Knocking-down cyclin A(2) by siRNA suppresses apoptosis and switches differentiation pathways in K562 cells upon administration with doxorubicin

Biomaterials for polynucleotide delivery to anchorage-independent cells

Comparison of various chemical vectors used for polynucleotide delivery to mammalian anchorage-independent cells.

Enhanced Therapeutic Efficacy of Doxorubicin for Breast Cancer Using Chitosan Oligosaccharide-Modified Halloysite Nanotubes

Halloysite nanotubes (HNTs) are natural aluminosilicates with unique hollow lumen structure, also having high specific area, good biocompatibility, nontoxicity, and low price. Here, we designed a chitosan oligosaccharide-grafted HNTs (HNTs-g-COS) as a doxorubicin (DOX) carrier for treating breast cancer both in vitro and in vivo. The structure of HNTs-g-COS was first characterized by various methods. HNTs-g-COS showed positively charged surface and improved hemocompatibility. DOX-loaded HNTs-g-COS (DOX@HNTs-g-COS) released in cell lysate in a controlled manner. The IC₅₀ value of DOX@HNTs-g-COS toward MCF-7 cells was 1.17 μg mL^-1, while it was 2.43 μg mL^-1 for free DOX. DOX@HNTs-g-COS increased the apoptosis effects of MCF-7 cells as shown in flow cytometry results. Also, reactive oxygen species of cells induced by DOX@HNTs-g-COS were drug-dose-dependent. DOX@HNTs-g-COS could enter the MCF-7 cells and induce mitochondrial damage as well as attack the nuclei. The in vivo antitumor effect of DOX@HNTs-g-COS was investigated in 4T1-bearing mice. The tumor-inhibition ratio of DOX@HNTs-g-COS was 83.5%, while it was 46.1% for free DOX. All mice treated with DOX@HNTs-g-COS survived over 60 days. DOX@HNTs-g-COS showed fewer ruptured cardiomyocytes and no obvious systemic toxicity. Therefore, the rational designed HNTs nanocarrier for chemotherapy drug showed promising applications in tumor treatment.

Mmu-miR-125b overexpression suppresses NO production in activated macrophages by targeting eEF2K and CCNA2

BACKGROUND

MicroRNAs have been shown to be important regulators of the immune response and the development of the immune system. It was reported that microRNA-125b (miR-125b) was down-regulated in macrophages challenged with endotoxin. However, little is known about the function and mechanism of action of miR-125b in macrophage activation. Macrophages use L-arginine to synthesize nitric oxide (NO) through inducible NO synthase (iNOS), and the released NO contributes to the tumoricidal activity of macrophages.

METHODS

Luciferase reporter assays were employed to validate regulation of a putative target of miR-125b. The effect of miR-125b on endogenous levels of this target were subsequently confirmed via Western blot. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was performed to determine the expression level of miR-125b in macrophage. MTS assays were conducted to explore the impact of miR-125b overexpression on the cell viability of 4T1 cells.

RESULTS

Here, we demonstrate that mmu-miR-125b overexpression suppresses NO production in activated macrophages and that LPS-activated macrophages with overexpressed mmu-miR-125b promote 4T1 tumor cell proliferation in vitro and 4T1 tumor growth in vivo. CCNA2 and eEF2K are the direct and functional targets of mmu-miR-125b in macrophages; CCNA2 and eEF2K expression was knocked down, which mimicked the mmu-miR-125b overexpression phenotype.

CONCLUSIONS

These data suggest that mmu-miR-125b decreases NO production in activated macrophages at least partially by suppressing eEF2K and CCNA2 expression.

Dual drug loaded nanoliposomal chemotherapy: A promising strategy for treatment of head and neck squamous cell carcinoma

The rising incidence of head and neck cancer and the drawbacks of currently used therapeutic strategies such as salvage surgery followed by adjuvant chemo- or radiotherapy have encouraged pursuits for better therapeutic approaches. This work describes the development and characterization of a PEGylated liposomal nanocarrier encapsulated with trans-resveratrol (Res), a plant stilbenoid, and doxorubicin hydrochloride (Dox), a standard chemotherapeutic agent for treatment of oral squamous cell carcinoma. The two drugs were loaded in liposomes prepared from egg phosphatidylcholine and DSPE-PEG with maximum encapsulation efficiencies of about 80% for each drug achieved at Res to Dox ratio of 2:1. The liposomal suspension was found to be stable with a zeta potential of -30.53 mV and size of approximately 250 nm. Thermal properties and release kinetics of the dual drug loaded liposomes were determined. The nanoformulation was evaluated for its in vitro anticancer efficacy on an oral squamous cell carcinoma cell line (NT8e). The cell uptake mechanism of the liposomal formulation was determined using pharmacological inhibitors for different endocytosis pathways. The combination effect of the two drugs was evaluated in free form and was found to have synergistic effects. The formulation was found to have a higher IC50 value than that of free doxorubicin hydrochloride but was found to have a superior effect on the signaling proteins involved in apoptosis and cell cycle.

An Efficient Method for Electroporation of Small Interfering RNAs into ENCODE Project Tier 1 GM12878 and K562 Cell Lines

The Encyclopedia of DNA Elements (ENCODE) Project aims to identify all functional sequence elements in the human genome sequence by use of high-throughput DNA/cDNA sequencing approaches. To aid the standardization, comparison, and integration of data sets produced from different technologies and platforms, the ENCODE Consortium selected several standard human cell lines to be used by the ENCODE Projects. The Tier 1 ENCODE cell lines include GM12878, K562, and H1 human embryonic stem cell lines. GM12878 is a lymphoblastoid cell line, transformed with the Epstein-Barr virus, that was selected by the International HapMap Project for whole genome and transcriptome sequencing by use of the Illumina platform. K562 is an immortalized myelogenous leukemia cell line. The GM12878 cell line is attractive for the ENCODE Projects, as it offers potential synergy with the International HapMap Project. Despite the vast amount of sequencing data available on the GM12878 cell line through the ENCODE Project, including transcriptome, chromatin immunoprecipitation-sequencing for histone marks, and transcription factors, no small interfering siRNA-mediated knockdown studies have been performed in the GM12878 cell line, as cationic lipid-mediated transfection methods are inefficient for lymphoid cell lines. Here, we present an efficient and reproducible method for transfection of a variety of siRNAs into the GM12878 and K562 cell lines, which subsequently results in targeted protein depletion.

A new arylbenzofuran derivative functions as an anti-tumour agent by inducing DNA damage and inhibiting PARP activity

We previously reported that 7-hydroxy-5, 4'-dimethoxy-2-arylbenzofuran (HDAB) purified from Livistona chinensis is a key active agent. The present study investigated the function and molecular mechanism of HDAB. HDAB treatment of cervical cancer cells resulted in S phase arrest and apoptosis, together with cyclin A2 and CDK2 upregulation. Cyclin A2 siRNA and a CDK inhibitor efficiently relieved S phase arrest but increased the apoptosis rate. Mechanistic studies revealed that HDAB treatment significantly increased DNA strand breaks in an alkaline comet assay and induced ATM, CHK1, CHK2 and H2A.X phosphorylation. Wortmannin (a broad inhibitor of PIKKs) and CGK733 (a specific ATM inhibitor), but not LY294002 (a phosphatidylinositol 3-kinase inhibitor) or NU7026 (a DNA-PK specific inhibitor), prevented H2A.X phosphorylation and γH2A.X-positive foci formation in the nuclei, reversed S phase arrest and promoted the HDAB-induced apoptosis, suggesting that HDAB is a DNA damaging agent that can activate the ATM-dependent DNA repair response, thereby contributing to cell cycle arrest. In addition, molecular docking and in vitro activity assays revealed that HDAB can correctly dock into the hydrophobic pocket of PARP-1 and suppress PARP-1 ADP-ribosylation activity. Thus, the results indicated that HDAB can function as an anti-cancer agent by inducing DNA damage and inhibiting PARP activity.

Effect of cell cycle phase on the sensitivity of SAS cells to sonodynamic therapy using low-intensity ultrasound combined with 5-aminolevulinic acid in vitro

Sonodynamic therapy (SDT) with 5-aminolevulinic acid (5-ALA) can effectively inhibit various types of tumor in vitro and in vivo. However, the association between the efficacy of SDT and the phase of the cell cycle remains to be elucidated. 5-ALA may generate different quantities of sonosensitizer, protoporphyrin IX (PpIX), in different phases of the cell cycle, which may result in differences in sensitivity to 5-ALA-induced SDT. The present study aimed to investigate the effect of the cell cycle on the susceptibility of SAS cells to SDT following synchronization to different cell cycle phases. These results indicates that the rates of cell death and apoptosis of the SAS cells in the S and G2/M phases were significantly higher following SDT, compared with those in the G1-phase cells and unsynchronized cells, with a corresponding increase in PpIX in the S and G2/M cells. In addition, the expression of caspase-3 increased, while that of B-cell lymphoma (Bcl)-2 decreased markedly in theS and G2/M cells following SDT. Cyclin A was also expressed at higher levels in the S and G2/M cells, compared with the G1-phase cells. SDT also caused a significant upregulation of cyclin A in all phases of the cell cycle, however this was most marked in the S and G2/M cells. It was hypothesized that high expression levels of cyclin A in the S and G2/M cells may promote the induction of caspase-3 and reduce the induction of Bcl-2 by SDT and, therefore, enhance apoptosis. Taken together, these data demonstrated that cells in The S and G2/M phases generate more intracellular PpIX, have higher levels of cyclin A and are, therefore, more sensitive to SDT-induced cytotoxicity. These findings indicate the potential novel approach to preventing the onset of cancer by combining cell-cycle regulators with SDT. This sequential combination therapy may be a simple and cost-effective way of enhancing the effects of SDT in clinical settings.

Therapeutic delivery of cyclin-A2 via recombinant adeno-associated virus serotype 9 restarts the myocardial cell cycle: an in vitro study

Cyclin‑A2, which is downregulated following birth, has previously been established as a key regulator of the cell cycle. The present study aimed to detect the effects of cyclin‑A2 on myocardial cells by using recombinant adeno‑associated virus 9 (rAAV9). Sixty mice were selected and randomly divided into two groups (n=30). The control group were injected with saline and the experimental group were transfected with the rAAV9‑cyclinA2‑CMV vector by intravenous injection into the tail vein. Tissues were harvested at two and four weeks following injection. Cyclin‑A2 expression levels and localization were evaluated using western blot and immunohistochemical analyses. DNA synthesis and mitosis in the myocardium were confirmed by analyzing proliferating cell nuclear antigen (PCNA) and phospho‑histone H3 (H3P) expression levels. Expression of Cyclin‑A2 in the myocardium commenced two weeks following tail vein injection in the cyclin‑A2‑treated group, while no expression was observed in the control group. Four weeks following injection, expression levels of cyclin‑A2 were higher than those observed at two weeks following injection into the myocardium (two weeks: 0.146±0.013 vs. 27.1±3.33%, P<0.001; four weeks: 0.142±0.107 vs. 74.4±3.36%, P<0.001). PCNA displayed increased expression levels in the cyclin‑A2‑treated group (two weeks: 13.1±0.54 vs. 65.8±3.44%, P<0.001; four weeks: 13.2±0.55 vs. 71.2±1.58%, P<0.001); however, no change was observed in those of the control group. By contrast, no significant difference was observed in mitosis marker H3P expression levels between the two groups. Immunohistochemical analysis of cyclin‑A2 indicated cytoplasmic, but not nuclear, localization. cyclin‑A2 and PCNA expression levels in the liver, lung and kidney showed no significant difference between the two groups (P>0.05). It was therefore concluded that the delivery of cyclin‑A2 via rAAV9 to the mouse myocardium restarted the myocardial cell cycle, thereby establishing steady and specific expression in the myocardium. Furthermore, the effect of Cyclin‑A2 on the myocardium may provide a novel method for achieving cardiac regeneration following cardiac injury.

Reduced graphene oxide upconversion nanoparticle hybrid for electrochemiluminescent sensing of a prognostic indicator in early-stage cancer

Upconversion nanoparticles (UCNPs) have been proposed as a promising new class of biological luminescent labels because of their weak auto-fluorescence background, strong penetration ability under near-infrared (NIR) radiation, resistance to photobleaching, and low toxicity. Although UCNPs hold great promise in nanotechnology and nanomedicine, their applications in ECL fields still remain unexplored. Herein, a label-free, ultra-sensitive and selective electrochemiluminescence (ECL) assay is developed for detection of cyclin A2 by using highly efficient ECL graphene-upconversion hybrid. Being an important member of the cyclin family, cyclin A2 is involved in the initiation of DNA replication, transcription and cell cycle reg-ulation through the association of cyclin-dependent kinases (CDK). Cyclin A2 is a prognostic indicator in early-stage cancers and a target for treatment of different types of cancers. However, the expression level of cyclin A2 is quite low, direct detection of cyclin A2 in crude cancer cell extracts is challenging and important for both clinical diagnosis of cancer in the early stage and the treatment. By chemically grafting cyclin A2 detection specific probe, a PEGlyted hexapeptide, to graphene-upconversion hybrid, the constructed ECL biosensor displays a superior performance for cyclin A2 , which can not only detect cyclin A2 directly in cancer cell extracts, but also discriminate between normal cells and cancer cells. More importantly, the ECL biosensor has different responses between clinical used anticancer drug-treated and non-treated cancer cells, which demonstrates that the sensor can be potentially used for drug screening, and for evaluation of therapeutic treatments in early-stage cancers.

The inhibitory role of Mir-29 in growth of breast cancer cells

Mir-29 microRNA families are involved in regulation of various types of cancers. Although Mir-29 was shown to play an inhibitory role in tumorigenesis, the role of Mir-29 in breast cancer still remains obscure. In this study, we showed that Mir-29a is the dominant isoform in its family in mammary cells and expression of Mir-29a was down-regulated in different types of breast cancers. Furthermore, over-expression of Mir-29a resulted in significant slower growth of breast cancer cells and caused higher percentage of cells at G0/G1 phase. Consistent with this over-expression data, knockdown of Mir-29a in normal mammary cells lead to higher cell growth rate, and higher percentage of cells entering S phase. We further found that Mir-29a negatively regulated expression of B-Myb, which is a transcription factor associated with tumorigenesis. The protein levels of Cyclin A2 and D1 are consistent with the protein level of B-Myb. Taken together, our data suggests Mir-29a plays an important role in inhibiting growth of breast cancer cells and arresting cells at G0/G1 phase. Our data also suggests that Mir-29a may suppress tumor growth through down-regulating B-Myb.

Quantitative trait locus linkage analysis in a large Amish pedigree identifies novel candidate loci for erythrocyte traits

We characterized a large Amish pedigree and, in 384 pedigree members, analyzed the genetic variance components with covariate screen as well as genome-wide quantitative trait locus (QTL) linkage analysis of red blood cell count (RBC), hemoglobin (HB), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), platelet count (PLT), and white blood cell count (WBC) using SOLAR. Age and gender were found to be significant covariates in many CBC traits. We obtained significant heritability estimates for RBC, MCV, MCH, MCHC, RDW, PLT, and WBC. We report four candidate loci with Logarithm of the odds (LOD) scores above 2.0: 6q25 (MCH), 9q33 (WBC), 10p12 (RDW), and 20q13 (MCV). We also report eleven candidate loci with LOD scores between 1.5 and <2.0. Bivariate linkage analysis of MCV and MCH on chromosome 20 resulted in a higher maximum LOD score of 3.14. Linkage signals on chromosomes 4q28, 6p22, 6q25, and 20q13 are concomitant with previously reported QTL. All other linkage signals reported herein represent novel evidence of candidate QTL. Interestingly rs1800562, the most common causal variant of hereditary hemochromatosis in HFE (6p22) was associated with MCH and MCHC in this family. Linkage studies like the one presented here will allow investigators to focus the search for rare variants amidst the noise encountered in the large amounts of data generated by whole-genome sequencing.

Expression of cyclin A, B1 and D1 after induction of cell cycle arrest in the Jurkat cell line exposed to doxorubicin

Jurkat human lymphoblastoid cells were incubated in increasing concentrations of doxorubicin (0.05, 0.1 and 0.15 μM) to induce cell death, and their expression of cyclin A, B1 and D1 was evaluated by flow cytometry (cell cycle progression, Annexin V assay, percentages and levels of each of the cyclins), transmission electron microscopy (ultrastructure) and confocal fluorescence microscopy (expression and intracellular localization of cyclins). After low-dose doxorubicin treatment, Jurkat cells responded mainly by G2/M arrest, which was related to increased cyclin B1, A and D1 levels, a low level of apoptosis and/or mitotic catastrophe. The influence of doxorubicin on levels and/or localization of selected cyclins was confirmed, which may in turn contribute to the G2/M arrest induced by the drug.

Aptamer-capped multifunctional mesoporous strontium hydroxyapatite nanovehicle for cancer-cell-responsive drug delivery and imaging

A novel cancer-cells-triggered controlled-release gadolinium-doped luminescent and mesoporous strontium hydroxyapatite nanorods (designated as Gd:SrHap nanorods) system using cell-type-specific aptamers as caps has been constructed. Aptamers behave as a dual-functional molecule that acts as not only a lid but also a targeted molecular that can be used in an effective way for therapeutically special cancer cells. After incubated with cancer cells, for example, MCF-7 cells, the doxorubicin-loaded and aptamer-capped Gd:SrHap nanorods (designated as Gd:SrHap-Dox-aptamer) can be internalized into MCF-7 cells, resulting in the pore opening and drug releasing. Furthermore, the high biocompatibility and biodegradability Gd:SrHap nanorods with blue autofluorescence and paramagnetism could serve as a good contrast agent of targeting fluorescence and magnetic resonance imaging. We envision that this Gd:SrHap system could play a significant role in developing new generations of site-selective, controlled-release delivery and interactive sensory nanodevices.

Repositioning antimicrobial agent pentamidine as a disruptor of the lateral interactions of transmembrane domain 5 of EBV latent membrane protein 1

The lateral transmembrane protein-protein interactions (PPI) have been regarded as "undruggable" despite their importance in many essential biological processes. The homo-trimerization of transmembrane domain 5 (TMD-5) of latent membrane protein 1 (LMP-1) is critical for the constitutive oncogenic activation of the Epstein-Barr virus (EBV). Herein we repurpose the antimicrobial agent pentamidine as a regulator of LMP-1 TMD-5 lateral interactions. The results of ToxR assay, tryptophan fluorescence assay, courmarin fluorescence dequenching assay, and Bis-Tris sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) consistently show pentamidine disrupts LMP-1 TMD-5 lateral interactions. Furthermore, pentamidine inhibits LMP-1 signaling, inducing cellular apoptosis and suppressing cell proliferation in the EBV infected B cells. In contrast, EBV negative cells are less susceptible to pentamidine. This study provides a novel non-peptide small molecule agent for regulating LMP-1 TMD-5 lateral interactions.

Effects of long and short carboxylated or aminated multiwalled carbon nanotubes on blood coagulation

In this work the effects of four different multiwalled carbon nanotubes (MWCNTs), including long carboxylated (L-COOH), short carboxylated (S-COOH), long aminated (L-NH₂) and short aminated (S-NH₂) ones, on the integrity of red blood cells, coagulation kinetics and activation of platelets were investigated with human whole blood. We found that the four MWCNTs induced different degrees of red blood cell damage as well as a mild level of platelet activation (10–25%). L-COOH and L-NH₂ induced a higher level of platelet activation than S-COOH and S-NH₂ respectively; meanwhile L-NH₂ caused marked reductions in platelet viability. The presence of the four MWCNTs led to earlier fibrin formation, L-NH₂ increased the clots hardness significantly, while L-COOH and S-NH₂ made the clots become softer. It was concluded that the four MWCNTs affected blood coagulation process and the clots mechanical properties; they also altered the integrity of the red blood cells and the viability of the platelets, as well as induced platelets activation. The effects of MWCNTs depended on the size and chemistry of the nanotubes and the type of cells they contacted.

Mesoporous silica nanoparticle-based H2O2 responsive controlled-release system used for Alzheimer's disease treatment

Metal ions play important roles in amyloid aggregation and neurotoxicity. Metal-ion chelation therapy has been used in clinical trials for Alzheimer's disease (AD) treatment. However, clinical trial studies have shown that long-term use of metal chelator can cause adverse side effect, subacute myelo-optic neuropathy. Nanoparticle engineering processes have become promising approaches for efficiently drugs delivery. A series of modified mesoporous silica nanoparticles (MSNs) using redox, pH, competitive binding, light, and enzyme as actuators have been demonstrated. Recently, significant advances in sensing oxidative stress have been made by taking advantage of specific chemistry between cellular oxidants such as H(2) O(2) . Here we report a biocompatible delivery platform by using H(2) O(2) responsive controlled-release system to realize target delivery of AD therapeutic metal chelator. The advantage of this novel strategy is that metal chelator can only be released by the increased levels of H(2) O(2) , thus, it would not interfere with the healthy metal homeostasis and can overcome strong side effect of metal chelator after long-term use. By taking advantage of the good biocompatibility, cellular uptake properties, and efficient intracellular release of metal chelators, the delivery system is promising for future in vivo controlled-release biomedical applications.

Induction of apoptosis and cell cycle arrest by pericarp polyphenol-rich extract of Baneh in human colon carcinoma HT29 cells

Plants as important source of natural active components with anticancer effects commonly are different in structure and biological properties. The pericarp of Pistacia atlantica sub kurdica with local name of Baneh, a rich source of active phytochemicals, contains noticeable amounts of polyphenolic compounds, flavonoids and anthocyanins. Therefore, the antiproliferative, apoptosis induction and cell cycle alterations of Baneh were evaluated in human colon carcinoma HT29 cells. The Baneh extract (0.7 mg/ml) resulted in 50% growth inhibition similar to 500 nM of Doxorubicin (Dox) in HT29 cells after 72 h. The down-regulation of cyclin A protein by Baneh extract induced S phase delay in cell cycle progression of HT29 cells. Unlike the Baneh extract, Dox showed G2/M accumulation of HT29 cells which was associated with an increase in cyclin A and cyclin B1 protein expression. Furthermore, the induction of apoptosis following Baneh extract and Dox treatment in HT29 cells was confirmed by DNA fragmentation and translocation of phosphatidylserine. The morphological characteristics of apoptosis were also observed in HT29 cells exposed to the Baneh extract and Dox. These results suggest that due to the existence of bioactive components, methanolic extract of the Baneh has significant cytotoxic effects against human colon carcinoma HT29 cells.

Coformulation of doxorubicin and curcumin in poly(D,L-lactide-co-glycolide) nanoparticles suppresses the development of multidrug resistance in K562 cells

Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic used to treat a variety of cancers including leukemia. Chronic myeloid leukemia (CML) blasts like K562 cells are resistant to apoptosis induced by DOX due to several reasons, the primary being the sequestration of drug into cytoplasmic vesicles and induction of multidrug resistance (MDR) gene expression with DOX treatment resulting in intracellular resistance to this drug. Moreover, expression of antiapoptotic protein BCL-2 and the hybrid gene bcr/abl in K562 cells contributes resistance to DOX. Studies have shown that curcumin (CUR) has a pleiotropic therapeutic effect in cancer treatment, as it is an inhibitor of nuclear factor kappa B (NFκB) as well as a potent downregulator of MDR transporters. In this study, we investigated the potential benefit of using DOX and CUR in a single nanoparticle (NP) formulation to inhibit the development of drug resistance for the enhancement of antiproliferative activity of DOX in K562 cells. Results illustrate that the dual (DOX+CUR) drug loaded NPs were effectively delivered into K562 cells. CUR not only facilitates the retention of DOX in nucleus for a longer period of time but also inhibits the gradual expression of MDR1 and BCL-2 at the mRNA level in K562 cells. Moreover, Western blot results confirm that in combination both of the drugs were capable of inducing apoptosis even if in a lower concentration compared to either single drug in both solution or in formulation. Combinational therapy by using DOX and CUR, especially when administered in the NP formulation, has enhanced the cytotoxicity in K562 cells by promoting the apoptotic response. Overall, this combinational strategy has significant promise in the clinical management of intractable diseases, especially leukemia.

A graphene functionalized electrochemical aptasensor for selective label-free detection of cancer cells

Here we report an electrochemical sensor that can realize label-free cancer cell detection using the first clinical trial II used aptamer AS1411 and functionalized graphene. By taking advantages of AS1411 high binding affinity and specificity to the overexpressed nucleolin on the cancer cell surface, our developed electrochemical aptasensor can distinguish cancer cells and normal ones and detect as low as one thousand cells. With DNA hybridization technique, this E-DNA sensor can be regenerated and reusable for cancer cell detection. Our work gives a good example for label-free cancer cell detection based on aptamer and graphene-modified electrode.