DIETARY FAT AND CANCER Genetic and Molecular Interactions ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY Editorial Board: NATHAN BACK, State University of New York at Buffalo !RUN R. COHEN, The Weizmann Institute of Science DAVID KRITCHEVSKY, Wistar Institute ABEL LAJTHA, N. S. Kline Institute for Psychiatric Research RODOLFO PAOLETTI, University of Milan Recent Volumes in this Series Volume 413 OPTICAL IMAGING OF BRAIN FUNCTION AND METABOLISM 2: Physiological Basis and Comparison to Other Functional Neuroimaging Methods Edited by Arno Villringer and Ulrich Dirnagl Volume 414 ENZYMOLOGY AND MOLECULAR BIOLOGY OF CARBONYL METABOLISM 6 Edited by Henry Weiner, Ronald Lindahl, David W. Crabb, and T. Geoffrey Flynn Volume 415 FOOD PROTEINS AND LIPIDS Edited by Srinivasan Damodaran Volume 416 PLATELET-ACTIVATING FACTOR AND RELATED LIPID MEDIA TORS 2: Roles in Health and Disease Edited by Santosh Nigam, Gert Kunkel, and Stephen M. Prescott Volume417 DENDRITIC CELLS IN FUNDAMENTAL AND CLINICAL IMMUNOLOGY, Volume 3 Edited by Paola Ricciardi-Castagnoli Volume 418 STREPTOCOCCI AND THE HOST Edited by Thea Horaud, Anne Bouvet, Roland Leclerq, Henri de Montclos, and Michel Sicard Volume 419 ADP-RIBOSYLATION IN ANIMAL TISSUES: Structure, Function, and Biology of Mono (ADP-ribosyl) Transferases and Related Enzymes Edited by Friedrich Haag and Friedrich Koch-Nolte Volume 420 ADVANCES IN CIRRHOSIS, HYPERAMMONEMIA, AND HEPATIC ENCEPHALOPATHY Edited by Vicente Felipo Volume 421 CELLULAR PEPTIDASES IN IMMUNE FUNCTIONS AND DISEASES Edited by Siegfried Ansorge and Jiirgen Langner Volume 422 DIETARY FAT AND CANCER: Genetic and Molecular Interactions Edited under the auspices of the American Institute for Cancer Research A Continuation Order Plan is available for this series. A continuation order will bring delivery of each new volume immediately upon publication. Volumes are billed only upon actual shipment. For further information please contact the publisher. DIETARY FAT AND CANCER Genetic and Molecular Interactions Edited under the auspices of the American Institute for Cancer Research Washington, D.C. SPRINGER SCIENCE+BUSINESS MEDIA, LLC Llbrary of Congress Cataloglng-In-Publlcatlon Data Dietary fat and cancer: genetic and molecular interactions / edited under the auspices of the American Institute for Cancer Research. p. cm. -- (Advances in experimental medicine and biology ; v. 422) "Proceedings of the American Institutefor Cancer Research's Seventh Annual Conference on Dietary Fat and Cancer: Genetic and Molecular Interactions, held August 28-30, 1996 in Washington, D.C."--T.p. versa. Includes bibliographical references and index. ISBN 978-1-4419-3282-2 ISBN 978-1-4757-2670-1 (eBook) DOI 10.1007/978-1-4757-2670-1 1. Cancer--Nutritional aspects--Congresses. 2. Lipids in human nutrition--Congresses. 3. Lipids--Pathophysiology--Congresses. 4. Cancer--Molecular aspects--Congresses. 5. Cancer--Genetic aspects--Congresses. 1. American Institute for Cancer Research. II. Conference an Dietary Fat and Cancer: Genetic and Molecular Interactions (1996 : Washington, D.C.) III. Series. [DNLM: 1. Neoplasms--etiology--congresses. 2. Neoplasms -genetics--congresses. 3. Dietary Fats--adverse effects- -congresses. 4. Dietary Fats--metabolism--congresses. 5. Fatty Acids--genetics. W1 AD559 v.422 1997 I az 202 D5646 1997J RC268.45.D5626 1997 616.99'4071--dc21 DNLM/DLC for Library of Congress 97-4389 CIP l American Institute for Cancer Research Proceedings ofthe American Institute for Cancer Research's Seventh Annual Conference on Dietary Fat and Cancer: Genetic and Molecular Interactions, held August 28 - 30, 1996, in Washington, D.C. ISBN 978-1-4419-3282-2 © 1997 Springer Science+Business Media New York Originally published by Plenum Press, New York in 1997 Softcover reprint ofthe hardcover lst edition 1997 http://www.plenum.com 10987654321 Ali rights reserved No part ofthis book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher PREFACE The annual research conference for 1996 of the American Institute for Cancer Re search was again held at the Loews L'Enfant Plaza Hotel in Washington, DC, August 29 and 30. The topic for this, the seventh in the series, was "Dietary Fat and Cancer: Genetic and Molecular Mechanisms." Two separate presentations were given as the conference overview. "Fat and Cancer: The Epidemiologic Evidence in Perspective" noted that die tary fat can be saturated, largely from animal or dairy sources, or mono- or polyunsatu rated, mostly from plant sources. Unlike animal fats, fish contain relatively high levels of protective omega-3 fatty acids. Although the hypothesis that dietary fat is associated with cancer is plausible, the mechanisms involved are reasonable, and many animal studies support the hypothesis, there are many obstacles in any direct extrapolation to humans, in cluding imprecise measures of dietary fat intake, variability in individual diets, and spe cies variations. Despite these limitations, there is a weak positive correlation between colon cancer and dietary fat intake, but with substantial differences for various ethnic groups. In the case of breast cancer, there is substantial variation among countries and eth nic groups, but the overall evidence indicated an association with fat in the diet. Epidemiologic studies of dietary fat and prostate cancer are more consistent and most show a positive relationship. However, it was not clear which types of dietary fat were im plicated in the effect. Surprisingly, although the major etiologic factor for lung cancer is smoking, there are some fairly good correlations between high fat or cholesterol intake and this type of cancer. For other organ sites such as pancreas, endometrium, ovary, kid ney, bladder, and gallbladder, there is no compelling evidence for an effect of dietary fat. The second overview paper "Dietary Lipids and the Cancer Cascade" mentioned that although animal models implicate dietary lipid as a factor in development of malig nancies, testing this hypothesis in human intervention studies has been very slow. Prob lems include cost, controlling for changes in foods and nutrients, and quantitating levels of lipids and any changes accurately. Better elucidation of the molecular, biochemical, and cellular processes modulated by lipids will eventually allow novel means to assess ac curately the intake of dietary fats. The cancer process, from its beginning with a single mutated cell, requires many years to evolve to a life-threatening malignancy, thus affording opportunity for diet to in fluence both the rate of progression and the biological behavior of the neoplasm. Genetics has an important role in cancer initiation and progression, either by virtue of familial or germ line genes that are inherited and influence cancer risk, or by acquired defects in criti cal genes comprising the evolving tumor. Examples are the BRCA 1 and BRCA2 tumor suppressor genes; if a woman inherits a mutation in these genes, her risk of breast cancer increases measurably. Genes that determine capacity to either activate or detoxify chemi- v vi Preface cal carcinogens also influence the pattern of acquired mutations in critical tumor suppres sor genes. Persons who inherit two noneffective copies of the GSTM l (for glutathione-S transferase) gene have a significant increase in bladder cancer if they smoke since GST detoxifies a carcinogen in tobacco smoke. Inheriting the deletion carries little risk for those who do not smoke. These polymorphisms that affect risk of cancer may potentially interact with dietary factors. Since options for intervention are limited for those with de fective genes, prevention strategies involving diet and nutrition are more practical. Extrapolation from studies in mice with a genetic background leading to increased risk for mammary cancer indicates that delaying the onset of tumor development by die tary means is feasible. In mice lacking the critical p53 gene (knockout mouse) moderate calorie restriction delayed the onset of spontaneous tumors. Further, p53 may serve as an activator of apoptosis for damaged cells before they progress on to neoplasia. Angiogene sis, the means by which tumors develop vascular systems, also is important. There are pre liminary data that these processes can be controlled to a certain extent by dietary means. Reducing various cancer rates through dietary intervention is possible. The first of the subsequent sessions was entitled "Dietary Fat and Tumor Growth Regulation," with the first paper on specific studies of gene expression in chemically in duced mammary carcinogenesis. In female rats given the mammary carcinogen methylni trosourea and fed diets high in omega-6 polyunsaturated fatty acids (promoters), there was higher expression of cyclooxygenase 2 (COX-2) transcripts than in rats fed omega-3 fatty acids or control diets. Additional experiments suggested that a certain level of die tary cholesterol may inhibit de novo cholesterol synthesis in preneoplastic mammary epi thelial cells, thus decreasing their proliferative rate and neoplastic development. Likewise, in an estrogen-independent and highly metastatic human breast cancer cell line (MDA-MB-231) there was expression of a high level of COX-2. Exposure to the promot ing agent TPA caused further sustained enzyme expression. In contrast, the estrogen re ceptor positive human breast cancer cell line MCF-7, which has low invasive capacity, had a high level of COX-I expression and only a transient response to TPA. Reducing dietary intake of the omega-6 fatty acids, increasing the omega-3, developing a specific drug for inhibition of COX-2, and developing an inhibitor of lipoxygenase, another en zyme system involved in oxidative activation of fatty acids, were suggested as future chemopreventive approaches. Increased breast cancer cell proliferation was implicated as an important adverse factor in the survival of cancer patients. In cell cultures long chain saturated fatty acids such as stearate inhibited cancer cell proliferation but there was no effect on membrane fluidity. Inhibition by stearate paralleled a decrease in association of the transducer mole cules guanine nucleotide binding proteins (G-proteins) with the epidermal growth factor receptor (EGFR) but tyrosine phosphorylation of the EGFR was not affected. The unsatu rated long chain fatty acid oleate increased cell proliferation and G-protein association with EGFR. It was suggested that stearate may merit a specific controlled place in the diet. The second session "Dietary Fat and Signal Transduction" explored the mechanisms by which unsaturated fatty acids influence the processes involved in neoplasia. The ei cosanoids, derived from oxygenated arachidonic acid metabolites and the hydroxyei cosatetraenoic acids (HETEs) are involved in multiple steps of neoplasia and metastasis. HETEs affect tumor cell motility, interactions with the extracellular matrix, the release of lysosomal enzymes, and they act as signaling molecules. However, the unsaturated fatty acids in fish oils, namely eicosapentaenoic acid and docosahexaenoic acid, tend to reduce the development of colon tumors in rats treated with a colon carcinogen. These fatty acids modulate favorably the balance between colonic cell proliferation and apoptosis and de- Preface vii crease carcinogen-induced ras mutation in the colon. Further, in azoxymethane-treated rats, dietary fish oils decreased colonic phospholipase C gamma 1 expression and diacyl glycerol mass and blocked the azoxymethane-induced decrease in steady-state levels of select colonic protein kinase C (PKC) isozymes. The beneficial action of fish oils may re side in blocking the activation and downregulation of PKC isozymes. The emphasis then shifted to a different dietary component-choline. A deficiency leads to hepatocellular carcinoma in male rats. Adapting rat hepatocytes to grow in a choline-deficient medium caused the cells to acquire resistance to apoptosis and to pro duce hepatocellular carcinomas when injected into nude mice. These adapted hepatocytes were resistant to the transforming growth factors (TGF-Beta 1), which also induce cell death. Thus choline deficiency may act through induction of alterations in growth factor signaling pathways. Although peroxisome proliferators have been implicated as inducers of hepatic tumors in rodents, both humans and subhuman primates apparently are mini mally responsive or resistant to their action. The session on "Dietary Fat and Peroxisome Proliferator Activated Receptors" provided information on these cell constituents. Perox isomes are cellular organelles that contain a variety of enzymes, but especially those in volved in fatty acid beta-oxidation. Lack of these systems can lead to multiple functional deficiencies since oxidation of cholesterol, biosynthesis of cholesterol and other lipids and dolichols, all depend on peroxisome-localized enzymes. Hypolipidemic drugs, leukotriene D4 antagonists, some herbicides and pesticides, phthalate esters, various solvents, and the endogenous chemicals, phenylacetate and dehydroepiandosterone, are only some of the many peroxisome proliferators. A nuclear receptor was cloned from mice (peroxisome proliferator receptor or PPAR) and found to be a member of the nuclear receptor superfa mily that includes estrogen, progesterone, thyroid hormone, and other receptors. Three members of the PPAR family, alpha, beta and gamma, have been cloned and appear to have different functions and tissue distribution. PPAR alpha appears to have a role in modulating lipid catabolism and perhaps lipid synthesis. PP AR alpha activates gene ex pression through binding to a response element (PPRE), and it interacts with other mem bers of the nuclear receptor superfamily. Peroxisome proliferators may lead to hepatocellular carcinoma in rats by increasing intracellular hydrogen peroxide, by damag ing cytoplasmic mitochondrial DNA, or by inhibiting apoptosis. Mice lacking the PPAR alpha receptor were produced and showed no apparent gross phenotypic abnormalities. In addition, they showed no response to peroxisome proliferators such as clofibrate or dehy droepiandrosterone sulfate, but they did have an altered lipid metabolism. These null mice are being used to investigate species and other differences in response to peroxisome· pro liferators. The complexity of the PPAR activation pathway has been enhanced by finding that PPAR DNA binding is linked to heterodimerization with a member of the retinoid X (RXR) family of receptors. In addition, the PPAR/farnesol activation pathway converges at some points with another steroid receptor orphan family member, the farnesoid X acti vated receptor (FXR). The data suggest that farnesol is a common intermediate for endo genous activators of both PPAR alpha and FXR and that FXR can be integrated into the PPAR alpha-mediated oxidative stress hypothesis. "Dietary Fat and Gene Expression," the next session, provided more information on the functions of PPAR and related receptors. Several genes expressed in adipose cells, such as that for adipocyte lipid-binding protein (aP2) and phosphoenolpyruvate carboxyki nase have binding sites for PPAR/RXR heterodimers. These intracellular aP2s control ac cessibility of the substrates and are negative elements in polyunsaturated fatty acid control of gene expression. viii Preface In discussing dietary fatty acids, the short chain fatty acids are often disregarded, but acetate, propionate, and butyrate have important biological and clinical effects in the nor mal and diseased colon. Butyrate, especially, regulates expression of growth-related genes, such as p53, c-fos, thymidine kinase, and c- myc. Expression of c-myc is correlated with cellular proliferation and inversely with cellular differentiation. Butyrate acts rapidly on c-myc, presumably through induction of a protein that decreases c-myc. Butyrate also induces apoptosis in several colon and breast carcinoma cell lines. It inhibits the growth of the colon carcinoma cells in the early G I phase of the cell cycle. Although mammals are the organisms of interest with respect to PP AR, peroxisome proliferation also occurs in yeast, where levels of peroxisomal beta-oxidation enzymes are regulated by the available carbon source. Expression of the genes encoding the enzymes occurs in the presence of glucose and activation occurs when a fatty acid such as oleate is supplied for growth. The rate-limiting enzyme in the peroxisomal beta-oxidation cycle is POX! (for peroxisomal acyl-CoA oxidase); an activating sequence required for oleate specific activation of POX 1 was identified. Disrupting this gene in the yeast led to cells which did not grow in the presence of oleic acid. An overview on the metabolism of fats, derivation of energy and genetic control summarized the situation. Dietary fat regulates gene expression through multiple path ways, thus causing changes in carbohydrate and lipid metabolism. Polyunsaturated fatty acid (PUF A) regulatory factor (PUF A-RF) was not PPAR, although PPAR apparently is involved in one mechanism for fatty acid regulation. This appears to be transcription of S 14 gene in liver where it acts by sequestering RXR. PUF A can have either a beneficial action as in the n-3 PUF A suppression of serum triglycerides or a detrimental one as in the saturated and n-6 PUF A promotion of insulin resistance. The final session "Future Directions and Implications of Research on Dietary Fat and Genetics" afforded a panel of experts the opportunity to present their individual views on this matter. The role of body fat distribution and genetic predisposition in relation to breast cancer was mentioned. In addition the relative risk was fairly high ( 4.8) for a rela tionship between obesity and both breast and ovarian cancer, versus a risk of 2.1 for breast cancer alone and a relative risk of 1.1 for women with no family history of breast or ovar ian cancer. In animal studies dietary fat definitely influences the outcome of various car cinogenicity studies, but molecular studies may not always provide a rationale for the observed effects. Although the evidence for the role of specific genes in human cancer is growing, some experts consider that environmental factors are still the most important determinant of cancer risk. Studies of populations with certain cancer susceptibilities may provide more definitive human data. Integrative studies on nutrition and cancer, the time in life when exposure is important, and epidemiologic studies that assess cancer genetics using molecular biology techniques were all considered necessary. There is general interest in any relationship between body shape and risk of breast or ovarian cancer, as well as the difference in function of body fat from different anatomical sites. Besides the scientific sessions, there was a special evening workshop on "Diet, Nu trition and Cancer Prevention: Research Opportunities, Approaches and Pitfalls," directed toward obtaining funding and the interactions with funding agencies. There were 57 poster abstracts presented with participants from eight countries be sides the United States, confirming the international interest in research in the diet/cancer field. Thus, although the epidemiologic evidence is not always definitive, it does hint to ward an association between dietary fat and cancer incidence. Fat has an important role in Preface ix the diet, but the type and quantity consumed can interact with the genetic background of the individual to increase the risk of disease. There is a need for most people in the afflu ent world to reduce the amount of dietary fat. Educational efforts toward that end are most appropriate. The Editors CONTENTS Chapter 1 Fat and Cancer: The Epidemiologic Evidence in Perspective Laurence N. Kolonel Classification of Fat in Epidemiologic Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Plausibility of the Fat-Cancer Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Some Issues Related to Epidemiologic Studies of Fat and Cancer . . . . . . . . . . . . . . 3 Epidemiologic Associations of Dietary Fat and Cancer . . . . . . . . . . . . . . . . . . . . . . . 4 Colorectal Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Breast Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Prostate Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Lung Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II Other Cancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Conclusions and Implications for Public Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Chapter 2 Dietary Lipids and the Cancer Cascade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Steven K. Clinton Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 The Genetic Basis of Cancer Predisposition and Susceptibility . . . . . . . . . . . . . . . . 23 Cellular Proliferation, Apoptosis, and Immortality . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Angiogenesis and Metastasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 The Relationship between Dietary Lipids, Energy Intake, and Cancer in Experimental Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Future Directions: Dietary Lipids and the Cancer Cascade . . . . . . . . . . . . . . . . . . . . 32 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Chapter 3 Molecular Studies on the Role of Dietary Fat and Cholesterol in Breast Cancer Induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Michael C. Archer, Ahmed El-Sohemy, Laurie L. Stephen, and Alaa F. Badawi Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39