Dietary fatty acids and human breast cancer cell growth, invasion, and metastasis

Lysine 63-linked ubiquitination is important for arachidonic acid-induced cellular adhesion and migration

Arachidonic acid, a dietary cis-polyunsaturated fatty acid, stimulates adhesion and migration of human cancer cells on the extracellular matrix by activation of intracellular signaling pathways. Polyubiquitin chains bearing linkages through different lysine residues convey distinct structural and functional information that is important for signal transduction. We investigated whether ubiquitination was required for arachidonic acid-induced cellular adhesion and migration of MDA-MB-435 cells on collagen type IV. An E1 (ubiquitin-activating enzyme) inhibitor, PYR-431, completely abrogated arachidonic acid-stimulated adhesion. Additionally, expression of a lysine null mutant ubiquitin prevented activation of cellular adhesion. Cells expressing ubiquitin in which lysine 63 (K63) was mutated to arginine (K63R) were unable to adhere to collagen upon exposure to arachidonic acid. When K63 was the only lysine present, the cells retained the ability to adhere, indicating that K63-linked ubiquitin is both necessary and sufficient. Moreover, K63-linked ubiquitin was required for the induction of cell migration by arachidonic acid. The ubiquitin mutants and PYR-431 did not prevent arachidonic acid-induced phosphorylation of TGF-β activated kinase-1 (TAK1) and p38 MAPK, suggesting K63-linked ubiquitination occurs downstream of MAPK. These novel findings are the first to demonstrate a role for K63-linked ubiquitination in promoting cell adhesion and migration.

Serum insulin-like growth factor binding protein-1 levels and bone mineral density in older adults: the Rancho Bernardo Study

Insulin-like growth factor-I (IGF-I) stimulates osteoblast function, inhibits collagen matrix degradation, and is positively associated with bone mineral density in most but not all studies. We previously reported that IGF-I was positively associated with BMD at the spine and hip in women but not men. Insulin-like growth factor binding protein-1 (IGFBP-1), a potent modulator of IGF-I, is expressed in normal osteoblasts and inhibits collagen gene expression in bone, but little is known about the relationship between IGFBP-1 and bone mineral density (BMD). We report a cross-sectional study of serum IGFBP-1 levels and BMD in 1,139 community-dwelling men and postmenopausal women (not using estrogen), aged 44-98. In both sexes, IGFBP-1 levels increased linearly with age (p<0.001) and decreased with body mass index (BMI) quartile (p<0.001). After adjusting for age and BMI, there was no significant association between IGFBP-1 and BMD at the hip or spine. IGF-I and IGFBP-1 were weakly and inversely associated with each other. These findings suggest that if there is an important role for IGFBP-1 in bone metabolism, it is mediated or confounded by weight. Studies are needed to further investigate the relationship between inhibitory components of IGF-1 and bone loss.

The effect of osteogenic growth factors on bone growth into a ceramic filled defect around an implant

Currently available synthetic bone substitutes perform poorly compared to autograft. It is hoped that by adding osteogenic growth factors to the materials, new bone formation could be increased and the clinical outcome improved. In this study, IGF-1, bFGF and TGFbeta1, alone and in combination, were absorbed onto a carrier of beta-tricalcium phosphate (betaTCP) and implanted into a defect around a hydroxyapatite-coated, stainless steel implant in the proximal tibia of rat in a model of revision arthroplasty. Animals were sacrificed at 6 and 26 weeks for routine histology and histomorphometry and mechanical push out tests. The results show that only bFGF had a significant effect on ceramic resorption. The groups that received bFGF and bFGF in combination with TGFbeta1 had smaller and fewer betaTCP particles remaining in the defect at 6 and 26 weeks. No growth factor combination significantly enhanced new bone formation or the mechanical strength of the implant. These results indicate that, of the growth factors tested, only bFGF had any beneficial effect on the host response to the implant, perhaps by delaying osteoblast differentiation and thereby prolonging osteoclast access to the ceramic.

The effect of 15-lipoxygenase-1 expression on cancer cells

Lipoxygenases oxidatively metabolize polyunsaturated fatty acids to a rich spectrum of biologically active products. One enzyme of the lipoxygenase family, Arachidonate 15-lipoxygenase-1 (arachidonate:oxygen 15-oxidoreductase, EC 1.13.11.33), is implicated in several forms of epithelial cell cancers, and provides a rationale for exploring its role in the progression and metastasis of cancers. Thus, 15-LO-1 could be a marker of the growth and spread of cancers. The importance of 15-LO-1 expression is imparted by its metabolic product of linoleic acid, yielding 13-(S)-hydroxyoctadecadienoic acid (13-(S)-HODE). In order to maximize our understanding of the roles of lipoxygenases and cyclooxygenases in cancer, it is necessary to correlate their metabolic pathways to the respective expression levels, and not exaggerate the presence or absence of an enzyme or its function when it clearly is not there. It is also important to acknowledge that some forms of these enzymes may not even be relevant to human disease. Although it is unlikely that any single gene is sufficient to account for the complex etiology of cancer, 15-LO-1 overexpression is clearly a key component in the cell proliferation process. This article is divided into three sections emphasizing the key role of 15-LO-1 in prostate, colorectal, and breast cancers.

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.

Insulin-like growth factor binding proteins in femoral and vertebral bone marrow stromal cells: expression and regulation by thyroid hormone and dexamethasone

Insulin-like growth factor (IGF)-I is an important regulator of bone metabolism. Clinical observations suggest that different anatomic sites within the adult skeleton respond differently to hormonal and therapeutic treatment, and recent studies on bone marrow stromal cells in culture show that there are skeletal site-dependent differences in the gene expression of IGF-I. The actions of IGF-I and -II on bone cells are known to be modulated by the IGF binding proteins (IGFBP)-1 through -6 and the Type I and Type II IGF receptors. Therefore, we compared the expression of IGFBP-1 through -6 in adult female rat bone marrow stromal cell cultures derived from two separate skeletal sites: vertebrae and femurs. The cultures were maintained simultaneously under conditions that support osteoblast differentiation from osteoprogenitors present in the femoral and vertebral marrow cell populations. We also addressed whether IGFBP messenger RNA levels are regulated by thyroid hormone (T(3)) and dexamethasone (dex) treatment in femoral vs. vertebral marrow stromal cells in vitro, since steroid hormones play an important role in skeletal function. Northern blot analyses revealed that there are distinct skeletal site differences in the gene expression of IGFBPs. The vertebral marrow cultures express IGFBP-2 through -6 mRNAs, with IGFBP-2, IGFBP-4, and IGFBP-6 mRNAs predominating. The femoral marrow stromal cell cultures express only IGFBP-4 and IGFBP-6. Importantly, vertebral marrow cultures have much higher IGFBP mRNA steady-state levels than femoral cultures for all the detected IGFBP transcripts. IGFBP-1 is not detected in either femoral or vertebral cultures. In addition to a skeletal site difference, we show that T(3) and dex regulate the expression of specific IGFBP mRNAs. T(3) treatment also upregulates IGF-I protein secretion by vertebral marrow stromal cell cultures. Interestingly, the type I receptor for IGF-I was expressed equivalently in cultures from the two skeletal sites. These findings have important implications for the anatomical site specificities of hormonal responses that are noted in the skeleton.

Insulin-Like growth factor I: implications in aging

According to the somatomedin model, growth hormone (GH)-dependent hepatic synthesis is responsible for maintaining circulating insulin-like growth factor (IGF)-I levels. On the other hand, the local autocrine/paracrine IGF-I expression in peripheral tissue is generally GH-independent and reflects the effects of various and tissue-specific trophic hormones. Circulating IGF-I levels undergo important age-related variations increasing at puberty and decreasing, thereafter, to low levels in the elderly. Low IGF-I levels in the elderly mainly reflect impaired somatotroph secretion but the decline in gonadal sex steroid levels, some protein and micronutrients malnutrition as well as age-dependent variations in IGF-binding proteins may also play a role in the age-related decrease in IGF-I activity. This, in turn, partially accounts for age-related changes in bones, muscles, cardiovascular system, central nervous system and the immune system. However, it is currently unclear whether treatment with exogenous IGF-I can retard or reverse age-related changes in body structure and function.

Correlation of the osteoblastic phenotype with prostate-specific antigen expression in metastatic prostate cancer: implications for paracrine growth

The characteristic sclerotic appearance of bone metastases from prostate cancer is unexplained but could involve excess peritumoural activity of osteoblast mitogens such as the insulin-like growth factors (IGFs). Since prostatic metastases are distinguished by androgen-dependent secretion of prostate-specific antigen (PSA), a serine protease which cleaves extracellular IGF-binding proteins and thereby enhances the bioavailability of IGFs, the relationship was examined between tumour PSA expression and the osteoblastic phenotype. To this end, a cohort of 27 prostate cancer patients was evaluated to determine the relationship between serum PSA and radiographic bone lesion density at first presentation with metastatic disease. No linear correlation between absolute PSA levels and metastatic osteosclerosis was apparent. However, non-parametric statistical analysis revealed a highly significant link between low-PSA (<20 ng/ml) metastatic prostate cancer and osteolytic bone lesions (p<0.0001, chi(2)=21.5). This finding raises the possibility that the osteoblastic phenotype of prostate cancer derives in part from PSA-dependent proteolysis of IGF-binding proteins within bone matrix.

Enhanced angiogenesis and growth of 12-lipoxygenase gene-transfected MCF-7 human breast cancer cells in athymic nude mice

Transfection of the estrogen-dependent and poorly invasive MCF-7 human breast cancer cell line so that it stably overexpressed 12-lipoxygenase and secreted high levels of 12-hydroxyeicosatetraenoic acid when cultured with arachidonate resulted in rapid growth in athymic nude mice when compared with the parental line. This enhanced acquisition of tumor mass was a result of both increased cell proliferation and reduced apoptotic cell death and was accompanied by high angiogenic activity.

Essential fatty acids, insulin resistance, and breast cancer risk

This review compares the prevalence of hyperinsulinemic insulin resistance in Caucasian-American women with that in Japanese-American and Pima Indian minority groups in the United States. It also examines the differences in breast cancer risk between these ethnic groups and suggests that risk may be modulated by ethnic genetic susceptibility to the effect of the Western diet in precipitating insulin resistance. It is widely agreed that the Western diet with its high saturated fatty acid content and high n-6/n-3 ratio of polyunsaturated fatty acids (PUFAs) favors the manifestation of hyperinsulinemia in individuals who are genetically predisposed. A number of case-control studies have shown hyperinsulinemia to be a marker of increased breast cancer risk, particularly in obese postmenopausal women. Mechanisms that have been postulated include an increased sex steroid level associated with a decreased serum level of sex hormone-binding globulin and an increased bioactive level of insulin-like growth factor I, which may synergize with estrogen in promoting mammary carcinogenesis. Dietary supplements rich in n-3 PUFAs have been shown to inhibit the growth of human breast cancer implants in nude mice, and members of the n-3 PUFA series can inhibit the growth of human breast cancer cell lines in vitro. On the basis of this experimental evidence, some have proposed dietary supplements rich in n-3 PUFAs for breast cancer protection. However, increased consumption of PUFAs requires increased intake of antioxidants. Vitamin E may be the most suitable agent, especially because of its added advantage that in animal models it is reported to reduce the incidence of carcinogen-induced mammary tumors. Preliminary trials of the combination may best be planned as adjuvant treatment after primary surgery for breast cancer, and the insulin hypothesis could be tested in the trials by monitoring fasting insulin and sex steroid levels.

The challenges of assessing fat intake in cancer research investigations

Ecologic comparison of the incidence of cancer (eg, largescale differences between countries in the incidence of breast, prostate, and colon cancer) can be explained best by substantial differences in the intake of dietary fat. Additionally, there is a vast amount of animal and mechanistic data that strongly supports the hypothesis that ditary fat, independent of caloric intake, appears to have a major effect on the incidence and mortality rates for cancer. Yet, results from human case and cohort studies are inconsistent in linking carcinogenesis with fat intake. This is due to several factors. Reported intakes may not reflect previous long-term intakes and may be con-founded by several sources of error, including memory and estimates of portion size. Additionally, ongoing media reports of adverse health effects from high-fat diets may impart a social desirability bias to self-reporting of fat intake. These factors may be significant when investigating the relationship between dietary intake and cancer. Studies have shown considerable error in self-reported dietary data, with under-estimations in energy intake ranging from 3% to 18%. Such a wide range likely is due to differences in dietary assessment methodologies, which highlights the need to continue to develop improved techniques of data collection to relate nutrition better to health outcomes. The Women's Intervention Nutrition Study (WINS) is investigating the effect of dietary fat on the incidence of recurrence and survival in women with early-stage breast cancer. WINS is employing the multiple-pass 24-hour telephone recall system along with enhanced quality control measures to assess dietary intake. This dietary assessment method is particularly applicable when comparing two populations when one population is treated by an extensive dietary intervention.

Breast cancer: weighing the evidence for a promoting role of dietary fat

It has been hypothesized that a high-fat diet promotes the development of postmenopausal breast cancer. This contention is supported by data showing high international correlations between fat intake and breast cancer rates, modest positive associations with a high-fat diet in case-control studies, and animal model studies that have consistently demonstrated that dietary fat influences mammary cancer development at several stages in the carcinogenic process. A number of plausible biologic mechanisms have been suggested that may explain such promotional effects. In contrast, dietary fat intake is unrelated to the risk of breast cancer in cohort studies. The conflicting findings from cohort studies have created uncertainty regarding nutritional recommendations and breast cancer prevention. After reviewing key scientific findings that are relevant to this issue, the following conclusion is drawn: In the absence of data from dietary intervention trials, the weight of available evidence suggests that the type and amount of fat in the diet is related to postmenopausal breast cancer and that the inability to detect associations within populations (cohort studies) is because of measurement error and the relative homogeneity of diets measured. It is expected that the results from intervention trials will clarify this issue.

Eicosanoids as mediators of linoleic acid-stimulated invasion and type IV collagenase production by a metastatic human breast cancer cell line

Diets rich in linoleic acid (LA) stimulate the metastasis of MDA-MB-435 human breast cancer cells from the mammary fat pads of nude mice. This omega-6 fatty acid is metabolized to various cyclo-oxygenase and lipoxygenase products, several of which have been previously associated with tumor cell invasion and metastasis. We now report that MDA-MB-435 cells secreted increased levels of prostaglandin E2 (PGE2), and 12-hydroxyeicosatetraenoic acid (12-HETE) and 15-HETE when cultured in the presence of 2.7 microM (0.75 micrograms/ml) LA; 5-HETE secretion was unchanged. The 12-lipoxygenase inhibitor esculetin (20 microM) completely blocked the LA-stimulated 12-HETE secretion. Linoleic acid also increased MDA-MB-435 cell invasion in an in vitro assay; this stimulation was abolished by 20 microM esculetin, but was unaffected by piroxicam, a selective cyclooxygenase inhibitor. The effect of LA on invasion was replicated by 0.1 microM 12-HETE, but not by 5-HETE or PGE2; 15-HETE was stimulatory only at a concentration of 1.0 microM. Zymographic and Northern blot analyses showed that these events are accompanied by the induction of 92 kDa isoform type IV collagenase (metalloproteinase-9) enzymic activity and mRNA expression by exogenous LA and 12-HETE, and their suppression by the 12-lipoxygenase inhibitor. These results suggest that the effects of dietary LA on breast cancer cell metastasis in the nude mouse model are due, at least in part, to enhanced 12-HETE biosynthesis, with an associated increase in proteolytic enzyme activity and tumor cell invasiveness.

Dietary linoleic acid-stimulated human breast cancer cell growth and metastasis in nude mice and their suppression by indomethacin, a cyclooxygenase inhibitor

Growth and metastasis to the lung of the human breast cancer cell line MDA-MB-435 in nude mice fed a high-fat (20% wt/wt) high-linoleic acid (LA; 12% wt/wt) diet were significantly reduced by the addition of the cyclooxygenase inhibitor indomethacin to the drinking water at a dose of 10 micrograms/ml (approximately 1 mg/kg body wt). No toxicity was observed in these mice; at 20 micrograms/ml indomethacin, gastric ulcerations occurred. After necropsy, tumor eicosanoids were measured by radioimmunoassay in the control and 10 micrograms/ml indomethacin treatment groups. Levels of the cyclooxygenase products prostaglandin (PG) E (PGE), 6-keto-PGF1 alpha, and thromboxane B2 (TxB2) were significantly reduced in indomethacin-treated mice compared with controls; however, the 6-keto-PGF1 alpha-to-TxB2 ratio was significantly increased. Two lipoxygenase products, 5-hydroxyeicosatetraenoic acid (5-HETE) and 15-HETE, were unaffected, but the 12-HETE levels were increased compared with the untreated high-LA-fed group. Metastases to the lungs in mice fed a high-fat low-LA (2% wt/wt) diet were also reduced compared with those in the high-LA-fed control mice, but whereas tumor cyclooxygenase and lipoxygenase product levels were reduced, no change in the 6-keto-PGF1 alpha-to-TxB2 ratio was observed. The use of selective cyclooxygenase inhibitors may prevent LA-mediated progression of breast cancer at several levels of the metastatic cascade, among which may be interference with tumor cell-vascular endothelial cell interaction and with angiogenesis.

Age-related bone loss and senile osteoporosis: evidence for both secondary hyperparathyroidism and skeletal growth factor deficiency in the elderly

Aging is characterized by a decrease in bone volume, implying that net bone resorption exceeds net bone formation. This age-related bone loss can be regarded as the main determinant of hip fracture risk in the elderly. In the concept of senile osteoporosis, a key role has been attributed to vitamin D deficiency. Lack of vitamin D activity may affect femoral strength through impaired mineralization as well as through a hyperparathyroidism-mediated increase in bone resorption. In addition to vitamin D-related mechanisms, recent evidence has indicated a decline in the skeletal content of anabolic growth factors--such as insulin-like growth factor-I (IGF-I)--in femoral (cortical) bone, suggesting that skeletal growth factor deficiency may contribute to the age-related bone loss in the proximal femur as well. It is tempting to speculate that skeletal IGF-I loss might, at least partially, be accounted for by growth hormone deficiency. However, critical evidence does not yet support the concept that the decreased activity of the growth hormone-IGF-I-axis alters bone remodeling, and the extent to which serum concentrations of growth factors are reflective of skeletal activity remains to be clarified.

Growth hormone, insulin-like growth factors, and the senescent skeleton: Ponce de Leon's Fountain revisited?

As the population ages, the prevalence of osteoporosis will continue to rise. Yet, the mechanisms leading to age-related bone loss remain poorly defined. Furthermore, extensive longitudinal studies of bone mass, especially in the three decades beyond menopause, have not been completed. Although calciotropic hormones, growth hormone (GH), and insulin-like growth factor-I (IGF-I) change with age, it is not certain if these changes are responsible for age-related bone loss. Nor is it clear if the "senescent" osteoblast is fully responsive to growth factor stimulation. To complicate matters further, both circulatory and skeletal IGF regulatory systems are extremely redundant. Changes in serum IGFs may lead to compensatory alterations in IGF receptor number, IGF binding protein (IGFBP) synthesis, or IGFBP catabolism. What is measured in serum, may, in the end, be either a mirror or a mirage of skeletal IGF action! Clinical trials with "replacement" doses of GH or IGF-I are underway. But, critical evidence does not yet support the concept that a true "sommatopause" alters bone remodeling. Moreover, only scarce data exist that GH augments bone formation or prevents bone loss in the elderly. As clinicians expand the use of recombinant growth factors to elders, ethical and clinical issues surrounding administration of the new "fountain of youth" will be revisited. For basic scientists studying skeletal growth factors and their relationship to senescence, significant questions remain unanswered. New technological advances will provide clues about the basic mechanisms of skeletal aging.(ABSTRACT TRUNCATED AT 250 WORDS)