Natural Products for Cancer Prevention and Interception: Preclinical and Clinical Studies and Funding Opportunities

Multiple agents derived from natural products (NPs) have been evaluated for cancer prevention and interception, either alone or in combination. The National Cancer Institute (NCI) is very interested in advancing research to identify additional agents that, alone or in combination, may prove useful in cancer prevention. Below, we provide an overview of NP studies in cancer prevention and interception, both individual agents and combination interventions. Given that findings from many preclinical studies evaluating individual agents have generally not been confirmed in human studies, our focus with individual NPs in this review is on studies involving humans, especially clinical trials. Fewer combination intervention studies have been conducted, so we have broadened our review to include preclinical studies. We conclude with how the Division of Cancer Prevention (DCP) within the NCI is providing funding to encourage the research community to propose natural product studies in cancer prevention and interception to advance the field.

Obesity, metabolic and bariatric surgery, and cancer prevention: what do we need to learn and how do we get there?

Obesity and associated metabolic dysfunction are on the rise in the United States and around the world. Metabolic dysfunction often leads to chronic disease, including cancer. Recent evidence suggests that weight loss among individuals with obesity may decrease cancer risk. Metabolic and bariatric surgery (MBS) leads to greater maximum and sustained weight loss than nonsurgical dietary strategies and demonstrates the most convincing evidence that weight loss lowers cancer risk. Caloric restriction diets combined with GLP-1 receptor agonists demonstrate weight loss intermediate between MBS and other nonsurgical diet strategies so long as individuals consistently take the medication. Weight regain after initial loss is a major problem with all weight loss strategies. To better prevent cancer in individuals with obesity, we need to individualize weight loss strategies, determining what strategy works for a given individual and how to implement it. We need to learn (1) what an individual's impediments to initial and sustained weight loss are; (2) what the optimal weight loss strategy, be it diet modification, diet modification + medication, or MBS followed by diet modification, is; (3) how exercise(s) should be incorporated into weight loss strategies; (4) where medications fit into the treatment strategy of individuals with obesity; and (5) what the mechanisms driving the influence of MBS on cancer risk are. We also need to (6) explore expanding the eligibility of MBS to individuals with a body mass index <35 kg/m2. Answers to these questions require a better understanding of how MBS impacts cancer risk, including in which groups (women versus men, which racial and ethnic groups, which cancers, which MBS procedure) MBS works best to reduce risk. The National Cancer Institute, through new funding opportunities, hopes to advance our understanding of how obesity drives cancer risk and how individuals with obesity can prevent cancer development and, among those with cancer, prevent disease recurrence.

Role of FABP5 in T Cell Lipid Metabolism and Function in the Tumor Microenvironment

To evade immune surveillance, tumors develop a hostile microenvironment that inhibits anti-tumor immunity. Recent immunotherapy breakthroughs that target the reinvigoration of tumor-infiltrating T lymphocytes (TIL) have led to unprecedented success in treating some cancers that are resistant to conventional therapy, suggesting that T cells play a pivotal role in anti-tumor immunity. In the hostile tumor microenvironment (TME), activated T cells are known to mainly rely on aerobic glycolysis to facilitate their proliferation and anti-tumor function. However, TILs usually exhibit an exhausted phenotype and impaired anti-tumor activity due to the limited availability of key nutrients (e.g., glucose) in the TME. Given that different T cell subsets have unique metabolic pathways which determine their effector function, this review introduces our current understanding of T cell development, activation signals and metabolic pathways. Moreover, emerging evidence suggests that fatty acid binding protein 5 (FABP5) expression in T cells regulates T cell lipid metabolism and function. We highlight how FABP5 regulates fatty acid uptake and oxidation, thus shaping the survival and function of different T cell subsets in the TME.

Lessons from the Failure to Complete a Trial of Denosumab in Women With a Pathogenic BRCA1/2 Variant Scheduling Risk-Reducing Salpingo-Oophorectomy

Female carriers of pathogenic/likely pathogenic (P/LP) BRCA1/2 variants are at increased risk of developing breast and ovarian cancer. Currently, the only effective strategy for ovarian cancer risk reduction is risk-reducing bilateral salpingo-oophorectomy (RR-BSO), which carries adverse effects related to early menopause. There is ongoing investigation of inhibition of the RANK ligand (RANKL) with denosumab as a means of chemoprevention for breast cancer in carriers of BRCA1 P/LP variants. Through the NCI Division of Cancer Prevention (DCP) Early Phase Clinical Trials Prevention Consortia, a presurgical pilot study of denosumab was developed in premenopausal carriers of P/LP BRCA1/2 variants scheduled for RR-BSO with the goal of collecting valuable data on the biologic effects of denosumab on gynecologic tissue. The study was terminated early due to the inability to accrue participants. Challenges which impacted the conduct of this study included a study design with highly selective eligibility criteria and requirements and the COVID-19 pandemic. It is critical to reflect on these issues to enhance the successful completion of future prevention studies in individuals with hereditary cancer syndromes.

Dietary Fats High in Linoleic Acids Impair Antitumor T-cell Responses by Inducing E-FABP-Mediated Mitochondrial Dysfunction

The most recent American Dietary Guidelines (2020-2025) recommend shifting dietary fats from solid saturated fats to unsaturated oils. Dietary oils contain different compositions of unsaturated fatty acids (UFA). Oleic acid (OA) and linoleic acid (LA) are the most common UFA in dietary oils. How individual UFA in oils regulate immune cell function and cancer risk remains unclear. Here we demonstrated that high-fat diets (HFD) rich either in OA or LA induced a similar degree of murine obesity, but the LA-rich HFD specifically promoted mammary tumor growth. LA impaired antitumor T-cell responses by promoting naïve T-cell apoptosis and inhibiting TNFα production. While exogenous OA and LA were taken up by T cells with similar efficacy, only LA induced significant mitochondrial reactive oxygen species production and lipid peroxidation. Importantly, naïve T cells predominantly expressed epidermal fatty acid binding protein (E-FABP), which is central in facilitating LA mitochondrial transport and cardiolipin incorporation. Genetic depletion of E-FABP rescued LA-impaired T-cell responses and suppressed LA-rich HFD-associated mammary tumor growth. Collectively, these data suggest that dietary oils high in LA promote mammary tumors by inducing E-FABP-mediated T-cell dysfunction. SIGNIFICANCE: These findings suggest that modulation of dietary oil composition and inhibition of E-FABP activity may represent novel strategies to enhance T-cell function in the prevention and treatment of obesity-associated cancers.

Metabolic Surgery and Cancer Risk: An Opportunity for Mechanistic Research

Simple Summary

Metabolic (bariatric) surgery (MBS) provides the greatest maximum and sustained weight loss among individuals who are morbidly obese. It is more effective than lifestyle interventions in improving or eliminating type 2 diabetes mellitus (T2DM) and in decreasing cardiovascular (CV) risk. Preclinical studies have been conducted to investigate the mechanisms by which MBS leads to the benefits in T2DM and CV risk. In this review, we describe the emerging evidence that MBS may also impact cancer risk and mortality, and whom may benefit most. We describe the long term involvement and commitment of the National Institutes of Health in obesity research in general and MBS in particular. We outline the need for additional research to understand the mechanism(s) by which MBS may influence cancer, since these mechanism(s) are currently unknown.

Abstract

Metabolic (bariatric) surgery (MBS) is recommended for individuals with a BMI > 40 kg/m² or those with a BMI 35–40 kg/m² who have one or more obesity related comorbidities. MBS leads to greater initial and sustained weight loss than nonsurgical weight loss approaches. MBS provides dramatic improvement in metabolic function, associated with a reduction in type 2 diabetes mellitus and cardiovascular risk. While the number of MBS procedures performed in the U.S. and worldwide continues to increase, they are still only performed on one percent of the affected population. MBS also appears to reduce the risk of certain obesity related cancers, although which cancers are favorably impacted vary by study, who benefits most is uncertain, and the mechanism(s) driving this risk reduction are mostly speculative. The goal of this manuscript is to highlight (1) emerging evidence that MBS influences cancer risk, and that the potential benefit appears to vary based on cancer, gender, surgical procedure, and likely other variables; (2) the role of the NIH in MBS research in T2DM and CV risk for many years, and more recently in cancer; and (3) the opportunity for research to understand the mechanism(s) by which MBS influences cancer. There is evidence that women benefit more from MBS than men, that MBS may actually increase the risk of colorectal cancer in both women and men, and there is speculation that the benefit in cancer risk reduction may vary according to which MBS procedure an individual undergoes. Herein, we review what is currently known, the historical role of government, especially the National Institutes of Health (NIH), in driving this research, and provide suggestions that we believe could lead to a better understanding of whether and how MBS impacts cancer risk, which cancers are impacted either favorably or unfavorably, the role of the NIH and other research agencies, and key questions to address that will help us to move the science forward.

Using Organ Specific and Circulatory Biofluids to Screen Individuals at High Risk for Breast Cancer Presents Unique Challenges and Opportunities

Intraductal assessment of the breast holds the potential to provide useful information regarding breast cancer risk assessment, early diagnosis, and/or response to therapy. Intraductal assessment can be through imaging (ductography), direct visualization (mammary ductoscopy), or evaluation of the intraductal fluid collected. The most common nonradiologic approaches to intraductal assessment that provide intraductal fluid for evaluation include breast nipple aspiration fluid (NAF), spontaneous nipple discharge (SND), mammary ductoscopy, and ductal lavage. The first two approaches are entirely noninvasive while the latter are considered minimally invasive. Nipple aspiration is performed both on women with and without evidence of possible disease in the breast. On the other hand, unilateral SND suggests the presence of a lesion in the incident breast, while bilateral SND is most often physiologic. The focus of the report by Patuleia and colleagues is on challenges, lessons learned, and recommended solutions in the identification of women with increased breast cancer risk who are more likely to develop in situ or invasive breast cancer based on sequential collection and subsequent analysis of biofluids (NAF and serum). The lessons learned that are discussed can also be applied to other types of biofluid studies for cancer early detection and response to treatment.See related article by Patuleia et al., p. 441.

SnapShot: FABP Functions

Fatty acid binding proteins (FABPs) serve as intracellular chaperones for fatty acids and other hydrophobic ligands inside cells. Recent studies have demonstrated new functions of individual members of the FABP family. This Snapshot describes the overall functions of FABPs in health and disease and highlights emerging roles of adipose FABP (A-FABP) and epidermal FABP (E-FABP) in the fields of obesity, chronic inflammation, and cancer development. To view this SnapShot, open or download the PDF.

Perspective: Time-Restricted Eating Compared with Caloric Restriction: Potential Facilitators and Barriers of Long-Term Weight Loss Maintenance

A growing body of literature examines the potential benefits of a time-based diet strategy referred to as time-restricted eating (TRE). TRE, a type of intermittent fasting, restricts the time of eating to a window of 4-12 h/d but allows ad libitum intake during eating windows. Although TRE diets do not overtly attempt to reduce energy intake, preliminary evidence from small studies suggests that TRE can lead to concomitant reduction in total energy, improvements in metabolic health, and weight loss. Unique features of the TRE diet strategy may facilitate adherence and long-term weight loss maintenance. In this Perspective, we explore the potential multilevel (i.e., biological, behavioral, psychosocial, environmental) facilitators and barriers of TRE for long-term weight loss maintenance in comparison with the more commonly used diet strategy, caloric restriction (CR). Compared with CR, TRE may facilitate weight loss maintenance by counteracting physiological adaptations to weight loss (biological), allowing for usual dietary preferences to be maintained (behavioral), preserving executive functioning (psychosocial), and enabling individuals to withstand situational pressures to overeat (environmental). However, TRE may also pose unique barriers to weight loss maintenance, particularly for individuals with poor baseline diet quality, internal or social pressures to eat outside selected windows (e.g., grazers), and competing demands that interfere with the scheduling of eating. Future studies of TRE in free-living individuals should consider the multiple levels of influence impacting long-term adherence and weight loss maintenance. Ultimately, TRE could be one strategy in a toolkit of tailored diet strategies to support metabolic health and weight loss maintenance.

FABP4: A New Player in Obesity-Associated Breast Cancer

Obesity is known to increase breast cancer incidence and mortality, but the underlying mechanisms remain unsolved. Recent studies demonstrate that adipose fatty acid binding protein (FABP4) promotes obesity-associated breast cancer development, thus suggesting FABP4 as a novel player linking obesity and breast cancer risk.

Cancer prevention and treatment using combination therapy with natural compounds

Introduction: Naturally occurring compounds play an essential role in the prevention and treatment of various cancers. There are more than 100 plant and animal based natural compounds currently in clinical use.Areas covered: 1) The importance of natural products combinations in the prevention and treatment of cancer, 2) the need to maximize efficacy while minimizing side effects when using natural product combinations, and 3) specifics related to plant and animal derived natural products, as well as agents derived from natural products. Therapies using natural compounds that have been investigated, their rationale, mechanism of action and findings are reviewed. When the data warrant it, combined interventions that appear to increase efficacy (compared with monotherapy) while minimizing toxicity have been highlighted. Pubmed was used to search for relevant publications.Expert opinion: Combination therapy with natural compounds has the potential to be more effective than single agent therapy. Similar to pharmacologic agents, the goal is to maximize efficacy while mimimizing potential side effects. There is an increasing research focus on the development of agents derived from natural products, with notable successes already achieved from the effort.

Consumption of the Fish Oil High-Fat Diet Uncouples Obesity and Mammary Tumor Growth through Induction of Reactive Oxygen Species in Protumor Macrophages

Obesity is associated with increased risk of many types of cancer and can be induced by various high-fat diets (HFD) from different fat sources. It remains unknown whether fatty acid composition in different HFD influences obesity-associated tumor development. Here we report that consumption of either a cocoa butter or fish oil HFD induced similar obesity in mouse models. While obesity induced by the cocoa butter HFD was associated with accelerated mammary tumor growth, consumption of the fish oil HFD uncoupled obesity from increased mammary tumor growth and exhibited a decrease in protumor macrophages. Compared with fatty acid (FA) components in both HFDs, n-3 FA rich in the fish oil HFD induced significant production of reactive oxygen species (ROS) and macrophage death. Moreover, A-FABP expression in the protumor macrophages facilitated intracellular transportation of n-3 FA and oxidation of mitochondrial FA. A-FABP deficiency diminished n-3 FA-mediated ROS production and macrophage death in vitro and in vivo. Together, our results demonstrate a novel mechanism by which n-3 FA induce ROS-mediated protumor macrophage death in an A-FABP-dependent manner. SIGNIFICANCE: This study provides mechanistic insight into dietary supplementation with fish oil for breast cancer prevention and advances a new concept that not all HFDs leading to obesity are tumorigenic. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/12/2564/F1.large.jpg.

A-FABP and oestrogens are independently involved in the development of breast cancer

We previously reported that postmenopausal obese women exhibit increased levels of circulating adipocyte fatty acid binding protein (A-FABP), which is associated with breast cancer (BC) development. In postmenopause, increased oestrogen levels are reported to be associated with increased BC risk. Herein, we assessed if oestrogens, including oestrone (E1), oestradiol (E2) and oestriol (E3), are associated with A-FABP in the obesity-related BC development. We collected 249 serum samples from women with or without BC and measured serum levels of E1, E2, E3 and A-FABP. Considering all subjects, E1 and E2 but not E3 levels were significantly higher in pre- than in postmenopause individuals. E3 and E1 levels were higher in non-obese than in obese women. When samples were separated by BC status, E2 levels were significantly higher, while E1 and E3 levels were significantly lower in postmenopausal obese than non-obese women without BC. These differences based on body mass index (BMI) were not observed among women with BC. E3 levels were higher in obese women with BC than those without. A-FABP levels were significantly higher in postmenopausal obese women regardless of BC status. In addition, A-FABP was not associated with E1, E2 or E3. Altogether, our data suggest that A-FABP is independently regulated by obesity and menopausal status compared to oestrogens, thus playing a unique role in the development of BC.

Breast Hyperplasias, Risk Signature, and Breast Cancer

We address the dilemma faced by oncologists in administering preventative measures to "at risk" patients diagnosed with atypical and nonatypical hyperplasias due to lack of any molecular means of risk stratification and identifying high-risk subjects. Our study purpose is to investigate a four marker risk signature, MMP-1, CEACAM6, HYAL1, and HEC1, using 440 hyperplastic tissues for identifying high-risk subjects who will benefit from preventative therapies. We assayed the markers by IHC and combined their expression levels to obtain a composite value from 0-10, which we called a "Cancer Risk Score." We demonstrate that the four marker-based risk scores predict subsequent cancer development with an accuracy of 91% and 86% for atypical and nonatypical subjects, respectively. We have established a correlation between risk scores and cancer rates by stratifying the samples into low risk (score ≤ 0.5); intermediate risk (score ≤ 5.4), and high risk (score >5.4) groups using Kaplan-Meier survival analysis. We have evaluated cancer rates at 5, 10, and 15 years. Our results show that the average cancer rates in the first 5 years among low- and intermediate-risk groups were 2% and 15%, respectively. Among high-risk group, the average cancer rates at 5 years were 73% and 34% for atypical and nonatypical subjects, respectively. The molecular risk stratification described here assesses a patient's tumor biology-based risk level as low, intermediate, or high and for making informed treatment decisions. The outcomes of our study in conjunction with the available prophylactic measures could prevent approximately 20%-25% of sporadic breast cancers.

Stearic Acid Induces CD11c Expression in Proinflammatory Macrophages via Epidermal Fatty Acid Binding Protein

Obesity is associated with elevated levels of free fatty acids (FAs) and proinflammatory CD11c⁺ macrophages. However, whether and how free FAs contribute to CD11c⁺ macrophage differentiation and proinflammatory functions remain unclear. Here we report that dietary saturated FAs, but not unsaturated FAs, promoted the differentiation and function of CD11c⁺ macrophages. Specifically, we demonstrated that stearic acid (SA) significantly induced CD11c expression in monocytes through activation of the nuclear retinoid acid receptor. More importantly, cytosolic expression of epidermal FA binding protein (E-FABP) in monocytes/macrophages was shown to be critical to the mediation of the SA-induced effect. Depletion of E-FABP not only inhibited SA-induced CD11c upregulation in macrophages in vitro but also abrogated high-saturated-fat diet-induced skin lesions in obese mouse models in vivo. Altogether, our data demonstrate a novel mechanism by which saturated FAs promote obesity-associated inflammation through inducing E-FABP/retinoid acid receptor-mediated differentiation of CD11c⁺ macrophages.

Breast Cancer Prevention: Current Approaches and Future Directions

The topic of breast cancer prevention is very broad. All aspects of the topic, therefore, cannot be adequately covered in a single review. The objective of this review is to discuss strategies in current use to prevent breast cancer, as well as potential approaches that could be used in the future. This review does not discuss early detection strategies for breast cancer, including breast cancer screening. The breast is the most common site among women worldwide of noncutaneous cancer. Many clinical and genetic factors have been found to increase a woman's risk of developing the disease. Current strategies to decrease a woman's risk of developing breast cancer include primary prevention, such as avoiding tobacco, exogenous hormone use and excess exposure to ionizing radiation, maintaining a normal weight, exercise, breastfeeding, eating a healthy diet and minimizing alcohol intake. Chemoprevention medications are available for those at high risk, though they are underutilized in eligible women. Mastectomy and/or bilateral oophorectomy are reasonable strategies for women who have deleterious mutations in genes that dramatically increase the risk of developing cancer in either breast. There are a variety of strategies in development for the prevention of breast cancer. Personalized approaches to prevent breast cancer that are being developed focus on advances in precision medicine, knowledge of the immune system and the tumor microenvironment and their role in cancer development. Advances in our understanding of how breast cancer develops are allowing investigators to specifically target populations who are most likely to benefit. Additionally, prevention clinical trials are starting to evaluate multi-agent cancer prevention approaches, with the hope of improved efficacy over single agents. Finally, there is a push to increase the use of chemopreventive agents with proven efficacy, such as tamoxifen and raloxifene, in the prevention of breast cancer.

Reliable Biomarkers to Identify New and Recurrent Cancer

Breast cancer is the most frequent cancer detected throughout both the developing and the developed world. Its incidence is on the rise in the developing world. Great strides have been made in developing biomarkers to guide therapy for women diagnosed with breast cancer. Far fewer advances have occurred with biomarker development for the early diagnosis of breast cancer. Standard screening for new and recurrent breast cancer involves clinical breast exam and breast imaging. There are no Food and Drug Administration (FDA) approved noninvasive body fluid tests for the early detection of new or recurrent breast cancer. Promising biomarker approaches include multianalyte testing of tissue for individuals diagnosed with breast cancer and body fluid analysis for both at risk women and to monitor individuals after treatment.

Human Milk and Matched Serum Demonstrate Concentration of Select miRNAs

BACKGROUND

Pregnancy-associated breast cancers (PABCs), especially those diagnosed after childbirth, are often aggressive, with a poor prognosis. Factors influencing PABC are largely unknown. Micro(mi)RNAs are present in many human body fluids and shown to influence cancer development and/or growth.

SUBJECTS AND METHODS

In six nursing mothers, we determined if breast cancer-associated miRNAs were (1) detectable in human breast milk and (2) if detectable, their relative expression in milk fractions compared to matched serum. We evaluated by quantitative PCR the expression of 11 cancer-associated miRNAs (10a-5p, 16, 21, 100, 140, 145, 155, 181, 199, 205, 212) in breast milk cells, fat and supernatant (skim milk), and matched serum.

RESULTS

miRNA expression was detectable in all samples. For 10/11 miRNAs, mean relative expression compared to control (ΔCt) values was lowest in milk cells, the exception being miR205. Relative concentration was highest in the skim fraction of milk for all miRNAs. Expression was higher in skim milk than matched serum for 7/11 miRNAs and in serum for 4/11 miRNAs. miR205 expression was higher in all milk fractions than in matched serum.

CONCLUSION

In conclusion, the expression of breast cancer-associated miRNAs is detectable in human breast milk and serum samples. The concentration is highest in skim milk, but is also detectable in milk fat and milk cells.

Adipose Fatty Acid Binding Protein Promotes Saturated Fatty Acid-Induced Macrophage Cell Death through Enhancing Ceramide Production

Macrophages play a critical role in obesity-associated chronic inflammation and disorders. However, the molecular mechanisms underlying the response of macrophages to elevated fatty acids (FAs) and their contribution to metabolic inflammation in obesity remain to be fully elucidated. In this article, we report a new mechanism by which dietary FAs, in particular, saturated FAs (sFAs), are able to directly trigger macrophage cell death. We demonstrated that excess sFAs, but not unsaturated FAs, induced the production of cytotoxic ceramides (Cers) in macrophage cell lines. Most importantly, expression of adipose FA binding protein (A-FABP) in macrophages facilitated metabolism of excess sFAs for Cer synthesis. Inhibition or deficiency of A-FABP in macrophage cell lines decreased sFA-induced Cer production, thereby resulting in reduced cell death. Furthermore, we validated the role of A-FABP in promoting sFA-induced macrophage cell death with primary bone marrow-derived macrophages and high-fat diet-induced obese mice. Altogether, our data reveal that excess dietary sFAs may serve as direct triggers in induction of Cer production and macrophage cell death through elevated expression of A-FABP, thus establishing A-FABP as a new molecular sensor in triggering macrophage-associated sterile inflammation in obesity.

Exosomes in Human Breast Milk Promote EMT

PURPOSE

Pregnancy increases breast cancer risk for all women for at least 5 years after parturition. During weaning and involution, the breast microenvironment becomes tumor promotional. Exosomes provide cell-cell communication during physiologic processes such as lactation, but also in breast cancer. We determined whether molecules in milk exosomes from healthy lactating women modulate the development and progression of breast cancer.

EXPERIMENTAL DESIGN

Thirteen nursing women provided three (transitional, mature, and wean) milk samples. Exosomes were extracted and MCF7 and MCF10A breast cells labeled. The expression of six proteins linked to breast cancer was measured. On the basis of the findings, TGFβ2 concentration in exosome samples was measured, breast cells incubated with the exosomes and effect (epithelial-mesenchymal transition, EMT) on EMT-related proteins [E-cadherin, α-smooth muscle actin (α-SMA), filamentous (F)-actin and vimentin] measured.

RESULTS

Human milk exosomes entered benign and malignant breast cells. The greatest change in wean milk protein was in TGFβ2 (P = 0.01). Exosomes with a high (but not low) level of TGFβ2 led to EMT in both cancer and benign cells, based on (i) change in cell morphology, actin cytoskeleton, and loss of cell-cell junction structure and (ii) increased α-SMA and vimentin and decreased E-cadherin.

CONCLUSIONS

TGFβ2 is significantly upregulated in breast milk exosomes during weaning/early involution. Breast milk exosomes containing high levels of TGFβ2 induce changes in both benign and malignant breast epithelial cells, consistent with the development and progression of breast cancer, suggesting a role for high TGFβ2-expressing breast milk exosomes in influencing breast cancer risk. Clin Cancer Res; 22(17); 4517-24. ©2016 AACR.

Expression of the Extracellular Matrix Protein Tenascin-C Varies During Lactation

BACKGROUND

Women diagnosed with pregnancy-associated breast cancer postpartum have a worse prognosis, stage for stage, than other women with breast cancer. The time of breast involution is tumor promotional. The extracellular matrix protein tenascin-C is upregulated during involution in animal models and promotes breast cancer progression. It interacts with transforming growth factor (TGF)β, which also is involved in breast involution and breast cancer progression. Little is known about the expression of tenascin-C during human breast involution, nor its relationship to TGFβ. The purpose of this study was to investigate the expression of tenascin-C throughout lactation, as well as its relationship to TGFβ1 and TGFβ2.

MATERIAL AND METHODOLOGY

Three milk samples from 25 lactating women (transitional, whole, and wean) were collected, separated into components (cells, fat, and skim), and the skim fraction analyzed for total protein, tenascin-C, TGFβ1, and TGFβ2. Tenascin-C, TGFβ1, and TGFβ2 were detectable in all milk samples.

RESULTS

Highest tenascin-C levels on average were found in whole milk, whereas highest mean TGFβ1 and TGFβ2 levels were in wean milk. Wean samples on average had higher levels of both TGFβ1 (26%) and TGFβ2 (>500%) than matched transitional milk samples. Tenascin-C levels in wean milk were associated with nursing length (p = 0.048). Combining all three milk collection time points, tenascin-C exhibited a weak inverse correlation with TGFβ1 and TGFβ2 (p < 0.1). The inverse correlation at the wean time point was stronger for TGFβ2 than -1 (-0.37 versus -0.25). Tenascin-C, a protein known to promote breast cancer progression, is expressed throughout lactation.

CONCLUSION

The inverse correlation with TGFβ2 in wean milk suggests a possible interaction during breast involution, which should be further investigated.

Abstract P1-04-01: Breast milk exosomes promote breast cancer progression

Background: The stimulation of extant neoplastic cells vs. their inhibition during breast involution is a key concept in whether pregnancy and lactation decrease or increase breast cancer risk. The time of weaning, a period of breast involution and remodeling, appears critical to future breast cancer risk, as during involution the breast microenvironment becomes tumor promotional. Both matrix metalloproteinases (MMPs) and transforming growth factor (TGF)β isoforms have been implicated in this process. We previously reported that TGFβ2 (but not TGFβ1) expression was significantly higher in milk collected from the cancer containing (vs. matched clinically normal) breast of women diagnosed with cancer during lactation.

Hypothesis: TGFβ2 in milk exosomes from healthy lactating women modulates the development and progression of breast cancer.

Methods: Matched (early, mature and wean-early involution) milk samples were collected from 13 lactating women, exosomes isolated and the levels of five (MMP2, 3, 9; TGFβ1, 2) proteins measured. Based on the results, additional wean samples were analyzed for TGFβ2 expression and samples divided based on their TGFβ2 expression. The highest and lowest TGFβ2 expressing milk exosome samples were co-cultured with MCF-7 breast cancer cells grown in exosome-depleted media. Cell proliferation was measured after 24h. Confocal microscopy was performed after 72h to evaluate epithelial to mesenchymal transition (EMT) in the cells. A TGFβ2 neutralizing blocking antibody was applied after 72 h co-culture.

Results: The greatest increase in expression (four-fold) at the time of involution was in TGFβ2. Confocal microscopy performed 24h after co-culture confirmed the uptake of the exosomes (both those expressing hi and lo TGFβ2) in the MCF-7 cells. There was a significant increase in cell proliferation compared to control (p&lt;0.001) in cells treated with hi TGFβ2 milk exosomes. 72h after co-culture, bright field microscopy demonstrated that MCF-7 cells treated with hi TGFβ2 underwent EMT including the formation of filopodia, whereas those treated with low TGFβ2 did not. A TGFβ2 blocking antibody reversed the EMT phenotype and filopodia formation.

Impact: Pregnancy has a lasting influence on breast cancer risk, and pregnancy associated breast cancers (PABCs) diagnosed after delivery are generally aggressive, with a poor prognosis. Part of the reason for the development of PABCs, and the aggressive nature of PABCs may be the influence of high-expressing TGFβ2 exosomes in the milk on the breast ductal epithelium.

Citation Format: Sauter ER, Qin W, Dasgupta S. Breast milk exosomes promote breast cancer progression. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-04-01.

Protease-activated Receptor-2 (PAR-2)-mediated Nf-κB Activation Suppresses Inflammation-associated Tumor Suppressor MicroRNAs in Oral Squamous Cell Carcinoma

Oral cancer is the sixth most common cause of death from cancer with an estimated 400,000 deaths worldwide and a low (50%) 5-year survival rate. The most common form of oral cancer is oral squamous cell carcinoma (OSCC). OSCC is highly inflammatory and invasive, and the degree of inflammation correlates with tumor aggressiveness. The G protein-coupled receptor protease-activated receptor-2 (PAR-2) plays a key role in inflammation. PAR-2 is activated via proteolytic cleavage by trypsin-like serine proteases, including kallikrein-5 (KLK5), or by treatment with activating peptides. PAR-2 activation induces G protein-α-mediated signaling, mobilizing intracellular calcium and Nf-κB signaling, leading to the increased expression of pro-inflammatory mRNAs. Little is known, however, about PAR-2 regulation of inflammation-related microRNAs. Here, we assess PAR-2 expression and function in OSCC cell lines and tissues. Stimulation of PAR-2 activates Nf-κB signaling, resulting in RelA nuclear translocation and enhanced expression of pro-inflammatory mRNAs. Concomitantly, suppression of the anti-inflammatory tumor suppressor microRNAs let-7d, miR-23b, and miR-200c was observed following PAR-2 stimulation. Analysis of orthotopic oral tumors generated by cells with reduced KLK5 expression showed smaller, less aggressive lesions with reduced inflammatory infiltrate relative to tumors generated by KLK5-expressing control cells. Together, these data support a model wherein KLK5-mediated PAR-2 activation regulates the expression of inflammation-associated mRNAs and microRNAs, thereby modulating progression of oral tumors.

Complex-I Alteration and Enhanced Mitochondrial Fusion Are Associated With Prostate Cancer Progression

Mitochondria (mt) encoded respiratory complex-I (RCI) mutations and their pathogenicity remain largely unknown in prostate cancer (PCa). Little is known about the role of mtDNA loss on mt integrity in PCa. We determined mtDNA mutation in human and mice PCa and assessed the impact of mtDNA depletion on mt integrity. We also examined whether the circulating exosomes from PCa patients are transported to mt and carry mtDNA or mt proteins. We have employed next generation sequencing of the whole mt genome in human and Hi-myc PCa. The impact of mtDNA depletion on mt integrity, presence of mtDNA, and protein in sera exosomes was determined. A co-culture of human PCa cells and the circulating exosomes followed by confocal imaging determined co-localization of exosomes and mt. We observed frequent RCI mutations in human and Hi-myc PCa which disrupted corresponding complex protein expression. Depletion of mtDNA in PCa cells influenced mt integrity, increased expression of MFN1, MFN2, PINK1, and decreased expression of MT-TFA. Increased mt fusion and expression of PINK1 and DNM1L were also evident in the Hi-myc tumors. RCI-mtDNA, MFN2, and IMMT proteins were detected in the circulating exosomes of men with benign prostate hyperplasia (BPH) and progressive PCa. Circulating exosomes and mt co-localized in PCa cells. Our study identified new pathogenic RCI mutations in PCa and defined the impact of mtDNA loss on mt integrity. Presence of mtDNA and mt proteins in the circulating exosomes implicated their usefulness for biomarker development.

Polyunsaturated fatty acid content may be increased in the milk of women with pregnancy-associated breast cancer

BACKGROUND

Pregnancy-associated breast cancer (PABC) is aggressive and difficult to diagnose. High intake of most types of dietary fat is thought to increase breast cancer risk; however, results in humans supporting this premise remain equivocal. Fatty acid (FA) concentrations in the body comprise both dietary intake and endogenous FA production. Most assessments of FA levels have been performed on blood, with little information on the effect of FA levels in breast milk on PABC risk.

OBJECTIVE

This study aimed to determine if FA concentrations in the milk from women diagnosed with breast cancer while nursing were different in the cancer-containing breast and opposite breast.

METHODS

We quantified 16 long-chain FA and soluble FA synthase (sFAS) enzyme levels from 4 women diagnosed with PABC, comparing results from the cancer-containing breast to those from the normal breast.

RESULTS

Fatty acid concentrations consistently exceeded and trended higher (P < .10) in each cancer-containing breast for 20:4n-6 (arachidonic acid [AA]), 20:5n-3 (eicosapentaenoic acid [EPA]), and 22:5n-6 (docosapentaenoic acid [DPA]). Soluble FA synthase levels were similar in the cancer-containing and normal breasts.

CONCLUSION

Breast milk concentrations of AA, EPA, and DPA increased in the cancer-containing breast of women with PABC. This increase was not associated with higher sFAS levels.

MDA-9/Syntenin regulates differentiation and angiogenesis programs in head and neck squamous cell carcinoma

Little is known about the molecular pathways regulating poor differentiation and invasion of head and neck squamous cell carcinoma (HNSCC). In the present study, we aimed to determine the role of MDA-9/Syntenin, a metastasis associated molecule in HNSCC tumorigenesis. Elevated MDA-9/Syntenin expression was evident in 67% (54/81) primary HNSCC tumors (p=0.001-0.002) and 69% (9/13) pre-neoplastic tissues (p=0.02-0.03). MDA-9/Syntenin overexpression was associated with the stage (p=0.001), grade (p=0.001) and lymph node metastasis (p=0.0001). Silencing of MDA-9/Syntenin in 3 poorly differentiated HNSCC cell lines induced squamous epithelial cell differentiation, disrupted angiogenesis and reduced tumor growth in vitro and in vivo. We confirmed SPRR1B and VEGFR1 as the key molecular targets of MDA-9/Syntenin on influencing HNSCC differentiation and angiogenesis respectively. MDA-9/Syntenin disrupted SPRR1B expression interacting through its PDZ1 domain and altered VEGFR1 expression in vitro and in vivo. VEGFR1 co-localized with MDA-9/Syntenin in HNSCC cell lines and primary tumor. Downregulation of growth regulatory molecules CyclinD1, CDK4, STAT3, PI3K and CTNNB1 was also evident in the MDA-9/Syntenin depleted cells, which was reversed following over-expression of MDA-9/Syntenin in immortalized oral epithelial cells. Our results suggest that early induction of MDA-9/Syntenin expression influences HNSCC progression and should be further evaluated for potential biomarker development.

Determination of Celecoxib in human plasma using liquid chromatography with high resolution time of flight-mass spectrometry

A sensitive method for the determination of Celecoxib (CXB) in human plasma samples was developed using liquid chromatography coupled to electrospray ionization and time of flight mass spectrometry (LC-ESI-TOF-MS). A full factorial design of experiments (FF-DOE) methodology was applied to optimize the ESI conditions for CXB determination and also to predict the effects of interactions of multiple parameters affecting ionization (i.e., capillary voltage, fragmentor voltage, electrolyte and electrolyte concentration). The optimum ionization voltages were 4500V and 220V for capillary and fragmentor, respectively. Even though the highest ESI efficiency was obtained without electrolytes, the addition of 1.0mM ammonium acetate was shown to be essential to buffer the matrix effect and ensure a consistent response. In contrast to previous studies, deuterated CXB was used as a recovery (surrogate) standard, which enabled the correction of CXB loss during sample preparation. The extraction recovery using solid phase extraction was 87-98%. The instrumental limit of detection of CXB (LOD), 0.33ng/mL, and matrix affected LOD, 0.55ng/mL, were similar and comparable to the previously reported LC-MS/MS LODs. This method was employed to determine CXB concentrations in human plasma samples. Upon administration of 400mg CXB to the healthy women, the concentrations found in the plasma were 440-3300ng/mL. The inter-day repeatability was less than 4% RSD.

Calcium homeostasis and bone metabolic responses to high-protein diets during energy deficit in healthy young adults: a randomized controlled trial

BACKGROUND

Although consuming dietary protein above current recommendations during energy deficit (ED) preserves lean body mass, concerns have been raised regarding the effects of high-protein diets on bone health.

OBJECTIVE

The objective was to determine whether calcium homeostasis and bone turnover are affected by high-protein diets during weight maintenance (WM) and ED.

DESIGN

In a randomized, parallel-design, controlled trial of 32 men and 7 women, volunteers were assigned diets providing protein at 0.8 [Recommended Dietary Allowance (RDA)], 1.6 (2 × RDA), or 2.4 (3 × RDA) g · kg(-1) · d(-1) for 31 d. Ten days of WM preceded 21 d of ED, during which total daily ED was 40%, achieved by reduced dietary energy intake (∼30%) and increased physical activity (∼10%). The macronutrient composition (protein g · kg(-1) · d(-1) and % fat) was held constant from WM to ED. Calcium absorption (ratio of (44)Ca to (42)Ca) and circulating indexes of bone turnover were determined at day 8 (WM) and day 29 (ED).

RESULTS

Regardless of energy state, mean (±SEM) urinary pH was lower (P < 0.05) at 2 × RDA (6.28 ± 0.05) and 3 × RDA (6.23 ± 0.06) than at the RDA (6.54 ± 0.06). However, protein had no effect on either urinary calcium excretion (P > 0.05) or the amount of calcium retained (P > 0.05). ED decreased serum insulin-like growth factor I concentrations and increased serum tartrate-resistant acid phosphatase and 25-hydroxyvitamin D concentrations (P < 0.01). Remaining markers of bone turnover and whole-body bone mineral density and content were not affected by either the protein level or ED (P > 0.05).

CONCLUSION

These data demonstrate that short-term consumption of high-protein diets does not disrupt calcium homeostasis and is not detrimental to skeletal integrity. This trial was registered at www.clinicaltrials.gov as NCT01292395.

Methylation and miRNA effects of resveratrol on mammary tumors vs. normal tissue

We reported that resveratrol decreased DNA methyltransferase (DNMT) 1 and 3b expression in vitro and demethylates tumor suppressor RASSF-1a in women at increased breast cancer risk. We investigated the effects of resveratrol on DNMT and miRNA expression in normal and tumor mammary tissue in a rodent model of estrogen dependent mammary carcinoma. Eighty-nine female ACI rats received estradiol plus: low dose (lo) resveratrol, high dose (hi) resveratrol, 5-aza-2-deoxycytidine (Aza), a known inhibitor of DNMTs, or control (no additional treatment). After 21 wk of treatment, animals were sacrificed and mammary glands harvested. Matched tumor/normal tissues were available from 36 rats. DMNT3b (but not DNMT1) differed in tumor vs. normal tissue after lo (P = .04) and hi (P = .007) resveratrol and Aza treatment. With hi resveratrol, DNMT3b decreased in tumor but increased normal tissue. Hi resveratrol increased miR21, -129, -204, and -489 >twofold in tumor and decreased the same miRs in normal tissue 10-50% compared to control. There was an inverse association between DNMT3b and miR129, -204, and -489 in normal and/or tumor tissue. Treatment with resveratrol differentially influences tumor vs. normal tissue DNMT3b and miRNA expression. This mechanism of action of resveratrol to influence mammary carcinogenesis warrants further investigation.

Analysis of nipple aspirate fluid for diagnosis of breast cancer: an alternative to invasive biopsy

Over 40,000 women in the USA will die this year of breast cancer. Current generally accepted techniques to detect breast cancer are limited to breast examination and mammography. Abnormalities found by these techniques require an invasive needle or surgical biopsy to determine if cancer is present. The author's ultimate goal is to determine if a woman has breast cancer without the need for invasive biopsies, and do this before the abnormality is detectable by standard screening techniques. Herein, the technology is reviewed as it was, as it is today, and its future potential is discussed.

Abstract B26: Epigenetic effects of resveratrol on mammary carcinoma

Background: We previously reported that resveratrol decreased DNA methyltransferase (DNMT) 1 and 3b expression in vitro and demethylates tumor suppressor RASSF-1a in women at increased breast cancer risk. Herein we document the effects of resveratrol on DNMT and miRNA expression in normal and malignant mammary tissue in a rodent model of estrogen dependent mammary carcinoma.

Methods: 89 female rats received slow release estradiol plus: low dose (lo) resveratrol, high dose (hi) resveratrol, 5-aza-2-deoxycytidine (Aza), a known inhibitor of DNMTs, or control (no additional treatment). After 21 weeks of treatment, animals were sacrificed and mammary glands harvested. Matched tumor and normal tissues were available from 36 rats.

Results: DMNT3b (but not DNMT1) differed in tumor vs. normal tissue after lo (p=.04) and hi p=.007) resveratrol. With hi resveratrol, DNMT3b decreased in tumor but increased normal tissue. Hi resveratrol increased miR21, -129, -204 and -489 from 2.5 to &gt;5 fold in tumor and decreased the same miRs in normal tissue 10-50% compared to control. There was an inverse association between DNMT3b and miR129, 204, and 489 in normal and/or tumor tissue.

Conclusion: Treatment with resveratrol differentially influences malignant vs. normal tissue DNMT3b and miRNA expression. This mechanism of action of resveratrol to influence mammary carcinogenesis warrants further investigation.

Citation Format: Wenyi Qin, Ke Zhang, Kaitlin Clarke, Timothy Weiland, Edward R. Sauter. Epigenetic effects of resveratrol on mammary carcinoma. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr B26.

Vitamin D favorably alters the cancer promoting prostaglandin cascade

BACKGROUND

Preclinical studies suggest that 1,25-dihydroxyvitamin D [1,25(OH)2D] and celecoxib inhibit prostaglandins (PGs) associated with cancer through different mechanisms. We determined if there was synergy in their use.

PATIENTS AND METHODS

A total of 36 healthy women received daily for one month/menstrual cycle: placebo, 400 international units (IU) vitamin D-3, 2,000 IU vitamin D-3, or 2,000 IU vitamin D-3 plus 400 mg celecoxib. Serum and nipple aspirate fluid (NAF) were analyzed for PGE2 and transforming growth factor (TGF)β1 and -2; serum for 25(OH)D (total, -D-2, -D-3), plasma for celecoxib; and mammary duct RNA for cyclooxygenase (COX)2.

RESULTS

25(OH)D-3 increased (p<0.01) only in the groups receiving 2,000 IU vitamin D-3. PGE2 decreased in the breast (p=0.01) only after receiving 2,000 IU vitamin D-3; 2,000 IU vitamin D-3 alone was more effective in decreasing PGE2 than 2,000 IU vitamin D-3 plus celecoxib (p=0.018). COX2 expression decreased only in the breasts of women taking 2,000 IU vitamin D-3. Change in circulating 25(OH)D-3 correlated with change in TGFβ2 in the breast.

CONCLUSION

Vitamin D-3 reduces the PG cascade and increases TGFβ2 in a dose-dependent fashion. Adding celecoxib did not provide synergy.

Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial

The purpose of this work was to determine the effects of varying levels of dietary protein on body composition and muscle protein synthesis during energy deficit (ED). A randomized controlled trial of 39 adults assigned the subjects diets providing protein at 0.8 (recommended dietary allowance; RDA), 1.6 (2×-RDA), and 2.4 (3×-RDA) g kg(-1) d(-1) for 31 d. A 10-d weight-maintenance (WM) period was followed by a 21 d, 40% ED. Body composition and postabsorptive and postprandial muscle protein synthesis were assessed during WM (d 9-10) and ED (d 30-31). Volunteers lost (P<0.05) 3.2 ± 0.2 kg body weight during ED regardless of dietary protein. The proportion of weight loss due to reductions in fat-free mass was lower (P<0.05) and the loss of fat mass was higher (P<0.05) in those receiving 2×-RDA and 3×-RDA compared to RDA. The anabolic muscle response to a protein-rich meal during ED was not different (P>0.05) from WM for 2×-RDA and 3×-RDA, but was lower during ED than WM for those consuming RDA levels of protein (energy × protein interaction, P<0.05). To assess muscle protein metabolic responses to varied protein intakes during ED, RDA served as the study control. In summary, we determined that consuming dietary protein at levels exceeding the RDA may protect fat-free mass during short-term weight loss.