Breast Tumor Growth Research Articles

Nuclear receptor 4A1 (NR4A1) antagonists target paraspeckle component 1 (PSPC1) in cancer cells.

Paraspeckles compound 1 (PSPC1) is a multifunctional protein that plays an important role in cancer cells, where PSPC1 is a master regulator of pro-oncogenic responses that includes activation of TGFβ (TGFβ1),TGFβ-dependent EMT, and metastasis. The pro-oncogenic activities of PSPC1 closely resembled those observed for the orphan nuclear receptor 4A1 (NR4A1, Nur77) and knockdown of NR4A1 decreased expression of PSPC1 in MDA-MB-231 breast, H1299 lung, and SNU449 liver cancer cells. Similar results were observed in these same cell lines after treatment with bisindole-derived (CDIMs) NR4A1 antagonists. Moreover, PSPC1-dependent regulation of TGFβ, genes associated with cancer stem cells and epithelial to mesenchymal transition (EMT) were also downregulated after NR4A1 silencing or treatment of breast, lung, and liver cancer cells with CDIM/NR4A1 antagonists. Results of chromatin immunoprecipitation (ChIP) assays suggest that NR4A1 regulates PSPC1 through interaction with an NBRE sequence in the PSPC1 gene promoter. These results coupled with in vivo studies showing that NR4A1 antagonists inhibit breast tumor growth and downregulate PSPC1 in tumors indicate that the pro-oncogenic nuclear PSPC1 factor can be targeted by CDIM/NR4A1 antagonists.

Anemoside A3 activates TLR4-dependent M1-phenotype macrophage polarization to represses breast tumor growth and angiogenesis

The polarization of macrophages has been previously demonstrated to be closely related to immune and inflammatory processes in the tumorigenesis and progression of breast cancer. In the present study, Anemoside A3 (A3), an active compound from Pulsatilla saponins, was screened out and polarized M0 macrophages into the classically activated macrophages (M1-phenotype). We found that A3 is an activator of TLR4/NF-κB/MAPK signaling pathway. A3 increased the expression of CD86+ (a marker of M1 macrophage) in M0 macrophage, and increased the typical M1 macrophage pro-inflammatory cytokines TNF-α, and IL-12 expression in a TLR4-dependent manner. A macrophage-cancer cell co-culture system was established to evaluate whether A3 can could switch tumor-associated macrophages (TAMs) to the M1-phenotype. In the co-culture system, A3 increased the expression of IL-12 in macrophages, whereby suppressing MCF-7 breast cancer cell line proliferation and VEGF-mediated angiogenesis. Moreover, A3 induced M1 macrophage polarization in the 4 T1 murine breast cancer model and effectively inhibited tumor growth and tumor angiogenesis. Collectively, these findings indicated that A3 induced M1 macrophages polarization to repress breast tumorigenesis via targeting the TLR4/NF-κB/MAPK signaling pathway. This study provides a rationale for utilizing traditional Chinese medicine extracts in the immunotherapy of breast cancer.

Transcriptome study of oleanolic acid in the inhibition of breast tumor growth based on high-throughput sequencing.

The function of oleanolic acid (OA) in various types of cancer has been reported frequently, especially for breast cancer. However, the regulation of breast tumor growth in response to OA treatment has not been studied in depth. Here, we first explored the effect of OA treatment on breast tumors in vitro and in vivo and then used RNA-seq technology to study the effect and molecular mechanism of OA treatment of MCF-7 cells, particularly at the level of functional genomics. The results showed that 40 μM OA treatment could significantly inhibit the proliferation and induce the apoptosis of MCF-7 cells. Through analysis of RNA sequencing data quality and differentially expressed genes (DEGs), 67 significantly downregulated genes and 260 significantly upregulated genes were identified to be involved in OA treatment of MCF-7 cells. Among these genes, 43 unique DEGs were enriched in several signaling pathways and Gene Ontology terms, such as p53 signaling pathway, TNF signaling pathway and mTOR signaling pathway. Six downregulated genes, including THBS1, EDN1, CACNG4, CCN2, AXIN2 and BMP4, as well as six upregulated genes, including ATF4, SERPINE1, SESN2, PPARGC1A, EGR1 and JAG1, were selected as target genes in response to OA treatment. The inhibitory effect of OA on breast cancer was also found in the following mouse experiments. Our study provides evidence and molecular support for the treatment of breast cancer with OA.

Inhibition of Breast Tumour Growth with Intravenously Administered PRKCA siRNA- and PTEN Tumour Suppressor Gene-Loaded Carbonate Apatite Nanoparticles

Gene therapy aims to silence an oncogene through RNA interference, or replace an abnormal tumour suppressor via gene augmentation. In this study, we intended RNA interference for PRKCA oncogene and gene augmentation for PTEN tumour suppressor with a view to reduce tumour growth in a mouse model of breast cancer. Inorganic carbonate apatite nanoparticles (CA NPs) were utilized to deliver the synthetic siRNA and the purified gene-carrying plasmid DNA both in vitro and in vivo. Effects of PRKCA siRNA- and PTEN plasmid-loaded NPs on viability of MCF-7, MDA-MB-231 and 4T1 breast cancer cells were assessed by MTT assay. The cell viability data in MCF-7 cell line demonstrated that combined delivery of PRKCA specific siRNA and PTEN plasmid with CA NPs had an additive effect to significantly decrease cellular growth compared to individual treatments. In addition, we observed a similar pattern of cumulative influence for combined treatment in triple negative MDA-MB-231 breast cancer cell line. Upon treatment with PRKCA siRNA+PTEN plasmid-loaded NPs, a remarkable decrease in the phosphorylated form of AKT protein of PI3K/AKT pathway was observed in Western blot, indicative of diminished proliferative signal. Moreover, in vivo study in MCF-7 xenograft breast cancer mouse model demonstrated that the rate of growth and final tumour volume were reduced significantly in the mouse group that received intravenous treatment of PRKCA siRNA+NPs, and PTEN plasmid+NPs. Our findings demonstrated that PRKCA siRNA and PTEN plasmid loaded into CA NPs attenuated breast tumour growth, suggesting their therapeutic potential in the treatment of breast cancer.

Effects of Simvastatin on Breast Carcinoma Cell Proliferation and Apoptosis via Transforming Growth Factor-β1/Smad3 Pathway

Objective: To investigate the function and causative role of simvastatin (Sim) in breast carcinoma cell apoptosis as well as proliferation. Methods: 20 breast carcinoma patients requiring surgery were treated with Sim (20 days, 30 mg), and samples of pre-treatment (pre) and post-treatment (post) were acquired. We detected tissue cell proliferation and apoptosis changes and used functional experiments to detect cell proliferation and apoptosis changes after treating not only estrogen receptor (ER)-positive (MCF-7) but also ER-negative cells (MDA-MB-231) with Sim or TGF-β1. Detection of p-Smad3 and total Smad3 protein expression changes was conducted, and we finally used in vivo experiments to assess the influence of Sim on breast tumor growth and drug safety. Results: Immunohistochemistry and TUNEL staining results showed that after treatment with Sim, breast carcinoma cell proliferation decreased and apoptosis increased. Functional experiments results showed that Sim notedly promoted the MDA-MB-231 and MCF-7 cell apoptosis, inhibiting migration, proliferation and epithelial mesenchymal transition. Moreover, TGF-β1 protein expression was strikingly lower in Sim group than that in DMSO group. When TGF-β1 and Sim were combined to use, the inhibitory ability of Sim on breast cancer cell proliferation markedly increased and the capability of TGF-β1 protein inducing p-Smad3 protein increased. In addition, after Sim treatment in mice, the tumor volume became smaller, the pathological changes weakened, and there was no significant effect on liver function and kidney function. Conclusion: Sim participates in breast cancer cell apoptosis and proliferation via regulating TGF-β1/Smad3 signal pathway.

Ubiquitination of NF-κB p65 by FBXW2 suppresses breast cancer stemness, tumorigenesis, and paclitaxel resistance.

The F-box and WD-repeat-containing protein 2 (FBXW2) plays a crucial role as an E3 ligase in regulating tumorigenesis. However, the functions of FBXW2 in breast cancer are still unknown. Here, we find that nuclear factor-kB (NF-κB) p65 is a new substrate of FBXW2. FBXW2 directly binds to p65, leading to its ubiquitination and degradation. Interestingly, p300 acetylation of p65 blocks FBXW2 induced p65 ubiquitination. FBXW2-p65 axis is a crucial regulator of SOX2-induced stemness in breast cancer. Moreover, FBXW2 inhibits breast tumor growth by regulating p65 degradation in vitro and in vivo. FBXW2 overexpression abrogates the effects of p65 on paclitaxel resistance in vitro and in vivo. Furthermore, FBXW2 induced p65 degradation is also confirmed in FBXW2-knockout mice. Our results identify FBXW2 as an important E3 ligase for p65 degradation, which provide insights into the tumor suppressor functions of FBXW2 in breast cancer.

SHOX2 cooperates with STAT3 to promote breast cancer metastasis through the transcriptional activation of WASF3

BackgroundMetastasis is most often the root cause of cancer-related death. Human short stature homeobox 2 (SHOX2), a homeodomain transcription factor, is a novel inducer of epithelial-to-mesenchymal transition in breast cancer cells, though its exact role and underlying mechanisms in metastasis are not well understood.MethodsTCGA analysis was performed to identify the clinical relevance of SHOX2 in breast cancer. Gene depletion was achieved by short hairpin RNA and small interfering RNA. Molecular regulations and alterations were assessed by Western blotting, immunoprecipitation, immunohistochemistry, qRT-PCR, chromatin immunoprecipitation coupled with qPCR (ChIP-qPCR), and ChIP/re-ChIP. The impact of SHOX2 signaling on tumor growth and metastasis was evaluated in orthotopic breast tumor mice.ResultsThe expression level of SHOX2 is strongly associated with poor distant metastasis-free survival in breast cancer patients and inactivation of SHOX2 suppresses breast tumor growth and metastasis in mice. In breast cancer cells, SHOX2 directly activates Wiskott-Aldridge syndrome protein family member 3 (WASF3), a metastasis-promoting gene, at the transcriptional level, leading to a significant increase in metastatic potential. Mechanistically, SHOX2 activates signal transducer and activator of transcription 3 (STAT3) and recruits it to the WASF3 promoter, where STAT3 cooperates with SHOX2 to form a functional immunocomplex to promote WASF3 transcriptional activity in breast cancer cells. WASF3 knockdown abrogates SHOX2-induced metastasis, but not SHOX2-dependent tumorigenesis.ConclusionsThese findings provide a critical link between the SHOX2-STAT3-WASF3 signaling axis and metastasis and suggest that the targeting of this signaling node may represent a valuable alternative strategy for combating breast cancer metastasis.

Retinoic Acid-Loaded Dendritic Polyglycerol-Conjugated Gold Nanostars for Targeted Photothermal Therapy in Breast Cancer Stem Cells.

The existence of cancer stem cells (CSCs) poses a major obstacle for the success of current cancer therapies, especially the fact that non-CSCs can spontaneously turn into CSCs, which lead to the failure of the treatment and tumor relapse. Therefore, it is very important to develop effective strategies for the eradication of the CSCs. In this work, we have developed a CSCs-specific targeted, retinoic acid (RA)-loaded gold nanostars-dendritic polyglycerol (GNSs-dPG) nanoplatform for the efficient eradication of CSCs. The nanocomposites possess good biocompatibility and exhibit effective CSCs-specific multivalent targeted capability due to hyaluronic acid (HA) decorated on the multiple attachment sites of the bioinert dendritic polyglycerol (dPG). With the help of CSCs differentiation induced by RA, the self-renewal of breast CSCs and tumor growth were suppressed by the high therapeutic efficacy of photothermal therapy (PTT) in a synergistic inhibitory manner. Moreover, the stemness gene expression and CSC-driven tumorsphere formation were significantly diminished. In addition, the in vivo tumor growth and CSCs were also effectively eliminated, which indicated superior anticancer activity, effective CSCs suppression, and prevention of relapse. Taken together, we developed a CSCs-specific targeted, RA-loaded GNSs-dPG nanoplatform for the targeted eradication of CSCs and for preventing the relapse.

Antibiotic-induced disturbances of the gut microbiota result in accelerated breast tumor growth

SummaryThe gut microbiota’s function in regulating health has seen it linked to disease progression in several cancers. However, there is limited research detailing its influence in breast cancer (BrCa). This study found that antibiotic-induced perturbation of the gut microbiota significantly increases tumor progression in multiple BrCa mouse models. Metagenomics highlights the common loss of several bacterial species following antibiotic administration. One such bacteria, Faecalibaculum rodentium, rescued this increased tumor growth. Single-cell transcriptomics identified an increased number of cells with a stromal signature in tumors, and subsequent histology revealed an increased abundance of mast cells in the tumor stromal regions. We show that administration of a mast cell stabilizer, cromolyn, rescues increased tumor growth in antibiotic treated animals but has no influence on tumors from control cohorts. These findings highlight that BrCa-microbiota interactions are different from other cancers studied to date and suggest new research avenues for therapy development.

Phytolacca decandra 30 CH dilution as an anticancer agent in murine mammary adenocarcinoma model

Homeopathy is an effective and safe therapy that provides better quality of life and reduces the adverse effects of conventional therapy used in different diseases. However, there are few published studies showing effects of homeopathic medicines in cancer models. Considering the principle "like cures like" the Phytolocca decandra causes similar symptoms to those presented in cancer subjects. Therefore, the aim of this study was to evaluate the effects of homeopathic preparations of Phytolacca decandra in the development of murine mammary tumor. For this, 4T1 mammary adenocarcinoma cells were inoculated subcutaneously in the inguinal breast of female BALB/c mice. Then, mice were blind treated with water containing only vehicle (control) or vehicle with Phytolacca decandra dilutions (6CH, 12CH, 30CH or 200cH). Tumor growth was monitored in alternated days during 21 days after tumor cells inoculation. Then, mice were euthanized and tumor, spleen, and lungs were removed to histological analyses. Results showed that animals treated with 30CH when compared with other groups exhibited tumor growth delay and smaller tumor weight, less vascularization and smaller relative weight of the spleen and pulmonary metastases. Together, results obtained in this pilot study demonstrated that treatment with Phytolacca decandra 30CH dilution induces delayed of breast tumor growth suggesting that this dilution may be a promising alternative therapy in the treatment of breast cancer.

Hyperleptinemia in obese state renders luminal breast cancers refractory to tamoxifen by coordinating a crosstalk between Med1, miR205 and ErbB

Obese women with hormone receptor-positive breast cancer exhibit poor response to therapy and inferior outcomes. However, the underlying molecular mechanisms by which obesity/hyperleptinemia may reduce the efficacy of hormonal therapy remain elusive. Obese mice with hyperleptinemia exhibit increased tumor progression and respond poorly to tamoxifen compared to non-obese mice. Exogenous leptin abrogates tamoxifen-mediated growth inhibition and potentiates breast tumor growth even in the presence of tamoxifen. Mechanistically, leptin induces nuclear translocation of phosphorylated-ER and increases the expression of ER-responsive genes, while reducing tamoxifen-mediated gene repression by abrogating tamoxifen-induced recruitment of corepressors NCoR, SMRT, and Mi2 and potentiating coactivator binding. Furthermore, in silico analysis revealed that coactivator Med1 potentially associates with 48 (out of 74) obesity-signature genes. Interestingly, leptin upregulates Med1 expression by decreasing miR-205, and increases its functional activation via phosphorylation, which is mediated by activation of Her2 and EGFR. It is important to note that Med1 silencing abrogates the negative effects of leptin on tamoxifen efficacy. In addition, honokiol or adiponectin treatment effectively inhibits leptin-induced Med1 expression and improves tamoxifen efficacy in hyperleptinemic state. These studies uncover the mechanistic insights how obese/hyperleptinemic state may contribute to poor response to tamoxifen implicating leptin-miR205-Med1 and leptin-Her2-EGFR-Med1 axes, and present bioactive compound honokiol and adipocytokine adiponectin as agents that can block leptin’s negative effect on tamoxifen.

Calcification‐Based Cancer Diagnosis and Therapy

In nature, calcium deposition is a common biological process in mammals that shapes mechanical structures and creates the functions of bones and teeth, and causes calculi formation. Spontaneous tumor calcification and regional lymph node calcification in colorectal cancer, lung cancer, and glioblastoma have been proven to be benign prognostic factors in the clinic. In line with this concept, we introduce the idea and lead the compound development of artificially inducing bionic calcification around the surface of cancer cells. This process is shown to have excellent effects in the inhibition of growth and metastases of cervical, breast, and lung tumors, as well as superb performance in early-stage diagnosis. Therefore, we predict that this concept may open the door for cancer targeting calcification therapy and diagnosis and provide an outlook for a new avenue in anticancer drug development.

A phosphatidic acid-binding lncRNA SNHG9 facilitates LATS1 liquid-liquid phase separation to promote oncogenic YAP signaling.

Long noncoding RNAs (lncRNAs) are emerging as a new class of important regulators of signal transduction in tissue homeostasis and cancer development. Liquid-liquid phase separation (LLPS) occurs in a wide range of biological processes, while its role in signal transduction remains largely undeciphered. In this study, we uncovered a lipid-associated lncRNA, small nucleolar RNA host gene 9 (SNHG9) as a tumor-promoting lncRNA driving liquid droplet formation of Large Tumor Suppressor Kinase 1 (LATS1) and inhibiting the Hippo pathway. Mechanistically, SNHG9 and its associated phosphatidic acids (PA) interact with the C-terminal domain of LATS1, promoting LATS1 phase separation and inhibiting LATS1-mediated YAP phosphorylation. Loss of SNHG9 suppresses xenograft breast tumor growth. Clinically, expression of SNHG9 positively correlates with YAP activity and breast cancer progression. Taken together, our results uncover a novel regulatory role of a tumor-promoting lncRNA (i.e., SNHG9) in signal transduction and cancer development by facilitating the LLPS of a signaling kinase (i.e., LATS1).

Mammary Epithelial and Endothelial Cell Spheroids as a Potential Functional <em>In vitro</em> Model for Breast Cancer Research

Crosstalk between mammary epithelial cells and endothelial cells importantly contributes to breast cancer progression, tumor growth, and metastasis. In this study, spheroids have been made from breast cancer cells together with vascular and/or lymphatic endothelial cells and demonstrate their applicability as an in vitro system for breast cancer research.

Anti-cancer immunoprotective effects of immunization with hydatid cyst wall antigens in a non-immunogenic and metastatic triple-negative murine mammary carcinoma model

Cancer vaccines have gained lots of attention as the future of cancer treatment. However, poor immunogenicity of tumor-associated antigens often fails to induce an efficient immune response against the tumor. Strange anti-tumor immune responses at the parasite-infected patients due to cross-reactivity have been reported in various studies. Therefore, parasite antigens with significant immunogenicity and high epitope homology with cancer antigens may activate a strong immune response against cancer cells. Herein, the sera of immunized rabbits with the hydatid cyst wall (HCW) antigens were incubated with 4 T1 mammary carcinoma cells to investigate cross-reactivity between the HCW antigens antisera and surface antigens of the breast cancer cells. Also, the SDS-PAGE profile of HCW antigens was prepared and incubated with the breast cancer patients’ sera and considerable reactivity was observed between their sera and a specific band (~27/28 kDa) according to Western blotting analyzes. Then, the protein bands with cross-reactivity with breast cancer patients’ sera were utilized for prophylactic immunizations of Balb/c mice. The immunoprotective effect of immunization with the HCW antigens caused significant inhibition of 4 T1 breast tumor growth, decrease of metastasis, and enlargement of the tumor-bearing mice survival time in comparison with PBS and pure immune adjuvant injected groups. Mass spectrometry analysis showed that the ~ 27/28 kDa band has numbers of proteins/polypeptides with a high degree of homology with cancer cells antigens which can be the reason for this cross-reactivity and anti-tumor immune response. Taking together, immunization with HCW antigens would be a promising approach in cancer immunotherapy after further investigations.

Ruyiping formula inhibits metastasis via the microRNA-134-SLUG axis in breast cancer

BackgroundMetastasis is the leading cause of death among breast cancer patients. MicroRNA-134 has been reported to have a tumor-suppressive role in breast cancer. Ruyiping (RYP), a traditional Chinese formula, has been shown with the ability to reduce breast cancer metastasis in pre-clinical studies. This present study was designed to examine whether miR-134 was involved in RYP-inhibited breast cancer metastasis.MethodsThe expression of SLUG, E-Cadherin, N-Cadherin and miR-134 in MDA-MB-231 and 4 T1 cells treated with RYP or vehicle control were determined by quantitative realtime-PCR and western blot. Invasiveness determined by transwell assay as well as SLUG gene expression determined by qPCR were detected in cells transfected with chemically synthesized miR-134 mimics or inhibitors. BALB/c mice were injected with 4 T1 cells orthotopically and fed with RYP through gavage. Breast tumor growth, metastasis and tumor expression of EMT markers were detected.ResultsCompared with the control, Ruyiping formula significantly inhibited SLUG-regulated breast cancer cells invasion. MiR-134 was induced by RYP in vitro and in vivo and was able to suppress SLUG by targeting its 3’UTR. RYP suppressed SLUG expression and cell invasion through miR-134. In 4 T1 tumor-bearing mice, RYP significantly inhibited 4 T1 tumor growth and lung metastasis, increased the levels of miR-134 and epithelial marker while decreased the levels of SLUG and mesenchymal marker.ConclusionOur data uncovered that Ruyiping formula exerts an anti-metastatic activity against breast cancer cells by regulating SLUG through miR-134. MiR-134-SLUG axis might be a promising strategy in breast cancer therapy.

Abstract 107: Identifying the role of fibrocytes in obesity-induced mammary gland fibrosis

Abstract Obesity significantly increases breast cancer risk. In addition, obese breast cancer patients have an overall worsened prognosis. The complex relationship between obesity and breast tumor growth and aggressiveness is still being examined. Within breast adipose tissue, obesity causes a state of chronic, macrophage-driven inflammation. Chronic inflammation is associated with increased extracellular matrix (ECM) deposition, however, the underlying mechanisms are not completely understood. In mouse models, increased collagen within the mammary microenvironment is a risk factor for tumor formation, as well as more aggressive tumors. To understand how obesity affects collagen deposition in the mammary gland, we used a diet-induced obesity mouse model. We demonstrated that there was significantly greater collagen deposition around the mammary ducts of high-fat diet (HFD) fed mice compared to control diet (CD) fed mice. To understand how myeloid lineage cells contribute to this fibrosis, CD11b+ cells were sorted from mammary glands of CD- and HFD-fed mice using magnetic beads. When cultured, a population of these sorted CD11b+ cells formed adherent colonies, and colony formation was significantly increased in the CD11b+ cells isolated from HFD-fed mice. When examined further, these colonies expressed myofibroblast markers smooth muscle actin (SMA) and collagen I. These colony-forming CD11b+ cells are consistent with fibrocytes, which have been studied in both chronic inflammatory and fibrotic diseases, but have not been studied in obesity. Fibrocytes are a multipotent, bone-marrow-derived population of cells that originate as myeloid progenitor cells and have characteristics of both macrophages and myofibroblasts. Consistent with an increase in fibrocytes in the mammary gland, myeloid progenitor cells (CD45+CD11b+CD34+) were significantly increased in the bone marrow of HFD-fed mice, indicating an upregulation in the progenitor cell population for both monocytes/macrophages and fibrocytes. To examine differentiation of fibrocytes within the mammary gland, FACS-isolated myeloid progenitor cells from the bone marrow of GFP positive mice were transplanted into the inguinal mammary glands of HFD-fed CCR2 null mice, which have limited movement of myeloid lineage cells out of the bone marrow. Within the mammary glands of these transplanted mice, we observed GFP positive cells that also expressed SMA. Together, our results suggest that chronic inflammation within the obese mammary gland leads to increased fibrocyte numbers, as well as increased collagen deposition around mammary ducts. The effects of obesity on breast tissue fibrosis, as well as the cells responsible for this fibrosis, must be elucidated to better address the risk of breast tumor development in obese women. Citation Format: Genevra M. Kuziel, Lisa M. Arendt. Identifying the role of fibrocytes in obesity-induced mammary gland fibrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 107.

Abstract 90: Fatty acid synthesis is required for breast cancer brain metastasis

Abstract Brain metastases are refractory to therapies that otherwise control systemic disease in patients with human epidermal growth factor receptor 2 (HER2+) breast cancer, and the unique brain microenvironment contributes to this therapy resistance. Nutrient availability can vary across tissues, therefore metabolic adaptations required for breast cancer growth in the brain microenvironment may also introduce liabilities that can be exploited for therapy. Here, we assessed how metabolism differs between breast tumors growing in the brain versus extracranial sites and found that fatty acid synthesis is elevated in breast tumors growing in the brain. We determine that this phenotype is an adaptation to decreased lipid availability in the brain relative to other tissues, which results in a site-specific dependency on fatty acid synthesis for breast tumors growing at this site. Genetic or pharmacological inhibition of fatty acid synthase (FASN) reduces HER2+ breast tumor growth in the brain, demonstrating that differences in nutrient availability across metastatic sites can result in targetable metabolic dependencies. Citation Format: Gino B. Ferraro, Ahmed Ali, Alba Luengo, David P. Kodack, Amy Deik, Keene L. Abbott, Divya Bezwada, Landry Blanc, Brendan Prideaux, Xin Jin, Jessica M. Possada, Jiang Chen, Christopher R. Chin, Zohreh Amoozgar, Raphael Ferreira, Ivy Chen, Kamila Naxerova, Christopher Ng, Anna M. Westermark, Mark Duquette, Sylvie Roberge, Costas A. Lyssiotis, Dan G. Duda, Todd R. Golub, Shawn M. Davidson, Dai Fukumura, Véronique A. Dartois, Clary B. Clish, Matthew G. Vander Heiden, Rakesh K. Jain. Fatty acid synthesis is required for breast cancer brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 90.

Abstract 2601: Using chaperonin containing TCP1 as a marker to track clinically relevant circulating tumor cells

Abstract Current methods for assessing circulating tumor cells (CTC) in blood focus on capture and enumeration with epithelial markers that provide little information about the aggressive and invasive potential of CTC. As a result, valuable knowledge that improves monitoring of cancer recurrence and metastasis is lacking. To provide actionable information on CTC, we developed a CTC identification method based on detection of the second subunit of Chaperonin Containing TCP1 (CCT2). CCT is a macromolecular protein folding complex composed of eight subunits (CCT1-8) that drives expression of many tumorigenic factors. Bioinformatic analysis in multiple cancers, such as breast cancer, revealed increased gene expression in tumor tissue compared to normal tissue for CCT1-8 (p< 0.0001), with the largest differences observed in CCT2 and CCT3. Genomic alteration of CCT2 inversely correlated with cancer patient survival, and depletion of CCT2 prevented growth of murine breast tumors. In a correlative study of blood and tumor tissues from metastatic breast cancer patients, high CTC counts positively correlated with detectable CCT2 in tumor tissues. These results support CCT2 as a possible marker for CTC. To determine this, antibodies to CCT2 were validated for use in the CellSearch System (CSS), currently the only FDA approved CTC enrichment platform, and tested with breast cancer cells spiked into healthy human blood. Recovery using CCT2 for identification, led to increased collection up to 6% of spiked breast cancer cells that would have been lost by standard CTC classification using cytokeratin (CK). With prognostic thresholds around 3-5 CTC/tube of blood, increased detection of even 1-2 more CTC can be significant for assessing patients' risks. Analysis in an open software program called ACCEPT (Automated CTC Classification, Enumeration and PhenoTyping) confirmed that the majority of recovered spiked cancer cells expressed CCT2. Flow cytometry analysis of spiked cancer cells confirmed that CCT2+ enriched cells expressed cancer markers CD44 or estrogen receptor (ER). These results show that the addition of CCT2 staining to a CTC detection protocol has positive implications for enumeration of CTC from blood, such as increased detection of CTC with low expression of epithelial markers. This experiment was repeated using small cell lung cancer cell lines with similar results. The combined bioinformatics, histologic and experimental results indicate that identification of CCT2-expressing CTC can be incorporated into CTC detection platforms to monitor those patients with a heightened risk for cancer recurrence or metastasis. Citation Format: Amanda Cox, Ana Martini, Eunkyung Lee, Rebecca Moroose, Amr Khaled, Annette R. Khaled. Using chaperonin containing TCP1 as a marker to track clinically relevant circulating tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2601.

Abstract 2690: Therapeutic browning of white adipose tissue in the tumor microenvironment to inhibit breast cancer progression

Abstract Background and Aim: The growth and metastatic potential of cancer cells is regulated by the surrounding tumor microenvironment composed of a variety of cells including endothelial cells, fibroblasts, and adipose cells that promote tumor cell growth and invasion. There are two types of adipose tissue within the body. Brown adipocytes (BAT) contains uncoupling protein 1 (UCP1), which burns energy through adaptive thermogenesis. White adipocytes (WAT), which is the most prominent cell type in the breast, stores energy in the form of lipids. White adipocytes have the ability to secrete cytokines, growth factors, and hormones, providing a suitable microenvironment for breast tumor growth and progression. Identifying the mechanism through which adipocytes promote breast tumor progression will allow for the development of novel therapeutic interventions to inhibit adipocyte-breast cancer cell crosstalk during early stages of breast carcinogenesis. Furthermore, development of treatments that target cells within the tumor microenvironment, such as adipose cells, will potentially inhibit primary tumor growth as well as prevent metastatic disease, and could provide a treatment option for breast cancers. Methods: Functional assays including matrigel invasion, transwell migration and growth assays were conducted. Browning of white adipocyte was achieved by the addition of bioactive compounds such as BITC and Honokiol. Results: First, we explored the functional impact of WAT on breast cancer cells and observed that co-culture of WAT and breast cancer cells significantly increases the growth, clonogenicity, invasion and migration potential of breast cancer cells. In addition, breast cancer cells with epithelial-like morphology exhibit an acquisition of mesenchymal-like morphology indicating epithelial-to-mesenchymal conversion. To query the existence of a crosstalk between breast cancer cells and WAT, we examined the secretome of WATs and WATs-co-cultured with breast cancer cells (termed CA-WAT). We observed that CA-WAT exhibit increased levels of pro-inflammatory cytokines (IL-6, MCP, and PAI). Furthermore, we examined if WAT can be converted to BAT using bioactive strategies. We found that successful browning of WAT can be achieved with BITC and Honokiol. The addition of bioactive compounds increases the expression of BAT marker genes (UCP1, PRDM16, EVOL3, COX7a, and CIDEA) in WAT. We discovered that browning of WAT not only abrogates the pro-cancer effects of WAT on breast cancer cells but it also successfully alters the secretome profile of WAT. Conclusion: Our study shows that the conversion of white adipocytes to brown adipocytes with the use of BITC and Honokiol may serve as a novel therapeutic option for altering the breast tumor microenvironment to inhibit the growth and metastatic potential of breast cancer cells. Citation Format: Nethaji Muniraj, Sumit Siddharth, Sheetal Parida, Marey Shriver, Arumugam Nagalingam, Dipali Sharma. Therapeutic browning of white adipose tissue in the tumor microenvironment to inhibit breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2690.