Negative Breast Cancer Cells Research Articles

Anti-cancer Effect of Recombinant PI-Laterosporulin10 as a Novel Bacteriocin with Selective Cytotoxicity on Triple Negative Breast Cancer Cells

Anti-microbial peptides (AMPs) are important factors of the innate immune system which perform a comprehensive spectrum of biological activities. The present study aims to examine the expression, purification, and cytotoxic effects of recombinant PI–laterosporulin10 (LS10) a defensing-like peptide. PI is a transmembrane peptide that helps to increase penetration and specificity of peptide targeting. PI–LS10 sequence was optimized and fused to a Xa protease site to achieve higher levels of expression. Then Xa–PI–LS10 was cloned into the pET-32a (+) vector and expressed in Escherichia coli BL21 (DE3). The fusion protein with a molecular weight of about 25.3 kDa was analyzed using the SDS-PAGE. The maximum expression was observed 8 h post-induction. After enzymatic cleavage, the purity of PI–LS10 was > 300 µg/ ml as the final yield. The recombinant PI–LS10 showed anti-cancer characteristics against breast cancer cell lines. MCF7 (non-triple negative) and MDA-MB-231 (triple negative) cells were treated with different concentrations of the PI–LS10 in order to evaluate their cytotoxic activity and efficiency in targeting triple negative cells. Our results suggest that PI–LS10 had a significant cytotoxic effect against breast cancer cells in comparison to the normal cell line. Triple negative breast cancer cell (MDA-MB-231) proliferation inhibited higher in 72 h after treatment compare MCF7 cells. In conclusion, the PI–LS10 peptide was produced successfully and its favorable anti-cancer activity against a breast cancer cell line was confirmed.

Elucidation of an mTORC2-PKC-NRF2 pathway that sustains the ATF4 stress response and identification of Sirt5 as a key ATF4 effector

Proliferating cancer cells are dependent on glutamine metabolism for survival when challenged with oxidative stresses caused by reactive oxygen species, hypoxia, nutrient deprivation and matrix detachment. ATF4, a key stress responsive transcription factor, is essential for cancer cells to sustain glutamine metabolism when challenged with these various types of stress. While it is well documented how the ATF4 transcript is translated into protein as a stress response, an important question concerns how the ATF4 message levels are sustained to enable cancer cells to survive the challenges of nutrient deprivation and damaging reactive oxygen species. Here, we now identify the pathway in triple negative breast cancer cells that provides a sustained ATF4 response and enables their survival when encountering these challenges. This signaling pathway starts with mTORC2, which upon sensing cellular stresses arising from glutamine deprivation or an acute inhibition of glutamine metabolism, initiates a cascade of events that triggers an increase in ATF4 transcription. Surprisingly, this signaling pathway is not dependent on AKT activation, but rather requires the mTORC2 target, PKC, which activates the transcription factor Nrf2 that then induces ATF4 expression. Additionally, we identify a sirtuin family member, the NAD+-dependent de-succinylase Sirt5, as a key transcriptional target for ATF4 that promotes cancer cell survival during metabolic stress. Sirt5 plays fundamental roles in supporting cancer cell metabolism by regulating various enzymatic activities and by protecting an enzyme essential for glutaminolysis, glutaminase C (GAC), from degradation. We demonstrate that ectopic expression of Sirt5 compensates for knockdowns of ATF4 in cells exposed to glutamine deprivation-induced stress. These findings provide important new insights into the signaling cues that lead to sustained ATF4 expression as a general stress-induced regulator of glutamine metabolism, as well as highlight Sirt5 an essential effector of the ATF4 response to metabolic stress.

The antimicrobial and the antiproliferative effect of human triple negative breast cancer cells using the greenly synthesized iron oxide nanoparticles

Greenly synthesized iron oxide nanoparticles (IONPs) were prepared from Spinacia oleracea leaf extract. They were coated with 10% polyethylene glycol (PEG) and conjugated with doxorubicin (DOX). They were characterized by UV–Vis spectrophotometer, X-ray diffraction, and Fourier transforms infrared spectroscopy (FTIR). They exhibited a particle size of 29.0 ± 1.2 nm, a polydispersity index of 0.52 ± 0.05, and zeta potential of −12.3 ± 0.1 mV. The absorption spectrum of the greenly synthesized IONPs was endorsed by a characteristic peak at 450 nm. FTIR revealed that DOX conjugated to PEGylated IONPs occurred via the interaction of the –NH2 group of DOX with –OH groups of PEG through hydrogen bonding. PEGylation, as well as DOX conjugation, improved the cytotoxic activity of IONPs on triple-negative breast cancer. Cytotoxic activity of DOX conjugated to PEGylated IONPs was significantly higher than free DOX. Furthermore, the IC50 of DOX conjugated PEGylated IONPs (0.1804 μg/mL) was lower than unloaded PEGylated IONPs (0.2119 μg/mL) and uncoated IONPs (0.3817 μg/mL), which was further verified by a lower percentage of closure area in the scratch test. Moreover, the zones of microbial inhibition of PEGylated and non-PEGylated IONPs were higher than the commonly used antimicrobial agents including ampicillin and gentamycin. In conclusion, the prepared nanoparticles offer potential passive target chemotherapy with lower dose than free DOX.

Pharmacological Activation of Potassium Channel Kv11.1 with NS1643 Attenuates Triple Negative Breast Cancer Cell Migration by Promoting the Dephosphorylation of Caveolin-1.

The prevention of metastasis is a central goal of cancer therapy. Caveolin-1 (Cav-1) is a structural membrane and scaffolding protein shown to be a key regulator of late-stage breast cancer metastasis. However, therapeutic strategies targeting Cav-1 are still lacking. Here, we demonstrate that the pharmacological activation of potassium channel Kv11.1, which is uniquely expressed in MDA-MB-231 triple negative breast cancer cells (TNBCs) but not in normal MCF-10A cells, induces the dephosphorylation of Cav-1 Tyr-14 by promoting the Ca2+-dependent stimulation of protein tyrosine phosphatase 1B (PTP1B). Consequently, the dephosphorylation of Cav-1 resulted in its disassociation from β-catenin, which enabled the accumulation of β-catenin at cell borders, where it facilitated the formation of cell–cell adhesion complexes via interactions with R-cadherin and desmosomal proteins. Kv11.1 activation-dependent Cav-1 dephosphorylation induced with NS1643 also reduced cell migration and invasion, consistent with its ability to regulate focal adhesion dynamics. Thus, this study sheds light on a novel pharmacological mechanism of promoting Cav-1 dephosphorylation, which may prove to be effective at reducing metastasis and promoting contact inhibition.

Silencing of COL3A1 represses proliferation, migration, invasion, and immune escape of triple negative breast cancer cells via down-regulating PD-L1 expression.

This study is designed to illuminate the specific role and underlying mechanism of collagen type III alpha 1 chain (COL3A1) in triple negative breast cancer (TNBC). Quantitative real-time polymerase chain reactionwas applied to examine mRNA expression of COL3A1. Western blot analysis was employed to determine protein levels of COL3A1, programmed death ligand 1 (PD-L1),Bcl-2, and cleaved caspase-3. Immunohistochemistry staining was utilized for assessing protein expression of Ki67 and COL3A1 in tissues. The proliferous capacity of cells was assessed through CCK-8 assay and 5-Ethynyl-2'-deoxyuridine assay. Cell apoptosis and the percentage of CD8+ T cells were measured using flow cytometry. Migration and invasion of TNBC cells were examined via transwell assay. Lactate dehydrogenase (LDH)release was measured via a LDH assay kit. For establishing a xenograft tumor model, MDA-MB-231 cells were injected into the flank of mice through subcutaneous injection. COL3A1 expression was raised in TNBC tissues and cells, and it was inversely associated with overall survival data of TNBC patients. COL3A1 downregulation repressed proliferation, invasion, migration, and immune escape of TNBC cells along with tumor growth of xenograft mice. In TNBC cells and tumor tissues of mice, protein expression of PD-L1 was reduced by COL3A1 knockdown. COL3A1 knockdown-mediated inhibitory effects on cell proliferation, migration, invasion, and immune escape were reversed by PD-L1 upregulation in vitro. Silencing of COL3A1 exerted an antitumor role in TNBC, implying its potential as a therapeutic target for TNBC.

Protein kinase inhibitor ceritinib blocks ectonucleotidase CD39 – a promising target for cancer immunotherapy

BackgroundAn important mechanism, by which cancer cells achieve immune escape, is the release of extracellular adenosine into their microenvironment. Adenosine activates adenosine A2A and A2B receptors on immune cells constituting...

Design, synthesis, bioevaluation, DFT, docking, and molecular dynamic simulation for selected novel 1,3,4-Oxadiazole - indole derivatives hybrid against estrogen receptor alpha

Breast tumors overexpress ER alpha and it initiates, as well as the progression of breast cancer. Studies have proven that anti-estrogen therapy (tamoxifen) is used to treat breast cancer. For the first time, in vitro bioevaluation, molecular docking, and DFT simulations were used to investigate the essential interactions of the estrogen receptor (ER) alpha with selected novel 1,3,4-Oxadiazole - indole derivatives hybrid against Triple Negative Breast Cancer (TNBC) cell lines. The key step of this synthesis is the oxidative cyclization of N-acylhydrazones, 2(a-j), in 20 min using reagent BTI [bis(trilfuoroacetoxy)iodobenzene]. Synthesized compounds, 3(a-j), were screened against a series of cancer cell lines, and among these compounds, the compound, 3d ((5′-Bromo-1H-indol-1-yl) methyl)-5′’-(3-bromo-4-methylphenyl)-1,3,4-Oxadiazole), as a potent molecule which displayed IC50 values of 10.56 and 22.61 µM against MDA MB 468, and MDA MB 231 cell lines respectively. In vitro antibody specific for Human Estrogen Receptor alpha assay showed an IC50 value of 5.27 µM for compound 3d. The structures were optimized to their molecular geometry (3d) by the DFT method with B3LYP hybrid functional and 6–311++g(d,p) basis set. The electrostatic potential map was plotted to understand the energy distribution and chemical reactive regions of the molecule. The optimized structures were used to perform in silico studies. Molecular docking followed by molecular dynamics trajectories is essential to investigate the stable binding of 3d to estrogen receptor alpha. Overall, results show that 3d has the potential to be further explored for the treatment of metastatic breast cancer.

Intratumoral xenogeneic tissue-specific cell immunotherapy inhibits tumor growth by increasing antitumor immunity in murine triple negative breast and pancreatic tumor models

Low immunogenicity in tumors and the immunosuppressive tumor microenvironment (TME) represent major obstacles to the full success of immunotherapy in cancer patients. A novel intratumoral xenogeneic tissue-specific cell immunotherapeutic approach could overcome the obstacles. Murine 4T1 triple negative breast cancer (TNBC) cells and Pan18 pancreatic ductal adenocarcinoma (PDAC) cells were used for establishing syngeneic graft tumor models to evaluate antitumor effect of intratumoral injection of xenogeneic tissue-specific cells. Responses to treatment were assessed by measuring tumor growth and tumor weight of the tumor-bearing mice. To investigate the mechanisms of action, tumor histology and immunohistochemistry and cytokine gene expression were measured. Splenic lymphocytes proliferation, cytokine production and cytotoxicity activities were also assessed. The findings showed that intratumoral injection of xenogeneic tissue-specific cells in monotherapy and combination with chemotherapy inhibit tumor growth. The therapeutic efficacy of intratumoral xenogeneic cells was significantly enhanced by the addition of cytotoxic chemotherapeutic agents. Mice that received combined treatment showed maximal attenuation in tumor growth rate. The antitumor immunity was explained by altered immune cell infiltration in tumors and immune cell functions. Our findings demonstrate that xenogeneic tissue-specific cells given intratumorally, provide a potent antitumor effect in murine breast and pancreatic tumor models by enhancing recruitment and activation of immune cells in tumors for local and systemic antitumor effects. Moreover, intratumoral xenogeneic cell treatment turns immunologically “cold” tumors to “hot” ones, generates systemic antitumor immunity, and synergizes with chemotherapy. Thus, the intratumoral xenogeneic tissue-specific cell immunotherapy may represent a useful therapeutic option to difficult-to-treat cancers.

Design and Validation of Nanofibers Made of Self-Assembled Peptides to Become Multifunctional Stimuli-Sensitive Nanovectors of Anticancer Drug Doxorubicin.

Self-assembled peptides possess remarkable potential as targeted drug delivery systems and key applications dwell anti-cancer therapy. Peptides can self-assemble into nanostructures of diverse sizes and shapes in response to changing environmental conditions (pH, temperature, ionic strength). Herein, we investigated the development of self-assembled peptide-based nanofibers (NFs) with the inclusion of a cell-penetrating peptide (namely gH625) and a matrix metalloproteinase-9 (MMP-9) responsive sequence, which proved to enhance respectively the penetration and tumor-triggered cleavage to release Doxorubicin in Triple Negative Breast Cancer cells where MMP-9 levels are elevated. The NFs formulation has been optimized via critical micelle concentration measurements, fluorescence, and circular dichroism. The final nanovectors were characterized for morphology (TEM), size (hydrodynamic diameter), and surface charge (zeta potential). The Doxo loading and release kinetics were studied in situ, by optical microspectroscopy (fluorescence and surface-enhanced Raman scattering–SERS). Confocal spectral imaging of the Doxo fluorescence was used to study the TNBC models in vitro, in cells with various MMP-9 levels, the drug delivery to cells as well as the resulting cytotoxicity profiles. The results confirm that these NFs are a promising platform to develop novel nanovectors of Doxo, namely in the framework of TNBC treatment.

In vitro radiosensitization of breast cancer with hypoxia-activated prodrugs.

KP167 is a novel hypoxia‐activated prodrug (HAP), targeting cancer cells via DNA intercalating and alkylating properties. The single agent and radiosensitizing efficacy of KP167 and its parental comparator, AQ4N, were evaluated in 2D and 3D cultures of luminal and triple negative breast cancer (TNBC) cell lines and compared against DNA damage repair inhibitors. 2D normoxic treatment with the DNA repair inhibitors, Olaparib or KU‐55933 caused, as expected, substantial radiosensitization (sensitiser enhancement ratio, SER0.01 of 1.60–3.42). KP167 induced greater radiosensitization in TNBC (SER0.01 2.53 in MDAMB‐231, 2.28 in MDAMB‐468, 4.55 in MDAMB‐436) and luminal spheroids (SER0.01 1.46 in MCF‐7 and 1.76 in T47D cells) compared with AQ4N. Significant radiosensitization was also obtained using KP167 and AQ4N in 2D normoxia. Although hypoxia induced radioresistance, radiosensitization by KP167 was still greater under 2D hypoxia, yielding SER0.01 of 1.56–2.37 compared with AQ4N SER0.01 of 1.13–1.94. Such data show KP167 as a promising single agent and potent radiosensitiser of both normoxic and hypoxic breast cancer cells, with greater efficacy in TNBCs.

Proteomic characterisation of triple negative breast cancer cells following CDK4/6 inhibition

When used in combination with hormone treatment, Palbociclib prolongs progression-free survival of patients with hormone receptor positive breast cancer. Mechanistically, Palbociclib inhibits CDK4/6 activity but the basis for differing sensitivity of cancer to Palbociclib is poorly understood. A common observation in a subset of Triple Negative Breast Cancers (TNBCs) is that prolonged CDK4/6 inhibition can engage a senescence-like state where cells exit the cell cycle, whilst, remaining metabolically active. To better understand the senescence-like cell state which arises after Palbociclib treatment we used mass spectrometry to quantify the proteome, phosphoproteome, and secretome of Palbociclib-treated MDA-MB-231 TNBC cells. We observed altered levels of cell cycle regulators, immune response, and key senescence markers upon Palbociclib treatment. These datasets provide a starting point for the derivation of biomarkers which could inform the future use CDK4/6 inhibitors in TNBC subtypes and guide the development of potential combination therapies.

Studies on the mode of action of synthetic diindolylmethane derivatives against triple negative breast cancer cells.

Diindolylmethane (DIM) is a metabolic product of indole-3-carbinol (I3C), the major phytochemicals present in cruciferous vegetables, which can modulate multiple signalling pathways in cancer. The present study deals with the mechanism of action of two synthetic biaryl conjugates of DIM in triple negative breast cancer cells. Out of 12 DIM derivatives tested, two compounds, DIM-1 and DIM-4, exhibit cytotoxicity with GI50 values of 9.83 ± 0.2195 μM and 8.726 ± 0.5234 μM, respectively, in 2D culture. In 3D culture, DIM-1 and DIM-4 show GI50 values of 24.000 ± 0.7240 μM and 19.230 ± 0.3754 μM, respectively. The non-toxic nature of the compounds was also established by the toxicity studies using the zebrafish model system. The two compounds induced apoptosis and anoikis in the cancer cells, which was confirmed by morphological analysis, nuclear fragmentation, membrane integrity assay, caspase activity measurements and modulation of pro/anti-apoptotic proteins. The compounds inhibited cell migration and MMP-2 and MMP-9 activities indicating their anti-metastatic property. They also reduced the expression of active Ras, phosphorylated forms of PI3K, Akt and mTOR. Immunofluorescence studies revealed the reduced expression of EGFR and pEGFR in treated cells. To conclude, DIM-1 and DIM-4 induced anti-breast cancer effects by blocking EGF receptor and subsequently inhibiting Ras-mediated PI3K-Akt-mTOR signalling pathway.

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.

MiR-589-5p Inhibits Cell Proliferation by Targeting Histone Deacetylase 3 in Triple Negative Breast Cancer

Histone deacetylase 3 (HDAC3) is a potential oncogene that is significantly up-regulated in patients with breast cancer. MicroRNAs (miRs) are a group of small non-coding and regulatory RNAs which have recently been proposed as promising molecules for breast cancer target therapy. In the current study, we investigated the impact of miR-589-5p/ HDAC3 axis on cancer cell development in triple negative breast cancer (TNBC) cells. In-silico analysis determined that miR-589-5p potentially targets HDAC3. We evaluated the HDAC3 and mir-589-5p expression levels in clinical samples and breast cancer cell lines including MDA-MB-231, MDA-MB-468, MCF-7 and MCF-10A. HDAC3 was knocked out to investigate its role on cancer cell progression. Anti-cancerous role of the miR-589-5p was assessed using an expression vector. We evaluated possible alteration in the cell cycle progression, cell viability and cell proliferation, after transient transfection. HDAC3 was over-expressed in TNBC clinical samples and breast cancer cell lines compared to non-cancerous controls while miR-589-5p was down regulated in cancer cells. Suppression of HDAC3 decreased the cell viability, cell proliferation and colony formation. Similar results were observed after over-expression of the miR-589-5p. Dual-Luciferase reporter assay confirmed the direct targeting of HDAC3 by miR-589-5p. Our results showed that miR-589-5p mediates its anti-proliferative effects on breast cancer cells via targeting HDAC3. These findings suggest that the miR-589-5p/ HDAC3 axis could be considered as a possible therapeutic strategy in TNBC.

In vitro characterization and molecular dynamic simulation of shikonin as a tubulin-targeted anticancer agent

Shikonin (SK), a naphthoquinone compound from the purple gromwell, Lithospermum erythrorhizon, possesses a considerable antiproliferative potential. By using a combination of biophysical techniques, cellular assays, immunofluorescence imaging, and molecular dynamic simulation, we identified a possible mechanism of action of SK. SK inhibited the viability of the triple negative breast cancer cells MDA-MB-231 (IC50 of 1 ± 0.1 μM), and its inhibitory effect was irreversible. It strongly suppressed the clonogenic and migratory potential of the cells. Although SK did not show any phase-specific inhibition of cell cycle progression, it induced apoptosis as confirmed by annexin-V-based flow cytometry and Western immunoblotting of PARP1. Probing further into its mechanism using a tryptophan-quenching assay, it was found that SK binds the microtubule-building protein tubulin with a dissociation constant (Kd) of 8 ± 2.7 μM, without grossly damaging the tertiary structure of the protein. The drug-bound tubulin could not assemble microtubules properly in vitro as confirmed by polymer mass analysis, turbidimetry analysis, and transmission electron microscopy, and in cells, as visualized by immunofluorescence imaging. In cells, SK also suppressed the dynamicity of microtubules as indicated by considerable acetylation of the cellular microtubules. The fine details of tubulin-SK interactions were then elucidated using molecular docking and molecular dynamic simulation. The free energy change of the interaction (ΔGbind,pred) was found to be −14.60 kcal/mol and the binding involved both the intermolecular van der Waals (ΔEvdw) and the electrostatic (ΔEele) interactions. Taken together, our data provide evidence for a possible mechanism of action of SK as a tubulin-targeted anticancer agent.

Thymoquinone upregulates IL17RD in controlling the growth and metastasis of triple negative breast cancer cells in vitro

BackgroundTriple negative breast cancer (TNBC) is a molecular subtype of breast cancer, which is a major health burden of females worldwide. Thymoquinone (TQ), a natural compound, has been found to be effective against TNBC cells, and this study identified IL17RD as a novel target of TQ in TNBC cells.MethodsWe have performed chromatin immunoprecipitation Sequence (ChIP-Seq) by MBD1 (methyl-CpG binding domain protein 1) antibody to identify genome-wide methylated sites affected by TQ. ChIP-seq identified 136 genes, including the tumor suppressor IL17RD, as a novel target of TQ, which is epigenetically upregulated by TQ in TNBC cell lines BT-549 and MDA-MB-231. The IL17RD expression and survival outcomes were studied by Kaplan–Meier analysis.ResultsTQ treatment inhibited the growth, migration, and invasion of TNBC cells with or without IL17RD overexpression or knockdown, while the combination of IL17RD overexpression and TQ treatment were the most effective against TNBC cells. Moreover, higher expression of IL17RD is associated with longer survival in TNBC patients, indicating potential therapeutic roles of TQ and IL17RD against TNBC.ConclusionsOur data suggest that IL17RD might be epigenetically upregulated in TNBC cell lines by TQ, and this might be one of the mechanisms by which TQ exerts its anticancer and antimetastatic effects on TNBC cells.

Nicotinic receptors modulate antitumor therapy response in triple negative breast cancer cells.

BACKGROUNDTriple negative breast cancer is more aggressive than other breast cancer subtypes and constitutes a public health problem worldwide since it has high morbidity and mortality due to the lack of defined therapeutic targets. Resistance to chemotherapy complicates the course of patients’ treatment. Several authors have highlighted the participation of nicotinic acetylcholine receptors (nAChR) in the modulation of conventional chemotherapy treatment in cancers of the airways. However, in breast cancer, less is known about the effect of nAChR activation by nicotine on chemotherapy treatment in smoking patients.AIMTo investigate the effect of nicotine on paclitaxel treatment and the signaling pathways involved in human breast MDA-MB-231 tumor cells.METHODSCells were treated with paclitaxel alone or in combination with nicotine, administered for one or three 48-h cycles. The effect of the addition of nicotine (at a concentration similar to that found in passive smokers’ blood) on the treatment with paclitaxel (at a therapeutic concentration) was determined using the 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The signaling mediators involved in this effect were determined using selective inhibitors. We also investigated nAChR expression, and ATP “binding cassette” G2 drug transporter (ABCG2) expression and its modulation by the different treatments with Western blot. The effect of the treatments on apoptosis induction was determined by flow cytometry using annexin-V and 7AAD markers.RESULTSOur results confirmed that treatment with paclitaxel reduced MDA-MB-231 cell viability in a concentration-dependent manner and that the presence of nicotine reversed the cytotoxic effect induced by paclitaxel by involving the expression of functional α7 and α9 nAChRs in these cells. The action of nicotine on paclitaxel treatment was linked to modulation of the protein kinase C, mitogen-activated protein kinase, extracellular signal-regulated kinase, and NF-κB signaling pathways, and to an up-regulation of ABCG2 protein expression. We also detected that nicotine significantly reduced the increase in cell apoptosis induced by paclitaxel treatment. Moreover, the presence of nicotine reduced the efficacy of paclitaxel treatment administered in three cycles to MDA-MB-231 tumor cells.CONCLUSIONOur findings point to nAChRs as responsible for the decrease in the chemotherapeutic effect of paclitaxel in triple negative tumors. Thus, nAChRs should be considered as targets in smoking patients.

Transcriptome-Wide Mapping of Small-Molecule RNA-Binding Sites in Cells Informs an Isoform-Specific Degrader of QSOX1 mRNA.

The interactions between cellular RNAs in MDA-MB-231 triple negative breast cancer cells and a panel of small molecules appended with a diazirine cross-linking moiety and an alkyne tag were probed transcriptome-wide in live cells. The alkyne tag allows for facile pull-down of cellular RNAs bound by each small molecule, and the enrichment of each RNA target defines the compound's molecular footprint. Among the 34 chemically diverse small molecules studied, six bound and enriched cellular RNAs. The most highly enriched interaction occurs between the novel RNA-binding compound F1 and a structured region in the 5' untranslated region of quiescin sulfhydryl oxidase 1 isoform a (QSOX1-a), not present in isoform b. Additional studies show that F1 specifically bound RNA over DNA and protein; that is, we studied the entire DNA, RNA, and protein interactome. This interaction was used to design a ribonuclease targeting chimera (RIBOTAC) to locally recruit Ribonuclease L to degrade QSOX1 mRNA in an isoform-specific manner, as QSOX1-a, but not QSOX1-b, mRNA and protein levels were reduced. The RIBOTAC alleviated QSOX1-mediated phenotypes in cancer cells. This approach can be broadly applied to discover ligands that bind RNA in cells, which could be bioactive themselves or augmented with functionality such as targeted degradation.

Eliciting anti-cancer immunity by genetically engineered multifunctional exosomes

Exosomes are cell-derived nanovesicles involved in regulating intercellular communications. In contrast to conventional nanomedicines, exosomes are characterized by unique advantages for therapeutic development. Despite their major successes in drug delivery, the full potential of exosomes for immunotherapy remains untapped. Herein we designed genetically engineered exosomes featured with surfaced-displayed antibody targeting groups and immunomodulatory proteins. Through genetic fusions with exosomal membrane proteins, Expi293F cell-derived exosomes were armed with monoclonal antibodies specific for human T-cell CD3 and epidermal growth factor receptor (EGFR) as well as immune checkpoint modulators, programmed death 1 (PD-1) and OX40 ligand (OX40L). The resulting genetically engineered multifunctional immune-modulating exosomes (GEMINI-Exos) can not only redirect and activate Tcells toward killing EGFR-positive triple negative breast cancer (TNBC) cells but also elicit robust anti-cancer immunity, giving rise to highly potent inhibition against established TNBC tumors in mice. GEMINI-Exos represent candidate agents for immunotherapy and may offer a general strategy for generating exosome-based immunotherapeutics with desired functions and properties.

113. 3D is Not Enough: Recapitulating the Tumor Microenvironment is Necessary to Elicit Increased Proliferation of Triple Negative Breast Cancer Cells In Vitro

113. 3D is Not Enough: Recapitulating the Tumor Microenvironment is Necessary to Elicit Increased Proliferation of Triple Negative Breast Cancer Cells In Vitro