Biomedical subjects

Yongbaek Kim

Publications and source records attributed to Yongbaek Kim.

14 recordsLinked to original sources

PubMed2006

Evaluation of genetic alterations in cancer-related genes in lung and brain tumors from B6C3F1 mice exposed to 1,3-butadiene or chloroprene.

1,3-Butadiene and chloroprene are multisite carcinogens in B6C3F1 mice with the strongest tumor response being the induction of lung neoplasms in females. Incidence of brain tumors in mice exposed to 1,3-butadiene was equivocal. This article reviews the efforts of our laboratory and others to uncover the mechanisms of butadiene and chloroprene induced lung and brain tumor responses in the B6C3F1 mouse. The formation of lung tumors by these chemicals involved mutations in the K-ras cancer gene and loss of heterozygosity in the region of K-ras on distal chromosome 6, while alterations in p53 and p16 were implicated in brain tumorigenesis.

Alleles↗

PubMed2006

Major carcinogenic pathways identified by gene expression analysis of peritoneal mesotheliomas following chemical treatment in F344 rats.

This study was performed to characterize the gene expression profile and to identify the major carcinogenic pathways involved in rat peritoneal mesothelioma (RPM) formation following treatment of Fischer 344 rats with o-nitrotoluene (o-NT) or bromochloracetic acid (BCA). Oligo arrays, with over 20,000 target genes, were used to evaluate o-NT- and BCA-induced RPMs, when compared to a non-transformed mesothelial cell line (Fred-PE). Analysis using Ingenuity Pathway Analysis software revealed 169 cancer-related genes that were categorized into binding activity, growth and proliferation, cell cycle progression, apoptosis, and invasion and metastasis. The microarray data were validated by positive correlation with quantitative real-time RT-PCR on 16 selected genes including igf1, tgfb3 and nov. Important carcinogenic pathways involved in RPM formation included insulin-like growth factor 1 (IGF-1), p38 MAPkinase, Wnt/beta-catenin and integrin signaling pathways. This study demonstrated that mesotheliomas in rats exposed to o-NT- and BCA were similar to mesotheliomas in humans, at least at the cellular and molecular level.

Acetates↗

PubMed2006

Disseminated transmissible venereal tumor in a dog.

Transmissible venereal tumor (TVT) is a well-documented transplantable tumor in dogs, with no breed or sex predilection and a low metastatic rate. In this report, a 2-year-old intact female Mastiff that had numerous, rapidly growing masses throughout the subcutis mainly at the dorsal body plane, the caudal half of the ventral abdomen, and around the vulva was euthanized due to poor prognosis. Neoplastic nodules similar to those seen in the subcutis were also noted in the lung, anterior mediastinum, liver, spleen, kidney, and superficial and deep lymph nodes in both abdominal and thoracic cavities. The neoplastic nodules from the subcutis as well as metastatic foci revealed similar cytologic and histologic features, which were consistent with canine TVT. By immunohistochemical staining, the neoplastic cells were positive for lysozyme and vimentin but were negative for cytokeratin, desmin, CD3, and CD79a. The diagnosis of the TVT was further supported by the identification and analysis of long interspersed nuclear elements (LINE) from paraffin-embedded tumor tissue. This case is a rare example of TVT with multiorgan metastasis. In this case, the polymerase chain reaction technique was useful in differential diagnosis of canine round cell tumors because this technique can be applied in retrospective as well as future study.

Animals↗

PubMed2005

Overview of the molecular biology of hepatocellular neoplasms and hepatoblastomas of the mouse liver.

The molecular pathogenesis of chemically induced hepatocellular neoplasms and hepatoblastomas in the B6C3FI mouse is unclear but may involve alterations in the fi-catenin/Wnt signaling pathway as was recently described for human liver neoplasms. The objectives of this research were to characterize the mutation frequency and spectrum of P-catenin mutations and the intracellular localization of I-catenin protein accumulation in chemically induced hepatoblastomas and hepatocellular neoplasms. In the majority of the hepatoblastomas examined by immunohistochemical methods, both nuclear and cytoplasmic localization of P-catenin protein were detected, whereas in hepatocellular adenomas and carcinomas and normal liver only membrane staining was observed. Genomic DNA was isolated from paraffin sections of each liver tumor. P-catenin exon 2 (corresponds to exon 3 in humans) genetic alterations were identified in the majority of hepatoblastomas from exposed mice. Deletion mutations were identified more frequently than point mutations in hepatoblastomas. Hepatocellular adenomas and carcinomas from treated mice had mutations in exon 2 of the B-catenin gene which ranged from 32-43%, while 10% P-catenin mutations were detected in spontaneous neoplasms. By immunohistochemical methods cyclin Dl was observed in most nuclei of hepatoblastomas and strong expression of cyclin Dl was confirmed by Western analysis regardless of treatment. The cumulative data suggests that P-catenin mutations with upregulation of the B-catenin protein and Wnt signaling most likely increased cyclin Dl expression. Cyclin D1 may provide an advantage during tumor progression of hepatocellular neoplasms and hepatoblastomas. The review will also focus on other genes which are important in mouse and human liver tumors.

Adenoma, Liver Cell↗

PubMed2005

Genetic alterations in brain tumors following 1,3-butadiene exposure in B6C3F1 mice.

The nervous system of the B6C3F1 mouse has rarely been a target for chemical carcinogenesis in the National Toxicology Program (NTP) bioassays. However, 6 malignant gliomas and 2 neuroblastomas were observed in B6C3F1 mice exposed to 625 ppm 1,3-butadiene (NTP technical reports 288 and 434). These mouse brain tumors were evaluated with regard to the profile of genetic alterations that are observed in human brain tumors. Alterations in the p53 tumor suppressor gene were common. Missense mutations were observed in 3/6 malignant gliomas and 2/2 neuroblastomas and were associated with loss of heterozygosity. Most of the mutations occurred in exons 5-8 of the p53 gene and were G-->A transitions, and did not involve CpG sites. Loss of heterozygosity at the Ink4a/Arf gene locus was observed in 5/5 malignant gliomas and 1/1 neuroblastoma, while the PTEN(phosphatase and tensin homologue) gene locus was unaffected by deletions. One of 2 neuroblastomas had a mutation in codon 61 of H-ras, while H-ras mutations were not observed in the malignant gliomas examined. Only 1 brain tumor has been reported from control mice of over 500 NTP studies. This malignant glioma showed no evidence of alterations in the p53 gene or K- and H-ras mutations. It is likely that the specific genetic alterations observed were induced or selected for by 1,3-butadiene treatment that contributed to the development of mouse brain tumors. The observed findings are similar in part to the genetic alterations reported in human brain tumors.

Animals↗

PubMed2005

Analysis of p53 tumor suppressor gene, H-ras protooncogene and proliferating cell nuclear antigen (PCNA) in squamous cell carcinomas of HRA/Skh mice following exposure to 8-methoxypsoralen (8-MOP) and UVA radiation (PUVA therapy).

Treatment with 8-methoxypsoralen (8-MOP) and ultraviolet radiation (primarily UVA), called PUVA therapy, has been used to treat different chronic skin diseases but led to a significant increased risk for skin cancer. The National Toxicology Program (NTP) performed a study in mice treated with PUVA that showed a significant increase in squamous cell carcinomas of the skin. In the present study, we evaluated the protein expression of p53 and PCNA and DNA mutations of p53 and H-ras genes in both hyperplastic and neoplastic squamous cell lesions from the NTP study. By immunohistochemical staining, protein expression of both p53 and PCNA was detected in 3/16 (19%) of hyperplastic lesions and 14/17 (82%) of SCCs in groups treated with both 8-MOP and UVA. The mutation frequency of p53 in SCCs from mice administered 8-MOP plus UVA was 15/17 (88%) with a predominant distribution of mutations in exon 6 (14/15 - 93%). No H-ras mutations were detected in the hyperplastic lesions/tumors. The mutagenic effect of PUVA on the p53 tumor suppressor gene may lead to a conformational modification and inactivation of the p53 protein, which are considered critical steps in PUVA-induced skin carcinogenesis. The p53 mutational frequency and patterns from our study were different from those reported in human PUVA-type tumors.

Animals↗

PubMed2005

Disseminated visceral coccidiosis and cloacal cryptosporidiosis in a Japanese white-naped crane (Grus vipio).

A 4-mo-old male Japanese white-naped crane (Grus vipio) kept in an outdoor exhibit at the Everland Zoological Gardens in Korea became depressed and developed anorexia, weight loss, and diarrhea. Death of this bird was associated with an overwhelming systemic infection by an intracellular coccidian parasite, which resulted in necrosis and granulomatous inflammation in a number of major organs, including the intestine, liver, spleen, and kidney. Coccidian parasite-laden macrophages were commonly found in the blood vessels of these organs. Using electron microscopy and polymerase chain reaction assays, the parasite was identified as Eimeria sp. The bird was also infected with Cryptosporidium sp., which suggests an immunosuppressed state, although the cause of such suppression was not identified. Our findings suggest that an initial Eimeria sp. intestinal infection spread to other organs through the blood vessels, with the immunosuppressed state possibly contributing to a rapid hematogenous transmission. To our knowledge, this is the first report of disseminated visceral coccidiosis caused by Eimeria sp. in a captive Japanese white-naped crane.

Animals↗

PubMed2004

Development of quantitative competitive-reverse transcriptase-polymerase chain reaction for detection and quantitation of avian leukosis virus subgroup J.

Infection with avian leukosis virus subgroup J (ALV-J) causes severe economic losses in the broiler industry by increasing mortality, producing tumors, and decreasing weight gain in chickens. The quantitation of ALV-J is difficult because of its failure to produce a cytopathic effect in cell culture systems and the nonspecificity of antigen-capture enzyme-linked immunosorbent assay (ELISA) tests. This study was performed to develop a quantitative competitive-reverse transcriptase-polymerase chain reaction (QC-RT-PCR) method based on coamplification of ALV-J genomic RNA and a known amount of a synthesized RNA competitor. The 369 bp RNA competitor was constructed by restriction enzyme treatment of an ALV-J specific 545 bp PCR product, ligation, transformation into Escherichia coli, and in vitro transcription. The competitor contained the same amplification primer annealing sites and sequence as the original viral RNA, except that it had a 176 bp internal deletion. Coamplified RT-PCR products were visualized by electrophoresis and ethidium bromide staining, and fluorescences were quantified using computer-assisted image analysis. The sensitivity of this new QC-RT-PCR method was 25 fg of viral RNA, and 10-fold dilutions were differentiable. This method allowed absolute and relative quantification of ALV-J RNA copy numbers and was simpler than previously published methods for ALV-J quantification.

Animals↗

PubMed2004

The effects of cyclophosphamide treatment on the pathogenesis of subgroup J avian leukosis virus (ALV-J) infection in broiler chickens with Marek's disease virus exposure.

Studies were performed to determine the effects of Bcell suppression on the pathogenesis of Subgroup J avian leukosis virus (ALV-J) in broiler chickens. Neonatal chickens were treated with cyclophosphamide (CY) or PBS, and then infected with ALV-J (ADOL-7501) at 2 weeks of age. CY treatment induced B cell specific immunosuppression throughout the experiment confirmed by decreased bursal weight, intact lymphocyte mitogenetic activity stimulated by Con A and increased relative subpopulation of CD3-positive cells as measured by flow cytometry. Chickens in this experiment had Mareks disease virus exposure prior to three weeks of age as determined by the presence of lymphocytic infiltration and antibody. Virus neutralizing antibody against ALV-J was first observed at 6 weeks post-infection in some of the infected chickens in the PBS group. As expected, none of the chickens from the CY group and uninfected chickens developed virus-neutralizing antibody. The viremic status was measured by real time RT-PCR using SYBR green I dye. The percentage of viremic chickens was significantly higher, and more chickens had high titered viremia, in the CY treated group. No neoplastic foci consistent with ALVJ infection were observed in any of the experimental chickens. The frequency and intensity of viral antigen expression determined by immunohistochemistry was significantly higher in tissues from CY treated birds than those of PBS treated chickens at 3 weeks post-infection. This study showed that B cell specific immunosuppression with CY treatment in chickens resulted in increase in viremia and viral antigen load in tissues.

Animals↗

PubMed2003

Lesions induced in broiler chickens by cyclophosphamide treatment.

Cyclophosphamide (CY) is an immunosuppressant and inhibits cell division by alkylating nucleic acids. This study was performed to determine the toxic effects of CY treatment in broiler chickens. One-d-old White Plymouth Rock broiler chickens were treated with either 4 mg/d CY or phosphate buffered saline (PBS) for 4 consecutive days. Mortality of the CY-treated chickens was 65.4% (34/52), while that of the PBS-treated chickens was 10% (5/50). CY-treated chickens were significantly smaller and had delayed feathering and lower relative bursal weight compared to those PBS treated. Histologically, the lymphocytes were markedly depleted in the spleen and bursa. Bone marrow was severely hypocellular and replaced by adipose tissue. Diffuse vacuolation of hepatocytes with individual cell necrosis was present in the liver. There was segmental necrosis of lining epithelial cells of renal tubules with eosinophilic material and necrotic detritus within the lumens. The lesions in the liver, kidney and bone marrow were transient and repaired by 2 w of age.

Animals↗

PubMed2003

Effects of cyclosporin A treatment on the pathogenesis of avian leukosis virus subgroup J infection in broiler chickens with Marek's disease virus exposure.

In this study, we investigated the effects of T-cell suppression on the pathogenesis of subgroup J avian leukosis virus (ALV-J). Chickens were treated with cyclosporin A (CSP) 50 mg/Kg body weight or a corresponding volume of olive oil per every three days after hatching until the end of experiment. Some of the chickens from each treatment group were infected with an isolate of ALV-J, ADOL-7501, at 2 weeks of age. The effects of viral infection were compared to uninfected birds in same treatment group. Intramuscular injection of CSP induced significant T-cell specific immunosuppression determined by decreased cutaneous basophilic hypersensitivity response and decreased lymphocyte mitogenic activity using concanavalin A. Most of the chickens examined had Marek's disease virus infection prior to 3 weeks of age. The percentage of antibody-positive birds and antibody titers were similar in infected chickens between both treatment groups. The ratio of viremic chickens was significantly higher in CSP treated group than that of the Oil treated group. Microscopically, one CSP treated chicken had a nephroblastoma at 10 weeks post infection. At 7 and 10 weeks post-infection, more chickens had myeloid cell infiltrations in multiple organs including heart, liver and occasionally lung. Expression of ALV-J viral antigen determined by immunohistochemical staining was significantly higher in CSP treated chickens than Oil treated chickens at 10 weeks post-infection. This study indicated that chemically-induced T-cell suppression may enhance pathogenicity of the AVL-J virus in broilers.

Animals↗

PubMed2002

Comparison and verification of quantitative competitive reverse transcription polymerase chain reaction (QC-RT-PCR) and real time RT-PCR for avian leukosis virus subgroup J.

Avian leukosis virus subgroup J (ALV-J) infections cause significant economic losses because of increased mortality, tumor production, decreased production, and cost for eradication. Current quantification methods for ALV-J expressed by TCID(50) are difficult to determine because of the lack of cytopathic effect in cell cultures and non-specificity of currently available antigen-capture ELISA tests. In this study, a one-tube fluorescent probe based real time RT-PCR method was developed for quantification of ALV-J and compared with available quantification methods. Cell lysates with different TCID(50)s determined by cell culture and antigen capture ELISA (ag-ELISA) were used for one-tube real time RT-PCR using fluorogenic probe and quantitative competitive RT-PCR (QC-RT-PCR). The results of QC-RT-PCR and real time RT-PCR were highly correlated to the TCID(50)s determined by conventional culture methods. They were also very specific, sensitive, easy to perform, reproducible, and rapid compared with conventional methods. These RT-PCR based quantification methods of ALV-J viral RNA will be useful for virological and pathogenesis studies.

Animals↗

PubMedDate not supplied

Genetic alterations in K-ras and p53 cancer genes in lung neoplasms from Swiss (CD-1) male mice exposed transplacentally to AZT.

A transplacental carcinogenicity study was conducted by exposing pregnant Swiss (CD-1) mice to 0, 50, 100, 200, or 300 mg of 3'-azido-3'-deoxythymidine (AZT)/kg bw/day, through a 18 to 19-day gestation [National Toxicology Program, NIH Pub. No. 04-4458, 2004]. The incidences of alveolar/bronchiolar adenomas and carcinomas, in the 200 and 300 mg/kg male treatment groups, were significantly greater than that of the controls. In the present study, we evaluated the benign and malignant lung neoplasms from this bioassay for point mutations, in the K-ras and p53 cancer genes that are often mutated in human lung tumors. K-ras and p53 mutations were detected by cycle sequencing of polymerase chain reaction-amplified DNA, isolated from formalin-fixed, paraffin-embedded neoplasms. K-ras mutations were detected in 25 of 38 (66%) of the AZT-induced lung tumors, and the predominant mutations were codon 12 G-->T transversions. p53 mutations were detected in 32 of 38 (84%) of the AZT-induced lung tumors, with the predominant mutations being exon 8, codon 285 A-->T transversions, and exon 6, codon 198 T-->A transversions. No K-ras or p53 mutations were detected in five tumors, examined from control mice. The patterns of mutations identified in the lung tumors suggest that incorporation of AZT or its metabolites into DNA, oxidative stress, and genomic instability may be the contributing factors to the mutation profile and development of lung cancer in these mice.

Animals↗

PubMedDate not supplied

Predominant K-ras codon 12 G --> A transition in chemically induced lung neoplasms in B6C3F1 mice.

Based on long-term toxicity and carcinogenicity studies in B6C3F1 mice conducted by the National Toxicology Program, 2,2-Bis(bromomethyl)-1,3-propanediol (BMP) and tetranitromethane (TNM) have been identified as carcinogens. Following 2 yr of exposure to 312, 625, or 1,250 ppm BMP in feed, or exposure to 0.5 or 2 ppm TNM by inhalation, increased incidences of lung neoplasms were observed in B6C3F1 mice at all exposure concentrations compared to unexposed mice. The present study characterizes genetic alterations in the K-ras protooncogene in BMP- and TNM-induced lung neoplasms, respectively, and compares the findings to spontaneous lung neoplasms from corresponding control mice. The frequencies of the K-ras mutations were 57% (29/51) in BMP-induced lung neoplasms compared to 15% (3/20) in lung neoplasms from dosed feed control mice, and 54% (14/26) in TNM-induced lung neoplasms compared to 60% (3/5) in lung neoplasms from inhalation control mice. G --> A transitions at the second base of the K-ras codon 12 (GGT --> GAT) were the most frequent pattern of K-ras mutations identified in BMP-induced (20/29) and TNM-induced lung neoplasms (13/14), which differed from the mutational patterns identified in the lung neoplasms from unexposed control mice. These results indicate that mutations in the K-ras gene are involved in B6C3F1 lung carcinogenesis following BMP- and TNM-exposure, and the high frequency and specificity of the ras mutation profile in lung neoplasms (G --> A transition) may be due to in vivo genotoxicity by the parent compounds or their metabolites.

Animals↗