Drug-resistant Breast Cancer Cells Research Articles

Metformin suppresses proliferation and invasion of drug-resistant breast cancer cells by activation of the Hippo pathway.

Drug resistance limits the clinical efficacy of breast cancer therapies, and overexpression or activation of Yes‐associated protein (YAP) is common in drug‐resistant cancer cells. Thus, inhibition of YAP may reduce resistance to anti‐cancer drugs. Metformin (MET), a first‐line diabetes medication that also has anti‐tumour activities, induces AMP‐activated protein kinase (AMPK), directly phosphorylates YAP and inhibits YAP transcriptional activity. In this study, we determined the effect of MET on the proliferation and invasion of drug‐resistant breast cancer cells and then investigated the underlying molecular mechanism. Our in vivo and in vitro experiments indicated that MET suppressed breast cancer by an AMPK‐independent pathway to decrease YAP nuclear localization. In drug‐sensitive cells, MET activated the Hippo pathway by increasing KIBRA and FRMD6 expression, but this did not occur in drug‐resistant cells. Scribble (SCRIB), a cell polarity protein, was notably down‐regulated in tamoxifen‐ and paclitaxel‐resistant breast cancer cells relative to sensitive cells. We also found that MET suppressed the proliferation and invasion of drug‐resistant breast cancer cells by increasing the expression and cell membrane localization of SCRIB, which enhanced the interaction of SCRIB with MST1 and LATS1, and inhibited YAP nuclear localization and transcriptional activity.

Proteomic Level Changes on Treatment in MCF-7/DDP Breast Cancer Drug- Resistant Cells.

Background LCL161, a SMAC’S small molecule mimetic, can bind to a variety of IAPs and activate Caspases. We found that on its own, LCL161induces apoptosis of drug-resistant breast cancer cells by binding to a variety of IAPs and activating Caspases. However, when LCL161 is used in combination with Caspase Inhibitors (CI), its capacity to induce apoptosis of breast cancer cells is enhanced.Objective To carry out proteomic and bioinformatics analysis of LCL161 in combination with CI. We aim to identify the key proteins and mechanisms of breast cancer drug-resistant apoptosis, thereby aiding in the breast cancer drug resistance treatment and identification of drug targeting markers.Methods Cell culture experiments were carried out to explore the effect of LCL161 combined with CI on the proliferation of breast cancer drug-resistant cells. Proteomic analysis was carried out to determine the protein expression differences between breast cancer drug-resistant cells and LCL161 combined with CI treated cells. Bioinformatics analysis was carried out to determine its mechanism of action. Validation of proteomics results was done using Parallel Reaction Monitoring (PRM).Results Cell culture experiments showed that LCL161 in combination with CI can significantly promote the apoptosis of breast cancer drug-resistant cells. Up-regulation of 92 proteins and down-regulation of 114 proteins protein were noted, of which 4 were selected for further validation.Conclusion Our results show that LCL161 combined with CI can promote the apoptosis of drug-resistant breast cancer cells by down-regulation of RRM2, CDK4, and ITGB1 expression through Cancer pathways, p53 or PI3K-AKT signaling pathway. In addition, the expression of CDK4, RRM2, and CDC20 can be down-regulated by the nuclear receptor pathway to affect DNA transcription and replication, thereby promoting apoptosis of breast cancer drug-resistant cells.

Dihydroartemisinin-Loaded Magnetic Nanoparticles for Enhanced Chemodynamic Therapy.

Recently, chemodynamic therapy (CDT) has represented a new approach for cancer treatment with low toxicity and side effects. Nonetheless, it has been a challenge to improve the therapeutic effect through increasing the amount of reactive oxygen species (ROS). Herein, we increased the amount of ROS agents in the Fenton-like reaction by loading dihydroartemisinin (DHA) which was an artemisinin (ART) derivative containing peroxide groups, into magnetic nanoparticles (MNP), thereby improving the therapeutic effect of CDT. Blank MNP were almost non-cytotoxic, whereas three MNP loading ART-based drugs, MNP-ART, MNP-DHA, and MNP-artesunate (MNP-AS), all showed significant killing effect on breast cancer cells (MCF-7 cells), in which MNP-DHA were the most potent. What’s more, the MNP-DHA showed high toxicity to drug-resistant breast cancer cells (MCF-7/ADR cells), demonstrating its ability to overcome multidrug resistance (MDR). The study revealed that MNP could produce ferrous ions under the acidic condition of tumor microenvironment, which catalyzed DHA to produce large amounts of ROS, leading to cell death. Further experiments also showed that the MNP-DHA had significant inhibitory effect on another two aggressive breast cancer cell lines (MDA-MB-231 and MDA-MB-453 cells), which indicated that the great potential of MNP-DHA for the treatment of intractable breast cancers.

Facile synthesis of biodegradable flower-like hydroxyapatite for drug and gene delivery

Controlled synthesis of hierarchical hydroxyapatite materials is a hot research topic because of the excellent biocompatibility and bioactivity of the materials. In this study, flower-like hydroxyapatite spheres (FHAPS) were facile synthesized in one pot using Al(OH)3 as a structure-directing agent. The prepared FHAPS comprised nanosheets possessing a uniform diameter of approximately 4 µm. Notably, the FHAPS can be degraded in solutions with a pH of 5.5 for 144 h or incubated with cells for 48 h. In addition, the FHAPS have rough surfaces, which exhibit high loading contents for the anticancer drug doxorubicin (DOX, 9.1%) and siRNA (2.0%). Thus, the FHAPS can effectively deliver DOX into drug-resistant breast cancer cells to exert an excellent killing effect compared with free DOX and transfect siRNA into tumor cells to interfere with the expression of the target protein. Taken together, this work successfully prepared FHAPS via a convenient synthesis route that shows high delivery efficiency for anticancer drugs and siRNA.

Cytotoxicity of Novel Redox Sensitive PEG2000-S-S-PTX Micelles against Drug-Resistant Ovarian and Breast Cancer Cells.

Since the last decade, it is established that nonspecific delivery of chemotherapeutics fails to effectively treat cancer due to systemic cytotoxicity, poor biodistribution at tumor site and most importantly the development of drug resistance (MDR). Stimuli-sensitive drug delivery systems gained significant attention in recent years for effective tumor therapy and reversal of MDR. The aim of this study was developing a redox sensitive micellar prodrug system, by taking the advantage of the significant difference in GSH levels between extracellular and intracellular environments, but more importantly in healthy and tumor tissues. Redox sensitive PEG2000-S-S-PTX micelles were developed for intracellular paclitaxel delivery and characterized in vitro. In vitro release studies were carried out and followed by cytotoxicity studies in chemo-resistant ovarian and breast cancer cells in various reducing environments for different time periods to confirm their potential. PEG2000-S-S-PTX, was synthesized and characterized as a redox sensitive micellar prodrug system. The reduction sensitivity and in vitro PTX release properties were confirmed in reducing environments comparatively with physiological conditions. Cytotoxicity studies suggested that ovarian (SK-OV-3) cells could be better candidates for treatment with redox-sensitive drug delivery systems than breast (MCF-7) cancer cells. The results of this study highlights the importance of personalized therapy since no fits-for-all system can be developed for different cancer with significantly different metabolic activities. Graphical Abstract Schematic representation of self-assembly of reduction-sensitive PEG2000-S-S-PTX micelles and GSH dependent release of PTX.

Abstract P6-03-04: Microenvironment-induced epigenetic reprogramming imposes drug-tolerant states in breast cancer cells

Abstract Development of resistance to breast cancer (BC) therapy is frustratingly common. Multiple mechanisms of resistance have been identified including selection of genetic resistance, redundant signaling, and others. More recently, rare cancer cells were shown to be sporadically reprogrammed by the presence of anti-cancer drugs into transiently resistant states, then to expand later after cessation of therapy. We have demonstrated that the physical character and composition of tumor microenvironment (ME) components are determinants of BC cell drug resistance, however, the mechanism by which this phenomenon occurs is unclear. We hypothesize that epigenetic reprogramming is not rare or sporadic, indeed, that specific tumor ME components impose epigenetic states that beget the expression of gene clusters that put cancer cells into drug-tolerant states. Our current pharmacopeia targets cancer cells, not their ME. Some tumor ME components, e.g. extracellular matrices (ECM), have half-lives that span years, and growth factors with typically short half-lives can be stabilized by direct association with ECM. Thus, a ME-imposed drug tolerance mechanism would explain how resistance can arise rapidly, in multiple locations, without the need for genetic selection. Because ME-cell interactions lead to activation of specific pathways, based on canonical receptor-ligand models, we should be able to circumvent ME-imposed drug tolerance by addition of molecules that alter ME-induced signaling. Clusters of genes that are activated in multidrug resistant breast cancer cells identified potential markers of drug tolerance. ME-drivers of the drug tolerance markers were identified in high-throughput cell-based screens with the MicroEnvironment MicroArray (MEMA) platform. BC cells were exposed in parallel to over 1000 unique combinatorial MEs, which were chosen to mimic normal mammary gland, and luminal or basal BC tumor MEs. Single-cell resolution analysis revealed MEs that induce and maintain drug-tolerance markers. Longer-term functional experiments validated that the identified MEs also increased BC cells drug tolerance. Chromatin accessibility profiling with ATAC-sequencing demonstrated that BC cells cultured in those drug-tolerance inducing MEs exhibit chromatin opening in promoter regions of genes linked to epithelial plasticity (e.g. Axl, SNAI2, Vimentin, TWIST1) within 24h of exposure. These results support the concept that specific MEs drive drug-tolerant cellular phenotypes and suggest a novel interventional avenue for preventing acquired therapy resistance. Citation Format: Tiina A Jokela, Dustin Schones, Mark A LaBarge. Microenvironment-induced epigenetic reprogramming imposes drug-tolerant states in breast cancer cells [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-03-04.

Electrospray-based synthesis of fluorescent poly(d,l-lactide-co-glycolide) nanoparticles for the efficient delivery of an anticancer drug and self-monitoring its effect in drug-resistant breast cancer cells

A novel approach used to synthesize antimetabolite-conjugated and intense blue fluorescence-emitting smart polymeric nanoparticles is reported for the efficient delivery of anticancer drugs and self-monitoring their effect in drug-resistant metastatic breast cancer cells.

Strategic Design of Dicer Substrate siRNA to Mitigate the Resistance Mediated by ABCC1 in Doxorubicin-resistant Breast Cancer

The current study involved designing of a small interfering ribonucleic acid-loaded folate functionalized chitosan-coated PLGA nanoparticles to evaluate tumor targeting potential in drug-resistant breast cancer cells. The synthesized conjugate was utilized to develop small interfering ribonucleic acid encapsulated nanoparticles. The developed siRNA nanoparticles were with a particle size of ˂250 nm and could offer protection against serum nucleases. A significant uptake of the folic acid conjugated formulation was noticed, affirming that the nanoparticles selectively targeted the drug-resistant cancer cells. Through the polymerase chain reaction and Western blot, it was evident that ABCC1 expression was significantly reduced (˂95%). The efficiency of small interfering ribonucleic acid with doxorubicin could be evaluated by cytotoxicity assay and it was found that the ABCC1 targeted small interfering ribonucleic acid minimized the resistance of doxorubicin-resistant MCF- 7 cell line to doxorubicin. The main objective in developing this folate conjugated nanoformulation was to enhance the targetability to the cancer cells and to increase the sensitivity of drug-resistant tumors to doxorubicin

Fomes fomentarius and Tricholoma anatolicum (Agaricomycetes) Extracts Exhibit Significant Multiple Drug-Resistant Modulation Activity in Drug-Resistant Breast Cancer Cells.

Multiple drug resistance is one of the main problems that hinder successful cancer chemotherapy. Investigations on the development of effective chemotherapeutic agents and drug resistance inhibitors motivate studies on the effects of natural compounds on drug-resistant cancer cells. For this purpose, aqueous, methanol, and ethanol extracts of Fomes fomentarius and Tricholoma anatolicum were prepared. The extracts were evaluated to assess their anticancer and multiple drug resistance modulation activities. Cytotoxic effects of F. fomentarius and T. anatolicum extracts on paclitaxel and vincristine resistant P-glycoprotein over-expressing MCF-7 cell lines were investigated by cytotoxicity test (XTT). P-glycoprotein reversing ability and MDR modulation effects of the extracts were determined by flow cytometry through Rhodamine 123 exclusion assay. Furthermore, 11 phenolic compounds in the extracts were characterized by HPLC. As a result of the cytotoxicity assay, IC50 values of the extracts for MCF-7/Vinc were between 1.08 and 1.80 mg/mL, and IC50 values for MCF-7/Pac were found between 1.11 and 2.83 mg/mL. Strikingly, methanol extract of F. fomentarius and ethanol extract of T. anatolicum have potential value to become MDR reversing agents for drug-resistant breast cancer cells.

Near-infrared light and magnetic field dual-responsive porous silicon-based nanocarriers to overcome multidrug resistance in breast cancer cells with enhanced efficiency.

The development of drug delivery systems based on external stimuli-responsive nanocarriers is important to overcome multidrug resistance in breast cancer cells. Herein, iron oxide/gold (Fe3O4/Au) nanoparticles were first fabricated via a simple hydrothermal reaction, and subsequently loaded into porous silicon nanoparticles (PSiNPs) via electrostatic interactions to construct PSiNPs@(Fe3O4/Au) nanocomposites. The as-prepared PSiNPs@(Fe3O4/Au) nanocomposites exhibited excellent super-paramagnetism, photothermal effect, and T2-weight magnetic resonance imaging capability. In particular, with the help of a magnetic field, the cellular uptake of PSiNPs@(Fe3O4/Au) nanocomposites was significantly enhanced in drug-resistant breast cancer cells. Moreover, PSiNPs@(Fe3O4/Au) nanocomposites as carriers showed a high loading and NIR light-triggered release of anticancer drugs. Based on the synergistic effect of magnetic field-enhanced cellular uptake and NIR light-triggered intracellular release, the amount of anticancer drug carried by PSiNPs@(Fe3O4/Au) nanocarriers into the nuclei of drug-resistant breast cancer cells sharply increased, accompanied by improved chemo-photothermal therapeutic efficacy. Finally, PSiNPs@(Fe3O4/Au) nanocomposites under the combined conditions of magnetic field attraction and NIR light irradiation also showed improved anticancer drug penetration and accumulation in three-dimensional multicellular spheroids composed of drug-resistant breast cancer cells, leading to a better growth inhibition effect. Overall, the fabricated PSiNPs@(Fe3O4/Au) nanocomposites demonstrated great potential for the therapy of multidrug-resistant breast cancer in future.

Design, synthesis and SAR study of 3rd-generation taxoids bearing 3-CH3, 3-CF3O and 3-CHF2O groups at the C2-benzoate position.

It has been shown that inclusion of CF3O and CHF2O groups to drug candidates often improve their pharmacological properties, especially metabolic stability, membrane permeability and PK profile. Moreover, the unique non-spherical structure of the OCHF2 group can provide interesting and beneficial characteristics. Accordingly, new 3rd-generation taxoids, bearing 3-OCF3 or 3-OCF2H (and 3-CH3 for comparison) at the C2 benzoate moiety, were synthesized and their potencies against drug-sensitive and drug-resistant cancer cell lines examined. In this study, our previous SAR studies on 3rd-generation taxoids were expanded to disclose that CH3, CF3O and CHF2O groups are well tolerated at this position and enhance potency, especially against MDR-cancer cell lines so that these taxoids can virtually overcome MDR. These new taxoids exhibit up to 7 times higher cytotoxicity (IC50) than paclitaxel against drug-sensitive cancer cell lines (MCF7 and LCC6-WT) and 2-3 orders of magnitude higher potency than paclitaxel against drug-resistant ovarian, breast and colon cancer cell lines with MDR-phenotype (NCI/ADR, LCC6-MDR and LDL-1), as well as pancreatic cancer cell line, CFPAC-1. Since it has been shown that a bulky group at this position reduces potency, it is noteworthy that rather bulky CF3O and CHF2O groups are well tolerated. Molecular modeling analysis indicated the favorable van der Waals interactions of CF3O and CHF2O groups in the binding site. It is also worthy of note that new taxoids, bearing a CHF2O group at the C2 benzoate position (1-06 series), exhibited the highest potencies against MDR-cancer cell lines and cancer stem cell (CSC)-enriched cancer cell lines. These new 3rd-generation taxoids are promising candidates for highly potent chemotherapeutic agents, as well as payloads for tumor-targeting drug conjugates such as antibody-drug conjugates (ADCs).

Crystal-Amorphous Core-Shell Structure Synergistically Enabling TiO2 Nanoparticles' Remarkable SERS Sensitivity for Cancer Cell Imaging.

Exploring novel surface-enhanced Raman scattering (SERS) active materials with high detection sensitivity, excellent biocompatibility, low biotoxicity, and good spectral stability is urgently required for efficacious cancer cell diagnosis. Herein, black TiO2 nanoparticles (B-TiO2 NPs) with crystal-amorphous core-shell structure are successfully developed. Remarkable SERS activity is derived from the synergistic effect of the promising crystal-amorphous core-shell structure. Abundant excitons can be generated by high-efficiency exciton transitions in the crystal core, a feature that provides sufficient charge source. Significantly, the novel crystal-amorphous heterojunction enables the efficient exciton separation at the crystal-amorphous interface, which can effectively facilitate charge transfer from the crystal core to the amorphous shell and results in exciton enrichment at the amorphous shell. Kelvin probe force microscopy (KPFM) confirms the Fermi level of the amorphous layer shifting to a relatively low position compared to that of the crystal core, allowing efficient photoinduced charge transfer (PICT) between the amorphous shell and probe molecules. The first-principles density functional theory (DFT) calculations further indicate that the amorphous shell structure possesses a narrow band gap and a relatively high electronic density of state (DOS), which can effectively promote vibration coupling with target molecules. Moreover, MCF-7 drug-resistant (MCF-7/ADR) breast cancer cells can be quickly and accurately diagnosed based on the high-sensitivity B-TiO2-based SERS bioprobe. To the best of our knowledge, this is the first time the crystal-amorphous core-shell heterojunction enhancement of the TiO2-molecule PICT process, which widens the application of semiconductor-based SERS platforms in precision diagnosis and treatment of cancer, has been investigated.

Kinase Chemodiversity from the Arctic: The Breitfussins.

In this work, we demonstrate that the indole-oxazole-pyrrole framework of the breitfussin family of natural products is a promising scaffold for kinase inhibition. Six new halogenated natural products, breitfussin C-H (3 - 8) were isolated and characterized from the Arctic, marine hydrozoan Thuiaria breitfussi. The structures of two of the new natural products were also confirmed by total synthesis. Two of the breitfussins (3 and 4) were found to selectively inhibit the survival of several cancer cell lines, with the lowest IC50 value of 340 nM measured against the drug-resistant triple negative breast cancer cell line MDA-MB-468, while leaving the majority of the tested cell lines not or significantly less affected. When tested against panels of protein kinases, 3 gave IC50 and Kd values as low as 200 and 390 nM against the PIM1 and DRAK1 kinases, respectively. The activity was confirmed to be mediated through ATP competitive binding in the ATP binding pocket of the kinases. Furthermore, evaluation of potential off-target and toxicological effects, as well as relevant in vitro ADME parameters for 3 revealed that the breitfussin scaffold holds promise for the development of selective kinase inhibitors.

Functional extracellular vesicles engineered with lipid-grafted hyaluronic acid effectively reverse cancer drug resistance

Multidrug resistance (MDR) is a key issue accounting for ineffectiveness of cancer chemotherapy. Numerous multifunctional nanocarriers have been developed to increase drug delivery efficacy and inhibit drug efflux for overcoming cancer drug resistance. However, limited success has been achieved in clinic because of nanocarriers' complicated multi-step fabrication procedures and their undesired side toxicity as well as potential immunogenicity. Here, hyaluronic acid (HA) functionalized extracellular vesicles (EVs) are generated as natural vehicles to efficiently deliver doxorubicin (DOX) and reverse MDR. The EVs isolated from noncancerous HEK293T cells (hEVs) reduce P-glycoprotein (P-gp) expression in drug resistant MCF7/ADR cells. To acquire tumor-targeting capability, hEVs are modified with lipidomimetic chains-grafted HA (lipHA) by a simple incubation. Owing to CD44-mediated cancer-specific targeting and P-gp suppressive capability, the HA-functionalized hEVs (lipHA-hEVs) remarkably promote the intracellular DOX accumulation in drug resistant breast cancer cells. In preclinical MDR tumor models, lipHA-hEVs deeply penetrate into tumor tissue and effectively transport DOX into tumor local, while eliminating DOX's systemic toxicity. Importantly, DOX@lipHA-hEVs inhibited MDR tumor growth by 89% and extend animal survival time by approximately 50%. Thus, our engineered tumor-targeting hEVs are promising natural carriers for overcoming cancer MDR.

MicroRNA-16 sensitizes drug-resistant breast cancer cells to Adriamycin by targeting Wip1 and Bcl-2.

Clinical evidence indicates that drug resistance is a major obstacle in the treatment of breast cancer (BC). Drug resistance results in the disease being uncontrollable, and leads to high mortality rates. The aim of the present study was to investigate the chemosensitizing effect of microRNA (miR)-16 on Adriamycin (ADM)-resistant BC cells and the associated mechanisms. BC tumors from 40 patients were collected and reverse transcription-quantitative PCR was used to examine the expression of miR-16. ADM-sensitive (MCF-7/S) and -resistant (MCF-7/A) BC cell lines were used to determine the expression of miR-16 prior to and following transfection with miR-16 mimics or inhibitor. The effects of increased and decreased miR-16 expression on the chemosensitivity of BC cells to ADM was analyzed using MTT, colony survival and flow cytometry assays. miR-16 was found to regulate wild-type p53-induced phosphatase 1 (Wip1) and Bcl-2 expression, as confirmed by western blotting, immunofluorescence staining and luciferase reporter assays. miR-16 expression in drug-resistant tumor tissues and cells was decreased, compared with that the drug-sensitive equivalents. Overexpression of miR-16 in MCF-7/A was associated with a sharp downregulation of Wip1 and Bcl-2 expression, leading to increased ADM-induced cell apoptosis and sensitization of MCF-7/A cells to ADM treatment. Taken together, the results demonstrate that miR-16 may serve as an effective chemosensitizing target to enhance the effects of chemotherapy in drug-resistant BC cells with high Wip1 and Bcl-2 expression. This provides a novel approach to improving the chemotherapeutic efficacy in drug-resistant BC via regulation of miRs.

Regulation of PERK expression by FOXO3: a vulnerability of drug-resistant cancer cells

The major impediment to effective cancer therapy has been the development of drug resistance. The tumour suppressive transcription factor FOXO3 promotes cell cycle arrest, senescence and cell death, and mediates the cytotoxic and cytostatic functions of cancer therapeutics. In consequence, FOXO3 is often downregulated as an adaptive response in cancer and particularly in chemotherapeutic drug-resistant cells. Consistently, we find that FOXO3 expression is attenuated in the drug-resistant MCF-7-EpiR and MCF-7-TaxR compared to the parental MCF-7 breast cancer cells. Using ChIP, short-interfering RNA (siRNA) knockdown, and overexpression assays as well as Foxo1/3/4−/− MEFs, we establish the endoplasmic reticulum (ER)-stress defence modulator PERK (eIF2AK3) as a direct downstream transcriptional target of FOXO3. In agreement, there is also a positive correlation between FOXO3 and PERK expression at the protein and RNA levels in breast cancer patient samples. We uncover that PERK expression is downregulated but its activity constitutively elevated in the drug-resistant cells. With this in mind, we exploit this adaptive response of low FOXO3 and PERK expression, and high PERK activity in drug-resistant breast cancer cells and show that these drug-resistant cells are specifically sensitive to PERK inhibition. In support of this finding, we show that ectopic overexpression of FOXO3 can reduce the sensitivity of the resistant cells to the PERK inhibitor GSK2606414, while the Foxo1/3/4−/− MEFs expressing lower levels of PERK are more sensitive to PERK inhibition compared to wild-type MEFs. PERK inhibitor-titration and -time course experiments showed that the drug-resistant cells, which express lower expression and higher activity levels of PERK, are more sensitive to the increasing concentrations of PERK inhibitor compared to parental MCF-7 cells. Our present work thus reveals a chemotherapeutic drug-resistant cancer cell vulnerability in PERK and suggests PERK as a potential target for cancer therapy, specifically in the context of drug-resistant cancers.

Silencing CDR1as enhances the sensitivity of breast cancer cells to drug resistance by acting as a miR-7 sponge to down-regulate REGγ.

In our study, we aimed to investigate the role of CDR1as during competitive inhibition of miR‐7 in the regulation of cisplatin chemosensitivity in breast cancer via regulating REGγ. RT‐qPCR was applied to detect the expression of CDR1as and miR‐7 in breast cancer tissues, breast cancer cell lines and corresponding drug‐resistant cell lines. The correlation between CDR1as and miR‐7 and between miR‐7 and REGγ was evaluated. MCF‐7‐R and MDA‐MB‐231‐R cells were selected followed by transfection of a series of mimics, inhibitors or siRNA. The effect of CDR1as on the half maximal inhibitor concentration (IC50), cisplatin sensitivity and cell apoptosis was also analysed. Furthermore, a subcutaneous xenograft nude mouse model was established to further confirm the effect of CDR1as on the chemosensitivity of breast cancer to cisplatin in vivo. Immunohistochemical staining was conducted to test the Ki‐67 expression in nude mice. A positive correlation was found between the drug resistance and CDR1as expression in breast cancer. CDR1as could increase the resistance of breast cancer cells to cisplatin. miR‐7 expression was low, while REGγ was highly expressed in MCF‐7‐R and MDA‐MB‐231‐R cells. CDR1as competitively inhibited miR‐7 and up‐regulated REGγ. Overexpression of miR‐7 could reverse the enhanced sensitivity of silenced CDR1as to drug‐resistant breast cancer cells. Additionally, in vivo experiments demonstrated that CDR1as mediated breast cancer occurrence and its sensitivity to cisplatin. Silencing CDR1as decreased Ki‐67 expression. Silencing CDR1as may inhibit the expression of REGγ by removing the competitive inhibitory effect on miR‐7 and thus enhancing the sensitivity of drug‐resistant breast cancer cells.

Resveratrol chemosensitizes adriamycin-resistant breast cancer cells by modulating miR-122-5p.

Breast cancer is one of the major malignancies threatening women's health worldwide, and chemotherapy tolerance has become a severe limitation of clinical treatment. Recent findings have revealed that resveratrol, as a dietary agent with antitumour activity, could prevent cancer progression by regulating microRNAs (miRNAs). Additionally, dysregulated miRNAs have been found to contribute significantly to chemoresistance by an increasing number of studies. In this study, experiments were designed to study the functional role of resveratrol in MCF-7 cells (low-invasive breast cancer) in chemosensitivity to adriamycin and to determine the targeted miRNAs of resveratrol and their key target proteins linked to cell activity. We demonstrated that in resveratrol-induced chemosensitivity, cell cycle and apoptosis were arrested in adriamycin-resistant breast cancer cells after modulation of the critical suppresser, miR-122-5p. Further miRNA modulation with miR-122-5p mimics or miR-122-5p inhibitors indicated a major effect of miR-122-5p on the regulation of key antiapoptotic proteins (B-cell lymphoma 2 [Bcl-2]) and cyclin-dependent kinases (CDK2, CDK4, and CDK6) in drug-resistant breast cancer cells in response to resveratrol. In conclusion, our results indicate that resveratrol acts as a potential inducer to enhance the chemosensitivity of breast cancer and also suggest that miR-122-5p is involved in the pathway of cell-cycle arrest by targeting Bcl-2 and CDKs.

Knockdown of lncRNA-HOTAIR downregulates the drug-resistance of breast cancer cells to doxorubicin via the PI3K/AKT/mTOR signaling pathway.

The resistance to chemotherapeutic drugs is a critical feature of breast cancer recurrence and metastasis. Long non-coding RNAs (LncRNAs) serve key roles in tumor drug resistance. LncRNA-HOX transcript antisense RNA (HOTAIR) has been reported to be overexpressed in certain types of cancer and may be closely associated with tumor resistance. The current study aimed to investigate the role of lncRNA-HOTAIR in the regulation of breast cancer resistance to doxorubicin (DOX). A breast cancer cell line (MCF-7) and DOX-resistant breast cancer cell line (DOXR-MCF-7) were utilized in the current study. DOXR-MCF-7 cells were transfected with lncRNA-HOTAIR small interfering RNA (siRNA) and control siRNA. Subsequently, MTT and colony formation assays were performed to assess cell proliferation. Cell apoptosis was also evaluated via flow cytometry. In addition, western blotting and reverse transcription-quantitative polymerase chain reaction were performed to detect the expression of caspase-3, B-cell lymphoma 2, Bcl-2-associated X protein, phosphoinositide 3-kinase (PI3K), protein kinase B (AKT) and mechanistic target of rapamycin (mTOR), and the phosphorylation of PI3K, AKT, and mTOR. The data indicated that lncRNA-HOTAIR silencing decreased cell proliferation and increased apoptosis in MCF-7 and DOXR MCF-7 cells. Furthermore, lncRNA-HOTAIR silencing significantly decreased the phosphorylation of PI3K, AKT and mTOR, indicating that the knockdown of lncRNA-HOTAIR effectively attenuates the resistance of breast cancer cells to DOX by inhibiting the PI3K/AKT/mTOR pathway. In summary, the present study indicated that the knockdown of lncRNA-HOTAIR weakened the resistance of breast cancer cells to DOX via PI3K/AKT/mTOR signaling, suggesting that lncRNA-HOTAIR may be a novel intervention target to reverse DOX-resistance in breast cancer.

Rack1 mediates tyrosine phosphorylation of Anxa2 by Src and promotes invasion and metastasis in drug-resistant breast cancer cells

BackgroundAcquirement of resistance is always associated with a highly aggressive phenotype of tumor cells. Recent studies have revealed that Annexin A2 (Anxa2) is a key protein that links drug resistance and cancer metastasis. A high level of Anxa2 in cancer tissues is correlated to a highly aggressive phenotype. Increased Anxa2 expression appears to be specific in many drug-resistant cancer cells. The functional activity of Anxa2 is regulated by tyrosine phosphorylation at the Tyr23 site. Nevertheless, the accurate molecular mechanisms underlying the regulation of Anxa2 tyrosine phosphorylation and whether phosphorylation is necessary for the enhanced invasive phenotype of drug-resistant cells remain unknown.MethodsSmall interfering RNAs, small molecule inhibitors, overexpression, loss of function or gain of function, rescue experiments, Western blot, wound healing assays, transwell assays, and in vivo metastasis mice models were used to investigate the functional effects of Rack1 and Src on the tyrosine phosphorylation of Anxa2 and the invasion and metastatic potential of drug-resistant breast cancer cells. The interaction among Rack1, Src, and Anxa2 in drug-resistant cells was verified by co-immunoprecipitation assay.ResultsWe demonstrated that Anxa2 Tyr23 phosphorylation is necessary for multidrug-resistant breast cancer invasion and metastasis. Rack1 is required for the invasive and metastatic potential of drug-resistant breast cancer cells through modulating Anxa2 phosphorylation. We provided evidence that Rack1 acts as a signal hub and mediates the interaction between Src and Anxa2, thereby facilitating Anxa2 phosphorylation by Src kinase.ConclusionsOur findings suggest a convergence point role of Rack1/Src/Anxa2 complex in the crosstalk between drug resistance and cancer aggressiveness. The interaction between Anxa2 and Rack1/Src is responsible for the association between drug resistance and invasive/metastatic potential in breast cancer cells. Thus, our findings provide novel insights on the mechanism underlying the functional linkage between drug resistance and cancer aggressiveness.