• Journal of Life Science
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• v.5 no.3
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• pp.105-116
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• 1995

To investigate genomic changes in c-myc gene by a chemical carcinogen, human lymphoblast NC-37 cells were exposed to benzo(a)pyrene(BP) and dimethylbenzanthracene(DMBA), and the c-myc gene expression was evaluated by Northern and Southern blot hybridization techniques. The results are as follows: When the genomic DNA of NC-37 cells exposed to several concentrations(1.25, 2.5 and 5ug/ml) of BP concentration. However, the c-myc gene was most significantly enhanced with 2.5ug/ml of BP. The expressions of c-myc gene in NC-37 cells was stimulated by BP and DMBA. Addition of TPA reduced the gene expression BP-treated cells, whereas it enhanced the gene expression in DMBA-treated cells. The expression of c-H-ras gene was slightly increased by treatment with BP and DMBA alone and in combination with TPA, however the magnitude of increase was not significantly different between each other. The expressions of c-myc c-H-ras genes in Burkitt's lymphoma cells were greater than those in NC-37 cells. When the DNA extracted from NC-37 cells exposed to various concentrations of BP were amplified by polymerase chain reaction using a primer set containing c-myc exon I, the amplified products were of the same size in all groups. To evaluate the BP toxicity in E.coli to which human c-myc gene-cloned pBR322 vector was inserted, Southern blot hybridization was conducted on c-myc genes digested with EcoRI/HindIII and Smal/Xbal restriction enzymes, and observing that in 2 ug/ml BP-treated cells a 3.5kb fragment was generated in addition to 1.3kb fragment which can be observed in normal cells. Direct nucleotide sequence analysis of polymerase chain reaction products showed a mutation of G$\longrightarrow$A transition at the Smal recognition site.

• The Korean Journal of Zoology
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• v.38 no.2
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• pp.196-203
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• 1995

The c-myc proto-oncogene, one of the immediately earlY genes, is expressed in various mammalian cell types and heavily involved in the regulation of cell proliferation and differentiation. To determine endogeneous expression pattern of c-myc gene in preimpBantation mouse embwos, we employed a reverse transcription coupled to polvrnerase chain reaction (RT-PCR). Transcript of c-myc was detected at fertilized embryos as a maternal transcript. At the early two-cell stave, transcript of c-myc gene was hardly detected, bu, appeared at late two-cell embryos as a zygotic transcript. The level of c-myc expresion was increased at later stases and peaked at blastocvst stage. To examine the functional role of promoter region for c-myc gene transcription, we fused the 5'upstream region (1.8 kb) including econ 1 of c-myc genomic DNA with E. coli lacE gene fnamed as pcMYC-laczl. pcMYC-lacZ was microiniected into the pronscleus of mouse one-cell embryovs, and p·salactosidase activity was determined tv histochemical staining with X-gal at different stases. f-galactosidase activity was detected only at blastocyst, but not at the earlier stage embryos. This result indicates that c-myc gene is transcriptionallv active during mouse preimplantation development.

• Journal of Yeungnam Medical Science
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• v.14 no.1
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• pp.67-76
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• 1997

The occurrence of multidrug resistance (MDR) is one of the main obstacles in the successful chemotherapeutic treatment of cancer. In this study The gene expressions of multidrug resistance-associated protein (MRP), c-myc and c-fos were investigated in L1210 cells. Adriamycin- or vincristine-resistant L1210 cells, L1210AdR or L1210VcR, respectively, has been identified to overexpression of mdr1 gene. The expression leve of MRP gene in L1210AdR and L1210Cis was more decreased than that in L1210 cells. The c-myc and c-fos genes were expressed both in L1210 and resistant sublines. In L1210AdR, the expressions level of c-myc and c-fos genes were decreased than in L1210. However, in L1210VcR and L1210Cis, c-myc and c-fosgene expressionwere rather increased than L1210. These results suggested that MRP does not contribute in resistance of drug-resistant L1210 cells and there is no relations between MRP and mdr1 gene expression. The expression of c-myc and c-fos gene may be changed during transformation of L1210 to drug-resistant sublines.

• The Korean Journal of Zoology
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• v.38 no.4
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• pp.550-556
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• 1995

The c-myc proto-oncogene is Involved In the control of normal cell proliferation and differentiation of many cell lineages. Although it has heen suggested that c-myc may play an important role in the mammalian early development, it Is unclear whether the embryonic c-myc mRNA is originated from zygotic gene expression or stored maternal message. Thus, we have construded expression vectors, In which the 5, flanking sequences including c-myc promoter region and a large non-coding exon I are fused 'sith E. coli lacZ gene that encedes $\beta$-galactosldase as a reporter. As c-myc exon I contains a modulatory sequence, we designed t, vo types of vectors (pcmyc.Gall and pcmyc-Ga12) to examine the role of exon I in c-myc expression. The former contains the complete exon I and the later has a deletion in 40 bp of modulator sequence located In the exon I of c-myc These vectors were microInjected into fertilized one-cell embryos and $\beta$-galactosidase activity was examined by X-gal staining during early embryogenesis. $\beta$-galactosidase activity derived from c-myc promoter was decreased at two-cell stage. The expression level directed by pcmyc- Ga12 was similar to that of pcmyc-Gal1, indicating that the medulatory sequence in exon I may not be Involved at least In the regulation of embryonic c-myc expression. In summary, the present study indicates that the c-myc promoter is functional at the early stage embryo, and the regulation of c-myc expression is under the control of "zygotic" clock of preimplantation mouse embryos.e embryos.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.8
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• pp.4883-4889
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• 2013

Background: The most common incident cancer and cause of cancer-related deaths in women is breast cancer. The Myc gene is upregulated in many cancer types including breast cancer, and it is considered as a potential anti-cancer drug target. The present study was conducted to evaluate the Myc (gene and protein) expression pattern in an experimental mammary tumour model in rats. Materials and Methods: Thirty six Sprague Dawley rats were divided into: Experimental group (26 animals), which received the chemical carcinogen N-methyl nitrosourea (MNU) and a control group (10 animals), which received vehicle only. c-Myc oncoprotein and its mRNA expression pattern were evaluated using immunohistochemistry (IHC) and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively, in normal rat mammary tissue and mammary tumours. The rat glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was used as internal control for semi-quantitative RT-PCR. Results: Histopathological examination of mammary tissues and tumours from MNU treated animals revealed the presence of premalignant lesions, benign tumours, in situ carcinomas and invasive carcinomas. Immunohistochemical evaluation of tumour tissues showed upregulation and heterogeneous cellular localization of c-Myc oncoprotein. The expression levels of c-Myc oncoprotein were significantly elevated (75-91%) in all the tumours. Semi-quantitative RT-PCR revealed increased expression of c-Myc mRNA in mammary tumours compared to normal mammary tissues. Conclusions: Further large-scale investigation study is needed to adopt this experimental rat mammary tumour model as an in vivo model to study anti-cancer strategies directed against Myc or its downstream partners at the transcriptional or post-transcriptional level.

• Proceedings of the Korean Society of Toxicology Conference
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• 2000.11a
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• pp.45-67
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• 2000

2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) is a mutagenic and carcinogenic heterocyclic amino found in cooked meat. The in vivo mutagenicity and hepatocarcinogenicity of MeIQx were examined in mice harboring the lacZ mutation reporter gene ($Muta^{TM}$ Mice) and bitransgenic mice over-expressing the c-myc oncogene. C57B1/$\lambda$lacZ and bitransgenic c-myc (albumin promoter)/$\lambda$lacZ mice were bred and weaned onto an AIN-76 based diet containing $0.06\%$ (w/w) MeIQx or onto control diet. After 30 weeks on diet, only male bitransgenic mice on MeIQx developed hepatocellular carcinoma ($100\%$ incidence) indicating that there was synergism between c-myc over-expression and MeIQx. By 40 weeks, hepatic tumor incidence was $100\%$ ($17\%$) and $44\%$ ($0\%$) in male c-myc/$\lambda$lacZ and C57B1/$\lambda$lacZ mice given MeIQx (or control) diet, respectively, indicating that either MeIQx or c-myc over-expression alone eventually induced hepatic tumors. At either time point, mutant frequency in the lacZ gene was at least 40-fold higher in MeIQx-treated mice than in control mice of either strain. These findings suggest that MeIQx-induced hepatocarcinogenesis is associated with MeIQx-induced mutations. Elevated mutant frequency in MeIQx-treated mice also occurred concomitant with the formation of MeIQx-guanine adducts as detected by the $^{32}P$-postlabeling assay. Irrespective of strain or diet, sequence analysis of the lacZ mutants from male mouse liver showed that the principal sequence alteration was a single guanine-base substitution. Adenine mutations, however, were detected only in animals on control diet. MeIQx-fed mice harboring the c-myc oncogene showed a l.4-2.6-fold higher mutant frequency in the lacZ gene than mice not carrying the transgene. Although there was a trend toward higher adduct levels in c-myc mice, MeIQx-DNA adduct levels were not significantly different between c-myc/$\lambda$lacZ and C57B1/$\lambda$lacZ mice after 30 weeks on diet. Thus, it appeared that factors in addition to MeIQx-DNA adduct levels, such as the enhance rate of proliferation associated with c-myc over-expression, may have accounted for a higher mutant frequency in c-myc mice. In the control diet groups, the lacZ mutant frequency was significantly higher in c-myc/$\lambda$lacZ mice than in 057B1/$\lambda$1acZ mice. The findings are consistent with the notion that c-myc over-expression is associated with an increase in mutagenesis. The mechanism for the synergistic effects of c-myc over-expression on MeIQx hepatocarcinogenicity appears to involve an enhancement of MeIQx-induced mutations.

• Journal of Life Science
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• v.10 no.6
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• pp.621-629
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• 2000

Camptothecin (CPT) is an antitumor alkaloid that has been isolated from the Chinese tree, Camptotheca acuminata. The cytotoxicity of CPT has been correlated to its inhibition of DNA topoisomerase (Topo) I by stabilizing drug-enzyme-DNA “cleavable complex" resulting in DNA single-strand breaks and DNA-protein crosslinks. This studies were designed to elucidate whether CPT regulates Topo I mediated by CPT in DNAs containing c-myc protooncogene. We have conducted experiments on Topo I purification, pUC-MYC I cloning and Topo I assay using electrophoresis, quantitative RT-PCR and Northern blotting techniques. CPT ingibited the relaxation activity of Topo I in pUC19 DNA at various concentrations (1-1000 $\mu$M), while it enhanced the cleavage of Topo I in the pUC-MYC I by forming a cleavable complex at relatively high concentrations (100-1000 $\mu$M). In HL-60 cells treated with CPT, the expression of c-myc gene was decreased over that in the control group with no changes in the expression of Topo I mRNA. Our results suggest that Topo I is the target of CPT cytotoxicity but it does not affect Topo I extression, and the suppression of c-myc mRNA expression by CPT is due to c-myc damage resulted from formation of a cleavable complex with CPT. CPT.

• Journal of the Korea Convergence Society
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• v.9 no.5
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• pp.91-97
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• 2018

This study has been conducted to see the expression of $TGF-{\beta}_1$, c-Myc, Erb-B2 and $Thymosin-{\beta}_4$ genes in ethanol - damaged liver tissues. Experimental groups were divided into 2 groups, one where damaged liver was caused by 25% ethanol and normal group administered with purified water. Results of test showed the expression of $TGF-{\beta}_1$, c-Myc, and $Thymosin-{\beta}_4$ genes was higher in the experimental group treated with 25% ethanol than in the normal group. Erb-B2 gene was not expressed clearly. Thus, it is considered that we can expect to utilize $TGF-{\beta}_1$, c-Myc 및 $Thymosin-{\beta}_4$ as auxiliary data and find clinical meanings of diagnosis on hepatic diseases, In addition to serologic and histological examination by convergence examining the gene expression status by molecular diagnostic techniques in liver-related disease prevention and diagnosis through results of this study.

• BMB Reports
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• v.41 no.8
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• pp.593-596
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• 2008

ADPKD (Autosomal Dominant Polycystic Kidney Disease) is characterized by the progressive expansion of multiple cystic lesions in the kidneys. ADPKD is caused by mutations in Ed-pl. consider PKD1 and PKD2. Recently a relation between c-myc and the pathogenesis of ADPKD was reported. In addition, c-Myc is a downstream effector of PKD1. To identify the gene regulated by PKD2 and c-Myc, we performed gene expression profiling in PKD2 and c-Myc overexpressing cells using a human 8K cDNA microarray. NCAM (neuronal cell adhesion molecule) levels were significantly reduced in PKD2 overexpressing systems in vitro and in vivo. These results suggest that NCAM is an important molecule in the cystogenesis induced by PKD2 overexpession.

• The Journal of the Korean Society for Microbiology
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• v.22 no.2
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• pp.167-174
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• 1987

N-myc, a DNA sequence related to the oncogene c-myc, was found to be amplified in untreated primary neuroblastomas and the amplification appeared to be associated with advanced disease at diagnosis and rapid tumor progression. Synthetic peptides have been useful immunogens for generating antisera and monoclonal antibodies to a number of native proteins. In order to identify myc-related protein in the tumor cells, an antiserum against a synthetic hexapeptide (-Glu-Asp-Ile-Trp-Lys-Lys-), whose sequence corresponds to a part of the exon 2 of oncogene N-myc, was prepared by immunizing a rabbit with BSA-conjugated peptide. After ammonium sulfate precipitation and affinity column chromatography, it appeared to be specific to the peptide. Strong nuclear staining in immunoperoxidase method using this serum was observed in both human promyeloid leukemic cell line, HL-60(containing high c-myc copy number), and human neuroblastoma cell line, LA-N-5 (containing high N-myc copy number), whereas LA351 (human lymphoid cell line) cells did not react with the serum. This reaction was completely abrogated by incubating the antiserum with soluble excess peptide. These data suggest that the protein encoded by N-myc could be localized in the nucleus as c-myc protein and this antiserum can be used to detect myc-related tumor cells in clinical samples and to determine if the N-myc expression correlates with genomic amplification in cell lines, untreated primary tumors, and untreated metastases.