Mammary Tumor Growth Research Articles

Immunogenic shift of arginine metabolism triggers systemic metabolic and immunological reprogramming to prevent HER2+ breast cancer.

Arginine metabolism in tumors is often shunted into the pathway producing pro-tumor and immune suppressive polyamines (PAs), while downmodulating the alternative nitric oxide (NO) synthesis pathway. Aiming to correct arginine metabolism in tumors, arginine deprivation therapy and inhibitors of PA synthesis have been developed. Despite some therapeutic advantages, these approaches have often yielded severe side effects, making it necessary to explore an alternative strategy. We previously reported that supplementing SEP, the endogenous precursor of BH 4 (the essential NO synthase cofactor), could correct arginine metabolism in tumor cells and tumor-associated macrophages (TAMs) and induce their metabolic and phenotypic reprogramming. We saw that oral SEP treatment effectively suppressed the growth of HER2-positive mammary tumors in animals. SEP also has no reported dose-dependent toxicity in clinical trials for metabolic disorders. In the present study, we report that a long-term use of SEP in animals susceptible to HER2-positive mammary tumors effectively prevented tumor occurrence. These SEP-treated animals had undergone reprogramming of the systemic metabolism and immunity, elevating total T cell counts in the circulation and bone marrow. Given that bone marrow-resident T cells are mostly memory T cells, it is plausible that chronic SEP treatment promoted memory T cell formation, leading to a potent tumor prevention. These findings suggest the possible roles of the SEP/BH 4 /NO axis in promoting memory T cell formation and its potential therapeutic utility for preventing HER2-positive breast cancer.

Inhibition of NAMPT by PAK4 Inhibitors.

The serine/threonine kinase PAK4 plays a crucial role in regulating cell proliferation, survival, migration, and invasion. Overexpression of PAK4 correlates with poor prognosis in some cancers. KPT-9274, a PAK4 inhibitor, significantly reduces the growth of triple-negative breast cancer cells and mammary tumors in mouse models, and it also inhibits the growth of several other types of cancer cells. Interestingly, although it was first identified as a PAK4 inhibitor, KPT-9274 was also found to inhibit the enzyme NAMPT (nicotinamide phosphoribosyltransferase), which is crucial for NAD (nicotinamide adenine dinucleotide) synthesis and vital for cellular energy and growth. These results made us question whether growth inhibition in response to KPT-9274 was due to PAK4 inhibition, NAMPT inhibition, or both. To address this, we tested several other PAK4 inhibitors that also inhibit cell growth, to determine whether they also inhibit NAMPT activity. Our findings confirm that multiple PAK4 inhibitors also inhibit NAMPT activity. This was assessed both in cell-free assays and in a breast cancer cell line. Molecular docking studies were also used to help us better understand the mechanism by which PAK4 inhibitors block PAK4 and NAMPT activity, and we identified specific residues on the PAK4 inhibitors that interact with NAMPT and PAK4. Our results suggest that PAK4 inhibitors may have a more complex mechanism of action than previously understood, necessitating further exploration of how they influence cancer cell growth.

Novel Inhibition of Central Carbon Metabolism Pathways by Rac and CDC42 inhibitor MBQ167 and Paclitaxel.

Triple negative breast cancer (TNBC) represents a therapeutic challenge in which standard chemotherapy is limited to paclitaxel. MBQ167, a clinical stage small molecule inhibitor that targets Rac and Cdc42, inhibits tumor growth and metastasis in mouse models of TNBC. Herein, we investigated the efficacy of MBQ167 in combination with paclitaxel in TNBC preclinical models, as a prelude to safety trials of this combination in patients with advanced breast cancer. Individual MBQ167 or combination therapy with paclitaxel was more effective at reducing TNBC cell viability and increasing apoptosis compared with paclitaxel alone. In orthotopic mouse models of human TNBC (MDA-MB231 and MDA-MB468), individual MBQ167, paclitaxel, or the combination reduced mammary tumor growth with similar efficacy, with no apparent liver toxicity. However, paclitaxel single agent treatment significantly increased lung metastasis, whereas MBQ167, single or combined, reduced lung metastasis. In the syngeneic 4T1/BALB/c model, combined MBQ167 and paclitaxel decreased established lung metastases by ∼80%. To determine the molecular basis for the improved efficacy of the combined treatment on metastasis, 4T1 tumor extracts from BALB/c mice treated with MBQ167, paclitaxel, or the combination were subjected to transcriptomic analysis. Gene set enrichment identified specific downregulation of central carbon metabolic pathways by the combination of MBQ167 and paclitaxel but not individual compounds. Biochemical validation, by immunoblotting and metabolic Seahorse analysis, shows that combined MBQ167 and paclitaxel reduces glycolysis. This study provides a strong rationale for the clinical testing of MBQ167 in combination with paclitaxel as a potential therapeutic for TNBC and identifies a unique mechanism of action.

Development of a humanized anti-FABP4 monoclonal antibody for potential treatment of breast cancer

BackgroundBreast cancer is the most common cancer in women diagnosed in the U.S. and worldwide. Obesity increases breast cancer risk without clear underlying molecular mechanisms. Our studies demonstrate that circulating adipose fatty acid binding protein (A-FABP, or FABP4) links obesity-induced dysregulated lipid metabolism and breast cancer risk, thus potentially offering a new target for breast cancer treatment.MethodsWe immunized FABP4 knockout mice with recombinant human FABP4 and screened hybridoma clones with specific binding to FABP4. The potential effects of antibodies on breast cancer cells in vitro were evaluated using migration, invasion, and limiting dilution assays. Tumor progression in vivo was evaluated in various types of tumorigenesis models including C57BL/6 mice, Balb/c mice, and SCID mice. The phenotype and function of immune cells in tumor microenvironment were characterized with multi-color flow cytometry. Tumor stemness was detected by ALDH assays. To characterize antigen-antibody binding capacity, we determined the dissociation constant of selected anti-FABP4 antibodies via surface plasmon resonance. Further analyses in tumor tissue were performed using 10X Genomics Visium spatial single cell technology.ResultsHerein, we report the generation of humanized monoclonal antibodies blocking FABP4 activity for breast cancer treatment in mouse models. One clone, named 12G2, which significantly reduced circulating levels of FABP4 and inhibited mammary tumor growth, was selected for further characterization. After confirming the therapeutic efficacy of the chimeric 12G2 monoclonal antibody consisting of mouse variable regions and human IgG1 constant regions, 16 humanized 12G2 monoclonal antibody variants were generated by grafting its complementary determining regions to selected human germline sequences. Humanized V9 monoclonal antibody showed consistent results in inhibiting mammary tumor growth and metastasis by affecting tumor cell mitochondrial metabolism.ConclusionsOur current evidence suggests that targeting FABP4 with humanized monoclonal antibodies may represent a novel strategy for the treatment of breast cancer and possibly other obesity- associated diseases.

CCN6 Suppresses Metaplastic Breast Carcinoma by Antagonizing Wnt/β-Catenin Signaling to Inhibit EZH2-Driven EMT.

Metaplastic breast carcinomas (mBrCA) are a highly aggressive subtype of triple-negative breast cancer with histologic evidence of epithelial-to-mesenchymal transition and aberrant differentiation. Inactivation of the tumor suppressor gene cellular communication network factor 6 (CCN6; also known as Wnt1-induced secreted protein 3) is a feature of mBrCAs, and mice with conditional inactivation of Ccn6 in mammary epithelium (Ccn6-KO) develop spindle mBrCAs with epithelial-to-mesenchymal transition. Elucidation of the precise mechanistic details of how CCN6 acts as a tumor suppressor in mBrCA could help identify improved treatment strategies. In this study, we showed that CCN6 interacts with the Wnt receptor FZD8 and coreceptor LRP6 on mBrCA cells to antagonize Wnt-induced activation of β-catenin/TCF-mediated transcription. The histone methyltransferase EZH2 was identified as a β-catenin/TCF transcriptional target in Ccn6-KO mBrCA cells. Inhibiting Wnt/β-catenin/TCF signaling in Ccn6-KO mBrCA cells led to reduced EZH2 expression, decreased histone H3 lysine 27 trimethylation, and deregulation of specific target genes. Pharmacologic inhibition of EZH2 reduced growth and metastasis of Ccn6-KO mBrCA mammary tumors in vivo. Low CCN6 is significantly associated with activated β-catenin and high EZH2 in human spindle mBrCAs compared with other subtypes. Collectively, these findings establish CCN6 as a key negative regulator of a β-catenin/TCF/EZH2 axis and highlight the inhibition of β-catenin or EZH2 as a potential therapeutic approach for patients with spindle mBrCAs. Significance: CCN6 deficiency drives metaplastic breast carcinoma growth and metastasis by increasing Wnt/β-catenin activation to upregulate EZH2, identifying EZH2 inhibition as a mechanistically guided treatment strategy for this deadly form of breast cancer.

Cold-inducible RNA-binding protein as a context-specific functional mediator of breast cancer metastasis.

3136 Background: Cold-inducible RNA-binding protein (CIRBP) is a stress-induced mRNA-binding protein associated with clinical outcomes in a variety of human disease states. CIRBP’s role as a prognostic biomarker in breast cancer (BC) has yet to be established. Methods: We describe a clinically annotated tissue micro-array cohort of 1406 hormone receptor positive (HR+) and 281 triple negative primary breast cancers (TNBC) stained by immunohistochemistry (IHC) for CIRBP. Statistical analyses were performed with the Kaplan-Meier estimator, as well as univariate and multivariate Cox proportional-hazards models. Multivariate models incorporated tumor size, lymph node status, grade and CIRBP expression levels. Co-primary endpoints were overall survival (OS) and progression-free survival (PFS). MDA-MB-231 TNBC cells and MDA-MB-361 HR+ cells were used for CIRBP knockout (KO) by CRISPR/Cas9, and subsequent mammary fat pad injections were performed in immunocompromised mice. Results: In N=281 primary TNBCs, high levels of CIRBP expression by IHC was associated with poor prognosis in multivariate analysis (OS: adjusted hazard ratio (aHR) 2.05, 95% confidence interval (CI) 1.24-3.41, P=0.005. PFS: aHR 2.46, 95% CI 1.33-4.57, P=0.004). However, in N=1406 HR+ primary BC, CIRBP expression was correlated with favorable prognosis (OS: aHR 0.927, 95% CI 0.88-0.98, P=0.05. PFS: aHR 0.904, 95% CI 0.85-0.96, P=0.002). CIRBP KO had minimal impact on mammary fat pad primary tumor growth in both MDA-MB-231 and MDA-MB-361 cell models. However, CIRBP KO resulted in the inhibition of efficient spontaneous metastasis to the liver and lungs in TNBC MDA-MB-231 cells but not HR+ MDA-MB-361 cells. Conclusions: CIRBP expression is associated with poor prognosis in TNBC but not HR+ BC patients, a finding validated with CRISPR/Cas9 KO in representative model systems. This finding highlights the prognostic significance of CIRBP in TNBC and suggests differential underlying mRNA targets bound and modulated by CIRBP in TNBC and HR+ BC, respectively.

Mutation of SIVA, a candidate metastasis gene identified from clonally related bilateral breast cancers, promotes breast cancer cell spread in vitro and in vivo.

Metastasis is the most dreaded outcome after a breast cancer diagnosis, and little is known regarding what triggers or promotes breast cancer to spread distally, or how to prevent or eradicate metastasis effectively. Bilateral breast cancers are an uncommon form of breast cancers. In our study, a percentage of bilateral breast cancers were clonally related based on copy number variation profiling. Whole exome sequencing and comparative sequence analysis revealed that a limited number of somatic mutations were acquired in this "breast-to-breast" metastasis that might promote breast cancer distant spread. One somatic mutation acquired was SIVA-D160N that displayed pro-metastatic phenotypes in vivo and in vitro. Over-expression of SIVA-D160N promoted migration and invasion of human MB-MDA-231 breast cancer cells in vitro, consistent with a dominant negative interfering function. When introduced via tail vein injection, 231 cells over-expressing SIVA-D160N displayed enhanced distant spread on IVIS imaging. Over-expression of SIVA-D160N promoted invasion and anchorage independent growth of mouse 4T1 breast cancer cells in vitro. When introduced orthotopically via mammary fat pad injection in syngeneic Balb/c mice, over-expression of SIVA-D160N in 4T1 cells increased orthotopically implanted mammary gland tumor growth as well as liver metastasis. Clonally related bilateral breast cancers represented a novel system to investigate metastasis and revealed a role of SIVA-D160N in breast cancer metastasis. Further characterization and understanding of SIVA function, and that of its interacting proteins, may elucidate mechanisms of breast cancer metastasis, providing clinically useful biomarkers and therapeutic targets.

LYVE-1-expressing Macrophages Modulate the Hyaluronan-containing Extracellular Matrix in the Mammary Stroma and Contribute to Mammary Tumor Growth.

We have identified a macrophage subset in mouse mammary tumors associated with tumor structural components. When this macrophage subset is absent in tumors, we report a delay in tumor growth and an increase in antitumor immune cells. Understanding the functions of distinct macrophage subsets may allow for improved therapeutic strategies for patients with breast cancer.

Abstract ED03-01: Breaking the Obesity-Breast Cancer Link: Comparing Diet, Drug and Surgical Approaches

Abstract The prevalence of obesity, an established risk and progression factor for at least 15 types of cancer (including breast cancer), continues to rise in the US and many other countries. Lifestyle approaches to weight loss have proven challenging for most people to maintain, and bariatric surgery, while effective, is expensive and has numerous adverse effects. The recent availability of highly effective incretin therapies for weight loss raises several key questions that we will address, including: i) do these agents drive weight loss in obese female mice?; ii) do they reverse obesity-induced metabolic dysregulation?; iii) can they reverse obesity-driven cancer?; iv) how heterogeneous is the response to these agents? We will report our study of the effects of extended (13 weeks) tirzepatide (TZP, a dual GLP1R/GIPR agonist) treatment in obese female mice on weight loss, metabolic hormones, and mammary tumor growth. We found that—similar to reports in the literature using male mice—obese female mice lost >20% body weight by 4 weeks of TZP treatment. Moreover, TZP-induced weight loss was maintained through 13 weeks of treatment by progressively escalating the dose up to 40 nmol/kg. Congruent with reports in male rodents and humans, we found the majority of weight loss in female mice was attributed to loss of adipose tissue, rather than lean mass. The effects of TZP on body weight and composition were associated with reversal of obesity-induced changes in glycemic control and circulating levels of metabolic hormones, particularly leptin, insulin, and IGF-1. TZP also significantly reversed the protumor effects of obesity in our murine E0771 orthotopic transplant model of TNBC.Furthermore, daily 30% calorie restriction, which we previously reported has strong weight loss-inducing, metabolic reprogramming and anticancer effects in multiple mouse models of breast and other cancers, reversed body weight, adiposity, and TNBC tumor growth and altered metabolic hormones to a greater extent than all groups studied, including the never-obese control mice and TZP-treated mice. Citation Format: S. Hursting. Breaking the Obesity-Breast Cancer Link: Comparing Diet, Drug and Surgical Approaches [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr ED03-01.

Abstract PO4-25-05: LYVE-1 expressing macrophages modulate the extracellular matrix and contribute to mammary tumor growth

Abstract Macrophages represent a heterogeneous myeloid population with varied functions in normal tissue and tumors. We identify a tissue resident macrophage subpopulation marked by the protein LYVE-1 in both the female mammary gland and mammary tumor. In a genetic LYVE-1+ macrophage deletion model, loss of LYVE-1+ macrophage leads to accumulation of the extracellular matrix glycosaminoglycan hyaluronan. Further, qRT-PCR of tissue lacking LYVE-1+ macrophages yields a gene signature associated with extracellular matrix disorganization. Supporting a tissue remodeling functionality, inducing a LYVE-1 macrophages phenotype in vitro prompts HA internalization and increases hyaluronidase expression. In a murine tumor model, deletion of LYVE-1+ macrophages slows tumor progression and increases HA accumulation, suggesting an anti-tumorigenic, tissue remodeling phenotype. LYVE-1+ macrophages preferentially localize to HA dense regions of tumors, specifically in the tumor stroma, while scRNA-seq of murine tumors demonstrates a LYVE-1+ macrophage phenotype associated with tissue remodeling and immunosuppression. Our data illustrate a LYVE-1+ macrophage population critical for HA homeostasis and tumor progression. Citation Format: Alexis Elfstrum, Annisa Rumahorbo, Braedan McCluskey, Emma Nelson, Kaylee Schwertfeger. LYVE-1 expressing macrophages modulate the extracellular matrix and contribute to mammary tumor growth [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-25-05.

Tumor Oxygenation in an Orthotopic Model of Breast Cancer: Impact of Dietary Nitrate Supplementation

Introduction: Breast cancer (BC), the predominant non-melanoma cancer among women, is projected to escalate to more than 3 million new cases and ~1 million fatalities globally by 2040. Chronic and fluctuating low oxygen (O2) conditions within tumors favor malignant growth, decreased responsiveness to therapeutic interventions, and reduced patient survivability. Treatment strategies to combat tumor hypoxia are desperately needed. Dietary nitrate supplementation via beetroot juice (BRJ), which increases nitric oxide (NO) production through the nitrate-nitrite-NO pathway, has been demonstrated to increase skeletal muscle blood flow, improve mitochondrial effciency, and reduce metabolic demands. Specifically, BRJ improves interstitial oxygen pressures (PO2 is) in acidic, low oxygen environments such as that found in the tumor microenvironment. Therefore, we hypothesized that BRJ supplementation would increase PO2 is in BC tumors. Methods: Female Fischer 344 retired breeder rats (6-8 months old) were used in this investigation. Adenocarcinoma cells (MAT B III at 6 x 103) were injected into the mammary duct and tumor growth was monitored over 2 weeks. Once tumors reached ~5 mm in diameter, rats were randomly assigned to consume BRJ (1 mmol/kg/day; BRJ, n=3) or water (CON; n=3) for 5 days. Under pentobarbital anesthesia, tumor PO2 is measurements were obtained using phosphorescence quenching. Results: Tumor growth rate was decreased in BRJ compared to CON rats (0.5 ± 0.1 vs. 1.0 ± 0.1 mm/day; p<0.05). Heart rate and mean arterial pressure were not different between groups (P>0.05). Blood lactate was significantly decreased in BRJ compared to CON rats (0.5 ± 0.1 vs. 1.2 ± 0.1 mmol/L, p<0.05). There was an increase in mean tumor PO2 is in BRJ vs. control rats (6.9 ± 1.3 vs. 3.7 ± 0.47; p<0.05). Conclusions: This study offers promising preliminary insights into the potential of dietary nitrate supplementation as an adjunctive approach to BC treatment to increase tumor PO2 is and reduce tumor growth rate. Future and ongoing studies will increase the sample size, use fluorescent microspheres to measure tumor blood flow, and explore the potential for BRJ and other NO agonists to combat tumor hypoxia and the skeletal muscle dysfunction associated with cancer progression. This research was funded by the following sources: the Johnson Cancer Research Center Innovative Research Award and Sustained Momentum for Investigators with Laboratories Established (SMILE) Grants at Kansas State University, the National Institute on Aging (Grant 1R15AG078060), and Ruth L. Kirschstein National Research Service Awards from the National Heart, Lung, and Blood Institute (Grants 1F31HL167618-01 and 1F31HL170643-01). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 2007: Ischemic And Non-ischemic Cardiovascular Events Differentially Regulate Cross Disease Communication With Cancer

Cancer and cardiovascular disease (CVD) are the top two leading causes of death worldwide, exhibiting cross-disease communication that increases morbidity. Cancer patients are at significantly increased risk for CVD and recent studies by our lab and others indicate that CVDs like myocardial infarction (MI) or heart failure can in turn accelerate tumor growth. We previously showed this occurs through changes in the innate immune system or via tumor-promoting factors secreted from the damaged myocardium, which together have established the nascent field of Reverse CardioOncology. We hypothesized that ischemic and non-ischemic CVD injuries have distinctly different mechanisms underlying mammary tumor growth. To mimic these events, we modeled non-cardiac hind limb ischemic injury by femoral artery ligation (FAL) and non-ischemic cardiac injury by cardiac cryoinjury (CCI). To test our hypothesis, we introduced primary E0771 mouse mammary cancer cells into the mammary fat pad three days prior to FAL or CCI. Measurements of tumor over time showed significant increases in tumor growth after both FAL and CCI when compared to sham surgeries. However, only the ischemic injury, FAL, induced similar changes in immune cells to what we observed after MI (induced by left anterior descending coronary artery [LAD] ligation). This included significant increases in myeloid populations and decreased lymphocytes within the circulation. Additionally, flow cytometry of immune cells within tumors of mice exposed to FAL showed significantly increased myeloid cells and macrophages, as well as increased immunosuppressive T-regulatory cells. In contrast, while CCI showed significantly increased tumor burden and circulating leukocytes, there were no differences in the above-mentioned subsets of immune cells within the circulation or within the tumor. These data suggest that ischemic injury, via FAL or LAD, induces an immunosuppressive environment within the tumor that accelerates cancer growth that is distinct from the non-ischemic cardiac injury induced by CCI. Taken together, our data suggest that the immune reprogramming after ischemic CVDs is a risk factor for tumor growth and these data help to elucidate the mechanisms that underlie cancer risk in CVD patients.

Voluntary wheel running reduces tumor growth and increases capillarity in the heart during doxorubicin chemotherapy in a murine model of breast cancer.

Introduction: The possible beneficial effects of physical activity during doxorubicin treatment of breast cancer need further investigation as many of the existing studies have been done on non-tumor-bearing models. Therefore, in this study, we aim to assess whether short-term voluntary wheel-running exercise during doxorubicin treatment of breast cancer-bearing mice could induce beneficial cardiac effects and enhance chemotherapy efficacy. Methods: Murine breast cancer I3TC cells were inoculated subcutaneously to the flank of female FVB mice (n = 16) that were divided into exercised and non-exercised groups. Two weeks later, doxorubicin treatment was started via intraperitoneal administration (5mg/kg weekly for 3weeks). Organs were harvested a day after the last dose. Results: The tumor volume over time was significantly different between the groups, with the exercising group having lower tumor volumes. The exercised group had increased body weight gain, tumor apoptosis, capillaries per cardiomyocytes, and cardiac lactate dehydrogenase activity compared to the unexercised group, but tumor blood vessel density and maturation and tumor and cardiac HIF1-α and VEGF-A levels did not differ from those of the non-exercised group. Discussion: We conclude that even short-term light exercise such as voluntary wheel running exercise can decrease the subcutaneous mammary tumor growth, possibly via increased tumor apoptosis. The increase in cardiac capillaries per cardiomyocytes may also have positive effects on cancer treatment outcomes.

Benzo[a]pyrene promotes an epithelial‐to‐mesenchymal transition process in MCF10A cells and mammary tumor growth and brain metastasis in female mice

AbstractBreast cancer is the most frequent neoplasia in developed countries and the leading cause of death in women worldwide. Epithelial‐to‐mesenchymal transition (EMT) is a cellular process through which epithelial cells decrease or lose their epithelial characteristics and gain mesenchymal properties. EMT mediates tumor progression, because tumor cells acquire the capacity to execute the multiple steps of invasion and metastasis. Benzo[a]pyrene (B[a]P) is an environmental organic pollutant generated during the burning of fossil fuels, wood, and other organic materials. B[a]P exposition increases the incidence of breast cancer, and induces migration and/or invasion in MDA‐MB‐231 and MCF‐7 breast cancer cells. However, the role of B[a]P in the induction of an EMT process and metastasis of mammary carcinoma cells has not been studied in detail. In this study, we demonstrate that B[a]P induces an EMT process in MCF10A mammary non‐tumorigenic epithelial cells. In addition, B[a]P promotes the formation of larger tumors in Balb/cJ mice inoculated with 4T1 cells than in untreated mice and treated with dimethyl sulfoxide (DMSO). B[a]P also increases the number of mice with metastasis to brain and the total number of brain metastatic nodules in Balb/cJ mice inoculated with 4T1 cells compared with untreated mice and treated with DMSO. In conclusion, B[a]P induces an EMT process in MCF10A cells and the growth of mammary tumors and metastasis to brain in Balb/cJ mice inoculated with 4T1 cells.

Retraction Note: Declining melatonin levels and MT1 receptor expression in aging rats is associated with enhanced mammary tumor growth and decreased sensitivity to melatonin.

Retraction Note: Declining melatonin levels and MT1 receptor expression in aging rats is associated with enhanced mammary tumor growth and decreased sensitivity to melatonin.

Methyl-CpG binding domain protein 2 (Mbd2) drives breast cancer progression through the modulation of epithelial-to-mesenchymal transition

Methyl-CpG-binding domain protein 2 (Mbd2), a reader of DNA methylation, has been implicated in different types of malignancies, including breast cancer. However, the exact role of Mbd2 in various stages of breast cancer growth and progression in vivo has not been determined. To test whether Mbd2 plays a causal role in mammary tumor growth and metastasis, we performed genetic knockout (KO) of Mbd2 in MMTV-PyMT transgenic mice and compared mammary tumor progression kinetics between the wild-type (PyMT-Mbd2+/+) and KO (PyMT-Mbd2−/−) groups. Our results demonstrated that deletion of Mbd2 in PyMT mice impedes primary tumor growth and lung metastasis at the experimental endpoint (postnatal week 20). Transcriptomic and proteomic analyses of primary tumors revealed that Mbd2 deletion abrogates the expression of several key determinants involved in epithelial-to-mesenchymal transition, such as neural cadherin (N-cadherin) and osteopontin. Importantly, loss of the Mbd2 gene impairs the activation of the PI3K/AKT pathway, which is required for PyMT-mediated oncogenic transformation, growth, and survival of breast tumor cells. Taken together, the results of this study provide a rationale for further development of epigenetic therapies targeting Mbd2 to inhibit the progression of breast cancer.

Pirfenidone ameliorates alcohol-induced promotion of breast cancer in mice.

Alcohol consumption increases the risk of breast cancer and promotes cancer progression. Alcohol exposure could affect both processes of the mammary carcinogenesis, namely, the cell transformation and onset of tumorigenesis as well as cancer aggressiveness including metastasis and drug resistance/recurrence. However, the cellular and molecular mechanisms underlying alcohol tumor promotion remain unclear. There are four members of the mammalian p38 mitogen-activated protein kinase (MAPK) family, namely, p38α, p38β, p38γ and p38δ. We have previously demonstrated alcohol exposure selectively activated p38γ MAPK in breast cancer cells in vitro and in vivo. Pirfenidone (PFD), an antifibrotic compound approved for the treatment of idiopathic pulmonary fibrosis, is also a pharmacological inhibitor of p38γ MAPK. This study aimed to determine whether PFD is useful to inhibit alcohol-induced promotion of breast cancer. Female adolescent (5 weeks) MMTV-Wnt1 mice were exposed to alcohol with a liquid diet containing 6.7% ethanol. Some mice received intraperitoneal (IP) injection of PFD (100 mg/kg) every other day. After that, the effects of alcohol and PFD on mammary tumorigenesis and metastasis were examined. Alcohol promoted the progression of mammary tumors in adolescent MMTV-Wnt1 mice. Treatment of PFD blocked tumor growth and alcohol-promoted metastasis. It also significantly inhibited alcohol-induced tumorsphere formation and cancer stem cell (CSC) population. PFD inhibited mammary tumor growth and alcohol-promoted metastasis. Since PFD is an FDA-approved drug, the current findings may be helpful to re-purpose its application in treating aggressive breast cancer and alcohol-promoted mammary tumor progression.

Inhibitory effect of lomustine on the growth of spontaneous HER2-positive mammary tumors in transgenic mice

Inhibitory effect of lomustine on the growth of spontaneous HER2-positive mammary tumors in transgenic mice

Abstract 5568: Understanding the role of immune exclusion in mammary tumor growth

Abstract Multiple solid tumor types, including triple-negative breast cancer (TNBC), respond poorly to immunotherapy due to low infiltration of CD8+ T cells into the tumor core. The extracellular matrix (ECM) and its components such as collagen have been found to contribute to immune cell exclusion. Discoidin domain receptor 1 (DDR1) is a collagen receptor known to be aberrantly expressed in TNBC among multiple solid tumor types. We have uncovered a previously unappreciated function of DDR1 in immune exclusion through shaping a collagen fiber-based tumor defense against anti-tumor immunity (Sun et al, Nature 599, 673-678 (2021)). Our study showed that deletion of DDR1 in mouse mammary carcinoma cell lines such as E0771 and M-Wnt (syngeneic with C57BL/6 strain background) promotes infiltration of CD8+ T cells and reduces tumor growth in an immunocompetent mouse model. Extending the published study to other immunocompetent mouse strain backgrounds, we observed that deletion of DDR1 in EMT6 cells, another immune excluded TNBC mouse model in the BALB/c strain, increased the infiltration of CD8+ T cells to the tumor core and reduced tumor growth. Data concerning the DDR1-dependent spatial architecture of the mammary tumor microenvironment will be presented. Identifying specific immune and stromal cell populations and proteins spatially modified in the presence or absence of DDR1 may aid in development of new stand-alone or combination anti-cancer treatments with anti DDR1 antibody. Citation Format: Payal Mitra, Jorge Azpurua, Huai-Chin Chiang, Rong Li. Understanding the role of immune exclusion in mammary tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5568.

Abstract 159: LYVE-1-expressing macrophages modulate the hyaluronan-containing extracellular matrix in the mammary stroma and contribute to mammary tumor growth

Abstract Macrophages represent a heterogeneous myeloid population with diverse functions in normal tissues and tumors. While macrophages expressing the cell surface marker lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) have been identified in stromal regions of the normal mammary gland and in the peri-tumoral stroma, their functions within these regions are not well-understood. Using a genetic LYVE-1+ macrophage deletion mouse model, we demonstrate that loss of LYVE-1+ macrophages is associated with altered extracellular matrix remodeling in the normal mammary gland and reduced mammary tumor growth in vivo. In further studies focused on investigating the functions of LYVE-1+ macrophages in the tumor microenvironment, we demonstrate that LYVE-1 expression correlates with an increased ability of macrophages to bind, internalize, and degrade hyaluronan. Consistent with this, we show that deletion of LYVE-1+ macrophages correlates with increased hyaluronan accumulation in both the normal mammary gland and in mammary tumors. Analysis of single cell RNA sequencing of macrophages isolated from these tumors reveals that deletion of LYVE-1+ macrophages in tumors drives a shift in the majority of the remaining macrophages towards a pro-inflammatory phenotype, as well as an increase in CD8+ T cell infiltration. Together, these findings demonstrate that LYVE-1+ macrophages represent a tumor-promoting anti-inflammatory subset of macrophages that contributes to hyaluronan remodeling in the tumor microenvironment. Citation Format: Alexis K. Elfstrum, Annisa H. Rumahorbo, Braedan M. McCluskey, Kathryn L. Schwertfeger. LYVE-1-expressing macrophages modulate the hyaluronan-containing extracellular matrix in the mammary stroma and contribute to mammary tumor growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 159.