Early Exposure to a High Fat/High Sugar Diet Increases the Mammary Stem Cell Compartment and Mammary Tumor Risk in Female Mice

Nutrition and Dietary Intervention in Cancer: Gaps, Challenges, and Future Perspectives

The term "cancer" refers to the state in which cells in the body develop mutations and lose control over their replication. Malignant cancerous cells invade in various other tissue sites of the body. Chemotherapy, radiation, and surgery are the first-line modalities for the majority of solid cancers. These treatments work by mitigating the DNA damage of cancerous cells, but they can also cause harm to healthy cells. These side effects might be immediate or delayed, and they can cause a high rate of morbidity and mortality. Dietary interventions have a profound impact on whole-body metabolism, including immunometabolism and oncometabolism which have been shown to reduce cancer growth, progression, and metastasis in many different solid tumor models with promising outcomes in early phase clinical studies. Dietary interventions can improve oncologic or quality-of-life outcomes for patients that are undergoing chemotherapy or radiotherapy. In this chapter, we will focus on the impact of nutritional deficiencies, several dietary interventions and their proposed mechanisms which are used as a novel therapy in controlling and managing cancers.

Early Dietary Exposures Epigenetically Program Mammary Cancer Susceptibility through Igf1-Mediated Expansion of the Mammary Stem Cell Compartment

Diet is a critical environmental factor affecting breast cancer risk, and recent evidence shows that dietary exposures during early development can affect lifetime mammary cancer susceptibility. To elucidate the underlying mechanisms, we used our established crossover feeding mouse model, where exposure to a high-fat and high-sugar (HFHS) diet during defined developmental windows determines mammary tumor incidence and latency in carcinogen-treated mice. Mammary tumor incidence is significantly increased in mice receiving a HFHS post-weaning diet (high-tumor mice, HT) compared to those receiving a HFHS diet during gestation (low-tumor mice, LT). The current study revealed that the mammary stem cell (MaSC) population was significantly increased in mammary glands from HT compared to LT mice. Igf1 expression was increased in mammary stromal cells from HT mice, where it promoted MaSC self-renewal. The increased Igf1 expression was induced by DNA hypomethylation of the Igf1 Pr1 promoter, mediated by a decrease in Dnmt3b levels. Mammary tissues from HT mice also had reduced levels of Igfbp5, leading to increased bioavailability of tissue Igf1. This study provides novel insights into how early dietary exposures program mammary cancer risk, demonstrating that effective dietary intervention can reduce mammary cancer incidence.

Maternal Low-Protein Diet Deregulates DNA Repair and DNA Replication Pathways in Female Offspring Mammary Gland Leading to Increased Chemically Induced Rat Carcinogenesis in Adulthood

Studies have shown that maternal malnutrition, especially a low-protein diet (LPD), plays a key role in the developmental mechanisms underlying mammary cancer programming in female offspring. However, the molecular pathways associated with this higher susceptibility are still poorly understood. Thus, this study investigated the adverse effects of gestational and lactational low protein intake on gene expression of key pathways involved in mammary tumor initiation after a single dose of N-methyl-N-nitrosourea (MNU) in female offspring rats. Pregnant Sprague-Dawley rats were fed a normal-protein diet (NPD) (17% protein) or LPD (6% protein) from gestational day 1 to postnatal day (PND) 21. After weaning (PND 21), female offspring (n = 5, each diet) were euthanized for histological analysis or received NPD (n = 56 each diet). At PND 28 or 35, female offspring received a single dose of MNU (25 mg/kg body weight) (n = 28 each diet/timepoint). After 24 h, some females (n = 10 each diet/timepoint) were euthanized for histological, immunohistochemical, and molecular analyses at PDN 29 or 36. The remaining animals (n = 18 each diet/timepoint) were euthanized when tumors reached ≥2 cm or at PND 250. Besides the mammary gland development delay observed in LPD 21 and 28 groups, the gene expression profile demonstrated that maternal LPD deregulated 21 genes related to DNA repair and DNA replication pathways in the mammary gland of LPD 35 group after MNU. We further confirmed an increased γ-H2AX (DNA damage biomarker) and in ER-α immunoreactivity in mammary epithelial cells in the LPD group at PND 36. Furthermore, these early postnatal events were followed by significantly higher mammary carcinogenesis susceptibility in offspring at adulthood. Thus, the results indicate that maternal LPD influenced the programming of chemically induced mammary carcinogenesis in female offspring through increase in DNA damage and deregulation of DNA repair and DNA replication pathways. Also, Cidea upregulation gene in the LPD 35 group may suggest that maternal LPD could deregulate genes possibly leading to increased risk of mammary cancer development and/or poor prognosis. These findings increase the body of evidence of early-transcriptional mammary gland changes influenced by maternal LPD, resulting in differential response to breast tumor initiation and susceptibility and may raise discussions about lifelong prevention of breast cancer risk.

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species

In mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction.

Dietary Choices Modulate Colorectal Cancer Stem Cells: A Role of FXR Nuclear Receptor

Intra- and inter-tumor heterogeneity (TMH) among colorectal cancer patients is considered as major hurdles to develop precise, potent, and personalized cancer therapeutics. The discernible factors that contribute to the existence of TMH and associated problems are suggested as genetic, molecular, epigenetic, and environmental pressures including shifts in trend from high-fiber diet to high-fat/processed sugar diet. In essence, components of high fat/processed sugar diet potentiate metabolic re-programing of inherent cellular heterogeneity of cancer stem cells (CSCs) by genetic and epigenetic pathways intersected by the farnesoid X receptor (FXR) nuclear receptor. Therefore, choices of dietary components shape up protumor or antitumor microenvironment by the modulation of FXR regulated transcriptional and epigenetic events in CSCs. In this article, we highlight the major understanding emanated from preclinical and clinical studies that indicate the potential contribution of high fiber/saturated sugar diet toward carcinogenesis of colorectal cancer.

Weighing the Risk: effects of Obesity on the Mammary Gland and Breast Cancer Risk

Obesity is a preventable risk factor for breast cancer following menopause. Regardless of menopausal status, obese women who develop breast cancer have a worsened prognosis. Breast tissue is comprised of mammary epithelial cells organized into ducts and lobules and surrounded by adipose-rich connective tissue. Studies utilizing multiple in vivo models of obesity as well as human breast tissue have contributed to our understanding of how obesity alters mammary tissue. Localized changes in mammary epithelial cell populations, elevated secretion of adipokines and angiogenic mediators, inflammation within mammary adipose tissue, and remodeling of the extracellular matrix may result in an environment conducive to breast cancer growth. Despite these significant alterations caused by obesity within breast tissue, studies have suggested that some, but not all, obesity-induced changes may be mitigated with weight loss. Here, we review our current understanding regarding the impact of obesity on the breast microenvironment, how obesity-induced changes may contribute to breast tumor progression, and the impact of weight loss on the breast microenvironment.

Life style factors, tumor cell plasticity and cancer stem cells

Cancers are heterogeneous tissues and a layer of heterogeneity is determined by the presence of cells showing stemness traits, known as cancer stem cells (CSCs). Evidence indicates that CSCs are important players in tumor development, progression and relapse. Oncogenic transformation of normal stem cells can give rise to CSCs, but CSCs can also originate from de-differentiation of bulk tumor cells. Thus, factors promoting the increase of normal stem cell pools or stimulating the acquisition of stemness features by tumor cells can have serious consequences on cancer origin and progression. In this review, we will first give an overview of the CSC model of cancer development and we will then discuss the role of life style factors, such as high caloric diet, alcohol drinking and smoking, on the widening of stem cell pools and the induction of CSC features in tumors. Finally, we will discuss some healthy life style factors that can help to prevent cancer.

Fetal Alcohol Exposure Alters Mammary Epithelial Cell Subpopulations and Promotes Tumorigenesis

BACKGROUND

Fetal alcohol exposure (FAE) increases the risk of mammary tumorigenesis in adult offspring; however, the underlying mechanism remains unknown. This study tested the hypothesis that FAE shifts the mammary epithelial cell (MEC) composition toward one that promotes tumorigenesis.

METHODS

Pregnant Friend Virus B NIH Jackson dams bred to MMTV-Wnt1 male mice were given ad libitum access to 5% alcohol in 0.2% saccharin solution from GD9-10 and 10% alcohol in 0.2% saccharin from GD11-GD19 or 0.2% saccharin solution from GD9-GD19. Thoracic and inguinal mammary glands from wild-type (WT) and transgenic (Tg) female offspring were harvested at 5 and 10 weeks of age and dissociated to yield a single cell suspension enriched for MECs for flow cytometry, mammosphere assay, and gene analysis. A subset of Tg offspring was followed for tumor formation.

RESULTS

WT glands of FAE animals exhibited a decreased basal cell population and increased luminal: basal ratio at 10 weeks of age. qRT-PCR analysis of total MECs found that Hey1 mRNA expression was increased in the WT FAE group at 10 weeks of age. In Tg glands, FAE increased the luminal progenitor cell population at 5 weeks of age but did not alter MEC composition at 10 weeks of age. Tertiary mammosphere-forming efficiency was greater in the WT glands of FAE animals at 10 weeks of age. Tumor latency was decreased in the FAE group. Flow cytometry analysis indicated that FAE females developed tumors with an increased basal cell population.

CONCLUSIONS

These data indicate that FAE can shift MEC subpopulations, increasing the proportion of cells that are potentially vulnerable to transformation and affecting cancer risk.

Dietary patterns and cancer risk

Over the past decade, the search for dietary factors on which to base cancer prevention guidelines has led to the rapid expansion of the field of dietary patterns and cancer. Multiple systematic reviews and meta-analyses have reported epidemiological associations between specific cancer types and both data-driven dietary patterns determined by empirical analyses and investigator-defined dietary indexes based on a predetermined set of dietary components. New developments, such as the use of metabolomics to identify objective biomarkers of dietary patterns and novel statistical techniques, could provide further insights into the links between diet and cancer risk. Although animal models of dietary patterns are limited, progress in this area could identify the potential mechanisms underlying the disease-specific associations observed in epidemiological studies. In this Review, we summarize the current state of the field, provide a critical appraisal of new developments and identify priority areas for future research. An underlying theme that emerges is that the effectiveness of different dietary pattern recommendations in reducing risk could depend on the type of cancer or on other risk factors such as family history, sex, age and other lifestyle factors or comorbidities as well as on metabolomic signatures or gut microbiota profiles.

Puberty is a critical window for the impact of diet on mammary gland development in the rabbit

Background

Nutritional changes can affect future lactation efficiency. In a rabbit model, an obesogenic diet initiated before puberty and pursued throughout pregnancy enhances mammary differentiation, but when started during the neonatal period can cause abnormal mammary development in early pregnancy. The aim of this study was to investigate the impact of an unbalanced diet administered during the pubertal period only.

Results

Consuming an obesogenic diet at puberty did not affect either metabolic parameters or certain maternal reproductive parameters at the onset of adulthood. In contrast, at Day 8 of pregnancy, epithelial tissue showed a lower proliferation rate in obesogenic‐diet fed rabbits than in control‐diet fed rabbits. Wap and Cx26 genes, mammary epithelial cell differentiation markers, were upregulated although Wap protein level remained unchanged. However, the expression of genes involved in lipid metabolism and in alveolar formation was not modified.

Conclusion

Taken together, our results demonstrate that the consumption for 5 weeks of an obesogenic diet during the pubertal period initiates mammary structure modifications and affects mammary epithelial cell proliferation and differentiation. Our findings highlight the potentially important role played by unbalanced nutrition during critical early‐life windows in terms of regulating mammary epithelial cell differentiation and subsequent function in adulthood.

Our results demonstrate that the consumption for five weeks of an obesogenic diet during the pubertal period initiates mammary structure modifications and affects mammary epithelial cell proliferation and differentiation. Our findings highlight the potentially important role played by unbalanced nutrition during critical early‐life windows in terms of regulating mammary epithelial cell differentiation and subsequent function in adulthood.

Maternal western-style diet enhances the effects of chemically-induced mammary tumors in female rat offspring through transcriptome changes

Previous studies have shown that early life intake of high-fat diet or western-style diet (WD) enhances the development of mammary tumors in adult female rats. Thus, we hypothesized that maternal WD throughout pregnancy and the lactation period could speed up the development of MNU-induced mammary tumors and alter their gene expression. For this, the present study investigated the gene expression profile of chemically-induced mammary tumors in female rat offspring from dams fed a WD or a control diet. Pregnant female Sprague-Dawley rats received a WD (high-fat, low-fiber and oligoelements) or a control diet from gestational day 12 until post-natal day (PND) 21. At PND 21, female offspring received a single dose of N-Methyl-N-Nitrosourea (MNU, 50 mg/kg body weight) and were fed a control diet for 13 weeks. Tumor incidence, multiplicity, and latency were recorded and mammary gland samples were collected for histopathology and gene expression analysis. Tumor multiplicity and histological grade were significantly higher and tumor latency was lower in WD offspring compared to control offspring. Transcriptome profiling identified 57 differentially expressed genes in tumors from WD offspring as compared to control offspring. There was also an increase in mRNA expression of genes such as Emp3, Ccl7, Ets1, Abcc5, and Cyr61, indicative of more aggressive disease detected in tumors from WD offspring. Thus, maternal WD diet increased MNU-induced mammary carcinogenesis in adult female offspring through transcriptome changes that resulted in a more aggressive disease.