Phenethyl isothiocyanate (PEITC) is a candidate anticancer compound found in certain cruciferous vegetables. In our tumor cell xenograft model, dietary administration of PEITC (100-150 mg/kg body ...weight/d) inhibited androgen-responsive LNCaP human prostate cancer cell tumor growth. We found that dietary treatment with PEITC significantly inhibited tumor platelet/endothelial cell adhesion molecule (PECAM-1/CD31) expression, a marker of angiogenesis. By contrast, we did not find the inhibitory effects of PEITC on tumor growth to be associated with alteration of specific markers for apoptosis, cell proliferation or androgen receptor-mediated pathways. Consistent with in vivo results, PEITC exerted little effects on cell proliferation, cell cycle and androgen-dependent pathways. Interestingly, PEITC significantly attenuated LNCaP cell plating efficiency that correlated with inhibition of integrin family proteins integrin β1, α2 and α6 mRNA expression. Thus, PEITC may be a dietary factor that inhibits androgen-responsive prostate tumor growth indirectly by selectively targeting factors involved in the tumor microenvironment.
Epidemiologic studies show a positive association between obesity and cancer risk. In addition to increased body adiposity and secretion of fat-derived hormones, obesity is also linked to insulin ...resistance, type 2 diabetes, and chronic inflammation. We used the fatless A-ZIP/F-1 transgenic mouse to dissociate the relative role of each of these underlying factors in the development of cancer. These mice are unique in that they do not have white fat but do develop type 2 diabetes. In two cancer models, the classic two-stage skin carcinogenesis protocol and the C3(1)/T-Ag transgenic mouse mammary tumor model, A-ZIP/F-1 mice displayed higher tumor incidence, tumor multiplicity, and decreased tumor latency than wild-type mice. We examined circulating levels of adipokines, growth factors, and cytokines. As expected, adipokines (i.e., leptin, adiponectin, and resistin) were undetectable or found at very low levels in the blood of fatless mice. However, insulin, insulin-like growth factor-I, growth hormone, vascular endothelial growth factor, and proinflammatory Th2 cytokines, such as interleukin (IL)-1beta, IL-4, and IL-6, were elevated in A-ZIP/F-1 mice. Additionally, we examined multiple phosphorylated proteins (i.e., protein kinase B/Akt and ErbB2/HER-2 kinase) associated with cancer development. Results show that many of these phosphorylated proteins were activated specifically in the A-ZIP/F-1 skin but not in the wild-type skin. These findings suggest that adipokines are not required for the promotion of tumor development and thus contradict the epidemiologic data linking obesity to carcinogenesis. We postulate that insulin resistance and inflammation are responsible for the positive correlation with cancer observed in A-ZIP/F-1 mice.
We evaluated the effects of diet on intestinal tumorigenesis in male Apc(Min) mice by comparing AIN-76A diet fed ad libitum (CON); calorie intake restricted by 40% of the CON (CR); diet high in olive ...oil and supplemented with freeze-dried fruit and vegetable extracts (OFV); and diet high in total fat (HF). Compared with CON, the frequency of intestinal polyps was reduced by 57% by CR (P < 0.001) and by 33% OFV diet (P = 0.04). Both effective interventions reduced total body weight, lean mass, and fat mass and increased daily urinary corticosterone output, but only CR reduced serum insulin-like growth factor I and leptin. We conclude that dietary interventions can partially offset genetic susceptibility to intestinal carcinogenesis.
Breast cancer is the most commonly diagnosed cancer among US women; there is therefore great interest in developing preventive and treatment strategies for this disease. Because breast cancer ...incidence is much lower in countries where women consume high levels of soy, bioactive compounds in this food source have been studied for their effects on breast cancer. Genistein, found at high levels in soybeans and soy foods, is a controversial candidate breast cancer preventive phytochemical whose effects on breast cells are complex. To understand more clearly the molecular mechanisms underlying the effects of genistein on breast cancer cells, we used a DNA oligo microarray approach to examine the global gene expression patterns in MCF-7 breast cancer cells at both physiologic (1 or 5 μM) and pharmacologic (25 μM) genistein concentrations. Microarray analyses were performed on MCF-7 cells after 48 h of either vehicle or 1, 5, or 25 μM genistein treatment. We found that genistein altered the expression of genes belonging to a wide range of pathways, including estrogen- and p53-mediated pathways. At 1 and 5 μM, genistein elicited an expression pattern suggestive of increased mitogenic activity, confirming the proliferative response to genistein observed in cultured MCF-7 cells, while at 25 μM genistein effected a pattern that likely contributes to increased apoptosis, decreased proliferation and decreased total cell number, also consistent with cell culture results. These findings provide evidence for a molecular signature of genistein’s effects in MCF-7 cells and lay the foundation for elucidating the mechanisms of genistein’s biological impact in breast cancer cells.
The prevalence of obesity, an established epidemiologic risk factor for many cancers, has risen steadily for the past several decades in the U.S. Particularly alarming are the increasing rates of ...obesity among children, portending continuing increases in the rates of obesity and obesity-related cancers for many years to come. Unfortunately, the mechanisms underlying the association between obesity and cancer are not well understood. In particular, the effects and mechanistic targets of interventions that modulate energy balance, such as reduced calorie diets and physical activity, on the carcinogenesis process have not been well characterized. The purpose of this review is to provide a strong foundation for future mechanistic-based research in this area by describing key animal and human studies of energy balance modulations involving diet, exercise, or pharmaceutical agents and by focusing on the interrelated pathways affected by alterations in energy balance. Particular attention in this review is placed on the components of the insulin/IGF-1/Akt pathway, which has emerged as a predominant target for disrupting the obesity-cancer link. Also discussed is the promise of global approaches, including genomics, proteomics, and metabolomics, for the elucidation of energy balance-responsive pathways. The ultimate goal of this work is to provide the missing mechanistic information necessary to identify targets for the prevention and control of cancers related to or caused by excess body weight.
Energy balance, including diet, weight, adiposity, and physical activity, is associated with carcinogenesis. Epidemiologic studies indicate that obesity and sedentary and/or active behavior are risk ...factors for breast cancer in postmenopausal women and survival in both premenopausal and postmenopausal breast cancer patients. Thus, understanding the influence of energy balance modulation on changes in gene expression patterns in the normal mammary gland is important for understanding mechanisms linking energy balance and breast cancer. In a 6-week-long study, female C57BL/6 mice (9-week-old) were randomized into four groups: (a) food consumed ad libitum (AL), (b) AL with access to running wheels (AL+EX), (c) 30% calorie restricted (CR), and (d) 30% CR with access to running wheels (CR+EX). CR mice received 70% of calories but 100% of all other nutrients compared with AL mice. Diet and exercise treatments, individually and combined, had significant effects on body composition and physical activity. Affymetrix oligomicroarrays were used to explore changes in gene expression patterns in total RNA samples from excised whole mammary glands. Contrasting AL versus CR resulted in 425 statistically significant expression changes, whereas AL versus AL+EX resulted in 45 changes, with only 3 changes included among the same genes, indicating that CR and EX differentially influence expression patterns in noncancerous mammary tissue. Differential expression was observed in genes related to breast cancer stem cells, the epithelial-mesenchymal transition, and the growth and survival of breast cancer cells. Thus, CR and EX seem to exert their effects on mammary carcinogenesis through distinct pathways.
Abstract Regular moderate exercise has been proposed to enhance immune function, but its effects on immunity and their consequences have not been well studied. Mice without (AL) or with access (AL + ...EX) to voluntary running wheels were vaccinated with a model antigen (ovalbumin (OVA)) via intranasal or subcutaneous routes to target the mucosal and systemic immune compartments, respectively. EX enhanced OVA-specific CD4+ T cell cytokine production and proliferation in all lymphoid organs examined without changes in cell distribution in any organ. These results suggest that coupling moderate exercise with vaccination may enhance vaccine efficacy for the prevention and/or therapy of numerous diseases.
Evidence has accumulated from laboratory-based animal experiments and population-based human epidemiological studies that lifestyle factors that affect energy balance, such as caloric intake, ...nutritional status, and exercise, act in concert with genetic susceptibility to influence cancer development and progression. The use of animal models with specific genetic alterations, in combination with lifestyle modifications that alter overall energy balance, has contributed to a greater understanding of the mechanistic changes occurring during carcinogenesis and to the identification of points of intervention. Studies in our laboratory focusing on the role of energy balance and genetic susceptibility in mice deficient in one (+/−) or both (−/−) alleles of the p53 tumor suppressor gene and mice with a mutant APC allele (APCMin) showed that calorie restriction decreases tumor burden, increases tumor latency, and decreases serum insulin-like growth factor (IGF)-1 and leptin levels. Data from our studies, combined with results from other animal and human studies, have established a role for IGF-1 in carcinogenesis. Studies using genetic models of cancer that have been interbred with mice with abnormal levels of IGF-1 will enable the examination of combined effects of energy balance and genetic alterations on the cancer process. Models that integrate lifestyle and genetic effects in a single system provide a physiologically intact system in which combination interventions and therapies for cancer prevention can be tested and validated, thus building a strong preclinical foundation that will inform the development of clinical trials and add perspective to epidemiological studies.
Leptin is an adipocyte-derived cytokine associated with obesity and inflammation recently shown to influence colon epithelial cell fate and colon inflammation. Thus, the purpose of this study is to ...investigate the influences of leptin exposure on the production of proinflammatory signals by a model of normal YAMC (Apc+/+) and preneoplastic IMCE (ApcMin/+) colon epithelial cells. Here, we characterize the production of specific CC and CXC chemokines by IMCE and YAMC cells using an antibody-based cytokine array. Further, since epithelial cells are hypothesized to be accessory to the inflammatory response, we assessed the ability of supernants from leptin-exposed colon epithelial cells to activate macrophage chemotaxis and nitric oxide production. Both YAMC and IMCE cells produced the following chemokines from the CC family; MCP-1, MIP-3α, TCA-3, CTACK and RANTES. These cell lines also produced the following CXC chemokines; MIP-2, CXCL18, KC and LIX. Conditioned media from leptin-treated YAMC and IMCE cells induced nitric oxide production by macrophages (P < 0.05). However, only conditioned media from leptin-treated IMCE cells induced macrophage chemotaxis (P < 0.05). These data imply that preneoplastic but not normal cells may selectively attract immune cells that promote their survival and transformation. Taken together with our previous data, we conclude that leptin promotes the proliferation of a model of preneoplastic cells (IMCE) and induces the production of chemokines which may activate macrophages and promote macrophage cell chemotaxis. These data provide a rational basis for leptin-induced cross-talk between preneoplastic epithelial cells and immune cells that may influence the promotional phase of carcinogenesis.
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