Obesity-associated Breast Cancer Research Articles

The effects of muscle factors irisin on lipid metabolism in breast cancer: A possible mechanism anti-tumor mechanism of physical activity

Breast cancer is the most prevalent cancer in the female population and is a significant cause of global cancer deaths in this group. Obesity increases a woman’s risk of developing breast cancer and has a negative impact on prognosis. Metabolic alterations are an important part of the process of cancer migration; invasion and proliferation, with lipids being a major metabolic substrate for rapid cancer progression, capable of influencing the metabolic crosstalk between tumor cells and other cells in the tumor microenvironment. Physical activity-induced irisin affects the progression of obesity-associated breast cancer and is a new indicator for breast cancer diagnosis. Existing evidence suggests a potential inhibitory effect of physical activity-induced irisin on the progression of breast cancer. A strong association exists between obesity and breast cancer progression and outcomes. This paper discusses how physical activity-induced irisin may achieve cancer suppression by affecting lipid metabolic processes between breast cancer cells and cancer-associated adipocytes, and elucidates the molecular pathways involved in the effects of irisin on cancer lipid reprogramming, thereby helping to prevent the metastatic progression of breast cancer, and ultimately improving the survival rate of this patient group.

Single-cell RNA-sequencing reveals a unique landscape of the tumor microenvironment in obesity-associated breast cancer

As two diseases with rapidly increasing incidence, the molecular linkages between obesity and breast cancer (BC) are intriguing. Overall, obesity may be a negative prognostic factor for BC. Single-cell RNA-sequencing (scRNA-seq) was performed on tumor tissues from 6 obese and non-obese BC patients. With 48,033 cells analyzed, we found heterogeneous tumor epithelium and microenvironment in these obese and lean BC patients. Interestingly, the obesity-associated epithelial cells exhibited specific expression signatures which linked tumor growth and hormone metabolism in BC. Notably, one population of obesity-specific macrophage up-regulated the nuclear receptor subfamily 1 group H member 3 (NR1H3), which acted a transcription factor and regulated FABP4 expression through its interaction with the DNA of SREBP1, and further increased the proliferation of tumor cells in BC. Using single-cell signatures, our study illustrate cell diversity and transcriptomic differences in tumors from obese and non-obese BC patients, and sheds light on potential molecular link between lipid metabolism and BC.

Abstract 3935: Involvement of nanoscale physical communication in obesity-associated breast cancer severity

Abstract Obesity is a risk factor for several cancers, including breast cancer, and contributes up to 20% of cancer-related deaths. Growing evidence from both clinical and preclinical studies indicates that increased obesity is associated with increases in cancer incidence, progression, metastasis, and therapeutic resistance. According to the Centers for Disease Control and Prevention (CDC), more than 70% and 40% of American adults can be classified as overweight and obese, respectively. However, treatment strategies for dealing with cancer in obese patients have not advanced apart from lifestyle interventions. However, several signaling mechanisms have been proposed related to the inflammatory and metabolic impact of obese adipocytes in promoting cancer progression. However, a lack of mechanistic understanding led to no specific treatment strategies have been proposed which can specifically downregulate the key regulator by which obese adipocytes promote cancer progression. Thus, translational research initiatives are immediately needed to provide mechanistic justifications for these striking statistics in order to better serve this growing segment of the population. Here, we have shown the role of nanoscale physical communication between breast cancer cells and adipose tissue in promoting cancer progression. Using high-resolution optical and electron microscopy, we have found that breast cancer cells form nanoscale tubular communications with obese adipocytes. Moreover, the cancer cells hijack mitochondria from obese adipocytes. However, coculturing cancer cells and obese adipocytes in the Boyden chamber, allowing exosomal and paracrine communication but blocking direct physical communication, revealed negligible mitochondria transfer. This observation indicates an active transfer of mitochondria via nanotube. A significantly higher rate of mitochondria transfer from obese adipocytes to cancer cells has been observed than non-differentiated pre-adipocytes. The transfer of mitochondria results in an increase in the metabolism of the cancer cells. The mechanistic investigation of the nanotube formation revealed actin's presence as the major component in the nanotube. The exocyst-GTPase protein complex has a prime contribution in actin remodeling and nanotube formation. Inhibition of exocyst-GTPase using a pharmacological inhibitor results in a significant reduction in nanotube-mediated mitochondria transfer. Conclusion: Our goal is to (i) investigate the direct physical connection between adipocytes and cancer cells and the effect on cancer progression and (ii) eliminate mortality related to obesity-associated breast cancer severity by introducing a new therapeutic strategy. Here, we have shown how cancer cells communicate with obese adipocytes and receive additional metabolic power for proliferation. The in vivo investigation of the same is under progress. Citation Format: Tanmoy Saha, Balaaji Baanupriya Srinivasan, Shiladitya Sengupta. Involvement of nanoscale physical communication in obesity-associated breast cancer severity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3935.

Obesity-Associated Breast Cancer: Analysis of Risk Factors and Current Clinical Evaluation.

Several studies show that a significantly stronger association is obvious between increased body mass index (BMI) and higher breast cancer incidence. Additionally, obese and postmenopausal women are at higher risk of all-cause and breast cancer-specific mortality compared with non-obese women with breast cancer. In this context, increased levels of estrogens, excessive aromatization activity of the adipose tissue, overexpression of pro-inflammatory cytokines, insulin resistance, adipocyte-derived adipokines, hypercholesterolemia, and excessive oxidative stress contribute to the development of breast cancer in obese women. Genetic evaluation is an integral part of diagnosis and treatment for patients with breast cancer. Despite trimodality therapy, the four-year cumulative incidence of regional recurrence is significantly higher. Axillary lymph nodes as well as primary lesions have diagnostic, prognostic, and therapeutic significance for the management of breast cancer. In clinical setting, because of the obese population primary lesions and enlarged lymph nodes could be less palpable, the diagnosis may be challenging due to misinterpretation of physical findings. Thereby, a nomogram has been created as the "Breast Imaging Reporting and Data System" (BI-RADS) to increase agreement and decision-making consistency between mammography and ultrasonography (USG) experts. Additionally, the "breast density classification system," "artificial intelligence risk scores," ligand-targeted receptor probes," "digital breast tomosynthesis," "diffusion-weighted imaging," "18F-fluoro-2-deoxy-D-glucose positron emission tomography," and "dynamic contrast-enhanced magnetic resonance imaging (MRI)" are important techniques for the earlier detection of breast cancers and to reduce false-positive results. A high concordance between estrogen receptor (ER) and progesterone receptor (PR) status evaluated in preoperative percutaneous core needle biopsy and surgical specimens is demonstrated. Breast cancer surgery has become increasingly conservative; however, mastectomy may be combined with any axillary procedures, such as sentinel lymph node biopsy (SLNB) and/or axillary lymph node dissection whenever is required. As a rule, SLNB-guided axillary dissection in breast cancer patients who have clinically axillary lymph node-positive to node-negative conversion following neoadjuvant chemotherapy is recommended, because lymphedema is the most debilitating complication after any axillary surgery. There is no clear consensus on the optimal treatment of occult breast cancer, which is much discussed today. Similarly, the current trend in metastatic breast cancer is that the main palliative treatment option is systemic therapy.

FGF1 supports glycolytic metabolism through the estrogen receptor in endocrine-resistant and obesity-associated breast cancer

BackgroundObesity increases breast cancer risk and breast cancer-specific mortality, particularly for people with estrogen receptor (ER)-positive tumors. Body mass index (BMI) is used to define obesity, but it may not be the best predictor of breast cancer risk or prognosis on an individual level. Adult weight gain is an independent indicator of breast cancer risk. Our previous work described a murine model of obesity, ER-positive breast cancer, and weight gain and identified fibroblast growth factor receptor (FGFR) as a potential driver of tumor progression. During adipose tissue expansion, the FGF1 ligand is produced by hypertrophic adipocytes as a stimulus to stromal preadipocytes that proliferate and differentiate to provide additional lipid storage capacity. In breast adipose tissue, FGF1 production may stimulate cancer cell proliferation and tumor progression.MethodsWe explored the effects of FGF1 on ER-positive endocrine-sensitive and resistant breast cancer and compared that to the effects of the canonical ER ligand, estradiol. We used untargeted proteomics, specific immunoblot assays, gene expression profiling, and functional metabolic assessments of breast cancer cells. The results were validated in tumors from obese mice and breast cancer datasets from women with obesity.ResultsFGF1 stimulated ER phosphorylation independently of estradiol in cells that grow in obese female mice after estrogen deprivation treatment. Phospho- and total proteomic, genomic, and functional analyses of endocrine-sensitive and resistant breast cancer cells show that FGF1 promoted a cellular phenotype characterized by glycolytic metabolism. In endocrine-sensitive but not endocrine-resistant breast cancer cells, mitochondrial metabolism was also regulated by FGF1. Comparison of gene expression profiles indicated that tumors from women with obesity shared hallmarks with endocrine-resistant breast cancer cells.ConclusionsCollectively, our data suggest that one mechanism by which obesity and weight gain promote breast cancer progression is through estrogen-independent ER activation and cancer cell metabolic reprogramming, partly driven by FGF/FGFR. The first-line treatment for many patients with ER-positive breast cancer is inhibition of estrogen synthesis using aromatase inhibitors. In women with obesity who are experiencing weight gain, locally produced FGF1 may activate ER to promote cancer cell metabolic reprogramming and tumor progression independently of estrogen.

The Role of Obesity in Breast Cancer Pathogenesis.

Research has shown that obesity increases the risk for type 2 diabetes mellitus (Type 2 DM) by promoting insulin resistance, increases serum estrogen levels by the upregulation of aromatase, and promotes the release of reactive oxygen species (ROS) by macrophages. Increased circulating glucose has been shown to activate mammalian target of rapamycin (mTOR), a significant signaling pathway in breast cancer pathogenesis. Estrogen plays an instrumental role in estrogen-receptor-positive breast cancers. The role of ROS in breast cancer warrants continued investigation, in relation to both pathogenesis and treatment of breast cancer. We aim to review the role of obesity in breast cancer pathogenesis and novel therapies mediating obesity-associated breast cancer development. We explore the association between body mass index (BMI) and breast cancer incidence and the mechanisms by which oxidative stress modulates breast cancer pathogenesis. We discuss the role of glutathione, a ubiquitous antioxidant, in breast cancer therapy. Lastly, we review breast cancer therapies targeting mTOR signaling, leptin signaling, blood sugar reduction, and novel immunotherapy targets.

Fibrocytes enhance mammary gland fibrosis in obesity.

Obesity rates continue to rise, and obese individuals are at higher risk for multiple types of cancer, including breast cancer. Obese mammary fat is a site of chronic, macrophage-driven inflammation, which enhances fibrosis within adipose tissue. Elevated fibrosis within the mammary gland may contribute to risk for obesity-associated breast cancer. To understand how inflammation due to obesity enhanced fibrosis within mammary tissue, we utilized a high-fat diet model of obesity and elimination of CCR2 signaling in mice to identify changes in immune cell populations and their impact on fibrosis. We observed that obesity increased a population of CD11b+ cells with the ability to form myofibroblast-like colonies in vitro. This population of CD11b+ cells is consistent with fibrocytes, which have been identified in wound healing and chronic inflammatory diseases but have not been examined in obesity. In CCR2-null mice, which have limited ability to recruit myeloid lineage cells into obese adipose tissue, we observed reduced mammary fibrosis and diminished fibrocyte colony formation in vitro. Transplantation of myeloid progenitor cells, which are the cells of origin for fibrocytes, into the mammary glands of obese CCR2-null mice resulted in significantly increased myofibroblast formation. Gene expression analyses of the myeloid progenitor cell population from obese mice demonstrated enrichment for genes associated with collagen biosynthesis and extracellular matrix remodeling. Together these results show that obesity enhances recruitment of fibrocytes to promote obesity-induced fibrosis in the mammary gland.

Abstract 1316: Immune cell dysfunction is enhanced in a mouse model of obesity-associated breast cancer lung metastasis

Abstract Obesity is known to worsen the overall prognosis of breast cancer patients. Breast cancer patients with a body mass index (BMI) of ≥30 kg/m2 have an increased risk for metastatic disease compared to patients with a BMI in the normal range. Further studies are necessary to understand the mechanisms driving increased breast cancer metastasis in obese patients, particularly to the lung. Although immune cells like neutrophils and myeloid derived suppressor cells have been studied in breast cancer metastasis of the lung, little is known how adaptive immune cells function in metastatic niche of the lung in obesity. To investigate these gaps, we fed 3-week-old female FVB/N mice either a low-fat diet (LFD) or high-fat diet (HFD) for 16 weeks to induce obesity. We then injected estrogen receptor positive (ER+) TC2 cells into the mammary fat pad. Tumors grew to 0.5 cm in diameter then were surgically removed. Lung tissue was collected 8 weeks after tumor removal to examine progression of metastatic disease, and T cell populations were quantified in metastatic lung tissue from obese and lean mice using flow cytometry. Lungs from obese mice showed a significant increase of total immune cells (CD45) and a decrease in total T cells and natural killer cells (NK) compared with controls. CD3+ cells and CD8+ T cells from obese mice expressed higher levels of programmed cell death protein-1 (PD1), a marker of T cell dysfunction. These results suggest that T cells from the lungs of obese mice may have a greater level of T cell dysfunction than controls. To further investigate how obesity alters the function of T cells, CD45+ cells were sorted from lungs from lean and obese mice with and without metastasis, and gene expression was examined using the Nanostring nCounter Immune Exhaustion panel. Immune cells from the lungs of obese non-tumor-bearing mice showed increased expression of NK exhaustion markers and increased TCR signaling. In metastatic lungs from obese mice, immune cells also showed impaired interferon and tumor necrosis factor signaling and an increase in genes associated with exhaustion in NK cells. Further analysis showed upregulated expression of genes associated with senescence in immune cells from metastatic lungs of obese mice. These data suggest that obesity may increase dysfunctional states of T cells and NK cells, leading to enhanced metastatic growth of breast cancer cells. Citation Format: Abbey E. Williams, Lisa M. Arendt. Immune cell dysfunction is enhanced in a mouse model of obesity-associated breast cancer lung metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1316.

Obesity-mediated upregulation of the YAP/IL33 signaling axis promotes aggressiveness and induces an immunosuppressive tumor microenvironment in breast cancer.

Obesity is a well-known risk factor for breast cancer formation and is associated with elevated mortality and a poor prognosis. An obesity-mediated inflammatory microenvironment is conducive to the malignant progression of tumors. However, the detailed molecular mechanism is still needed to be clarified. Herein, we identified that breast cancer cells from mice with diet-induced obesity exhibited increased growth, invasiveness, and stemness capacities. A transcriptome analysis revealed that expressions of interleukin 33 (IL33) signaling pathway-related genes were elevated in obesity-associated breast cancer cells. Importantly, IL33 expression was significantly associated with the yes-associated protein (YAP) signature, and IL33 was transcriptionally regulated by YAP. Suppression of IL33 reduced tumor migration and invasion, while the addition of IL33 activated nuclear factor (NF)-κB signaling and revived tumor mobility in YAP-silenced cells. Furthermore, suppression of YAP attenuated IL33 expression which was accompanied by relief of obesity-mediated immunosuppression. Clinical analyses showed that IL33 expression was markedly associated with macrophage and regulatory T cell infiltration. These findings reveal a crucial role of the YAP/IL33 axis in promoting aggressiveness and immunosuppression of obesity-associated breast cancer progression.

Adipose Cells Induce Escape from an Engineered Human Breast Microtumor Independently of their Obesity Status.

Obesity is associated with increased breast cancer incidence, recurrence, and mortality. Adipocytes and adipose-derived stem cells (ASCs), two resident cell types in adipose tissue, accelerate the early stages of breast cancer progression. It remains unclear whether obesity plays a role in the subsequent escape of malignant breast cancer cells into the local circulation. We engineered models of human breast tumors with adipose stroma that exhibited different obesity-specific alterations. We used these models to assess the invasion and escape of breast cancer cells into an empty, blind-ended cavity (as a mimic of a lymphatic vessel) for up to sixteen days. Lean and obese donor-derived adipose stroma hastened escape to similar extents. Moreover, a hypertrophic adipose stroma did not affect the rate of adipose-induced escape. When admixed directly into the model tumors, lean and obese donor-derived ASCs hastened escape similarly. This study demonstrates that the presence of adipose cells, independently of the obesity status of the adipose tissue donor, hastens the escape of human breast cancer cells in multiple models of obesity-associated breast cancer. The online version contains supplementary material available at 10.1007/s12195-022-00750-y.

Therapeutic effects of Vernonia amygdalina on the expression of hormone and HER2 receptors in 7, 12-dimethylbenz(a)anthracene-induced breast tumours in obese and non-obese Wistar rats

BackgroundObesity, a risk factor for breast cancer has been shown to be associated with poor response to neoadjuvant chemotherapy in women with breast cancer. Medicinal plants have been used to treat chronic diseases like cancer with little or no side effects. Vernonia amygdalina (VA) is a medicinal plant with anticancer activity. Previous studies on the anticancer potential of V. amygdalina against breast cancer are however entirely in vitro studies. The efficacy of V. amygdalina on obesity-associated breast cancer has also not been investigated in previous studies. This study explored VA’s anti-cancer effects on obesity- and non-obesity-associated 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast tumours in Wistar rats (WRs). MethodThirty female obese and non-obese WRs were studied, each group divided into six subgroups of five. At the 7th postnatal week (p.w), three subgroups were given a subcutaneous injection of DMBA to the breast with two of these three subgroups also commenced on daily oral VA at 250 mg/kg and 500 mg/kg from the 9th p.w. Same doses of VA were administered to two of the subgroups that did not receive DMBA while the last subgroup was placed on placebo from the 9th p.w. Haematoxylin and eosin staining were carried out on the excised breast tumours to evaluate general histoarchitecture, while immunohistochemistry was done for oestrogen (ER), progesterone (PR), and human epidermal growth factor receptor 2 (HER2) expression. ANOVA and Mann-Whitney followed by posthoc tests were used to analyse the data. Alpha level was set at 0.05. ResultsWhile the DMBA-induced tumours were triple-negative in the obese WRs, they were ER, PR HER2-positive in the non-obese group. Vernonia amygdalina was associated with a reduction in cancer cell proliferation in both obese and non-obese groups despite the differences in immunohistochemical profiles of the tumours. Vernonia amygdalina was associated with reversal of the increased ER, PR and HER2 expressions in the breast tumours of the non-obese rats. ConclusionsConclusively, VA had more therapeutic effects on DMBA-induced breast tumours in the non-obese than obese WRs.

Preventing ovariectomy-induced weight gain decreases tumor burden in rodent models of obesity and postmenopausal breast cancer

BackgroundObesity and adult weight gain are linked to increased breast cancer risk and poorer clinical outcomes in postmenopausal women, particularly for hormone-dependent tumors. Menopause is a time when significant weight gain occurs in many women, and clinical and preclinical studies have identified menopause (or ovariectomy) as a period of vulnerability for breast cancer development and promotion.MethodsWe hypothesized that preventing weight gain after ovariectomy (OVX) may be sufficient to prevent the formation of new tumors and decrease growth of existing mammary tumors. We tested this hypothesis in a rat model of obesity and carcinogen-induced postmenopausal mammary cancer and validated our findings in a murine xenograft model with implanted human tumors.ResultsIn both models, preventing weight gain after OVX significantly decreased obesity-associated tumor development and growth. Importantly, we did not induce weight loss in these animals, but simply prevented weight gain. In both lean and obese rats, preventing weight gain reduced visceral fat accumulation and associated insulin resistance. Similarly, the intervention decreased circulating tumor-promoting growth factors and inflammatory cytokines (i.e., BDNF, TNFα, FGF-2), with greater effects in obese compared to lean rats. In obese rats, preventing weight gain decreased adipocyte size, adipose tissue macrophage infiltration, reduced expression of the tumor-promoting growth factor FGF-1 in mammary adipose, and reduced phosphorylated FGFR indicating reduced FGF signaling in tumors.ConclusionsTogether, these findings suggest that the underlying mechanisms associated with the anti-tumor effects of weight maintenance are multi-factorial, and that weight maintenance during the peri-/postmenopausal period may be a viable strategy for reducing obesity-associated breast cancer risk and progression in women.

Abstract P1-10-02: Effect of metformin on metabolic markers associated with breast cancer risk in a phase II clinical trial in overweight/obese premenopausal women

Abstract Background: The increasing rate of obesity in the United States is accompanied by serious health concerns. Obesity increases breast cancer burden and is associated with increased risk of triple-negative breast cancer in premenopausal women and overall poor prognosis in breast cancer patients. There is a need for intervention strategies aiming to reduce obesity-associated dysregulation to attenuate breast cancer risk.Methods: We conducted a Phase II, double-blind, randomized, placebo-controlled clinical trial in overweight/obese premenopausal women with elements of metabolic syndrome to assess the potential of metformin to reduce obesity-associated breast cancer risk. Study participants received metformin (850 mg BID, n = 76) or placebo (n = 75) for 12 months. Fasting blood samples were collected at baseline, 6-months and 12-months from each participant. We analyzed the effects of metformin on circulating levels of insulin/IGF axis, adipokines, and neutrophil-to-lymphocyte ratio in samples collected from this trial. Serum concentrations of insulin, IGF-1, IGFBP-3, leptin and high-molecular weight adiponectin were measured using ELISA immunoassays. Results: The study population included 151 women and had a mean age of 39.5 years, mean body mass index (BMI) was 37.8 and study participants had a large waist and at least one other component of metabolic syndrome. Metformin treatment did not result in significant changes in members of the insulin/IGF axis compared to the placebo group, however, limiting the analysis to participants with detectable metformin in the blood serum resulted in favorable changes in insulin (p=0.0215), HOMA-IR (p<0.001) and a significant increase in IGFBP-3 (p=0.0176) in the metformin group after the intervention. We observed significant decreases in leptin (p=0.0018) and the leptin-to-adiponectin ratio (p=0.0036) in the metformin arm longitudinally. Additionally, we observed a significant reduction in the neutrophil-to-lymphocyte ratio (NLR), a systemic inflammation marker, in the metformin group compared to the placebo group (p=0.0170). Conclusions: We conclude that metformin led to favorable changes in metabolic markers associated with breast cancer risk in the metformin treated participants, however, the changes were not significantly different from the placebo group. The NLR was significantly reduced after metformin intervention compared to the placebo group. More research is needed to understand the effects of metformin on the insulin/IGF axis and adipokines in overweight/obese premenopausal women. Citation Format: Edgar Tapia, Diana Villa-Guilen, Pavani Chalasani, Sara Centuori, Denise J. Roe, Jose Guillen, Catherine Cordova, Liane Pinto, Sherry Chow. Effect of metformin on metabolic markers associated with breast cancer risk in a phase II clinical trial in overweight/obese premenopausal women [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-10-02.

Identification of molecular signatures and pathways of obese breast cancer gene expression data by a machine learning algorithm

Aim: Currently, the obesity epidemic is one of the biggest problems for human health. Obesity is impacted on survival in patients with breast cancer. However, key biomarkers of obesity-related breast cancer risk are still not well known. Thus, using machine learning to identify the most appropriate features in obesity-associated breast cancer patients may improve the predictive accuracy and interpretability of regression models. Methods: In the present study, we identified 23 differentially expressed genes (DEGs) from the GSE24185 transcriptome dataset. Seed genes were identified from DEGs, the co-expression network genes and hub genes of the protein-protein interaction network. Pathway enrichment analysis was performed for DEGs. The Ridge penalty regression model was executed by using P-values of enriched pathways and seed gene pathway association score to obtain the most relevant molecular signatures. The model was performed using 10-fold cross-validation to fit the penalized models. Results: Angiotensin II receptor type 1 (AGTR1), cyclin D1 (CCND1), glutamate ionotropic receptor AMPA type subunit 2 (GRIA2), interleukin-6 cytokine family signal transducer (IL6ST), matrix metallopeptidase 9 (MMP9), and protein kinase CAMP-dependent type II regulatory subunit beta (PRKAR2B) were considered as candidate molecular signatures of obese patients with breast cancer. In addition, RAF-independent MAPK1/3 activation, collagen degradation, bladder cancer, drug metabolism-cytochrome P450, and signaling by Hedgehog pathways in cancer were primarily associated with obesity-associated breast cancer. Conclusion: These genes may be used for risk analysis of the disease progression of obese patients with breast cancer. Corresponding genes and pathways should be validated via experimental studies.

Genetic predisposition to obesity and inflammation in a tri-racial/ethnic breast cancer population

Aim: Multiple genes and genetic variants may contribute to racial/ethnic disparities in obesity-associated breast cancer diagnosis and prognosis. Therefore, we evaluate whether racial/ethnic differences in polygenic risk score (PRS) contribute to obesity and inflammatory biomarker in breast cancer patients. Methods: In a tri-racial/ethnic population of 403 breast cancer patients, 21% African American (AA), 65% Hispanic White (HW), and 14% non-Hispanic White (NHW), we evaluated racial/ethnic differences in obesity PRS, the association between PRS and an inflammatory biomarker C-reactive protein (CRP), and its implication in bariatric surgery eligibility. The obesity PRS was constructed via a weighted risk allele model using 35 obesity-related single nucleotide polymorphisms (SNPs). SAS version 9.3 for Windows (SAS Institute, Cary, NC, USA) was used to perform the logistic regression analysis. Results: About 74% of our study population were overweight or obese. The mean ± SD of obesity PRS was 45.03 ± 10.66 for obese patients and 39.36 ± 8.81 for non-obese patients (P < 0.0001). AA patients had a significantly higher obesity PRS than HW and NHW (P < 0.0001). The obesity PRS significantly correlated with body mass index and CRP levels (P < 0.0001) and was associated with bariatric surgery eligibility (OR = 4.32, 95%CI: 1.89-9.87). Conclusion: In summary, multiple obesity-associated SNPs contribute to racial/ethnic disparities in obesity of breast cancer patients; the obesity PRS has application in identifying breast cancer patients with higher genetic risk for obesity who may benefit from more aggressive weight management, such as bariatric surgery to improve breast cancer clinical outcomes.

Dietary Piperine Suppresses Obesity-Associated Breast Cancer Growth and Metastasis by Regulating the miR-181c-3p/PPARα Axis.

Adipocyte-derived leptin activates multiple oncogenic signaling, leading to breast cancer cell progression and metastasis. Hence, finding effective strategies to inhibit the oncogenic effects of leptin would provide a novel approach for disrupting obesity-associated breast cancer. In the current study, we explored the role of piperine, a major plant alkaloid from Piper nigrum (black pepper), against leptin-induced breast cancer. Piperine treatment significantly inhibited leptin-induced breast cancer cell proliferation, colony formation, migration, and invasion. We found that piperine downregulated the expression of PPARα, a predicted target of miR-181c-3p. Mechanistically, piperine potentiates miR-181c-3p-mediated anticancer potential in leptin-induced breast cancer cells. Interestingly, the knockdown of PPARα reduced the proliferative potential of leptin-induced breast cancer cells. Further, oral administration of piperine inhibited breast tumor growth in diet-induced obese mice, accompanied by the upregulation of miR-181c-3p and downregulation of PPARα expression. Together, piperine represents a potential candidate for further development as an anticancer agent for treating obesity-associated breast cancer.

WISER Survivor Trial: Combined Effect of Exercise and Weight Loss Interventions on Insulin and Insulin Resistance in Breast Cancer Survivors.

Obesity-associated breast cancer recurrence is mechanistically linked with elevated insulin levels and insulin resistance. Exercise and weight loss are associated with decreased breast cancer recurrence, which may be mediated through reduced insulin levels and improved insulin sensitivity. This is a secondary analysis of the WISER Survivor clinical trial examining the relative effect of exercise, weight loss and combined exercise and weight loss interventions on insulin and insulin resistance. The weight loss and combined intervention groups showed significant reductions in levels of: insulin, C-peptide, homeostatic model assessment 2 (HOMA2) insulin resistance (IR), and HOMA2 beta-cell function (β) compared to the control group. Independent of intervention group, weight loss of ≥10% was associated with decreased levels of insulin, C-peptide, and HOMA2-IR compared to 0–5% weight loss. Further, the combination of exercise and weight loss was particularly important for breast cancer survivors with clinically abnormal levels of C-peptide.

Fish oil supplementation increases expression of mammary tumor apoptosis mediators and reduces inflammation in an obesity-associated HER-2 breast cancer model

Obesity is associated with inflammation and has been shown to increase breast cancer severity. The objective of this study was to examine the effect of fish oil (FO) supplementation in obesity-associated mammary tumorigenesis in the MMTV-neu(ndl)-YD5 mouse model of human epidermal growth factor receptor-2 positive BC. Female mice were fed one of three diets for 16 weeks: i) high fat diet [HF, % kacl: 41.2% lard, 18.7% corn oil (CO)], ii) an isocaloric HF plus menhaden FO diet (HF+FO, % kcal: 41.2 lard, 13.4% CO, 5.3% FO), iii) low fat diet (LF, % kcal: 4.7% lard, 6% CO). HF mice had increased body weight, visceral adipose weight and serum hormone concentrations (increased leptin and resistin; decreased adiponectin) versus LF, which was attenuated in the HF+FO group versus HF (P<.05). Compared to HF, tumor onset was delayed in HF+FO and LF mice (P<0.05). Compared to HF, HF+FO reduced mammary tumor multiplicity (-27%), tumor weight (-46%) and total tumor volume (-50%) (P<0.05). Additionally, HF+FO reduced mammary tumor multiplicity (-33%), tumor weight (-39%) and total tumor volume (-60%) versus LF. HF+FO improved mammary tumor apoptosis status with increased expression of pro-apoptotic Bad and decreased expression of anti-apoptotic Bcl-xLmediators versus HF (P<0.05). Additionally, HF+FO decreased tumor protein expression of activated Akt, NFκB p65 and STAT3, versus HF (P<0.05). Tumor mRNA expression of inflammatory mediators TNFα, IL-6 and leptin were reduced in HF+FO, whereas IL-10 expression was increased compared to HF (P<0.05). Collectively these results demonstrate the efficacy of FO supplementation for improving obesity-associated breast cancer outcomes.

Immune checkpoint blockade reprograms systemic immune landscape and tumor microenvironment in obesity-associated breast cancer.

SUMMARYImmune checkpoint blockade (ICB) has improved outcomes in some cancers. A major limitation of ICB is that most patients fail to respond, which is partly attributable to immunosuppression. Obesity appears to improve immune checkpoint therapies in some cancers, but impacts on breast cancer (BC) remain unknown. In lean and obese mice, tumor progression and immune reprogramming were quantified in BC tumors treated with anti-programmed death-1 (PD-1) or control. Obesity augments tumor incidence and progression. Anti-PD-1 induces regression in lean mice and potently abrogates progression in obese mice. BC primes systemic immunity to be highly responsive to obesity, leading to greater immunosuppression, which may explain greater anti-PD-1 efficacy. Anti-PD-1 significantly reinvigorates antitumor immunity despite persistent obesity. Laminin subunit beta-2 (Lamb2), downregulated by anti-PD-1, significantly predicts patient survival. Lastly, a microbial signature associated with anti-PD-1 efficacy is identified. Thus, anti-PD-1 is highly efficacious in obese mice by reinvigorating durable antitumor immunity.

Abstract PS8-27: Consumption of a high-fat diet rich in linoleic acid promotes mammary tumor growth

Abstract Consumption of high-fat diets rich in linoleic acid promotes mammary tumor growth Rong Jin1, Jiaqing Hao1, Edward Sauter2, Bing Li1 1Department of Microbiology and Immunology, University of Louisville, Louisville, KY2Hartford Healthcare Cancer Institute, Hartford, CT *To whom correspondence should be addressed: Bing Li, Department of Microbiology and Immunology, University of Louisville, 505 South Hancock Street, Louisville, KY, 40202. Telephone: 502-852-2678. Email: b.li@louisville.edu. AbstractBackground: The most recent Dietary Guidelines in 2015-2020 for Americans from the U.S. Department of Health and Human Services (DHH) and U.S. Department of Agriculture (USDA) recommends a healthy eating pattern with more oils but less saturated fats. Oils predominantly consist of unsaturated fats with either monounsaturated or polyunsaturated fatty acids (FAs). As high fat diets (HFDs) contribute to obesity, which increases the risk of breast cancer, in this report we evaluate whether the consumption of HFDs rich in different unsaturated fatty acids induces similar degrees of obesity and further determines the impact of different oils on mammary tumor growth using our unique murine mouse models. Hypothesis: Consumption of different oils impacts obesity-associated mammary tumor development. Methods: Weaned C57BL/6 wild type (WT) mice and epidermal fatty acid binding protein (E-FABP)-deficient (genetically depleted E-FABP) female mice were randomly grouped and fed either a safflower oil HFD (45% fat, rich in 18:2 polyunsaturated FAs) or an olive oil HFD (45% fat, rich in 18:1 monounsaturated FAs), or a control low fat diet (LFD). After 5 months on the diets, E0771 mammary tumor cells (0.5 × 106/mouse) were injected into the mammary fat pad and tumor volume was measured at 3-day intervals for tumor growth. Immune cell phenotype and functions were evaluated before and after tumor injection. The student’s t-test and/or ANOVA were used to compare immune cell function, obesity and tumor sizes in WT and E-FABP-/- mice, respectively. Results: Compared to the LFD diet, consumption of either safflower oil HFD or olive oil HFD was able to induce a similar degree of mouse obesity in WT mice. E-FABP deficiency has no obvious impact on HFD-induced mouse weight increase. Interestingly, while safflower oil-induced obesity significantly increased mammary tumor growth, olive oil-induced obesity did not promote mammary tumor growth when compared to LFD-fed lean mice. Immunophenotypic and functional analyses showed that mice on the safflower oil diet exhibited lower numbers of CD8+ T cells with reduced production of TNFa than mice on the olive oil diet or LFD. Moreover, safflower oil-associated tumor growth was compromised in mice genetically lacking of E-FABP expression. Mechanistically, E-FABP expression in T cells, especially in CD8+ T cells, mediated 18:2 linoleic acid-induced ROS production and T cell death, thus leading to impaired anti-tumor immunity in safflower oil-fed obese mice. Impact: Although oils are healthy dietary components as recommended by DHH and USDA, different oils exhibit diverse immunoregulatory effects in vivo. Overconsumption of oils with 18:2 FAs may cause obesity-associated breast cancer development. Citation Format: Rong Jin, Jiaqing Jiaqing, Di Yin, Yanmei Yi, Hua Yuan, Satuer Edward, Bing Li. Consumption of a high-fat diet rich in linoleic acid promotes mammary tumor growth [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS8-27.