Paclitaxel-resistant Breast Cancer Research Articles

Protein Phosphatase 1H, Cyclin-Dependent Kinase Inhibitor p27, and Cyclin-Dependent Kinase 2 in Paclitaxel Resistance for Triple Negative Breast Cancers.

PurposePaclitaxel is a cytotoxic chemotherapy commonly used in patients with triple negative breast cancer (TNBC); however, the resistance to paclitaxel is a cause of poor response in the patients. The aim of this study was to examine the role of protein phosphatase 1H (PPM1H) in paclitaxel resistance in breast cancer patients.MethodsTo investigate the function of PPM1H in paclitaxel treatment, we conducted in vitro assays and molecular experiments using a stable cell line (MDA-MB-231) in which PPM1H is overexpressed. We also performed molecular analyses on patient tissue samples. Molecular expression related to PPM1H in breast cancer patients was analyzed using TCGA data.ResultsWe investigated whether PPM1H was associated with paclitaxel resistance in breast cancer. PPM1H expression was upregulated in breast cancer cells treated with paclitaxel. We also observed that overexpression of PPM1H in breast cancer cells resulted in increased sensitivity to paclitaxel in vitro. Additionally, paclitaxel treatment induced dephosphorylation of cyclin-dependent kinase (CDK) inhibitor p27 (p27), which was more evident in PPM1H-overexpressing cells. To understand how upregulation of PPM1H increases paclitaxel sensitivity, we determined the levels of p27, phospho-p27, and CDK2, since CDK2 exerts antagonistic effects against PPM1H on p27 phosphorylation. The patient-derived xenograft (PDX) tumors that did not respond to paclitaxel showed increased levels of CDK2 and phospho-p27 and decreased levels of total p27 compared to the other breast tumor tissues. The use of dinaciclib, a selective CDK inhibitor, significantly inhibited tumor growth in the PDX model.ConclusionCDK2 kinase activity was significantly upregulated in basal breast cancer tumors and was negatively correlated with p27 protein levels in the TCGA breast cancer dataset, suggesting that targeting CDK2 may be an effective treatment strategy for TNBC patients.

EPAS1 targeting by miR-152-3p in Paclitaxel-resistant Breast Cancer.

Background: Paclitaxel plays a pivotal role in the chemotherapy of breast cancer, but resistance to this drug is an important obstacle in the treatment. It is reported that microRNA-152-3p (miR-152-3p) is involved in tamoxifen resistance in breast cancer, but whether it is involved in paclitaxel resistance in breast cancer remains unknown.Materials and methods: We examined the expression of miR-152-3p in breast cancer tissues and cells by qRT-PCR. After transfecting paclitaxel-resistant MCF-7/TAX cells with miR-152-3p mimics, we analyzed the function of miR-152-3p in these cells by MTT assay and flow cytometry. We screened the target gene, endothelial PAS domain-containing protein 1 (EPAS1), using bioinformatics analysis and verified it with the dual luciferase reporter gene experiment. The relationship between EPAS1 and miR-152-3p and their roles in paclitaxel resistance of breast cancer were further investigated using RNA interference and transfection techniques.Results: The expression of miR-152-3p in normal breast tissues and cells was markedly higher than that in breast cancer. Overexpression of miR-152-3p decreased the survival rate and increased the apoptosis rate and sensitivity of MCF-7/TAX cells to paclitaxel. We confirmed that EPAS1 is the target of miR-152-3p and is negatively regulated by this miRNA. Moreover, transfection with EPAS1 siRNA enhanced the susceptibility and apoptosis rate of MCF-7/TAX cells to paclitaxel. Co-transfection of miR-152-3p mimics and EPAS1 increased paclitaxel sensitivity and apoptosis induced by the drug.Conclusion: miR-152-3p inhibits the survival of MCF-7/TAX cells and promotes their apoptosis by targeting the expression of EPAS1, thereby, enhancing the sensitivity of these breast cancer cells to paclitaxel.

Chemoresistance was correlated with elevated expression and activity of indoleamine 2,3-dioxygenase in breast cancer.

Indoleamine 2,3-dioxygenase (IDO) catalyses degradation of the essential amino acid tryptophan leading to the production of immunosuppressive kynurenine and tryptophan exhausting. IDO expression and activity contribute to aggressive tumor growth, inferior therapeutic gain and poor prognosis. The aim of this study was to explore the association between chemoresistance and IDO expression, activity in breast cancer METHODS: Immunohistochemistry was applied for evaluating IDO expression in biopsy tissues. Serum IDO activity was examined via High-performance liquid chromatography (HPLC). Western blots (WB), HPLC and Real-time PCR (RT-PCR) were used to analyze IDO protein, IDO enzyme activity and IDO gene expression in original and paclitaxel-resistant cells respectively. Logistic regression and survival analysis were applied to explore the association between chemoresistance and IDO expression, activity in breast cancer. IDO expression in tumor tissues was associated with serum IDO activity (P = 0.004). Both IDO expression in tumor and serum activity were associated with clinical tumor stage, node stage and estrogen receptor (ER) status (all P < 0.05); clinical response and pathologic complete response (pCR) to NAC were both related to IDO expression and activity prior NAC (all P < 0.05). Multivariate analysis showed IDO activity before NAC was the only independent factor affected pCR (P = 0.032). ROC curves showed that the IDO expression and activity had discriminative ability for predicting the clinical response and pCR. In the prognostic analysis, patients with high IDO expression had significantly impaired overall survival (5year survival rate: 53.57% vs 80.00%) and progression-free survival (5year survival rate: 46.43% vs 72.00%, P = 0.031 and P = 0.046). In vitro, significantly increased IDO protein, IDO mRNA expression and IDO enzyme activity in paclitaxel-resistant cells were demonstrated in comparing of sensitive cells. IDO expression and activity associated with advanced breast cancer, poor response to neoadjuvant chemotherapy and prognosis. IDO expression and activity were significantly increased in paclitaxel-resistant breast cancer cells.

Antitumor Activity of Abnormal Cannabidiol and Its Analog O-1602 in Taxol-Resistant Preclinical Models of Breast Cancer.

Cannabinoids exhibit anti-inflammatory and antitumorigenic properties. Contrary to most cannabinoids present in the Cannabis plant, some, such as O-1602 and abnormal cannabidiol, have no or only little affinity to the CB1 or CB2 cannabinoid receptors and instead exert their effects through other receptors. Here, we investigated whether the synthetic regioisomers of cannabidiol, abnormal cannabidiol, and a closely related compound, O-1602, display antitumorigenic effects in cellular models of breast cancer and whether it could reduce tumorigenesis in vivo. Several studies have shown the effects of cannabinoids on chemotherapy-sensitive breast cancer cell lines, but less is known about the antitumorigenic effects of cannabinoids in chemotherapy-resistant cell lines. Paclitaxel-resistant MDA-MB-231 and MCF-7 breast cancer cell lines were used to study the effect of O-1602 and abnormal cannabidiol on viability, apoptosis, and migration. The effects of O-1602 and abnormal cannabidiol on cell viability were completely blocked by the combination of GPR55 and GPR18-specific siRNAs. Both O-1602 and abnormal cannabidiol decreased viability in paclitaxel-resistant breast cancer cells in a concentration-dependent manner through induction of apoptosis. The effect of these cannabinoids on tumor growth in vivo was studied in a zebrafish xenograft model. In this model, treatment with O-1602 and abnormal cannabidiol (2 µM) significantly reduced tumor growth. Our results suggest that atypical cannabinoids, like O-1602 and abnormal cannabidiol, exert antitumorigenic effects on paclitaxel-resistant breast cancer cells. Due to their lack of central sedation and psychoactive effects, these atypical cannabinoids could represent new leads for the development of additional anticancer treatments when resistance to conventional chemotherapy occurs during the treatment of breast and possibly other cancers.

Long noncoding RNA CASC2 promotes paclitaxel resistance in breast cancer through regulation of miR-18a-5p/CDK19.

Breast cancer is one of the most prevalent cancers in women. Chemoresistance is a major obstacle for the treatment of breast cancer. We investigated the role of long noncoding RNA (lncRNA) cancer susceptibility candidate 2 (CASC2) in paclitaxel (PTX) resistance in breast cancer. CASC2 expression was increased in PTX-resistant clinical samples and cell lines. PTX induced CASC2 expression in a concentration-dependent manner. Downregulation of CASC2 increased PTX toxicity and decreased IC50 value, while upregulation of CASC2 decreased PTX toxicity and increased IC50 value in MCF-7/PTX and MDA-MB-231/PTX cells. Moreover, downregulation of CASC2 decreased tumor growth in xenograft mice implanted with MCF-7/PTX cells. miR-18a-5p possessed a putative binding site in 3'-UTR of CASC2 and cyclin-dependent kinase 19 (CDK19). In PTX-resistant breast cancer cells, miR-18a-5p expression was decreased. CASC2 and miR-18a-5p could negatively regulate the expression of each other. CDK19 expression could be negatively regulated by miR-18a-5p, but positively regulated by CASC2. miR-18a-5p mimics or downregulation of CDK19 decreased tumor growth in xenograft mice implanted with MCF-7/PTX cells. In summary, we identified that CASC2 activated PTX resistance in breast cancer through regulation of miR-18a-5p/CDK19. We highlight the importance of CASC2/miR-18a-5p/CDK19 axis in the chemoresistance of breast cancer and provide potential targets for the improving chemotherapy of breast cancer.

Epigenetic inhibition of the tumor suppressor ARHI by light at night-induced circadian melatonin disruption mediates STAT3-driven paclitaxel resistance in breast cancer.

Disruption of circadian time structure and suppression of circadian nocturnal melatonin (MLT) production by exposure to dim light at night (dLAN), as occurs with night shift work and/or disturbed sleep-wake cycles, is associated with a significantly increased risk of breast cancer and resistance to tamoxifen and doxorubicin. Melatonin inhibition of human breast cancer chemoresistance involves mechanisms including suppression of tumor metabolism and inhibition of kinases and transcription factors which are often activated in drug-resistant breast cancer. Signal transducer and activator of transcription 3 (STAT3), frequently overexpressed and activated in paclitaxel (PTX)-resistant breast cancer, promotes the expression of DNA methyltransferase one (DNMT1) to epigenetically suppress the transcription of tumor suppressor Aplasia Ras homolog one (ARHI) which can sequester STAT3 in the cytoplasm to block PTX resistance. We demonstrate that breast tumor xenografts in rats exposed to dLAN and circadian MLT disrupted express elevated levels of phosphorylated and acetylated STAT3, increased DNMT1, but reduced sirtuin 1 (SIRT1) and ARHI. Furthermore, MLT and/or SIRT1 administration blocked/reversed interleukin 6 (IL-6)-induced acetylation of STAT3 and its methylation of ARH1 to increase ARH1 mRNA expression in MCF-7 breast cancer cells. Finally, analyses of the I-SPY 1 trial demonstrate that elevated MT1 receptor expression is significantly correlated with pathologic complete response following neo-adjuvant therapy in breast cancer patients. This is the first study to demonstrate circadian disruption of MLT by dLAN driving intrinsic resistance to PTX via epigenetic mechanisms increasing STAT3 expression and that MLT administration can reestablish sensitivity of breast tumors to PTX and drive tumor regression.

Silencing RRM1 gene reverses paclitaxel resistance in human breast cancer cell line MCF- 7/R by inducing cell apoptosis

To investigate the effects of ribonucleotide reductase catalytic subunit M1 (RRM1) gene silencing on drug resistance of human breast cancer cell line MCF-7/R. We established a paclitaxel-resistant breast cancer MCF-7 cell line (MCF-7/R) by exposing the cells to high-concentration paclitaxel in a short time. Small interfering RNAs (siRNAs) targeting RRM1 were designed to silence RRM1 expression in human breast cancer MCF-7/R cells. MTT assay was used to detect the IC50 values and the sensitivity to paclitaxel in the cells with or without siRNA transfection. The changes in the proliferative activity of MCF7 and MCF-7/R cells following RRM1 gene silencing were evaluated using EdU assay. Flow cytometry was used to analyze the cell apoptosis and cell cycle changes. We assessed the effect of RRM1 gene silencing and paclitaxel on the tumor growth in a nude mouse model bearing subcutaneous xenografts with or without siRNA transfection. We detected significantly higher expressions of RRM1 at both the mRNA and protein levels in the drug-resistant MCF- 7/R cells than in the parental MCF-7 cells (P &lt; 0.01). Transfection with the specific siRNAs significantly reduced the expression of RRM1 in MCF-7/R cells (P &lt; 0.05), which showed a significantly lower IC50 value of paclitaxel than the cells transfected with the negative control siRNA (P &lt; 0.05). RRM1 silencing significantly inhibited the proliferation (P &lt; 0.01) and enhanced the apoptosis-inducing effect of paclitaxel in MCF-7/R cells (P &lt; 0.001); RRM1 silencing also resulted in obviously reduced Akt phosphorylation, suppressed Bcl-2 expression and promoted the expression of p53 protein in MCF-7/R cells. In the tumor-bearing nude mice, the volume of subcutaneously transplanted tumors was significantly smaller in MCF-7/R/siRNA+ PTX group than in the other groups (P &lt; 0.001). RRM1 gene silencing can reverse paclitaxel resistance in human breast cancer cell line MCF-7/R by promoting cell apoptosis.

Penfluridol overcomes paclitaxel resistance in metastatic breast cancer

Paclitaxel is a first line chemotherapeutic agent for the patients with metastatic breast cancer. But inherited or acquired resistance to paclitaxel leads to poor response rates in a majority of these patients. To identify mechanisms of paclitaxel resistance, we developed paclitaxel resistant breast cancer cell lines, MCF-7 and 4T1 by continuous exposure to paclitaxel for several months. Western blot analysis showed increased expression of HER2 and β-catenin pathway in resistant cell lines as compared to parent cells. Hence, we hypothesized that HER2/β-catenin mediates paclitaxel resistance in breast cancer and suppression of HER2/β-catenin signaling could overcome paclitaxel resistance. Our data showed that penfluridol (PFL) treatment significantly reduced the survival of paclitaxel-resistant cells. Western blot analysis revealed that PFL treatment suppressed HER2, as well as, β-catenin pathway. In vivo data confirmed that PFL significantly potentiated tumor growth suppressive effects of paclitaxel in an orthotropic breast cancer model. In addition, tumors from paclitaxel and PFL-treated mice showed reduced HER2 and β-catenin expression, along with increased apoptosis. Taken together our results demonstrate a novel role of HER2/β-catenin in paclitaxel resistance and open up new avenues for application of PFL as a therapeutic option for overcoming paclitaxel resistance.

Plumbagin Increases Paclitaxel-Induced Cell Death and Overcomes Paclitaxel Resistance in Breast Cancer Cells through ERK-Mediated Apoptosis Induction.

ERK is a component of mitogen-activated protein kinases that controls a range of cellular processes including cell proliferation and survival. The upregulation of ERK has been associated with apoptosis inhibition in response to various stimuli including chemotherapeutic agents. Research has suggested that the upregulation of ERK signaling by the anticancer agent paclitaxel leads to acquired resistance of cells to this compound. The presented research focused on determining the role of plumbagin, a naturally derived naphthoquinone, in the sensitization of breast cancer cells to paclitaxel-induced cell death and the involvement of ERK signaling in this process. The results of the study indicated that plumbagin increases the sensitivity of breast cancer cells to paclitaxel. Moreover, a synergistic effect between plumbagin and paclitaxel was observed. Plumbagin was shown to decrease levels of phosphorylated ERK in breast cancer cells and abrogated paclitaxel-induced ERK phosphorylation. The role of ERK in plumbagin-mediated sensitization of breast cancer cells to paclitaxel was shown through the enhancement of the synergistic effect between compounds in cells with decreased ERK expression. Furthermore, plumbagin reduced p-ERK levels in paclitaxel-resistant breast cancer cells and resensitized paclitaxel-resistant cells to this compound. These results imply that plumbagin inhibits ERK activation in breast cancer cells, which plays a role in the sensitization of cells to paclitaxel-induced cell death.

Aglycone Polyether Nanchangmycin and Its Homologues Exhibit Apoptotic and Antiproliferative Activities against Cancer Stem Cells.

The potential of the polyether salinomycin as an inhibitory agent against cancer stem cells has attracted interest in this family of compounds. In this study, we found that the aglycone polyether nanchangmycin and its homologues show promising activities against breast cancer stem cells as well as 38 other different types of cancer cells by in vitro assays. We found that aglycone polyethers caused elevations in calcium levels, an accumulation of reactive oxygen species and mitochondrial inner membrane permeability to H+ and K+, resulting in the release of cytochrome c and apoptosis-inducing factor and the triggering of caspase-dependent apoptosis. Our analyses also indicate that aglycone polyethers are potent Wnt/β-catenin signaling inhibitors, blocking the Wnt pathway and resulting in reduced cell survival. Notably, the key autophagy-related proteins LC3A/B were also activated by aglycone polyether treatment. Furthermore, nanchangmycin showed inhibitory effects toward somatic tumors developed from MCF-7 paclitaxel-resistant breast cancer cells injected into BALB/c mice. Our study not only provides promising candidates for therapy against cancer stem cells but also provides the groundwork for identifying stronger therapeutic agents among the natural polyether compounds.

Downregulation of miR‑200c‑3p contributes to the resistance of breast cancer cells to paclitaxel by targeting SOX2.

Acquisition of resistance to paclitaxel is a major obstacle to successful treatment of breast cancer patients, but the molecular mechanisms underlying the development of drug resistance remain largely unclear. The aim of the present study was to investigate the role and mechanism of action of miR‑200c‑3p in the resistance of breast cancer to paclitaxel. It was observed that miR‑200c‑3p expression, as determined by reverse transcription‑quantitative polymerase chain reaction analysis, was significantly downregulated in paclitaxel‑resistant MCF‑7/Tax cells compared with parental MCF‑7 cells. Overexpression of miR‑200c‑3p increased the chemosensitivity to paclitaxel and enhanced apoptosis in MCF‑7/Tax cells, whereas the downregulation of miR‑200c‑3p exerted the opposite effect. In addition, upregulation of miR‑200c‑3p in MCF‑7/Tax cells suppressed the expression of sex‑determining region Y‑box 2 (SOX2) at the mRNA and protein levels. Dual‑luciferase reporter assay demonstrated that SOX2 is a target of miR‑200c‑3p in MCF‑7/Tax cells. Moreover, knockdown of SOX2 expression increased chemosensitivity to paclitaxel and upregulated miR‑200c‑3p expression in MCF‑7/Tax cells. Taken together, the results of the present study indicated that miR‑200c‑3p plays a key role in the development of paclitaxel resistance in breast cancer, possibly partially through regulating SOX2 expression, suggesting that the miR‑200c‑3p‑SOX2 loop may serve as a potential target for the reversal of paclitaxel resistance in breast cancer.

PIM2-mediated phosphorylation of hexokinase 2 is critical for tumor growth and paclitaxel resistance in breast cancer

Hexokinase-II (HK2) is a key enzyme involved in glycolysis, which is required for breast cancer progression. However, the underlying post-translational mechanisms of HK2 activity are poorly understood. Here, we showed that Proviral Insertion in Murine Lymphomas 2 (PIM2) directly bound to HK2 and phosphorylated HK2 on Thr473. Biochemical analyses demonstrated that phosphorylated HK2 Thr473 promoted its protein stability through the chaperone-mediated autophagy (CMA) pathway, and the levels of PIM2 and pThr473-HK2 proteins were positively correlated with each other in human breast cancer. Furthermore, phosphorylation of HK2 on Thr473 increased HK2 enzyme activity and glycolysis, and enhanced glucose starvation-induced autophagy. As a result, phosphorylated HK2 Thr473 promoted breast cancer cell growth in vitro and in vivo. Interestingly, PIM2 kinase inhibitor SMI-4a could abrogate the effects of phosphorylated HK2 Thr473 on paclitaxel resistance in vitro and in vivo. Taken together, our findings indicated that PIM2 was a novel regulator of HK2, and suggested a new strategy to treat breast cancer.

NT21MP negatively regulates paclitaxel-resistant cells by targeting miR‑155‑3p and miR‑155-5p via the CXCR4 pathway in breast cancer.

Evidence has shown that microRNAs (miRNAs) are vital in cell growth, migration, and invasion by inhibiting their target genes. A previous study demonstrated that miRNA (miR)-155-3p and miR-155-5p exerted opposite effects on cell proliferation, apoptosis, migration and invasion in breast cancer cell lines. An miRNA microarray was used to show that miR-155-3p was downregulated whereas miR-155-5p was upregulated in paclitaxel-resistant (PR) cells compared with parental breast cancer cells. However, the role of miR-155 in breast cancer cell invasion and metastasis remains to be elucidated. A 21-residue peptide derived from the viral macrophage inflammatory protein II (NT21MP), competes with the ligand of CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α, inducing cell apoptosis in breast cancer. The present study aimed to identify the underlying mechanism of action of miR-155-3p/5p and NT21MP in PR breast cancer cells. Quantitative polymerase chain reaction, western blotting, wound-healing, cell cycle and apoptosis assays, and Cell Counting kit-8 assay were used to achieve this goal. The combined overexpression of miR-155-3p with NT21MP decreased the migration and invasion ability and increased the number of apoptotic and arrested cells in the G0/G1 phase transition in vitro. The knockdown of miR-155-5p combined with NT21MP had a similar effect on PR breast cancer cells. Furthermore, the ectopic expression of their target gene myeloid differentiation primary response gene 88 (MYD88) or tumor protein 53-induced nuclear protein 1 (TP53INP1) combined with NT21MP enhanced the sensitivity of the breast cancer cells to paclitaxel. Taken together, these findings suggested that miR-155-3p/5p and their target genes MYD88 and TP53INP1 may serve as novel biomarkers for NT21MP therapy through the CXCR4 pathway for improving sensitivity to paclitaxel in breast cancer.

Long non-coding RNA FTH1P3 activates paclitaxel resistance in breast cancer through miR-206/ABCB1.

Emerging evidence has indicated the important function of long non‐coding RNAs (lncRNAs) in tumour chemotherapy resistance. However, the underlying mechanism is still ambiguous. In this study, we investigate the physiopathologic role of lncRNA ferritin heavy chain 1 pseudogene 3 (FTH1P3) on the paclitaxel (PTX) resistance in breast cancer. Results showed that lncRNA FTH1P3 was up‐regulated in paclitaxel‐resistant breast cancer tissue and cells (MCF‐7/PTX and MDA‐MB‐231/PTX cells) compared with paclitaxel‐sensitive tissue and parental cell lines (MCF‐7, MDA‐MB‐231). Gain‐ and loss‐of‐function experiments revealed that FTH1P3 silencing decreased the 50% inhibitory concentration (IC50) value of paclitaxel and induced cell cycle arrest at G2/M phase, while FTH1P3‐enhanced expression exerted the opposite effects. In vivo, xenograft mice assay showed that FTH1P3 silencing suppressed the tumour growth of paclitaxel‐resistant breast cancer cells and ABCB1 protein expression. Bioinformatics tools and luciferase reporter assay validated that FTH1P3 promoted ABCB1 protein expression through targeting miR‐206, acting as a miRNA “sponge.” In summary, our results reveal the potential regulatory mechanism of FTH1P3 on breast cancer paclitaxel resistance through miR‐206/ABCB1, providing a novel insight for the breast cancer chemoresistance.

Compound A attenuates toll-like receptor 4-mediated paclitaxel resistance in breast cancer and melanoma through suppression of IL-8

BackgroundPaclitaxel (PTX) is a potent anti-cancer drug commonly used for the treatment of advanced breast cancer (BCA) and melanoma. Toll-like receptor 4 (TLR4) promotes the production of pro-inflammatory cytokines associated with cancer chemoresistance. This study aims to explore the effect of TLR4 in PTX resistance in triple-negative BCA and advanced melanoma and the effect of compound A (CpdA) to attenuate this resistance.MethodsBCA and melanoma cell lines were checked for the response to PTX by cytotoxic assay. The response to PTX of TLR4-transient knockdown cells by siRNA transfection was evaluated compared to the control cells. Levels of pro-inflammatory cytokines, IL-6 and IL-8, and anti-apoptotic protein, XIAP were measured by real-time PCR whereas the secreted IL-8 was quantitated by ELISA in TLR4-transient knockdown cancer cells with or without CpdA treatment. The apoptotic cells after adding PTX alone or in combination with CpdA were detected by caspase-3/7 assay.ResultsPTX could markedly induce TLR4 expression in both MDA-MB-231 BCA and MDA-MB-435 melanoma cell lines having a basal level of TLR4 whereas no significant induction in TLR4-transient knockdown cells occurred. The siTLR4-treated BCA cells revealed more dead cells after PTX treatment than that of mock control cells. IL-6, IL-8 and XIAP showed increased expressions in PTX-treated cells and this over-production effect was inhibited in TLR4-transient knockdown cells. Apoptotic cells were detected higher when PTX and CpdA were combined than PTX treatment alone. Isobologram exhibited the synergistic effect of CpdA and PTX. CpdA could significantly decrease expressions of IL-6, XIAP and IL-8, as well as excreted IL-8 levels together with reduced cancer viability after PTX treatment.ConclusionsThe acquired TLR4-mediated PTX resistance in BCA and melanoma is explained partly by the paracrine effect of IL-6 and IL-8 released into the tumor microenvironment and over-production of anti-apoptotic protein, XIAP, in BCA cells and importantly CpdA could reduce this effect and sensitize PTX-induced apoptosis in a synergistic manner. In conclusion, the possible impact of TLR4-dependent signaling pathway in PTX resistance in BCA and melanoma is proposed and using PTX in combination with CpdA may attenuate TLR4-mediated PTX resistance in the treatment of the patients.

Knockdown of LncRNA MAPT-AS1 inhibites proliferation and migration and sensitizes cancer cells to paclitaxel by regulating MAPT expression in ER-negative breast cancers

BackgroundMAPT-AS1, a long non-coding RNA, has not been reported in any previous research about its function in cancers. In this study, we investigated the role of MAPT-AS1 in the progression and paclitaxel resistance in breast cancer, and the regulation between MAPT-AS1 and its natural comparable sense transcripts MAPT.MethodsWe analysed the breast cancer patients’ clinical information and explored the function of MAPT-AS1 by gain- and loss-of function assays in vitro and in vivo. The regulation between MAPT-AS1 and MAPT was confirmed by gene expression analysis and rescue assays. To verify the hypothesis that MAPT-AS1 and MAPT might form a duplex structure, we performed RT-PCR assays on RNA after α-amanitin treatment.ResultsBy analysing the breast cancer patients’ clinical information from the TCGA database, we found that ER-negative patients with younger age (< 60), larger tumors (≥ 2 cm), metastatic lymph nodes and stages (III–IV) had higher expression of MAPT-AS1. MAPT-AS1 is correlated with the cell growth, invasiveness and paclitaxel resistance by regulating its natural comparable sense transcripts MAPT in ER-negative breast cancer cells. The result revealed that MAPT-AS1 overexpression could partially protect the MAPT mRNA from degradation, while MAPT-AS1 knockdown decreased the stability of MAPT mRNA. Meanwhile, MAPT knockdown decreased the expression of MAPT-AS1 mRNA. MAPT-AS1 expressed coordinately with MAPT in breast tumor tissues.ConclusionOur study is the first to report a novel lncRNA MAPT-AS1 in human cancer. ER-negative patients with younger age (< 60), larger tumors (≥ 2 cm), metastatic lymph nodes and stages (III–IV) had higher expression of MAPT-AS1. MAPT-AS1 is correlated with the cell growth, invasiveness and paclitaxel resistance in ER-negative breast cancer cells through antisense pairing with MAPT. MAPT-AS1 may serve as a potential therapeutic target in ER-negative breast cancers.

Folic acid functionalized PEG coated magnetic nanoparticles for targeting anti-cancer drug delivery: Preparation, characterization and cytotoxicity on Doxorubicin, Zoledronic acid and Paclitaxel resistant MCF-7 breast cancer cell lines

ABSTRACTIn this study, MNPs were synthesized, coated with biocompatible polyethylene glycol (PEG) and conjugated with folic acid. Crystal and chemical structures, shape, size and magnetic properties of synthesized nanoparticles were characterized. Agglomeration tendency of naked nanoparticles were prevented by oleic acid addition during the synthesis. All synthesized MNPs have been found to exhibit superparamagnetic behavior at 23°C and 37°C. Cytotoxic effects of MNPs were investigated on Doxorubicin, Zoledronic acid and Paclitaxel resistant MCF-7 breast cancer cell lines. The synthesized nanoparticles have been found to be suitable for drug targeting in terms of size, shape, magnetic and cytotoxic properties.

SH003 reverses drug resistance by blocking signal transducer and activator of transcription 3 (STAT3) signaling in breast cancer cells.

Overcoming drug resistance is an important task for investigators and clinician to achieve successful chemotherapy in cancer patients. Drug resistance is caused by various factors, including the overexpression of P-glycoprotein (P-gp, MDR1). The development of new, useful compounds that overcome drug resistance is urgent. SH003 is extracted from the mixture of three different herbs, and its anticancer effect has been revealed in different cancer cell types. In the present study, we investigated whether SH003 is able to reverse drug resistance using paclitaxel-resistant breast cancer cells (MCF-7/PAC). In our experiments, SH003 significantly decreased cell growth and colony formation in MCF-7/PAC cells and parental MCF-7 cells. This growth inhibition was related to the accumulation of cells in the sub-G0/G1 apoptotic population and an increase in the number of apoptotic cells. SH003 reduced the mRNA expression of multidrug resistance 1 (MDR1) and multidrug resistance-associated proteins (MRPs) in MCF-7/PAC cells. SH003 also down-regulated the expression of P-gp. SH003 reversed drug efflux from MCF-7/PAC cells, resulting in rhodamine123 (Rho123) accumulation. Inhibition of drug resistance by SH003 is related to the suppression of the signal transducer and activator of transcription 3 (STAT3) signaling pathway. SH003 decreased STAT3 activation (p-STAT3) and its nuclear translocation and inhibited the secretion of VEGF and MMP-2, which are STAT3 target genes. An STAT3 inhibitor, JAK inhibitor I and an HIF-1α inhibitor decreased cell growth in MCF-7 and MCF-7/PAC cells. Taken together, these results demonstrate that SH003 can overcome drug resistance, and SH003 might be helpful for chemotherapy in cancer patients.

Involvement of miR-451 in resistance to paclitaxel by regulating YWHAZ in breast cancer

MicroRNAs (miRNAs) have been identified as major post-transcriptional regulators of the initiation and progression of human cancers, including breast cancer. However, the detail role of miR-451 has not been fully elucidated in breast cancer. In this study, we aimed to investigate the biological role and molecular mechanisms of miR-451 in drug resistance in breast cancer cell lines and in xenograft model. We show that miR-451 is decreased in human breast cancer specimens and in paclitaxel-resistant (PR) cells. Ectopic expression of miR-451 could inhibit the cell migration and invasion, promoted apoptosis, induced cell-cycle arrest Furthermore, tyrosine3-monooxygenase/tryptophan5-monooxygenase activation protein zeta (YWHAZ) was identified as a direct target of miR-451. Remarkably, the expression of YWHAZ is inversely correlated with the level of miR-451 in human breast cancer samples. Co-treatment with miR-451 mimics and YWHAZ-siRNA significantly enhanced YWHAZ knockdown in both SKBR3/PR and MCF-7/PR cells Moreover, miR-451 markedly inhibited expression of β-catenin via YWHAZ and subsequently inhibited downstream gene cyclin D1, c-Myc expression. The results of xenograft model in vivo showed that intratumor injection of miR-451 agomir induced a tumor-suppressive effect in SKBR3/PR drug-resistant xenograft model. Taken together, our findings suggested that miR-451 might be considered as important and potential target in paclitaxel-resistant breast cancer treatment.

Establishment and characterization of a triple negative basal-like breast cancer cell line with multi-drug resistance.

Triple-negative breast carcinoma (TNBC) is one of the most aggressive subtypes of breast cancer and is associated with an unfavorable prognosis. The management of TNBC is currently based on the use of classical cytotoxic drugs, i.e., anthracyclines and/or microtubule-binding agents (TBAs). However, conventional chemotherapy is not always effective in these tumors and a systemic relapse is often observed, potentially due to the development of multi-drug resistance (MDR). Therefore, an improved understanding of MDR mechanisms may improve the therapeutic strategies for TNBC. In the present study, a paclitaxel-resistant (TxR) breast cancer cell subline of HCC1806 TNBC cells was established and characterized. The resistance index of this subline was calculated according to the IC50 of HCC1806-TxR relative to the parental HCC1806 cells (16.86-fold). TxR-cells also exhibited cross-resistance to vinblastin, doxorubicin and etoposide (~14-, ~4- and ~3-fold, respectively). As assessed with reverse transcription-quantitative polymerase chain reaction, TxR-resistant cells exhibited the upregulated expression of a number of multidrug resistance-associated genes, including MDR-1, MRP-1, -5, -6 and YB-1. The TxR cells also exhibited an increased expression of MDR-related proteins including MDR1 and MRP-1, which led to a substantial increase (5.4-fold) of the paclitaxel efflux from TxR-cells. In addition, the pro-apoptotic protein Fas was downregulated, whereas the anti-apoptotic Bcl-2 was upregulated, in TxR-cells. This may explain why a reduced extent of apoptosis was observed when TxR cells were exposed to TBAs and topoisomerase type II inhibitors, relative to the parental HCC1806 cells. Thus, the HCC1806-TxR cell line may serve as an appropriate model for the analysis of chemoresistance mechanisms in TNBCs, and for the investigation of novel anticancer agents for overcoming MDR-mediated mechanisms in TNBC.