Mammary Tumor Cells Research Articles

Synergistic effect of the sphingosine kinase inhibitor safingol in combination with 2'-nitroflavone in breast cancer.

Sphingosine kinase-1 (SPHK1), the enzyme that catalyzes the synthesis of the pro-oncogenic molecule sphingosine-1-phosphate, is commonly upregulated in breast cancer cells and has been linked with poor prognosis and progression by promoting cell transformation, proliferation, angiogenesis, and metastasis. Therefore, SPHK1-targeting drugs have been proposed for breast cancer treatment, with better antitumor results when they are combined with chemotherapy. Previously, we demonstrated that the synthetic flavonoid 2'-nitroflavone (2'NF) exerted a potent and selective antiproliferative effect in murine HER2-positive LM3 mammary tumor cells. As we found that these cells overexpress SPHK1, we decided to explore the antitumor action of the combination of SPHK inhibitors (safingol or SKI-II) with 2'NF. In vitro assays showed that the combination induced a synergistic antiproliferative effect in LM3 cells. Similar results were obtained when human HER2-positive MDA-MB-453 breast cancer cells were treated with the combination of 2'NF/safingol. We also found that safingol potentiated the 2'NF apoptotic effect in both cell lines. The synergistic antitumor effect was confirmed in vivo in an LM3 syngeneic breast cancer model. Moreover, western blot analysis of tumor lysates revealed that combined treatment increased PARP cleavage and Bax protein levels and decreased anti-apoptotic Bcl-xL and Bcl-2 protein levels. Additionally, mice treated with both compounds showed no histopathological effects on different organ tissues. In summary, these findings suggest that the combination safingol/2'NF can be proposed as a potential therapeutic strategy for HER2-positive breast cancer treatment. KEY MESSAGES: The combination safingol/2'-nitroflavone exerts a synergic antitumor action in vitro. Safingol potentiates 2'-nitroflavone apoptotic effect in breast cancer cells. Safingol enhances the 2'-nitroflavone antitumor activity in vivo in breast cancer.

Proteomic analysis of extracellular vesicles derived from canine mammary tumour cell lines identifies protein signatures specific for disease state

BackgroundCanine mammary tumours (CMT) are among the most common types of tumours in female dogs. Diagnosis currently requires invasive tissue biopsies and histological analysis. Tumour cells shed extracellular vesicles (EVs) containing RNAs and proteins with potential for liquid biopsy diagnostics. We aimed to identify CMT subtype-specific proteome profiles by comparing the proteomes of EVs isolated from epithelial cell lines derived from morphologically normal canine mammary tissue, adenomas, and carcinomas.MethodsWhole-cell protein lysates (WCLs) and EV-lysates were obtained from five canine mammary cell lines: MTH53A (non-neoplastic); ZMTH3 (adenoma); MTH52C (simple carcinoma); 1305, DT1406TB (complex carcinoma); and their proteins identified by LC-MS/MS analyses. Gene Ontology analysis was performed on differentially abundant proteins from each group to identify up- and down-regulated biological processes. To establish CMT subtype-specific proteomic profiles, weighted gene correlation network analysis (WGCNA) was carried out.ResultsWCL and EVs displayed distinct protein abundance signatures while still showing the same increase in adhesion, migration, and motility-related proteins in carcinoma-derived cell lines, and of RNA processing and RNA splicing factors in the adenoma cell line. WGCNA identified CMT stage-specific co-abundant EV proteins, allowing the identification of adenoma and carcinoma EV signatures not seen in WCLs.ConclusionsEVs from CMT cell lines exhibit distinct protein profiles reflecting malignancy state, allowing us to identify potential biomarkers for canine mammary carcinomas, such as biglycan. Our dataset could therefore potentially serve as a basis for the development of a less invasive clinical diagnostic tool for the characterisation of CMT.

Autophagy is required for mammary tumor recurrence by promoting dormant tumor cell survival following therapy

BackgroundMortality from breast cancer is principally due to tumor recurrence. Recurrent breast cancers arise from the pool of residual tumor cells, termed minimal residual disease, that survive treatment and may exist in a dormant state for 20 years or more following treatment of the primary tumor. As recurrent breast cancer is typically incurable, understanding the mechanisms underlying dormant tumor cell survival is a critical priority in breast cancer research. The importance of this goal is further underscored by emerging evidence suggesting that targeting dormant residual tumor cells in early-stage breast cancer patients may be a means to prevent tumor recurrence and its associated mortality. In this regard, the role of autophagy in dormant tumor cell survival and recurrence remains unresolved, with conflicting reports of both pro-survival/recurrence-promoting and pro-death/recurrence-suppressing effects of autophagy inhibition in dormant tumor cells. Resolving this question has important clinical implications.MethodsWe used genetically engineered mouse models that faithfully recapitulate key features of human breast cancer progression, including minimal residual disease, tumor dormancy, and recurrence. We used genetic and pharmacological approaches to inhibit autophagy, including treatment with chloroquine, genetic knockdown of ATG5 or ATG7, or deletion of BECN and determined their effects on dormant tumor cell survival and recurrence.ResultsWe demonstrate that the survival and recurrence of dormant mammary tumor cells following therapy is dependent upon autophagy. We find that autophagy is induced in vivo following HER2 downregulation and remains activated in dormant residual tumor cells. Using genetic and pharmacological approaches we show that inhibiting autophagy by chloroquine administration, ATG5 or ATG7 knockdown, or deletion of a single allele of the tumor suppressor Beclin 1 is sufficient to inhibit mammary tumor recurrence, and that autophagy inhibition results in the death of dormant mammary tumor cells in vivo.ConclusionsOur findings demonstrate a pro-tumorigenic role for autophagy in tumor dormancy and recurrence following therapy, reveal that dormant tumor cells are uniquely reliant upon autophagy for their survival, and indicate that targeting dormant residual tumor cells by inhibiting autophagy impairs tumor recurrence. These studies identify a pharmacological target for a cellular state that is resistant to commonly used anti-neoplastic agents and suggest autophagy inhibition as an approach to reduce dormant minimal residual disease in order to prevent lethal tumor recurrence.

Transcriptome profiling of Canine Parvovirus 2 Nonstructural gene 1(CPV2.NS1) transfected 4T1 mice mammary tumor cells to elucidate its oncolytic effects

Oncolytic viral gene therapy is a directed approach to target cancer cells without affecting healthy cells of the body. Canine parvovirus (CPV2) is an oncolytic virus that precisely targets and destroys neoplastic cells by causing DNA damage, mitochondrial damage, and apoptosis. Non-structural gene 1 (NS1) of CPV, concerned with viral DNA replication is a key mediator of cytotoxicity of CPV and can specifically cause tumor cell lysis. In the present study, by using the transcriptomics approach, we tried to identify molecular pathways and key genes involved in CPV2.NS1 mediated 4T1 mice mammary tumor cell death. We identified necroptosis and mitochondrial damage-mediated apoptosis as major cell death pathways leading to CPV2.NS1 transfected 4T1 cancer cell death. Various DEGs identified in our study play an important role in pathways like the PI3K/AKT pathway, diverse metabolic pathways, MAPK signaling pathway, and FGF signaling pathway, whichare mostly dysregulated in cancerous conditions. Histone variant H2A.X genes, Capn2, and Mapk10/JNK are predicted as key genes that play a role in causing endoplasmic reticulum stress and mitochondrial damage, thereby leading to necroptosis and apoptosis. This study is a preliminary work done to identify key genes and molecular pathways involved in CPV2.NS1 mediated 4T1 cancer cells death which need to be further validated to establish this viral gene as a potent oncolytic agent.

Canine Mammary Tumours (CMTs) exploit mitochondrial cholesterol for aggressive reprogramming.

In human breast cancer the mitochondrial translocator protein (TSPO) aids pro-survival cellular response by facilitating the formation of mitochondrial contact sites with the nucleus termed Nucleus Associated Mitochondria (NAM). Here, we show that TSPO positively associates with the aggressiveness of tissues and cells isolated from Canine Mammary Tumours (CMTs). TSPO is also readily upregulated in reprogrammed mammary tumour cells following long-term deprivation of oestrogen or exposure to the endocrine chemotherapeutic (ET) agent Tamoxifen. The latter triggers mitochondrial handling of cholesterol which is facilitated by TSPO whose upregulation reduces susceptibility to Tamoxifen. TSPO binding ligands boost, on the other hand, the efficacy of Tamoxifen and Chemotherapy agents. In aggressive canine mammary tumour cells, TSPO repression impairs the NF-kB pattern thus confirming the pro-survival role of the NAM uncovered in the human counterpart. Mitochondrial cholesterol handling via TSPO emerges therefore as a signature in the aggressive reprogramming of CMTs thus advancing our understanding of the molecular mechanisms underpinning this pathology. A novel target mechanism to improve bio-marking and therapeutic protocols is here proposed.

Knock-out of CD73 delays the onset of HR-negative breast cancer by reprogramming lipid metabolism and is associated with increased tumor mutational burden

ObjectiveCD73 (ecto-5′-nucleotidase, NT5E), a cell-surface enzyme converting 5′-AMP to adenosine, is crucial for cancer progression. However, its role in the tumorigenesis process remains mostly obscure. We aimed to demonstrate CD73's role in breast cancer (BC) tumorigenesis through metabolic rewiring of fatty acid metabolism, a process recently indicated to be regulated by BC major prognostic markers, hormone receptors (HR) for estrogen (ER), and progesterone (PR). MethodsA murine model of chemically induced mammary gland tumorigenesis was applied to analyze CD73 knock-out (KO)-induced changes at the transcriptome (RNA-seq), proteome (IHC, WB), and lipidome (GC-EI-MS) levels. CD73 KO-induced changes were correlated with scRNA-seq and bulk RNA-seq data for human breast tissues and BCs from public collections and confirmed at the proteome level with IHC or WB analysis of BC tissue microarrays and cell lines. ResultsCD73 KO delayed the onset of HR/PR-negative mammary tumors in a murine model. This delay correlated with increased expression of genes related to biosynthesis and β-oxidation of fatty acids (FAs) in the CD73 KO group at the initiation stage. STRING analysis based on RNA-seq data indicated an interplay between CD73 KO, up-regulated expression of PR-coding gene, and DEGs involved in FA metabolism, with PPARγ, a main regulator of FA synthesis, as a main connective node. In epithelial cells of mammary glands, PPARγ expression correlated with CD73 at the RNA level. With cancer progression, CD73 KO increased the levels of PUFAn3/6 (polyunsaturated omega 3/6 FAs), known ligands of PPARγ and target for lipid peroxidation, which may lead to oxidative DNA damage. It correlated with the downregulation of genes involved in cellular stress response (Mlh1, Gsta3), PR–or CD73-dependent changes in the intracellular ROS levels and expression or activation of proteins involved in DNA repair or oxidative stress response in mammary tumor or human BC cell lines, increased tumor mutational burden (TMB) and genomic instability markers in CD73 low HR-negative human BCs, and the prolonged onset of tumors in the CD73 KO HR/PR-negative group. ConclusionsCD73 has a significant role in tumorigenesis driving the reprogramming of lipid metabolism through the regulatory loop with PR and PPARγ in epithelial cells of mammary glands. Low CD73 expression/CD73 KO might enhance mutational burden by disrupting this regulatory loop, delaying the onset of HR-negative tumors. Our results support combining therapy targeting the CD73-adenosine axis and tumor lipidome against HR-negative tumors, especially at their earliest developmental stage.

USP11 deubiquitinates E-cadherin and maintains the luminal fate of mammary tumor cells to suppress breast cancer

Basal-like breast cancer may originate from luminal epithelial or cancerous cells. Inadequately repaired DNA damage impairs luminal differentiation and promotes aberrant luminal to basal trans-differentiation in mammary epithelial cells (MECs). Ubiquitin-specific peptidase 11 (USP11), a deubiquitinase, plays a critical role in DNA damage repair. The role of USP11 in controlling mammary cell differentiation and tumorigenesis remains poorly understood. We generated Usp11 knockout mice and breast cancer cell lines expressing wild-type (WT) and mutant form of USP11. By using these mutant mice, cell lines, and human USP11-deficient and -proficient breast cancer tissues, we tested how USP11 controls mammary cell fate. We generated Usp11 knock-out mice and found that deletion of Usp11 reduced the expression of E-cadherin and promoted DNA damage in MECs. Overexpression of WT USP11, but not a deubiquitinase-inactive mutant form of USP11, promoted luminal differentiation, enhanced DNA damage repair, and suppressed tumorigenesis in mice. Mechanistically, we found that USP11 enhanced the protein expression of E-cadherin dependent on its deubiquitinase activity, and that USP11 deubiquitinated E-cadherin at K738. We discovered that USP11 bound to E-cadherin through its C-terminal region. In human breast cancers, expression of USP11 was positively correlated with that of E-cadherin, and high USP11 predicted better recurrence-free survival. Our findings provide compelling genetic and biochemical evidence that USP11 not only promotes DNA damage repair but also deubiquitinates E-cadherin and maintains the luminal feature of mammary tumor cells, thereby suppressing luminal breast cancer.

Comparative in vitro and in silico analysis of the ability of basic Asp49 phospholipase A2 and Lys49-phospholipase A2-like myotoxins from Bothrops diporus venom to inhibit the metastatic potential of murine mammary tumor cells and endothelial cell tubulogenesis: Asp49 vs Lys49 phospholipases A2: Inhibition of metastasis and angiogenesis

Snake venoms are a complex mixture of proteins and polypeptides that represent a valuable source of potential molecular tools for understanding physiological processes for the development of new drugs. In this study two major PLA2s, named PLA2-I (Asp49) and PLA2-II (Lys49), isolated from the venom of Bothrops diporus from Northeastern Argentina, have shown cytotoxic effects on LM3 murine mammary tumor cells, with PLA2-II-like exhibiting a stronger effect compared to PLA2-I. At sub-cytotoxic levels, both PLA2s inhibited adhesion, migration, and invasion of these adenocarcinoma cells. Moreover, these toxins hindered tubulogenesis in endothelial cells, implicating a potential role in inhibiting tumor angiogenesis. All these inhibitory effects were more pronounced for the catalytically-inactive toxin. Additionally, in silico studies strongly suggest that this PLA2-II-like myotoxin could effectively block fibronectin binding to the integrin receptor, offering a dual advantage over PLA2-I in interacting with the αVβ3 integrin. In conclusion, this study reports for the first time, integrating both in vitro and in silico approaches, a comparative analysis of the antimetastatic and antiangiogenic potential effects of two isoforms, an Asp49 PLA2-I and a Lys49 PLA2-II-like, both isolated from Bothrops diporus venom.

HUNK as a key regulator of tumor-associated macrophages in triple negative breast cancer

ABSTRACT Triple-negative breast cancer (TNBC) lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). TNBC tumors are not sensitive to endocrine therapy, and standardized TNBC treatment regimens are lacking. TNBC is a more immunogenic subtype of breast cancer, making it more responsive to immunotherapy intervention. Tumor-associated macrophages (TAMs) constitute one of the most abundant immune cell populations in TNBC tumors and contribute to cancer metastasis. This study examines the role of the protein kinase HUNK in tumor immunity. Gene expression analysis using NanoString’s nCounter PanCancer Immune Profiling panel identified that targeting HUNK is associated with changes in the IL-4/IL-4 R cytokine signaling pathway. Experimental analysis shows that HUNK kinase activity regulates IL-4 production in mammary tumor cells, and this regulation is dependent on STAT3. In addition, HUNK-dependent regulation of IL-4 secreted from tumor cells induces polarization of macrophages into an M2-like phenotype associated with TAMs. In return, IL-4 induces cancer metastasis and macrophages to produce epidermal growth factor. These findings delineate a paracrine signaling exchange between tumor cells and TAMs regulated by HUNK and dependent on IL-4/IL-4 R. This highlights the potential of HUNK as a target for reducing TNBC metastasis through modulation of the TAM population.

AGR2-mediated unconventional secretion of 14-3-3ε and α-actinin-4, responsive to ER stress and autophagy, drives chemotaxis in canine mammary tumor cells

BackgroundCanine mammary tumors (CMTs) in intact female dogs provide a natural model for investigating metastatic human cancers. Our prior research identified elevated expression of Anterior Gradient 2 (AGR2), a protein disulfide isomerase (PDI) primarily found in the endoplasmic reticulum (ER), in CMT tissues, highly associated with CMT progression. We further demonstrated that increased AGR2 expression actively influences the extracellular microenvironment, promoting chemotaxis in CMT cells. Unraveling the underlying mechanisms is crucial for assessing the potential of therapeutically targeting AGR2 as a strategy to inhibit a pro-metastatic microenvironment and impede tumor metastasis.MethodsTo identify the AGR2-modulated secretome, we employed proteomics analysis of the conditioned media (CM) from two CMT cell lines ectopically expressing AGR2, compared with corresponding vector-expressing controls. AGR2-regulated release of 14-3-3ε (gene: YWHAE) and α-actinin 4 (gene: ACTN4) was validated through ectopic expression, knockdown, and knockout of the AGR2 gene in CMT cells. Extracellular vesicles derived from CMT cells were isolated using either differential ultracentrifugation or size exclusion chromatography. The roles of 14-3-3ε and α-actinin 4 in the chemotaxis driven by the AGR2-modulated CM were investigated through gene knockdown, antibody-mediated interference, and recombinant protein supplement. Furthermore, the clinical relevance of the release of 14-3-3ε and α-actinin 4 was assessed using CMT tissue-immersed saline and sera from CMT-afflicted dogs.ResultsProteomics analysis of the AGR2-modulated secretome revealed increased abundance in 14-3-3ε and α-actinin 4. Ectopic expression of AGR2 significantly increased the release of 14-3-3ε and α-actinin 4 in the CM. Conversely, knockdown or knockout of AGR2 expression remarkably reduced their release. Silencing 14-3-3ε or α-actinin 4 expression diminished the chemotaxis driven by AGR2-modulated CM. Furthermore, AGR2 controls the release of 14-3-3ε and α-actinin 4 primarily via non-vesicular routes, responding to the endoplasmic reticulum (ER) stress and autophagy activation. Knockout of AGR2 resulted in increased α-actinin 4 accumulation and impaired 14-3-3ε translocation in autophagosomes. Depletion of extracellular 14-3-3ε or α-actinin 4 reduced the chemotaxis driven by AGR2-modulated CM, whereas supplement with recombinant 14-3-3ε in the CM enhanced the CM-driven chemotaxis. Notably, elevated levels of 14-3-3ε or α-actinin 4 were observed in CMT tissue-immersed saline compared with paired non-tumor samples and in the sera of CMT dogs compared with healthy dogs.ConclusionThis study elucidates AGR2’s pivotal role in orchestrating unconventional secretion of 14-3-3ε and α-actinin 4 from CMT cells, thereby contributing to paracrine-mediated chemotaxis. The insight into the intricate interplay between AGR2-involved ER stress, autophagy, and unconventional secretion provides a foundation for refining strategies aimed at impeding metastasis in both canine mammary tumors and potentially human cancers.

Enhancing the Anti-Tumor Efficacy of NK Cells on Canine Mammary Tumors through Resveratrol Activation.

In order to explore the therapeutic effect of Resveratrol (Res)-activated Natural Killer (NK) cells on canine mammary tumors, this study employed a range of assays, including wound healing, colony formation, Transwell, flow cytometry, and Western blot experiments, to investigate the impact of Res-pretreated NK cells on canine mammary tumor cells in vitro. Additionally, a tumor-bearing mouse model was utilized to further analyze the therapeutic effects of Res-pretreated NK cells in vivo. The results showed that Res enhances the capacity of NK cells to induce apoptosis, pyroptosis, and ferroptosis in canine breast tumor cells, while also augmenting their influence on the migration, invasion, and epithelial-mesenchymal transition of these cells. Furthermore, pretreatment of NK cells with Res significantly amplified their inhibitory effect on breast tumor growth in vivo and promoted tumor tissue apoptosis. Additionally, Res enhanced the recruitment of NK cells to other immune cells in the body. In summary, Res has been shown to enhance the anti-breast-tumor effect of NK cells both in vitro and in vivo, offering a new avenue for optimizing immunotherapy for canine breast tumors.

Establishment of canine mammary gland tumor cell lines harboring PI3K/Akt activation as a therapeutic target

Canine mammary gland tumors (MGT) have a poor prognosis in intact female canines, posing a clinical challenge. This study aimed to establish novel canine mammary cancer cell lines from primary tumors and characterize their cellular and molecular features to find potential therapeutic drugs. The MGT cell lines demonstrated rapid cell proliferation and colony formation in an anchorage-independent manner. Vimentin and α-SMA levels were significantly elevated in MGT cell lines compared to normal canine kidney (MDCK) cells, while CDH1 expression was either significantly lower or not detected at all, based on quantitative real-time PCR (qRT-PCR) analysis. Functional annotation and enrichment analysis revealed that epithelial-mesenchymal transition (EMT) phenotypes and tumor-associated pathways, particularly the PI3K/Akt signaling pathway, were upregulated in MGT cells. BYL719 (Alpelisib), a PI3K inhibitor, was also examined for cytotoxicity on the MGT cell lines. The results show that BYL719 can significantly inhibit the proliferation of MGT cell lines in vitro. Overall, our findings suggest that the MGT cell lines may be valuable for future studies on the development, progression, metastasis, and management of tumors.

Abstract PO3-09-05: Potential novel treatments for high-risk subsets of breast cancer in postpartum and African American women

Abstract Semaphorin 7a (SEMA7A) is a neuroimmune molecule first recognized for its roles in axonal guidance and inflammation. More recently, SEMA7A has emerged as a driver of tumor progression in multiple types of cancer including lung, glioblastoma and breast. Our studies have focused on the roles of SEMA7A in promoting tumor cell growth and survival as well as invasion and metastasis in mouse models including xenograft and syngeneic. Using patient samples and datamining we have shown that SEMA7A can predict for recurrence in women with postpartum breast cancer (PPBC), or breast cancers diagnosed within 10 years of recent childbirth, and SEMA7A mRNA expression in TCGA is highest in young and African American (AA) women with BC, who typically have poor prognosis. Additionally, our analysis of the Cancer Genome Atlas (TCGA) breast cancer (n=593) and METABRIC cohorts (n=2,136) revealed that SEMA7A is increased in invasive disease and in the top 9% and 27% of upregulated genes (p=1.09E-19&p=0.009), respectively. Additionally, ~1.2 (TCGA) and ~1.1 (METABRIC) fold increases in SEMA7A mRNA conferred significantly decreased 5-year survival rates (p=0.009&p=0.002) and SEMA7A was in the top 4% of mRNAs upregulated in patients who died within 5 years of diagnosis 20,24-26. Cumulatively, these results suggest that identifying therapeutic vulnerabilities of SEMA7A+BC, or direct targeting of SEMA7A, could improve prognosis for these high-risk populations. We have identified several targets in pre-clinical models of SEMA7A+BC that include clinically available, FDA approved drugs, as well as novel inhibitors that exhibit efficacy. In published studies, we have shown that venetoclax, a Bcl-2 inhibitor, reverses ER+SEMA7A+BC resistance to endocrine therapy in mouse models. In unpublished studies, we have extended our observations in ER+SEMA7A+BC to show that alpelisib and a novel PI3K kinase inhibitor, GCT-007, both inhibit growth of human and mouse mammary tumor cells. Furthermore, in models of ER-SEMA7A+BC where we have shown cells to be resistant to chemotherapy, we have utilized age matched cell lines from AA and CA women to dissect the downstream pro-survival signaling that is mediated by SEMA7A and we have shown that anti-PD-1 and anti-PD-L1 therapies are efficacious in reducing tumor growth in vivo. Finally, we have developed a novel monoclonal antibody-based therapy that directly targets SEMA7A signaling via pro-survival pathways and inhibits tumor growth in vivo and in vitro. Collectively our results suggest that SEMA7A+BC should be identified clinically, and alternative treatments advised for this high-risk subset of breast cancer. Citation Format: Traci Lyons, Lyndsey Crump, Rachel Steinmetz, Kelsey Kines, Heather Fairchild, Alan Elder. Potential novel treatments for high-risk subsets of breast cancer in postpartum and African American women [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 PO3-09-05.

Myocardial Blood Flow in Newly Diagnosed Breast Cancer Patients at Rest and During Exercise

Heart depends critically on continuous supply of blood, but it is unknown whether cancer, without any treatments, affects myocardial blood flow (MBF) at rest or during exercise. This study therefore aimed at measuring MBF in cancer patients and control subjects and it was hypothesized that MBF is affected by cancer. The study included recently-diagnosed breast cancer patients (n=18) who had not started their oncologic treatments and age-matched female control participants (n=32). Controls were women referred to cardiac diagnostic testing but who were by this testing judged to be free of obstructive coronary artery disease. MBF was quantified with [15O]H2O positron emission tomography (PET) at rest in both groups and additionally during 10-min supine bicycling exercise in the breast cancer patients. Furthermore, cardiac morphological changes were analyzed with a breast cancer mice-model four weeks after the inoculation of 13TC mammary tumor cells. Respective mice without tumors served as controls. Resting heart rate (HR) and rate pressure product (RPP) correlated positively with resting MBF, but were similar in both groups resulting also in similar resting MBF in cancer patients and controls. MBF increased significantly from rest during exercise in breast cancer patients (p<0.0001) and exercising MBF correlated positively with the histologic grade of cancer (r=0.54, p=0.021). However, cancer grade did not associate with exercise intensity measures such as HR, RPP or HR percentage from age-predicted maximal HR. In the mouse model, the breast cancer did not affect heart weight, cardiomyocyte size, myocardial capillary density, or capillary-to-myocyte size ratio. In conclusion, resting MBF in humans or myocardial capillarity in mice appear not to be affected by breast cancer. However, the more severe is the histologic grade of cancer, the higher is the MBF during exercise in patients with breast cancer, independently of the intensity of the exercise suggesting dysregulation of myocardial blood supply with cancer. This novel finding requires further investigations. This study was financially supported by Academy of Finland and Hospital District of South-West Finland. 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.

Anticancer Effects of Mitoquinone via Cell Cycle Arrest and Apoptosis in Canine Mammary Gland Tumor Cells.

Treating female canine mammary gland tumors is crucial owing to their propensity for rapid progression and metastasis, significantly impacting the overall health and well-being of dogs. Mitoquinone (MitoQ), an antioxidant, has shown promise in inhibiting the migration, invasion, and clonogenicity of human breast cancer cells. Thus, we investigated MitoQ's potential anticancer properties against canine mammary gland tumor cells, CMT-U27 and CF41.Mg. MitoQ markedly suppressed the proliferation and migration of both CMT-U27 and CF41.Mg cells and induced apoptotic cell death in a dose-dependent manner. Furthermore, treatment with MitoQ led to increased levels of pro-apoptotic proteins, including cleaved-caspase3, BAX, and phospho-p53. Cell cycle analysis revealed that MitoQ hindered cell progression in the G1 and S phases in CMT-U27 and CF41.Mg cells. These findings were supported using western blot analysis, demonstrating elevated levels of cleaved caspase-3, a hallmark of apoptosis, and decreased expression of cyclin-dependent kinase (CDK) 2 and cyclin D4, pivotal regulators of the cell cycle. In conclusion, MitoQ exhibits in vitro antitumor effects by inducing apoptosis and arresting the cell cycle in canine mammary gland tumors, suggesting its potential as a preventive or therapeutic agent against canine mammary cancer.

Effect of Melatonin on Chemoresistance Exhibited by Spheres Derived from Canine Mammary Carcinoma Cells.

Mammary cancer is a frequent disease in female dogs, where a high proportion of cases correspond to malignant tumors that may exhibit drug resistance. Within the mammary tumor microenvironment, there is a cell subpopulation called cancer stem cells (CSCs), which are capable of forming spheres in vitro and resisting anti-tumor treatments, partly explaining the recurrence of some tumors. Previously, it has been described that spheres derived from canine mammary carcinoma cells CF41.Mg and REM 134 exhibit stemness characteristics. Melatonin has shown anti-tumor effects on mammary tumor cells; however, its effects have been poorly evaluated in canine mammary CSCs. This study aimed to analyze the effect of melatonin on the chemoresistance exhibited by stem-like neoplastic cells derived from canine mammary carcinoma to cytotoxic drugs such as doxorubicin and mitoxantrone. CF41.Mg and REM 134 cells were cultured in high-glucose DMEM supplemented with fetal bovine serum and L-glutamine. The spheres were cultured in ultra-low attachment plates in DMEM/F12 medium without fetal bovine serum and with different growth factors. The CD44+/CD24-/low phenotype was analyzed by flow cytometry. The viability of sphere-derived cells (MTS reduction) was studied in the presence of melatonin (0.1 or 1 mM), doxorubicin, mitoxantrone, and luzindole. In addition, the gene (RT-qPCR) of the multidrug resistance bombs MDR1 and ABCG2 were analyzed in the presence of melatonin. Both cell types expressed the MT1 gene, which encodes the melatonin receptor MT1. Melatonin 1 mM does not modify the CD44+/CD24-/low phenotype; however, the hormone reduced viability (p < 0.0001) only in CF41.Mg spheres, without inducing an additive effect when co-incubated with cytotoxic drugs. These effects were independent of the binding of the hormone to its receptor MT1, since, by pharmacologically inhibiting them, the effect of melatonin was not blocked. In CF41.Mg spheres, the relative gene expression of ABCG2 and MDR1 was decreased in response to the hormone (p < 0.001). These results indicate that melatonin negatively modulates the cell survival of spheres derived from CF41.Mg cells, in a way that is independent of its MT1 receptor. These effects did not counteract the resistance to doxorubicin and mitoxantrone, even though the hormone negatively regulates the gene expression of MDR1 and ABCG2.

Abstract 251: MCAM controls mammary cell state in luminal progenitor-derived breast cancer and alveologenesis

Abstract To establish and maintain functional and properly formed tissues, cells must integrate cues from their environment into fate decisions. External cues—from other cells and the extracellular matrix for instance—must be met with appropriate responses to ensure cell fate decisions that control lineage plasticity and favor proper development, maintenance, or regeneration of tissues while suppressing neoplastic transformation. MCAM (CD146; MUC18; S-endo-1; and Gicerin) is an integral membrane glycoprotein whose misexpression is associated with a variety of epithelial cancers, including breast cancer. However, the mechanisms by which MCAM conveys extracellular cues into malignant cellular outputs is not well understood. Our observation that MCAM is normally expressed in transplantable fetal and adult mammary stem cells (MaSCs) with multilineage potential, suggested it could control mammary cell state plasticity in both neoplastic and normal mammary tissue. Using a plastic, mouse mammary tumor cell line derived from the MMTV-PyMT mouse (Py230) that has been reported to exhibit mammary stem cell and luminal progenitor features, we tested the role of Mcam in controlling the tumorigenicity and lineage/cell-state relationships of mammary tumor cells. We found that Mcam knockdown in Py230 cells increases STAT3 expression, activation, and downstream target transcription, leading to a shift in the predominant cell state away from a luminal progenitor state toward more differentiated alveolar and basal phenotypes. Mechanistically, these changes involve altered activity of casein kinase II (CK2) against multiple substrates including STAT3 and PTEN. This effect may be mediated by direct coupling and sequestration of CK2 to various substrates via the cytoplasmic tail of MCAM. We have also found that inhibition of Ck2 or Stat3 reversed the transcriptional state change elicited by Mcam knockdown. In grafted tumors in vivo, this state switch correlates with reduced overall tumorigenicity and attenuated expression of Sox10, a gatekeeper of neural crest-like invasive features. In the normal gland, we hypothesize that this activity regulates multilineage stem cell potential upon transplantation and multilineage regenerative potential across lactation/involution cycles as we found reciprocal expression patterns for MCAM and STAT3 in alveolar mammary epithelial cells. These data point to an integral role for MCAM in lineage plasticity of normal mammary epithelial cells that is co-opted during transformation to potentiate tumor cell plasticity, progression, and evasion of targeted cancer therapies. Citation Format: Brooke L. Gates, Ozlen Balcioglu, David W. Freeman, Berhane M. Hagos, Benjamin T. Spike. MCAM controls mammary cell state in luminal progenitor-derived breast cancer and alveologenesis [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 251.

Abstract 6877: Progesterone promotes immunosuppression in the murine mammary gland by causing T cell death

Abstract Breast Cancer is the most common cancer diagnosed in women in the United States. Second only to lung cancer, breast cancer results in the greatest number of cancer deaths for women. Hormone receptor positive (HR+) breast cancers - cancers expressing the nuclear receptors for steroid hormones estrogen and progesterone, termed the estrogen receptor (ER) and progesterone receptor (PR) - make up the largest proportion of diagnosed breast cancers by a significant margin. So, although the HR+ subtype is less aggressive compared to others, it continues to be the largest contributor to breast cancer mortality. Treatment consists of anti-endocrine therapies, largely targeting ER/estrogen, the established drivers of breast cancer growth. Most women respond well to these therapies, but for women who do not, there are few alternative options. With the advent of immunotherapy and its successes in treating and controlling certain tumor types, many were hopeful that it could be employed for breast cancer as well. However, breast cancers, especially HR+ breast cancers, are considered “immune cold.” They lack high proportions of tumor-infiltrating lymphocytes (TILs), have low neoantigen production, and high percentages of immunosuppressive cells. A contributing factor could be the hormones present in the tumor microenvironment. The accepted paradigm is that lifetime exposure to estrogens drives the development of HR+ breast cancer, but both estrogen and progesterone are part of the normal menstrual cycle. Prior work from our lab has uncovered a novel immune-modulatory role for progesterone, pivotal to promoting the growth of PR-positive mammary tumors. Recent preliminary data from our lab show that progesterone treatment conveys immune protection against T cell killing in a co-culture with E0771 mammary gland tumor cells. However, when activated in monoculture, T cells exposed to increasing concentrations of progesterone have no differing expression of cell surface activation or exhaustion markers, implying that progesterone is not eliciting this effect by interfering with the T cell activation cascade nor is it inducing premature exhaustion. Interestingly, progesterone treatment instead leads to a concentration-dependent increase in T cell death compared to the untreated control. In vivo, these results are supported as progesterone treatment decreases the amount of total CD3+ T cells, and specifically the cytotoxic CD8+ subset, in the mammary glands of mice. These results suggest that progesterone could modulate the breast and tumor microenvironment, providing tumor cells with protection from immunosurveillance and contributing to HR+ breast cancer development. These data also argue for the use of anti-progestins to be added to the HR+ breast cancer treatment regimen to boost anti-tumor immune activity. Citation Format: Amanda Heard, Lauryn R. Werner, Eilidh I. Chowanec, Harmony Saunders, Julio Tinoco, Zachary C. Hartman, Christy R. Hagan. Progesterone promotes immunosuppression in the murine mammary gland by causing T cell death [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 6877.

Abstract 5364: Progesterone receptor modulates the antigen processing and presentation machinery decreasing MHC class I expression on tumors

Abstract Hormone receptor (HR) positive breast cancers, which account for approximately 75% of all breast cancers and express both estrogen receptor (ER) and progesterone receptor (PR), have been the subject of much research. As such, successful anti-estrogen/ER-based therapies have been very successful in the treatment of HR+ breast cancer. Despite this success, over 1/3 of patients will eventually progress on current ER/estrogen-targeted therapies, underscoring the need for new targeted therapies in HR+ breast cancer. Unlike ER, the role of PR in breast cancer progression has received far less attention. In a previous study, we found that a mouse mammary tumor cell line E0771, modified to express the mouse progesterone receptor (mPR) and the OVA peptide, demonstrated decreased T cell-mediated cell death when treated with progesterone compared to the control group. Progesterone-mediated protection from T-cell death was only observed in mPR+ cell lines. Flow analysis of the E0771-Ova-mPR cells also revealed a decrease in MHC Class I presentation in progesterone-treated cells compared to a vehicle control. To further explore the role of the machinery required for antigen processing and presentation of MHC Class I molecules, we conducted additional experiments using the E0771 cell line. Our results showed that treatment with progesterone led to a reduction in RNA levels of all the machinery required for antigen processing and presentation (APP). Based on these findings, we hypothesize that activation of the progesterone receptor by progesterone may decrease MHC Class I expression by regulating APP. Our results showed that treatment with progesterone resulted in a reduction in RNA levels of Tap1, Tap2, Tapbp, Nlrc5, B2m, and Psmb8, which are essential for APP. We therefore propose that activation of the progesterone receptor by progesterone may decrease MHC Class I expression by directly modulating the APP pathway. The findings of this study may have significant implications for our understanding of how breast cancer cells evade T-cell mediated cytotoxicity. Citation Format: Julio Tinoco, Lauryn Werner, Eilidh Chowanec, Harmony Saunders, Sun Xiaopeng, Jay Gertz, Justin Balko, Zachary C. Hartman, Christy Hagan. Progesterone receptor modulates the antigen processing and presentation machinery decreasing MHC class I expression on tumors [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 5364.

Abstract 3971: Progesterone impacts regulatory T cell activity to promote immunosuppression in the mammary gland

Abstract Estrogen and progesterone signaling together drive hormone-receptor positive breast cancer growth and progression. However, there have been limited studies on the independent role that progesterone and its receptor, the progesterone receptor (PR), play in the development of breast cancer. Studies in the Hagan lab have shown that progesterone signaling promotes mammary tumor growth and changes the immune landscape of the mammary gland towards immunosuppression. Regulatory T-cells (Tregs) are immune cells known to promote immunosuppression in the tumor microenvironment. The data from our lab shows that among hormone receptor positive breast cancers, higher levels of PR expression correlates to higher levels of Tregs in the tumor microenvironment. To determine if progesterone signaling increases the number of Tregs in the tumor-bearing mammary gland, we used a syngeneic orthotopic murine tumor model, E0771 cells, engineered to express mouse PR or control empty vector. Mice were treated with progesterone or placebo for 7 days before implantation of the modified E0771 cells. The results of this study show that progesterone promoted tumor growth, and flow cytometry analysis at tumor endpoint showed that PR-positive tumors treated with progesterone harbored more Tregs than mice treated with placebo. Additionally, initial studies using flow cytometry and RNA-seq indicate increased Treg activity following progesterone treatment in PR+ tumor-bearing mice. As progesterone treatment promoted tumor growth and Treg recruitment in progesterone receptor-positive tumors, these data imply that progesterone treatment may promote the release of secreted factors impacting the immune cells in the mammary microenvironment. To determine if progesterone treatment results in cytokine or chemokine changes that may affect Treg recruitment, cytokine arrays and enzyme-linked immunosorbent assays (ELISAs) were performed using cell culture supernatant from murine mammary tumor cells expressing progesterone receptor (E0771-PR) treated with progesterone (0-72 hours). E0771-PR cells treated with progesterone showed higher levels of cytokines and chemokines that have been linked to Treg recruitment and differentiation, such as MCSF. Our findings demonstrate that progesterone signaling promotes an immune suppressed microenvironment in the mammary gland through an increase in Tregs. This evidence provides rationale to investigate the use of anti-progestins as a mechanism to overcome the immune-cold tumor microenvironment seen in progesterone receptor positive breast tumors. Citation Format: Eilidh I. Chowanec, Lauryn R. Werner, Christy R. Hagan. Progesterone impacts regulatory T cell activity to promote immunosuppression in the mammary gland [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 3971.