Calorie restriction suppresses subgenomic mink cytopathic focus-forming murine leukemia virus transcription and frequency of genomic expression while impairing lymphoma formation

The Role of Diet in Cancer Prevention and Chemotherapy Efficacy

Despite great advances in treatment, cancer remains a leading cause of death worldwide. Diet can greatly impact health, while caloric restriction and fasting have putative benefits for disease prevention and longevity. Strong epidemiological associations exist between obesity and cancer, whereas healthy diets can reduce cancer risk. However, less is known about how diet might impact cancer once it has been diagnosed and particularly how diet can impact cancer treatment. In the present review, we discuss the links between obesity, diet, and cancer. We explore potential mechanisms by which diet can improve cancer outcomes, including through hormonal, metabolic, and immune/inflammatory effects, and present the limited clinical research that has been published in this arena. Though data are sparse, diet intervention may reduce toxicity, improve chemotherapy efficacy, and lower the risk of long-term complications in cancer patients. Thus, it is important that we understand and expand the science of this important but complex adjunctive cancer treatment strategy.

Perinatal diet influences health and survival in a mouse model of leukemia

The goal of the current study was to determine the role of maternal diet in the perinatal period on the health and survival of the offspring. AKR/J mice, a model described to be susceptible to leukemia development, was used where females were maintained on either standard diet (SD), high sucrose diet, Western diet, or calorie restriction (CR) as they were mated with SD-fed males. Body weights, pregnancy rates, litter size, and litter survival were used as markers of successful pregnancy and pup health. Data indicated that maternal diet had significant effects on litter size, early pup survival, and early pup body weights. As pups matured, the makeup of their respective maternal diet was a predictor of adult metabolic health and survival. Overall, these results suggest that perinatal maternal diet is an important determinant of the health and survival of the offspring and that these effects continue well into adulthood, strongly correlating with lifespan.

Fasting and cancer: molecular mechanisms and clinical application

The vulnerability of cancer cells to nutrient deprivation and their dependency on specific metabolites are emerging hallmarks of cancer. Fasting or fasting-mimicking diets (FMDs) lead to wide alterations in growth factors and in metabolite levels, generating environments that can reduce the capability of cancer cells to adapt and survive and thus improving the effects of cancer therapies. In addition, fasting or FMDs increase resistance to chemotherapy in normal but not cancer cells and promote regeneration in normal tissues, which could help prevent detrimental and potentially life-threatening side effects of treatments. While fasting is hardly tolerated by patients, both animal and clinical studies show that cycles of low-calorie FMDs are feasible and overall safe. Several clinical trials evaluating the effect of fasting or FMDs on treatment-emergent adverse events and on efficacy outcomes are ongoing. We propose that the combination of FMDs with chemotherapy, immunotherapy or other treatments represents a potentially promising strategy to increase treatment efficacy, prevent resistance acquisition and reduce side effects.

The role of adipose tissue and obesity in causing treatment resistance of acute lymphoblastic leukemia

Obesity is responsible for ~90,000 cancer deaths/year, increasing cancer incidence and impairing its treatment. Obesity has also been shown to impact hematological malignancies, through as yet unknown mechanisms. Adipocytes are present in bone marrow and the microenvironments of many types of cancer, and have been found to promote cancer cell survival. In this review, we explore several ways in which obesity might cause leukemia treatment resistance. Obese patients may be at a treatment disadvantage due to altered pharmacokinetics of chemotherapy and dosage "capping" based on ideal body weight. The adipose tissue provides fuel to cancer cells in the form of amino acids and free fatty acids. Adipocytes have been shown to cause cancer cells to resist chemotherapy-induced apoptosis. In addition, obese adipose tissue is phenotypically altered, producing a milieu of pro-inflammatory adipokines and cytokines, some of which have been linked to cancer progression. Given the prevalence of obesity, understanding its role and adipose tissue in acute lymphoblastic leukemia treatment is necessary for evaluating current treatment regimen and revealing new therapeutic targets.

Diet-induced obesity accelerates acute lymphoblastic leukemia progression in two murine models

Obesity is associated with an increased incidence of many cancers, including leukemia, although it is unknown whether leukemia incidence is increased directly by obesity or rather by associated genetic, lifestyle, health, or socioeconomic factors. We developed animal models of obesity and leukemia to test whether obesity could directly accelerate acute lymphoblastic leukemia (ALL) using BCR/ABL transgenic and AKR/J mice weaned onto a high-fat diet. Mice were observed until development of progressive ALL. Although obese and control BCR/ABL mice had similar median survival, older obese mice had accelerated ALL onset, implying a time-dependent effect of obesity on ALL. Obese AKR mice developed ALL significantly earlier than controls. The effect of obesity was not explained by WBC count, thymus/spleen weight, or ALL phenotype. However, obese AKR mice had higher leptin, insulin, and interleukin-6 levels than controls, and these obesity-related hormones all have potential roles in leukemia pathogenesis. In conclusion, obesity directly accelerates presentation of ALL, likely by increasing the risk of an early event in leukemogenesis. This is the first study to show that obesity can directly accelerate the progression of ALL. Thus, the observed associations between obesity and leukemia incidence are likely to be directly related to biological effects of obesity.

Combination of physical activity, nutrition, or other metabolic factors and vaccine response

A number of lifestyle factors that reduce cancer risk in the primary prevention setting may be potential new targets for use in combination with cancer vaccines. This review discusses the modulation of energy balance (physical activity, calorie restriction, and obesity prevention), and the supplementation with natural and synthetic analogs of vitamins A and E, as potential interventions for use in combination with cancer vaccines. Additionally, the pharmacologic manipulation of nutrient metabolism in the tumor microenvironment (e.g., arachidonic acid, arginine, tryptophan, and glucose metabolism) is discussed. This review includes a brief overview of the role of each agent in primary cancer prevention; outlines the effects of these agents on immune function, specifically adaptive and/or anti-tumor immune mechanisms, when known; and discusses the potential use of these interventions in combination with therapeutic cancer vaccines. Modulation of energy balance through exercise and strategies targeting nutrient metabolism in the tumor microenvironment represent the most promising interventions to partner with therapeutic cancer vaccines. Additionally, the use of vitamin E succinate and the retinoid X receptor-directed rexinoids in combination with cancer vaccines offer promise. In summary, a number of energy balance- and nutrition-related interventions are viable candidates for further study in combination with cancer vaccines.

Lifestyle and nutrition, caloric restriction, mitochondrial health and hormones: scientific interventions for anti-aging

Aging is a universal process to all life forms. The most current and widely accepted definition for aging in humans is that there is a progressive loss of function and energy production that is accompanied by decreasing fertility and increasing mortality with advancing age. The most obvious and commonly recognised consequence of aging and energy decline is a decrease in skeletal muscle function which affects every aspect of human life from the ability to play games, walk and run to chew, swallow and digest food. There is hence a recognised overall decline of an individuals' fitness for the environment that they occupy. In Westenised countries this decline is gradual and the signs become mostly noticeable after the 5th decade of life and henceforth, where the individual slowly progresses to death over the next three to four decades. Given that the aging process is slow and gradual, it presents with opportunities and options that may ameliorate and improve the overall functional capacity of the organism. Small changes in function may be more amenable and likely to further slow down and possibly reverse some of the deleterious effects of aging, rather, than when the incremental changes are large. This overall effect may then translate into a significant compression of the deleterious aspects of human aging with a resultant increase in human life expectancy.

Age-dependent differences in the efficacy of cancer immunotherapy in C57BL and AKR mouse strains

While tumor incidence increases with age, tumor growth and metastasis often proceed at a slower rate in aged organisms. The mechanisms underlying this age-related reduced tumor development may suggest therapeutic modalities appropriate for the aged. Decreased tumor aggressiveness in the old was shown to be related to altered immune response. Consequently, the aim of the present study was to assess whether cancer immunotherapy has an age-dependent effect. Only a few studies have compared cancer immunotherapy efficiency as a function of age, most showing lower inhibition in older animals. In the present study, we tested the effect of two immunomodulators, levamisole and BCG, on two tumors, B16 melanoma and AKR lymphoma, in mice of different ages. We demonstrated a higher efficiency of immunotherapy in aged as compared to young mice, particularly at low immunomodulator doses. While decreased T cell function during aging is apparently established, nonspecific immunity is more preserved or even enhanced in later life. We found an increased number of macrophages in tumors of old compared to young mice and an increase in MAC-1+ cells in old levamisole-treated compared to non-treated mice. The stronger therapeutic effect of this immunomodulator in old mice might thus be due to an increased macrophage-mediated anti-tumoral effect.

Microarray profiling of gene expression in aging and its alteration by caloric restriction in mice

An active research area in biological gerontology concerns the mechanisms by which caloric restriction (CR) retards the aging process in laboratory rodents. We used high density oligonucleotide arrays representing 6347 genes to determine the gene expression profile of the aging process in gastrocnemius muscle of male C57BL/6 mice. Aging resulted in a differential gene expression pattern indicative of a marked stress response and lower expression of metabolic and biosynthetic genes. Most alterations were completely or partially prevented by CR. Transcriptional patterns of muscle from calorie-restricted animals suggest that CR retards the aging process by causing a metabolic shift toward increased protein turnover and decreased macromolecular damage. The use of high density oligonucleotide microarrays provides a new tool to measure biological age on a tissue-specific basis and to evaluate at the molecular level the efficacy of nutritional interventions designed to retard the aging process.

Evaluating mutant mice: anatomic pathology

As the human and mouse genome projects approach their goals, initiatives in functional genomics are advancing. When the nucleotide sequences are available, identification of gene functions will assume even greater importance. Determination of gene products and their proximal biochemical functions provide a part of the picture, but determination of their functions in the context of the whole organism is the ultimate goal. The manipulated mouse genome has become accepted as a model for understanding the genetic basis of human conditions and diseases. Consequently, biomedical research institutions have seen significant increases in the use of mice since the early 1980s, and these increases are largely attributable to the use of genetically modified mice. The role of comparative pathology in research on mutant mouse models of disease is increasing in response to these trends. Evaluation and phenotypic characterization of mutant mice, via clinical and anatomic pathology techniques, will be an important component of functional genomics initiatives.

The influence of restricted calorie intake on peritoneal macrophage function

Malnutrition leads to immune dysfunction with greatly increased morbidity. However, restrictive dietary regimens are also known to preserve immune function in autoimmune-susceptible mice. The macrophage (Mø) is central to both immune effector and autoregulatory functions and is critical to host-defense mechanisms. The aim of this study was to investigate the effect of calorie restriction on Mø functions in mice. Female, 6- to 8-wk-old, Swiss Webster mice were randomized to ad libitum feeding for 7 or 21 d (n = 10 mice/group), restricted feeding (13.5 to 14.0 g/cage/d; n = 10) for 7 d, or restricted feeding (16.5 to 17.0 g/cage/d; n = 10) for 21 d. These restrictions were equivalent to a decrease in calorie intake of 21.9% and 5.1%, respectively, over 7 and 21 d. All mice were allowed free access to water. On days 8 and 22, respectively, the mice were killed, and peritoneal Møs were isolated by lavage and adhered to 96-well polystyrene tissue-culture-treated plates. After stimulation with lipopolysaccharide, supernatant prostaglandin E2 and interleukin-6 levels were measured by enzyme-linked immunosorbent assay. Supernatant NO2- in response to stimulation with lipopolysaccharide and interferon-gamma was determined by the Greiss reaction. Prostaglandin E2 production was significantly elevated in peritoneal Møs from the calorie-restricted mice compared with the ad-libitum-fed mice after 7 d. After 21 d, production of both prostaglandin E2 and nitric oxide was significantly increased (P < 0.05) in peritoneal Møs from the restricted mice compared with the ad-libitum-fed mice. These results indicate that calorie restriction influences immune function by altering prostaglandin E2 and nitric oxide generation by Møs.

Reflections on scrapie and related disorders, with consideration of the possibility of a viral aetiology

The transmissible spongiform encephalopathies of domesticated animals, scrapie in sheep and bovine spongiform encephalopathy (BSE), and transmissible mink encephalopathy are more than a scientific curiosity; under certain circumstances their impact on commercial activities can be calamitous. Knowledge of their causation and pathogenesis is still rudimentary, but many consider than an unconventional agent, the prion (a brain protein, PrP), that is not associated with nucleic acid is involved in both. Others believe that conventional viruses, which replicate by virtue of their nucleic acid-defined genes, are involved in the causation and progression of the encephalopathies but that technical problems have prevented their identification. Others postulate even more exotic causative agents. While this paper will particularly address the possibility of a viral aetiology for these diseases, it is also emphasized that our knowledge of the state of the immune system in animals with encephalopathy needs broadening. There are remarkable gaps in our knowledge of the histopathology of these diseases, particularly the nature of the characteristic vacuoles. Much further work is needed on the biochemical changes in the brain and the serum, particularly of the latter as it could lead to an additional means of recognizing clinical cases without waiting for the animal to die with subsequent examination of the brain for characteristic lesions and the presence of protease-K-resistant PrP.

Influence of calorie restriction on oncogene expression and DNA synthesis during liver regeneration

Controlling calorie intake (CCI) extends healthful life-span by a mechanism that may involve reduced rates of cell division without detriment to inducible cellular responses. To test whether inducible cellular proliferation is preserved by CCI and whether the mRNA expression levels of oncogenes activated by cell division can be reduced by CCI, we evaluated the effect of dietary energy on the hepatocellular proliferative burst and on oncogene and growth factor mRNA expression induced by partial hepatectomy. Eighty Fischer 344 rats were separated into two dietary groups and were fed semipurified diets for 10 weeks that differed only in calories by 40%. Mean hepatic levels of [3H]thymidine incorporation were greater among CCI animals at 18, 24, 28, and 36 hr after partial hepatectomy. The expression of c-fos and c-Ki-ras mRNAs, activated during hepatic regeneration, was reduced by CCI. Peak expression of c-fos among ad libitum fed controls to levels 4-6 times greater than prehepatectomy levels was not detected among CCI animals. Protracted elevated expression of c-Ki-ras among ad libitum fed animals was foreshortened by CCI. These findings demonstrate that inducible cellular proliferative responses are preserved by CCI and that the mRNA expression levels of c-fos and c-Ki-ras activated during cell division are reduced by controlling dietary energy. Preserved inducible cellular responses and lowered oncogene expression during cell division may be attributes of the healthful protective effect of CCI.