Effects In Breast Cancer Cells Research Articles

CircRNA circRREB1 promotes tumorigenesis and progression of breast cancer by activating Erk1/2 signaling through interacting with GNB4

Current investigations have illuminated the essential roles played by circular RNAs (circRNAs) in driving breast cancer (BC) tumorigenesis. However, the functional implications and molecular underpinnings of most circRNAs in BC are not well characterized. Here, Circular RNA (circRNA) expression profiles were analyzed in four surgically resected BC cases along with adjacent non-cancerous tissues applying RNA microarray analysis. The levels and prognostic implications of circRREB1 in BC were subjected to quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). Experimental manipulation of circRREB1 levels in both in vivo and in vitro settings further delineated its role in BC cell growth, invasion, and metastasis. The mechanical verification of circRREB1's interaction with GNB4 was established through RNA pull-down, mass spectrometry, Western blot analysis, RNA immunoprecipitation assays (RIP), fluorescence ISH (FISH), and rescue experiments. We found that circRREB1 exhibited significant upregulation in BC tissues and cells, implicating its association with an unfavorable prognosis in BC patients. CircRREB1 knockdown elicited anti-proliferative, anti-migratory, anti-invasive, and pro-apoptotic effects in BC cells, whereas its upregulation exerted opposing influences. Follow-up mechanistic examinations suggested that circRREB1 might interact with GNB4 directly, inducing the activation of Erk1/2 signaling and driving BC progression. Our findings collectively indicate that the interplay of circRREB1 with GNB4 promotes Erk1/2 signaling, thereby fostering BC progression, and positioning circRREB1 as a candidate therapeutic target for intervention in BC.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer.

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

The ameliorative effect of rosmarinic acid and epigallocatechin gallate against doxorubicin-induced genotoxicity

Doxorubicin (Dox), an effective anticancer agent, is known for its genotoxic effects on normal cells. Phenolic compounds, renowned for their antitumor, antioxidant, and antigenotoxic properties, have gained prominence in recent years. This study investigates the individual and combined protective effects of rosmarinic acid (RA) and epigallocatechin gallate (EGCG) against Dox-induced genotoxicity using various in vitro test systems. The synergistic/antagonistic interaction of these combinations on Dox’s chemotherapeutic effect is explored in breast cancer cell lines. Both RA and EGCG significantly mitigate Dox-induced genotoxicity in comet, micronucleus, and Ames assays. While Dox exhibits higher selectivity against MCF-7 cells, EGCG and RA show greater selectivity against MDA-MB-231 cells. The coefficient of drug interaction reveals a synergistic effect when RA or EGCG is combined with Dox in breast cancer cells. In conclusion, both EGCG and RA effectively reduce Dox-induced genetic damage and enhance Dox’s cell viability-reducing effect in breast cancer cells.

The PIN1-YTHDF1 axis promotes breast tumorigenesis via the m6A-dependent stabilization of AURKA mRNA.

The post-transcriptional processing of N6-methyladenosine (m6A)-modified mRNA by YTH domain-containing family protein 1 (YTHDF1) plays a crucial role in the regulation of gene expression. Although YTHDF1 expression is frequently upregulated in breast cancer, the regulatory mechanisms for this remain unclear. In this study, we examined the role of peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) in regulating YTHDF1 stability in breast cancer cells. The WW domain of PIN1 interacted with YTHDF1 in a phosphorylation-dependent manner. Additionally, PIN1 overexpression increased YTHDF1 stability by preventing ubiquitin-dependent proteasomal degradation. Furthermore, using the MS2-tagged RNA pull-down assay, we identified Aurora kinase A (AURKA) mRNA as a bona fide substrate of YTHDF1. PIN1-mediated YTHDF1 stabilization increased the stability of AURKA mRNA in an m6A-dependent manner. Furthermore, YTHDF1 knockout reduced AURKA protein expression levels, resulting in anticancer effects in breast cancer cells, including decreased cell proliferation, cell cycle arrest at the G0/G1 phase, apoptotic cell death, and decreased spheroid formation. The anticancer effects induced by YTHDF1 knockout were reversed by AURKA overexpression. Similarly, the knockout of PIN1 produced comparable anticancer effects to those observed in YTHDF1-knockout cells, and these effects were reversed upon overexpression of YTHDF1. In conclusion, the findings of our study suggest that increased YTHDF1 stability induced by PIN1 promotes breast tumorigenesis via the stabilization of AURKA mRNA. Targeting the PIN1/YTHDF1 axis may represent a novel therapeutic strategy for breast cancer.

Natural-Product-Inspired Discovery of Trimethoxyphenyl-1,2,4-triazolosulfonamides as Potent Tubulin Polymerization Inhibitors.

An approach of natural product-inspired strategy and incorporation of an NP-privileged motif has been investigated for the discovery of new tubulin polymerization inhibitors. Two series, N-Arylsulfonyl-3-arylamino-5-amino-1,2,4-triazole derivatives, and their isomers were considered. The compounds were synthesized by construction of the N-aryl-1,2,4-triazole-3,5-diamine motif and sulfonylation. Although the chemo- and regioselectivity in sulfonylation were challenging due to multiple ring-tautomerizable-NH and exocyclic NH2 functionalities present in the molecular motifs, the developed synthetic method enabled the preparation of designed molecular skeletons with biologically important motifs. The approach also led to explore interesting molecular regio- and stereochemical aspects valuable for activity. The X-ray crystallography study indicated that the hydrogen bonding between the arylamine-NH and the arylsulfonyl-"O" unit and appropriate molecular-functionality topology allowed the cis-locking of two aryls, which is important for tubulin-binding and antiproliferative properties. All synthesized compounds majorly showed characteristic antiproliferative effects in breast cancer cells (MCF-7), and four compounds exhibited potent antiproliferative activity. One compound potently bound to tubulin at the colchicine site and inhibited tubulin polymerization in vitro. The compound significantly depolymerized microtubules in MCF-7 cells, arrested the cells at the G2/M phase, and induced cell death. This study represents the importance of the design strategy in medicinal chemistry and the molecular structural features relevant to anticancer anti-tubulin properties. The explored molecules have the potential for further development.

Abstract B105: Antineoplastic effects and expression modulations in proliferation/apoptosis related genes by riproximin in breast cancer cells

Abstract Background: Ribosomal inactivating proteins (RIPs) target the ribosomal machinery of target cells and stop the translational machinery irreversibly. Riproximin is a plant-based RIP which was extracted and purified from the plant “Ximenia americana”. Riproximin has demonstrated its anticancer effects against various in vitro and in vivo cancer models. In this study, the focus was to evaluate the effects of riproximin on proliferation and apoptosis of breast cancer cells at functional and molecular levels. Methods: MTT dye reduction assay and DAPI nuclear staining methodologies were used to highlight the riproximin mediated effects on proliferation and apoptosis in primary (MCF-7) and metastatic (MDA-MB-231) breast cancer cell lines. Afterwards, the two cell lines were used to investigate the expression modulations in genes related to PIK3/Akt and apoptosis pathways (84 genes/pathway) via real-time PCR methodology. The expression modulations were used to build the signalling pathways via Ingenuity Pathway Analysis supported by Qiagen software system. Results: Riproximin successfully halted the proliferation of the breast cancer cells with an average 50% inhibitory concentrations of 1.2 and 2.9 ng/ml after 72 hours exposure interval in MCF-7 and MDA-MB-231 cells, respectively. The protein also induced apoptotic effects in the two cell lines as reflected by shrinkage, blebbing and fragmentation of the nucleus/DNA content in a concentration dependant format. Substantial alterations (≥2fold) were observed in PIK3/Akt pathway genes (MCF-7: 49/84, MDA-MB-231: 28/84) in response to riproximin exposure. Similarly, the protein induced de-regulation (≥2fold) of apoptosis related 44/84 and 34/84 genes in MCF-7 and MDA-MB-231 cell lines, respectively. The Ingenuity Pathway Analysis revealed involvement of these genes at distinct positions in cell survival and death mechanisms. Conclusion: Riproximin demonstrated the substantial potential to induce the cytotoxic effects in breast cancer cells. The protein also de-regulated a significant number of proliferation and apoptosis related genes in breast cancer primary and metastatic cells. Further in vitro investigations are required to understand the fine molecular tuning being operated by this natural plant protein in cancer cells.  Citation Format: Asim Pervaiz, Asma Khan, Kiran Umer, Martin R. Berger. Antineoplastic effects and expression modulations in proliferation/apoptosis related genes by riproximin in breast cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B105.

Hsa_circ_0052611 and mir-767-5p guide the warburg effect, migration, and invasion of BRCA cells through modulating SCAI.

Noncoding RNAs are key regulators in the Warburg Effect, an emerging hallmark of cancer. We intended to investigate the role and mechanism of circular RNA hsa_circ_0052611 (circ_0052611) and microRNA (miR)-767-5p in breast cancer (BRCA) hallmarks, especially the Warburg Effect. Expression of circ_0052611 and SCAI was downregulated, and miR-767-5p was upregulated in human BRCA tissues and cells; moreover, circ_0052611 acted as a miR-767-5p sponge to modulate the expression of miR-767-5p-targeted SCAI. Functionally, re-expressing circ_0052611 suppressed migration, invasion, glucose uptake, lactate production, and extracellular acidification rate (ECAR) in BRCA cells, and promoted apoptotic rate. These effects were accompanied by decreased Vimentin, N-cadherin, Bcl-2, and LDHA, and increased E-cadherin and Bax. Consistently, exhausting miR-767-5p exerted similar effects in BRCA cells. High miR-767-5p could counteract the role of circ_0052611 overexpression, and low SCAI likewise blocked the role of miR-767-5p deletion. In vivo, upregulating circ_0052611 delayed tumor growth of BRCA cells by altering miR-767-5p and SCAI expression. circ_0052611/miR-767-5p/SCAI axis might boycott the malignancy of BRCA cells.

Targeting FOXP3 Tumor-Intrinsic Effects Using Adenoviral Vectors in Experimental Breast Cancer.

The regulatory T cell master transcription factor, Forkhead box P3 (Foxp3), has been detected in cancer cells; however, its role in breast tumor pathogenesis remains controversial. Here we assessed Foxp3 tumor intrinsic effects in experimental breast cancer using a Foxp3 binder peptide (P60) that impairs Foxp3 nuclear translocation. Cisplatin upregulated Foxp3 expression in HER2+ and triple-negative breast cancer (TNBC) cells. Foxp3 inhibition with P60 enhanced chemosensitivity and reduced cell survival and migration in human and murine breast tumor cells. We also developed an adenoviral vector encoding P60 (Ad.P60) that efficiently transduced breast tumor cells, reduced cell viability and migration, and improved the cytotoxic response to cisplatin. Conditioned medium from transduced breast tumor cells contained lower levels of IL-10 and improved the activation of splenic lymphocytes. Intratumoral administration of Ad.P60 in breast-tumor-bearing mice significantly reduced tumor infiltration of Tregs, delayed tumor growth, and inhibited the development of spontaneous lung metastases. Our results suggest that Foxp3 exerts protumoral intrinsic effects in breast cancer cells and that gene-therapy-mediated blockade of Foxp3 could constitute a therapeutic strategy to improve the response of these tumors to standard treatment.

Integrins and Actions of Androgen in Breast Cancer.

Androgen has been shown to regulate male physiological activities and cancer proliferation. It is used to antagonize estrogen-induced proliferative effects in breast cancer cells. However, evidence indicates that androgen can stimulate cancer cell growth in estrogen receptor (ER)-positive and ER-negative breast cancer cells via different types of receptors and different mechanisms. Androgen-induced cancer growth and metastasis link with different types of integrins. Integrin αvβ3 is predominantly expressed and activated in cancer cells and rapidly dividing endothelial cells. Programmed death-ligand 1 (PD-L1) also plays a vital role in cancer growth. The part of integrins in action with androgen in cancer cells is not fully mechanically understood. To clarify the interactions between androgen and integrin αvβ3, we carried out molecular modeling to explain the potential interactions of androgen with integrin αvβ3. The androgen-regulated mechanisms on PD-L1 and its effects were also addressed.

Anti-cancer effectiveness of a novel ceramide analog on chemo-sensitive and chemo-resistant breast cancers.

Ceramides are known to show anti-cancer activity. A novel ceramide analog, (S,E)-3-hydroxy-2-(2-hydroxybenzylidene)amino-N-tetradecylpropanamide (analog 315) was developed as part of a larger study focused on finding more effective breast cancer treatments. To assess whether analog 315 shows any or a combination of the following effects in breast cancer cells in vitro: inhibiting proliferation, inducing apoptosis, and altering protein expression. Also, to determine whether it inhibits chemo-resistant breast cancer tumor growth in vivo mouse model. In vitro cell proliferation and apoptosis after treatment with analog 315 were assessed in three breast cancer cell lines (MCF-7, MCF-7TN-R, and MDA-MB-231) and reported. Protein expression was assessed by microarray assay. For the in vivo studies, chemo-resistant breast cancer cells were used for tumor development in two groups of mice (treated and control). Analog 315 (25 mg/kg/day) or control (dimethyl sulfoxide) was administered intraperitoneally for 7 days. Effects of analog 315 on inhibiting the growth of chemo-resistant breast cancer tumors after treatment are reported. Analog 315 reduced MCF-7TN-R chemo-resistant tumor burden (volume and weight) in mice. Liver metastasis was observed in control mice, but not in the treated animals. Ki-67, a proliferation marker for breast cancer cells, increased significantly ( P  < 0.05) in control tumor tissue. In vitro studies showed that analog 315 inhibited cell proliferation, altered protein expression and induced apoptosis in all three breast cancer cell lines studied, of which the effects on MCF-7TN-R cells were the most significant. Analog 315 reduced tumor growth in chemo-resistant breast cancer, inhibited cell proliferation, altered protein expression, and induced apoptosis in all three cell lines studied.

Chemoproteomic Profiling Reveals that Anticancer Natural Product Dankastatin B Covalently Targets Mitochondrial VDAC3.

Chlorinated gymnastatin and dankastatin alkaloids derived from the fungal strain Gymnascella dankaliensis have been reported to possess significant anticancer activity but their mode of action is unknown. These members possess electrophilic functional groups that can might undergo covalent bond formation with specific proteins to exert their biological activity. To better understand the mechanism of action of this class of natural products, we mapped the proteome-wide cysteine reactivity of the most potent of these alkaloids, dankastatin B, by using activity-based protein profiling chemoproteomic approaches. We identified a primary target of dankastatin B in breast cancer cells as cysteine C65 of the voltage-dependent anion-selective channel on the outer mitochondrial membrane VDAC3. We demonstrated direct and covalent interaction of dankastatin B with VDAC3. VDAC3 knockdown conferred hypersensitivity to dankastatin B-mediated antiproliferative effects in breast cancer cells, thus indicating that VDAC3 was at least partially involved in the anticancer effects of this natural product. Our study reveals a potential mode of action of dankastatin B through covalent targeting of VDAC3 and highlights the utility of chemoproteomic approaches in gaining mechanistic understanding of electrophilic natural products.

Resveratrol-Loaded Polymeric Nanoparticles: The Effects of D-α-Tocopheryl Polyethylene Glycol 1000 Succinate (TPGS) on Physicochemical and Biological Properties against Breast Cancer In Vitro and In Vivo.

Resveratrol (RSV), a phytoalexin from grapes and peanuts, has been reported to exhibit antiproliferative effects on various cancer cell lines. In breast cancer, RSV has been demonstrated to exert an antiproliferative effect on both hormone-dependent and hormone-independent breast cancer cell lines. However, RSV is a lipophilic drug, and its therapeutic effect could be improved through nanoencapsulation. Functionalizing polymeric nanoparticles based on polycaprolactone (PCL) with polyethylene glycol 1000 tocopheryl succinate (TPGS) has been reported to prolong drug circulation and reduce drug resistance. However, the effect of TPGS on the physicochemical properties and biological effects of breast cancer cells remains unclear. Therefore, this study aimed to develop RSV-loaded PCL nanoparticles using nanoprecipitation and investigate the effect of TPGS on the nanoparticles' physicochemical characteristics (particle size, zeta potential, encapsulation efficiency, morphology, and release rate) and biological effects on the 4T1 breast cancer cell line (cytotoxicity and cell uptake), in vitro and in vivo. The optimized nanoparticles without TPGS had a size of 138.1 ± 1.8 nm, a polydispersity index (PDI) of 0.182 ± 0.01, a zeta potential of -2.42 ± 0.56 mV, and an encapsulation efficiency of 98.2 ± 0.87%, while nanoparticles with TPGS had a size of 127.5 ± 3.11 nm, PDI of 0.186 ± 0.01, zeta potential of -2.91 ± 0.90 mV, and an encapsulation efficiency of 98.40 ± 0.004%. Scanning electron microscopy revealed spherical nanoparticles with low aggregation tendency. Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) identified the constituents of the nanoparticles and the presence of drug encapsulation in an amorphous state. In vitro release studies showed that both formulations followed the same dissolution profiles, with no statistical differences. In cytotoxicity tests, IC50 values of 0.12 µM, 0.73 µM, and 4.06 µM were found for the formulation without TPGS, with TPGS, and pure drug, respectively, indicating the potentiation of the cytotoxic effect of resveratrol when encapsulated. Flow cytometry and confocal microscopy tests indicated excellent cellular uptake dependent on the concentration of nanoparticles, with a significant difference between the two formulations, suggesting that TPGS may pose a problem in the endocytosis of nanoparticles. The in vivo study evaluating the antitumor activity of the nanoparticles confirmed the data obtained in the in vitro tests, demonstrating that the nanoparticle without TPGS significantly reduced tumor volume, tumor mass, maintained body weight, and improved survival in mice. Moreover, the biochemical evaluation evidenced possible hepatotoxicity for formulation with TPGS.

Erythrocyte−cancer hybrid membrane-coated reduction-sensitive nanoparticles for enhancing chemotherapy efficacy in breast cancer

Cell-membrane-coated biomimetic nanoparticles (NPs) have attracted great attention due to their prolonged circulation time, immune escape mechanisms and homotypic targeting properties. Biomimetic nanosystems from different types of cell -membranes (CMs) can perform increasingly complex tasks in dynamic biological environments thanks to specific proteins and other properties inherited from the source cells. Herein, we coated doxorubicin (DOX)-loaded reduction-sensitive chitosan (CS) NPs with 4T1 cancer cell -membranes (CCMs), red blood cell -membranes (RBCMs) and hybrid erythrocyte-cancer membranes (RBC-4T1CMs) to enhance the delivery of DOX to breast cancer cells. The physicochemical properties (size, zeta potential and morphology) of the resulting RBC@DOX/CS-NPs, 4T1@DOX/CS-NPs and RBC-4T1@DOX/CS-NPs, as well as their cytotoxic effect and cellular NP uptake in vitro were thoroughly characterized. The anti-cancer therapeutic efficacy of the NPs was evaluated using the orthotopic 4T1 breast cancer model in vivo. The experimental results showed that DOX/CS-NPs had a DOX-loading capacity of 71.76 ± 0.87 %, and that coating of DOX/CS-NPs with 4T1CM significantly increased the NP uptake and cytotoxic effect in breast cancer cells. Interestingly, by optimizing the ratio of RBCMs:4T1CMs, it was possible to increase the homotypic targeting properties towards breast cancer cells. Moreover, in vivo tumor studies showed that compared to control DOX/CS-NPs and free DOX, both 4T1@DOX/CS-NPs and RBC@DOX/CS-NPs significantly inhibited tumor growth and metastasis. However, the effect of 4T1@DOX/CS-NPs was more prominent. Moreover, CM-coating reduced the uptake of NPs by macrophages and led to rapid clearance from the liver and lungs in vivo, compared to control NPs. Our results suggest that specific self-recognition to source cells resulting in homotypic targeting increased the uptake and the cytotoxic capacity of 4T1@DOX/CS-NPs by breast cancer cells in vitro and in vivo. In conclusion, tumor-disguised CM-coated DOX/CS-NPs exhibited tumor homotypic targeting and anti-cancer properties, and were superior over targeting with RBC-CM or RBC-4T1 hybrid membranes, suggesting that the presence of 4T1-CM is critical for treatment outcome.

Orally Administered Curcumin Inhibits Breast Cancer In vivo and Reduces Cell Proliferation In vitro in an Iron Dependent Manner

BACKGROUNG: Increased intracellular iron metabolism is a hallmark of breast cancer. Curcumin is an iron chelator with suggested anti-proliferative effects in breast cancer cell lines. However, preclinical studies in murine models are required to validate these important benefits AIMS: Therefore, this study was aimed to determine if the iron-chelating properties of curcumin are responsible for its anti-proliferative effect in breast cancer cells and to investigate the translation of this effect to in vivo models METHODS: For in vitro experiments, human MCF-7 and mouse 4T1 breast cancer cells were tested. Cell proliferation was assessed in presence and absence of different concentrations of FAC (ferric ammonium citrate) and curcumin. For in vivo studies, 4T1 cells were implanted into BALB/c mice. After tumor development, animals were divided into four groups (n=5); control, curcumin, optimized curcumin (OC) and chemotherapy group. Tumor volumes were calculated prior and posterior oral gavage treatments. RESULT: Curcumin inhibited cell proliferation in both MCF-7 and 4T1 cell lines in a seemingly iron-dependent manner. FAC addition inhibited the anti-proliferative effect exhibited by curcumin. Moreover, curcumin group showed a significantly decreased in tumor growth; interestingly, treatment with OC supplement induced the opposite effect. CONCLUSION: These results suggest that curcumin may have an important positive impact in breast cancer, due to its iron dependent anti-proliferative properties.

A functional genetic screen for metabolic proteins unveils GART and the de novo purine biosynthetic pathway as novel targets for the treatment of luminal A ERα expressing primary and metastatic invasive ductal carcinoma.

Targeting tumor cell metabolism is a new frontier in cancer management. Thus, metabolic pathway inhibitors could be used as anti-estrogen receptor α (ERα) breast cancer (BC) drugs. Here, the interplay among metabolic enzyme(s), the ERα levels and cell proliferation was studied. siRNA-based screen directed against different metabolic proteins in MCF10a, MCF-7 and MCF-7 cells genetically resistant to endocrine therapy (ET) drugs and metabolomic analyses in numerous BC cell lines unveil that the inhibition of GART, a key enzyme in the purine de novo biosynthetic pathway, induces ERα degradation and prevent BC cell proliferation. We report here that a reduced GART expression correlates with a longer relapse-free-survival (RFS) in women with ERα-positive BCs. ERα-expressing luminal A invasive ductal carcinomas (IDCs) are sensitive to GART inhibition and GART expression is increased in receptor-positive IDCs of high grade and stage and plays a role in the development of ET resistance. Accordingly, GART inhibition reduces ERα stability and cell proliferation in IDC luminal A cells where it deregulates 17β-estradiol (E2):ERα signaling to cell proliferation. Moreover, the GART inhibitor lometrexol (LMX) and drugs approved for clinical treatment of primary and metastatic BC (4OH-tamoxifen and the CDK4/CDK6 inhibitors) exert synergic antiproliferative effects in BC cells. In conclusion, GART inhibition by LMX or other inhibitors of the de novo purine biosynthetic pathway could be a novel effective strategy for the treatment of primary and metastatic BCs.

Truncation of GalNAc-type O-glycans suppresses CD44-mediated osteoclastogenesis and bone metastasis in breast cancer.

The glycoprotein CD44 is a key regulator of malignant behaviors in breast cancer cells. To date, hyaluronic acid (HA)-CD44 signaling pathway has been widely documented in the context of metastatic bone diseases. Core 1 β1,3-galactosyltransferase (C1GALT1) is a critical enzyme responsible for the elongation of O-glycosylation. Aberrant O-glycans are recognized as a hallmark in cancers. However, the effects of C1GALT1 on CD44 signaling and bone metastasis remain unclear. In this study, immunohistochemical analysis indicated that C1GALT1 expression positively correlates with CD44 in breast cancer. Silencing C1GALT1 accumulates the Tn antigen on CD44, which decreases CD44 levels and osteoclastogenic signaling. Mutations in the O-glycosites on the stem region of CD44 impair its surface localization as well as suppress cell-HA adhesion and osteoclastogenic effects of breast cancer cells. Furthermore, in vivo experiments demonstrated the inhibitory effect of silencing C1GALT1 on breast cancer bone metastasis and bone loss. In conclusion, our study highlights the importance of O-glycans in promoting CD44-mediated tumorigenic signals and indicates a novel function of C1GALT1 in driving breast cancer bone metastasis. Implications: Truncation of GalNAc-type O-glycans by silencing C1GALT1 suppresses CD44-mediated osteoclastogenesis and bone metastasis in breast cancer; targeting the O-glycans on CD44 may serve as a potential therapeutic target for blocking cancer bone metastasis.

Combinations of vitamin A and D induced are synergistic in breast cancer cells and alter gene expression in the endoplasmic reticulum stress, unfolded protein and estrogen signaling canonical pathways

Introduction: Numerous studies over the past 30 years have shown that bioactive compounds present in functional foods, including vitamins, minerals and phytochemicals reduce cancer risk. For example, vitamins A and D derivatives found in fruits, vegetables, and dairy products, reduce the growth of breast, bladder, head, neck, lung, prostate, and skin cancers. However, the effects of these combined vitamins have not been previously reported for breast cancer.Aims: To investigate the activities of vitamin A (all-trans-retinoic acid; ATRA), as well as vitamins D2 and D3 in combination in the breast epithelial cancer cell lines T47D:A18, MCF-7, and SK-BR-3 and perform whole genome analysis in MCF-7 cells using RNA-seq.Methods: Breast cancer cells were cultured in appropriate media and treated with ATRA, D2 or D3 alone in concentrations from 1-10 μg/ml, or in combination at 1, 5, and 10 μg/ml. The CellTiter-Glo® 2.0 assay, Caspase-Glo®3/7, Caspase®8, and ApoTox-Glo™ Triplex assays measured cell viability and apoptosis. The effect of treatment on autophagy in MCF-7 cells was measured with a CYTO-ID® Autophagy Detection Kit 2.0. The whole transcriptome analysis was assessed using mRNA-seq and qPCR.Results: Separately, ATRA, D2, and D3 all reduced the viability of all breast cancer cell lines tested, with median inhibitory concentrations (IC50) between 2.1 to 31.7 μg/ml. However, when breast cancer cells were treated with combinations of ATRA+D2+D3, the IC50 was reduced indicating synergism. In MCF-7 cells, 5-flurouracil (5-FLU) had an IC50 of 1.37 µg/ml, while the vitamin A and D combination had an IC50 of 1.5 µg/ml, indicating the combination was ~90% as effective as 5-FLU. Treatment of MCF-7 cells with ATRA+D2+D3 enhanced caspase 3/7 activity, as well as the expression of Bax, BAD, PTEN and p53 (apoptosis canonical pathway), as well as induced autophagy. Whole genome analysis of treated MCF-7 cells showed a significant upregulation in gene expression in the autophagy, endoplasmic reticulum stress and the unfolded protein response apoptosis canonical pathways. Furthermore, MCF-7 cells treated with ATRA+D2+D3 demonstrated significant downregulation of gene expression in estrogen-mediated S phase entry and estrogen signaling canonical pathways suggesting antiestrogenic effects. Conclusions: Vitamins A and D combinations had synergistic effects in breast cancer cells and induced both apoptosis and autophagy. Transcriptional profiling showed significant alterations in gene expression patterns and upregulation of multiple cancer signaling pathways supporting the hypothesis that combining vitamins A and D is a more effective treatment than either vitamin alone. Keywords: all-trans-retinoic acid (ATRA), Vitamin D2, Vitamin D3, breast cancer cells, apoptosis, estrogen receptors

Estrogen receptor alpha mutations regulate gene expression and cell growth in breast cancer through microRNAs.

Estrogen receptor α (ER) mutations occur in up to 30% of metastatic ER-positive breast cancers. Recent data has shown that ER mutations impact the expression of thousands of genes not typically regulated by wildtype ER. While the majority of these altered genes can be explained by constant activity of mutant ER or genomic changes such as altered ER binding and chromatin accessibility, as much as 33% remain unexplained, indicating the potential for post-transcriptional effects. Here, we explored the role of microRNAs in mutant ER-driven gene regulation and identified several microRNAs that are dysregulated in ER mutant cells. These differentially regulated microRNAs target a significant portion of mutant-specific genes involved in key cellular processes. When the activity of microRNAs is altered using mimics or inhibitors, significant changes are observed in gene expression and cellular proliferation related to mutant ER. An in-depth evaluation of miR-301b led us to discover an important role for PRKD3 in the proliferation of ER mutant cells. Our findings show that microRNAs contribute to mutant ER gene regulation and cellular effects in breast cancer cells.

Eribulin Treatment Promotes Re-expression of Estrogen Receptor in Endocrine Therapy-resistant Hormone Receptor-positive Breast Cancer Cells.

Hypoxia is significantly associated with the development of drug resistance, and endocrine therapy is ineffective against hormone receptor (HR)-positive breast cancer in hypoxic tumor environments. Eribulin has a unique anticancer effect in breast cancer cells and improves tumor hypoxia by vascular remodeling. Therefore, we investigated the effect of eribulin on HR-positive breast cancer cells that were resistant to endocrine blockade. We established hypoxia-resistant breast cancer cell lines by continuous culture in a hypoxic environment. Parental and hypoxia-resistant cell lines were treated with eribulin and/or tamoxifen, and estrogen receptor (ER)-, epithelial-mesenchymal transition-, and hypoxia-related gene and protein expression changes in each surviving cell line were assessed. In addition, proliferation was assessed after eribulin treatment in the parental and hypoxia-resistant cell lines. We also assessed the effect of eribulin in vivo using subcutaneous xenograft models. Hypoxia-resistant cell lines showed significantly decreased expression of epithelial and ER-related markers and exhibited a higher level of resistance to tamoxifen. Conversely, eribulin treatment increased epithelial and ER-related gene and protein expression in hypoxia-resistant cell lines and enhanced the anticancer effect of tamoxifen. In in vivo xenograft models, eribulin treatment of hypoxia- and tamoxifen-resistant tumors slightly induced the re-expression of ER. In addition, hypoxia-resistant tumors treated with eribulin tended to respond better to tamoxifen. Eribulin ameliorated the aggressive behavior caused by hypoxia and induced the re-expression of ER in hypoxia-resistant breast cancer cells. Eribulin treatment of HR-positive breast cancer may resensitize cells to hormone blockade.

Small Molecule-Activated O-GlcNAcase for Spatiotemporal Removal of O-GlcNAc in Live Cells.

The nutrient sensor O-linked N-acetylglucosamine (O-GlcNAc) is a post-translational modification found on thousands of nucleocytoplasmic proteins. O-GlcNAc levels in cells dynamically respond to environmental cues in a temporal and spatial manner, leading to altered signal transduction and functional effects. The spatiotemporal regulation of O-GlcNAc levels would accelerate functional interrogation of O-GlcNAc and manipulation of cell behaviors for desired outcomes. Here, we report a strategy for spatiotemporal reduction of O-GlcNAc in live cells by designing an O-GlcNAcase (OGA) fused to an intein triggered by 4-hydroxytamoxifen (4-HT). After rational protein engineering and optimization, we identified an OGA-intein variant whose deglycosidase activity can be triggered in the desired subcellular compartments by 4-HT in a time- and dose-dependent manner. Finally, we demonstrated that 4-HT activation of the OGA-intein fusion can likewise potentiate inhibitory effects in breast cancer cells by virtue of the reduction of O-GlcNAc. The spatiotemporal control of O-GlcNAc through the chemically activatable OGA-intein fusion will facilitate the manipulation and functional understanding of O-GlcNAc in live cells.