Gene expression profiling of MYC-driven tumor signatures in porcine liver stem cells by transcriptome sequencing

AIM:To identify the genes induced and regulated by the MYC protein in generating tumors from liver stem cells.METHODS:In this study,we have used an immortal porcine liver stem cell line,PICM-19,to study the role of c-MYC in hepatocarcinogenesis.PICM-19 cells were converted into cancer cells(PICM-19-CSCs)by overexpressing human MYC.To identify MYC-driven differential gene expression,transcriptome sequencing was carried out by RNA sequencing,and genes identified by this method were validated using real-time PCR.In vivo tumorigenicity studies were then conducted by injecting PICM-19-CSCs into the flanks of immunodeficient mice.RESULTS:Our results showed that MYC-overexpressing PICM-19 stem cells formed tumors in immunodeficient mice demonstrating that a single oncogene was sufficient to convert them into cancer cells(PICM-19-CSCs).By using comparative bioinformatics analyses,we have determined that>1000 genes were differentially expressed between PICM-19 and PICM-19-CSCs.Gene ontology analysis further showed that the MYCinduced,altered gene expression was primarily associated with various cellular processes,such as metabolism,cell adhesion,growth and proliferation,cell cycle,inflammation and tumorigenesis.Interestingly,six genes expressed by PICM-19 cells(CDO1,C22orf39,DKK2,ENPEP,GPX6,SRPX2)were completely silenced after MYC-induction in PICM-19-CSCs,suggesting that the absence of these genes may be critical for inducingtumorigenesis.CONCLUSION:MYC-driven genes may serve as promising candidates for the development of hepatocellular carcinoma therapeutics that would not have deleterious effects on other cell types in the liver.

Sonic hedgehog elevates N-myc gene expression in neural stem cells

Proliferation of neural stem cells is regulated by the secreted signaling molecule sonic hedgehog. In this study, neural stem cells were infected with recombinant adeno-associated virus expressing sonic hedgehog-N-enhanced green fluorescent protein. The results showed that overexpression of sonic hedgehog in neural stem cells induced the increased expression of Gill and N-myc, a target gene of sonic hedgehog. These findings suggest that N-myc is a direct downstream target of the sonic hedgehog signal pathway in neural stem cells. Sonic hedgehog and N-myc are important mediators of sonic hedgehog-induced proliferation of neural stem cells.

Expressions of myc and ras gene in human hepatocellular carcinoma by applying the double hybridization in situ

Objective: To establish a method of non-isotope double in situ hybridization in order to detect the expression of two kinds of oncogenes at single cell level simultaneously, and confirm the hypothesis of 'model of stepwise carcinogenesis'. Methods: The method of non-isotope double in situ hybridization was established with the digoxigenin (Dig) and biotin(Bio) labelled probes. The expression of two members of oncogenes of the myc and/or ras gene families (myc and N-ras, myc and K-ras, myc and H-ras, N-ras and K-ras , N-ras and H-ras, K-ras and H-ras) was further studied with the method in 10 cases of Chinese Hepatocellular Carcinomas (HCC). Results : Co-expression of two kinds of oncogenes was detected only in a few cases, reflected by coshowing two different hybridization signals ,i. e. , co-showing of Dig-myc and Bio-H-ras, Dig-myc and Bio-N-ras, Dig-myc and Bio-K-ras was observed in 2 cases, 2 cases and one case, respectively. The common characteristics were that positive cells of myc distributed diffusely, while positive cells of ras diatributed sporadically or locally among the positive cells of myc, and only a few cells exhibited co-showing of two oncogenes at single cell level. There were only 2 cases representing co-showing of two oncogenes in ras gene family (Dig-N-ras and bio-H-ras, Dig-N-ras and Bio-K-ras , respectively). The two kinds of positive cells of different ras gene represented mixed local and sporadical distribution, and co-showing of two signals was found in a few cells at single cell level. Conclusion: There are multiple oncogenes involving in tumorigenesis by their ordered activation. The activation of the ras gene family plays a role in promotion, while the activation of myc is an important event in late stage of tumorigenesis

Gene therapy with antisense c-myc adenovirus for human gastric carcino-ma cell line in vitro and for implanted carcinoma in nude mice

Objective:To study the effects of recombinant antisense c-myc adenovirus (rAS-c-myc-Ad) on SGG 7901 human gastric carcinoma cell line in for and in nude mice. Methods:The effects of rAS-c-myc-Ad and LacZ-Ad on SGG 7901 gastric carcinoma cells were observed with X-galstaining, MTT, DNA gradient degradation test, TUNEL, flow cytometry, PCR and western blot. The therapeutic effects of rAS-c-myc-Ad on the implanted ax 7901 cells in nude mice were also ob served.Results: rAS-c-myc-Ad significantly inhibited the growth of SGG 7901 cells and induced their apoptosis. After the treatment of rAS-c-myc-Ad, the prolifetion rate of the cells was decreased by 44’ l% in de and SGC 7901 cells failed to form caxcinoma ther they were implanted into nude mice. Injection of rAS-c-myc-Ad into the carcinoma subcutaneously implanted to the nude mice significantly inhibited the growth of the implanted carcinoma with an inhibition rate of 68. 9%. Conclusion: rAS-c- myc- Ad significantly inhibits the growth of SGG 7901 human gastric carcinoma cells in vitro and in nude

Expression and Biological Function of N-myc Down-regulated Gene 1 in Human Cervical Cancer

The expression of N-myc down-regulated gene 1 (NDRG1) has previously been reported to be involved in the proliferation,differentiation,invasion and metastasis of cancer cells,but its role in cervical cancer is still unclear.This study aimed to investigate the expression of NDRG1gene in human cervical cancer and its effect on aggressive tumor behaviors.The NDRG1 expression in cervical tissues and cells was detected by RT-PCR.Specific expression plasmid pEGFP-N1-NDRG1-GFP was used to enhance the expression of NDRG1 in human cervical cancer cell lines.The mRNA and protein level of NDRG1 was assessed by RT-PCR and Western blotting,respectively.Its effects on cell proliferation,migration,invasion,cell cycle and apoptosis were detected by MTT,transwell migration assay and flow cytometry (FCM),respectively.The results showed that the expression of NDRG1 in cervical cancer tissues and cells was significantly lower than in normal cervical tissues (P【0.001).After transfection with pEGFP-N1-NDRG1-GFP,the mRNA and protein expression of NDRG1 was up-regulated in Siha cells,which suppressed cell proliferation (P【0.001),induced cell cycle arrest (P【0.05),reduced invasion and migration of Siha cells (P【0.05),but caused no cell apoptosis.Moreover,vascular endothelial growth factor (VEGF),a tumor-induced angiogenesis factor,was markedly reduced and E-cadherin,a cell adhesion molecule,was increased in the cells transfected with pEGFP-N1-NDRG1-GFP.It was concluded that up-regulated NDRG1 may play a role in the suppression of malignant cell growth,invasion and metastasis of human cervical cancer.

c-Myc Knockout as a Model for Gene Editing for Training Healthcare Professional Students

Correction of genetic errors, commonly known as gene editing, holds promise to treat diseases with unmet medical needs. However, gene therapy trials do encounter unwanted outcomes, because of an incomplete understanding of the disease states, and gene therapy processes, among others. This situation encourages a concept that healthcare professionals receiving laboratory research training will not only identify inadequacies in basic biomedical knowledge of gene therapies but also provide tangible refinements. To this end, we have undertaken the PharmD student training in gene editing in a basic research laboratory setting. As a model, MYC gene was chosen for knockout using CRISPR-Cas9 method in HT29 and OVCAR8 cells. Students were involved in the design of MYC-specific gRNAs, subcloning into Cas9-carrying plasmid, and selection of knockout clones from the transfected cells. Subsequently, genomic DNA isolation and sequencing, analysis of clonal DNA sequences using online bioinformatics tools, western blotting, cell proliferation and cell division cycle experiments, were performed to characterize the MYC knockout clones. Results presented in this communication suggest that healthcare professionals who received laboratory training gain a better understanding of the disease states and mechanisms, gene therapy protocols, limitations of gene therapies, ability to critically evaluate the literature and confidence in the oversight of gene therapies in the clinic.

EXPRESSION OF c－myc GENE AND BIOSYNTHESIS OF BIOLOGICAL MACROMOLECULES IN ANTISENSE TRANSFECTANT HL_（60）~R－9

The recombinant plasmid PGC was constructed for transcription unit of c-myc gene with diorientation in vitro, to make RNA probes for detection of c-myc mRNA and antisence RNA expression of tranfectant HL-9,which was obtained from HL60 cells transfected with inducible c-myc antisense RNA expression plasmid. The results from HL-9 cells induced by Cd2+ indicated that expression of c-myc antisense RNA increased with Cd2+ concentration and exposure time, while c-myc mRNA expression progressively reduced. Using immunohistochemical technique no c-myc P62 protein expression was detected. The incorporation of 3H-TdR, 3H-UR and 3H-Leu revealed significant suppression of DNA, RNA and protein biosynthesis. It is suggested that the reversion changes previously reported in malignant Phenotypes of HL-9 cells and the inhibition of macromolecular biosynthesis mentioned above were associated with the blockade of c-myc gene expression by its antisense RNA.

Inhibition of N-Myc down regulated gene 1 in in vitro cultured human glioblastoma cells

AIM: To study short ds RNA oligonucleotides(si RNA)as a potent tool for artificially modulating gene expression of N-Myc down regulated gene 1(NDRG1) gene induced under different physiological conditions(Normoxia and hypoxia) modulating NDRG1 transcription, m RNA stability and translation. METHODS: A cell line established from a patient with glioblastoma multiforme. Plasmid DNA for transfections was prepared with the Endofree Plasmid Maxi kit. From plates containing 5 × 107 cells, nuclear extracts were prepared according to previous protocols. The p SUPERNDRG1 vectors were designed, two sequences were selected from the human NDRG1 c DNA(5'-GCATTATTGGCATGGGAAC-3' and 5'-ATGCAGAGTAACGTGGAAG-3'. reverse transcription polymerase chain reaction was performed using primers designed using published information on β-actin and hypoxia-inducible factor(HIF)-1α m RNA sequences in Gen Bank. NDRG1 m RNA and protein level expression results under different conditions of hypoxia or reoxygenation were compared to aerobic control conditions using the Mann-Whitney U test. Reoxygenation values were also compared to the NDRG1 levels after 24 h of hypoxia(P < 0.05 was considered significant).RESULTS: si RNA- and iodoacetate(IAA)-mediated downregulation of NDRG1 m RNA and protein expression in vitro in human glioblastoma cell lines showed a nearly complete inhibition of NDRG1 expression when compared to the results obtained due to the inhibitory role of glycolysis inhibitor IAA. Hypoxia responsive elements bound by nuclear HIF-1 in human glioblastoma cells in vitro under different oxygenation conditions and the clearly enhanced binding of nuclear extracts from glioblastoma cell samples exposed to extreme hypoxic conditions confirmed the HIF-1 Western blotting results. CONCLUSION: NDRG1 represents an additional diagnostic marker for brain tumor detection, due to the role of hypoxia in regulating this gene, and it canrepresent a potential target for tumor treatment in human glioblastoma. The si RNA method can represent an elegant alternative to modulate the expression of the hypoxia induced NDRG1 gene and can help to monitor the development of the cancer disease treatment outcome through monitoring the expression of this gene in the patients undergoing the different therapeutic treatment alternatives available nowadays.

Regulation of HIF-1 α to Expression of N-myc Downstream Regulated Gene 1 in Colorectal Carcinoma

Plasmid expressing small interfering RNA （siRNA） against HIF-1α （pSilence-2.1-U6-siRNA） was constructed and transfected into LS174T cells in hypoxia condition.After expression of siRNA against HIF-1 α in LS174T cells, expressions of HIF-1 α and N-myc downstream regulated gene 1 （NDRG1） gene were inhibited significantly. HIF-1 cta transcripts were positive in 67.7% （42/62） and 44.4% （8/18） of colorectal adenocarcinoma and adenoma, re- spectively. The mean percentage of cells with positive hybridization of HIF-1 α mRNA increases with the development from Duke stage A to stage C＋D （p〈 0.05）. The positive staining rate of NDRG1 protein was significant higher in than that in colorectal adenoma colorectal adenocarcinoma group group （p〈 0.05）. The level of HIF-1 a transcripts was positively correlated with the level of NDRG1 protein （p 〈 0.05） during colorectal tumor progression. HIF-1α and its down stream gene NDRG1 may play roles in tumor progression of human colorectal carcinoma.

Detection of Tumor Suppressor Gene and Oncogene in SO-Rb_(50) Human Retinoblastoma Cell Line

Retinoblastoma (Rb) is the most common malignant'cancer of eye.So-Rb_(50) is the first Rb cell line established in China in 1988.It has passed to the 387th passage now.We collected cells of the 327th passage of SO-Rb_(50),purified its genomic DNA and detected it with Rb and c-myc cDNA probes respectively(normal human white blood cells DNA was the control).We found the Rb gene was deleted while c-myc gene was amplified three times.This provides a basis for further study of the regulation of tumor development and tumor reversal with this cell line in vitro.Eye Science 1993;9:34-37.

拟南芥突变体 myc234 的鉴定及其对MeJA的敏感性分析

AtMYC 2(AT1G32640),AtMYC 3(AT5G46760)和AtMYC 4(AT4G17880)是茉莉酸信号通路的关键基因,为深入挖掘其在拟南芥生长发育及防御反应中的基因功能,结合PCR,SqRT-PCR半定量及测序技术对myc 2,myc 3和myc 4单突变体杂交获得的F3代植株进行鉴定,获得7株纯合三突变体.并以40μmol/L MeJA对纯合三突材料进行外源处理.结果显示,野生型根长较对照降低39.57%,而myc 234纯合三突变体较对照升高3.54%,说明其对MeJA敏感度明显下降.研究结果可为myc 234突变体的鉴定以及对茉莉酸敏感性相关研究提供试验依据及材料.

NDRG2 gene copy number is not altered in colorectal carcinoma

AIM To investigate if the down-regulation of N-myc Downstream Regulated Gene 2(NDRG2) expression in colorectal carcinoma(CRC) is due to loss of the NDRG2 allele(s).METHODS The following were investigated in the human colorectal cancer cell lines DLD-1, Lo Vo and SW-480: NDRG2 mRNA expression levels using quantitative reverse transcriptionpolymerase chain reaction(qRT-PCR); interaction of the MYC gene-regulatory protein with the NDRG2 promoter using chromatin immunoprecipitation; and NDRG2 promoter methylation using bisulfite sequencing.Furthermore, we performed qPCR to analyse the copy numbers of NDRG2 and MYC genes in the above three cell lines, 8 normal colorectal tissue samples and 40 CRC tissue samples.RESULTS As expected, NDRG2 mRNA levels were low in the three colorectal cancer cell lines, compared to normal colon.Endogenous MYC protein interacted with the NDRG2 core promoter in all three cell lines.In addition, the NDRG2 promoter was heavily methylated in these cell lines, suggesting an epigenetic regulatory mechanism.Unaltered gene copy numbers of NDRG2 were observed in the three cell lines.In the colorectal tissues, one normal and three CRC samples showed partial or complete loss of one NDRG2 allele.In contrast, the MYC gene was amplified in one cell line and in more than 40% of the CRC cases.CONCLUSION Our study suggests that the reduction in NDRG2 expression observed in CRC is due to transcriptional repression by MYC and promoter methylation, and is not due to allelic loss.

Detection of Gene Dosage in Circulating Free Plasma DNA as Biomarker for Lung Cancer

The increase in the number of gene copies at specific loci is a genetic alteration frequently associated with over expression of the related protein in cancer cells. Genes whose dose is consistently augmented in cancer include those involved in cell cycle control, proliferation, apoptosis, and angiogenesis among others. In this study, gene dose of onc ogenes MYCL1, MYCN, MYC, EGFR, ERBB2 and AKT2 in DNA obtained from lung tissue and blood plasma, of patients with primary lung cancer was evaluated with respect to normal lung tissue and plasma DNA of healthy individ uals, to determine the capacity of these genes to discriminate normal and neoplastic phenotypes. The number of copies of each gene was determined using real-time (2-△△CT). The AKT2 oncogene was found to be amplified frequently in plasma DNA from patients (74% of cases). This marker showed a noticeable ability to discriminate normal and neo-plastic phenotypes, with a 76 to 89% probability of correctly recognize a plasma sample provided by a lung cancer patient or a healthy individual. For this reason, this detection could be a very useful tool to supplement the existing diagnostic methods in pulmonary cancer.

Prognostic implications of FGFR1 and MYC status in esophageal squamous cell carcinoma

AIM To investigate the clinicopathological features and prognostic implications of combined MYC and fibroblast growth factor receptor 1(FGFR1) status in esophageal squamous cell carcinomas(ESCCs). METHODS All patients with ESCC(n = 180) underwent surgical resection at Seoul National University Hospital sometime between 2000 and 2013. A tissue microarray was constructed using cores obtained from representative tumor areas of formalin-fixed, paraffin-embedded tissue blocks. FGFR1 and MYC copy numbers were quantified using fluorescence in situ hybridization. The level of MYC expression was determined using immunohistochemistry. FGFR1 and MYC amplification status was compared between primary and metastatic lymph nodes. Univariate and multivariate survival analyses were performed according to adjuvant therapy status.RESULTS FGFR1 and MYC amplifications were observed in 21.4%(37/173) and 54.2%(91/168) of patients, respectively, while MYC expression was observed in 58.9%(106/180) of patients. There was a positive correlation between MYC amplification and overexpression(P = 0.002). Although FGFR1 amplification was not associated with MYC amplification or expression, 12.3%(20/163) of patients exhibited both FGFR1 amplification and MYC expression. There was also a correlation in FGFR1 amplification status between matched primary tumors and metastatic lymph nodes(P < 0.001). MYC expression was higher in ESCCs with p T1(P < 0.001) and in those with no lymph node metastasis(P = 0.023). MYC expression was associated with prolonged diseasefree survival(P = 0.036) and overall survival(OS)(P = 0.017) but was not an independent prognostic factor. FGFR1 amplification was an independent predictor for prolonged OS in all patients(P = 0.029) and in those who did not receive adjuvant therapy(P = 0.013). Combined FGFR1 amplification and MYC expression predicted better OS in patients who did not receive adjuvant therapy(P = 0.034) but not in those who did receive adjuvant therapy.CONCLUSION FGFR1 amplification and MYC expression have prognostic implications in resected ESCCs with respect to adjuvant therapy. The role of FGFR1-targeted therapy in ESCC remains to be explored.

c-Myc基因扩增的原发性胰腺弥漫性大B细胞淋巴瘤2例并文献复习

目的探讨发生在胰腺的c-Myc基因扩增的弥漫性大B细胞淋巴瘤(DLBCL)患者的临床表现、病理特征及预后。方法回顾性分析2例c-Myc基因扩增的原发性胰腺DLBCL患者的临床病理特征。结果病例1,DLBCL,非生发中心型;病例2,DLBCL,生发中心型。病例1未手术治疗,病例2行十二指肠切除术后化疗。2例患者均采用利妥昔单抗联合阿霉素、环磷酰胺,长春新碱和泼尼松龙(R-CHOP方案)化疗,病例1总生存期18 d,病例2总生存期15个月。结论c-Myc基因扩增的原发性胰腺DLBCL患者临床表现与胰腺癌相似,病情易进展,预后很差,美罗华R-CHOP方案化疗方案治疗效果不佳,建议采取更激进的治疗方式改善预后。

Expression of telomerase hTERT in human non-small cell lung cancer and its correlation with c-myc gene

Objective To investigate the expression of human telomerase catalytic subunit,hTERT, in human non-small cell lung cancer (NSCLC) and its correlations to c-myc gene.Methods hTERT and c-myc mRNA expressions were detected by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Statistical correlation analysis was made to estimate whether there was interrelation between them.Results Positive rate of hTERT expression in 51 surgically resected lung cancer specimens was 86.3%,significantly higher than that in adjacent non-neoplastic lung tissues and benign lesions,which were 14.3% and 27.3% respectively. No statistical significance was observed between the frequency of hTERT expression and histologic types,degree of differentiation,TNM stages,tumor size or lymph nodes metastases. Correlation analysis revealed that the expression of c-myc gene was significantly related to that of hTERT (correlation coefficient,r =0.633,P <0.001).Conclusions hTERT may be a useful tumor marker in diagnosing lung cancer. Significant correlation between the expression of hTERT and c-myc mRNA indicates that the activation and up-regulation of hTERT might be conferred by over-expression of c-myc gene.

Anti-fibrotic Effects of Salvia miltiorrhiza and Ligustrazine Injection on LX-2 Cells Involved with Increased N-myc Downstream-Regulated Gene 2 Expression

Objective: To investigate the effects of Salvia miltiorrhiza and Ligustrazine Injection（SML） on proliferation and apoptosis of human hepatic stellate cell LX-2 and the expression of N-myc downstreamregulated gene 2（NDRG2, a tumor suppressor gene）. Methods: HSCs from the LX-2 cell line were cultured in vitro. The proliferative state of different initial LX-2 cell numbers was measured using a 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide（MTT） colorimetric assay. LX-2 cells were plated in 96-well plates at an approximate density of 2.50×10;cells/mL and cultured for 24 h followed by the application of different concentrations of SML（1, 2, 4 and 8 μL/mL）. Cell proliferation was measured using the MTT assay at 24 and 48 h. Apoptosis was detected by flow cytometry at 24 h. LX-2 cells were treated with different concentrations of SML and extracted with protein lysis buffer. The levels of NDRG2 and β-catenin were measured by Western blot. Results: With the exception of the 1 and 2 μL/mL concentrations, 4 and 8 μL/mL SML inhibited cell proliferation in a concentration-dependent manner at 24 and 48 h（P<0.05）. With the exception of the 1 and 2 μL/mL concentrations, the NDRG2 expression level was greatly increased in a concentration-dependent manner. However, the level of β-catenin was unaffected. Conclusion: SML inhibit LX-2 cell proliferation in a concentration-dependent manner, and the mechanism may be associated with NDRG2 over-expression.

Lipoxin A4 Ameliorates Lipopolysaccharide-lnduced A549 Cell Injury through Upregulation of N-myc Downstream-Regulated Gene-1

Background： Lipoxin A4 （LXA4） can alleviate lipopolysaccharide （LPS）-induced acute lung injury （ALl） and acute respiratory distress syndrome through promoting epithelial sodium channel （ENaC） expression in lung epithelial cells. However, how LXA4 promote ENaC expression is still largely elusive. The present study aimed to explore genes and signaling pathway involved in regulating ENaC expression induced by LXA4. Methods： A549 cells were incubated with LPS and LXA4, or in combination, and analyzed by quantitative real-time polymerase chain reaction （qRT-PCR） of ENaC-α/γ. Candidate genes affected by LXA4 were explored by transcriptome sequencing ofA549 cells. The critical candidate gene was validated by qRT-PCR and Western blot analysis ofA549 cells treated with LPS and LXA4 at different concentrations and time intervals. LXA4 receptor （ALX） inhibitor BOC-2 was used to test induction of candidate gene by LXA4. Candidate gene siRNA was adopted to analyze its influence on A549 viability and ENaC-α expression. Phosphoinositide 3-kinase （PI3K） inhibitor LY294002 was utilized to probe whether the PI3K signaling pathway was involved in LXA4 induction of candidate gene expression. Results： The A549 cell models of ALl were constrticted and subjected to transcriptome sequencing. Among candidate genes, N-myc downstream- regulated gent- 1 （NDRG 1 ） was validated by real-time-PCR and Western blot. NDRG 1 mRNA was elevated in a dose-dependent manner of LXA4, whereas BOC-2 antagonized NDRG 1 expression induced by LXA4. NDRG I siRNA suppressed viability of LPS-treated A549 cells （treatment vs. control, 0.605± 0.063 vs. 0.878 ± 0.083, P = 0.040） and ENaC-α expression （treatment vs. control, 0.458 ± 0.038 vs. 0.711 ± 0.035, P = 0.008）. LY294002 inhibited NDRG 1 （treatment vs. control, 0.459 ± 0.023 vs. 0.726 ± 0.020, P 0.001 ） and ENaC-α （treatment vs. control, 0.236 ± 0.021 vs. 0.814 ±0.025, P 〈 0.001 ） expressions and serum- and glucocorticoid-inducible kinase I phosphorylation （treatment vs. control, 0.442± 0.024 vs. 1.046 ± 0.082, P = 0.002）, indicating the PI3K signaling pathway was involved in regulating NDRG 1 expression induced by LXA4. Conclusion： Our research uncovered a critical role of NDRG1 in LXA4 alleviation of LPS-induced A549 cell injury through mediating PI3K signaling to restore ENaC expression.

The role of c-myc in regulating mdr1 gene expression in tumor cell line KB

To investigate the relationship between c-myc expression and mdr1 regulation in multidrug resistance (MDR) tumor cell line KBv200 Methods A DNA sequence encoding the ribozyme gene was incorporated into a eukaryotic expression vector (pHβ Apr-1 neo) and transfected into the cell line KB, which is resistant to vincristine and expresses the MDR phenotype The changes of c-myc protein, P-glycoprotein (P-gp) and c-myc mRNA in the KB cell line were assessed before and after treatment with anti-mdr1-ribozyme using immunohisto-chemistry, flow cytometry and semi-quantitative RT-PCR methods Results The results demonstrate elevated levels of c-myc mRNA and c-myc protein as well as P-gp in KBv200 cells which are resistant to vincristine (VCR), compared to these of the KB cell which is not resistant to VCR The expression of c-myc protein, P-gp and c-myc mRNA in the multidrug resistant cell, KBv200, displayed higher than that in the sensitive cell, KB However, after reversing the multidrug resistance phenotype by anti-mdr1-ribozyme, the level of c-myc protein, P-gp and c-myc mRNA expression showed significant down-regulation in KBv/5mR3, without difference in KB/5mR3 and KB Conclusion The results of our study suggest that there is a close relationship between c-myc gene and mdr1 gene c-myc may be involved in regulating the expression of mdr1

Reduction of Repair in c-myc Gene Within HL-60 Induced With DMSO

One of the important advancements in DNA repair research is the demonstration of preferential repair of transcriptionally active DNA in UV-irradiation cells. Experiment results have shown that repair in specific sequence in and around