Cisplatin-resistant Breast Cancer Research Articles

Targeting cisplatin resistance in breast cancer using a combination of Thymoquinone and Silymarin: an in vitro and in vivo study

Background: Breast cancer (BC) is considered the most diagnosed cancer among women globally. This is because of its high possibility of metastasis and high resistance to chemotherapy. Cisplatin is a platinum-based antitumor agent that is used to treat various types of cancer. However, the main obstacle to using this drug is drug resistance. Drug resistance is a cause of most relapses of cancer which eventually lead to death. Nowadays, combining natural products is a trend to overcome drug resistance. Thymoquinone (TQ) is a natural phytochemical that exists mainly in blackseed. It has been used in medicine for decades, especially as an anticancer agent. Silymarin is a milk thistle compound that exhibits anticancer, hepatoprotective, and neuroprotective activity. Hence, the combination of TQ and silymarin could be a probable solution to treat cancer and reduce chemoresistance. Methods: This study tested this combination on cisplatin-sensitive (EMT6/P) and cisplatin-resistant (EMT6/CPR) mouse mammary cell lines. Apoptotic and antiproliferative activity was assessed for TQ and silymarin in vitro using caspase-3 and [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] (MTT) assays, respectively. An in vivo study was performed to evaluate the effect of TQ and silymarin combination in mice inoculated with EMT6/P and EMT6/CPR cells. The safety profile was also examined using creatinine and liver enzyme assays. Results: In vitro, the TQ and silymarin combination synergized in both cell lines. Also, this combination caused apoptosis induction at a higher rate than the single treatment in both cell lines. In vivo, TQ and silymarin combination resulted in a remarkable reduction in tumor size and enhanced the cure rate in mice implanted with EMT6/P and EMT6/CPR cell lines. According to the safety profile results, TQ and silymarin combination was safe. Conclusion: In conclusion, the combination of TQ and silymarin provides a promising solution in treating BC resistant to cisplatin by inducing apoptosis. Further studies are needed to define the exact anticancer mechanisms of this combination.

Zinc finger protein 468 up-regulation of TFAM contributes to the malignant growth and cisplatin resistance of breast cancer cells

BackgroundBecause of the progress on the diagnosis and treatment for patients with breast cancer (BC), the overall survival of the patients has been improved. However, a number of BC patients cannot benefit from the existing therapeutic strategies as the essential molecular events triggering the development of BC are not well understood. Previous studies have shown that abnormal expression of zinc finger proteins is involved in the development of various malignancies, whereas it remains largely unclear on their significance during the progression of BC. In this study, we aimed to explore the clinical relevance, cellular function and underlying mechanisms of zinc finger protein 468 (ZNF468) in BC.MethodsThe clinical relevance of ZNF468 and TFAM was analyzed based on TCGA database. Overexpression or knockdown of ZNF468 and TFAM were performed by transfecting the cells with overexpression plasmids and siRNAs, respectively. Overexpression and knockdown efficacy was checked by immunoblotting. CCK-8, colony formation, transwell and apoptosis experiments were conducted to check the cellular function of ZNF468 and TFAM. The content of mtDNA was measured by the indicated assay kit. The effects of cisplatin on BC cells were detected by CCK-8 and colony formation assays. The regulation of ZNF468 on TFAM was analyzed by RT-qPCR, immunoblotting, dual luciferase activity and ChIP-qPCR assays.ResultsZNF468 was overexpressed in BC patients and inversely correlated with their prognosis. Based on overexpression and knockdown assays, we found that ectopic expression of ZNF468 was essential for the proliferation, growth and migration of BC cells. The expression of ZNF468 also negatively regulated the sensitivity of BC cells to the treatment of cisplatin. Mechanistically, ZNF468 potentiated the transcription activity of TFAM gene via direct binding on its promoter. Lastly, we demonstrated that ZNF468 up-regulation of TFAM was important for the growth, migration and cisplatin resistance in BC cells.ConclusionOur study indicates that ZNF468 promotes BC cell growth and migration via transcriptional activation of TFAM. ZNF468/TFAM axis can serve as the diagnostic and therapeutic target, as well as the predictor of cisplatin effectiveness in BC patients.

TBOPP, a DOCK1 Inhibitor, Potentiates Cisplatin Efficacy in Breast Cancer by Regulating Twist-mediated EMT.

DOCK1 has been reported to be involved in tumor progression and resistance. 1-(2-(30-(trifluoromethyl)-[1,10-biphenyl]-4-yl)-2-oxoethyl)-5-pyrrolidinylsulfonyl2(1H)- pyridone (TBOPP) is a selective DOCK1 inhibitor; however, the role and molecular mechanisms of DOCK1 and its inhibition in breast cancer (BC) resistance remain poorly understood. This study aims toinvestigate the underlying mechanisms of DOCK1 in BC resistance. DOCK1 or Twist siRNA and Twist plasmid were used to explore the function of DOCK1 in vitro experiments. A mouse xenograft model was used for in vivo experiments. In the present study, we demonstrated that DOCK1 siRNA promoted cisplatin sensitivity in BC cells. Moreover, TBOPP also enhances the therapeutic effect of cisplatin both in vitro and in vivo. Mechanistically, DOCK1 siRNA inhibited EMT. Twist 1 is one of the EMT-inducing transcription factors and is known to induce EMT. To further reveal the effect of DOCK in BC cells, we co-transfected with DOCK1 and Twist1 siRNA to BC cells and found that co-transfection with DOCK1 and Twist siRNA could not further enhance the cisplatin sensitivity of BC cells. Moreover, DOCK1 siRNA failed to reverse the effect of Twist 1 up-regulation. Taken together, these results demonstrate that DOCK1 may function as a potential therapeutic target in BC and that combining cisplatin with TBOPP may provide a promising therapeutic strategy for cisplatin-resistant BC patients.

DNA binding, cleavage and anticancer activity of a Zn(II)-Cu(II) hetero-dinuclear carbohydrazone complex containing the secondary ligand 1,10-phenanthroline

A hetero di-nuclear complex [Zn(o-phen)LCu(OAc)] (1) (H3L = o-HOC6H4CH = NNH)2C = O, o-phen = 1,10-phenanthroline) exhibited intercalative DNA binding (Kb = 1.03 × 105 M−1) as revealed from UV–Vis spectral analysis as well as viscosity study and further supported by molecular docking study of 1 with DNA. The apparentbinding constant (Kapp = 21.78 × 105 M−1) obtained from ethidium bromide (EB) displacement assay using fluorescence spectral study further confirmed the efficient binding ability of the complex to DNA. The complex displayed both oxidative as well as hydrolytic DNA cleavage activity. Quantitative hydrolytic cleavage results suggested significant nuclease activity against PUC19 plasmid DNA. Oxidative DNA cleavage experiments done with ROS (reactive oxygen species) scavengers showed the involvement of •OH in the cleavage mechanism. Anticancer activity of 1 was tested by evaluating the cytotoxicity of the complex towards cervical cancer HeLa, cisplatin resistant breast cancer MDA-MB-231 and epidermoid carcinoma A431 cells. IC50 values (11.08 ± 1.1 µM for HeLa, 2.75 ± 0.16 µM for MDA-MB-231 and 1.38 ± 0.07 µM for A431 cells) revealed significant cell death in all three cell lines. Nuclear staining using AO/PI and Hoechst 33,342 suggested cell death occurred due to apoptosis in these cancer cells. 1 induced high level of ROS in HeLa cells. It also caused G2/M phase arrest in HeLa cells as revealed from cell cycle analysis.

TMED2 Induces Cisplatin Resistance in Breast Cancer via Targeting the KEAP1-Nrf2 Pathway.

Cisplatin is the first-line treatment for breast cancer, but it faces challenges of drug resistance. This study investigated new molecular mechanisms underlying cisplatin resistance in breast cancer. We analyzed sequencing data from the TCGA database to identify potential associations between transmembrane emp24 protein transport domain containing 2 (TMED2) and breast cancer. Western blotting, real-time PCR, CCK-8, and TUNEL assays were used to measure the effects and molecular mechanism of TMED2 on cisplatin resistance in MCF-7 and MDA-MB-231 cell lines. TMED2 was overexpressed in breast cancer and associated with poor prognosis. TMED2 increased cisplatin resistance in breast cancer cells in vitro via promoting ubiquitination of Kelch-like ECH-associated protein 1 (KEAP1), relieving inhibition of KEAP1 on nuclear factor erythroid 2-related factor 2 (Nrf2), and increasing expression of downstream drug resistance related genes, such as heme oxygenase 1 (HO-1) and NAD (P) H quinone oxidoreductase 1 (NQO1). We identified a new molecular mechanism by which TMED2 affects cisplatin resistance in breast cancer. Our results provide theoretical guidance for future clinical applications.

Combination of Probiotics and Resveratrol to Target Drug Resistance in Breast Cancer: An In vitro and In vivo Study

Background: Probiotics exhibit significant activity in the immune system by activating multiple immune mechanisms. Resveratrol is a non-flavonoid polyphenol. It has various pharmacological effects, including anti-oxidative, anti-inflammatory, anti-proliferative, and anti-angiogenesis effects. Objectives: The present study investigates the potential immunomodulatory and antitumor activity of the combination treatment of probiotics and resveratrol in sensitive and cisplatin-resistant breast cancer. Methods: In the in vivo study, tumor-bearing mice received one of the following treatments: 2.5*108 CFU/ml probiotics, 50 mg/kg resveratrol, the combination of probiotics and resveratrol, vehicle, or cisplatin. Balb/C mice were inoculated with sensitive EMT6/P and cisplatin resistance EMT6/CPR cancer cell lines, and in vivo antitumor activity was evaluated. Results: The antiproliferative activity of the probiotics, resveratrol, and their combination treatments was assessed using an MTT assay to evaluate lymphocyte proliferation activity. LDH colorimetric assay was conducted to measure the effectiveness of the treatments on the activity of natural killer cells. Nitro blue tetrazolium assay and neutral red method were used to evaluate macrophage function. Conclusion: The combination treatment showed an enhanced effect in splenic lymphocyte proliferation, macrophage function, phagocytosis, and pinocytosis in both cell lines. A significant reduction in tumor size and weight in EMT6/P and EMT6/CPR-bearing mice occurred. Hence, the combination treatment of probiotics and resveratrol was found to have a valuable activity against sensitive and cisplatin-resistant breast cancer cells and might act as a stimulator of the immune system. Therefore, the combination of probiotics and resveratrol deserves further analysis to be used in cancer prevention and treatment.

Synthesis, Characterization, DNA/HSA Interaction, and Cytotoxic Activity of a Copper(II) Thiolate Schiff Base Complex and Its Corresponding Water-Soluble Stable Sulfinato-O Complex Containing Imidazole as a Co-ligand.

A Cu(II) thiolato complex [CuL(imz)] (1) (H2L = o-HOC6H4C(H)=NC6H4SH-o) and the corresponding water-soluble stable sulfinato-O complex [CuL'(imz)] (2) (H2L' = o-HOC6H4C(H)=NC6H4S(=O)OH) were synthesized and characterized using physicochemical techniques. Compound 2 is found to be a dimer in the solid state as characterized using single-crystal X-ray crystallography. XPS studies clearly showed the differences in the sulfur oxidation states in 1 and 2. Both compounds are found to be monomers in solution as revealed from their four-line X-band electron paramagnetic resonance spectra in CH3CN at room temperature (RT). 1-2 were tested to assess their ability to exhibit DNA binding and cleavage activity. Spectroscopic studies and viscosity experiments suggest that 1-2 bind to CT-DNA through the intercalation mode having moderate binding affinity (Kb ∼ 104 M-1). This is further supported by molecular docking studies of complex 2 with CT-DNA. Both complexes display significant oxidative cleavage of pUC19 DNA. Complex 2 also showed hydrolytic DNA cleavage. The interaction of 1-2 with HSA revealed that they have strong ability to quench the intrinsic fluorescence of HSA by a static quenching mechanism (kq ∼ 1013 M-1 s-1). This is further complemented by Förster resonance energy transfer studies that revealed binding distances of r = 2.85 and 2.75 nm for 1 and 2, respectively, indicating high potential for energy transfer from HSA to complex. 1-2 were capable of inducing conformational changes of HSA at secondary and tertiary levels as observed from synchronous and three-dimensional fluorescence spectroscopy. Molecular docking studies with 2 indicate that it forms strong hydrogen bonds with Gln221 and Arg222 located near the entrance of site-I of HSA. 1-2 showed potential toxicity in human cervical cancer HeLa cells, lung cancer A549 cells, and cisplatin-resistant breast cancer MDA-MB-231 cells and appeared to be most potent against HeLa cells (IC50 = 2.04 μM for 1 and 1.86 μM for 2). In HeLa cells, 1-2 mediated cell cycle arrest in S and G2/M phases, which progressed into apoptosis. Apoptotic features seen from Hoechst and AO/PI staining, damaged cytoskeleton actin viewed from phalloidin staining, and increased caspase-3 activity upon treatment with 1-2 collectively suggested that they induced apoptosis in HeLa cells via caspase activation. This is further supported by western blot analysis of the protein sample extracted from HeLa cells treated with 2.

Blockade of store-operated calcium entry sensitizes breast cancer cells to cisplatin therapy via modulating inflammatory response

Store-operated calcium entry (SOCE) is an important pathway for calcium signaling that regulates calcium influx across the plasma membrane upon the depletion of calcium stores in the endoplasmic reticulum. SOCE participates in regulating a number of physiological processes including cell proliferation and migration while SOCE dysregulation has been linked with pathophysiological conditions such as inflammation and cancer. The crosslink between cancer and inflammation has been well-established where abundant evidence demonstrate that inflammation plays a role in cancer pathophysiology and the response of cancer cells to chemotherapeutic agents including cisplatin. Indeed, the efficacy of cisplatin against cancer cells is reduced by inflammation. Interestingly, it was shown that SOCE enhances inflammatory signaling in immune cells. Therefore, the main objectives of this study are to examine the impact of SOCE inhibition on the cisplatin sensitivity of breast cancer cells and to explore its related mechanism in modulating the inflammatory response in breast cancer cells. Our findings showed that SOCE inhibitor (BTP2) enhanced cisplatin cytotoxicity against resistant breast cancer cells via inhibition of cell proliferation and migration as well as induction of apoptosis. We also found an upregulation in the gene expression of two major components of SOCE, STIM1 and ORAI1, in cisplatin-resistant breast cancer cells compared to cisplatin-sensitive breast cancer cells. In addition, cisplatin treatment increased the gene expression of STIM1 and ORAI1 in cisplatin-resistant breast cancer cells. Finally, this study also demonstrated that cisplatin therapy caused an increase in the gene expression of inflammatory mediators COX2, IL-8, and TNF-α as well as COX2 protein and upon SOCE inhibition using BTP2, the effect of cisplatin on the inflammatory mediators was reversed. Altogether, this study has proven the pivotal role of SOCE in cisplatin resistance of breast cancer cells and showed the importance of targeting this pathway in improving breast cancer therapy.

Combination of Ashwagandha Water Extract and Intermittent Fasting as a Therapy to Overcome Cisplatin Resistance in Breast Cancer: An in vitro and in vivo Study.

Breast cancer is considered a universal public health dilemma in women. Due to the high toxicity and low selectivity of conventional anticancer therapies, there is a growing trend of using plant-derived natural products in cancer prevention and therapy. Ashwagandha (Withania somnifera, WS) has been used in the Mediterranean region and Ayurvedic medicine for millennia as a functional food and a medicinal plant with anticancer activity. Besides, intermittent fasting (IF) has been engaged recently in cancer treatment. Hence, the combination of WS and IF provides possible solutions to treat cancer and reduce chemoresistance when combined with chemotherapy. In this study, WS root (WSR), IF, and cisplatin were tested on cisplatin-sensitive (EMT6/P) and cisplatin-resistant (EMT6/CPR) mouse mammary cell lines. The phytochemical content of the WSR extract was analyzed using liquid chromatography–mass spectrometry (LC-MS) analysis. Antiproliferative and apoptotic effects were assessed for WSR extract, cisplatin, and their combination in vitro using [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] (MTT) and caspase-3 assays. An in vivo study was used to assess the effect of WSR extract, IF, cisplatin, and their combinations in mice inculcated with EMT6/P and EMT6/CPR cells. The safety profile was also investigated using liver enzymes and creatinine assays. In vitro, WSR extract and cisplatin had a synergistic effect in both cell lines. The same combination induced an apoptotic effect higher than the single treatment in both cell lines. In vivo, several combinations of WSR extract, IF, or cisplatin caused significant tumor size reduction and improved the cure rate in mice implanted with EMT6/P and EMT6/CPR cell lines. IF-treated groups showed a significant reduction in serum glucose and an elevation in β-hydroxybutyrate (BHB) levels. In the safety profile, WSR extract, IF, and their combinations were safe. Overall, the combination of WSR extract and IF provides a promising solution for breast cancer treatment besides cisplatin by reducing the proliferation of cancer cells through induction of apoptosis. Moreover, they minimize cisplatin toxicity to the liver and kidney.

Expression of Phosphatase and Tensin Homolog Deleted on Chromosome Ten on the Development of Cisplatin Resistance in Breast Cancer by TGF-β1 Signal Pathway

Introduction: This study aims to evaluate the expression of PTEN on the development of cisplatin resistance in breast cancer by TGF-β1 signal pathway in order to investigate the prognostic value of PTEN and TGF-β1 for breast cancer. Material and Methods: In this study, HE staining, Immunohistochemical staining, Immunofluorescence and Western blotting were used to detect the expression of PTEN and TGF-β1 in breast cancer MCF-7 cells to explain clearly the relationship between PTEN and TGF-β1 on TGF-β1 treated MCF-7 Cells. Results: The experiment results showed the expression of PTEN and TGF-β1 in Human breast cancer increased obviously compared with paracancerous tissues (P < 0.05). The expression of PTEN and TGF-β1 was closely correlated with tumor size, distant metastasis, pathological stage and progesterone receptor status, but not with age and lymph node status. At the same time, the expression of PTEN and TGF-β1 in cisplatin-treated MCF-7 Cells reduced as compared with untreated breast cancer cells (P < 0.05). In addition, the expression of PTEN increased by TGF-β1 inducer treated Human Breast Cancer Cells. However, the expression of PTEN in TGF-β1 inhibitor treated Human Breast Cancer Cells was lower than in untreated breast cancer cells (P < 0.05). Conclusions: PTEN and TGF-β1 played an important role in Human Breast cancer. In addition, the expression of PTEN could be regulated by TGF-β1 in Cisplatin and TGF-β1 treated Human Breast Cancer Cells.

Retraction of: miR-100 Reverses Cisplatin Resistance in Breast Cancer by Suppressing HAX-1

Retraction of: miR-100 Reverses Cisplatin Resistance in Breast Cancer by Suppressing HAX-1

Regulation of Cellular and Cancer Stem Cell-Related Putative Gene Expression of Parental and CD44+CD24- Sorted MDA-MB-231 Cells by Cisplatin.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype that promotes a higher risk of metastasis and cancer reoccurrence. Cisplatin is one of the potential anticancer drugs for treating TNBC. However, the occurrence of cisplatin resistance still remains one of the challenges in fully eradicating TNBC. The presence of cancer stem cells (CSCs) has been proposed as one of the factors contributing to the development of cisplatin resistance. In this study, we aimed to characterize the cellular properties and reveal the corresponding putative target genes involved in cisplatin resistance associated with CSCs using the TNBC cell line (MDA-MB-231). CSC-like cells were isolated from parental cells and the therapeutic effect of cisplatin on CSC-like cells was compared to that of the parental cells via cell characterization bioassays. A PCR array was then conducted to study the expression of cellular mRNA for each subpopulation. As compared to treated parental cells, treated CSCs displayed lower events of late apoptosis/necrosis and G2/M phase cell arrest, with higher mammosphere formation capacity. Furthermore, a distinct set of putative target genes correlated to the Hedgehog pathway and angiogenesis were dysregulated solely in CSC-like cells after cisplatin treatment, which were closely related to the regulation of chemoresistance and self-renewability in breast cancer. In summary, both cellular and gene expression studies suggest the attenuated cytotoxicity of cisplatin in CSC-like cells as compared to parental cells. Understanding the role of dysregulated putative target genes induced by cisplatin in CSCs may aid in the potential development of therapeutic targets for cisplatin-resistant breast cancer.

Upregulation of microRNA-181a-5p increases the sensitivity of HS578T breast cancer cells to cisplatin by inducing vitamin D receptor-mediated cell autophagy.

Breast cancer (BC) is the leading cause of death in females worldwide. Although cisplatin is a strong-effect and broad-spectrum chemotherapy drug, resistance to cisplatin remains a significant factor effecting clinical efficacy. The underlying mechanism of cancer cell resistance to cisplatin is not fully understood. MicroRNAs (miRs/miRNAs), as a regulator, are involved in regulating chemosensitivity to numerous chemotherapeutic drugs. The present study aimed to investigate the function of miR-181a-5p as a potential tumor suppressor in improving the efficiency of cisplatin in BC. The IC50 of cisplatin and miR-181a-5p expression were determined in five BC cell lines, and HS578T was selected as an appropriate cell line for subsequent experiments. The sensitivity of HS578T cells to cisplatin was assessed using cell proliferation, migration and apoptosis assays. Western blotting was performed to detect the expression of vitamin D receptor (VDR) and autophagy in HS578T cells. It was found that the increase in autophagy resulted in increased apoptosis and sensitivity to cisplatin in HS578T cells. miR-181a-5p transfection also inhibited the proliferation and migration ability of HS578T cells and induced apoptosis. Meanwhile, HS578T cells have increased sensitivity to cisplatin. VDR, as a target gene and autophagy regulator of miR-181a-5p, was negatively regulated by miR-181a-5p. Upon the decrease in VDR expression, the autophagy in HS578T cells was increased. These results indicate that the increase in autophagy enhanced the chemosensitivity of cisplatin by inducing apoptosis of HS578T cells and by inhibiting proliferation and migration. The present study showed that miR-181a-5p increased the chemical sensitivity of HS578T cells to cisplatin by inhibiting VDR to promote autophagy. The use of miR-181a-5p/autophagy/VDR-based treatment strategies may be a potential method to overcome cisplatin resistance in BC.

Targeted Inhibition of miR-221/222 Promotes Cell Sensitivity to Cisplatin in Triple-Negative Breast Cancer MDA-MB-231 Cells.

Cisplatin has been widely used in the treatment of a various types of cancers including triple-negative breast cancer (TNBC) by damaging DNA and inducing apoptosis. However, its anti-cancer effects are often limited due to chemo-resistance, which is one of the main reasons causing cancer relapse and metastasis. To overcome resistance, cisplatin is often used in combination with other drugs or molecules. Our study found that the targeted inhibition of miR-221/222 in MDA-MB-231 cells promoted cisplatin-induced cell apoptosis, and increased the cell sensitivity to cisplatin in vitro. Much higher expression levels of miR-221/222 were detected in the cisplatin-resistant MDA-MB-231 cells and in cisplatin-resistant breast cancer patients. The combination chemotherapy of cisplatin with anti-miR-221/222 showed much higher efficiency in suppressing tumor growth in the mice transplanted with MDA-MB-231 cells. In addition, anti-miR-221 and anti-miR-222 showed synergetic effects on improving sensitivity to cisplatin in MDA-MB-231 cells. Suppression of SOCS1-STAT3-Bcl-2 pathway and activation of p53-Pten signaling both contribute to anti-miR-221/222-induced sensitivity to cisplatin in MDA-MB-231 cells. These findings suggest the potential of a novel approach for the combination chemotherapy of cisplatin with small non-coding RNA in treatment of human TNBC.

SNHG15 Contributes To Cisplatin Resistance In Breast Cancer Through Sponging miR-381.

BackgroundIncreasing evidence implies the participation of long non-coding RNAs (lncRNAs) in chemoresistance to cancer treatment. Their role and molecular mechanisms in breast cancer chemoresistance, nevertheless, are yet not considerably elucidated. In this work, we research the function of small nucleolar RNA host gene 15 (SNHG15) in cisplatin (DDP) resistance of breast cancer and uncover the underlying molecular mechanism.MethodsSNHG15 and miR-381 expression levels were detected using Quantitative real-time PCR (qRT-PCR) analysis. The functional roles of SNHG15 and miR-381 in breast cancer were determined using MTT assay and flow cytometry analysis. The effect of SNHG15 on miR-381 expression was determined using Luciferase reporter assay, RNA immunoprecipitation (RIP) assay and qRT-PCR analysis.ResultsSNHG15 was found to be up-regulated in cisplatin resistant breast cancer tissues and cell lines. Breast cancer patients with high SNHG15 expression had a poor prognosis. SNHG15 silencing enhanced cisplatin sensitivity of MCF-7/DDP and MDA-MB-231/DDP cells. Additionally, SNHG15 could function as a miR-381 sponge. miR-381 overexpression could overcome cisplatin resistance. miR-381 knockdown countered SNHG15 knockdown-mediated enhancement of cisplatin sensitivity in MCF-7/DDP and MDA-MB-231/DDP cells. Besides, SNHG15 knockdown facilitated cisplatin sensitivity of cisplatin resistant breast cancer cells in vivo.ConclusionIn summary, SNHG15 knockdown overcame cisplatin resistance of breast cancer by sponging miR-381, providing a novel therapeutic target for breast cancer.

MiR-381 overcomes cisplatin resistance in breast cancer by targeting MDR1.

Increasing evidence suggests the involvement of microRNA-381 (miR-381) in chemoresistance of cancer treatment. However, its function and molecular mechanisms in breast cancer chemoresistance are still not well elucidated. In the present study, we aimed to investigate the functional role of miR-381 in cisplatin (DDP) resistance of breast cancer and discover the underlying molecular mechanism. The expression levels of miR-381 and MDR1 were detected by quantitative real-time PCR (qRT-PCR) and Western blot analysis in breast cancer tissues and cell lines. The DDP sensitivity and cell apoptosis of breast cancer cells were determined by MTT assay and flow cytometric analysis, respectively. The relationship between miR-381 and MDR1 was explored by target prediction and luciferase reporter analysis. miR-381 was decreased in DDP-resistant breast cancer tissues and cell lines. Low miR-381 expression was correlated with poor prognosis of breast cancer patients. miR-381 overexpression improved DDP sensitivity of MCF-7/DDP and MDA-MB-231/DDP cells. Conversely, miR-381 inhibition lowered the response of MCF-7 and MDA-MB-231 to DPP. Moreover, miR-381 could directly suppress multidrug resistance 1 (MDR1) expression. MDR1 knockdown could overcome DDP resistance in MCF-7/DDP and MDA-MB-231/DDP cells, while MDR1 overexpression led to DDP resistance in MCF-7 and MDA-MB-231 cells. Notably, MDR1 overexpression counteracted the inductive effect of miR-381 mimics on DDP sensitivity of MCF-7/DDP and MDA-MB-231/DDP cells. On the contrary, miR-381 inhibition-mediated DDP resistance in MCF-7 and MDA-MB-231 cells was reversed by MDR1 knockdown. In summary, miR-381 could overcome DDP resistance of breast cancer by directly targeting MDR1, providing a novel therapeutic target for breast cancer chemoresistance.

Apollon silencing enhanced the sensitivity to cisplatin-induced cytotoxicity of chemoresistant breast cancer cell line MCF-1/cisplatin

Objective To explore the effect of Apollon on cisplatin-induced chemoresistance of breast cancer cell line MCF-1/cisplatin (DDP). Methods Apollon silencing was performed by transient transfection of small interfering RNA (siRNA). The inhibitory effect of different concentrations of cisplatin (10, 20, 40, 80, and 100 μmol/L) on cell viability was measured by methyl thiazol tetrazolium (MTT) assays. The mRNA and protein expression levels were detected by real-time quantitative polymerase chain reaction (Real-time PCR) and Western blotting, respectively. Results As compared with MCF-7 cells, Apollon mRNA and protein levels were 1.70±0.21 folds and 2.23±0.33 folds enhanced in cisplatin-resistant breast cancer cell line MCF-1/DDP, respectively (P=0.007, 0.003). Knockdown of Apollon increased the sensitivity to cisplatin-induced cytotoxicity of MCF-1/DDP. As compared with non-transfected control group, the half maximal inhibitory concentration (IC50) value of cisplatin was significantly decreased from (81.39±3.67) μmol/L to (33.24±2.01) μmol/L (P=0.002). Meanwhile, the mRNA and protein expression levels of Apollon and β-catenin were remarkably declined to 0.43±0.16 (P=0.005), 0.54±0.10 (P=0.006) and 0.23±0.08 (P=0.003), 0.44±0.20 (P=0.005) after Apollon silencing, respectively. In addition, the mRNA and protein expression levels of β-catenin were significantly 1.91±0.23 folds (P=0.0044) and 2.21±0.31 (P=0.0023) folds enhanced with little influence on Apollon expression (P=0.890, 0.730) upon the treatment of WAY-262611 in siRNA-transfected cells. Conclusion Apollon silencing enhanced the sensitivity to cisplatin-induced cytotoxicity of chemoresistant breast cancer cell line MCF-1/DDP, which might be partially dependent on the reduced β-catenin expression. Key words: Breast cancer; Apollon; Cisplatin-resistant

Glutaryl Polyamidoamine Dendrimer for Overcoming Cisplatin-Resistance of Breast Cancer Cells

Cisplatin has limited clinical applications due to drug resistance. PAMAM dendrimer was chosen as a vehicle to counteract cisplatin-resistance and its mechanism was assessed. Generation 5 Polyamidoamine dendrimer (G5) was modified by glutaric anhydride (GA) and then conjugated with cisplatin. The cisplatin release of G5-GA-cisplatin was evaluated at pH 5.5 and pH 7.4. The cytotoxicity of G5-GA-cisplatin and free cisplatin was compared in cisplatin-resistant breast cancer cell line MCF-7R. The intracellular platinum content of MCF-7R was determined using ICP-MS. The expression of Ctr1 and ATP7B of MCF-7R cells was also evaluated. An average of 75 amino groups present in the G5 PAMAM surface were converted into glutaric acid (G5-GA75) and platinum loading was 350±21 μg per 1 mg of G5-GA75. G5-Ac75-cisplatin complex exhibited controlled release of cisplatin at different pH over a period of 96 h. After 96 h incubation with G5-Ac75-cisplatin, cell viability was 27.47±2.53%, 12.18±0.65% and 11.62±0.84% using platinum concentration of 1 μg/ml, 3 μg/ml and 5 μg/ml, respectively. Meanwhile, 46.33±5.06% cells survived even in the high platinum concentration of 5 μg/ml after 96 h incubation with free cisplatin. G5-GA75 led to 3-6 times higher cisplatin accumulation than free cisplatin in MCF-7R cells, because MCF-7R cells exhibited lower Ctr1 expression and higher ATP7B expression than MCF-7 cells. The G5-GA75-cisplatin complex displayed greater anticancer activity than free cisplatin in the cisplatin-resistant breast cancer cell line MCF-7R. The low levels of Ctr1 and high levels of ATP7B in MCF-7R caused G5-GA75 to allow the accumulation of cisplatin, which in turn increased the cytotoxicity. Results indicated that glutaryl G5 PAMAM may be a potential carrier for cisplatin targeting in breast cancer.

ER-\u03b136 mediates cisplatin resistance in breast cancer cells through EGFR/HER-2/ERK signaling pathway

BackgroundER-α36, a novel ER-α66 variant, has been demonstrated to promote tamoxifen resistance in breast cancer cells. However, the role and mechanisms of ER-α36 in cisplatin resistance of breast cancer cells remain unclear. This study investigates the expression and role of ER-α36 in cisplatin resistance of breast cancer cells and elucidates its underlying mechanisms.MethodsThe expression of ER-α36 and the proteins involved in nongenomic estrogen signaling was evaluated by western blot analysis. Cisplatin sensitivity was explored by CCK-8 assay, monolayer colony formation assay and apoptosis assays, respectively. ER-α36 siRNAs/shRNAs and overexpression vector were transfected into cells to down-regulate or up-regulate ER-α36 expression. Loss-and gain-of function assays were performed to investigate the role of ER-α36 in cisplatin sensitivity. The interaction between ER-α36 and EGFR/HER-2 were detected using CoIP. A mouse xenograft model of breast cancer was established to verify the role of ER-α36 in vivo.ResultsER-α36 is expressed at higher levels in cisplatin-resistant breast cancer cells compared to cisplatin sensitive cells. Cisplatin induced up-regulation of ER-α36 in a dose-dependent manner in breast cancer cells. Overexpression of ER-α36 leaded to cell resistant to cisplatin and knockdown of ER-α36 in cisplatin-resistant breast cancer cells restored cisplatin sensitivity. The up-regulation of ER-α36 resulted in increased activation of nongenomic estrogen signaling, which was responsible for cisplatin resistance. Disruption of ER-α36-mediated nongenomic estrogen signaling with kinase inhibitors significantly inhibited cisplatin-induced expression of ER-α36 and increased cisplatin sensitivity. The in vivo experiment also confirmed that up-regulation of ER-α36 attenuated cisplatin sensitivity in a mouse xenograft model of breast cancer.ConclusionsThe results for the first time demonstrated that ER-α36 mediates cisplatin resistance in breast cancer cells through nongenomic estrogen signaling, suggesting that ER-α36 may serve as a novel target for cisplatin resistance and a potential indicator of cisplatin sensitivity in breast cancer treatment.

Curcumin increases breast cancer cell sensitivity to cisplatin by decreasing FEN1 expression.

Flap endonuclease 1 (FEN1) overexpression promotes breast cancer. We investigated the role of FEN1 in cisplatin resistance and the chemosensitizing effects of curcumin in breast cancer cells. We demonstrated that FEN1 overexpression promotes cisplatin resistance in breast cancer cells, and that FEN1 knockdown enhances cisplatin sensitivity. Curcumin down-regulated FEN1 expression in a dose-dependent manner. A combination of cisplatin and curcumin enhanced breast cancer cell sensitivity to cisplatin by down-regulating FEN1 expression in vitro and in vivo. Increased ERK phosphorylation contributed to cisplatin resistance and cisplatin-induced FEN1 overexpression in breast cancer cells. Inhibiting ERK phosphorylation stimulated the chemosensitizing effect of curcumin to cisplatin by targeting FEN1. These data reveal that FEN1 overexpression promotes cisplatin resistance, and suggest FEN1 could be a potential therapeutic target to relieve cisplatin resistance in breast cancer. We also demonstrated that curcumin sensitizes breast cancer cells to cisplatin through FEN1 down-regulation.