grade Gleason score, however, have produced more consistent findings, indicating that obesity may not necessarily increase the risk of prostate cancer, but may promote it once established. Additionally, metabolic syndrome, which includes disturbed glucose metabolism and insulin bioactivity, may also be associated with prostate carcinogenesis. Adipokines, defined as biologically active polypeptides produced by adipose tissue, have been linked with a number of carcinogenic mechanisms, including angiogenesis, cell proliferation, metastasis, and alterations in sex-steroid hormone levels. A number of emerging studies have implicated the role of adipokines in prostate carcinogenesis. This review explores the specific roles of several adipokines as putative mediating factors between obesity and prostate cancer with particular attention to leptin, interleukin-6 (IL-6), heparin-binding epidermal growth factor-like growth factor (HB-EGF), vascular endothelial growth factor (VEGF) and adiponectin.

Breast cancer and obesity: an update.

Obesity has a complicated relationship to both breast cancer risk and the clinical behavior of the established disease. In postmenopausal women, particularly the elderly, various measures of obesity have been positively associated with risk. However, before menopause increased body weight is inversely related to breast cancer risk. In both premenopausal and postmenopausal breast cancer, the mechanisms by which body weight and obesity affect risk have been related to estrogenic activity. Obesity has also been related to advanced disease at diagnosis and with a poor prognosis in both premenopausal and postmenopausal breast cancer. Breast cancer in African-American women, considering its relationship to obesity, exhibits some important differences from those described in white women, although the high prevalence of obesity in African-American women may contribute to the relatively poor prognosis compared with white American women. Despite the emphasis on estrogens to explain the effects of obesity on breast cancer, other factors may prove to be equally or more important, particularly as they relate to expression of an aggressive tumor phenotype. Among these, this review serves to stress insulin, insulin-like growth factor-I, and leptin, and their relationship to angiogenesis, and transcriptional factors.

Adverse effects of obesity on breast cancer prognosis, and the biological actions of leptin (review).

Leptin is a hormone with multiple biological actions which is produced predominantly by adipose tissue; in humans, plasma levels correlate with total body fat, and particularly high concentrations occur in obese women. Several actions of leptin, including the stimulation of normal and tumor cell growth, migration and invasion, and enhancement of angiogenesis, suggest that this hormone can promote an aggressive breast cancer phenotype which can be estrogen-independent. This effect may involve activation of the transcription factor NFkappaB. Leptin can also induce aromatase activity, with the potential for the promotion of estrogen production from androstenedione in adipose tissue, and hence the stimulation of estrogen-dependent breast cancer progression. On this basis, we hypothesize that leptin, perhaps in association with insulin, the plasma concentrations of which correlate with those of leptin, has an important role in the known adverse effect of obesity on breast cancer.

Mammography screening and breast cancer biology in African American women--a review.

This review examines some of the key issues in early detection and breast cancer biology for African American (AA) women which contribute to their diagnoses at more advanced stages than white women, and poorer long-term prognoses. While screening mammography is considered an essential factor in eliminating these disparities, its optimal application for AAs is not fully understood. There is a paucity of information on the success with which mammography screening programs are maintained over time in the AA population, and on screening guidelines with regard to age of initiation and frequency. No randomized clinical trials targeting AA women have been reported. This type of information is critical since breast cancer in AA women occurs at younger ages, and frequently demonstrates aggressive tumor biology at diagnosis. Studies are required to determine the incidence of interval cancers in current screening programs, and the influence of the biological characteristics which are known to differ in the breast tumors of AA and white women. Recognition of molecular and cellular characteristics which identify the potential invasiveness of ductal carcinomas in situ is also required. These studies would assist in establishing the criteria for identifying the subpopulation of younger pre-menopausal AA women who would benefit from early initiation of screening. Finally, the epidemiology and biology of mammographic densities, a risk factor for breast cancer and, perhaps, markers of aggressive disease require further study in both AA and white women.

Cyclooxygenase-2 expression influences the growth of human large and small cell lung carcinoma lines in athymic mice: impact of an organoselenium compound on growth regulation.

Increased expression of cyclooxygenase-2 (COX-2) significantly enhances carcinogenesis and inflammatory reactions. Regulation of COX-2 overexpression may be a reasonable target for cancer chemoprevention. We have tested the hypothesis that levels of COX-2 expression determine the growth of human lung cancer cells in nude mice. Two cell lines, NCI-H460 (non-small cell lung cancer) and NCI-H69 (small cell lung cancer) were selected because the former expresses high levels of COX-2 protein and the latter has no detectable levels. We also examined the effects of 1,4-phenylenebis(methylene)selenocyanate (p-XSC), a highly effective chemopreventive organoselenium compound and known inhibitor of COX-2 expression, in vivo, on cell growth and COX-2 expression in vitro in the NCI-H460 cancer cell line. Cells were exposed to p-XSC at levels between 10 and 100 microM for six days and showed toxicity at approximately 50 microM. Pre-exposure of NCI-H460 to non-toxic levels of p-XSC suppressed COX-2 protein expression in a dose-dependent manner. At 40 microM, p-XSC suppressed phorbol myristate acetate (PMA)-induced COX-2 expression in NCI-H460 cells by more than 66%. In vivo studies in athymic mice showed a significant difference in tumor volume between cell lines. Pre-treatment of NCI-H460 cells with a non-toxic dose of p-XSC, prior to their injection into nude mice, significantly suppressed tumor growth when compared to untreated cells. Collectively, the outcome of our in vitro and in vivo studies supports the hypothesis that levels of COX-2 expression determine the extent of human lung tumor growth in athymic mice. Therefore, inhibition of COX-2 expression by agents such as p-XSC provides a strong rationale for the development of future clinical prevention trials.