Reporter gene systems for the identification and characterization of cancer stem cells

Cancer stem cells(CSCs)are tumor cells that share functional characteristics with normal and embryonic stem cells.CSCs have increased tumor-initiating capacity and metastatic potential and lower sensitivity to chemo-and radiotherapy,with important roles in tumor progression and the response to therapy.Thus,a current goal of cancer research is to eliminate CSCs,necessitating an adequate phenotypic and functional characterization of CSCs.Strategies have been developed to identify,enrich,and track CSCs,many of which distinguish CSCs by evaluating the expression of surface markers,the initiation of specific signaling pathways,and the activation of master transcription factors that control stemness in normal cells.We review and discuss the use of reporter gene systems for identifying CSCs.Reporters that are under the control of aldehyde dehydrogenase 1A1,CD133,Notch,Nanog homeobox,Sex-determining region Y-box 2,and POU class 5 homeobox can be used to identify CSCs in many tumor types,track cells in real time,and screen for drugs.Thus,reporter gene systems,in combination with in vitro and in vivo functional assays,can assess changes in the CSCs pool.We present relevant examples of these systems in the evaluation of experimental CSCs-targeting therapeutics,demonstrating their value in CSCs research.

Alpha-fetoprotein-targeted reporter gene expression imaging in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers in Eastern Asia, and its incidence is increasing globally. Numerous experimental models have been developed to better our understanding of the pathogenic mechanism of HCC and to evaluate novel therapeutic approaches. Molecular imaging is a convenient and up-to-date biomedical tool that enables the visualization, characterization and quantification of biologic processes in a living subject. Molecular imaging based on reporter gene expression, in particular, can elucidate tumor-specific events or processes by acquiring images of a reporter gene’s expression driven by tumor-specific enhancers/promoters. In this review, we discuss the advantages and disadvantages of various experimental HCC mouse models and we present in vivo images of tumor-specific reporter gene expression driven by an alpha-fetoprotein (AFP) enhancer/promoter system in a mouse model of HCC. The current mouse models of HCC development are established by xenograft, carcinogen induction and genetic engineering, representing the spectrum of tumor-inducing factors and tumor locations. The imaging analysis approach of reporter genes driven by AFP enhancer/promoter is presented for these different HCC mouse models. Such molecular imaging can provide longitudinal information about carcinogenesis and tumor progression. We expect that clinical application of AFP-targeted reporter gene expression imaging systems will be useful for the detection of AFP-expressing HCC tumors and screening of increased/decreased AFP levels due to disease or drug treatment.

Red fluorescent protein (DsRed2), an ideal reporter for cotton genetic transformation and molecular breeding

Genes encoding reporter proteins are used as visual marker-assisted tools in genetic transformation as well as plant breeding. In this study, the red fluorescent protein identified in Discosoma sp. coral(DsRed2) was successfully used as a visual marker for cotton genetic engineering. DsRed2 was successfully expressed in two cotton cultivars,JIN668 and YZ1, driven by the Ca MV-35 S promoter via the Agrobacterium-mediated transformation. Our results suggest that DsRed2 expression provides an early-stage selection tool for the transgenic calli via visual observation. Red fluorescence can be detected not only in callus and somatic embryos but also in most tissues and organs of mature plants. The transgenic line Yz-2-DsRed2 was crossed with four different cotton cultivars to assess the transgene heritability and stability in different genetic backgrounds.The heritability of the red color was highly stable when Yz-2-DsRed2 was used as a male parent. The DsRed2 gene expressed 100% in the F_1 hybrids. To investigate the relationship between DsRed2 transcription and DNA methylation, a methylation-specific PCR approach was applied to the Ca MV-35 S promoter region. The results showed a negative association between DNA methylation level in the promoter region and the transgene transcription.Taken together, these findings suggest DsRed2 a visual reporter gene for cotton genetic transformation and molecular breeding programs.

Construction and Identification of the Adenoviral Vector with Dual Reporter Gene for Multimodality Molecular Imaging

Summary： In this study, the recombinant adenovirus （Ad） vector containing dual reporter gene [i.e. human transferrin receptor gene （TFRC） and firefly luciferase reporter gene] was constructed to provide a novel experimental tool for magnetic resonance （MR） and bioluminescence dual-modality molecular imaging. The cDNA of TFRC was amplified by polymerase chain reaction （PCR） and cloned into the multiple cloning site of pShuttle-CMV-CMV-Luciferase vector. After identification by Sfi I digestion and sequencing, pShuttle-TFRC-Luciferase vector and the adenoviral backbone vector （pAdeno） were subjected to homologous recombination. The correct recombinant plasmid was then transfected into 293 packaging cells to produce adenoviral particles and confirmed by PCR. After infection of human colo- rectal cancer LOVO cells with Ad-TFRC-Luciferase, the expressions of transferrin receptor （TfR） and luciferase protein were detected respectively by Western blotting and bioluminescence imaging in vitro. The results showed that TFRC gene was successfully inserted into the adenoviral shuttle vector carrying luciferase gene. DNA sequence analysis indicated that the TFRC gene sequence in the shuttle plasmid was exactly the same as that reported in GenBank. The recombinant plasmid was identified correct by restriction digestion. Ad-TFRC-Luciferase recombinant adenovirns was constructed successfully, and the virus titer was 1.6x10^10 pfu/mL. Forty-eight h after dual reporter gene transfection, the expressions of TfR and luciferase protein were increased significantly （P〈0.01）. It was concluded that the recombinant adenovirus vector with dual reporter gene was successfully established, which may be used for in vivo tracing target cells in multimodality imaging.

VISUALIZATION OF HEAD AND NECK CANCER MODELS WITH A TRIPLE FUSION REPORTER GENE

The development of experimental animal models for head and neck tumors generally rely on the biol uminescence imaging to achieve the dynamic monitoring of the tumor growth and metastasis due to the complicated anatomical structures.Since the bioluminescence imaging is largely affected by the intracellular luciferase expression level and external D-luciferin concentrations,its imaging accuracy requires further confirmation.Here,a new triple fusion reportelr gene,which consists of a herpes simplex virus type 1 thymidine kinase(TK)gene for radioactive imaging,a far-red fuorescent protein(mLumin)gene for fuorescent imaging,and a firefly luciferase gene for bioluminescence imaging,was introduced for in vrivo observation of the head and neck tumors through multi-modality imaging.Results show that fuorescence and bioluminescence signals from mLumin and luciferase,respectively,were clearly observed in tumor cells,and TK could activate suicide pathway of the cells in the presence of nucleotide analog-ganciclovir(GCV),demonstrating the effecti veness of individual functions of each gene.Moreover,subcutaneous and metastasis animal models for head and neck tumors using the fusion reporter gene-expressing cell lines were established,allowing multi-modality imaging in vio.Together,the established tumor models of head and neck cancer based on the newly developed triple fusion reporter gene are ideal for monitoring tumor growth,assessing the drug therapeutic efficacy and verifying the effec-tiveness of new treatments.

Broad Hormonal Responses Induced by Aluminum in Roots of Dwarf Transgenics of Solanum lycopersicum L. cv “Micro-Tom”

The spatial pattern distribution of plant hormones in response to aluminum (Al) toxicity in roots remains to be shown. This study was performed to assess the root hormonal accumulation and gene expression in response to Al toxicity in five transgenic miniature dwarf tomatoes cv. Micro-Tom (MT). MT and MT transgenics to acid indole acetic, cytokinin, gibberellin, abscisic acid and ethylene were cultivated in nutrient solutions containing different Al concentrations. Root growth elongation was measured and cellular damage was visualized by staining Evans’s blue. The GUS reporter gene staining technique was used to visualize hormonal changes in MT apex root tissues. Data indicated that the MT is sensitive to Al that induced significant growth inhibition and cellular damage. Al concentration of 27 μM was significantly toxic, inducing root apex darkening and inhibition of root development. The qualitative evaluation of GUS reporter gene expression showed intense crosstalk among all hormones studied, underscoring the complexity of signaling induced by Al in apex roots. Results point out to a major understanding of the hormonal signaling in response to Al toxicity, which may induce a change of root growth and architecture with growth inhibition and cell constraints modulated by all different hormones evaluated.

Study on the regulatory effect of liver X receptor in HEK293 cells by six main diterpene esters in Semen Euphorbiae

Background:To study the effects of the main diterpene esters in Euphorbia factor L_(1),L_(2),L_(3),L_(7a),L_(7b)and L_(8)on the transcriptional activity and protein expression of liver X receptor(LXR).Methods:The effect of the main diterpene ester components in Semen Euphorbiae on the viability of HEK293 cells were studied by MTT assay.The LXR-Luc plasmid vector was transfected into HEK293 cells and treated with Euphorbia factor L_(1),L_(2),L_(3),L_(7a),L_(7b)and L_(8)for 24 h.The effect of the main diterpene ester components of Semen Euphorbiae on LXR-Luc luciferase activity was investigated by dual luciferase reporter gene system,and the expression of LXRαprotein was detected by Western Blot.Results:Euphorbia factor L_(1),L_(2),L_(3),L_(7a),L_(7b)and L_(8)could significantly reduce the relative luciferase activity(RLU)of LXRα,and the expression level of LXRαprotein was significantly down-regulated.Conclusion:Euphorbia factor L_(1),L_(2),L_(3),L_(7a),L_(7b)and L_(8)can inhibit the expression of LXR protein level,which may be achieved by inhibiting the transcriptional activity of LXR.

Identification of a Regulatory Single Nucleotide Polymorphism in the Adiponectin (APM1) Gene Associated with Type 2 Diabetes in Han Nationality

Objective To identify the genetic defects of the the adiponectin （APM1） gene that contribute to the development of type 2 diabetes （T2DM） and determine the functional single nucleotide polymorphisms （SNPs） in the APMI gene associated with T2DM in Han nationality. Methods The APMI gene 5＇-UTR was screened by direct sequencing to identify common polymorphisms. Identified SNPs were genotyped in 585 nondiabetic controls, 278 subjects with impaired glucose intolerance （IGT） and 212 patients with T2DM. The functions of SNPs in the regulatory region were assessed by reporter gene assay. Possible association between SNPs and plasma APMI levels or metabolic parameters was statistically asses,sed. Results Three SNPs were identified in the APMI gene 5＇-UTR. A case-control study revealed that SNP -11377 G/C had significant differences in allele frequencies between T2DM patients and nondiabetic controls （G 0.314/C 0.686 vs. G 0.265/C 0.735, P=0.03）. Haplotype analysis of three SNPs in the APM1 gene showed that no significant association of haplotypes with T2DM. IGT was detected in the present study. Reporter gene assay showed that SNP did not influence the transcription efficiency in the 3T3-LI cell line. Conclusion SNP - 11377 G/C in the proximal promoter region of the APM 1 gene contributes to the development of T2DM in Han nationality but may not be a functional SNP in the APM1 gene.

Improvement of Chemically-activated Luciferase Gene Expression Bioassay for Detection of Dioxin-Iike Chemicals

Objective To improve the chemically-activated luciferase expression (CALUX)bioassay for detection of dioxin-like chemicals (DLCs) based on the toxicity mechanisms ofDLCs. Method A recombinant vector was constructed and used to transfect humanhepatoma (HepG2). The expression of this vector was 10-100 folds higher than that of pGL2used in previous experiments. The transfected cells showed aromatic hydrocarbon receptor(AhR)-meditated luciferase gene expression. The reliability of luciferase induction in thiscell line as a reporter of AhR-mediated toxicity was evaluated, the optimal detection timewas examined and a comparison was made by using the commonly used ethoxyresoufin-O-deethylase (EROD) activity induction assay. Result The results suggested that theluciferase activity in recombinant cells was peaked at about 4 h and then decreased to astable activity by 14 h after TCDD treatment. The detection limit of this cell line was0.11pmol/L, or 10-fold lower than in previous studies, with a linear range from 1 to 100pmol/L, related coefficient of 0.997, and the coefficient of variability (CV) of 15-30%.Conclusion The luciferase induction is 30-fold more sensitive than EROD induction, thedetection time is 68 h shorter and the detection procedure is also simpler.

Effects of CMV Enhancer on Activity and Specificity of Bovine MyoG Gene Promoter

Connected a segment of CMV enhancer to the front of MyoG gene promoter and then constructed the corresponding dual luciferase expression vector pGL3-CMV-MyoGpro. We set four eukaryotic expression vectors including pGL3-CMV, pGL3MyoGpro, pGL3-CMV-MyoGpro, and pGL3-Basic which contained CMV promoter, MyoG promoter, CMV-MyoG synthesis promoter, and a promoterless negative control, respectively. Then the four vectors and internal control Renilla luciferase report gene vector phRL-TK were transfected into bovine skeletal muscle satellite cells, mouse C2C12 cells and bovine fetal fibroblast cells to detect the promoter activity with dual luciferase report system. The results showed that CMV enhancer could significantly improve the transcription activity of bovine MyoG gene promoter in muscle satellite cells and mouse C2C12 cells, and it had certain specificity. This study provided experimental materials for increasing the high expression of exogenous gene in bovine muscle cells, and also laid the molecular theoretical basis for obtaining the high specific promoter of bovine muscle and the transgenic beef cattle.

Immediate-early Inducible Function in Upstream Region of junB Gene

Objective To analyze the upstream region of radiation-induced junB gene. Methods Four plasmids containing 250 bp, 590 bp, 900 bp and 1650 bp, and CAT reporter gene were constructed separately and introduced to L8704 cells. The cells were irradiated with 2 Gy X-rays and incubated at different intervals. Total RNA was extracted from the cells and fluctuation of the CAT mRNA level was assessed by the RNA ratio of CAT/β-actin measured by quantitative Northern blot hybridization. Results CAT mRNA expression containing 900 bp and 1560 bpjunB promoter remarkably and rapidly increased, and reached its peak 30min after 2 Gy X-my irradiation. Conclusions 590-900 bp fragments located in the upstream region of junB gene play an important role in the early process of cells against radiation.

Effect of the C.–1388 A>G polymorphism in chicken heat shock transcription factor 3 gene on heat tolerance

Heat stress is one of the main factors that inlfuence poultry production. Heat shock proteins (HSPs) are known to affect heat tolerance. The formation of HSPs is regulated by heat shock transcription factor 3 (HSF3) in chicken. A DNA pool was established for identifying single nucleotide polymorphisms (SNPs) of the chicken HSF3, and 13 SNPs were detected. The bioinformatic analysis showed that 8 SNPs had the capacity to alter the transcription activity of HSF3. The dual luciferase report gene assay showed that there was a signiifcant difference (P<0.01) in the Firelfy luciferase/Renil a luciferase ratio (F/R) of C.–1 703 A>G (S1) and C.–1 388 A>G (S4) sites at the 5′-untranslated region (UTR) of chicken HSF3. The elec-trophoretic mobility shift assay showed that the S4 site was a transcription binding factor. The analysis of the association of the S1 and S4 sites with heat tolerance index revealed that the S4 site was signiifcantly correlated with the CD3+T cel , corticosterone, and T3 levels in Lingshan chickens and with the heterophil/lymphocyte value in White Recessive Rock. These results showed that the S4 site at the 5′ UTR of chicken HSF3 might have an impact on heat tolerance in summer and could be used as a potential marker for the selection of chicken with heat tolerance in the future.

Impact of Pitx3 gene knockdown on glial cell line-derived neurotrophic factor transcriptional activity in dopaminergic neurons

Pitx3 is strongly associated with the phenotype, differentiation, and survival of dopaminergic neurons. The relationship between Pitx3 and glial cell line-derived neurotrophic factor（GDNF） in dopaminergic neurons remains poorly understood. The present investigation sought to construct and screen a lentivirus expression plasmid carrying a rat Pitx3 short hairpin（sh）RNA and to assess the impact of Pitx3 gene knockdown on GDNF transcriptional activity in MES23.5 dopaminergic neurons. Three pairs of interference sequences were designed and separately ligated into GV102 expression vectors. These recombinant plasmids were transfected into MES23.5 cells and western blot assays were performed to detect Pitx3 protein expression. Finally, the most effective Pitx3 sh RNA and a dual-luciferase reporter gene plasmid carrying the GDNF promoter region（GDNF-luciferase） were cotransfected into MES23.5 cells. Sequencing showed that the synthesized sequences were identical to the three Pitx3 interference sequences. Inverted fluorescence microscopy revealed that the lentivirus expression plasmids carrying Pitx3-sh RNA had 40-50% transfection efficiency. Western blot assay confirmed that the corresponding Pitx3 of the third knockdown sequence had the lowest expression level. Dual-luciferase reporter gene results showed that the GDNF transcriptional activity in dopaminergic cells cotransfected with both plasmids was decreased compared with those transfected with GDNF-luciferase alone. Together, the results showed that the designed Pitx3-sh RNA interference sequence decreased Pitx3 protein expression, which decreased GDNF transcriptional activity.

Establishment of FAP-overexpressing Cells for FAP-targeted Theranostics

Objective Fibroblast activation protein(FAP)has been widely studied and exploited for its clinical applications.One of the difficulties in interpreting reports of FAP-targeted theranostics is due to the lack of accurate controls,making the results less specific and less confirmative.This study aimed to establish a pair of cell lines,in which one highly expresses FAP(HT1080-hFAP)and the other has no detectable FAP(HT1080-vec)as control,to accurately evaluate the specificity of the FAP-targeted theranostics in vitro and in vivo.Methods The cell lines of the experimental group(HT1080-hFAP)and no-load group(HT1080-vec)were obtained by molecular construction of the recombinant plasmid pIRES-hFAP.The expression of hFAP in HT1080 cells was detected by PCR,Western blotting and flow cytometry.CCK-8,Matrigel transwell invasion assay,scratch test,flow cytometry and immunofluorescence were used to verify the physiological function of FAP.The activities of human dipeptidyl peptidase(DPP)and human endopeptidase(EP)were detected by ELISA in HT1080-hFAP cells.PET imaging was performed in bilateral tumor-bearing nude mice models to evaluate the specificity of FAP.Results RT-PCR and Western blotting demonstrated the mRNA and protein expression of hFAP in HT1080-hFAP cells but not in HT1080-vec cells.Flow cytometry confirmed that nearly 95%of the HT1080-hFAP cells were FAP positive.The engineered hFAP on HT1080 cells had its ability to retain enzymatic activities and a variety of biological functions,including internalization,proliferation-,migration-,and invasion-promoting activities.The HT1080-hFAP xenografted tumors in nude mice bound and took up^(68)GA-FAPI-04 with superior selectivity.High image contrast and tumor-organ ratio were obtained by PET imaging.The HT1080-hFAP tumor retained the radiotracer for at least 60 min.Conclusion This pair of HT1080 cell lines was successfully established,making it feasible for accurate evaluation and visualization of therapeutic and diagnostic agents targeting the hFAP.

Involvement of cAMP in ABA Signal Transduction in Tobacco Suspension Cells

Abscisic acid (ABA) plays an important role in plant growth and developmental processes. Although some ABA signal molecules, such as cADPR, Ca2+, etc., have been reported, there. was no evidence proving the involvement of cAMP in A-B-A, signal transduction. In this present study, the constructed gene ( rd29A-GUS) was transformed into Nicotiana tabacum, and calli was induced from the transgenic plant. The suspension cells obtained from the callus grew well and uniformly. Treatment of the suspension cells with ABA led to an increase in GUS activity, indicating that these transgenic suspension cells are useful for the study of ABA signaling. Addition of nicotinamide (cADPR inhibitor) or U-73122 (phospholiphase C inhibitor) could only partially inhibit the increase of GUS activity elicited by ABA. The inhibitory effect of nicotinamide was enhanced by application of K252a (inhibitor of protein kinase). Treatment of the suspension cells with 8-Br-cAMP, a membrane-permeable analogue of cAMP, could partially replace the effect of ABA. Furthermore, intracellular addition of IBMX (phosphodiesterase inhibitor) mimicked die effect of exogenous cAMP on the deduction of expression of rd29A promoter. These results suggested that cAMP was an important messenger in ABA signal transduction in tobacco suspension cell.

The involvement of p38 MAPK in transforming growth factor β1-induced apoptosis in murine hepatocytes

We reported in this manuscript that TGF-beta1 induces apoptosis in AML12 murine hepatocytes, which is associated with the activation of p38 MAPK signaling pathway. SB202190, a specific inhibitor of p38 MAPK, strongly inhibited the TGF-beta1-induced apoptosis and PAI-1 promoter activity. Treatment of cells with TGF-beta1 activates p38. Furthermore, over-expression of dominant negative mutant p38 also reduced the TGF-beta1-induced apoptosis. The data indicate that the activation of p38 is involved in TGF-beta1-mediated gene expression and apoptosis.

Protective mechanisms of micro RNA-27a against oxygen-glucose deprivation-induced injuries in hippocampal neurons

Hypoxic injuries during fetal distress have been shown to cause reduced expression of micro RNA-27a（mi R-27a）,which regulates sensitivity of cortical neurons to apoptosis.We hypothesized that miR-27 a overexpression attenuates hypoxia- and ischemia-induced neuronal apoptosis by regulating FOXO1,an important transcription factor for regulating the oxidative stress response.miR-27 a mimic was transfected into hippocampal neurons to overexpress miR-27 a.Results showed increased hippocampal neuronal viability and decreased caspase-3 expression.The luciferase reporter gene system demonstrated that mi R-27 a directly binded to FOXO1 3′UTR in hippocampal neurons and inhibited FOXO1 expression,suggesting that FOXO1 was the target gene for mi R-27 a.These findings confirm that mi R-27 a protects hippocampal neurons against oxygen-glucose deprivation-induced injuries.The mechanism might be mediated by modulation of FOXO1 and apoptosis-related gene caspase-3 expression.

Genistein modulates MMP-26 and estrogen receptor expression in endometrial cancer cells

Objective:To explore the mechanism of the estrogen-like effect of genistein by observing the expression of Matrix metalloproteinases-26(MMP-26)and ERa in human endometrial cancer cells(Ishikawa and HEC-1B)in vitro.Methods:The effect of genistein on MMP-26 and ERa expression was examined by western blot in cultured Ishikawa and HEC-1B cells.Additionally,the effects of genistein on ERa-ERE-luc and ERb-ERE-luc reporter gene expression in HEC-1B cells were analyzed by luciferase activity assays.Results:MMP-26 and ERa protein expression was down-regulated by genistein treatment in Ishikawa cell induced by high concentration E2,whereas MMP-26 and ERa protein expression was up-regulated by genistein treatment in Ishikawa cells induced by low concentration E2.Expression of the ERa-ERE-luc and ERb-ERE-luc reporter genes was significantly increased after E2 induction and was further up-regulated by genistein.Expression of ERa-ERE-luc and ERb-ERE-luc reporter genes decreased significantly following genistein treatment in high E2 concentrations,and increased significantly following genistein treatment in low E2 concentrations.Conclusions:Genistein showed estrogen-like effects in endometrial cancer cells and influenced estrogen receptor signaling by modulating ERa and ERb expression.

A reporter gene assay for determining the biological activity of therapeutic antibodies targeting TIGIT

T cell immunoglobulin and ITIM domain(TIGIT)is a novel immune checkpoint that has been considered as a target in cancer immunotherapy.Current available bioassays for measuring the biological activity of therapeutic antibodies targeting TIGIT are restricted to mechanistic investigations because donor primary T cells are highly variable.Here,we designed a reporter gene assay comprising two cell lines,namely,CHO-CD112-CD3 scFv,which stably expresses CD 112(PVRL2,nectin-2)and a membranebound anti-CD3 single-chain fragment variable(scFv)as the target cell,and Jurkat-NFAT-TIGIT,which stably expresses TIGIT as well as the nuclear factor of activated T-cells(NFAT)response element-controlled luciferase gene,as the effector cell.The anti-CD3 scFv situated on the target cells activates Jurkat-NFATTIGIT cells through binding and crosslinking CD3 molecules of the effector cell,whereas interactions between CD 112 and TIGIT prevent activation.The presence of anti-TIGIT mAbs disrupts their interaction,which in turn reverses the inactivation and luciferase expression.Optimization and validation studies have demonstrated that this assay is superior in terms of specificity,accuracy,linearity,and precision.In summary,this reliable and effective reporter gene assay may potentially be utilized in lot release control,stability assays,screening,and development of novel TIGIT-targeted therapeutic antibodies.

Resistin does not down-regulate the transcription of insulin receptor promoter

Objective: To detect the effect of resistin on the transcription of insulin receptor promoter. Methods: Luciferase reporter gene was fused downstream of human insulin receptor promoter and the enzymatic activity of luciferase was determined in the presence or absence of resistin. The resistin expressed with plasmid was stained with antibody against Myc tag which was in frame fused with resistin coding sequence, and then imaged with confocal microscopy. Results: The treatment of pIRP-LUC transfected cells with recombinant resistin did not result in significant difference in the enzymatic activity of luciferase compared to the untreated cells. Cell staining showed that green fluorescence could be observed in the cytoplasm, but not in the nucleus. Conclusion: The results suggest that the endogenous resistin may functionally locate in the cytoplasm, but does not enter the nucleus and not down-regulate the transcription of insulin receptor promoter.