FXR Agonism with Bile Acid Mimetic Reduces Pre-Clinical Triple-Negative Breast Cancer Burden

Bariatric surgery is associated with improved outcomes for several cancers, including breast cancer (BC), although the mechanisms mediating this protection are unknown. We hypothesized that elevated bile acid pools detected after bariatric surgery may be factors that contribute to improved BC outcomes. Patients with greater expression of the bile acid receptor FXR displayed improved survival in specific aggressive BC subtypes. FXR is a nuclear hormone receptor activated by primary bile acids. Therefore, we posited that activating FXR using an established FDA-approved agonist would induce anticancer effects. Using in vivo and in vitro approaches, we determined the anti-tumor potential of bile acid receptor agonism. Indeed, FXR agonism by the bile acid mimetic known commercially as Ocaliva ("OCA"), or Obeticholic acid (INT-747), significantly reduced BC progression and overall tumor burden in a pre-clinical model. The transcriptomic analysis of tumors in mice subjected to OCA treatment revealed differential gene expression patterns compared to vehicle controls. Notably, there was a significant down-regulation of the oncogenic transcription factor MAX (MYC-associated factor X), which interacts with the oncogene MYC. Gene set enrichment analysis (GSEA) further demonstrated a statistically significant downregulation of the Hallmark MYC-related gene set (MYC Target V1) following OCA treatment. In human and murine BC analyses in vitro, agonism of FXR significantly and dose-dependently inhibited proliferation, migration, and viability. In contrast, the synthetic agonism of another common bile acid receptor, the G protein-coupled bile acid receptor TGR5 (GPBAR1) which is mainly activated by secondary bile acids, failed to significantly alter cancer cell dynamics. In conclusion, agonism of FXR by primary bile acid memetic OCA yields potent anti-tumor effects potentially through inhibition of proliferation and migration and reduced cell viability. These findings suggest that FXR is a tumor suppressor gene with a high potential for use in personalized therapeutic strategies for individuals with BC.

Bones and guts - Why the microbiome matters

The importance of the gut microbiota in human health has become increasingly apparent in recent years, especially when the relationship between microbiota and host is no longer symbiotic. It has long been appreciated that gut dysbiosis can be detrimental to human health and is associated with numerous disease states. Only within the last decade, however, was the gut microbiota implicated in bone biology. Dubbed osteomicrobiology, this emerging field aims to understand the relationship between the gut microbiome and the bone microenvironment in both health and disease. Importantly, the key to one of the major clinical challenges facing both bone and cancer biologists: bone metastasis, may lie in the field of osteomicrobiology; however the link between gut bacteria and bone metastasis is only beginning to be explored. This review will discuss (i) osteomicrobiology as an emerging field, and (ii) the current understanding of osteomicrobiology in the context of cancer in bone.

A Novel Metastatic Estrogen Receptor-Expressing Breast Cancer Model with Antiestrogen Responsiveness

Most women diagnosed with breast cancer (BC) have estrogen receptor alpha-positive (ER+) disease. The current mouse models of ER+ BC often rely on exogenous estrogen to encourage metastasis, which modifies the immune system and the function of some tissues like bone. Other studies use genetically modified or immunocompromised mouse strains, which do not accurately replicate the clinical disease. To create a model of antiestrogen responsive BC with spontaneous metastasis, we developed a mouse model of 4T1.2 triple-negative (TN) breast cancer with virally transduced ER expression that metastasizes spontaneously without exogenous estrogen stimulation and is responsive to antiestrogen drugs. Our mouse model exhibited upregulated ER-responsive genes and multi-organ metastasis without exogenous estrogen administration. Additionally, we developed a second TN BC cell line, E0771/bone, to express ER, and while it expressed ER-responsive genes, it lacked spontaneous metastasis to clinically important tissues. Following antiestrogen treatment (tamoxifen, ICI 182,780, or vehicle control), 4T1.2- and E0771/bone-derived tumor volumes and weights were significantly decreased, exemplifying antiestrogen responsivity in both cell lines. This 4T1.2 tumor model, which expresses the estrogen receptor, metastasizes spontaneously, and responds to antiestrogen treatment, will allow for further investigation into the biology and potential treatment of metastasis.

Probiotic and Muscadine Grape Extract Interventions Shift the Gut Microbiome and Improve Metabolic Parameters in Female C57BL/6 Mice

Obesity and Western-like diet consumption leads to gut microbiome dysbiosis, which is associated with the development of cardio-metabolic diseases and poor health outcomes. The objective of this study was to reduce Western diet-mediated gut microbial dysbiosis, metabolic dysfunction, and systemic inflammation through the administration of a novel combined intervention strategy (oral probiotic bacteria supplements and muscadine grape extract (MGE)). To do so, adult female C57BL/6 mice were fed a low-fat control or Western-style diet and sub-grouped into diet alone, probiotic intervention, antibiotic treatments, MGE supplementation, a combination of MGE and probiotics, or MGE and antibiotics for 13 weeks. Mouse body weight, visceral adipose tissue (VAT), liver, and mammary glands (MG) were weighed at the end of the study. Fecal 16S rRNA sequencing was performed to determine gut bacterial microbiome populations. Collagen, macrophage, and monocyte chemoattractant protein-1 (MCP-1) in the VAT and MG tissue were examined by immunohistochemistry. Adipocyte diameter was measured in VAT. Immunohistochemistry of intestinal segments was used to examine villi length, muscularis thickness, and goblet cell numbers. We show that dietary interventions in Western diet-fed mice modulated % body weight gain, visceral adiposity, MG weight, gut microbial populations, and inflammation. Intervention strategies in both diets effectively reduced VAT and MG fibrosis, VAT and MG macrophages, adipocyte diameter, and VAT and MG MCP-1. Interventions also improved intestinal health parameters. In conclusion, dietary intervention with MGE and probiotics modulates several microbial, inflammatory, and metabolic factors reducing poor health outcomes associated with Western diet intake.

Anti-CD47 immunotherapy as a therapeutic strategy for the treatment of breast cancer brain metastasis

The presence of cell surface protein CD47 allows cancer cells to evade innate and adaptive immune surveillance resulting in metastatic spread. CD47 binds to and activates SIRPα on the surface of myeloid cells, inhibiting their phagocytic activity. On the other hand, CD47 binds the matricellular protein Thrombospondin-1, limiting T-cell activation. Thus, blocking CD47 is a potential therapeutic strategy for preventing brain metastasis. To test this hypothesis, breast cancer patient biopsies were stained with antibodies against CD47 to determine differences in protein expression. An anti-CD47 antibody was used in a syngeneic orthotopic triple-negative breast cancer model, and CD47 null mice were used in a breast cancer brain metastasis model by intracardiac injection of the E0771-Br-Luc cell line. Immunohistochemical staining of patient biopsies revealed an 89% increase in CD47 expression in metastatic brain tumors compared to normal adjacent tissue (p ≤ 0.05). Anti-CD47 treatment in mice bearing brain metastatic 4T1br3 orthotopic tumors reduced tumor volume and tumor weight by over 50% compared to control mice (p ≤ 0.05) and increased IBA1 macrophage/microglia marker 5-fold in tumors compared to control (p ≤ 0.05). Additionally, CD47 blockade increased the M1/M2 macrophage ratio in tumors 2.5-fold (p ≤ 0.05). CD47 null mice had an 89% decrease in metastatic brain burden (p ≤ 0.05) compared to control mice in a brain metastasis model. Additionally, RNA sequencing revealed several uniquely expressed genes and significantly enriched genes related to tissue development, cell death, and cell migration tumors treated with anti-CD47 antibodies. Thus, demonstrating that CD47 blockade affects cancer cell and tumor microenvironment signaling to limit metastatic spread and may be an effective therapeutic for triple-negative breast cancer brain metastasis.

Reversion of breast epithelial polarity alterations caused by obesity

Molecular links between breast cancer risk factors and pro-oncogenic tissue alterations are poorly understood. The goal of this study was to characterize the impact of overweight and obesity on tissue markers of risk, using normal breast biopsies, a mouse model of diet-induced obesity, and cultured breast acini. Proliferation and alteration of epithelial polarity, both necessary for tumor initiation, were quantified by immunostaining. High BMI (>30) and elevated leptin were associated with compromised epithelial polarity whereas overweight was associated with a modest increase in proliferation in human and mice mammary glands. Human serum with unfavorable adipokine levels altered epithelial polarization of cultured acini, recapitulating the effect of leptin. Weight loss in mice led to metabolic improvements and restored epithelial polarity. In acini cultures, alteration of epithelial polarity was prevented by antioxidants and could be reverted by normalizing culture conditions. This study shows that obesity and/or dietary factors modulate tissue markers of risk. It provides a framework to set target values for metabolic improvements and to assess the efficacy of interventional studies aimed at reducing breast cancer risk.

Metabolic and bariatric surgery and obesity pharmacotherapy for cancer prevention: current status and future possibilities

Obesity is a chronic, relapsing, progressive disease of excess adiposity that increases the risk of developing at least 13 types of cancer. This report provides a concise review of the current state of the science regarding metabolic and bariatric surgery and obesity pharmacotherapy related to cancer risk. Meta-analyses of cohort studies report that metabolic and bariatric surgery is independently associated with a lower risk of incident cancer than nonsurgical obesity care. Less is known regarding the cancer-preventive effects of obesity pharmacotherapy. The recent approval and promising pipeline of obesity drugs will provide the opportunity to understand the potential for obesity therapy to emerge as an evidence-based cancer prevention strategy. There are myriad research opportunities to advance our understanding of how metabolic and bariatric surgery and obesity pharmacotherapy may be used for cancer prevention.

Abstract 3030: Effect of 6 months of bazedoxifene and conjugated estrogen on measures of insulin resistance in postmenopausal women at increased risk for breast cancer

Background: Bazedoxifene 20 mg (BZA) + Conjugated estrogen 0.45 mg (CE) as Duavee™ is FDA approved for treatment of hot-flashes and prevention of osteoporosis. We are investigating 6 months of BZA + CE vs wait list control in a multisite Phase IIB trial for primary prevention of breast cancer in high-risk peri-and postmenopausal women with vasomotor symptoms. Primary endpoints are change in mammographic fibroglandular volume and normal breast epithelial proliferation as assessed by Ki-67. Menopause transition is marked by an increase in insulin resistance and incidence of metabolic syndrome which in turn are implicated in the development of breast cancer. Tamoxifen can induce insulin resistance due to effects on small adipocytes, pancreatic beta cells, and hepatic lipid accumulation. In contrast, preclinical studies suggest that BZA + CE may have favorable effects on insulin resistance, particularly in obese animals. Consequently, we are exploring effects of BZA + CE on measures of insulin resistance in our clinical trial.

Methods: Fasting plasma was assessed for insulin and glucose in a CLIA laboratory the same day as drawn. HOMA-IR (insulin resistance) was computed as insulin (µU/ml) × glucose (mg/dl)]/405) and HOMA-%S (measure of insulin sensitivity) as 100/HOMA-IR. HOMA-IR ≥ 1.9 is considered an indication of early insulin resistance and HOMA-IR >2.8 significant insulin resistance. HOMA-%S values of ≥100% are considered an indication of insulin sensitivity.

Results: 21 women have been randomized in the initial 10 months of accrual at the University of Kansas Cancer Center with 8 women completing the 6 -month randomized period to date. Median age was 53 (48-56), and median BMI was 25 kg/m2 (22-35 kg/m2). All women were normoglycemic. However, 2 women (1 each BZA + CE and wait list) had baseline evidence of insulin resistance by HOMA IR (≥1.9). In the woman randomized to BZA + CE, HOMA-IR improved from 2.29 at baseline to 1.0 at 6 months and HOMA-%S improved from 44 to 100%. There was little change in insulin resistance measures in the woman with baseline insulin resistance randomized to wait list. HOMA-IR was 2.83 at baseline and 2.76 at 6 months and HOMA-%S 35% at baseline and 36% at 6 months. Another waitlist participant with normal baseline HOMA-%S of 141% dropped to 71% at 6 months. Results will be available for 20 study participants at the meeting.

Summary: In our initial accrual group there is no indication that 6 months of BZA +CE is associated with development of insulin resistance. Funded in part by NIH grant CA249437 and Breast Cancer Research Foundation grants BCRF-21-049 and BCRF-22-049.

Citation Format: Carol J. Fabian, Erin D. Giles, Katherine L. Cook, Kandy Powers, Christy Altman, Amy Kreutzjans, Teresa Phillips, Adrian Zelenchuk, Krystal Pittman, Stephen D. Hursting, Bruce Kimler. Effect of 6 months of bazedoxifene and conjugated estrogen on measures of insulin resistance in postmenopausal women at increased risk for breast cancer [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 3030.

Abstract P5-08-14: Blockade of CD47/Thrombospondin-1 signaling increases glycolytic metabolism as a protective mechanism against chemotherapy-associated cardiac injury in a model of Triple-Negative Breast Cancer

Due to advances in diagnosis and treatment, cancer–related mortality has decreased, and by the year 2030, there will be 22 million cancer survivors in the United States. This success comes with an increased incidence of serious adverse effects, mainly in the cardiovascular system. While new treatment modalities are emerging for Triple-negative breast cancer (TNBC), most current strategies include anthracycline-based regimens to manage disease. Therefore, novel strategies are needed to overcome anthracycline-induced cardiotoxicities in this patient population. Activation of the TSP1/CD47 signaling axis is implicated in the progression of heart failure, with reported increases in TSP1 levels following myocardial infarction. Therefore, we examined the potential of CD47 blockade as a strategy to prevent cardiac injury as a consequence of cancer chemotherapy. Our data in a syngeneic orthotopic breast cancer model shows that blockade of CD47 using an in vivo anti-sense phosphodiesterase morpholino (PMO) preserved ejection fraction, fractional shortening, and cardiac output when compared to DOX treatment while preserving oncologic efficacy of chemotherapy. To determine a potential mechanism of cardioprotection, hearts of control and CD47 PMO-treated mice were subjected to RNA sequencing. Gene set enrichment analysis (GSEA) showed significant positive enrichment for metabolic pathways including pyruvate metabolism (NES= 2.3 , p< 0.002), and oxidative phosphorylation (NES=2.0, p< 0.01). During cardiac insult, metabolic flexibility of cardiomyocytes results in metabolic reprogramming from fatty acid oxidation to a glycolytic mechanism to overcome injury. Thus, DOX-associated cardiotoxicity may be mediated by an increase in TSP1 and a decrease in glycolysis, leading to the inability to overcome acute cellular stress. In vitro cellular bioenergetics, analysis revealed that TSP1 caused a dose-dependent reduction in glycolytic flux and glycolytic capacity in cardiac myoblast. This, coupled with preserved cardiac viability of cardiac cells treated with CD47 PMO in the presence of DOX, suggests that TSP1 may act through CD47 to prevent cardiac cell metabolic reprogramming needed to overcome injury. Furthermore, anti-sense experiments with siRNAs to Glut-4 and Hexokinase-II showed that the protection conferred by CD47 is mediated by activating these proteins. Therefore our studies suggest that the TSP1/CD47 axis may be central to the interplay of metabolism to preserve cardiac tissue integrity; thus, targeting this pathway may prevent the onset of chronic cardiac disease due to chemotherapy in cancer patients.

Citation Format: Steven M. Bronson, Jessica D. Mackert, Mitra Kooshki, Adam S. Wilson, Nildris Cruz-Diaz, Pierre L Triozzi, Alexandra Thomas, Katherine L. Cook, David R. Soto-Pantoja. Blockade of CD47/Thrombospondin-1 signaling increases glycolytic metabolism as a protective mechanism against chemotherapy-associated cardiac injury in a model of Triple-Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-08-14.

Abstract P1-02-05: Endocrine-targeted therapies modify the gut microbiome affecting responsiveness in ER+ breast cancer

Background: The microbiome consists of the totality of microorganisms (bacteria, fungi, protist, viruses, and phages) that live on and within the body. Studies implicate the gut bacterial microbiome as a risk factor for estrogen receptor-positive (ER+) breast cancer. While diet is the main contributor to the gut microbiome, medications also shift the bacterial microbiome. We currently do not know whether oral endocrine targeting therapies, such as aromatase inhibitors or tamoxifen shift the gut microbiome. Furthermore, we do not know whether gut microbiome populations can influence drug efficacy. Methods: Fecal samples from human donors were placed into ex-vivo colonic bioreactors for stabilization (n=3). Bioreactors were untreated or treated with letrozole or tamoxifen citrate for 48 hours. Samples were collected, DNA isolated, and metagenomic sequencing performed to determine direct drug-bug interactions. C57BL/6 mice were placed on a healthy control (HC; 21% kcal from fat derived from olive oil and fish oil) or a Western diet (45% kcal from fat derived from corn oil, lard, and milkfat) for 6 weeks. Mice within dietary patterns were randomized and administered control, tamoxifen (TAM; 37 ppm tamoxifen citrate), or an aromatase inhibitor (AI; 5 ppm letrozole) for 16 weeks. Metagenomics sequencing were performed on fecal DNA samples at study endpoint. Female BALB/c mice fed a HC or Western diet were injected with bone metastatic 4T1.2ER+ breast cancer cells. Mice were administered tamoxifen citrate, oral probiotics, or a combination of TAM + probiotics for 3-weeks. Tumor volume, tumor weight, and lung weight were recorded at the end of the study. Hindlimbs were analyzed for metastatic lesions. Results: Metagenomic sequencing from the ex-vivo colonic bioreactors treated with aromatase inhibitors or tamoxifen display differential shifts in several β-glucuronidase-expressing and obesity-associated bacterial species suggesting AI and selective estrogen receptor modulators have varying effects in the gut microbiome that may influence estrogen bioavailability and metabolic parameters. C57BL/6 mice on HC or Western diet treated with AI or TAM also display differences in the microbiota and phage populations with TAM elevating Lactobacillus johnsonii and letrozole increasing Lactococcus lactis bacterial proportional abundance. In the tumor-bearing model, combination of oral Lactobacillus probiotics and TAM significantly reduced tumor weight when compared with the tumor weight in control, TAM, or probiotic treated mice fed a Western diet. Combination of probiotics and TAM also prevented the development of ER+ bone metastatic lesions. Conclusions: Our study indicates oral endocrine therapies differentially affect the gut microbiome and these drug-bug interactions are sensitive to dietary-influenced baseline microbiota populations, which may influence drug efficacy and metabolic outcomes. Furthermore, our preclinical studies suggest oral probiotic supplements may enhance tamoxifen efficacy to reduce tumor growth and metastatic development. Further clinical studies are needed on this topic.

Citation Format: Alana Arnone, Adam S. Wilson, Akiko Chiba, Bethany Kerr, David R. Soto-Pantoja, Alexandra Thomas, Katherine L. Cook. Endocrine-targeted therapies modify the gut microbiome affecting responsiveness in ER+ breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-02-05.

Early-life dietary exposures mediate persistent shifts in the gut microbiome and visceral fat metabolism

In utero dietary exposures are linked to the development of metabolic syndrome in adult offspring. These dietary exposures can potentially impact gut microbial composition and offspring metabolic health. Female BALB/c mice were administered a lard, lard + flaxseed oil, high sugar, or control diet 4 wk before mating, throughout mating, pregnancy, and lactation. Female offspring were offered low-fat control diet at weaning. Fecal 16S sequencing was performed. Untargeted metabolomics was performed on visceral adipose tissue (VAT) of adult female offspring. Immunohistochemistry was used to determine adipocyte size, VAT collagen deposition, and macrophage content. Hippurate was administered via weekly intraperitoneal injections to low-fat and high-fat diet-fed female mice and VAT fibrosis and collagen 1A (COL1A) were assessed by immunohistochemistry. Lard diet exposure was associated with elevated body and VAT weight and dysregulated glucose metabolism. Lard + flaxseed oil attenuated these effects. Lard diet exposures were associated with increased adipocyte diameter and VAT macrophage count. Lard + flaxseed oil reduced adipocyte diameter and fibrosis compared with the lard diet. Hippurate-associated bacteria were influenced by lard versus lard + flax exposures that persisted to adulthood. VAT hippurate was increased in lard + flaxseed oil compared with lard diet. Hippurate supplementation mitigated VAT fibrosis pathology. Maternal high-fat lard diet consumption resulted in long-term metabolic and gut microbiome programming in offspring, impacting VAT inflammation and fibrosis, and was associated with reduced VAT hippurate content. These traits were not observed in maternal high-fat lard + flaxseed oil diet-exposed offspring. Hippurate supplementation reduced VAT fibrosis. These data suggest that detrimental effects of early-life high-fat lard diet exposure can be attenuated by dietary omega-3 polyunsaturated fatty acid supplementation.

Gut and Breast Microbiota as Endocrine Regulators of Hormone Receptor-positive Breast Cancer Risk and Therapy Response

Despite advances in treatment strategies, breast cancer (BC) remains one of the most prevalent cancers worldwide. Recent studies implicate the gut microbiome as a potential risk factor for BC development. Alterations in gut microbial diversity resulting in dysbiosis have been linked to breast carcinogenesis by modulating host immune responses and inflammatory pathways, favoring tumorigenesis and progression. Moreover, gut microbiota populations are different between women with BC vs those that are cancer free, further implicating the role of the gut microbiome in cancer development. This alteration in gut microbiota is also associated with changes in estrogen metabolism, which strongly correlates with BC development. Gut microbiota that express the enzyme β-glucuronidase (GUS) may increase estrogen bioavailability by deconjugating estrogen-glucuronide moieties enabling reabsorption into circulation. Increased circulating estrogens may, in turn, drive estrogen receptor-positive BC. GUS-expressing microbiota also affect cancer therapy efficacy and toxicity by modifying glucuronide-conjugated drug metabolites. Therefore, GUS inhibitors have emerged as a potential antitumor treatment. However, the effectiveness of GUS inhibitors is still exploratory. Further studies are needed to determine how oral endocrine-targeting therapies may influence or be influenced by the microbiota and how that may affect carcinogenesis initiation and tumor recurrence.

Discrete Correlation Summation Clustering Reveals Differential Regulation of Liver Metabolism by Thrombospondin-1 in Low-Fat and High-Fat Diet-Fed Mice

Thrombospondin-1 (TSP1) is a matricellular protein with many important roles in mediating carcinogenesis, fibrosis, leukocyte recruitment, and metabolism. We have previously shown a role of diet in the absence of TSP1 in liver metabolism in the context of a colorectal cancer model. However, the metabolic implications of TSP1 regulation by diet in the liver metabolism are currently understudied. Therefore Discrete correlation summation (DCS) was used to re-interrogate data and determine the metabolic alterations of TSP1 deficiency in the liver, providing new insights into the role of TSP1 in liver injury and the progression of liver pathologies such as nonalcoholic fatty liver disease (NAFLD). DCS analysis provides a straightforward approach to rank covariance and data clustering when analyzing complex data sets. Using this approach, our previous liver metabolite data was re-analyzed by comparing wild-type (WT) and Thrombospondin-1 null (Thbs1-/-) mice, identifying changes driven by genotype and diet. Principal component analysis showed clustering of animals by genotype regardless of diet, indicating that TSP1 deficiency alters metabolite handling in the liver. High-fat diet consumption significantly altered over 150 metabolites in the Thbs1-/- livers versus approximately 90 in the wild-type livers, most involved in amino acid metabolism. The absence of Thbs1 differentially regulated tryptophan and tricarboxylic acid cycle metabolites implicated in the progression of NAFLD. Overall, the lack of Thbs1 caused a significant shift in liver metabolism with potential implications for liver injury and the progression of NAFLD.

Response to immune checkpoint blockade improved in pre-clinical model of breast cancer after bariatric surgery

Bariatric surgery is a sustainable weight loss approach, including vertical sleeve gastrectomy (VSG). Obesity exacerbates tumor growth, while diet-induced weight loss impairs progression. It remains unknown how bariatric surgery-induced weight loss impacts cancer progression or alters response to therapy. Using a pre-clinical model of obesity followed by VSG or diet-induced weight loss, breast cancer progression and immune checkpoint blockade therapy were investigated. Weight loss by VSG or weight-matched dietary intervention before tumor engraftment protected against obesity-exacerbated tumor progression. However, VSG was not as effective as diet in reducing tumor burden despite achieving similar weight and adiposity loss. Leptin did not associate with changes in tumor burden; however, circulating IL-6 was elevated in VSG mice. Uniquely, VSG tumors displayed elevated inflammation and immune checkpoint ligand PD-L1+ myeloid and non-immune cells. VSG tumors also had reduced T lymphocytes and markers of cytolysis, suggesting an ineffective anti-tumor microenvironment which prompted investigation of immune checkpoint blockade. While obese mice were resistant to immune checkpoint blockade, anti-PD-L1 potently impaired tumor progression after VSG through improved anti-tumor immunity. Thus, in formerly obese mice, surgical weight loss followed by immunotherapy reduced breast cancer burden. Finally, we compared transcriptomic changes in adipose tissue after bariatric surgery from patients and mouse models. A conserved bariatric surgery-associated weight loss signature (BSAS) was identified which significantly associated with decreased tumor volume. Findings demonstrate conserved impacts of obesity and bariatric surgery-induced weight loss pathways associated with breast cancer progression.

As the number of people classified as obese rises globally, so do obesity-related health risks. Studies show that people diagnosed with obesity have inflammation that contributes to tumor growth and their immune system is worse at detecting cancer cells. But weight loss is not currently used as a strategy for preventing or treating cancer.

Surgical procedures for weight loss, also known as ‘bariatric surgeries’, are becoming increasingly popular. Recent studies have shown that individuals who lose weight after these treatments have a reduced risk of developing tumors. But how bariatric surgery directly impacts cancer progression has not been well studied: does it slow tumor growth or boost the anti-tumor immune response?

To answer these questions, Sipe et al. compared breast tumor growth in groups of laboratory mice that were obese due to being fed a high fat diet. The first group of mice lost weight after undergoing a bariatric surgery in which part of their stomach was removed. The second lost the same amount of weight but after receiving a restricted diet, and the third underwent a fake surgery and did not lose any weight. The experiments found that surgical weight loss cuts breast cancer tumor growth in half compared with obese mice. But mice who lost the same amount of weight through dietary restrictions had even less tumor growth than surgically treated mice.

The surgically treated mice who lost weight had more inflammation than mice in the two other groups, and had increased amounts of proteins and cells that block the immune response to tumors. Giving the surgically treated mice a drug that enhances the immune system’s ability to detect and destroy cancer cells reduced inflammation and helped shrink the mice’s tumors. Finally, Sipe et al. identified 54 genes which were turned on or off after bariatric surgery in both mice and humans, 11 of which were linked with tumor size.

These findings provide crucial new information about how bariatric surgery can impact cancer progression. Future studies could potentially use the conserved genes identified by Sipe et al. to develop new ways to stimulate the anti-cancer benefits of weight loss without surgery.

Immuno-reactive cancer organoid model to assess effects of the microbiome on cancer immunotherapy

Immune checkpoint blockade (ICB) therapy has demonstrated good efficacy in many cancer types. In cancers such as non-resectable advanced or metastatic triple-negative breast cancer (TNBC), it has recently been approved as a promising treatment. However, clinical data shows overall response rates (ORRs) from ~ 3-40% in breast cancer patients, depending on subtype, previous treatments, and mutation status. Composition of the host-microbiome has a significant role in cancer development and therapeutic responsiveness. Some bacterial families are conducive to oncogenesis and progression, while others aid innate and therapeutically induced anti-tumor immunity. Modeling microbiome effects on anti-tumor immunity in ex vivo systems is challenging, forcing the use of in vivo models, making it difficult to dissect direct effects on immune cells from combined effects on tumor and immune cells. We developed a novel immune-enhanced tumor organoid (iTO) system to study factors affecting ICB response. Using the 4T1 TNBC murine cell line and matched splenocytes, we demonstrated ICB-induced response. Further administration of bacterial-derived metabolites from species found in the immunomodulatory host-microbiome significantly increased ICB-induced apoptosis of tumor cells and altered immune cell receptor expression. These outcomes represent a method to isolate individual factors that alter ICB response and streamline the study of microbiome effects on ICB efficacy.

Diet impacts triple-negative breast cancer growth, metastatic potential, chemotherapy responsiveness, and doxorubicin-mediated cardiac dysfunction

Anthracyclines are standard-of-care chemotherapy for the treatment of triple-negative breast cancer (TNBC). However, high anthracyclines cumulative doses increase heart failure risk. Designing therapeutic strategies that ameliorate cardiac toxicities without compromising oncologic efficacy are important to improve TNBC outcomes and survivorship. The purpose of this study was to determine the impact of diet on TNBC chemotherapeutic responsiveness and development of chemotherapy-induced cardiac damage. Female BALB/c mice fed a control, Western, Mediterranean, or Western + fish oil diet were injected with 1 × 106 4T1-luciferase TNBC into the mammary fat pad. Tumors grew for 21 days before surgical tumor resection, then mice were treated with 3.3 mg/kg i.v. doxorubicin for 3 weeks. Vevo (R) cardiac ultrasound was performed. Female nu/nu mice were placed on diets before 1 × 105  MDA-MB-231-luciferase TNBC were injected via the tail vein to induce the development of lung metastases. Mice were treated with saline or 3.3 mg/kg i.v. doxorubicin for 3 weeks, and the development of metastases visualized by IVIS (R). Consumption of a high-fat diet increased TNBC growth regardless of dietary pattern. Western diet-fed mice developed lung metastases sooner and displayed increased lung metastatic lesion formation, which was not observed in Mediterranean diet-fed mice. Western diet-fed animals displayed worse cardiac function when compared with Mediterranean diet-fed animals. Hearts from Western diet-fed animals displayed increased fibrosis. Diet represents a modifiable component directly impacting tumor growth, antitumor chemotherapy efficacy, and cardiac toxicities. Our data suggest that the Mediterranean diet may reduce lung metastatic lesions formation and prevent the development of cardiac toxicities.

Circulating Immune Bioenergetic, Metabolic, and Genetic Signatures Predict Melanoma Patients' Response to Anti-PD-1 Immune Checkpoint Blockade

PURPOSE

Immunotherapy with checkpoint inhibitors is improving the outcomes of several cancers. However, only a subset of patients respond. Therefore, predictive biomarkers are critically needed to guide treatment decisions and develop approaches to the treatment of therapeutic resistance.

EXPERIMENTAL DESIGN

We compared bioenergetics of circulating immune cells and metabolomic profiles of plasma obtained at baseline from patients with melanoma treated with anti-PD-1 therapy. We also performed single-cell RNA sequencing (scRNAseq) to correlate transcriptional changes associated with metabolic changes observed in peripheral blood mononuclear cells (PBMC) and patient plasma.

RESULTS

Pretreatment PBMC from responders had a higher reserve respiratory capacity and higher basal glycolytic activity compared with nonresponders. Metabolomic analysis revealed that responder and nonresponder patient samples cluster differently, suggesting differences in metabolic signatures at baseline. Differential levels of specific lipid, amino acid, and glycolytic pathway metabolites were observed by response. Further, scRNAseq analysis revealed upregulation of T-cell genes regulating glycolysis. Our analysis showed that SLC2A14 (Glut-14; a glucose transporter) was the most significant gene upregulated in responder patients' T-cell population. Flow cytometry analysis confirmed significantly elevated cell surface expression of the Glut-14 in CD3+, CD8+, and CD4+ circulating populations in responder patients. Moreover, LDHC was also upregulated in the responder population.

CONCLUSIONS

Our results suggest a glycolytic signature characterizes checkpoint inhibitor responders; consistently, both ECAR and lactate-to-pyruvate ratio were significantly associated with overall survival. Together, these findings support the use of blood bioenergetics and metabolomics as predictive biomarkers of patient response to immune checkpoint inhibitor therapy.

Abstract P1-09-03: Omega-3 polyunsaturated fatty acid supplementation shifts the gut and breast microbiome to influence inflammation

Obesity increases the risk of postmenopausal breast cancer. Obesity also influences the gut microbiome. The gut microbiome represents the totality of microorganisms living within the body and can influence the development of many different types of diseases, including breast cancer. Obesity is associated with an increase in the Firmicute-to-Bacteriodetes bacterial phyla ratio in the gut microbiome promoting dysbiosis and inflammation. We previously demonstrated that diet and obesity shift both the gut and breast tissue microbiome using a non-human primate model. To investigate the impact of omega-3 PUFA supplementation on the gut and breast microbiome, we used a combination of a preclinical murine model and human fecal samples collected from overweight and obese postmenopausal women enrolled in a weight loss clinical trial supplemented with placebo or high dose omega-3 PUFA (clinicaltrials.gov identifier: NCT02101970). Female C57BL/6 mice fed a Western (0.2% kcal from omega-3 PUFA) or a Western +omega-3 PUFA diet (1.3% kcal omega-3 PUFA) for 16 weeks demonstrate differences in intestinal permeability as measured by circulating plasma LPS, in vivo FITC-dextran permeability assay, and intestinal tight junction protein ZO-1 gene expression. Elevated LPS bioavailability associated with metabolic endotoxemia has been associated with breast cancer risk. Omega-3 PUFA supplementation shifts the gut and mammary gland (MG) microbiome. 16S sequencing of DNA isolated from matched fecal and MG samples demonstrate that omega-3 PUFA supplementation independently regulated both microbiomes. Moreover, omega-3 PUFA supplementation in a Western diet reduced Firmicute-to-Bacteriodetes ratio in the murine MG tissue. Obese and overweight postmenopausal women (n=46) were enrolled in a weight loss clinical trial (combination of calorie restriction and exercise) and were administered a placebo or 3.25 g/day combined eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids omega-3 PUFA supplements for 6 months. Bacterial sequencing of DNA isolated from fecal collections at baseline and after 6 months of intervention shows significant decrease in Firmicutes-to-Bacteriodetes ratio regardless of intervention group. However, when clustering subjects by relative weight loss and intervention (<10% weight loss on placebo; <10% weight loss on omega-3; >10% weight loss on placebo, or >10% weight loss on omega-3), women in the <10% weight loss on omega-3 PUFA group displayed significant reduction in the Firmicutes-to-Bacteriodetes ratio from baseline that was not observed in the <10% weight loss on placebo group. These data suggest that women who did not achieve substantial weight loss but were supplemented with omega-3 PUFA, show an improved gut microbiome for potential enhancement of health outcomes. Taken together, these data demonstrate that increasing omega-3 PUFA intake to approximately 2% of total daily calories can shift the gut and mammary gland microbiome to a pattern associated with improved intestinal permeability parameters and less chronic inflammation, which in turn is associated with reduced risk of postmenopausal breast cancer.

Citation Format: Katherine L. Cook, Adam S Wilson, David R Soto-Pantoja, Bruce F. Kimler, Shahid Umar, Carol J. Fabian. Omega-3 polyunsaturated fatty acid supplementation shifts the gut and breast microbiome to influence inflammation [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 P1-09-03.

Metabolic Implications of Immune Checkpoint Proteins in Cancer

Expression of immune checkpoint proteins restrict immunosurveillance in the tumor microenvironment; thus, FDA-approved checkpoint inhibitor drugs, specifically PD-1/PD-L1 and CTLA-4 inhibitors, promote a cytotoxic antitumor immune response. Aside from inflammatory signaling, immune checkpoint proteins invoke metabolic reprogramming that affects immune cell function, autonomous cancer cell bioenergetics, and patient response. Therefore, this review will focus on the metabolic alterations in immune and cancer cells regulated by currently approved immune checkpoint target proteins and the effect of costimulatory receptor signaling on immunometabolism. Additionally, we explore how diet and the microbiome impact immune checkpoint blockade therapy response. The metabolic reprogramming caused by targeting these proteins is essential in understanding immune-related adverse events and therapeutic resistance. This can provide valuable information for potential biomarkers or combination therapy strategies targeting metabolic pathways with immune checkpoint blockade to enhance patient response.

A review of research on the intersection between breast cancer and cardiovascular research in the Women's Health Initiative (WHI)

Both obesity and metabolic syndrome are linked to increased incidence of type 2 diabetes, cardiovascular disease (CVD), and cancers of the breast (post-menopausal), and other obesity-related cancers. Over the past 50 years, the worldwide prevalence of obesity and metabolic syndrome has increased, with a concomitant higher incidence of associated co-morbidities and mortality. The precise mechanism linking metabolic syndrome to increased cancer incidence is incompletely understood, however, individual components of metabolic syndrome have been linked to increased breast cancer incidence and worse survival. There is a bidirectional relationship between the risk of CVD and cancer due to a high burden of shared risk factors and higher rates of CVD among cancer survivors, which may be impacted by the pro-inflammatory microenvironment associated with metabolic syndrome and cancer-directed therapies. The Women's Health Initiative (WHI) is an excellent resource to study a dual relationship between cancer and CVD (cardio-oncology) with extensive information on risk factors and long-term outcomes. The purpose of this review is to provide an overview of research on cardio-oncology conducted utilizing WHI data with focus on studies evaluating both breast cancer and CVD including shared risk factors and outcomes after cancer. The review also includes results on other obesity related cancers which were included in the analyses of breast cancer, articles looking at cancer after heart disease (reverse cardio-oncology) and the role of Clonal Hematopoiesis of Indeterminate Potential (CHIP) as a shared risk factor between CVD and cancer. A summary of pertinent WHI literature helps to delineate the direction of future research evaluating the relationship between CVD and other cancer sites, and provides information on the opportunity for other novel analyses within the WHI.

Investigating the role of endogenous estrogens, hormone replacement therapy, and blockade of estrogen receptor-α activity on breast metabolic signaling

Purpose

Menopause is associated with an increased risk of estrogen receptor-positive (ER +) breast cancer. To characterize the metabolic shifts associated with reduced estrogen bioavailability on breast tissue, metabolomics was performed from ovary-intact and ovariectomized (OVX) female non-human primates (NHP). The effects of exogenous estrogen administration or estrogen receptor blockade (tamoxifen treatment) on menopause-induced metabolic changes were also investigated.

Methods

Bilateral ovariectomies were performed on female cynomolgus macaques (Macaca fascicularis) to model menopause. OVX NHP were then divided into untreated (n = 13), conjugated equine estrogen (CEE)-treated (n= 13), or tamoxifen-treated (n = 13) subgroups and followed for 3 years. Aged-matched ovary-intact female NHP (n = 12) were used as a premenopausal comparison group. Metabolomics was performed on snap-frozen breast tissue.

Results

Changes in several different metabolic biochemicals were noted, particularly in glucose and fatty acid metabolism. Specifically, glycolytic, Krebs cycle, acylcarnitines, and phospholipid metabolites were elevated in breast tissue from ovary-intact NHP and OVX + CEE in relation to the OVX and OVX + tamoxifen group. In contrast, treatment with CEE and tamoxifen decreased several cholesterol metabolites, compared to the ovary-intact and OVX NHP. These changes were accompanied by elevated bile acid metabolites in the ovary-intact group.

Conclusion

Alterations in estrogen bioavailability are associated with changes in the mammary tissue metabolome, particularly in glucose and fatty acid metabolism. Changes in these pathways may represent a bioenergetic shift in gland metabolism at menopause that may affect breast cancer risk.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06354-w.

Diet Alters Entero-Mammary Signaling to Regulate the Breast Microbiome and Tumorigenesis

Obesity and poor diet often go hand-in-hand, altering metabolic signaling and thereby impacting breast cancer risk and outcomes. We have recently demonstrated that dietary patterns modulate mammary microbiota populations. An important and largely open question is whether the microbiome of the gut and mammary gland mediates the dietary effects on breast cancer. To address this, we performed fecal transplants between mice on control or high-fat diets (HFD) and recorded mammary tumor outcomes in a chemical carcinogenesis model. HFD induced protumorigenic effects, which could be mimicked in animals fed a control diet by transplanting HFD-derived microbiota. Fecal transplants altered both the gut and mammary tumor microbiota populations, suggesting a link between the gut and breast microbiomes. HFD increased serum levels of bacterial lipopolysaccharide (LPS), and control diet-derived fecal transplant reduced LPS bioavailability in HFD-fed animals. In vitro models of the normal breast epithelium showed that LPS disrupts tight junctions (TJ) and compromises epithelial permeability. In mice, HFD or fecal transplant from animals on HFD reduced expression of TJ-associated genes in the gut and mammary gland. Furthermore, infecting breast cancer cells with an HFD-derived microbiome increased proliferation, implicating tumor-associated bacteria in cancer signaling. In a double-blind placebo-controlled clinical trial of patients with breast cancer administered fish oil supplements before primary tumor resection, dietary intervention modulated the microbiota in tumors and normal breast tissue. This study demonstrates a link between the gut and breast that mediates the effect of diet on cancer. SIGNIFICANCE: This study demonstrates that diet shifts the microbiome in the gut and the breast tumor microenvironment to affect tumorigenesis, and oral dietary interventions can modulate the tumor microbiota in patients with breast cancer. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/14/3890/F1.large.jpg.

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

Immune 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. VIDEO ABSTRACT.

Inhibition of Antiestrogen-Promoted Pro-Survival Autophagy and Tamoxifen Resistance in Breast Cancer through Vitamin D Receptor

We determined how vitamin D receptor (VDR) is linked to disease outcome in estrogen receptor-positive (ER+) breast cancer patients treated with tamoxifen (TAM). Breast cancer patients (n = 581) in four different datasets were divided into those expressing higher (above median) and lower levels of VDR in pretreatment ER+ tumors. Across all datasets, TAM-treated patients with higher pretreatment tumor VDR expression exhibited significantly longer recurrence-free survival. Ingenuity pathway analysis identified autophagy and unfolded protein response (UPR) as top differentially expressed pathways between high and low VDR-expressing ER+ cancers. Activation of VDR with vitamin D (VitD), either calcitriol or its synthetic analog EB1089, sensitized MCF-7-derived, antiestrogen-resistant LCC9 human breast cancer cells to TAM, and attenuated increased UPR and pro-survival autophagy. Silencing of VDR blocked these effects through the IRE1α-JNK pathway. Further, silencing of VDR impaired sensitivity to TAM in antiestrogen-responsive LCC1 cells, and prevented the effects of calcitriol and EB1089 on UPR and autophagy. In a preclinical mouse model, dietary VitD supplementation induced VDR activation and reduced carcinogen-induced ER+ mammary tumor incidence. In addition, IRE1α-JNK signaling was downregulated and survival autophagy was inhibited in mammary tumors of VitD-supplemented mice. Thus, activation of VDR is predictive of reduced risk of breast cancer recurrence in ER+ patients, possibly by inhibiting antiestrogen-promoted pro-survival autophagy.

Diet, obesity, and the gut microbiome as determinants modulating metabolic outcomes in a non-human primate model

BACKGROUND

The objective of this study was to increase understanding of the complex interactions between diet, obesity, and the gut microbiome of adult female non-human primates (NHPs). Subjects consumed either a Western (n=15) or Mediterranean (n=14) diet designed to represent human dietary patterns for 31 months. Body composition was determined using CT, fecal samples were collected, and shotgun metagenomic sequencing was performed. Gut microbiome results were grouped by diet and adiposity.

RESULTS

Diet was the main contributor to gut microbiome bacterial diversity. Adiposity within each diet was associated with subtle shifts in the proportional abundance of several taxa. Mediterranean diet-fed NHPs with lower body fat had a greater proportion of Lactobacillus animalis than their higher body fat counterparts. Higher body fat Western diet-fed NHPs had more Ruminococcus champaneliensis and less Bacteroides uniformis than their low body fat counterparts. Western diet-fed NHPs had significantly higher levels of Prevotella copri than Mediterranean diet NHPs. Western diet-fed subjects were stratified by P. copri abundance (P. copri^HIGH versus P. copri^LOW), which was not associated with adiposity. Overall, Western diet-fed animals in the P. copri^HIGH group showed greater proportional abundance of B. ovatus, B. faecis, P. stercorea, P. brevis, and Faecalibacterium prausnitzii than those in the Western P. copri^LOW group. Western diet P. copri^LOW subjects had a greater proportion of Eubacterium siraeum. E. siraeum negatively correlated with P. copri proportional abundance regardless of dietary consumption. In the Western diet group, Shannon diversity was significantly higher in P. copri^LOW when compared to P. copri^HIGH subjects. Furthermore, gut E. siraeum abundance positively correlated with HDL plasma cholesterol indicating that those in the P. copri^LOW population may represent a more metabolically healthy population. Untargeted metabolomics on urine and plasma from Western diet-fed P. copri^HIGH and P. copri^LOW subjects suggest early kidney dysfunction in Western diet-fed P. copri^HIGH subjects.

CONCLUSIONS

In summary, the data indicate diet to be the major influencer of gut bacterial diversity. However, diet and adiposity must be considered together when analyzing changes in abundance of specific bacterial taxa. Interestingly, P. copri appears to mediate metabolic dysfunction in Western diet-fed NHPs. Video abstract.

Abstract PS6-59: Impact of Cholecystectomy in Breast Cancer Recurrence

Background: Several published studies demonstrate that bile acid metabolites may influence the growth of breast cancer cells in vitro. Our group has shown reduced plasma concentrations of cholic acid and chenodeoxycholic acid (primary bile acids) and deoxycholic acid and lithocholic acid (secondary bile acids) in breast cancer patients that later on develop tumor recurrence. Cholecystectomy reduces the circulating bile acid pool. In patients with prior cholecystectomy, changes in bile acid metabolites may contribute to breast cancer tumorigenesis and recurrence. This study investigates our institutional rate of cholecystectomy in women diagnosed with breast cancer and its impact on breast cancer recurrence.

Methods: A retrospective review of patients with an invasive breast cancer diagnosis between 2014-2015 was conducted. Demographics, preoperative variables, surgical history and clinical outcome data was collected. 5-year disease-free survival (DFS) was compared using a Log-rank (Mantel-Cox) test.

Results: The study included 264 patients with mean age of 60.9. Most were Caucasian (83.5%). The majority were diagnosed at Stage II or lower (80.3%) and had hormone receptor positive, HER2 negative breast cancer (72.9%). Approximately 22.7% of patients had prior cholecystectomy surgery. The only statistically significant heterogeneity in demographic data between patients with and without cholecystectomy was body mass index (BMI). Patients with cholecystectomy had a mean BMI of 33.3, versus 29.1 in patients with intact gallbladders. The 5-year DFS in breast cancer patients with cholecystectomy was 91.6%, versus 97.1% in patients with intact gallbladders (p=0.06).

Conclusion: Women with breast cancer who had a history of cholecystectomy had increased rates of breast cancer recurrence over a 5-year period compared to women with breast cancer with intact gallbladders. Although this result was not statistically significant, a trend was seen. Future study of a larger patient sample size sample may lead to a statistical significant difference. The statistically significant difference in BMI between the two patient groups is likely a confounding factor, given increased BMI is a known risk factor for developing cholecystitis and breast cancer. This data supports existing in vitro studies that bile acids may influence the growth of breast cancer cells. There may be utility in closer follow-up of women with breast cancer and a history of cholecystectomy given the increased rate of breast cancer recurrence in this population.

Citation Format: Isheeta Madeka, Rohin Gawdi, Katherine L Cook, Akiko Chiba. Impact of Cholecystectomy in Breast Cancer Recurrence [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 PS6-59.

Abstract B15: Gut microbiome populations modulate neoadjuvant chemotherapy responsiveness in preclinical triple-negative breast cancer murine model

Triple-negative breast cancer (TNBC) is a highly aggressive subtype with a 5-year survival rate significantly worse when compared to other breast cancer types. There are no targeted therapy options, limiting these patients to cytotoxic chemotherapy regimens. Our group demonstrated increased tumoral Pseudomonas abundance in breast cancer patients receiving neoadjuvant chemotherapy, suggesting that systemic anticancer therapy administration may modulate microbiota populations. The purpose of our study was to determine whether gut microbiota populations correlate with chemotherapeutic responsiveness and may be a predictive biomarker outcome. We wanted to determine the impact of shifting the microbiome on chemotherapy efficacy. To do so, 8-week old female BALB/c mice were injected with 4T1-luciferase cells in the mammary fat pad. Once tumors reached 100 mm3, mice were either untreated (control group), treated with 1x weekly 2.5 mg/kg doxorubicin (DOX) for 4 weeks, or treated with doxorubicin +antibiotics (mixture of streptomycin, ampicillin, and colistin in the drinking water to ablate the microbiome). Tumor size was monitored. Tumors and lungs were collected after the study. Fecal samples were collected at T0 (before treatment) and T4 (after treatment). Mice receiving DOX were stratified into DOX-responders or DOX-nonresponders based upon tumor size. Mice from DOX-responders and DOX +antibiotics groups displayed reduced tumor weight and decreased lung metastatic burden. 16S-bacterial sequencing indicates elevated fecal Ruminococcus correlates with DOX-nonresponsiveness and increased abundance of Oscillospira and Bacteroidales is associated with better therapeutic outcome. Protein analysis of tumor tissue indicates a significant increase in apoptosis in DOX-responders and DOX +antibiotic groups. To determine whether modulating the gut microbiome influences drug responsiveness, BALB/c mice were stratified into a control group or group receiving lard diet-derived fecal transplant (LDFT) by oral gavage. Mice were injected with 4T1-luciferase cells in the mammary fat pad. Once tumors reached 100 mm3, mice were treated with 1x weekly 2.5 mg/kg DOX for 4 weeks. Tumors and lungs were collected at the end of the study. Fecal samples were collected at T0 (before gavage), T3 (after 3 weeks of LDFT and before DOX-treatment), and T7 (at end of study). All tumors from LDFT-group were larger and displayed reduced chemotherapy responsiveness when compared with control animals, suggesting gut microbiome populations can modulate chemotherapy resistance. Taken together, our data demonstrate that chemotherapy efficacy is modulated by gut microbiome and suggest that modulation of the gut microbiome through dietary or probiotic interventions may affect therapeutic outcomes. Moreover, fecal microbiota populations could be used as a predictive biomarker of chemotherapeutic responsiveness.

Citation Format: Kenysha Clear, Adam Wilson, Akiko Chiba, Katherine L. Cook, Alaa Bawaneh. Gut microbiome populations modulate neoadjuvant chemotherapy responsiveness in preclinical triple-negative breast cancer murine model [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr B15.

Research Note: Evaluation of several inoculation procedures for colonization of day-old broiler chicks with Salmonella Heidelberg

Before starting a study with many birds, it helps to know the method of chick inoculation. The objective was to compare 3 methods of Salmonella challenge (oral gavage [OR], intracloacal inoculation [IC], and seeder bird [SB]). Day-old broiler chicks (n = 100) were inoculated with 10⁶ colony forming units (CFU) per chick of a marker strain of Salmonella Heidelberg (SH) with each route of inoculation. Chicks (n = 25) inoculated by each route were placed in floor pens on fresh pine shavings litter. For the seeder batch, 5 colonized chicks, each orally gavaged with 10⁶ CFUs, were placed with 20 pen mates. Two weeks after inoculation, 10 birds from each pen and the 5 inoculated seeder birds were euthanized, the ceca were aseptically removed and macerated with a rubber mallet and weighed, and 3 times (w/v) buffered peptone was added and stomached for 60 s. Serial dilutions were made and plated onto Brilliant Green Sulfa plates containing 200 ppm nalidixic acid. Plates were incubated along with the stomached ceca for 24 h at 37°C. If no colonies appeared on the plates, an additional plate was streaked from the preenriched bag and incubated for 24 h at 37°C. In addition to all seeder birds being positive, the number of SH-positive birds out of 20 sampled in each group was 13, 17, and 7 for OR, IC, and SB, respectively. The level of SH per g of ceca and cecal contents was log (SE) 3.0 (0.7), 2.0 (0.4), and 2.6 (0.4) for OR, IC, and SB, respectively. After enrichment, the number of colonized birds out of 20 was 18, 20, and 10 for OR, IC, and SB, respectively. In conclusion, this study suggests that IC is the method to use to ensure most of the challenged birds are colonized. However, if you prefer to have a smaller percentage of the birds colonized with higher levels, then OR might be better.

Consumption of Mediterranean versus Western Diet Leads to Distinct Mammary Gland Microbiome Populations

Recent identification of a mammary gland-specific microbiome led to studies investigating bacteria populations in breast cancer. Malignant breast tumors have lower Lactobacillus abundance compared with benign lesions, implicating Lactobacillus as a negative regulator of breast cancer. Diet is a main determinant of gut microbial diversity. Whether diet affects breast microbiome populations is unknown. In a non-human primate model, we found that consumption of a Western or Mediterranean diet modulated mammary gland microbiota and metabolite profiles. Mediterranean diet consumption led to increased mammary gland Lactobacillus abundance compared with Western diet-fed monkeys. Moreover, mammary glands from Mediterranean diet-fed monkeys had higher levels of bile acid metabolites and increased bacterial-processed bioactive compounds. These data suggest that diet directly influences microbiome populations outside the intestinal tract in distal sites such as the mammary gland. Our study demonstrates that diet affects the mammary gland microbiome, establishing an alternative mechanistic pathway for breast cancer prevention.

Using a non-human primate model of women’s health, Shively et al. demonstrate that diet plays a critical role in determining microbiota populations in tissues outside the gut, such as the mammary gland. These microbial populations modulate localized bile acid and bacterial-modified metabolites to potentially influence anticancer signaling pathways.

Endoplasmic Reticulum Stress Pathway, the Unfolded Protein Response, Modulates Immune Function in the Tumor Microenvironment to Impact Tumor Progression and Therapeutic Response

Despite advances in cancer therapy, several persistent issues remain. These include cancer recurrence, effective targeting of aggressive or therapy-resistant cancers, and selective treatments for transformed cells. This review evaluates the current findings and highlights the potential of targeting the unfolded protein response to treat cancer. The unfolded protein response, an evolutionarily conserved pathway in all eukaryotes, is initiated in response to misfolded proteins accumulating within the lumen of the endoplasmic reticulum. This pathway is initially cytoprotective, allowing cells to survive stressful events; however, prolonged activation of the unfolded protein response also activates apoptotic responses. This balance is key in successful mammalian immune response and inducing cell death in malignant cells. We discuss how the unfolded protein response affects cancer progression, survival, and immune response to cancer cells. The literature shows that targeting the unfolded protein response as a monotherapy or in combination with chemotherapy or immunotherapies increases the efficacy of these drugs; however, systemic unfolded protein response targeting may yield deleterious effects on immune cell function and should be taken into consideration. The material in this review shows the promise of both approaches, each of which merits further research.

One Health and antimicrobial resistance, a United States perspective

Antimicrobial drugs are a precious resource, responsible for saving millions of lives since their discovery. Unfortunately, some antimicrobials are rapidly losing their effectiveness due to the development and spread of antimicrobial resistance (AMR), a multi-faceted and complex problem affecting humans, animals, plants and the environment. While AMR is a global problem, in this paper, the authors briefly highlight some ongoing efforts in the United States of America aimed at integrating a One Health approach into policies and programmes that address this important health threat.

Metabolomic Analysis Reveals Unique Biochemical Signatures Associated with Protection from Radiation Induced Lung Injury by Lack of cd47 Receptor Gene Expression

The goal of this study was to interrogate biochemical profiles manifested in mouse lung tissue originating from wild type (WT) and cd47 null mice with the aim of revealing the in vivo role of CD47 in the metabolic response to ionizing radiation, especially changes related to the known association of CD47 deficiency with increased tissue viability and survival. For this objective, we performed global metabolomic analysis in mouse lung tissue collected from (C57Bl/6 background) WT and cd47 null mice with and without exposure to 7.6 Gy whole body radiation. Principal component analysis and hierarchical clustering revealed a consistent separation between genotypes following radiation exposure. Random forest analysis also revealed a unique biochemical signature in WT and cd47 null mice following treatment. Our data show that cd47 null irradiated lung tissue activates a unique set of metabolic pathways that facilitate the handling of reactive oxygen species, lipid metabolism, nucleotide metabolism and nutrient metabolites which may be regulated by microbial processing. Given that cd47 has pleiotropic effects on responses to ionizing radiation, we not only propose this receptor as a therapeutic target but postulate that the biomarkers regulated in this study associated with radioprotection are potential mitigators of radiation-associated pathologies, including the onset of pulmonary disease.

Silver nanoparticles selectively treat triple-negative breast cancer cells without affecting non-malignant breast epithelial cells in vitro and in vivo

Silver nanoparticles (AgNPs) show promise for treatment of aggressive cancers including triple-negative breast cancer (TNBC) in preclinical cancer models. For clinical development of AgNP-based therapeutics, it will be necessary to clearly define the specific physicochemical features of the nanoparticles that will be used, and to tie these properties to biological outcomes. To fill this knowledge gap, we performed thorough structure/function, mechanistic, safety, and efficacy studies to assess the potential for AgNPs to treat TNBC. We establish that AgNPs, regardless of size, shape, or stabilizing agent, are highly cytotoxic to TNBC cells at doses that are not cytotoxic to non-malignant breast epithelial cells. In contrast, TNBC cells and non-malignant breast epithelial cells are similarly sensitive to exposure to silver cation (Ag+), indicating that the nanoparticle formulation is essential for the TNBC-specific cytotoxicity. Mechanistically, AgNPs are internalized by both TNBC and non-malignant breast cells, but are rapidly degraded only in TNBC cells. Exposure to AgNPs depletes cellular antioxidants and causes endoplasmic reticulum stress in TNBC cells without causing similar damage in non-malignant breast epithelial cells. AgNPs also cause extensive DNA damage in 3D TNBC tumor nodules in vitro, but do not disrupt the normal architecture of breast acini in 3D cell culture, nor cause DNA damage or induce apoptosis in these structures. Lastly, we show that systemically administered AgNPs are effective at non-toxic doses for reducing the growth of TNBC tumor xenografts in mice. This work provides a rationale for development of AgNPs as a safe and specific TNBC treatment.

Abstract 2835: Breast tumor microbiota populations are modulated by chemotherapy and may be indicative of outcome

Breast tumors were identified to have their own microbiota population distinct from mammary gland tissue. Breast cancer patients that present in the clinic with larger tumors often undergo neo-adjuvant chemotherapy to reduce tumor burden before surgery. The purpose of our study was to evaluate whether chemotherapy can modulate the tumor microbiome and the potential impact of microbes in the development of distant metastases. Using snap-frozen aseptically collected breast tumor tissue from women that underwent neo-adjuvant chemotherapy or women with no prior therapy at time of surgery, we performed 16S rRNA sequencing to identify tumoral bacterial populations. We also stained breast tumor microarrays (normal breast tissue, primary breast tumor, and lymph node metastases) to confirm presence of identified microbiota. Our data indicates that chemotherapy administration significantly increased breast tumor Pseudomonas and reduced the proportional abundance of Streptococcus. Primary breast tumors from patients that developed distant metastases later on in life (regardless of therapy) displayed increased tumoral abundance of Acinetobacter, Brevundimonas, and Staphylococcus. Stratifying patients based upon BMI indicates that obesity modulates breast tumor microbiota populations and needs to be considered in analyses. Furthermore, we confirm presence of Pseudomonas in breast tumor tissue by immunohistochemical staining. Our results indicate breast tumor microbiota populations can be modified by chemotherapy and specific microbes correlate with tumor recurrence. Further studies with a larger patient cohort may provide greater insights into the role of microbiota in therapeutic outcome and for the development of novel bacterial biomarkers that could predict distant metastases.

Citation Format: Akiko Chiba, Alaa Bawaneh, Christine Velazquez, Edward Levine, Katherine L. Cook. Breast tumor microbiota populations are modulated by chemotherapy and may be indicative of outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2835.

Abstract 650: Gut microbiota population may be used to predict chemotherapeutic responsiveness in triple negative breast cancer

Triple negative breast cancer (TNBC) accounts for 15-20% of all breast cancers and predominately affects young and minority women. TNBC is characterized by a high recurrence rate, with about 34% of TNBC patients relapsing around 2.6 years. This type of breast cancer lacks targeted therapy options and is limited to chemotherapy treatment options. The purpose of our study was to determine whether gut microbiota populations correlate with chemotherapeutic responsiveness and may be a predictive biomarker of outcome. Moreover, we want to determine the impact of targeting the microbiome on chemotherapy efficacy. In this study, 8-week old female BALB/c mice were injected with TNBC 4T1-luciferase cells into their L4/5 mammary fat pad. Once tumors developed, mice were either untreated (control group), treated with 1 x weekly 2.5 mg/kg IV doxorubicin (DOX), or treated with doxorubicin + antibiotics (mixture of streptomycin, ampicillin, and colistin in the drinking water to ablate host bacterial populations). Tumors were collected at the end of the study. Fecal samples were collected at time point 0 weeks (T0; before therapy when tumors were approximately 100 mm3) and time point 4 weeks (T4; after treatment). We subdivided the doxorubicin treated group into DOX-responders (tumors stopped growing or shrank) or DOX-nonresponders (tumors continued to grow on treatment). Tumors from the DOX-responders and DOX + antibiotics groups were significantly smaller and mice from these groups displayed reduced lung weight, suggesting decreased lung metastatic burden. 16S-bacterial sequencing analysis was performed on breast tumor tissue and feces. We demonstrate that at T0, elevated fecal Ruminococcus correlates with DOX-nonresponsiveness. Furthermore, at T4, we show increased fecal abundance of Oscillospira and Bacteroidales are associated with better therapeutic outcome. Protein analysis of primary 4T1 breast tumor tissue indicate a significant elevation of apoptosis (cleaved caspase-3 protein levels) in DOX-responders and DOX + antibiotic treated mice. We also stained breast tumor tissue and lung tissue for bacteria to confirm presence of microbiota by immunohistochemistry. Taken together our data demonstrates that chemotherapy efficacy is modulated by the microbiome. Moreover, fecal microbiota populations could be used as a predictive biomarker of chemotherapeutic responsiveness and suggests that modulation of the gut microbiome through dietary or probiotic interventions may affect therapeutic outcomes.

Citation Format: Alaa Bawaneh, Adam S. Wilson, Kenysha YJ Clear, Akiko Chiba, Katherine L. Cook. Gut microbiota population may be used to predict chemotherapeutic responsiveness in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 650.

Managing Beef Backgrounding Residual Soil Contaminants by Alum and Biochar Amendments

Heavy manure-derived contamination of soils can make animal congregating areas nonpoint sources for environmental pollution. In situ soil stabilization is a cost-effective management strategy with a focus on lowering contaminant availability and limiting release to the environment. Soil stabilizing amendments can help mitigate the negative environmental impacts of contaminated soils. In this 2-yr study, we examined the effects of adding no amendment (control) or treating with alum [Al (SO)⋅18HO] or biochar as soil amendments on Mehlich-3 extractable soil P, Cu, and Zn contents, antimicrobial monensin concentrations, total bacteria (16S ribosomal RNA [rRNA] gene), antibiotic resistance genes (1 and B), and Class 1 integrons (1) in an abandoned beef backgrounding setting. The alum reduced soil P (1374 to 1060 mg kg), Cu (7.7 to 3.2 mg kg), and Zn (52.4 to 19.6 mg kg) contents. Both alum and biochar reduced monesin concentrations (1.8 to 0.7 and 2.1 to 1.1 ng g, respectively). All the treatments harbored consistent 16 rRNA concentrations (10 copies g) throughout. The B gene concentration (10 copies g) was lower than either the 1 or the 1 genes (10 copies g), regardless of treatments. However, concentrations of all genes in the soils of animal congregation areas were higher than those in background soils with the least animal impact. In contrast with the effect on other contaminants, the effect of soil amendments on bacteria with antibiotic resistance genes was not biologically significant. Future research should be directed toward evaluating effective alternative methods to mitigate these bacterial populations.

Combination of anthracyclines and anti-CD47 therapy inhibit invasive breast cancer growth while preventing cardiac toxicity by regulation of autophagy

BACKGROUND

A perennial challenge in systemic cytotoxic cancer therapy is to eradicate primary tumors and metastatic disease while sparing normal tissue from off-target effects of chemotherapy. Anthracyclines such as doxorubicin are effective chemotherapeutic agents for which dosing is limited by development of cardiotoxicity. Our published evidence shows that targeting CD47 enhances radiation-induced growth delay of tumors while remarkably protecting soft tissues. The protection of cell viability observed with CD47 is mediated autonomously by activation of protective autophagy. However, whether CD47 protects cancer cells from cytotoxic chemotherapy is unknown.

METHODS

We tested the effect of CD47 blockade on cancer cell survival using a 2-dimensional high-throughput cell proliferation assay in 4T1 breast cancer cell lines. To evaluate blockade of CD47 in combination with chemotherapy in vivo, we employed the 4T1 breast cancer model and examined tumor and cardiac tissue viability as well as autophagic flux.

RESULTS

Our high-throughput screen revealed that blockade of CD47 does not interfere with the cytotoxic activity of anthracyclines against 4T1 breast cancer cells. Targeting CD47 enhanced the effect of doxorubicin chemotherapy in vivo by reducing tumor growth and metastatic spread by activation of an anti-tumor innate immune response. Moreover, systemic suppression of CD47 protected cardiac tissue viability and function in mice treated with doxorubicin.

CONCLUSIONS

Our experiments indicate that the protective effects observed with CD47 blockade are mediated through upregulation of autophagic flux. However, the absence of CD47 in did not elicit a protective effect in cancer cells, but it enhanced macrophage-mediated cancer cell cytolysis. Therefore, the differential responses observed with CD47 blockade are due to autonomous activation of protective autophagy in normal tissue and enhancement immune cytotoxicity against cancer cells.

Abstract 3528: Anti-CD47 immunotherapy regulates T cell metabolism and hypoxia in the tumor microenvironment

Dysfunction of infiltrating CD8+ effector T cells can be induced by hypoxia and aberrant tumor metabolite uptake in the microenvironment causing an “exhausted” T cell phenotype that limits anti-tumor immunosurveilance. Hence- therapeutic strategies aimed at improving T cell bioenergetics have the potential to reinvigorate T cell responses to reduce tumor burden. CD47 is a widely expressed receptor that controls phagocytic activity by engaging its counter receptor, SIRPα, in macrophages. Also autonomously or by binding to its ligand Thrombospondin-1 CD47 activation can control cell fate under stress. Our prior work shows that targeting CD47 on CD8+ T cells enhanced cytotoxicity against cancer cells. Moreover, depletion of CD8+ T cells in murine models reversed the anti-tumor effect of anti-CD47 therapy. Our new data shows that targeting CD47 reduced the growth of B16 melanoma tumors by approximately 50% (1607 ± 213.7, saline vs. 815.1 ± 67.8, CD47 (-) *p<0.02 n=5-6). Further examination of tumors by live photoacoustic imaging showed that tumors of animals treated with anti-CD47 had reduction in oxygen tension and reduced vascularity when compared to control. This suggests that the reduction in tumor hypoxia by CD47 may shift metabolic competition in the microenvironment to increase metabolite availability allowing optimal activation of cytotoxic T cells. Cell respirometry measurements using an Agilent Seahorse bioanalyzer showed increased levels of mitochondrial function and glycolytic flux in CD47 null T cells when compared to WT. Moreover, these cells showed increased mitochondrial density and increased levels of the mitochondrial biogenesis regulator, PGC1-a. Treatment with CD47 antibody enhanced Pmel-1 CD8+ T cell effector function by reducing B16 melanoma target cell viability by over 60%. Anti-CD47 treatment of these T cells also resulted in upregulation of cell bioenergetics, suggesting that targeting CD47 may impact T cell metabolism to enhance cytotoxic activity against cancer cells. Therefore, our studies show a new role of CD47 immunotherapy regulating immunometabolism of T cells to enhance effector function which may lead to improvement of clinical outcomes in melanoma patients.

Citation Format: Yismelin R. Feliz-Mosquea, Elizabeth Stirling, Katherine L. Cook, Adam Wilson, Manish Bharadwaj, Anthony J. Molina, Liliya Yamaleyeva, Pierre L. Triozzi, David R. Soto-Pantoja. Anti-CD47 immunotherapy regulates T cell metabolism and hypoxia in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3528.

Abstract 449: Targeting PKR-like endoplasmic reticulum kinase modulates metabolism to promote T-cell effector function and PD1 immunotherapy responsiveness

The development of immunotherapy is a major recent advance in clinical oncology. However the majority of patients do not respond and those who do, experience resistance and relapse. Therefore, understanding the molecular mechanisms of immune checkpoint inhibitor resistance is critical to develop combinatorial drug strategies to potentiate therapeutic responsiveness to reduce mortality. Highly secretory cells, such as T-cells, have a larger endoplasmic reticulum (ER) to handle the increased protein translation capacity required by the cell. Therefore, T-cells may be highly sensitive to ER stress. The high nutrient needs of the tumor deplete resources in the microenvironment subjugating infiltrating T-cells to reduced nutrient availability resulting in stress. Our data indicate that co-culturing melanoma cells with T-cells increase T-cell specific unfolded protein response (UPR) signaling. Stimulating ER stress decreased cytolytic T-cell function in TALL-104 T-cells, enabling Mun2b melanoma survival. Knockdown of PERK restored T-cell killing capacity in ER stress induced cells. In an ex-vivo model of antigen-specific mediated T-cell death, Pmel-1 T-cells stimulated with gp100 displayed increased B16 melanoma killing when treated with GSK2606414 (a small molecule PERK inhibitor). PERK inhibition also elevated glycolysis proteins and mitochondrial bioenergetics in T-cells, suggesting PERK inhibition increases T-cell metabolism. As proof-of-concept, we determined the effect of PERK inhibition in a syngeneic B16 melanoma model. Male C57/Bl6 mice were inoculated with B16 melanoma cells. At 5 days post injection, mice were treated with a control IgG, antisense morpholino targeting PERK, PD1 antibody, or a combination of PERK morpholino and PD1 antibody. PERK morpholino treatment alone was sufficient to reduce tumor volume by 46.5%. PD1 antibody therapy alone reduced tumor volume by 47.4%. The combination of PD1 antibody and PERK targeting therapy significantly reduced B16 melanoma tumor volume by 64.5% demonstrating that targeting PERK in vivo enhanced immunocheckpoint therapy efficacy. Treated B16 tumors were homogenized and infiltrating T-cells isolated by flow cytometry. Gated CD3+ infiltrating leukocytes were then counted for CD8 and PD1 expression. Tumor infiltrating CD8+ T-cells doubled with PERK inhibition alone, giving further proof indicating that PERK may be a novel immune checkpoint target. Small molecule PERK inhibitors were previously shown to cause β-islet damage and insulin resistance; therefore we tested the effect of our PERK morpholino on glucose tolerance in the B16 melanoma model. PERK morpholino treatment had no overall impact on glucose tolerance and therefore may be a novel therapeutic to induce T-cell metabolism and potentiate immune checkpoint therapy efficacy with reduced off-target toxicities.

Citation Format: David R. Soto-Pantoja, Yismeilin R. Feliz-Mosquea, Kenysha YJ Clear, Adam S. Wilson, Katherine L. Cook. Targeting PKR-like endoplasmic reticulum kinase modulates metabolism to promote T-cell effector function and PD1 immunotherapy responsiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 449.

Mitochondrial autophagosomes as a mechanism of drug resistance in breast carcinoma

We have previously described the process by which mitochondria donate their membranes for the formation of autophagosomes, and in this study we show that the same process could be involved in drug sequestration and exocytosis resulting in multidrug-resistant cancerous cells. We examine the implications of mitochondrial vesicle formation of mitoautophagosomes (MAPS) in response to the cytotoxic drug MKT-077, which targets mortalin, in a drug-resistant breast carcinoma cell line overexpressing P-glycoprotein (P-gp). The breast cancer cell line MCF-7Adr is derived from MCF-7, but differs from its ancestral line in tolerance of MKT-077-induced mitochondrial toxicity. Our ultrastructural observations suggest that autophagy in the MCF-7Adr cells entails regional sequestration of MKT077 in multilamellar LC3-labeled MAPS, which then separate from their mitochondria, and fuse with or engulf each other. MAPS appeared to be migrating through the cytoplasm and fusing with the plasma membrane, thus carrying out exocytotic secretion. This mechanism, which seems ineffective in the ancestral cell line, provides a resistance mechanism for MKT-077 by enhancing the efflux process of the cells. After 8 hr of MKT-077 exposure, a fraction of the resistant cells appeared viable and contained larger number of smaller sized mitochondria. Mitoautophagosomes, therefore, provide a potentially novel model for multidrug resistance in cancerous cells and may contribute to the P-gp efflux process.

"UPRegulation" of CD47 by the endoplasmic reticulum stress pathway controls anti-tumor immune responses

We recently demonstrated that targeting the unfolded protein response (UPR) protein GRP78 down-regulates CD47 expression, resulting in increased tumor macrophage infiltration and inhibited resistance to anti-estrogen therapy. We now show new data indicating that anti-estrogen therapy regulates CD47 expression and implicates its ligand, thrombospondin-1, in regulation of tumor macrophage infiltration. Moreover, GRP78 and CD47 co-expression is associated with poor prognosis in breast cancer patients, suggesting the existence of crosstalk between UPR and immunity that regulates therapeutic responses in breast cancer.

Endoplasmic Reticulum Stress Protein GRP78 Modulates Lipid Metabolism to Control Drug Sensitivity and Antitumor Immunity in Breast Cancer

The unfolded protein response is an endoplasmic reticulum stress pathway mediated by the protein chaperone glucose regulated-protein 78 (GRP78). Metabolic analysis of breast cancer cells shows that GRP78 silencing increases the intracellular concentrations of essential polyunsaturated fats, including linoleic acid. Accumulation of fatty acids is due to an inhibition of mitochondrial fatty acid transport, resulting in a reduction of fatty acid oxidation. These data suggest a novel role of GRP78-mediating cellular metabolism. We validated the effect of GRP78-regulated metabolite changes by treating tumor-bearing mice with tamoxifen and/or linoleic acid. Tumors treated with linoleic acid plus tamoxifen exhibited reduced tumor area and tumor weight. Inhibition of either GRP78 or linoleic acid treatment increased MCP-1 serum levels, decreased CD47 expression, and increased macrophage infiltration, suggesting a novel role for GRP78 in regulating innate immunity. GRP78 control of fatty acid oxidation may represent a new homeostatic function for GRP78. Cancer Res; 76(19); 5657-70. ©2016 AACR.

Abstract 1704: UPR signaling promotes T-cell dysfunction to prevent immune-mediated cancer cell killing and immune checkpoint therapy resistance

A critical point in cancer progression is evading recognition by the immune system. Cancer cells accomplish this by stimulating immune checkpoint signals on effector T-cells. In patients with advanced melanoma treated with immune checkpoint inhibitors, 3-year survival increased by 20%. While immune checkpoint therapies are the new first treatment option for advanced melanoma in over a decade, their efficacy is limited because resistance often develops. Understanding the molecular mechanisms of immune checkpoint inhibitor resistance is critical to develop combinatorial drug therapy to potentiate therapeutic responsiveness. The unfolded protein response (UPR) is an endoplasmic reticulum (ER) stress pathway activated when unfolded/misfolded proteins accumulate within the ER. Highly secretory cell types, such as T-cells, have larger ER cell compartments and elevated UPR components to deal with the increased protein synthesis/folding required by these cell types. Therefore, these cell types may be highly sensitive to ER stress. Our data demonstrates elevated UPR signaling components as a driver of T-cell exhaustion/dysfunction. Using a previously established T-cell exhaustion protocol, we stimulated naïve T-cells with antibodies to CD3/CD28 for 5 days and co-cultured them with MDA-MB-231 breast cancer cells, Mun2b melanoma cell line, or CMI patient-derived melanoma cell line. Exhausted T-cells displayed an increased PD-1 and PERK expression, suggesting that UPR signaling is activated during T-cell exhaustion. Treatment of naïve T-cells with DTT, a chemical agent that stimulates ER stress, also induced PD-1 and PERK compared with vehicle-treated T-cells. Gene expression analysis of T-cells indicate that co-culture with cancer cells, not CD3/CD28 activation, elevates T-cell UPR gene expression. Furthermore, induction of ER stress through low-dose DTT treatment decreased cytotoxic T-cell mediated cancer cell death, further supporting our hypothesis of ER stress inducing T-cell exhaustion. Inhibition of PERK by RNAi in TALL-104, a human cytotoxic T-cell line, enhanced T-cell mediated cancer cell clearance when exposed to ER stress-inducing agents, suggesting that PERK may represent a novel target to prevent T-cell exhaustion or restore T-cell effector capabilities. PERK inhibition in the patient-derived melanoma cells did not negatively affect T-cell-mediated killing, suggesting that systemic PERK inhibition may be an effective therapeutic strategy to enhance anti-tumor immune responses. Matched PBMC from melanoma patients before treatment or after ipilimumab therapy resistance indicated increased UPR signaling components in PBMC samples from patients after ipilimumab resistance when compared with PBMC samples before therapy, supporting a novel role UPR signaling in anti-CTLA4 therapy resistance.

Citation Format: Yismeilin R. Feliz Mosquea, David R. Soto Pantoja, Adam Wilson, Pierre L. Triozzi, Katherine L. Cook. UPR signaling promotes T-cell dysfunction to prevent immune-mediated cancer cell killing and immune checkpoint therapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1704. doi:10.1158/1538-7445.AM2017-1704

Abstract P2-04-06: Targeting of the unfolded protein response signaling arms differentially regulates macrophage proliferation, plasticity, and breast cancer cell clearance

The unfolded protein response (UPR) is an endoplasmic reticulum stress pathway controlled by the protein chaperone, glucose-regulated protein 78 (GRP78), to mediate inositol-requiring enzyme 1 (IRE1), PKR-like endoplasmic reticulum kinase (PERK), and activating transcription factor-6 (ATF6) signaling. UPR signaling has been shown to be upregulated in many different types of cancers, including breast cancer and melanoma, and is associated with the development of therapeutic resistance. These data suggest the importance of targeting UPR signaling as a possible cancer therapy. We have previously shown GRP78 to be upregulated in human breast tumor samples and leads to endocrine targeted therapy resistance. We recently showed inhibiting GRP78 in human orthotopic xenografts potentiates tamoxifen therapy effectiveness in sensitive tumors and restores endocrine therapy responsiveness in resistant tumors. In these GRP78-inhibited tumors there was a significant increase of CD68 positive macrophage population, suggesting that targeting UPR signaling has critical effects on the tumor microenvironment. Therefore, consideration of each UPR signaling component and how it effects the different cellular compartments of the tumor microenvironment need to be investigated to optimally induce both an antitumor immune effect and inhibit tumor epithelial cell growth. We now show deletion of GRP78, IRE1, and PERK through RNAi differentially regulates macrophage polarization. Specifically, PERK inhibition enhances macrophage proliferation and macrophage-mediated phagocytosis of 4T1 breast cancer cells, but not GRP78 or IRE1 inhibition. Targeting UPR signaling in the breast cancer cells also differentially affected macrophage cytolytic capacity; Specific breast cancer cell inhibition of IRE1 or GRP78 enhanced macrophage-mediated phagocytosis. Conditioned media from control or GRP78 silenced ZR-75-1 breast cancer cells indicated reciprocal regulation of CD206 and CD80; suggesting regulation of macrophage plasticity by GRP78-controlled secreted factors. GRP78 targeting in mice resulting in a cytokine shift and increased tumoral CD80+/CD68+ cells, suggesting that GRP78 inhibition favors a M1-like macrophage profile. Inhibition of UPR components in both macrophage and breast cancer cells, similar to what would be observed in systemic cancer therapies, indicated that either PERK or GRP78 inhibition enhances macrophage cytolytic clearance of breast cancer cells. Taken together, these data suggest that targeting GRP78 or PERK promotes an anti-tumor immune response by either directly promoting macrophage cytolytic activity (PERK targeting) or indirectly by shifting tumoral cytokine secretion (GRP78 targeting).

Citation Format: Cook KL, Wilson A, Westwood B, Soto-Pantoja DR. Targeting of the unfolded protein response signaling arms differentially regulates macrophage proliferation, plasticity, and breast cancer cell clearance [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-06.

Lifetime Genistein Intake Increases the Response of Mammary Tumors to Tamoxifen in Rats

PURPOSE

Whether it is safe for estrogen receptor-positive (ER+) patients with breast cancer to consume soy isoflavone genistein remains controversial. We compared the effects of genistein intake mimicking either Asian (lifetime) or Caucasian (adulthood) intake patterns to that of starting its intake during tamoxifen therapy using a preclinical model.

EXPERIMENTAL DESIGN

Female Sprague-Dawley rats were fed an AIN93G diet supplemented with 0 (control diet) or 500 ppm genistein from postnatal day 15 onward (lifetime genistein). Mammary tumors were induced with 7,12-dimethylbenz(a)anthracene (DMBA), after which a group of control diet-fed rats were switched to genistein diet (adult genistein). When the first tumor in a rat reached 1.4 cm in diameter, tamoxifen was added to the diet and a subset of previously only control diet-fed rats also started genistein intake (post-diagnosis genistein).

RESULTS

Lifetime genistein intake reduced de novo resistance to tamoxifen, compared with post-diagnosis genistein groups. Risk of recurrence was lower both in the lifetime and in the adult genistein groups than in the post-diagnosis genistein group. We observed downregulation of unfolded protein response (UPR) and autophagy-related genes (GRP78, IRE1α, ATF4, and Beclin-1) and genes linked to immunosuppression (TGFβ and Foxp3) and upregulation of cytotoxic T-cell marker CD8a in the tumors of the lifetime genistein group, compared with controls, post-diagnosis, and/or adult genistein groups.

CONCLUSIONS

Genistein intake mimicking Asian consumption patterns improved response of mammary tumors to tamoxifen therapy, and this effect was linked to reduced activity of UPR and prosurvival autophagy signaling and increased antitumor immunity. Clin Cancer Res; 23(3); 814-24. ©2017 AACR.

Social isolation induces autophagy in the mouse mammary gland: link to increased mammary cancer risk

Social isolation is a strong predictor of early all-cause mortality and consistently increases breast cancer risk in both women and animal models. Because social isolation increases body weight, we compared its effects to those caused by a consumption of obesity-inducing diet (OID) in C57BL/6 mice. Social isolation and OID impaired insulin and glucose sensitivity. In socially isolated, OID-fed mice (I-OID), insulin resistance was linked to reduced Pparg expression and increased neuropeptide Y levels, but in group-housed OID fed mice (G-OID), it was linked to increased leptin and reduced adiponectin levels, indicating that the pathways leading to insulin resistance are different. Carcinogen-induced mammary tumorigenesis was significantly higher in I-OID mice than in the other groups, but cancer risk was also increased in socially isolated, control diet-fed mice (I-C) and G-OID mice compared with that in controls. Unfolded protein response (UPR) signaling (GRP78; IRE1) was upregulated in the mammary glands of OID-fed mice, but not in control diet-fed, socially isolated I-C mice. In contrast, expression of BECLIN1, ATG7 and LC3II were increased, and p62 was downregulated by social isolation, indicating increased autophagy. In the mammary glands of socially isolated mice, but not in G-OID mice, mRNA expressions of p53 and the p53-regulated autophagy inducer Dram1 were upregulated, and nuclear p53 staining was strong. Our findings further indicated that autophagy and tumorigenesis were not increased in Atg7(+/-) mice kept in social isolation and fed OID. Thus, social isolation may increase breast cancer risk by inducing autophagy, independent of changes in body weight.

Effects of In Utero Exposure to Ethinyl Estradiol on Tamoxifen Resistance and Breast Cancer Recurrence in a Preclinical Model

Background

Responses to endocrine therapies vary among patients with estrogen receptor (ER+) breast cancer. We studied whether in utero exposure to endocrine-disrupting compounds might explain these variations.

Methods

We describe a novel ER+ breast cancer model to study de novo and acquired tamoxifen (TAM) resistance. Pregnant Sprague Dawley rats were exposed to 0 or 0.1 ppm ethinyl estradiol (EE2), and the response of 9,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors to 15 mg/kg TAM, with (n = 17 tumors in the controls and n = 20 tumors in EE2 offspring) or without 1.2 g/kg valproic acid and 5 mg/kg hydralazine (n = 24 tumors in the controls and n = 32 tumors in EE2 offspring) in the female offspring, was assessed. One-sided Chi2 tests were used to calculate P values. Comparisons of differentially expressed genes between mammary tumors in in utero EE2-exposed and control rats, and between anti-estrogen-resistant LCC9 and -sensitive LCC1 human breast cancer cells, were also performed.

Results

In our preclinical model, 54.2% of mammary tumors in the control rats exhibited a complete response to TAM, of which 23.1% acquired resistance with continued anti-estrogen treatment and recurred. Mammary tumors in the EE2 offspring were statistically significantly less likely to respond to TAM (P = .047) and recur (P = .007). In the EE2 offspring, but not in controls, adding valproic acid and hydralazine to TAM prevented recurrence (P < .001). Three downregulated and hypermethylated genes (KLF4, LGALS3, MICB) and one upregulated gene (ETV4) were identified in EE2 tumors and LCC9 breast cancer cells, and valproic acid and hydralazine normalized the altered expression of all four genes.

Conclusions

Resistance to TAM may be preprogrammed by in utero exposure to high estrogen levels and mediated through reversible epigenetic alterations in genes associated with epithelial-mesenchymal transition and tumor immune responses.

Abstract 904: Heterozygous ATG7 inhibition enhances endocrine therapy responsiveness through regulation of damage associated molecular patterns and priming the immune system in ER+ breast tumors

Breast cancer is the most prevalent cancer in women, with over 230,000 new cases diagnosed annually. The most common type of breast cancer, comprising over 70% of all cases, express the estrogen receptor (ER); these tumors are usually treated with an endocrine therapy such as an antiestrogen or aromatase inhibitor. Unfortunately, many of these tumors develop resistance, or in some instances express de novo resistance, which limits the curative potential of these therapies. Autophagy, a cellular process of “self-eating”, is implicated as possible contributor to endocrine therapy resistance in breast cancer. We previously showed that inhibiting autophagy through low-dose chloroquine treatment reversed antiestrogen therapy resistance in ER+ orthotopic breast tumors. We now show that heterozygous deletion of ATG7 decreased breast tumor multiplicity and increased endocrine targeting therapy sensitivity in a DMBA-model of ER+ mammary carcinogenesis. Knockdown of ATG7 through RNAi increased cytoplasmic to nuclear high-mobility group binding protein B1 (HMGB1) protein ratio, suggesting targeting ATG7 promotes damage associated molecular patterns (DAMP) signaling. Heterozygous deletion of ATG7 also increased cytoplasmic HMGB1 protein expression in tumor epithelial cells indicating targeting ATG7 promotes DAMP signaling in vivo. Furthermore, tumors from ATG7 heterozygous mice displayed increased CD68 staining indicating elevated macrophage infiltration. Corroborating previous literature showing the critical role of autophagy in T-cell maturation, splenic CD8+ T-cells were significantly reduced in tumor bearing ATG7 heterozygous mice. However, ATG7 heterozygous mice displayed increased tumor CD8+ T-cell population. These data suggest that while targeting ATG7 reduces overall circulating T-cell populations, inhibiting ATG7 enhances tumoral cytotoxic T-cell recruitment. Tumors from ATG7 heterozygous mice also showed a significant decrease in foxp3+ cells, indicating targeting ATG7 reduces immuno-suppressive T-reg population. Serum from ATG7 heterozygous mice showed increased circulating MDC, MCP-1, IL-6, and eotaxin cytokines. Taken together, these data suggests that ATG7 inhibition promotes an anti-tumor pro-inflammatory cytokine profile to enhance tumoral immune cell recruitment and promote endocrine therapy responsiveness.

Citation Format: Robert Clarke, Pamela A.G. Clarke, Anni Wärri, Katherine L. Cook. Heterozygous ATG7 inhibition enhances endocrine therapy responsiveness through regulation of damage associated molecular patterns and priming the immune system in ER+ breast tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 904.

Abstract 1027: Autophagy as a mediator of increased mammary cancer risk in socially isolated mice

Social isolation in mice is a model of post-traumatic stress disorder (PTSD) which affects 12-20% of newly diagnosed breast cancer patients. Since social isolation increases the risk of breast and other cancers and increases overall and cancer-specific mortality, it is critical to determine the biological pathways that mediate the effects of social isolation on cancer to identify targets to prevent its adverse effects. Among the potential mechanisms is autophagy, which we have found previously to be induced in the mammary glands of socially isolated mice. Others have reported upregulation of p53 and Hk2 in socially isolated animals. Both are genes that induce autophagy. In our study, social isolation increased nuclear p53 levels, expression of the p53-regulated autophagy genes Dram1 and Mdm2 in the mammary glands of mice. Further, social isolation led to an increase in body weight, particularly when mice were fed a high fat diet, but the ability of social isolation to induce autophagy was independent of high fat diet. Here we investigated the effect of social isolation on mammary tumorigenesis in heterozygous Atg7 knockout mice. Social isolation was implemented by housing mice singly and feeding them a high fat diet from weaning onwards. Socially isolated wildtype C57BL6 mice exhibited upregulation of Atg7 and LC3II and downregulation of p62, indicative of increased autophagy that allows cancer cells to survive. Atg7+/- mice, in contrast, exhibited significantly lower LC3II and higher p62 levels compared with group-housed wildtype mice. We also found that socially isolated wildtype mice were at a significantly increased risk of developing estrogen receptor positive (ER+) mammary cancer induced by treating mice with 15 mg medroxyprogesterone acetate (MPA) and three doses of 1 mg 7,12-dimethylbetz(a)anthracene (DMBA) (given on weeks 7, 8 and 9). No increase in mammary tumorigenesis was seen in socially isolated Atg7+/- mice, compared with group-housed Atg7+/- mice. Our results confirm that social isolation induces autophagy and show that increased autophagy in socially isolated mice was causally linked to increased breast cancer risk. Since activation of survival autophagy is known to impair response to cancer treatments, including to chemotherapy and endocrine therapy, it is imperative to determine if cancer patients suffering from PTSD exhibit increased autophagy. Autophagy inhibitors, such as chloroquine, are currently being investigated in the clinic as a 2nd line therapy for metastatic cancer, and therefore available also to be used in cancer patients experiencing PTSD-like symptoms.

Citation Format: Leena A. Hilakivi-Clarke, Fabia O. Andrade, Allison Sumis, Kerrie B. Bouker, Rong Hu, Robert Clarke, Katherine L. Cook. Autophagy as a mediator of increased mammary cancer risk in socially isolated mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1027.