Effect of dietary fat on human breast cancer growth and lung metastasis in nude mice

Time-restricted feeding alters the efficiency of mammary tumor growth

Disruption of circadian rhythms has detrimental host consequences. Indeed, both clinical and foundational science demonstrate a clear relationship between disruption of circadian rhythms and cancer initiation and progression. Because timing of food intake can act as a zeitgeber (i.e., entrainment signal) for the circadian clock, and most individuals in the developed world have access to food at all times of the day in a "24/7" society, we sought to determine the effects of timing of food intake on mammary tumor growth. We hypothesized that restricting access to food to during the inactive phase would accelerate tumor growth. Adult female Balb/C mice received a unilateral orthotopic injection of murine mammary carcinoma 4T1 cells into the ninth inguinal mammary gland. Beginning on the day of tumor injection and continuing until the end of the experiment, mice were food restricted to their active phase (ZT12 (lights off)- ZT0 (lights on), inactive phase (ZT0 - ZT12), or had ad libitum access to food. Mice that were food restricted to their inactive phase displayed a significant increase in body mass on days 7 and 14 of tumor growth relative to active phase or ad libitum fed mice. Additionally, mice fed during their inactive phase demonstrated a 20% reduction in food consumption relative to mice fed during their active phase and a 17% reduction in food consumption relative to ab libitum fed mice. Tumor volume was not significantly different between groups. However, food restricting mice to their inactive phase increased mammary tumor growth efficiency (i.e., mg of tumor mass per gram of food intake) relative to mice fed during the active phase and approached significance (p = .06) relative to ad libitum fed mice. To determine a potential explanation for the increased tumor growth efficiency, we examined rhythms of activity and body temperature. Mice fed during the inactive phase displayed significantly disrupted daily activity and body temperature rhythms relative to both other feeding regimens. Together, these data demonstrate that improperly timed food intake can have detrimental consequences on mammary tumor growth likely via disrupted circadian rhythms.

Dietary Intake of N-3 and N-6 Polyunsaturated Fatty Acids and Risk of Cancer: Meta-Analysis of Data from 32 Studies

BACKGROUND

Large epidemiological studies have yielded conflicting results regarding the relationship between polyunsaturated fatty acids (PUFAs) and cancers. Here, we performed a meta-analysis to examine the link between dietary intake of n-3 and n-6 PUFAs and cancer risk.

MATERIALS AND METHODS

We performed a search on PubMed, EMBASE, and the Cochrane Library. Studies that reported adjusted relative risk (RR) estimates with 95% confidence intervals (CI) for the associations of interest were included.

RESULTS

Thirty-two studies involving 1,445,732 participants were included. Colorectal, breast and prostate cancer had been analyzed in our study. Specifically, for colorectal cancer, total n-3 PUFAs, marine n-3 PUFAs, α-linolenic acids (ALA) and n-6 PUFAs were not associated with the risk of it (RR 1.04, 95%CI 0.85-1.28; RR 0.99, 95%CI 0.89-1.09; RR 1.05, 95%CI 0.93-1.19; RR 1.02, 95%CI 0.94-1.11, respectively). For breast cancer, only marine n-3 PUFAs, but not total n-3 PUFAs, ALA, and n-6 PUFAs, was associated with a lower risk of it (RR 0.70, 95%CI 0.55-0.91). For prostate cancer, ALA and n-6 PUFAs also have no association with the risk of it.

CONCLUSIONS

Most subtypes of PUFAs are probably not related to cancers. However, additional high-quality trials are warranted to corroborate the findings of this meta-analysis.

Chemoprevention of Breast Cancer With Vitamins and Micronutrients: A Concise Review

Numerous dietary components and vitamins have been found to inhibit the molecular events and signalling pathways associated with various stages of breast cancer development. To identify the vitamins and dietary micronutrients that exert protective effects against breast cancer and define their mechanism of action, we performed a literature review of in vitro, animal and epidemiological studies and selected the in vitro and animal studies with robust molecular evidence and the epidemiological studies reporting statistically significant inverse associations for a breast cancer-specific protective effect. There is sufficient evidence from in vitro, animal and epidemiological human studies that certain vitamins, such as vitamin D3, folate, vitamin B6, and beta carotene as well as dietary micronutrients, such as curcumin, piperine, sulforaphane, indole-3-carbinol, quercetin, epigallocatechin gallate (EGCG) and omega-3 polyunsaturated fatty acids (PUFAs), display an antitumoral activity against breast cancer and have the potential to offer a natural strategy for breast cancer chemoprevention and reduce the risk of breast cancer recurrence. Therefore, a supplement that contains these micronutrients, using the safest form and dosage should be investigated in future breast cancer chemoprevention studies and as part of standard breast cancer therapy.

The peculiarities of cancer cell metabolism: A route to metastasization and a target for therapy

The last decade has witnessed the peculiarities of metabolic reprogramming in tumour onset and progression, and their relevance in cancer therapy. Also, it has been indicated that the metastatic process may depend on the metabolic rewiring and adaptation of cancer cells to the pressure of tumour microenvironment and limiting nutrient availability. The present review gatherers the existent knowledge on the influence of tumour microenvironment and metabolic routes driving metastasis. A focus will be given to glycolysis, fatty acid metabolism, glutaminolysis, and amino acid handling. In addition, the role of metabolic waste driving metastasization will be explored. Finally, we discuss the status of cancer treatment approaches targeting metabolism. This knowledge revision will highlight the critical metabolic targets in metastasis and the chemicals already used in preclinical studies and clinical trials, providing clues that would be further exploited in medicinal chemistry research.

Thermally Abused Frying Oil Potentiates Metastasis to Lung in a Murine Model of Late-Stage Breast Cancer

Deep-frying is a popular form of food preparation used globally and throughout in the United States. Each time dietary oils are heated to deep-frying temperatures, they undergo chemical alterations that result in a new matrix of lipid structures. These lipid products include triglyceride dimers, polymers, oxidized triglycerides, and cyclic monomers, which raises nutritional concerns about associations between these lipid products and heightened health risks. Reports of associations between thermally abused frying oil and deleterious health outcomes currently exist, yet there is little information concerning the effects of thermally abused frying oil consumption and the progression of breast cancer. This study used a late-stage breast cancer murine model and in vivo bioluminescent imaging to monitor progression of metastasis of 4T1 tumor cells in animals consuming fresh soybean oil (SBO) and a thermally abused frying oil (TAFO). Bioluminescent and histologic examinations demonstrated that TAFO consumption resulted in a marked increase of metastatic lung tumor formation compared to SBO consumption. Further, in animals consuming the TAFO treatment diet, metastatic tumors in the lung displayed a 1.4-fold increase in the Ki-67 marker of cellular proliferation and RNA-sequencing analysis of the hepatic tissue revealed a dietary-induced modulation of gene expression in the liver.

Omega-3 fatty acid DHA modulates p53, survivin, and microRNA-16-1 expression in KRAS-mutant colorectal cancer stem-like cells

Background

The presence of chemotherapy-resistant colorectal cancer stem cells (CCSCs) with KRAS mutation is thought to be one of the primary causes for treatment failure in colorectal cancer (CRC). P53, survivin, and microRNA-16-1 are challenging targets for anticancer drugs which are associated with chemoresistance in CRC. Yet, no p53-, survivin-, and microRNA-16-1-modulating drug with low toxicity but high efficacy against KRAS-mutant CCSCs have been approved for clinical application in CRC. Here, we investigated whether in vitro concentrations of DHA equal to human plasma levels, are able to modulate, Wt-p53, survivin, and microRNA-16-1 in CRC cells with stem cell-like properties.

Methods

Wt-p53/KRAS-mutant CRC cells (HCT-116) with stem cell-like properties were treated with 100-, 150- and 200-μM/L DHA, after which cell number, viability, growth inhibition, Wt-p53, survivin and microRNA-16-1 expression, caspase-3 activation and apoptotic-rate were evaluated by different cellular and molecular techniques.

Results

After 24-, 48-, and 72-h treatments with 100- to 200-μM/L DHA, growth inhibition- rates were measured to be 54.7% to 59.7%, 73.% to 75.8%, and 63.3% to 97.7%, respectively. Treatment for 48 h with indicated DHA concentrations decreased cell number and viability. In addition, we observed a decrease in both the transcript and protein levels of survivin followed by 1.3- to 1.7- and 1.1- to 4.7-fold increases in the Wt-p53 accumulation and caspase-3 activation levels respectively. Treatment with 100 and 150 μM/L DHA increased microRNA-16-1 expression levels by 1.3- to 1.7-fold and enhanced the microRNA-16-1/survivin mRNA, p53/survivin, and caspase-3/survivin protein ratios by 1.7- to 1.8-, 1.3- to 2.6-, and 1.3- to 2-fold increases respectively. A decrease in the number of live cells and an increase in the number of apoptotic cells were also observed with increasing DHA concentrations.

Conclusion

Wt-p53, survivin, and microRNA-16-1 appear to be promising molecular targets of DHA. Thus, DHA might represent an attractive anti-tumor agent directed against KRAS-mutant CCSCs.

Dietary energy restriction reduces high-fat diet-enhanced metastasis of Lewis lung carcinoma in mice

The objective of this study was to determine whether a reduction in energy intake ameliorated the high-fat diet-enhanced spontaneous metastasis of Lewis lung carcinoma in mice. Male C57BL/6 mice were fed the AIN93G diet, a high-fat diet or a high-fat diet with a 5% restriction of the intake. Energy restriction reduced body adiposity and body weight, but maintained growth similar to mice fed the AIN93G diet. The high-fat diet significantly increased the number and size (cross-sectional area and volume) of metastases formed in lungs. Restricted feeding reduced the number of metastases by 23%, metastatic cross-sectional area by 32% and volume by 45% compared to the high-fat diet. The high-fat diet elevated plasma concentrations of proinflammatory cytokines (monocyte chemotactic protein-1, plasminogen activator inhibitor-1, leptin), angiogenic factors (vascular endothelial growth factor, tissue inhibitor of metalloproteinase-1) and insulin. Restricted feeding significantly reduced the high-fat diet-induced elevations in plasma concentrations of proinflammatory cytokines, angiogenic factors and insulin. These results demonstrated that a reduction in diet intake by 5% reduced high-fat diet-enhanced metastasis, which may be associated with the mitigation of adiposity and down-regulation of cancer-promoting proinflammatory cytokines and angiogenic factors.

Obesity and Cancer: An Angiogenic and Inflammatory Link

With the current epidemic of obesity, a large number of patients diagnosed with cancer are overweight or obese. Importantly, this excess body weight is associated with tumor progression and poor prognosis. The mechanisms for this worse outcome, however, remain poorly understood. We review here the epidemiological evidence for the association between obesity and cancer, and discuss potential mechanisms focusing on angiogenesis and inflammation. In particular, we will discuss how the dysfunctional angiogenesis and inflammation occurring in adipose tissue in obesity may promote tumor progression, resistance to chemotherapy, and targeted therapies such as anti-angiogenic and immune therapies. Better understanding of how obesity fuels tumor progression and therapy resistance is essential to improve the current standard of care and the clinical outcome of cancer patients. To this end, we will discuss how an anti-diabetic drug such as metformin can overcome these adverse effects of obesity on the progression and treatment resistance of tumors.

Effects of a High-Fat or High-Sucrose Diet on Ultraviolet B Irradiation-Induced Carcinogenesis and Tumor Growth in Melanin-Possessing Hairless Mice

We herein compared the effects of the chronic feeding of high-fat (HF), high-sucrose (HS), and low-fat/low-sucrose (control) diets on carcinogenesis following chronic ultraviolet B (UVB) irradiation in hairless mice. UVB irradiation-induced carcinogenesis was more prominent in HF diet-fed group than in control diet- and HS diet-fed groups. The HS diet group, as well as the HF diet one, showed tumor development and growth, increased skin matrix metalloproteinase (MMP) and blood plasminogen activator inhibitor-1 (PAI-1) levels, and decreased blood leptin and adiponectin levels after long-term UVB irradiation. These changes were smaller in the HS diet group than in the HF diet group. In addition, no difference was noted in the above changes between the control and HS diet groups. The increase induced in adipose tissue weight by the HF diet was markedly reduced by UVB irradiation. This result suggests that the abundant availability of lipids in hypertrophic adipose tissue may be related to tumor incidence and growth through increases in blood PAI-1 and skin MMP-9 expression levels and decreases in blood adiponectin levels by UVB irradiation. In conclusion, HF diet-induced hypertrophic adipose tissue is an important cancer risk factor that promotes UV irradiation-induced carcinogenesis and tumor growth.

Treatment of LS174T colorectal cancer stem-like cells with n-3 PUFAs induces growth suppression through inhibition of survivin expression and induction of caspase-3 activation

PURPOSE

Colorectal cancer stem cells (CCSCs) are thought to contribute to tumor initiation, progression, metastasis, chemo-resistance and therapy failure. Therefore, assessment of the effectiveness of agents with anti-proliferative activities against CCSCs is warranted. Several studies have shown that different tumorigenic steps, ranging from initiation to metastasis, can be affected by n-3 polyunsaturated fatty acids (PUFAs). Here, we evaluated the effects of the PUFA components docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), alone or in combination, on LS174T cells that serve as a model for colorectal cancer initiating cells with stem cell-like properties.

METHODS

LS174T cells were treated with 50, 100 and 150 μM DHA and EPA, or equal mixtures of DHA/EPA (i.e., 25/25, 50/50 and 75/75 μM), after which cell number, viability, growth inhibition, survivin expression, caspase-3 activation and apoptotic rate were evaluated.

RESULTS

We found that treatment of LS174T cells with increasing PUFA concentrations significantly increased growth inhibition in a dose- and time-dependent manner. After a 72 h treatment with 150 μM DHA and EPA, or their combination (75/75 μM), growth rates were inhibited by 80.3 ± 5.5%, 79.3 ± 5% and 71.1 ± 1%, respectively, compared to untreated cells. We also found that treatment for 48 h with 100 μM DHA and EPA, or their combination (50/50 μM), resulted in 2.9-, 3- and 2.6-fold increases in caspase-3 activation, as well as 54, 62.4 and 100% decreases in survivin mRNA expression levels, respectively, compared to untreated cells. Low survivin mRNA levels combined with high caspase-3 activity levels were found to correlate with a higher growth inhibition in PUFA-treated cells. DHA appears to be a more potent growth inhibitor than EPA and the DHA/EPA combination. An increase in the number of apoptotic cells (early + late), ranging from 12.9 to 44.7%, was observed with increasing DHA doses.

CONCLUSION

From our data we conclude that PUFAs induce growth inhibition via targeting survivin expression in LS174T cells, which serve as a model for CCSCs.

In utero exposure of rats to high-fat diets perturbs gene expression profiles and cancer susceptibility of prepubertal mammary glands

Human studies suggest that high-fat diets (HFDs) increase the risk of breast cancer. The 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis rat model is commonly used to evaluate the effects of lifestyle factors such as HFD on mammary tumor risk. Past studies focused primarily on the effects of continuous maternal exposure on the risk of offspring at the end of puberty (PND50). We assessed the effects of prenatal HFD exposure on cancer susceptibility in prepubertal mammary glands and identified key gene networks associated with such disruption. During pregnancy, dams were fed AIN-93G-based diets with isocaloric high olive oil, butterfat or safflower oil. The control group received AIN-93G. Female offspring were treated with DMBA on PND21. However, a significant increase in tumor volume and a trend of shortened tumor latency were observed in rats with HFD exposure against the controls (P=.048 and P=.067, respectively). Large-volume tumors harbored carcinoma in situ. Transcriptome profiling identified 43 differentially expressed genes in the mammary glands of the HFBUTTER group as compared with control. Rapid hormone signaling was the most dysregulated pathway. The diet also induced aberrant expression of Dnmt3a, Mbd1 and Mbd3, consistent with potential epigenetic disruption. Collectively, these findings provide the first evidence supporting susceptibility of prepubertal mammary glands to DMBA-induced tumorigenesis that can be modulated by dietary fat that involves aberrant gene expression and likely epigenetic dysregulation.

Omega-3 and omega-6 fatty acid intakes and endometrial cancer risk in a population-based case-control study

PURPOSE

Animal and laboratory studies suggest that long-chain omega-3 (n-3) fatty acids, a type of polyunsaturated fat found in fatty fish, may protect against carcinogenesis, but human studies on dietary intake of polyunsaturated fats and fish with endometrial cancer risk show mixed results.

METHODS

We evaluated the associations between endometrial cancer risk and intake of fatty acids and fish in a population-based sample of 556 incident cancer cases and 533 age-matched controls using multivariate unconditional logistic regression methods.

RESULTS

Although total n-3 fatty acid intake was not associated with endometrial cancer risk, higher intakes of eicosapentaenoic (EPA 20:5) and docosahexaenoic (DHA 22:6) fatty acids were significantly associated with lower risks (OR = 0.57, 95 % CI: 0.39-0.84; OR = 0.64, 95 % CI: 0.44-0.94; respectively) comparing extreme quartiles. The ratio of n-3:n-6 fatty acids was inversely associated with risk only on a continuous scale (OR = 0.84, 95 % CI: 0.71-0.99), while total fish intake was not associated with risk. Fish oil supplement use was significantly associated with reduced risk of endometrial cancer: OR = 0.63 (95 % CI: 0.45-0.88).

CONCLUSIONS

Our results suggest that dietary intake of the long-chain polyunsaturated fatty acids EPA and DHA in foods and supplements may have protective associations against the development of endometrial cancer.

Inhibition of transforming growth factor-β-activated kinase-1 blocks cancer cell adhesion, invasion, and metastasis

BACKGROUND

Tumour cell metastasis involves cell adhesion and invasion, processes that depend on signal transduction, which can be influenced by the tumour microenvironment. N-6 polyunsaturated fatty acids, found both in the diet and in response to inflammatory responses, are important components of this microenvironment.

METHODS

We used short hairpin RNA (shRNA) knockdown of TGF-β-activated kinase-1 (TAK1) in human tumour cells to examine its involvement in fatty acid-stimulated cell adhesion and invasion in vitro. An in vivo model of metastasis was developed in which cells, stably expressing firefly luciferase and either a control shRNA or a TAK1-specific shRNA, were injected into the mammary fat pads of mice fed diets, rich in n-6 polyunsaturated fatty acids. Tumour growth and spontaneous metastasis were monitored with in vivo and in situ imaging of bioluminescence.

RESULTS

Arachidonic acid activated TAK1 and downstream kinases in MDA-MB-435 breast cancer cells and led to increased adhesion and invasion. Knockdown of TAK1 blocked this activation and inhibited both cell adhesion and invasion in vitro. Tumour growth at the site of injection was not affected by TAK1 knockdown, but both the incidence and extent of metastasis to the lung were significantly reduced in mice injected with TAK1 knockdown cells compared with mice carrying control tumour cells.

CONCLUSION

These data demonstrate the importance of TAK1 signalling in tumour metastasis in vivo and suggest an opportunity for antimetastatic therapies.

Dietary fat increases solid tumor growth and metastasis of 4T1 murine mammary carcinoma cells and mortality in obesity-resistant BALB/c mice

Introduction

High-fat diets (HFDs) are known to cause obesity and are associated with breast cancer progression and metastasis. Because obesity is associated with breast cancer progression, it is important to determine whether dietary fat per se stimulates breast cancer progression in the absence of obesity. This study investigated whether an HFD increases breast cancer growth and metastasis, as well as mortality, in obesity-resistant BALB/c mice.

Methods

The 4-week-old, female BALB/c mice were fed HFD (60% kcal fat) or control diet (CD, 10% kcal fat) for 16 weeks. Subsequently, 4T1 mammary carcinoma cells were injected into the inguinal mammary fat pads of mice fed continuously on their respective diets. Cell-cycle progression, angiogenesis, and immune cells in tumor tissues, proteases and adhesion molecules in the lungs, and serum cytokine levels were analyzed with immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assay (ELISA). In vitro studies were also conducted to evaluate the effects of cytokines on 4T1 cell viability, migration, and adhesion.

Results

Spleen and gonadal fat-pad weights, tumor weight, the number and volume of tumor nodules in the lung and liver, and tumor-associated mortality were increased in the HFD group, with only slight increases in energy intake and body weight. HF feeding increased macrophage infiltration into adipose tissues, the number of lipid vacuoles and the expression of cyclin-dependent kinase (CDK)2, cyclin D1, cyclin A, Ki67, CD31, CD45, and CD68 in the tumor tissues, and elevated serum levels of complement fragment 5a (C5a), interleukin (IL)-16, macrophage colony-stimulating factor (M-CSF), soluble intercellular adhesion molecule (sICAM)-1, tissue inhibitors of metalloproteinase (TIMP)-1, leptin, and triggering receptor expressed on myeloid cells (TREM)-1. Protein levels of the urokinase-type plasminogen activator, ICAM-1, and vascular cell adhesion molecule-1 were increased, but plasminogen activator inhibitor-1 levels were decreased in the lungs of the HFD group. In vitro assays using 4T1 cells showed that sICAM-1 increased viability; TREM-1, TIMP-1, M-CSF, and sICAM-1 increased migration; and C5a, sICAM-1, IL-16, M-CSF, TIMP-1, and TREM-1 increased adhesion.

Conclusions

Dietary fat increases mammary tumor growth and metastasis, thereby increasing mortality in obesity-resistant mice.

A Western-type diet accelerates tumor progression in an autochthonous mouse model of prostate cancer

Epidemiological studies have provided evidence suggesting an important role for diet and obesity in the development of cancer. Specifically, lipid nutrients of the diet have been identified as important regulators of tumor development and progression. In the present study, we have examined the role of dietary fat and cholesterol in the initiation and progression of prostate cancer using the well-characterized TRAMP mouse model. Consumption of a Western-type diet--that is, enriched in both fat and cholesterol--accelerated prostate tumor incidence and tumor burden compared to mice fed a control chow diet. Furthermore, we also show that this diet increased the extent and the histological grade of prostate tumors. These findings were confirmed by the presence of increased levels of protein markers of advanced tumors in prostates obtained from animals fed a Western-type diet compared to those obtained from control animals. Increased lung metastases in animals fed a Western-type diet were also observed. In addition, we found that with a Western diet, animals bearing tumors presented with reduced plasma cholesterol levels compared with animals fed a control diet. Finally, we show that tumors obtained from animals fed a Western-type diet displayed increased expression of the high-density lipoprotein receptor SR-BI and increased angiogenesis. Taken together, our data suggest that dietary fat and cholesterol play an important role in the development of prostate cancer.

Environmental control of invasiveness and metastatic dissemination of tumor cells: the role of tumor cell-host cell interactions

Recent advances in tumor biology led to the realization that, in order to understand the mechanisms involved in proliferation and invasion of tumor cells, an analysis of the complex interactions that tumor cells establish with host cells of tumor microenvironment is required. The bidirectional interactions between tumor cells and components of tumor microenvironment, in particular endothelial cells, cells of monocyte/macrophage lineage and fibroblasts/myofibroblasts, play a critical role in most of the events that characterize tumor progression and metastasis. Interactions between these "reactive" normal cells and the genetically altered tumor cells, by either cell-to-cell contacts or soluble mediators, control the most aspects of tumor formation and progression. This review addresses some of the experimental evidences documenting that tumor cells may influence host cells of their own microenvironment by triggering changes that facilitate their local as well as distant dissemination. Therefore, it focuses on macrophages and fibroblasts that, upon stimulation by tumor cells, change their state towards a tumor-promoting-like phenotype.

Chewing the fat on tumor cell metabolism

Tumor cells undergo a metabolic shift toward specific bioenergetic (glycolysis) and anabolic (protein and lipid synthesis) processes that promote rapid growth. Nomura et al. (2010) now demonstrate that an increase in monoacylglycerol lipase (MAGL) drives tumorigenesis through the lipolytic release and remodeling of free fatty acids.

Ribosome-inactivating proteins isolated from dietary bitter melon induce apoptosis and inhibit histone deacetylase-1 selectively in premalignant and malignant prostate cancer cells

Epidemiologic evidence suggests that a diet rich in fruits and vegetables is associated with a reduced risk of prostate cancer (PCa) development. Although several dietary compounds have been tested in preclinical PCa prevention models, no agents have been identified that either prevent the progression of premalignant lesions or treat advanced disease. Momordica charantia, known as bitter melon in English, is a plant that grows in tropical areas worldwide and is both eaten as a vegetable and used for medicinal purposes. We have isolated a protein, designated as MCP30, from bitter melon seeds. The purified fraction was verified by SDS-PAGE and mass spectrometry to contain only 2 highly related single chain Type I ribosome-inactivating proteins (RIPs), alpha-momorcharin and beta-momorcharin. MCP30 induces apoptosis in PIN and PCa cell lines in vitro and suppresses PC-3 growth in vivo with no effect on normal prostate cells. Mechanistically, MCP30 inhibits histone deacetylase-1 (HDAC-1) activity and promotes histone-3 and -4 protein acetylation. Treatment with MCP30 induces PTEN expression in a prostatic intraepithelial neoplasia (PIN) and PCa cell lines resulting in inhibition of Akt phosphorylation. In addition, MCP30 inhibits Wnt signaling activity through reduction of nuclear accumulation of beta-catenin and decreased levels of c-Myc and Cyclin-D1. Our data indicate that MCP30 selectively induces PIN and PCa apoptosis and inhibits HDAC-1 activity. These results suggest that Type I RIPs derived from plants are HDAC inhibitors that can be utilized in the prevention and treatment of prostate cancer.

Gene signaling pathways mediating the opposite effects of prepubertal low-fat and high-fat n-3 polyunsaturated fatty acid diets on mammary cancer risk

In rats, prepubertal exposure to low-fat diet containing n-3 polyunsaturated fatty acids (PUFA) reduces mammary cell proliferation, increases apoptosis, and lowers risk of mammary tumors in adulthood, whereas prepubertal high-fat n-3 PUFA exposure has opposite effects. To identify signaling pathways mediating these effects, we performed gene microarray analyses and determined protein levels of genes related to mammary epithelial cell proliferation. Nursing female rats and rat pups were fed low-fat (16% energy from fat) or high-fat (39% energy from fat) n-3 or n-6 PUFA diets between postnatal days 5 and 24. cDNA gene expression microarrays were used to identify global changes in the mammary glands of 50-day-old rats. Differences in gene expression were confirmed by real-time quantitative PCR, and immunohistochemistry was used to assess changes in the peroxisome proliferator-activated receptor gamma and cyclin D1 levels. DNA damage was determined by 8-hydroxy-2'-deoxyguanosine assay. Expressions of the antioxidant genes thioredoxin, heme oxygenase, NADP-dependent isocitrate dehydrogenase, and metallothionein III, as well as peroxisome proliferator-activated receptor gamma protein, were increased in the mammary glands of 50-day-old rats prepubertally fed the low-fat n-3 PUFA diet. Prepubertal exposure to the high-fat n-3 PUFA diet increased DNA damage and cyclin D1 protein and reduced expression of BRCA1 and cardiotrophin-1. Reduction in mammary tumorigenesis among rats prepubertally fed a low-fat n-3 PUFA diet was associated with an up-regulation of antioxidant genes, whereas the increase in mammary tumorigenesis in the high-fat n-3 PUFA fed rats was linked to up-regulation of genes that induce cell proliferation and down-regulation of genes that repair DNA damage and induce apoptosis.

Coherent anti-Stokes Raman scattering imaging of lipids in cancer metastasis

Background

Lipid-rich tumours have been associated with increased cancer metastasis and aggressive clinical behaviours. Nonetheless, pathologists cannot classify lipid-rich tumours as a clinically distinctive form of carcinoma due to a lack of mechanistic understanding on the roles of lipids in cancer development.

Methods

Coherent anti-Stokes Raman scattering (CARS) microscopy is employed to study cancer cell behaviours in excess lipid environments in vivo and in vitro. The impacts of a high fat diet on cancer development are evaluated in a Balb/c mice cancer model. Intravital flow cytometry and histology are employed to enumerate cancer cell escape to the bloodstream and metastasis to lung tissues, respectively. Cancer cell motility and tissue invasion capability are also evaluated in excess lipid environments.

Results

CARS imaging reveals intracellular lipid accumulation is induced by excess free fatty acids (FFAs). Excess FFAs incorporation onto cancer cell membrane induces membrane phase separation, reduces cell-cell contact, increases surface adhesion, and promotes tissue invasion. Increased plasma FFAs level and visceral adiposity are associated with early rise in circulating tumour cells and increased lung metastasis. Furthermore, CARS imaging reveals FFAs-induced lipid accumulation in primary, circulating, and metastasized cancer cells.

Conclusion

Lipid-rich tumours are linked to cancer metastasis through FFAs-induced physical perturbations on cancer cell membrane. Most importantly, the revelation of lipid-rich circulating tumour cells suggests possible development of CARS intravital flow cytometry for label-free detection of early-stage cancer metastasis.

Non-Linear Optical Imaging of Obesity-Related Health Risks: Review

This review highlights the recent applications of non-linear optical (NLO) microscopy to study obesity-related health risks. A strong emphasis is given to the applications of coherent anti-Stokes Raman scattering (CARS) microscopy where multiple non-linear optical imaging modalities including CARS, sum-frequency generation (SFG), and two-photon fluorescence are employed simultaneously on a single microscope platform. Specific examples on applications of NLO microscopy to study lipid-droplet biology, obesity-cancer relationship, atherosclerosis, and lipid-rich biological structures are discussed.

An enhanced apoptosis and a reduced angiogenesis are associated with the inhibition of lung colonisation in animals fed an n-3 polyunsaturated fatty acid-rich diet injected with a highly metastatic murine melanoma line

Both epidemiological and experimental studies indicate that dietary n-3 PUFA inhibit carcinogenesis and tumour growth. Metastatic diffusion has also been found to be affected in animals fed diets containing purified n-3 PUFA or fish oil. In the present study, we investigated whether the metastatic diffusion of a highly metastatic variant (F10-SR cells) isolated from the B16 melanoma F10 line was affected by feeding host animals a diet containing 5 % fish oil. In these animals, compared with those fed a diet containing 5 % maize oil, there was a reduced number of metastatic pulmonary colonies. The immunohistochemical analysis of appropriate markers revealed that the antimetastatic effect of dietary n-3 PUFA was not related to a reduction of proliferation, but rather to an enhanced apoptotic activity. The reduction of von Willebrand factor immunoreactivity found in pulmonary colonies of F10-SR cells grown in fish oil-fed animals indicates that a decrease of angiogenesis contributes to the antimetastatic effect of dietary n-3 PUFA. This conclusion stands in spite of the higher expression of vascular endothelial growth factor observed in pulmonary colonies grown in fish oil-fed animals.

Dietary fish oil associated with increased apoptosis and modulated expression of Bax and Bcl-2 during 7,12-dimethylbenz(alpha)anthracene-induced mammary carcinogenesis in rats

The present study investigated the chemopreventive effect of dietary fish oil (Maxepa), rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on induction of apoptosis in mammary carcinogenesis model. Mammary carcinogenesis was initiated by a single, tail vein injection of 7,12-dimethylbenz(alpha)anthracene (DMBA) (0.5mg/0.2ml corn oil/100g body weight) at 7 weeks of animal age. Ninety female Sprague-Dawley rats were divided into two parts: part one was used for histology and immunohistochemical study and part two for morphological analysis. Each part consists of three experimental groups having 15 animals, i.e., Group A (DMBA control), Group B (DMBA+fish oil) and Group C (DMBA+corn oil). Rats were fed either fish oil or corn oil (0.5ml/day/rat) by oral gavage, 2 weeks prior to DMBA injection. Treatment was continued 25 weeks, studying histopathology, expression of Bax and Bcl-2 proteins by immunohistochemistry and apoptosis by TUNEL assay and morphological study at 36 weeks. Results showed that the fish oil-treated group exhibited a substantial increase in Bax (p<0.05) immunolabelling and a reduction of Bcl-2 immunopositivity (p<0.05), and increased TUNEL-positive apoptotic cells (p<0.05); however, corn oil treatment did not show these beneficial effects toward mammary preneoplasia. We conclude that fish oil has the potential to play a significant role in limiting mammary tumourigenesis in vivo.

Genotype X diet interactions in mice predisposed to mammary cancer: II. Tumors and metastasis

High dietary fat intake and obesity may increase the risk of susceptibility to certain forms of cancer. To study the interactions of dietary fat, obesity, and metastatic mammary cancer, we created a population of F(2) mice cosegregating obesity QTL and the MMTV-PyMT transgene. We fed the F(2) mice either a very high-fat or a matched-control-fat diet, and we measured growth, body composition, age at mammary tumor onset, tumor number and severity, and formation of pulmonary metastases. SNP genotyping across the genome facilitated analyses of QTL and QTL x diet interaction effects. Here we describe effects of diet on mammary tumor and metastases phenotypes, mapping of tumor/metastasis modifier genes, and the interaction between dietary fat levels and effects of cancer modifiers. Results demonstrate that animals fed a high-fat diet are not only more likely to experience decreased mammary cancer latency but increased tumor growth and pulmonary metastases occurrence over an equivalent time. We identified 25 modifier loci for mammary cancer and pulmonary metastasis, likely representing 13 unique loci after accounting for pleiotropy, and novel QTL x diet interactions at a majority of these loci. These findings highlight the importance of accurately modeling not only the human cancer characteristics in mice but also the environmental exposures of human populations.

High-fat, high-sucrose, and high-cholesterol diets accelerate tumor growth and metastasis in tumor-bearing mice

Epidemiological studies indicate that the risk factors for the development of various cancers are closely associated with metabolic symptoms such as obesity, hyperlipidemia, and insulin resistance caused by the excess consumption of high-calorie diets. However, the mechanisms of tumor growth and metastasis caused by feeding a high-calorie diet have not been clarified yet in tumor-bearing mice. In this study, we examined the effects of a high-fat (HF), a high-sucrose (HS), a high-cholesterol (HC) or a low-fat/low-sucrose (LF/LS) diet on tumor growth and metastasis in tumor-bearing mice. Angiogenic factors such as plasma leptin and monocyte chemoattractant protein-1 (MCP-1) were increased after the implantation of tumors, whereas conversely, an antiangiogenic factor, adiponectin, was reduced after the implantation of tumors in mice fed the HF, the HS, or the HC diet compared to LF/LS diet. Furthermore, we found that vascular endothelial growth factor, hypoxia inducible factor-1alpha and MCP-1 expression levels in tumors of mice fed the HF, the HS, or the HC diet were increased compared to those of mice fed the LF/LS diet. These findings suggest that the acceleration of tumor growth and metastasis by feeding the 3 diets may be due to the increase of angiogenic factors and the reduction of antiangiogenic factors.

Dietary lipids and cancer

For many years, epidemiological studies continued to suggest that high fat diets are linked to an increased incidence of certain cancers. However, whether the oncogenic properties of fat are associated with their quantity rather than the quality has become debatable. Epidemiological studies have been suggesting that n-6 polyunsaturated fatty acids (n-6 PUFA) and saturated fats are more likely to increase the incidence of cancer, whereas monounsaturated fatty acids (MUFA) and n-3 polyunsaturated fatty acids (n-3 PUFA) are more likely to prevent or decrease the chance of carcinogenesis. A firm conclusion cannot be drawn yet because of insufficient research. This paper reviews the current knowledge of the effects of saturated fats, different types of unsaturated fats, and fat-soluble vitamins on the etiology of cancer.

ω-3 Polyunsaturated fatty acids and ionizing radiation: Combined cytotoxicity on human colorectal adenocarcinoma cells

OBJECTIVE

This study evaluated whether omega-3 polyunsaturated fatty acids (PUFAs) could enhance the radiosensitivity of three different human colorectal adenocarcinoma cell lines. To understand the underlying mechanisms, the effects of omega-3 PUFAs on the cell growth, survival, and apoptosis were evaluated alone or in combination with an antioxidant (vitamin E) and compared with the effects of omega-6 PUFAs.

METHODS

LS174T, CO112, and Caco-2 cell survival was assessed by clonogenic assay after a 3-d pretreatment with omega-3/omega-6 PUFAs and/or vitamin E before a single X-ray exposure to 4 Gy. Cell growth and viability were measured by double fluorescence-activated cell sorter analyses using propidium iodide and fluorescein isothiocyanate-conjugated annexin V. Student's t test or multivariable linear regression analyses were used for comparison.

RESULTS

Preincubation with 30 to 100 micromol/L of omega-3 PUFAs induced a dose-dependent additive decrease in cell survival after irradiation (P < 0.05). Evaluation of the underlying mechanisms indicated that omega-3 PUFAs mainly decreased the cell number via apoptosis induction. Moreover, formation of lipid peroxidation products and modulation of cyclooxygenase II activity seemed to be involved, because coincubation with 10 micromol/L vitamin E abolished the effect of 50 micromol/L of omega-3 PUFAs (P < 0.05), whereas omega-6 PUFAs could partly mimic omega-3 PUFA effects.

CONCLUSION

These observations suggest that omega-3 PUFAs may be potential candidates as nutritional adjuvants to enhance the efficacy of human colorectal cancer radiotherapy.

Hypothalamic integration of immune function and metabolism

The immune and neuroendocrine systems are closely involved in the regulation of metabolism at peripheral and central hypothalamic levels. In both physiological (meals) and pathological (infections, traumas and tumors) conditions immune cells are activated responding with the release of cytokines and other immune mediators (afferent signals). In the hypothalamus (central integration), cytokines influence metabolism by acting on nucleus involved in feeding and homeostasis regulation leading to the acute phase response (efferent signals) aimed to maintain the body integrity. Peripheral administration of cytokines, inoculation of tumor and induction of infection alter, by means of cytokine action, the normal pattern of food intake affecting meal size and meal number suggesting that cytokines acted differentially on specific hypothalamic neurons. The effect of cytokines-related cancer anorexia is also exerted peripherally. Increase plasma concentrations of insulin and free tryptophan and decrease gastric emptying and d-xylose absorption. In addition, in obesity an increase in interleukin (IL)-1 and IL-6 occurs in mesenteric fat tissue, which together with an increase in corticosterone, is associated with hyperglycemia, dyslipidemias and insulin resistance of obesity-related metabolic syndrome. These changes in circulating nutrients and hormones are sensed by hypothalamic neurons that influence food intake and metabolism. In anorectic tumor-bearing rats, we detected upregulation of IL-1beta and IL-1 receptor mRNA levels in the hypothalamus, a negative correlation between IL-1 concentration in cerebro-spinal fluid and food intake and high levels of hypothalamic serotonin, and these differences disappeared after tumor removal. Moreover, there is an interaction between serotonin and IL-1 in the development of cancer anorexia as well as an increase in hypothalamic dopamine and serotonin production. Immunohistochemical studies have shown a decrease in neuropeptide Y (NPY) and dopamine (DA) and an increase in serotonin concentration in tumor-bearing rats, in first- and second-order hypothalamic nuclei, while tumor resection reverted these changes and normalized food intake, suggesting negative regulation of NPY and DA systems by cytokines during anorexia, probably mediated by serotonin that appears to play a pivotal role in the regulation of food intake in cancer. Among the different forms of therapy, nutritional manipulation of diet in tumor-bearing state has been investigated. Supplementation of tumor bearing rats with omega-3 fatty acid vs. control diet delayed the appearance of tumor, reduced tumor-growth rate and volume, negated onset of anorexia, increased body weight, decreased cytokines production and increased expression of NPY and decreased alpha-melanocyte-stimulating hormone (alpha-MSH) in hypothalamic nuclei. These data suggest that omega-3 fatty acid suppressed pro-inflammatory cytokines production and improved food intake by normalizing hypothalamic food intake-related peptides and point to the possibility of a therapeutic use of these fatty acids. The sum of these data support the concept that immune cell-derived cytokines are closely related with the regulation of metabolism and have both central and peripheral actions, inducing anorexia via hypothalamic anorectic factors, including serotonin and dopamine, and inhibiting NPY leading to a reduction in food intake and body weight, emphasizing the interconnection of the immune and neuroendocrine systems in regulating metabolism during infectious process, cachexia and obesity.

Effects of omega-3 fatty acids on orexigenic and anorexigenic modulators at the onset of anorexia

In cancer anorexia, a decrease in food intake (FI) occurs concomitant with changes in orexigenic peptides such as neuropeptide Y (NPY) and anorexigenic peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) and anorexigenic neurotransmitter serotonin. omega-3 Fatty acid (omega-3FA) inhibits cytokine synthesis, and delays tumor appearance, tumor growth, and onset of anorexia in tumor-bearing rats. We hypothesize that, in cancer anorexia, omega-3FA is associated with quantitative reversal of hypothalamic NPY, alpha-MSH, and serotonin receptor (5-HT(1B)-receptor) enhancing FI. Fischer rats were divided into: MCA tumor bearing fed chow (TB-Chow) or omega-3FA diet (TB-omega-3FA) and controls: non-tumor bearing fed chow (NTB-Chow) or omega-3FA diet (NTB-omega-3FA). Rats were euthanized at anorexia and brains were removed for hypothalamic immunohistochemical study, using NPY, alpha-MSH, and 5-HT(1B)-receptor-specific antibodies and slides assessed by image analysis. Immunostaining specificity was controlled by omission of primary or secondary antibodies and pre-absorption test. At anorexia, FI decreased (P < 0.05) in TB-Chow but did not change in TB-omega-3FA rats. In TB-omega-3FA vs. TB-Chow, NPY immunoreactivity increased 38% in arcuate nucleus (ARC; P < 0.05), and 50% in magnocellular paraventricular nucleus (mPVN; P < 0.05). alpha-MSH decreased 64% in ARC and 29% in mPVN (P < 0.05). 5-HT(1B)-receptor immunoreactivity decreased 13% only in supraoptic nucleus (P < 0.05). No immunoreactivity was found in the control sections. omega-3FA modified hypothalamic peptides and 5-HT-(1B)-receptor immunoreactivity at anorexia, concomitant with an increase in FI, were probably mediated by omega-3FA inhibition of tumor-induced cytokines.

Dietary long-chain n-3 fatty acids for the prevention of cancer: a review of potential mechanisms

Increasing evidence from animal and in vitro studies indicates that n-3 fatty acids, especially the long-chain polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid, present in fatty fish and fish oils inhibit carcinogenesis. The epidemiologic data on the association between fish consumption, as a surrogate marker for n-3 fatty acid intake, and cancer risk are, however, somewhat less consistent. This review highlights current knowledge of the potential mechanisms of the anticarcinogenic actions of n-3 fatty acids. Moreover, a possible explanation of why some epidemiologic studies failed to find an association between n-3 fatty acid intake and cancer risk is provided. Several molecular mechanisms whereby n-3 fatty acids may modify the carcinogenic process have been proposed. These include suppression of arachidonic acid-derived eicosanoid biosynthesis; influences on transcription factor activity, gene expression, and signal transduction pathways; alteration of estrogen metabolism; increased or decreased production of free radicals and reactive oxygen species; and mechanisms involving insulin sensitivity and membrane fluidity. Further studies are needed to evaluate and verify these mechanisms in humans to gain more understanding of the effects of n-3 fatty acid intake on cancer risk.

Mevalonate promotes the growth of tumors derived from human cancer cells in vivo and stimulates proliferation in vitro with enhanced cyclin-dependent kinase-2 activity

Malignant cells are known to have elevated rates of mevalonate synthesis because of increased levels and catalytic efficiency of 3-hydroxy-3-methylglutaryl-CoA reductase. Whether this increased mevalonate synthesis occurs as a consequence of increased requirements for a mevalonate-derived metabolite in response to rapid growth or whether mevalonate promotes the growth of tumor cells is unknown. To address this question, we administered mevalonate via miniosmotic pumps to nude mice inoculated with MDA-MB-435 human cancer cells. After 13 weeks of growth, tumors in mevalonate-treated mice were significantly larger than tumors in saline-treated, control mice (1.52 +/- 0.26 g versus 0.81 +/- 0.27 g respectively, p < 0.05). The cancer cells treated in culture with mevalonate also demonstrated increased proliferation rates associated with accelerated entry of cells into S phase. These cells had enhanced total and cyclin A-immunoprecipitable cyclin-dependent kinase-2 (CDK-2) activity, increased activating phosphorylation of CDK-2, and decreased inhibitory binding of CDK-2 to p21(Cip1). Our findings demonstrate that mevalonate promotes tumor growth and suggest that an increase in mevalonate synthesis in extrahepatic tissues following cholesterol-lowering therapy may explain the elevated risk of cancer shown in some studies.

Effects of eicosatrienoic acid (20:3 n-9, Mead's acid) on some promalignant-related properties of three human cancer cell lines

The essential fatty acid deficiency (EFAD) is a metabolic condition related to cancer development. We studied the effect of eicosapentaenoic acid (EPA, 20:5 n-3) and eicosatrienoic acid (ETA, 20:3 n-9), an essential fatty acid (EFA) and non-EFA respectively, on tumour cells parameters linked to tumour progression and metastases. Human tumour cell lines (T-24 from urothelium, MCF-7 from breast and HRT-18 from colon) were used. EPA showed an anti-proliferative effect on the three lines. ETA showed the following effects: in T-24, the lipid peroxidation was decreased and E-cadherin was undetectable; in MCF-7, increased E-cadherin expression enhanced the lipid peroxidation and decreased cell proliferation; on HRT-18, the E-cadherin expression and lipid peroxidation diminished, whereas cell proliferation was increased. In conclusion, EFA (20:5 n-3) exhibited beneficial effects, whereas unusual ETA showed an opposite effect on some tumour parameters. The possible riskiness of EFA-deprivation, along with the potential of EFA as natural nutrapeutic products for human tumour prevention and treatment, makes EFA worthy of further consideration.

The embedded tumour: host physiology is important for the evaluation of tumour growth

The growth potential of a tumour can significantly depend on host features such as age, cell proliferation rates and caloric intake. Although this is widely known, existing mathematical models for tumour growth do not account for it. We therefore developed a new model for tumour growth, starting from a mathematical framework that describes the host's physiology. The resulting tumour-in-host model allowed us to study the implications of various specific interactions between the energetics of tumour and host. The model accounts for the influence of both age and feeding regimen of the host organism on the behaviour of a tumour. Concerning the effects of a tumour on its host, it explains why tumour-mediated body-weight loss is often more dramatic than expected from the energy demands of the tumour. We also show how the model can be applied to study enhanced body-weight loss in presence of cachectic factors. Our tumour-in-host model thus appears a proper tool to unite a wide range of phenomena in tumour–host interactions.

Dietary docosahexaenoic acid levels influence the outcome of arabinosylcytosine chemotherapy in L1210 leukemic mice

The purpose of this study was to investigate whether dietary supplementation with the n-3 fatty acid docosahexaenoic acid (DHA) in combination with arabinosylcytosine (AraC) chemotherapy could prolong the life expectancy of mice bearing L1210 leukemia. The four control diets included rodent chow, a diet containing 5% of a blended oil mimicking the fatty acid composition of rodent chow, and diets containing 5% or 10% fat with safflower oil as the main oil source. The two DHA-supplemented diets provided 1.5% or 3.5% DHA and 5% or 10% total fat, respectively. After tumor cell inoculation, mice were treated with AraC for 10 days. Mice fed the 5% safflower oil diet (30.1 -/+ 4.1 days), but not those fed the 10% safflower oil diet, survived longer than the chow-fed animals (22.1 -/+ 3.1 days, P = 0.05). The 1.5%-/+ DHA diet (average intake 1.8 g DHA/kg/day) was associated with a longer life span (33.3 -/+ 3.4 days, P < 0.01 vs. chow-fed) and no incidence of death due to drug toxicity. Further increasing DHA intake (4.5 g DHA/kg/day) resulted in shortened survival time (26.5 -/+ 2.0 days), increased circulating tumor cell burden, and lowered red blood cell concentrations. These data suggest that a modest level of dietary DHA or linoleic acid supplementation may improve the antineoplastic efficacy of AraC. However, overconsumption of DHA reverses the beneficial effect of DHA intake on drug sensitivity.

Effects of dietary fish oil on fatty acids and eicosanoids in metastasizing human breast cancer cells

We examined the relationships between the suppressive effects of dietary fish oil on growth and metastasis of MDA-MB-435 human breast cancer cells in female nude mice and the primary tumor phospholipid fatty acid concentrations, phospholipase A2 activity, and eicosanoid levels. Mice (n = 120) were fed a 23% (wt/wt) corn oil (CO) linoleic acid (LA)-rich diet for seven days before and after 10(6) tumor cells were injected into a mammary fat pad, and then the mice receive one of three isocaloric diets containing 23% total fat but different proportions of CO and menhaden oil (MO) (18% CO-5% MO, 11.5% CO-11.5% MO, 5% CO-18% MO) or a 23% fat diet containing 18% deodorized fish oil supplemented with tocopherol and tert-butylhydroquinone antioxidants (FAO). Primary tumor growth rate was significantly greater in mice fed the 18% CO diet than in the three diets containing higher levels of fish oil (all p < 0.05). The 18% MO diet, but not the 11.5% MO or the 18% FAO diet, suppressed the development of lung metastases compared with the 18% CO diet. Increasing the proportion of MO relative to CO in the diets produced corresponding increases in the primary tumor phospholipid eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations and reductions in LA and arachidonic acid. There was a significant positive correlation between the LA concentration in these tumors and the extent of lung metastasis (r = 0.504). Tumor phospholipase A2 activity was unaffected by dietary MO intake. Prostaglandin E2 concentration was inversely correlated with phospholipid EPA (r = -0.484) and DHA (r = -0.439), but there was no relationship with lung metastasis. Tumor leukotriene B4 and 5-hydroxyeicosatetraenoic acid levels were not reduced by dietary MO. The 18% FAO- and the 18% MO-fed mice showed similar relationships for the phospholipid fatty acids and prostaglandin E2, despite the lack of effect on metastasis. The strong correlation between phospholipid LA levels and metastasis and the lack of an association with tumor eicosanoids suggest that the 18% MO diet inhibited metastasis because dietary LA was replaced by other fatty acids.

No effect of a high-fat diet on promotion of sex hormone-induced prostate and mammary carcinogenesis in the Noble rat model

Results of international correlation and migrant studies suggest that dietary fat promotes carcinogenesis in hormone-sensitive sites, but this is disputed. In the present study, we used a Noble rat model of sex hormone-induced cancers to examine the effect of a high-fat diet on the incidence and latency of prostate and mammary cancer in male (n 139) and female (n 72) animals respectively. We also measured alpha-tocopherol levels in female breast tissue to determine whether a high intake of polyunsaturated fatty acids depletes antioxidant defence in target tissues, providing a possible potentiating mechanism for carcinogenesis. Results showed a very high incidence of hormone-induced adenocarcinomas of prostate and mammary gland, irrespective of diet. There was no difference in the pattern of carcinogenesis in different prostatic locations, weight of the prostate, or weight gain between male rats on the high-fat diet compared with the control (standard, low-fat) diet. In female rats, the incidence of mammary cancer and the body-weight gain were the same in both dietary groups, and breast alpha-tocopherol was also unaffected by dietary fat intake. Our present results are supportive of recent cohort studies that reported no significant association between intake of fat and the development of human prostate and breast cancer, and do not support a role for dietary fat in promoting sex hormone-induced prostate and mammary carcinogenesis.

Fish oil slows S phase progression and may cause upstream shift of DHFR replication origin ori-beta in CHO cells

Fish oils (FOs) have been noted to reduce growth and proliferation of certain tumor cells, effects usually attributed to the content of polyunsaturated fatty acids of the n-3 family, which are thought to modulate cellular signaling pathways. We investigated the influence of FO on cell cycle kinetics of cultured Chinese hamster ovary cells. Exponentially growing cells were labeled with 5-bromo-2'-deoxyuridine (BrdU) and analyzed by flow cytometry after 5-day treatment with exogenous fat. Bivariate BrdU-DNA analysis indicated slower progression through S phase and thus longer S phase duration time in FO- but not corn oil-treated or control cells. We hypothesize that FO treatment might interfere with spatial/temporal organization of replication origins. Therefore, we mapped the well-characterized replication origin ori-beta downstream of the dihydrofolate reductase gene with the nascent strand length assay. Three DNA marker segments with known positions relative to this origin were amplified by PCR. By quantitatively assessing DNA length of the fragments in all fractions containing these markers, the location of ori-beta was established. In control or corn oil-treated cells, the location of ori-beta was consistent with previous studies. However, in FO-treated cells, DNA replication appears to start from a new site located farther upstream from ori-beta, suggesting a different replication initiation pattern. This study suggests novel mechanism(s) by which fats affect cell proliferation and DNA replication in mammalian cells.

Peroxisome proliferator-activated receptor alpha in the human breast cancer cell lines MCF-7 and MDA-MB-231

Peroxisome proliferator-activated receptor (PPAR) alpha is a ligand-activated transcription factor that has been linked with rodent hepatocarcinogenesis. It has been suggested that PPARalpha mRNA expression levels are an important determinant of rodent hepatic tumorigenicity. Previous work in rat mammary gland epithelial cells showed significantly increased PPARalpha mRNA expression in carcinomas, suggesting the possible role of this isoform in rodent mammary gland carcinogenesis. In this study we sought to determine whether PPARalpha is expressed and dynamically regulated in human breast cancer MCF-7 and MDA-MB-231 cells. Having established the presence of PPARalpha in both cell types, we then examined the consequence of PPARalpha activation, by its ligands Wy-14,643 and clofibrate, on proliferation. With real-time reverse transcriptase-polymerase chain reaction, we showed that PPARalpha mRNA was dynamically regulated in MDA-MB-231 cells and that PPARalpha activation significantly increased proliferation of the cell line. In contrast, PPARalpha expression in MCF-7 cells did not change with proliferation during culture and was present at significantly lower levels than in MDA-MB-231 cells. However, PPARalpha ligand activation still significantly increased the proliferation of MCF-7 cells. The promotion of proliferation in breast cancer cell lines following PPARalpha activation was in stark contrast to the effects of PPARgamma-activating ligands that decrease proliferation in human breast cancer cells. Our results established the presence of PPARalpha in human breast cancer cell lines and showed for the first time that activation of PPARalpha in human breast cancer cells promoted proliferation. Hence, this pathway may be significant in mammary gland tumorigenesis.

Dietary fat reduction to reduce prostate cancer risk: controlled enthusiasm, learning a lesson from breast or other cancers, and the big picture

Breast and prostate cancer share similar intrinsic and extrinsic risk factors. Based on laboratory, ecologic/international comparison, and case-control studies, the impact of dietary fat or other fat subtypes has been suggested as a potential route to reduce risk. Recent large-scale prospective studies have failed to find an association between fat and breast cancer risk. These studies may provide some insight for researchers examining the relation between fat and prostate cancer. Prospective studies to date have also failed to find a consistent association between prostate cancer and fat intake. Some fat subtypes (eg, saturated fat) or other lifestyle changes (eg, obesity, physical activity) may affect risk and progression of these cancers when examining the sum total of the research, but more precise and specific investigations in humans are needed to address these issues. Other concerns, such as the impact of excess energy or overall caloric consumption on carcinogenesis, still need to be addressed, as well as other methodologic limitations of past investigations. Large gaps exist in environmental (eg, diet, lifestyle) and heritable causes of these diseases. Regardless, until more extensive research is completed, lifestyle changes should be recommended based on reducing morbidity and mortality from cardiovascular disease-the number 1 cause of death in the United States. Additionally, cardiovascular disease remains the number 1 or 2 cause of death in patients diagnosed with breast or prostate cancer. Practical and simple dietary changes should be encouraged by health professionals because they could improve the overall longevity and quality of patients' lives. Numerous ongoing prospective studies of diet and cancer should provide researchers and the public with much-needed answers in this area.

Regulation of tumor angiogenesis by dietary fatty acids and eicosanoids

Angiogenesis is a prerequisite for tumor growth and metastasis. Vascular endothelial cell proliferation, migration, and capillary formation are stimulated by angiogenic growth factors, which include the proteins vascular endothelial growth factor, basic fibroblast growth factor, and transforming growth factor-beta, and eicosanoids synthesized from n-6 fatty acids. Clinical studies have shown that angiogenesis in solid tumors relates to a poor prognosis and, in premalignant lesions, indicates potential for cancerous transformation. High-fat, n-6 fatty acid-rich diets were associated with a relatively poor prognosis in breast cancer patients; in a nude mouse model the same diet enhanced breast cancer progression, whereas n-3 fatty acids exerted suppressive effects that were associated with impaired angiogenesis. Lipoxygenase and cyclooxygenase products of n-6 fatty acid metabolism are angiogenic in in vitro assays. This activity is blocked by pharmacological inhibitors of eicosanoid biosynthesis, and one, indomethacin, suppressed n-6 fatty acid-stimulated murine mammary carcinoma growth and metastasis and tumor vascularization. Review of the experimental data suggests that selective inhibitors of eicosanoid-synthesizing enzymes and dietary intervention with n-3 fatty acids merit clinical evaluation as adjuvant therapy and chemopreventive agents.

Dietary fat and breast cancer

One of the most often studied associations in epidemiology is dietary fat and breast cancer risk. That migrants from low-risk countries increase their risk on immigrating to higher-risk countries suggests that some modifiable lifestyle or environmental factor is responsible for the development of breast cancer. Although early international correlational studies and experimental animals studies support dietary fat as a risk factor for breast cancer, more recent data from case-control studies and cohort studies have been equivocal, thus the analytical data do not support a strong positive association. The conflicting results from analytic studies may be due to methodologic issues associated with study design, dietary assessment tools, measurement error, improper statistical analyses, and a lack of heterogeneity in fat intake among the study population. Moreover, current dietary questionnaires may be inadequate in capturing true dietary intakes or capturing the risk with exposure during earlier periods of a woman's life. Although two large clinical trials investigating the fat/breast cancer relationships issue are underway, researchers are generally skeptical at their ability to detect an independent association between fat and breast cancer risk. Further epidemiologic studies using current methodology may not prove to be fruitful in generating definitive answers to shed light on this controversial issue. In addition, rather than concentrating on dietary fat, researchers should focus on diets that are not only low in saturated fat, but also high in fruit and vegetable consumption. Researchers should take advantage of advances in molecular and genetic technology for a different perspective in examining the issue. For example, markers of susceptibility to breast cancer that can detect women at higher risk for breast cancer may be helpful in clarifying the role of dietary fat. More comprehensive and multiple approaches to studying dietary factors and breast cancer are recommended.

Inhibition of cyclooxygenase-2 suppresses angiogenesis and the growth of prostate cancer in vivo

PURPOSE

Cyclooxygenase (COX)-2, an inducible enzyme which catalyzes the formation of prostaglandins from arachidonic acid, is expressed in prostate cancer specimens and cell lines. To evaluate the in vivo efficacy of a COX-2 inhibitor in prostate cancer, NS398 was administered to mice inoculated with the PC-3 human prostate cancer cell line.

MATERIALS AND METHODS

A total of 28 male nude mice were inoculated subcutaneously with 1 million PC-3 cells. Tumors were palpable in all 28 animals 1 week after inoculation and mice were randomized to receive either vehicle (control) or NS398, 3 mg./kg. body weight, intraperitoneally three times weekly for 9 weeks. Tumors were measured at weekly intervals. After a 10-week experimental period, mice were euthanized and tumors were immuno- histochemically assayed for proliferation (PCNA), apoptosis (TUNEL) and microvessel density (MVD) (Factor-VIII-related antigen). Tumor VEGF content was assayed by Western blotting.

RESULTS

NS398 induced a sustained inhibition of PC-3 tumor cell growth and a regression of existing tumors. Average tumor surface area from control mice was 285 mm.2 as compared with 22 mm.2 from treated mice (93% inhibition, p <0.001). Immunohistochemical analysis revealed that NS398 had no effect on proliferation (PCNA), but induced apoptosis (TUNEL) and decreased MVD (angiogenesis). VEGF expression was also significantly down regulated in the NS398-treated tumors.

CONCLUSIONS

These results demonstrate that a selective COX-2 inhibitor suppresses PC-3 cell tumor growth in vivo. Tumor growth suppression is achieved by a combination of direct induction of tumor cell apoptosis and down regulation of tumor VEGF with decreased angiogenesis

The pathology of essential fatty acid deficiency: is it cell adhesion mediated?

For almost 70 years, essential fatty acid deficiency has been known to be associated with skin disorders, vessel abnormalities, and increased tumorigenesis. However, the underlying molecular and cellular mechanism is largely unknown. Recently, it has been reported that essential fatty acids regulate cell adhesion by modifying the expression of cell adhesion molecules. These findings may provide molecular explanations for those phenomena seen in EFAD and this paper aims to discuss these relationships and raise points for further discussion.

Inhibition of cyclooxygenase-2 suppresses angiogenesis and the growth of prostate cancer in vivo

PURPOSE

Cyclooxygenase (COX)-2, an inducible enzyme which catalyzes the formation of prostaglandins from arachidonic acid, is expressed in prostate cancer specimens and cell lines. To evaluate the in vivo efficacy of a COX-2 inhibitor in prostate cancer, NS398 was administered to mice inoculated with the PC-3 human prostate cancer cell line.

MATERIALS AND METHODS

A total of 28 male nude mice were inoculated subcutaneously with 1 million PC-3 cells. Tumors were palpable in all 28 animals 1 week after inoculation and mice were randomized to receive either vehicle (control) or NS398, 3 mg./kg. body weight, intraperitoneally three times weekly for 9 weeks. Tumors were measured at weekly intervals. After a 10-week experimental period, mice were euthanized and tumors were immuno- histochemically assayed for proliferation (PCNA), apoptosis (TUNEL) and microvessel density (MVD) (Factor-VIII-related antigen). Tumor VEGF content was assayed by Western blotting.

RESULTS

NS398 induced a sustained inhibition of PC-3 tumor cell growth and a regression of existing tumors. Average tumor surface area from control mice was 285 mm.2 as compared with 22 mm.2 from treated mice (93% inhibition, p <0.001). Immunohistochemical analysis revealed that NS398 had no effect on proliferation (PCNA), but induced apoptosis (TUNEL) and decreased MVD (angiogenesis). VEGF expression was also significantly down regulated in the NS398-treated tumors.

CONCLUSIONS

These results demonstrate that a selective COX-2 inhibitor suppresses PC-3 cell tumor growth in vivo. Tumor growth suppression is achieved by a combination of direct induction of tumor cell apoptosis and down regulation of tumor VEGF with decreased angiogenesis

Diminution of the development of experimental metastases produced by murine metastatic lines in essential fatty acid-deficient host mice

In a previous study we found that the capacity for spontaneous metastases of tumors developed after subcutaneous transplantation of RSV-transformed Balb/c 3T3 cells was reduced in essential fatty acids (EFA)-deficient host animals. In the present study, we have extended our investigation by considering the requirement of EFA for the formation of lung colonies obtained by i.v. injection of two metastatic murine cell lines of different origin: (1) T3 cells, a highly metastatic cell line isolated from a fibrosarcoma, and (2) the F10 variant of B16 melanoma (B16-F10 cells). We found that EFA deficiency reduces the lung colonization of both T3 cells and B16-F10 cells without affecting the retention of tumor cells in the lung. NK cells did not seem to be involved in the diminution of lung colonization in EFA-deficient animals. Furthermore, by examining histologically the lung parenchyma at successive intervals after tumor cell injection, we found that, in comparison with control mice, EFA-deficient animals had fewer lung colonies and a prevalence of smaller microcolonies during the entire period of observation. This led us to conclude that the diminution in development of tumor colonies in the lungs of EFA-deficient host animals was related to a reduced growth rate of tumor cells at this site.