Mechanistic targets and phytochemical strategies for breaking the obesity-cancer link

Health Behavior Change Intervention Preferences Expressed by American Indian Cancer Survivors From a Southwest Tribal Community: Semistructured Interview Study

BACKGROUND

While many factors, including social determinants of health, affect cancer mortality, one modifiable risk factor that may contribute to cancer disparities is obesity. The prevalence of obesity in the American Indian/Alaska Native population is 48.1% per the Centers for Disease Control and Prevention. The overall cancer mortality for the American Indian/Alaska Native population is 18% higher than the White population as reported by the American Cancer Society. Interventions tailored to American Indian/Alaska Native communities that promote healthy lifestyle behaviors after cancer diagnosis and prior to cancer surgery (prehab) might improve cancer outcomes for this population.

OBJECTIVE

The aim of the study is to characterize the lifestyle behaviors of San Carlos Apache cancer survivors and identify preferences for the adaption of a prehab intervention.

METHODS

Semistructured interviews and validated questionnaires were completed with San Carlos Apache cancer survivors (N=4), exploring their viewpoints on healthy lifestyle and cancer risk and preferences for program development. A thematic content analysis was conducted.

RESULTS

Participants had an average BMI of 31 kg/m2 and walked 53 minutes daily. The majority of participants reported a high willingness to change eating habits (n=3, 75%). All 4 reported willingness to participate in a diet and exercise program. Important themes and subthemes were identified: (1) cancer is perceived as a serious health condition in the community (N=4, 100%); (2) environmental exposures are perceived as cancer-causing threats (n=3, 75%); (3) healthy diet, exercise, and avoiding harmful substances are perceived as mitigating cancer risk (n=3, 75%); (4) barriers to healthy habits include distance to affordable groceries (n=3, 75%) and lack of transportation (n=2, 50%); (5) there is high interest in a prehab program geared toward patients with cancer (N=4, 100%); and (6) standard monitoring practiced in published prehab programs showed early acceptability with participants (N=4, 100%).

CONCLUSIONS

Collaboration with tribal partners provided important insight that can help inform the adaptation of a culturally appropriate prehab program for San Carlos Apache patients diagnosed with cancer.

Fat-enlarged axillary lymph nodes are associated with node-positive breast cancer in obese patients

PURPOSE

Obesity associated fat infiltration of organ systems is accompanied by organ dysfunction and poor cancer outcomes. Obese women demonstrate variable degrees of fat infiltration of axillary lymph nodes (LNs), and they are at increased risk for node-positive breast cancer. However, the relationship between enlarged axillary nodes and axillary metastases has not been investigated. The purpose of this study is to evaluate the association between axillary metastases and fat-enlarged axillary nodes visualized on mammograms and breast MRI in obese women with a diagnosis of invasive breast cancer.

METHODS

This retrospective case-control study included 431 patients with histologically confirmed invasive breast cancer. The primary analysis of this study included 306 patients with pre-treatment and pre-operative breast MRI and body mass index (BMI) > 30 (201 node-positive cases and 105 randomly selected node-negative controls) diagnosed with invasive breast cancer between April 1, 2011, and March 1, 2020. The largest visible LN was measured in the axilla contralateral to the known breast cancer on breast MRI. Multivariate logistic regression models were used to assess the association between node-positive status and LN size adjusting for age, BMI, tumor size, tumor grade, tumor subtype, and lymphovascular invasion.

RESULTS

A strong likelihood of node-positive breast cancer was observed among obese women with fat-expanded lymph nodes (adjusted OR for the 4th vs. 1st quartile for contralateral LN size on MRI: 9.70; 95% CI 4.26, 23.50; p < 0.001). The receiver operating characteristic curve for size of fat-enlarged nodes in the contralateral axilla identified on breast MRI had an area under the curve of 0.72 for predicting axillary metastasis, and this increased to 0.77 when combined with patient and tumor characteristics.

CONCLUSION

Fat expansion of axillary lymph nodes was associated with a high likelihood of axillary metastases in obese women with invasive breast cancer independent of BMI and tumor characteristics.

Anti-obesity Medications in Cancer Therapy: A Comprehensive Insight

The interplay between cancer and obesity is multifactorial and complex with the increased risk of cancer development in obese individuals posing a significant threat. Obesity leads to the upregulation or hyperactivation of several oncogenic pathways in cancer cells, which drives them towards a deleterious phenotype. The cross-talk between cancer and obesity is considered a large contributing factor in the development of chemotherapeutic drug resistance and the resistance to radiotherapy. The link between obesity and the development of cancer is so strong that a medication that demonstrates effectiveness against both conditions would serve as an essential step. In this context, anti-obesity medications provide a worthy list of candidates based on their chemo-preventive potential and chemotherapeutic properties. The current study focuses on exploring the potential of anti-obesity medicines as dual anticancer drugs. These medications target several key signaling pathways (e.g., AMPK, PI3K/Akt/mTOR, MAPK, NF-κB, JNK/ERK), which prove to be crucial for both cancer growth and metastases. Some of these drugs also play an important role in attenuating the signaling and cellular events which incite cancer-obesity cross-talk and demonstrate efficient counteraction of neoplastic transformation. Thus, this review highlights a comprehensive view of the potential use of anti-obesity medicines to treat both cancer and obesity for patients exhibiting both comorbities.

Mechanisms of action for the anti-obesogenic activities of phytochemicals

The prevalence of obesity is increasing rapidly globally and has recently reached pandemic proportions. It is a multifactorial disorder linked to a number of non-communicable diseases such as type-2 diabetes, cardiovascular disease, and cancer. Over-nutrition and a sedentary lifestyle are considered the most significant causes of obesity; a healthy lifestyle and behavioural interventions are the most powerful ways to achieve successful weight loss, but to maintain this in the long term can prove difficult for many individuals, without medical intervention. Various pharmacological anti-obesogenic drugs have been tested and marketed in the past and have been moderately successful in the management of obesity, but their adverse effects on human health often outweigh the benefits. Natural products from plants, either in the form of crude extracts or purified phytochemicals, have been shown to have anti-obesogenic properties and are generally considered as nontoxic and cost-effective compared to synthetic alternatives. These plant products combat obesity by targeting the various pathways and/or regulatory functions intricately linked to obesity. Their mechanisms of action include inhibition of pancreatic lipase activities, an increase in energy expenditure, appetite regulation, lipolytic effects, and inhibition of white adipose tissue development. In this review, we discuss the distinct anti-obesogenic properties of recently reported plant extracts and specific bioactive compounds, along with their molecular mechanisms of action. This review will provide a common platform for understanding the different causes of obesity and the possible approaches to using plant products in tackling this worldwide health issue.

Aspirin Modifies Inflammatory Mediators and Metabolomic Profiles and Contributes to the Suppression of Obesity-Associated Breast Cancer Cell Growth

Breast cancer is the most common cancer among women. Adiposity generally accompanies immune cell infiltration and cytokine secretion, which is ideal for tumor development. Aspirin is a chemopreventive agent against several types of cancer. The aim of this study was to investigate whether aspirin inhibits the growth of 4T1 breast cancer cells by inhibiting the inflammatory response and regulating the metabolomic profile of 3T3-L1 adipocytes. 3T3-L1 adipocyte-conditioned medium (Ad-CM) was used to mimic the obese adipose tissue microenvironment in 4T1 cells. The results revealed that aspirin inhibited macrophage chemoattractant protein (MCP-1), interleukin (IL-6), IL-1β, and plasminogen activator inhibitor (PAI-1) production in 3T3-L1 adipocytes stimulated by tumor necrosis factor-alpha (TNF-α) and lipopolysaccharide (LPS). In the obesity-associated model, Ad-CM significantly promoted 4T1 cell growth and migration, which were attenuated after aspirin treatment. The results of metabolic analyses using Ad-CM showed that amino acid metabolites and oxidative stress were increased in mature 3T3-L1 adipocytes compared to those in fibroblasts. Aspirin treatment modified metabolites involved in suppressing lipogenesis, oxidative stress, and neoplastic formation. In the relative fatty acid quantitation analysis of Ad-CM, aspirin diminished fatty acid contents of C16:1, C18:1, C18:2, C20:4, and C24:1. This study is the first to show that aspirin modifies the metabolomics and fatty acid composition of 3T3-L1 adipocytes and inhibits obesity-associated inflammation that contributes to obesity-related breast cancer cell growth and migration.

Obesity and survival in the neoadjuvant breast cancer setting: role of tumor subtype in an ethnically diverse population

BACKGROUND

Obesity may negatively affect survival in breast cancer (BC), but studies are conflicting, and associations may vary by tumor subtypes and race/ethnicity groups.

METHODS

In a retrospective review, we identified 273 women with invasive BC administered Adriamycin/Taxane-based neoadjuvant chemotherapy from 2004 to 2016 with body mass index (BMI) data at diagnosis. Obesity was defined as BMI ≥30. Associations between obesity and event-free survival (EFS), using STEEP events, and overall survival (OS), using all-cause mortality, were assessed overall and stratified by tumor subtype [[Hormone Receptor Positive (HR+)/HER2-, HER2+, and Triple-Negative Breast Cancer (TNBC])] in our diverse population.

RESULTS

Median follow-up was 32.6 months (range 5.7-137.8 months). Overall, obesity was associated with worse EFS (HR 1.71, 95% CI 1.03-2.84, p = 0.04) and a trend towards worse OS (p = 0.13). In HR+/HER2- disease (n = 135), there was an interaction between obesity and hormonal therapy with respect to OS but not EFS. In those receiving tamoxifen (n = 33), obesity was associated with worse OS (HR 9.27, 95% CI 0.96-89.3, p = 0.05). In those receiving an aromatase inhibitor (n = 89), there was no association between obesity and OS. In TNBC (n = 44), obesity was associated with worse EFS (HR 2.62, 95% CI 1.03-6.66, p = 0.04) and a trend towards worse OS (p = 0.06). In HER2+ disease (n = 94), obesity was associated with a trend towards worse EFS (HR 3.37, 95% CI 0.97-11.72, p = 0.06) but not OS. Race/ethnicity was not associated with survival in any subtype, and there were no interactions with obesity on survival.

CONCLUSIONS

Obesity may negatively impact survival, with differences among tumor subtypes.

Lunasin Attenuates Obesity-Associated Metastasis of 4T1 Breast Cancer Cell through Anti-Inflammatory Property

Obesity prevalence is increasing worldwide and is accompanied by low-grade inflammation with macrophage infiltration, which is linked with a poorer breast cancer prognosis. Lunasin is a natural seed peptide with chemopreventive properties and multiple bioactivities. This is the first study to explore the chemopreventive effects of lunasin in the obesity-related breast cancer condition using 4T1 breast cancer cells, 3T3-L1 adipocytes, and conditioned media. An obesity-related environment, such as leptin-treatment or adipocyte-conditioned medium (Ad-CM), promoted 4T1 cell proliferation and metastasis. Lunasin treatment inhibited metastasis of breast cancer cells, partially through modestly inhibiting production of the angiogenesis-mediator vascular endothelial growth factor (VEGF) and significantly by inhibiting secretion in the Ad-CM condition. Subsequently, two adipocytes inflammation models, 3T3-L1 adipocytes were stimulated by tumor necrosis factor (TNF)-α, and RAW 264.7 cell-conditioned medium (RAW-CM) was used to mimic the obese microenvironment. Lunasin significantly inhibited interleukin (IL)-6 and macrophage chemoattractant protein (MCP)-1 secretion by TNF-α stimulation, and MCP-1 secretion in the RAW-CM model. This study highlights that lunasin suppressed 3T3-L1 adipocyte inflammation and inhibited 4T1 breast cancer cell migration. Interestingly, lunasin exerted more effective anti-metastasis activity in the obesity-related condition models, indicating that it possesses anti-inflammatory properties and blocks adipocyte-cancer cell cross-talk.

Aspirin Breaks the Crosstalk between 3T3-L1 Adipocytes and 4T1 Breast Cancer Cells by Regulating Cytokine Production

Breast cancer is one of the most common cancers in women worldwide. The obesity process is normally accompanied by chronic, low-grade inflammation. Infiltration by inflammatory cytokines and immune cells provides a favorable microenvironment for tumor growth, migration, and metastasis. Epidemiological evidence has shown that aspirin is an effective agent against several types of cancer. The aim of this study is to investigate the anti-inflammatory and anti-cancer effects of aspirin on 3T3-L1 adipocytes, 4T1 murine breast cancer cells, and their crosstalk. The results showed that aspirin treatment inhibited differentiation and lipid accumulation by 3T3-L1 preadipocytes, and decreased the secretion of the inflammatory adipokine MCP-1 after stimulation with tumor necrosis factor (TNF)-α or conditioned medium from RAW264.7 cells. In 4T1 cells, treatment with aspirin decreased cell viability and migration, possibly by suppressing MCP-1 and VEGF secretion. Subsequently, culture of 4T1 cells in 3T3-L1 adipocyte-conditioned medium (Ad-CM) and co-culture of 3T3-L1 and 4T1 cells using a transwell plate were performed to clarify the relationship between these two cell lines. Aspirin exerted its inhibitory effects in the transwell co-culture system, as well as the conditioned-medium model. Aspirin treatment significantly inhibited the proliferation of 4T1 cells, and decreased the production of MCP-1 and PAI-1 in both the Ad-CM model and co-culture system. Aspirin inhibited inflammatory MCP-1 adipokine production by 3T3-L1 adipocytes and the cell growth and migration of 4T1 cells. It also broke the crosstalk between these two cell lines, possibly contributing to its chemopreventive properties in breast cancer. This is the first report that aspirin’s chemopreventive activity supports the potential application in auxiliary therapy against obesity-related breast cancer development.

Obesity and cancer: mechanistic insights from transdisciplinary studies

Obesity is associated with a range of health outcomes that are of clinical and public health significance, including cancer. Herein, we summarize epidemiologic and preclinical evidence for an association between obesity and increased risk of breast and prostate cancer incidence and mortality. Moreover, we describe data from observational studies of weight change in humans and from calorie-restriction studies in mouse models that support a potential role for weight loss in counteracting tumor-promoting properties of obesity in breast and prostate cancers. Given that weight loss is challenging to achieve and maintain, we also consider evidence linking treatments for obesity-associated co-morbidities, including metformin, statins and non-steroidal anti-inflammatory drugs, with reduced breast and prostate cancer incidence and mortality. Finally, we highlight several challenges that should be considered when conducting epidemiologic and preclinical research in the area of obesity and cancer, including the measurement of obesity in population-based studies, the timing of obesity and weight change in relation to tumor latency and cancer diagnosis, and the heterogeneous nature of obesity and its associated co-morbidities. Given that obesity is a complex trait, comprised of behavioral, epidemiologic and molecular/metabolic factors, we argue that a transdisciplinary approach is the key to understanding the mechanisms linking obesity and cancer. As such, this review highlights the critical need to integrate evidence from both epidemiologic and preclinical studies to gain insight into both biologic and non-biologic mechanisms contributing to the obesity-cancer link.

Tumor microenvironment and metabolic synergy in breast cancers: critical importance of mitochondrial fuels and function

Metabolic synergy or metabolic coupling between glycolytic stromal cells (Warburg effect) and oxidative cancer cells occurs in human breast cancers and promotes tumor growth. The Warburg effect or aerobic glycolysis is the catabolism of glucose to lactate to obtain adenosine triphosphate (ATP). This review summarizes the main findings on this stromal metabolic phenotype, and the associated signaling pathways, as well as the critical role of oxidative stress and autophagy, all of which promote carcinoma cell mitochondrial metabolism and tumor growth. Loss of Caveolin 1 (Cav-1) and the upregulation of monocarboxylate transporter 4 (MCT4) in stromal cells are novel markers of the Warburg effect and metabolic synergy between stromal and carcinoma cells. MCT4 and Cav-1 are also breast cancer prognostic biomarkers. Reactive oxygen species (ROS) are key mediators of the stromal Warburg effect. High ROS also favors cancer cell mitochondrial metabolism and tumorigenesis, and anti-oxidants can reverse this altered stromal and carcinoma metabolism. A pseudo-hypoxic state with glycolysis and low mitochondrial metabolism in the absence of hypoxia is a common feature in breast cancer. High ROS induces loss of Cav-1 in stromal cells and is sufficient to generate a pseudo-hypoxic state. Loss of Cav-1 in the stroma drives glycolysis and lactate extrusion via HIF-1α stabilization and the upregulation of MCT4. Stromal cells with loss of Cav-1 and/or high expression of MCT4 also show a catabolic phenotype, with enhanced macroautophagy. This catabolic state in stromal cells is driven by hypoxia-inducible factor (HIF)-1α, nuclear factor κB (NFκB), and JNK activation and high ROS generation. A feed-forward loop in stromal cells regulates pseudo-hypoxia and metabolic synergy, with Cav-1, MCT4, HIF-1α, NFκB, and ROS as its key elements. Metabolic synergy also may occur between cancer cells and cells in distant organs from the tumor. Cancer cachexia, which is due to severe organismal metabolic dysregulation in myocytes and adipocytes, shares similarities with stromal-carcinoma metabolic synergy, as well. In summary, metabolic synergy occurs when breast carcinoma cells induce a nutrient-rich microenvironment to promote tumor growth. The process of tumor metabolic synergy is a multistep process, due to the generation of ROS, and the induction of catabolism with autophagy, mitophagy and glycolysis. Studying epithelial-stromal interactions and metabolic synergy is important to better understand the ecology of cancer and the metabolic role of different cell types in tumor progression.

Catabolic cancer-associated fibroblasts transfer energy and biomass to anabolic cancer cells, fueling tumor growth

Fibroblasts are the most abundant "non-cancerous" cells in tumors. However, it remains largely unknown how these cancer-associated fibroblasts (CAFs) promote tumor growth and metastasis, driving chemotherapy resistance and poor clinical outcome. This review summarizes new findings on CAF signaling pathways and their emerging metabolic phenotypes that promote tumor growth. Although it is well established that altered cancer metabolism enhances tumor growth, little is known about the role of fibroblast metabolism in tumor growth. New studies reveal that metabolic coupling occurs between catabolic fibroblasts and anabolic cancer cells, in many types of human tumors, including breast, prostate, and head & neck cancers, as well as lymphomas. These catabolic phenotypes observed in CAFs are secondary to a ROS-induced metabolic stress response. Mechanistically, this occurs via HIF1-alpha and NFκB signaling, driving oxidative stress, autophagy, glycolysis and senescence in stromal fibroblasts. These catabolic CAFs then create a nutrient-rich microenvironment, to metabolically support tumor growth, via the local stromal generation of mitochondrial fuels (lactate, ketone bodies, fatty acids, glutamine, and other amino acids). New biomarkers of this catabolic CAF phenotype (such as caveolin-1 (Cav-1) and MCT4), which are reversible upon treatment with anti-oxidants, are strong predictors of poor clinical outcome in various types of human cancers. How cancer cells metabolically reprogram fibroblasts can also help us to understand the effects of cancer cells at an organismal level, explaining para-neoplastic phenomena, such as cancer cachexia. In conclusion, cancer should be viewed more as a systemic disease, that engages the host-organism in various forms of energy-transfer and metabolic co-operation, across a whole-body "ecosystem".