Breast Cancer Metastasis Suppressor Research Articles

A commonly inherited human PCSK9 germline variant drives breast cancer metastasis via LRP1 receptor.

Identifying patients at risk for metastatic relapse is a critical medical need. We identified a common missense germline variant in proprotein convertase subtilisin/kexin type 9 (PCSK9) (rs562556, V474I) that is associated with reduced survival in multiple breast cancer patient cohorts. Genetic modeling of this gain-of-function single-nucleotide variant in mice revealed that it causally promotes breast cancer metastasis. Conversely, host PCSK9 deletion reduced metastatic colonization in multiple breast cancer models. Host PCSK9 promoted metastatic initiation events in lung and enhanced metastatic proliferative competence by targeting tumoral low-density lipoprotein receptor related protein 1 (LRP1) receptors, which repressed metastasis-promoting genes XAF1 and USP18. Antibody-mediated therapeutic inhibition of PCSK9 suppressed breast cancer metastasis in multiple models. In a large Swedish early-stage breast cancer cohort, rs562556 homozygotes had a 22% risk of distant metastatic relapse at 15 years, whereas non-homozygotes had a 2% risk. Our findings reveal that a commonly inherited genetic alteration governs breast cancer metastasis and predicts survival-uncovering a hereditary basis underlying breast cancer metastasis.

EHD1 promotes breast cancer metastasis through upregulating HIF2a expression via activating mTOR pathway.

The multistep dynamic process of metastasis is the primary cause of breast cancer deaths. C-terminal Eps15-homology domain-containing protein 1 (EHD1), a translocator associated with endocytic recycling, has been implicated in various oncogenic processes. However, the precise molecular mechanisms of EHD1-induced breast cancer metastases remain largely unexplored. Here we found that the upregulation of EHD1 in breast cancer was positively associated with distant lymph node metastasis in patients. Meanwhile, EHD1 promoted epithelial-mesenchymal transition (EMT), invasion, and metastasis of breast cancer cells in both two-dimensional (2D) and three-dimensional (3D) culture models invitro, as well as invivo. Remarkably, EHD1 can activate the AKT-mTOR pathway to upregulate the protein expression of hypoxia-inducible factor 2α (HIF2α) under normoxic conditions and subsequently enhance the invasive and metastatic breast cancer. Our findings indicated EHD1 as a new regulator of HIF2α and a potential therapeutic target for inhibiting breast cancer metastasis.

Unraveling the metastasis-preventing effect of miR-200c in vitro and in vivo.

Advanced breast cancer, as well as ineffective treatments leading to surviving cancer cells, can result in the dissemination of these malignant cells from the primary tumor to distant organs. Recent research has shown that microRNA 200c (miR-200c) can hamper certain steps of the invasion-metastasis cascade. However, it is still unclear whether miR-200c expression alone is sufficient to prevent breast cancer cells from metastasis formation. Hence, we performed a xenograft mouse experiment with inducible miR-200c expression in MDA-MB 231 cells. The ex vivo analysis of metastatic sites in a multitude of organs, including lung, liver, brain, and spleen, revealed a dramatically reduced metastatic burden in mice with miR-200c-expressing tumors. A fundamental prerequisite for metastasis formation is the motility of cancer cells and, therefore, their migration. Consequently, we analyzed the effect of miR-200c on collective- and single-cell migration in vitro, utilizing MDA-MB 231 and MCF7 cell systems with genetically modified miR-200c expression. Analysis of collective-cell migration revealed confluence-dependent motility of cells with altered miR-200c expression. Additionally, scratch assays showed an enhanced predisposition of miR-200c-negative cells to leave cell clusters. The in-between stage of collective- and single-cell migration was validated using transwell assays, which showed reduced migration of miR-200c-positive cells. Finally, to measure migration at the single-cell level, a novel assay on dumbbell-shaped micropatterns was performed, which revealed that miR-200c critically determines confined cell motility. All of these results demonstrate that sole expression of miR-200c impedes metastasis formation in vivo and migration in vitro and highlights miR-200c as a metastasis suppressor in breast cancer.

Lung-resident alveolar macrophages regulate the timing of breast cancer metastasis

Breast disseminated cancer cells (DCCs) can remain dormant in the lungs for extended periods, but the mechanisms limiting their expansion are not well understood. Research indicates that tissue-resident alveolar macrophages suppress breast cancer metastasis in lung alveoli by inducing dormancy. Through ligand-receptor mapping and intravital imaging, it was found that alveolar macrophages express transforming growth factor (TGF)-β2. This expression, along with persistent macrophage-cancer cell interactions via the TGF-βRIII receptor, maintains cancer cells in a dormant state. Depleting alveolar macrophages or losing the TGF-β2 receptor in cancer cells triggers metastatic awakening. Aggressive breast cancer cells are either suppressed by alveolar macrophages or evade this suppression by avoiding interaction and downregulating the TGF-β2 receptor. Restoring TGF-βRIII in aggressive cells reinstates TGF-β2-mediated macrophage growth suppression. Thus, alveolar macrophages act as a metastasis immune barrier, and downregulation of TGF-β2 signaling allows cancer cells to overcome macrophage-mediated growth suppression.

1α,25-Dihydroxyvitamin D Downregulates Adipocyte Impact on Breast Cancer Cell Migration and Adipokine Release.

Excess adiposity is associated with a higher risk of breast cancer metastasis and mortality. Evidence suggests that dietary vitamin D inhibits breast cancer metastasis. However, the mechanistic link between vitamin D's regulation of adipocyte metabolism and metastasis has not been previously investigated. Therefore, the purpose of these experiments was to examine the effect of the active form of vitamin D, 1α,25-dihydroxyvitamin D (1,25(OH)2D), on adipocyte release of bioactive compounds and whether the impact on adipocytes leads to inhibition of breast cancer cell migration, an important step of metastasis. Differentiated 3T3-L1 adipocytes were treated with 1,25(OH)2D for two days, followed by either harvesting the adipocytes or collecting adipocyte-conditioned media without 1,25(OH)2D. A transwell migration assay was conducted with vehicle- or 1,25(OH)2D-conditioned media. In order to explore the mechanism underlying effects on breast cancer metastatic capability, the mRNA expression of leptin, adiponectin, insulin-like growth factor (IGF-1), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) was measured in adipocytes following either vehicle or 1,25(OH)2D treatment. Conditioned media from 1,25(OH)2D-treated adipocytes inhibited the migration of metastatic MDA-MB-231 breast cancer cells compared to conditioned media from vehicle-treated adipocytes. Treatment of adipocytes with 1,25(OH)2D decreased mRNA expression of leptin, adiponectin, IGF-1, IL-6, and MCP-1. Consistent with mRNA expression, concentrations of leptin, adiponectin, IGF-1, and IL-6 in adipocyte-conditioned media were decreased with 1,25(OH)2D treatment, although MCP-1 remained unchanged. In summary, these results suggest that 1,25(OH)2D alters adipocyte secretions to prevent breast cancer metastasis.

BMP4-Induced Suppression of Breast Cancer Metastasis Is Associated with Inhibition of Cholesterol Biosynthesis.

We reported previously that in preclinical models, BMP4 is a potent inhibitor of breast cancer metastasis and that high BMP4 protein levels predict favourable patient outcomes. Here, we analysed a breast cancer xenograft with or without enforced expression of BMP4 to gain insight into the mechanisms by which BMP4 suppresses metastasis. Transcriptomic analysis of cancer cells recovered from primary tumours and phosphoproteomic analyses of cancer cells exposed to recombinant BMP4 revealed that BMP4 inhibits cholesterol biosynthesis, with many genes in this biosynthetic pathway being downregulated by BMP4. The treatment of mice bearing low-BMP4 xenografts with a cholesterol-lowering statin partially mimicked the anti-metastatic activity of BMP4. Analysis of a cohort of primary breast cancers revealed a reduced relapse rate for patients on statin therapy if their tumours exhibited low BMP4 levels. These findings indicate that BMP4 may represent a predictive biomarker for the benefit of additional statin therapy in breast cancer patients.

Versatile Thermo-Sensitive liposomes with HSP inhibition and Anti-Inflammation for synergistic Chemo-Photothermal to inhibit breast cancer metastasis

Photothermal therapy (PTT) is a prospective therapeutic method for breast cancer. However, excess inflammatory response induced by PTT may aggravate tumor metastasis. Meanwhile, the overexpressed heat shock proteins (HSPs) by cancer cells can protect them from hyperthermia during PTT. Therefore, to attenuate the PTT-induced inflammation and inhibit tumor metastasis, a folate receptor-targeted thermo-sensitive liposome (BI-FA-LP) co-loading Berberine (BBR) and Indocyanine green (ICG) was developed. BI-FA-LP utilized enhanced permeability and retention (EPR) effect and FA receptor-mediated endocytosis to selectively accumulate at tumor, reducing off-target toxicity during the treatment. After targeting to the tumor site, BBR and ICG were released from BI-FA-LP upon laser irradiation, and ICG showed good photothermal performance, while BBR inhibited HSP70 and HSP90 expression during PTT, exerting chemo-photothermal synergetic anti-tumor effect. Moreover, BBR could suppress the PTT induced inflammation, thus inhibiting tumor metastasis and ameliorating tissue injury. Thus, this versatile liposome provided a new strategy to enhance PTT and anti-inflammatory effects for breast cancer treatment.

Discovery of novel pyrazolo[1,5-a]pyrimidine derivatives as selective ROCK2 inhibitors with anti-breast cancer migration and invasion activities

Rho-associated coiled-coil kinase (ROCK) is involved in multiple cellular activities regulating the actin cytoskeleton, such as cell morphology, adhesion, and migration. The inhibition of ROCK is a feasible strategy to suppress breast cancer metastasis. Herein, based on Belumosudil, a series of pyrazolo[1,5-a]pyrimidine derivatives as selective ROCK2 inhibitors were designed and synthesized. Through systematic investigation of SARs, the piperazine analog 7u was identified with optimum ROCK2 inhibitory activity (IC50 = 36.8 nM) and excellent selectivity over the isoform protein ROCK1 (>250-fold). Intriguingly, upon treatment with 7u, the arrangement of the MDA-MB-231 cytoskeleton was affected accompanied by the alteration of morphology. Furthermore, cell scratch and transwell assays indicated that 7u inhibited MDA-MB-231 cell migration and invasion in a dose-dependent manner. Ultimately, the binding model of 7u with ROCK2 well accounted for the superior activities of 7u as a promising ROCK2 inhibitor with the potential application in breast cancer metastasis treatment.

The role of RRS1 in breast cancer cells metastasis and AEG-1/AKT/c-Myc signaling pathway.

Breast cancer is the most common malignant tumor in women. Recurrence, metastasis, and chemotherapy resistance are the main causes of death in breast cancer patients. The inhibition of breast cancer metastasis is of great significance for prolonging its survival. Ribosome biogenesis regulatory protein homolog (RRS1) is overexpressed in breast cancer tissues and is involved in regulating the carcinogenic process of breast cancer cells. However, the exact signaling pathway and molecular mechanism of RRS1 promoting breast cancer metastasis are not fully understood. Hence, the primary objective of our study is to investigate the correlation between RRS1 and breast cancer metastasis. Bioinformatic analysis was used to identify the expression levels and prognostic significance of RRS1 in breast cancer. Lenti-sh RRS1 lentivirus was constructed and employed to downregulate the RRS1 expression in MDA-MB-231 and BT549 cells, which had a high-level expression of RRS1. Subsequently, we assessed the impact of RRS1 downregulation on the proliferation, migration, and invasion of breast cancer cells using CCK-8, apoptosis, and cell cycle by flow cytometry, wound healing test, Transwell migration, and invasion experiments. Moreover, we utilized an in vivo imaging system to examine the metastatic potential of breast cancer cells after RRS1 knockdown. Picrate staining and hematoxylin-eosin staining were employed to evaluate the presence of metastatic lesions. To gain a deeper understanding of the molecular mechanism, we conducted co-immunoprecipitation and western blot. The significant overexpression of RRS1 in breast cancer indicates a worse prognosis, as determined through TCGA databases (p<0.01). Additionally, RRS1 exhibits upregulation in breast cancer (p<0.001), which is tightly linked to the occurrence of lymph node metastasis (p<0.001). Clinical breast cancer tissues and breast cancer cell lines also demonstrated a noteworthy upregulation of RRS1 (p<0.05). Loss-of-function experiment illustrated that the inhibiting of RRS1 expression reduced the rapid proliferation capacity of MDA-MB-231 and BT549 cells and hindered their migration and invasion capabilities (p<0.05). Importantly, the suppression of RRS1 significantly diminished lung metastasis in Balb/c nude mice that were injected with MDA-MB-231 cells (p<0.01). Mechanistically, RRS1 may interact with the AEG-1 to modulate the phosphorylation of AKT at T308 and S473, consequently impeding the activity of c-Myc (p<0.05). To conclude, RRS1 functions as a potential oncogene in breast cancer by leveraging the AEG-1/AKT/c-Myc signaling.

Retracted] Paclitaxel inhibits breast cancer metastasis via suppression of Aurora kinase‑mediated cofilin‑1 activity.

[This retracts the article DOI: 10.3892/etm.2017.5588.].

Biomimetic gold nanocages incorporating copper-human serum albumin for tumor immunotherapy via cuproptosis-lactate regulation

Cancer immunotherapy remains a significant challenge due to insufficient proliferation of immune cells and the sturdy immunosuppressive tumor microenvironment. Herein, we proposed the hypothesis of cuproptosis-lactate regulation to provoke cuproptosis and enhance anti-tumor immunity. For this purpose, copper-human serum albumin nanocomplex loaded gold nanocages with bacterial membrane coating (BAu-CuNCs) were developed. The targeted delivery and disassembly of BAu-CuNCs in tumor cells initiated a cascade of reactions. Under near infrared (NIR) laser irradiation, the release of copper-human serum albumin (Cu-HSA) was enhanced that reacted with intratumoral glutathione (GSH) via a disulfide exchange reaction to liberate Cu2+ ions and exert cuproptosis. Subsequently, the cuproptosis effect triggered immunogenic cell death (ICD) in tumor by the release of damage associated molecular patterns (DAMPs) to realize anti-tumor immunity via robust production of cytotoxic T cells (CD8+) and helper T cells (CD4+). Meanwhile, under NIR irradiation, gold nanocages (AuNCs) promoted excessive reactive oxygen species (ROS) generation that played a primary role in inhibiting glycolysis, reducing the lactate and ATP level. The combine action of lower lactate level, ATP reduction and GSH depletion further sensitized the tumor cells to cuproptosis. Also, the lower lactate production led to the significant blockage of immunosuppressive T regulatory cells (Tregs) and boosted the anti-tumor immunity. Additionally, the effective inhibition of breast cancer metastasis to the lungs enhanced the anti-tumor therapeutic impact of BAu-CuNCs + NIR treatment. Hence, BAu-CuNCs + NIR concurrently induced cuproptosis, ICD and hindered lactate production, leading to the inhibition of tumor growth, remodeling of the immunosuppressive tumor microenvironment and suppression of lung metastasis. Therefore, leveraging cuproptosis-lactate regulation, this approach presents a novel strategy for enhanced tumor immunotherapy.

Suppression of lysosome metabolism-meditated GARP/TGF-β1 complexes specifically depletes regulatory T cells to inhibit breast cancer metastasis.

Regulatory T cells (Tregs) prevent autoimmunity and contribute to cancer progression. They exert contact-dependent inhibition of immune cells through the production of active transforming growth factor-β1 (TGF-β1). However, the absence of a specific surface marker makes inhibiting the production of active TGF-β1 to specifically deplete human Tregs but not other cell types a challenge. TGF-β1 in an inactive form binds to Tregs membrane protein Glycoprotein A Repetitions Predominant (GARP) and then activates it via an unknown mechanism. Here, we demonstrated that tumour necrosis factor receptor-associated factor 3 interacting protein 3 (TRAF3IP3) in the Treg lysosome is involved in this activation mechanism. Using a novel naphthalenelactam-platinum-based anticancer drug (NPt), we developed a new synergistic effect by suppressing ATP-binding cassette subfamily B member 9 (ABCB9) and TRAF3IP3-mediated divergent lysosomal metabolic programs in tumors and human Tregs to block the production of active GARP/TGF-β1 for remodeling the tumor microenvironment. Mechanistically, NPt is stored in Treg lysosome to inhibit TRAF3IP3-meditated GARP/TGF-β1 complex activation to specifically deplete Tregs. In addition, by promoting the expression of ABCB9 in lysosome membrane, NPt inhibits SARA/p-SMAD2/3 through CHRD-induced TGF-β1 signaling pathway. In addition to expose a previously undefined divergent lysosomal metabolic program-meditated GARP/TGF-β1 complex blockade by exploring the inherent metabolic plasticity, NPt may serve as a therapeutic tool to boost unrecognized Treg-based immune responses to infection or cancer via a mechanism distinct from traditional platinum drugs and currently available immune-modulatory antibodies.

Synergistic Effect of Layered Double Hydroxides Nanodosage Form to Induce Apoptosis and Ferroptosis in Breast Cancer.

Breast cancer is the most common cancer in women and one of the leading causes of cancer death worldwide. Ferroptosis, a promising mechanism of killing cancer cells, has become a research hotspot in cancer therapy. Simvastatin (SIM), as a potential new anti-breast cancer drug, has been shown to cause ferroptosis of cancer cells and inhibit breast cancer metastasis and recurrence. The purpose of this study is to develop a novel strategy boosting ferroptotic cascade for synergistic cancer therapy. In this paper, iron base form of layered double hydroxide supported simvastatin (LDHs-SIM) was synthesized by hydrothermal co-precipitation method. The characterization of LDHs-SIM were assessed by various analytical techniques, including ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). Biological activity, ferroptosis mechanism and biocompatibility were analyzed through in vivo and in vitro analysis, so as to evaluate its therapeutic effect on breast cancer. The constructed LDHs-SIM nanosystem can not only release SIM through mevalonate (MVA) pathway, inhibit the expression of glutathione peroxidase 4 (GPX4), inhibit the expression of SLC7A11 and reduce the synthesis efficiency of GSH, but also promote the accumulation of Fe2+ in cells through the release of Fe3+, and increase the intracellular ROS content. In addition, LDHs-SIM nanosystem can induce apoptosis of breast cancer cells to a certain extent, and achieve the synergistic effect of apoptosis and ferroptosis. In the present study, we demonstrated that nanoparticles of layered double hydroxides (LDHs) loaded with simvastatin were more effective than a free drug at inhibiting breast cancer cell growth, In addition, superior anticancer therapeutic effects were achieved with little systemic toxicity, indicating that LDHs-SIM could serve as a safe and high-performance platform for ferroptosis-apoptosis combined anticancer therapy.

Mixtures of Doxorubicin-Loaded Micelles and Berberine and Mifepristone Co-Loaded Liposomes Inhibit Breast Cancer Metastasis Based on Regulation of Tumor Microenvironments

Mixtures of Doxorubicin-Loaded Micelles and Berberine and Mifepristone Co-Loaded Liposomes Inhibit Breast Cancer Metastasis Based on Regulation of Tumor Microenvironments

Loss of tumor-derived SMAD4 enhances primary tumor growth but not metastasis following BMP4 signalling

BackgroundBone morphogenetic protein 4 (BMP4) is a potent inhibitor of breast cancer metastasis. However, a tumor-promoting effect of BMP4 is reported in other tumor types, especially when SMAD4 is inactive.MethodsTo assess the requirement for SMAD4 in BMP4-mediated suppression of metastasis, we knocked down SMAD4 in two different breast tumors and enforced SMAD4 expression in a third line with endogenous SMAD4 deletion. In addition, we assessed the requirement for SMAD4 in tumor cell-specific BMP signalling by expression of a constitutively active BMP receptor. Delineation of genes regulated by BMP4 in the presence or absence of SMAD4 was assessed by RNA sequencing and a BMP4-induced gene, MYO1F was assessed for its role in metastasis. Genes regulated by BMP4 and/or SMAD4 were assessed in a publicly available database of gene expression profiles of breast cancer patients.ResultsIn the absence of SMAD4, BMP4 promotes primary tumor growth that is accompanied by increased expression of genes associated with DNA replication, cell cycle, and MYC signalling pathways. Despite increased primary tumor growth, BMP4 suppresses metastasis in the absence of tumor cell expression of SMAD4. Consistent with the anti-metastatic activity of BMP4, enforced signalling through the constitutively active receptor in SMAD4 positive tumors that lacked BMP4 expression still suppressed metastasis, but in the absence of SMAD4, the suppression of metastasis was largely prevented. Thus BMP4 is required for suppression of metastasis regardless of tumor SMAD4 status. The BMP4 upregulated gene, MYO1F, was shown to be a potent suppressor of breast cancer metastasis. Gene signature upregulated by BMP4 in the absence of SMAD4 was associated with poor prognosis in breast cancer patients, whereas gene signature upregulated by BMP4 in the presence of SMAD4 was associated with improved prognosis.ConclusionsBMP4 expression is required for suppression of metastasis regardless of the SMAD4 status of the tumor cells. Since BMP4 is a secreted protein, we conclude that it can act both in an autocrine manner in SMAD4-expressing tumor cells and in a paracrine manner on stromal cells to suppress metastasis. Deletion of SMAD4 from tumor cells does not prevent BMP4 from suppressing metastasis via a paracrine mechanism.

Taurine Inhibits Lung Metastasis in Triple-Negative Breast Cancer by Modulating Macrophage Polarization Through PTEN-PI3K/Akt/mTOR Pathway.

Taurine (Tau) has been found to inhibit triple-negative breast cancer (TNBC) invasion and metastasis. However, its effect on tumor-promoting macrophages and tumor suppressor macrophages in breast cancer progression remains unknown. In this study, we investigated the effects of Tau on macrophage polarization and its role in TNBC cell growth, invasion, and metastasis. We induced human THP-1 monocytes to differentiate into M2 macrophages through exogenous addition of interleukin-4. We used the TNBC cell lines MDA-MB-231 and BT-549 cultured in a conditioned medium from M2 macrophages to investigate the effect of Tau on tumor growth and invasion. We analyzed macrophage subset distribution, M1 and M2 macrophage-associated markers, and mRNA expression by quantitative polymerase chain reaction. We also detected the PTEN-PI3K/Akt/mTOR signaling pathway that mediates M1 macrophage to suppress tumor invasion using western blotting. Our results showed that Tau inhibits breast cancer metastasis to the lungs in vivo and cell invasion by altering the polarization of tumor-associated macrophage in vitro. In addition, Tau can up-regulate PTEN expression, suppress the PI3K-Akt signaling pathway, and promote the M1 polarization of macrophages, which ultimately inhibits the metastasis of TNBC cells. Our findings suggest that Tau inhibits the activation of the PI3K-Akt-mTOR signaling pathway by up-regulating PTEN , promotes the proportion of M1 macrophages in tumor-associated macrophage, and suppresses the invasion and metastasis of TNBC. This provides a potential therapeutic approach to influence cancer progression and metastasis.

Synthetic Peptides with Genetic‐Codon‐Tailored Affinity for Assembling Tetraspanin CD81 at Cell Interfaces and Inhibiting Cancer Metastasis

AbstractProbing biomolecular interactions at cellular interfaces is crucial for understanding and interfering with life processes. Although affinity binders with site specificity for membrane proteins are unparalleled molecular tools, a high demand remains for novel multi‐functional ligands. In this study, a synthetic peptide (APQQ) with tight and specific binding to the untargeted extracellular loop of CD81 evolved from a genetically encoded peptide pool. With tailored affinity, APQQ flexibly accesses, site‐specifically binds, and forms a complex with CD81, enabling in‐situ tracking of the dynamics and activity of this protein in living cells, which has rarely been explored because of the lack of ligands. Furthermore, APQQ triggers the relocalization of CD81 from diffuse to densely clustered at cell junctions and modulates the interplay of membrane proteins at cellular interfaces. Motivated by these, efficient suppression of cancer cell migration, and inhibition of breast cancer metastasis were achieved in vivo.

Synthetic Peptides with Genetic-Codon-Tailored Affinity for Assembling Tetraspanin CD81 at Cell Interfaces and Inhibiting Cancer Metastasis.

Probing biomolecular interactions at cellular interfaces is crucial for understanding and interfering with life processes. Although affinity binders with site specificity for membrane proteins are unparalleled molecular tools, a high demand remains for novel multi-functional ligands. In this study, a synthetic peptide (APQQ) with tight and specific binding to the untargeted extracellular loop of CD81 evolved from a genetically encoded peptide pool. With tailored affinity, APQQ flexibly accesses, site-specifically binds, and forms a complex with CD81, enabling in-situ tracking of the dynamics and activity of this protein in living cells, which has rarely been explored because of the lack of ligands. Furthermore, APQQ triggers the relocalization of CD81 from diffuse to densely clustered at cell junctions and modulates the interplay of membrane proteins at cellular interfaces. Motivated by these, efficient suppression of cancer cell migration, and inhibition of breast cancer metastasis were achieved in vivo.

Exercise affects high-fat diet-stimulated breast cancer metastasis through irisin secretion by altering cancer stem cell properties

BackgroundRegular physical activities reduce the growth of breast cancer, but research on the effects of steady exercise on metastasis and its mechanisms is limited. In this study, the effects of steady exercise on breast cancer metastasis and its possible mechanism were demonstrated. MethodsExperimental metastasis was induced after 8 weeks of steady exercise using a mouse model. Furthermore, one of the myokines, irisin, was studied to elucidate the effects of metastasis-regulating protein expression, and colony and sphere formation, which are cancer stem cell properties. ResultsLow- and moderate-intensity exercise significantly reduced the number and volume of metastasized tumors. Among myokines, only irisin was significantly increased by steady exercise but decreased by a high-fat diet. In vitro studies, irisin significantly decreased the number of colonies and sphere formation. Irisin also inhibited cell migration and invasion and suppressed the malignancy of breast cancer cells by reducing the expression of vimentin, MMP-2, MMP-9, and HIF-1 and by increasing the expression of TIMP-1 and TIMP-2. ConclusionSteady exercise modulates myokine secretions and among them, irisin suppresses breast cancer metastasis by decreasing self-renewal properties and invasion regulating protein expressions. Thus, regular exercise may be beneficial in the prevention of breast tumor metastasis.

Abstract B072: Loss of the tumor and metastasis suppressor RasGAP DAB2IP mediates therapeutic resistance in HER2+ breast cancer

Abstract Resistance to HER2 inhibitors remains a clinical challenge in HER2+ breast cancer. Therefore, there is an urgent need to 1) understand the mechanisms that underlie resistance to these current treatments and 2) develop improved, and more importantly, curative combination therapies. We previously showed that the RasGAP DAB2IP is a tumor and metastasis suppressor in breast cancer. Interestingly, we have now generated robust data demonstrating that the loss of DAB2IP also mediates therapeutic resistance in HER2+ breast cancer. First, we genetically ablated DAB2IP in multiple HER2+ breast cancer cell lines and performed manual counting experiments after 6 days of HER2 TKI treatment. In all cell lines, DAB2IP knockdown conferred resistance to HER2 inhibitors. Since HER2 inhibitors are known to induce both apoptosis and senescence, we next investigated how DAB2IP loss specifically affects these phenotypes. Interestingly, DAB2IP knockdown prevented TKI-induced caspase-3/7 activation, measured by Incucyte live cell imaging, and enabled the regrowth of cells in long-term 10-day treatment and drug washout experiments, monitored by Incucyte or crystal violet staining. Mechanistically, stable knockdown of DAB2IP reduced the suppression of the AKT and ERK pathways and the induction of the pro-apoptotic protein Bim upon HER2i treatment. In addition, cell cycle progression pathways were enriched in DAB2IP-deficient cells on lapatinib treatment and immunoblots revealed higher residual levels of pRb and low levels of p27 in these cells. Interestingly, the levels of these proteins were restored and regrowth in low density assays was inhibited with co-treatment with an NF-kB inhibitor. We next evaluated the relevance of DAB2IP loss in mediating HER2 inhibitor resistance in a SUM190 orthotopic xenograft model. Importantly, while control tumors regressed upon lapatinib treatment, DAB2IP-deficient tumors did not regress and grew with kinetics comparable to vehicle-treated tumors after few days on treatment. Further understanding the pathways deregulated by DAB2IP loss upon HER2i treatment will be essential for developing effective therapeutic strategies to combat resistance induced by DAB2IP loss. Citation Format: Naiara Perurena, Amy Schade, Natalie Pilla, Patrick Loi, Carrie Rodriguez, Alycia Gardner, Karen Cichowski. Loss of the tumor and metastasis suppressor RasGAP DAB2IP mediates therapeutic resistance in HER2+ breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B072.