Triple-negative Breast Cancer Cells Cells Research Articles

G-quadruplex structural dynamics at MAPK12 promoter dictates transcriptional switch to determine stemness in breast cancer.

P38γ (MAPK12) is predominantly expressed in triple negative breast cancer cells (TNBC) and induces stem cell (CSC) expansion resulting in decreased survival of the patients due to metastasis. Abundance of G-rich sequences at MAPK12 promoter implied the functional probability to reverse tumorigenesis, though the formation of G-Quadruplex (G4) structures at MAPK12 promoter is elusive. Here, we identified two evolutionary consensus adjacent G4 motifs upstream of the MAPK12 promoter, forming parallel G4 structures. They exist in an equilibria between G4 and duplex, regulated by the binding turnover of Sp1 and Nucleolin that bind to these G4 motifs and regulate MAPK12 transcriptional homeostasis. To underscore the gene-regulatory functions of G4 motifs, we employed CRISPR-Cas9 system to eliminate G4s from TNBC cells and synthesized a naphthalene diimide (NDI) derivative (TGS24) which shows high-affinity binding to MAPK12-G4 and inhibits MAPK12 transcription. Deletion of G4 motifs and NDI compound interfere with the recruitment of the transcription factors, inhibiting MAPK12 expression in cancer cells. The molecular basis of NDI-induced G4 transcriptional regulation was analysed by RNA-seq analyses, which revealed that MAPK12-G4 inhibits oncogenic RAS transformation and trans-activation of NANOG. MAPK12-G4 also reduces CD44High/CD24Low population in TNBC cells and downregulates internal stem cell markers, arresting the stemness properties of cancer cells.

Vanadium complex as a potential modulator of the autophagic mechanism through proteins PI3K and ULK1: development, validation and biological implications of a specific force field for [VO(bpy)2Cl

The modulation of autophagy has been presented as a very useful strategy in anticancer treatments. In this sense, the vanadium complex (VC) bis(2,2'-bipyridine)chlorooxovanadium(IV), [VO(bpy)2Cl], is known for its ability to induce autophagy in triple-negative breast cancer cells (TNBC). An excellent resource to investigate the role of VC in the induction of autophagy is to make use of Molecular Dynamics (MD) simulations. However, until now, the scarcity of force field parameters for the VC prevented a reliable analysis. The autophagy signaling pathway starts with the PI3K protein and ends with ULK1. Therefore, in the first stage of this work, we developed a new AMBER force field for the VC (VCFF) from a quantum structure, obtained by DFT calculations. In the second stage, the VCFF was validated through structural analyses. From this, it was possible to investigate, through docking and MD (200 ns), the performance of the PI3K-VC and ULK1-VC systems (third stage). The analyses of this last stage involved RMSD, hydrogen bonds, RMSF and two pathways for the modulation of autophagy. In general, this work fills in the absence of force field parameters (FF) for VC by proposing an efficient and new FF, in addition to investigating, at the molecular level, how VC is able to induce autophagy in TNBC cells. This study encourages new parameterizations of metallic complexes and contributes to the understanding of the duality of autophagic processes.Communicated by Ramaswamy H. Sarma.

ZHX2 deficiency enriches hybrid MET cells through regulating E-cadherin expression

Growing evidence indicates that the epithelial to mesenchymal (E/M) hybrid state plays a key role in tumorigenesis. Importantly, a hybrid mesenchymal to epithelial transition (MET) state in which individual cells express both epithelial and mesenchymal markers was recently identified in vivo, further strengthening the bonds between the hybrid EMT state and cancer progression. However, the role and the molecular mechanisms by which the hybrid MET state is maintained in triple-negative breast cancer cells (TNBC) remain elusive. Here, we find that loss of ZHX2 expression results in the hybrid MET phenotype in mesenchymal TNBC cells. Mechanistically, through directly binding to the CDH1 promoter, depletion of ZHX2 specifically reactivates expression of CDH1 encoding E-cadherin, an epithelial marker that is crucial for maintaining epithelial phenotype. Functionally, loss of ZHX2 expression enriches the hybrid MET cells and inhibits the migration and dissemination of TNBC cells or organoids, which could be reversed by restoration of E-cadherin. Moreover, depletion of ZHX2 suppresses lung metastasis in preclinical models of TNBC. In patients with TNBC, ZHX2 expression was amplified and negatively correlated with the expression of E-cadherin. These findings suggest that loss of ZHX2 promotes the hybrid MET state to impair TNBC progression.

Anthocyanins Reduce Cell Invasion and Migration through Akt/mTOR Downregulation and Apoptosis Activation in Triple-Negative Breast Cancer Cells: A Systematic Review and Meta-Analysis.

Studies have suggested the chemopreventive effects of anthocyanins on breast cancer carcinogenesis. This systematic review and meta-analysis aimed to evaluate the effect of anthocyanins on triple-negative breast cancer cells (TNBC) cultured in vitro. We searched for all relevant studies that evaluated the mechanisms of migration, invasion, Akt/mTOR and MAPK pathways, and apoptosis, using PubMed and Scopus. Means and standard deviation were used, and a randomized effects model was applied, with a confidence interval of 95%. Statistical heterogeneity between studies was assessed using the Chi2 test and I2 statistics. All analyses were performed using RevMan software (version 5.4). Eleven studies were included in the systematic review and ten in the meta-analysis, where the roles of anthocyanin-enriched extract or cyanidin-3-O-glucoside (C-3-O-G) on MDA-MB-231 and MDA-MB-453 cells were investigated. There was a significant reduction in invasion (mean difference: -98.64; 95% CI: -153.98, -43.3; p ˂ 0.00001) and migration (mean difference: -90.13; 95% CI: -130.57, -49.68; p ˂ 0.00001) in TNBC cells after anthocyanins treatment. Anthocyanins also downregulated Akt (mean difference: -0.63; 95% CI: -0.70, -0.57; p ˂ 0.00001) and mTOR (mean difference: -0.93; 95% CI: -1.58, -0.29; p = 0.005), while JNK (mean difference: -0.06; 95% CI: -1.21, 1.09; p = 0.92) and p38 (mean difference: 0.05; 95% CI: -1.32, 1.41; p = 0.95) were not modulated. There was also an increase in cleaved caspase-3 (mean difference: 1.13; 95% CI: 0.11, 2.16; p = 0.03), cleaved caspase-8 (mean difference: 1.64; 95% CI: 0.05, 3.22; p = 0.04), and cleaved PARP (mean difference: 0.93; 95% CI: 0.54, 1.32). Although the difference between control and anthocyanin groups was not significant regarding apoptosis rate (mean difference: 3.63; 95% CI: -2.88, 10.14; p = 0.27), the analysis between subgroups showed that anthocyanins are more favorable in inducing overall apoptosis (p ˂ 0.00001). The results show that anthocyanins hold promise in fighting against TNBC, but their effects should not be generalized. In addition, further primary studies should be conducted so that more accurate conclusions can be drawn.

Abstract 2539: Tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces cytokine release via the alternative NFKB2 pathway in triple negative breast cancer cells (TNBC) and modulates neutrophil chemotaxis

Abstract TRAIL induces apoptosis in many preclinical cancer models including breast cancers and has been extensively studied as a potential cancer therapeutic. However, its efficacy in clinical trials is limited, suggesting that there are unknown modulatory mechanisms responsible for its lack of TRAIL activity in vivo. We hypothesized that TRAIL treatment elicits transcriptional changes in TNBC cells that alter the immune milieu, modulating the therapeutic efficacy. To investigate the hypothesis, we performed RNAseq analysis of MDA-MB231 cells treated with TRAIL for different time points, followed by validation with RT-PCR in various TNBC cells. TRAIL treatment of the TNBC significantly induced expression of a number of cytokines, such as CXCL1, CXCL2, CXCL3, CXCL8, CXCL11, IL6, which are known to affect neutrophil function. Mechanistically, induction of these cytokines was predominantly mediated by Death Receptor 5 and Caspase-8 protein, but not Caspase-8 enzymatic activity. Gene Set Enrichment Analysis of the RNAseq indicated that NFKB pathway-mediated TNF-alpha signaling was significantly enriched. Concordantly, we confirmed that both canonical NFKB1 and non-canonical NFKB2 pathways were activated by TRAIL. However, siRNA knockdown experiments indicated that the induction of the cytokine mRNAs was primarily dependent on the NFKB2 pathway. Neutrophils isolated from healthy human donors incubated with supernatants from TNBC cells in vitro indicated that TRAIL-induced CXCLs’ (1, 2, 3, 8) and IL6 significantly increased neutrophil chemotaxis in a NFKB2-dependent manner. Moreover, neutrophils pre-incubated with supernatants from TRAIL-treated TNBC significantly inhibited its cytotoxic effect in TNBCs in a NFKB2-dependent pathway. Further RNAseq and RT-PCR of neutrophils incubated with by either TRAIL or supernatant of MDA-MB231 cells treated with TRAIL revealed significant enrichment of inflammatory pathway-related genes as well as increased expression of immune modulating cytokines. These results suggested that TRAIL exerts a pro-inflammatory role towards immune cells in tumor microenvironment. CODEX (CO-Detection by indEXing) analysis of in vivo TNBC xenografts from mice treated with the TRAIL agonist MEDI3039 confirmed that TRAIL treatment increases the number of neutrophils in the tumor. Using TNBC organoids and humanized mice models, the changes in tumor immune environment caused by TRAIL are currently under investigation. Collectively, our study suggests the novel role of TRAIL-induced NFKB2-dependent cytokine production that affects neutrophil functions, leading to modulation of the immune response in TNBC. Citation Format: Manjari Kundu, Yoshimi Endo Greer, Lisa A. Ridnour, David A. Wink, Stan Lipkowitz. Tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces cytokine release via the alternative NFKB2 pathway in triple negative breast cancer cells (TNBC) and modulates neutrophil chemotaxis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2539.

Potential use of bio functionalized nanoparticles to attenuate triple negative breast cancer (MDA-MB-231 cells).

This study showed that bio-functional silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) were synthesized in aqueous extracts of Gymnemasylvestre leaves and tested for toxicity assessment against triple-negative breast cancer cells (TNBC). Biofunctional nanoparticle (NPs) samples were characterized using UV-Vis spectroscopy, FT-IR, XRD, SEM, and TEM. The results showed that the phytofabrication of AgNPs resulted in a dark brown, UV-vis maximum absorbance peak at 413nm. The AgNPs were crystalline and spherical, with sizes ranging from 20 to 60nm, as confirmed by the XRD pattern and TEM images. Another phytofabrication of ZnONPs exhibited a white precipitate corresponding to a UV-Vis maximum absorption peak at 377nm and a fine micro flower morphology with a particle-sized tribution between 100 and 200nm. In addition, FT-IR spectra showed that bioorganic compounds are associated with NPs that respond to reduced Ag+ ions and AgNPs tabilizers.Invitro cytotoxicity studies revealed thepotent anti-cancer effects ofphytofabricated AgNPs and ZnONPs on TNBC cells.Furthermore, the AO/EB double staining assay results proved that apoptotic cells are distinguished by greenish-yellow fluorescence of the cell nuclei with IC50 concentrations of 44 ± 0.8µg/mL for AgNPs and 26.2 ± 0.5µg/mL for ZnONPs, respectively. Based on our results, we expect that the anticancer function of the biofunctional NPs is due to the apoptotic activation of TNBC cells by increased ROS.Therefore, the presented study demonstrated that biofunctional AgNPs and ZnONPs have excellent prospects for the anti-cancer activity that can be used in pharmaceutical and medical fields.

The anti-tumor activities of coenzyme Q0 through ROS-mediated autophagic cell death in human triple-negative breast cells

Coenzyme Q0 (CoQ0) obtained from Antrodia camphorata has therapeutic benefits in cancer treatment. Our previous findings in vivo and in vitro have shown that CoQ0 affects triple-negative breast cancer cells (TNBCs) by blocking EMT and metastasis. The current study investigated the cancer-preventive activities of CoQ0 on TNBC MDA-MB-468 and 231 cells by activating apoptotic and autophagic cell death. The CoQ0 treatment reduced colony development and proliferation in TNBC cells. In addition, CoQ0 triggered death activation by caspase-3 stimulation, PARP cleavage, and significantly affected Bax/Bcl-2 regulation. Autophagy was triggered by CoQ0, as shown by LC3-II accumulation, p62/SQSTM1 expression, ATG5 expression, ATG4B inhibition, AVO formation, and impeded Beclin-1/Bcl-2 regulation. In addition, transmission electron microscopy data showed that CoQ0 increased autophagosome formation. The antioxidant N-acetylcysteine substantially suppressed CoQ0-mediated ROS generation and attenuated apoptotic- and autophagic-cell death by CoQ0 in TNBC cells. CoQ0 is a potential anticancer agent in treating human triple-negative breast cancers.

DTMP imbalance through thymidylate 5′-phosphohydrolase activity induces apoptosis in triple-negative breast cancers

Immunotherapy has a number of advantages over traditional anti-tumor therapy but can cause severe adverse reactions due to an overactive immune system. In contrast, a novel metabolic treatment approach can induce metabolic vulnerability through multiple cancer cell targets. Here, we show a therapeutic effect by inducing nucleotide imbalance and apoptosis in triple negative breast cancer cells (TNBC), by treating with cytosolic thymidylate 5'-phosphohydrolase (CT). We show that a sustained consumption of dTMP by CT could induce dNTP imbalance, leading to apoptosis as tricarboxylic acid cycle intermediates were depleted to mitigate this imbalance. These cytotoxic effects appeared to be different, depending on substrate specificity of the 5′ nucleotide or metabolic dependency of the cancer cell lines. Using representative TNBC cell lines, we reveal how the TNBC cells were affected by CT-transfection through extracellular acidification rate (ECAR)/oxygen consumption rate (OCR) analysis and differential transcription/expression levels. We suggest a novel approach for treating refractory TNBC by an mRNA drug that can exploit metabolic dependencies to exacerbate cell metabolic vulnerability.

Multi-Level Control of the ATM/ATR-CHK1 Axis by the Transcription Factor E4F1 in Triple-Negative Breast Cancer.

E4F1 is essential for early embryonic mouse development and for controlling the balance between proliferation and survival of actively dividing cells. We previously reported that E4F1 is essential for the survival of murine p53-deficient cancer cells by controlling the expression of genes involved in mitochondria functions and metabolism, and in cell-cycle checkpoints, including CHEK1, a major component of the DNA damage and replication stress responses. Here, combining ChIP-Seq and RNA-Seq approaches, we identified the transcriptional program directly controlled by E4F1 in Human Triple-Negative Breast Cancer cells (TNBC). E4F1 binds and regulates a limited list of direct target genes (57 genes) in these cells, including the human CHEK1 gene and, surprisingly, also two other genes encoding post-transcriptional regulators of the ATM/ATR-CHK1 axis, namely, the TTT complex component TTI2 and the phosphatase PPP5C, that are essential for the folding and stability, and the signaling of ATM/ATR kinases, respectively. Importantly, E4F1 also binds the promoter of these genes in vivo in Primary Derived Xenograft (PDX) of human TNBC. Consequently, the protein levels and signaling of CHK1 but also of ATM/ATR kinases are strongly downregulated in E4F1-depleted TNBC cells resulting in a deficiency of the DNA damage and replicative stress response in these cells. The E4F1-depleted cells fail to arrest into S-phase upon treatment with the replication-stalling agent Gemcitabine, and are highly sensitized to this drug, as well as to other DNA-damaging agents, such as Cisplatin. Altogether, our data indicate that in breast cancer cells the ATM/ATR-CHK1 signaling pathway and DNA damage-stress response are tightly controlled at the transcriptional and post-transcriptional level by E4F1.

Regulation of p53 and survivin by Curcuma longa extract to caspase-3 dependent apoptosis in triple negative breast cancer cells.

Aim Triple negative breast cancer cells (TNBC) are the population of breast cancer cells that are responsible for cancer recurrence and apoptosis resistance. Unfortunately, current therapies have limited efficacy to TNBC population due to apoptosis resistance and chemoresistance. Tumour suppressor p53 and survivin are primary targets for TNBC therapy. Consequently, a search for a natural compound which targets p53 and survivin is needed to further advance TNBC treatment. Curcuma longa extract (CL), a natural compound induces apoptosis in several cancer cells by targeting various molecules and possess fewer side effects. However, a possible potential of CL as p53- and survivin modulating agent in TNBC cells has not been investigated. Methods MDAMB-231 cells were treated with several concentration of CL, after which, viability, p53 gene expression, surviving protein expression, and caspase-3 protein expression were evaluated. Results After 24-h treatment, CL possessed cytotoxic effect with IC50 value of 13 μg/mL. Treatment with 1.625, 3.25, 6.5, and 13 μg/mL of CL resulted in 2.70-25.80% increase in caspase-3 expression levels followed by 94.60 - 21.60% decrease in survivin protein levels. CL induced remarkably p53 gene expression ratio up to 5-fold at 13 μg/mL. Survivin protein levels were inversely proportional to p53 accumulation levels. Low survivin protein levels combined with high levels of p53 accumulation were correlated to higher apoptotic rates. Conclusion p53 and survivin as molecular targets of CL contribute to caspase-3-dependent apoptosis in TNBC cells and this compound represents an attractive p53- and survivin modulating agent in TNBC.

Abstract 6097: Ferroptosis resistance in epithelial populations of triple negative breast cancer is mediated by laminin 332 and integrin beta4

Abstract Ferroptosis is an iron dependent form of regulatory cell death caused by the accumulation of lipid peroxides that can be exploited as a therapeutic for carcinomas and possibly other cancers. However, some populations of carcinoma cells resist ferroptosis, especially those with an epithelial phenotype but the mechanisms that promote resistance are poorly understood. We discovered that ferroptosis resistance in triple-negative breast cancer cells (TNBC) with an epithelial phenotype is dependent on expression of the integrin β4 and its ligand laminin 332 (LM332). LM332 and the integrin β4 maintain an epithelial cell state by downregulation of the EMT factor ZEB1. We further demonstrate that repression of ZEB1 by integrin β4 and LM332 promotes YAP/TAZ-mediated transcription of the C2 subunit of LM332, activating a positive feedback loop. Lastly, we observed that disrupting the β4/LM332 signaling axis sensitizes epithelial TNBC cells to ferroptosis by inducing ZEB1 expression. Our findings reveal a novel role for the extracellular matrix in promoting ferroptosis resistance by sustaining an epithelial phenotype and they suggest potential therapeutic strategies for overcoming this resistance. Citation Format: Emmet R. Karner, Hira Lal Goel, Arthur M. Mercurio. Ferroptosis resistance in epithelial populations of triple negative breast cancer is mediated by laminin 332 and integrin beta4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6097.

10]-Gingerol-Loaded Nanoemulsion and its Biological Effects on Triple-Negative Breast Cancer Cells.

The apoptotic, cytotoxic, and cytostatic activities for [10]-gingerol in triple-negative breast cancer cells (TNBCs) were already reported. However, despite these important antitumor activities, the compound has the disadvantage to have a hydrophobic characteristic, hindering in vivo administration. To surpass this issue, in this study we have created a [10]-gingerol-loaded nanoemulsion (10GNE) in order to increase the stability and solubility of the compound. The nanoemulsion was characterized and tested for its cytotoxic, cytostatic, and apoptotic effects on a panel of murine and human TNBC cell lines, as well as non-tumor cells, and compared with a [10]-gingerol-free nanoemulsion (NE) and with [10]-gingerol itself. Except for the murine 4T1.13 cell line, the IC50 of the free 10G molecule, after 72 h of incubation, was higher in all cell lines tested, both murine and human, demonstrating therefore the efficacy of the 10GNE regarding cytotoxicity. In murine tumor cells, 60 μM 10GNE was able to arrest cell cycle at sub-G0 phase and induce apoptosis, leading to 48% and 78% of total cell death in 4T1.13 and 4T1Br4 murine tumor cells, respectively. This represents an improvement compared to 10G-free molecule that only induced 74% of total apoptosis at 100 μM in 4T1Br4 cells. Taken together, our results show that nanoformulation preserved the [10]-gingerol cytotoxic and cytostatic properties and improved its apoptotic function on murine TNBC cell lines. These data open new perspectives to a more suitable drug-delivery approach for [10]-gingerol for TNBC treatment that should be further demonstrated using in vivo assays.

Zygote arrest 1 like (ZAR2) and cell cycle in breast cancer cells

ZAR2 is a novel RNA-binding C4 zinc finger containing protein, with cell cycle dependent differential expression and nuclear/ cytosolic localization. We observed that ZAR2 expression is relatively lower in triple negative breast cancer cells (TNBC) compared to non-TNBC and forced expression in TNBC cells inhibit their growth and invasiveness. Knocking down ZAR2 in non-TNBC cells increased their growth and invasiveness. Our studies showed that ZAR2, is inhibited by a c-Myc regulated miRNA, hsa-miR-130a-5p. Studies demonstrate that ZAR2 localizes in the RNA processing P-bodies and regulates the turnover of maternal WEE1 mRNA in developing oocytes. WEE1 is a tyrosine kinase, which regulates G2/M checkpoint in cell cycle, is over-expressed in various cancer types and is associated with resistance development to DNA-damaging agents. WEE1, is identified as a potential molecular target for TNBC. WEE1 inhibition is exclusively toxic for cancer cells and does not harm healthy cells. Major objective of the proposed research is to evaluate the potential of a novel protein ZAR2 as a modulator of G2-M checkpoint and therapeutic target in breast cancer. c-Myc mediated downregulation of ZAR2 expression via hsa-miR-130a-5p, results in increased levels of WEE1 protein in breast cancer cells, increased proliferation and faster progression through cell cycle.

N-Linked glycosylation profiles of therapeutic induced senescent (TIS) triple negative breast cancer cells (TNBC) and their extracellular vesicle (EV) progeny.

Triple negative breast cancer (TNBC) has poor clinical outcomes and limited treatment options. Chemotherapy, while killing some cancer cells, can result in therapeutic-induced-senescent (TIS) cells. Senescent cells release significantly more extracellular vesicles (EVs) than non-senescent cells. Recently, N- and O-linked glycosylation alterations have been associated with senescence. We aimed to profile the N-linked glycans of whole cells, membrane, cytoplasm and EVs harvested from TIS TNBC cells and to compare these to results from non-senescent cells. TIS was induced in the Cal51 TNBC cells using the chemotherapeutic agent paclitaxel (PTX). Ultra-performance liquid chromatography (UPLC) analysis of exoglycosidase digested N-linked glycans was carried out on TIS compared to non-treated control cells. LC-Mass spectrometry (MS) analysis of the N-linked glycans and lectin blotting of samples was carried out to confirm the UPLC results. Significant differences were found in the N-glycan profile of the Cal51 membrane, cytoplasm and EV progeny of TIS compared to non-senescent cells. Protein mass spectrometry showed that the TIS cells contain different glycan modifying enzymes. The lectin, calnexin demonstrated a lower kDa size (∼58 kDa) in TIS compared to control cells (∼90 kDa) while Galectin 3 demonstrated potential proteolytic cleavage with 32 kDa and ∼22 kDa bands evident in TIS compared to non-senescent control cells with a major 32 kDa band only. TIS CAL51 cells also demonstrated a reduced adhesion to collagen I compared to control non-senescent cells. This study has shown that therapeutic-induced-senescent TNBC cells and their EV progeny, display differential N-glycan moieties compared to non-senescent Cal51 cells and their resultant EV progeny. For the future, N-glycan moieties on cancer senescent cells and their EV progeny hold potential for (i) the monitoring of treatment response as a liquid biopsy, and (ii) cancer senescent cell targeting with lectin therapies.

Secreted sphingomyelins modulate low mammary cancer incidence observed in certain mammals

Determining mechanisms that naturally protect species from developing cancer is critical in order to prevent and treat cancer. Here, we describe a novel cancer-suppressing mechanism, via the secretion of bioactive factors by mammary cells, that is present in domesticated mammals with a low mammary cancer incidence. Specifically, these bioactive factors induced triple-negative breast cancer cell (TNBC) death in vitro and reduced tumorigenicity in a xenograft TNBC mouse model in vivo. RNA deep sequencing showed significant downregulation of genes associated with breast cancer progression in secretome-cultured TNBC cells. Further in-depth multi-omics analysis identified sphingomyelins as key secreted factors, and their role was confirmed via inhibition of the sphingomyelin signaling pathway. We speculate that secreted sphingomyelins in the mammary gland of mammals with a naturally low incidence of mammary cancer mediate the elimination of cancer cells. This study contributes to the growing list of protective mechanisms identified in cancer-proof species.

Claudin 1 inhibits cell migration and increases intercellular adhesion in triple-negative breast cancer cell line.

Triple-negative "claudin 1 low" subtype represents around 15% of breast cancer and displays poor prognosis. The loss of claudin 1 is correlated with increased invasiveness and higher recurrence of the disease. Claudin 1 constitutes the backbone of the tight junction and is involved in cell-cell adhesion and migration processes. However, studies showed a controversial role of claudin 1 in cell migration.In this study, we aimed to clarify the effect of claudin 1 on migration of mesenchymal triple-negative breast cancer cells (TNBC). We reported that transient over expression of claudin 1 in MDA-MB-231 and Hs578T "claudin 1 low" TNBC cells inhibited cell migration using wound healing and transwell migration assays. In order to investigate more specifically the involvement of claudin 1, we generated stable MDA-MB-231 clones overexpressing claudin 1. Interestingly, the level of claudin 1 was correlated to the inhibition of cell migration and to the increase of cell-cell aggregation associated with enhanced formation of β-catenin adherens junction and occludin tight junction. Finally, we reported for the first time the key role of claudin 1 in the inhibition of cell migration process associated with the disappearance of stress fibers.These data suggest that re-expression of claudin 1 could be a promising strategy for regulating the migration of TNBC which no longer express claudin 1.

Targeting of the Eukaryotic Translation Initiation Factor 4A Against Breast Cancer Stemness.

Breast cancer stem cells (BCSCs) are intrinsically chemoresistant and capable of self-renewal. Following chemotherapy, patients can develop minimal residual disease due to BCSCs which can repopulate into a relapsed tumor. Therefore, it is imperative to co-target BCSCs along with the bulk tumor cells to achieve therapeutic success and prevent recurrence. So, it is vital to identify actionable molecular targets against both BCSCs and bulk tumor cells. Previous findings from our lab and others have demonstrated that inhibition of the emerging drug target eIF4A with Rocaglamide A (RocA) was efficacious against triple-negative breast cancer cells (TNBC). RocA specifically targets the pool of eIF4A bound to the oncogenic mRNAs that requires its helicase activity for their translation. This property enables specific targeting of tumor cells. The efficacy of RocA against BCSCs is unknown. In this study, we postulated that eIF4A could be a vulnerable node in BCSCs. In order to test this, we generated a paclitaxel-resistant TNBC cell line which demonstrated an elevated level of eIF4A along with increased levels of cancer stemness markers (ALDH activity and CD44), pluripotency transcription factors (SOX2, OCT4, and NANOG) and drug transporters (ABCB1, ABCG2, and ABCC1). Furthermore, genetic ablation of eIF4A resulted in reduced expression of ALDH1A1, pluripotency transcription factors and drug transporters. This pointed out that eIF4A is likely associated with selected set of proteins that are critical to BCSCs, and hence targeting eIF4A may eliminate BCSCs. Therefore, we isolated BCSCs from two TNBC cell lines: MDA-Bone-Un and SUM-159PT. Following RocA treatment, the self-renewal ability of the BCSCs was significantly reduced as determined by the efficiency of the formation of primary and secondary mammospheres. This was accompanied by a reduction in the levels of NANOG, OCT4, and drug transporters. Exposure to RocA also induced cell death of the BCSCs as evaluated by DRAQ7 and cell viability assays. RocA treatment induced apoptosis with increased levels of cleaved caspase-3. Overall, we identified that RocA is effective in targeting BCSCs, and eIF4A is an actionable molecular target in both BCSCs and bulk tumor cells. Therefore, anti-eIF4A inhibitors could potentially be combined synergistically with existing chemo-, radio- and/or immunotherapies.

Green (gemini) surfactant mediated gold nanoparticles green synthesis: Effect on triple negative breast cancer cells

In this paper, we report the synthesis of gold nanoparticles (AuNPs) using the aqueous neem (Azadirachta indica) fruit extract as a reducing agent and capped by two different capping agents (monomeric surfactant: hexadecyltrimethylammonium chloride (CTAC) and dimeric counterion coupled gemini surfactant (COCOGS): 1, 6-Bis (N,N-hexadecyl dimethylammonium) adipate (16-6-16)). The synthesized AuNPs have been characterized by different modern techniques such as, UV–Visible spectroscopy, HR-TEM, DLS, XRD, FTIR, and XPS analyses, etc. The FTIR measurements were used to evaluate the adsorption of CTAC and COCOGS on the AuNPs surface. A significant shift in the stretching vibrations of CTAC and COCOGS head functional groups suggested their orientation towards the AuNPs surface and was further supported by the high-resolution XPS spectra of CTAC and COCOGS on the AuNPs surface. The main objective of the work is to investigate how to achieve the stability and activity of COCOGS-AuNPs for developing novel anticancer agents against triple negative breast cancer cells (TNBC). Hence, we have synthesized CTAC-AuNPs and COCOGS-AuNPs and evaluated theirs in vitro cytotoxicity against TNBC cell line (MDA-MB-231) as well as in normal NIH3T3 cells. The synthesized COCOGS-AuNPs displayed the excellent cytotoxicity against selected TNBC cell lines without affecting normal cells. In addition to the analysis of cellular apoptosis with mitochondrial membrane potential (Δψm) loss demonstrated an increased apoptotic cell death after 24 h at their dose-dependent concentrations. Thus we conclude that the synthesized AuNPs may directly inhibit the TNBC cell growth and induced the tumor cell autophagy which consequently increasing cellular apoptosis.

22P - Therapeutic potential of connective tissue growth factor (CTGF) in triple-negative breast cancer

Background: Matricellular proteins are a subset of extracellular matrix (ECM) proteins which are dynamically expressed and serve many regulatory roles. Among matricellular proteins, the CCN family, a group of secreted proteins are known to regulate cell adhesion, migration, proliferation, differentiation, apoptosis, survival, senescence, and gene expression. Connective tissue growth factor (CTGF), also known as CCN2, is a member of the CCN family. CTGF is known to have many roles in biological processes such as cell proliferation, migration, adhesion, and angiogenesis. Methods: To investigate the function of CTGF in triple-negative breast cancer cells (TNBC), we silenced CTGF in TNBC cell lines using short hairpin RNA. Knockdown of CTGF was verified by western blot, qPCR, and immunostaining. The effect of CTGF knockdown on TNBCs was examined by cell proliferation assay, adhesion assay, migration assays, metabolism assays, and cell cycle analysis. Results: Knockdown of CTGF decreased cell proliferation, adhesion, migration, glucose uptake, ATP production and lactate production. Since CTGF is a secreted protein, we gave recombinant human CTGF (rhCTGF) to the cells and found that rhCTGF induced activation of the Src/FAK/MAPK pathway and led to expression of proteins related to cell cycle progression. Also, when CTGF-specific antibodies were given to the cells, they expressed cytotoxicity by neutralizing the extracellular CTGF and decreasing CTGF-mediated signalling. Conclusions: We suggest that the secreted CTGF mediates tumor cell progression via modulation of cell proliferation, adhesion, migration and metabolism and could possess a potential for being a therapeutic target. Legal entity responsible for the study: Hanyang University. Funding: National Research Foundation of Korea. Disclosure: All authors have declared no conflicts of interest.

High Glucose Represses the Anti-Proliferative and Pro-Apoptotic Effect of Metformin in Triple Negative Breast Cancer Cells.

Metformin, the most widely prescribed anti-diabetic drug, is shown to possess anti-cancer potential in treatment of cancers, including breast cancer; decreases breast cancer risk; and improves overall survival. However, reports suggest that higher glucose concentrations may negatively impact the anti-cancer efficacy of metformin. Therefore, we examined the anti-cancer potential of metformin in triple-negative breast cancer cells (TNBCs) exposed to different glucose (25 mM, 5.5 mM and zero glucose/glucose-starved) conditions. Our data indicates that a high glucose (25 mM) concentration (mimicking diabetes) significantly abrogated the effect of metformin on cell proliferation, cell death and cell cycle arrest in addition to loss of efficacy in inhibition of the mTOR pathway, a key metabolic pathway in TNBC cells. The mTOR pathway is activated in TNBCs compared to other subtypes of breast cancer, regulates the synthesis of proteins that are critical for the growth and survival of cancer cells and its activation is correlated to poor outcomes among TNBC patients, while also contributing to metastatic progression and development of resistance to chemotherapy/radiotherapy. Our studies were performed in two different types of TNBCs, MDA-MB-231 cells (mesenchymal stem cell-like (MSL)) and MDA-MB-468 (basal like-1 (BL-1)). Interestingly, lower concentrations of metformin (50, 100, 250, and 500 μM) significantly increased cell proliferation in 25 mM glucose exposed MDA-MB-231 cells, an effect which was not observed in MDA-MB-468 cells, indicating that the effective concentration of metformin when used as anti-cancer drug in TNBCs may have to be determined based on cell type and blood glucose concentration. Our data indicates that metformin treatment was most effective under zero glucose/glucose-starved conditions in MDA-MB-468 with a significant increase in the apoptotic population (62.3 ± 1.5%; p-value < 0.01). Under 5.5 mM glucose conditions in both MDA-MB-231 and MDA-MB-468 cells our data showed reduced viability of 73.56 ± 2.53%; p-value < 0.05 and 70.49 ± 1.68%; p-value < 0.001, respectively, along with a significant increase in apoptotic populations of both cell types. Furthermore, metformin (2 mM) inhibited the mTOR pathway and its downstream components under zero glucose/glucose-starved conditions indicating that using metformin in combination with agents that inhibit the glycolytic pathway should be more beneficial for the treatment of triple-negative breast cancers in diabetic individuals.