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Y K Kang

Publications and source records attributed to Y K Kang.

At least 19 recordsLinked to original sources
PubMed2003

Nuclear reprogramming of cloned embryos produced in vitro.

Despite the fact that cloned animals derived from somatic cells have been successfully generated in a variety of mammalian species, there are still many unsolved problems with current cloning technology. Somatic cell nuclear transfer has shown several developmental aberrancies, including a high rate of abortion during early gestation and increased perinatal death. One cause of these developmental failures of cloned embryos may reside in the epigenetic reprogramming of somatic donor genome. In mammals, DNA methylation is an essential process in the regulation of transcription during embryonic development and is generally associated with gene silencing. A genome-wide demethylation may be a prerequisite for the formation of pluripotent stem cells that are important for later development. We analyzed methylation patterns in cloned bovine embryos to monitor the epigenetic reprogramming process of donor genomic DNA. Aberrant methylation profiles of cloned bovine embryos were observed in various genomic regions, except in single-copy gene sequences. The overall genomic methylation status of cloned embryos was quite different from that of normal embryos produced in vitro or in vivo. These results suggest that the developmental failures of cloned embryos may be due to incomplete epigenetic reprogramming of donor genomic DNA. We expect that advances in understanding the molecular events for reprogramming of donor genome will contribute to clarify the developmental defects of cloned embryos.

Animals↗
PubMed2003

Phase II study of capecitabine plus cisplatin as first-line chemotherapy in advanced biliary cancer.

BACKGROUND: A phase II study was conducted to assess the efficacy and tolerability of substituting capecitabine for 5-fluorouracil in combination with cisplatin in patients with advanced biliary cancer. PATIENTS AND METHODS: Patients with previously untreated metastatic or unresectable measurable biliary adenocarcinoma received oral capecitabine 1250 mg/m(2) twice daily on days 1-14, and intravenous cisplatin 60 mg/m(2) on day 1. This cycle was repeated every 21 days. RESULTS: Forty-two patients were enrolled in this study. Of these, 38 were assessable for efficacy and 41 were assessable for safety. A median of three cycles of treatment (range one to eight) were administered. One patient achieved a complete response, and eight had partial responses, giving an overall response rate of 21.4% in the intention-to-treat population (95% confidence interval 9.1% to 33.9%). The median response duration was 5.1 months. The median time to progression and median overall survival were 3.7 and 9.1 months, respectively. The most common grade 3/4 adverse events were neutropenia (20% of patients), vomiting (12%), diarrhea (7%) and stomatitis (5%). There were no treatment-related deaths. CONCLUSIONS: The combination of capecitabine and cisplatin has promising antitumor activity and is well tolerated in patients with advanced biliary cancer.

Administration, Oral↗
PubMed2002

Phase II study of capecitabine plus cisplatin as first-line chemotherapy in advanced gastric cancer.

BACKGROUND: A phase II study was conducted to assess the efficacy and tolerability of combination therapy with capecitabine and cisplatin in patients with advanced gastric cancer. PATIENTS AND METHODS: Patients with previously untreated metastatic or unresectable measurable gastric adenocarcinoma received oral capecitabine 1250 mg/m(2) twice daily, days 1-14, and i.v. cisplatin 60 mg/m(2) on day 1. This cycle was repeated every 3 weeks. RESULTS: Forty-two patients were enrolled in this study. Of these, 38 patients were assessable for efficacy and 40 were assessable for toxicity. One patient achieved a complete response and 22 patients had partial responses, giving an overall response rate of 54.8% in the intention-to-treat population (95% confidence interval 39.8% to 69.8%). The median time to progression was 6.3 months and the median overall survival was 10.1 months. The principal adverse events were neutropenia and hand-foot syndrome. Grade 3/4 adverse events were neutropenia (32.5% of patients), thrombocytopenia (10%), stomatitis (2.5%) and diarrhea (5%). Grade 2 and 3 hand-foot syndrome occurred in 20% and 7.5% of patients, respectively. There were no treatment-related deaths. CONCLUSIONS: The combination of capecitabine and cisplatin is active and well tolerated in patients with advanced gastric cancer.

Adenocarcinoma↗
PubMed2001

Typical demethylation events in cloned pig embryos. Clues on species-specific differences in epigenetic reprogramming of a cloned donor genome.

We investigated whether a genomic demethylation process occurs in pig preimplantation embryos produced by either normal fertilization or somatic cell nuclear transfer. The methylation status of the centromeric satellite and the PRE-1 short interspersed element (SINE) sequences was characterized using bisulfite-sequencing technology. Typical demethylation processes were identified in these repetitive sequences of the cloned donor genome during cleavage, the patterns of which were similar to the ones detected in fertilized counterparts. These findings are different from previous observations with cloned bovine embryos where various repeated regions of the donor genome exhibited aberrant methylation patterns. Our results indicate that species-specific differences exist in modifying the epigenetic status of cloned donor genomes.

Animals↗
PubMed2001

Influence of oocyte nuclei on demethylation of donor genome in cloned bovine embryos.

We recently demonstrated that satellite regions exhibit an aberrant DNA methylation in cloned bovine embryos. Here, we examined, using bisulfite-sequencing technology, whether the inefficient demethylation of cloned donor genomes could be rescued by the presence of oocytic nuclei. Both AciI digestion and sequencing analyses showed that satellite sequence was demethylated more efficiently in cloned tetraploid blastocysts than in diploid clones. When methyl-CpG density (the number of methyl-CpG sites per string) was scored, a significant decrease was observed in tetraploids (P<0.001). These results suggest that unknown mechanisms provided by oocytic nuclei could assist the demethylation of satellite sequences in tetraploid clones.

Animals↗
PubMed2001

The protective role of HSP90 against 3-hydroxykynurenine-induced neuronal apoptosis.

3-hydroxykynurenine (3HK), an endogenous metabolite of tryptophan in the kynurenine pathway, is a potential neurotoxin in several neurodegenerative disorders. Stabilizing protein structure, heat shock proteins (HSPs) have diverse roles as molecular chaperones to mediate stress tolerance. In the present study, we investigated the possible protective role of HSPs against 3HK induced neuronal cell death. Here we report that 3HK induced in a dose- and time-dependent manner neuronal cell death in neuroblastoma SK-N-SH cells. The cell death showed characteristic apoptotic features such as cell shrinkage, plasma membrane blebbing, chromatin condensation, and nuclear condensation and fragmentation. Furthermore, SK-N-SN cells were protected from 3HK induced cytotoxicity by prior elevation of HSPs expression. Our results show that the protective effect was abolished by HSP90 anti-sense oligonucleotides while not by HSP27 and HSP70 anti-sense oligonucleotides. Also, our result shows that HSP90 effectively inhibits caspases activities leading to the apoptosis. These results suggest that 3HK induces apoptosis in neuroblastoma SK-N-SN cells and that HSP90 is major contributing protein component of protection against 3HK induced apoptosis.

Apoptosis↗
PubMed2001

Differential inheritance modes of DNA methylation between euchromatic and heterochromatic DNA sequences in ageing fetal bovine fibroblasts.

To elucidate overall changes in DNA methylation occurring by inappropriate epigenetic control during ageing, we compared fetal bovine fibroblasts and their aged neomycin-resistant versions using bisulfite-PCR technology. Reduction in DNA methylation was observed in euchromatic repeats (18S-rRNA/art2) and promoter regions of single-copy genes (the cytokeratin/beta-lactoglobulin/interleukin-13 genes). Contrastingly, a stable maintenance of DNA methylation was revealed in various heterochromatic sequences (satellite I/II/alphoid and Bov-B). The differential inheritance mode of DNA methylation was confirmed through the analysis of individual neomycin-resistant clones. These global, multi-locus analyses provide evidence on the tendency of differential epigenetic modification between genomic DNA regions during ageing.

Animals↗
PubMed2001

Interleukin 12 gene therapy of cancer by peritumoral injection of transduced autologous fibroblasts: outcome of a phase I study.

A phase I dose-escalation clinical trial of peritumoral injections of interleukin 12 (IL-12)-transduced autologous fibroblasts was performed in patients with disseminated cancer for whom effective treatment does not exist. The goals of this study were to assess the safety and toxicities as well as the efficacy, and ancillarily the immunomodulatory effects, of peritumoral IL-12 gene transfer. Primary dermal fibroblasts cultured from the patients were transduced with retroviral vector carrying human IL-12 genes (p35 and p40) as well as the neomycin phosphotransferase gene (TFG-hIL-12-Neo). Patients received four injections at intervals of 7 days. Nine patients were enrolled in this dose-escalation study, with secreted IL-12 doses ranging from 300 ng/24 hr for the first three patients to 1000, 3000, and 5000 ng/24 hr for two patients in each subsequent dosage level. Although a definite statement cannot be made, there appears to be perturbation of systemic immunity. Also, the locoregional effects mediated by tumor necrosis factor alpha (TNF-alpha) and CD8+ T cells were observed with tumor regression. Treatment-related adverse events were limited to mild to moderate pain at the injection site; clinically significant toxicities were not encountered. Transient but clear reductions of tumor sizes were observed at the injected sites in four of nine cases, and at noninjected distant sites in one melanoma patient. Hemorrhagic necrosis of tumors was observed in two melanoma patients. These data indicate that gene therapy by peritumoral injection of IL-12-producing autologous fibroblasts is feasible, and promising in patients with advanced cancer.

Adult↗
PubMed2001

Developmental potential and transgene expression of porcine nuclear transfer embryos using somatic cells.

We examined whether porcine nuclear transfer (NT) embryos carrying somatic cells have a developmental potential and NT embryos carrying transformed fibroblasts express transgenes in the preimplantation stages. In Experiment 1, different activation methods were applied to NT embryos and the development rates were examined. Relative to A23187 only or A23187/6-DMAP, electrical pulse made a significant increase in both cleavage rate (58.1+/-13.9 or 60.7+/-6.3 vs. 74.9+/-7.5%) and development rate of NT embryos to the blastocyst stage (2.2+/-2.8 or 2.2+/-1.5 vs. 11.0+/-4.1%). In Experiment 2, in vitro developmental competence of NT embryos was investigated. The developmental rate to the blastocyst stage of NT embryos (9.9+/- 2.4% for cumulus cells and 9.8+/-1.6% for fibroblast cells) was significantly lower than that (22.9+/-3.5%) of IVF-derived embryos (P<0.01). NT blastocysts derived from either cumulus (28.9+/-11.4, n = 26) or fibroblast cells (30.2+/-9.9, n = 27) showed smaller mean nuclei numbers than IVF-derived blastocysts (38.6+/-10.4, n = 62) (P<0.05). In Experiment 3, nuclear transfer of porcine fibroblasts expressing the GFP (green fluorescent protein) gene resulted in green blastocysts without losing developmental potential. These results suggest that porcine embryos reconstructed by somatic cell nuclear transfer are capable of developing to preimplantation stage. We conclude that somatic cells expressing exogenous genes can be used as nuclei donors in the production of NT-mediated transgenic pig.

Adenine↗
PubMed2001

Cyclin D1 overexpression in hepatocellular carcinoma.

BACKGROUND/AIMS: Cyclin D1 gene amplification and cyclin D1 protein overexpression have been reported in various human tumors, including hepatocellular carcinoma (HCC). However, their significance is still controversial. In the present study, we examined the expression of cyclin D1 and its relationships to p53 and Ki-67 in HCCs. METHODS: The expression and topological distribution of cyclin D1, p53 and Ki-67 in 50 cases of HCC were examined immunohistochemically, and the relationship between the expression of these proteins and their pathologic features was investigated. RESULTS: Overexpression of cyclin D1 was noted in 58% of the HCC cases, and significantly associated with a well-differentiated histology and a low Ki-67 labeling index (LI). Cyclin D1 overexpression was also observed in all (7 of 7) dysplastic nodules and in non-neoplastic hepatocytes. On the other hand, aberrant p53 expression was detected in 36% of the cases, which showed positive relationships with poor differentiation, portal vein invasion, and KI-67 LI. Only eight of the 50 cases examined (16%) were positive for both cyclin D1 and p53, which showed only a small number of cyclin D1-positive cells. There was no significant relationship between the expressions of cyclin D1 and p53. CONCLUSIONS: Our results suggest that cyclin D1 overexpression may be an early event in hepatocarcinogenesis and that it plays a role in tumor differentiation. In addition, cyclin D1 expression is not correlated with tumor cell proliferation in HCCs.

Adult↗
PubMed2001

Aberrant methylation of donor genome in cloned bovine embryos.

Despite recent successes in cloning various animal species, the use of somatic cells as the source of donor nuclei has raised many practically relevant questions such as increased abortion rates, high birth weight and perinatal death. These anomalies may be caused by incomplete epigenetic reprogramming of donor DNA. Genome-wide demethylation occurs during early development, 'erasing' gamete-specific methylation patterns inherited from the parents. This process may be a prerequisite for the formation of pluripotent stem cells that are important for the later development. Here, we provide evidence that cloned bovine embryos may have impaired epigenetic reprogramming capabilities. We found highly aberrant methylation patterns in various genomic regions of cloned embryos. Cloned blastocysts closely resembled donor cells in their overall genomic methylation status, which was very different from that of normal blastocysts produced in vitro or in vivo. We found demethylation of the Bov-B long interspersed nuclear element sequence in normal embryos, but not in cloned embryos, in which the donor-type methylation was simply maintained during preimplantation development. There were also significant variations in the degree of methylation among individual cloned blastocysts. Our findings indicate that the developmental anomalies of cloned embryos could be due to incomplete epigenetic reprogramming of donor genomic DNA.

Animals↗
PubMed2001

Expression of Fas and Fas-related molecules in human hepatocellular carcinoma.

Many tumor cells, including hepatocellular carcinoma (HCC), express both Fas and its ligand on their surfaces, and it has remained a mystery why such cells do not spontaneously become apoptotic. In the current study, we analyzed the alterations of Fas structure and the expression of Fas and Fas ligand (FasL) and of Fas pathway inhibitors, including soluble Fas (sFas), Fas-associated phosphatase-1 (FAP-1), and bcl-2, in 50 cases of human HCC. Monoallelic loss of the Fas gene, as determined by loss of heterozygosity with intragenic polymorphisms, was observed in 5 of the 34 informative cases (15%), but none of the 50 cases showed Fas gene mutation. Expression of Fas and FasL was detected in 44 (88%) and 50 (100%) cases, respectively. sFas messenger RNA, as analyzed by in situ reverse-transcription polymerase chain reaction was expressed in 42 of the 50 cases (84%), and FAP-1 expression was observed in 40 of the 50 cases (80%). In contrast, none of the 50 cases showed bcl-2 expression. Our results showed that the majority of the HCCs (88%) coexpressed a death receptor, Fas and its cognate ligand, FasL, but all HCCs showed one or more alterations of the Fas pathway molecules known to inhibit Fas-mediated apoptosis. These findings suggest that the expression of sFas and FAP-1 and, in part, loss of Fas expression, rather than Fas gene alteration or bcl-2 expression, may be involved in the Fas resistance of HCC in vivo and that these mechanisms may play important roles in the pathogenesis of human HCC. HUM PATHOL 32:250-256.

Adult↗
PubMed2001

A prospective correlation of Laurén's histological classification of stomach cancer with clinicopathological findings including DNA flow cytometry.

Between November 1990 and December 1992, 217 patients with stomach cancer were enrolled in a prospective study evaluating the prognostic value of DNA flow cytometry. Laurén's histological type was evaluated in 216 cases, of which 102 (47%) were of the diffuse type, 74 (34%) were of the intestinal type, and 40 (19%) were mixed type tumors. Laurén's histological type showed a significant correlation with age (p = 0.028), sex (p = 0.004), tumor size (p = 0.002), T stage (p = 0.006), overall TNM stage (p = 0.008), histological grade (p < 0.001), and tumor ploidy (p < 0.001). Intestinal type stomach cancer showed a significantly higher proportion of aneuploidy [diffuse vs. intestinal type; 41/102 (40%) vs. 52/74 (70%)]. After a median follow-up of 66.1 months (range, 29.6-78.1), 110 of 216 patients (51%) survived. Patients with intestinal type stomach cancer had a significantly better survival than did those with diffuse type stomach cancer (64% vs. 42% of patients surviving, p = 0.020). Our study suggests that there are biological differences between the two subtypes of Laurén's classification of stomach cancer in addition to the morphological differences. Laurén's classification should remain valid in future studies investigating the pathogenetic and clinical aspects of stomach cancer.

Adult↗
PubMed2001

Bilateral conjunctival mucosa-associated lymphoid tissue lymphoma misdiagnosed as allergic conjunctivitis.

PURPOSE: This report aimed to discuss two nearly identical cases of primary conjunctival mucosa-associated lymphoid tissue (MALT) lymphoma mimicking allergic conjunctivitis. METHODS: Two patients were referred for intractability to conventional treatment of initial diagnoses of allergic conjunctivitis. On ocular examination, normally pigmented, giant papilla-like lesions were found bilaterally in the upper conjunctiva. Excisional biopsies were performed. RESULTS: Histopathologic and immunohistochemical examination of the conjunctival biopsies indicated MALT lymphoma in both patients. The patients subsequently received radiation therapy and achieved complete remission with no evidence of recurrence during follow-up periods of 13 and 11 months. CONCLUSION: Conjunctival low-grade lymphoma may share similar clinical features with allergic conjunctivitis. Ophthalmologists should be concerned that primary conjunctival low-grade malignant lymphoma can be misdiagnosed as allergic conjunctivitis

Adult↗
PubMed2001

Combination of oxaliplatin, fluorouracil, and leucovorin in the treatment of fluoropyrimidine-pretreated patients with metastatic colorectal cancer.

There has been no standard therapy for patients with metastatic colorectal cancer who have failed to first-line fluorouracil-based treatment. The present study was designed to assess the efficacy and toxicities of a combination of oxaliplatin, 5-fluorouracil (5-FU) and leucovorin in fluoropyrimidine-pretreated patients with metastatic colorectal cancer. Chemotherapy consisted of oxaliplatin 85 mg/m2 on day 1, followed by leucovorin 20 mg/m2 and 5-FU 1,200 mg/m2 on days 1 and 2. Treatment courses were repeated every two weeks. Thirty-nine patients were enrolled in this study. All patients previously received fluoropyrimidine-based chemotherapy. Thirty-one patients were assessable for response and 33 for treatment toxicity. Six patients required dose reduction of 5-FU due to grade III/IV cytopenia. Nausea/vomiting and peripheral neuropathy were common non-hematologic toxicities. Overall response rate was 42.0% including 3 complete response and 10 partial response. The median response duration was 91 days (range, 28-224+). The median duration of progression-free survival was 132 days (range, 40-308). A combination of oxaliplatin, 5-FU, and leucovorin showed high response rate in fluoropyrimidine-pretreated patients with metastatic colorectal cancer, but the duration of response was relatively short. It may be worthwhile to explore its therapeutic potential in the first-line treatment setting.

Adult↗
PubMed2000

Blastocyst viability and generation of transgenic cattle following freezing of in vitro produced, DNA-injected embryos.

This study examined whether the viability, determined in vitro, of DNA-injected bovine embryos produced in vitro was affected by freezing, and if the frozen embryos developed to term following transfer to recipients. In vitro fertilized zygotes were injected with the pBL1 gene and then co-cultured with mouse embryonic fibroblasts (MEF) in CR1aa medium. Embryos were prepared for cryopreservation by exposure to a 10% (v/v) glycerol solution, loaded into 0.25 ml straws and then frozen by conventional slow freezing. Thawing was by rapid warming in water (37 degrees C) and embryos were rehydrated in PBS diluents of 6%, 3% and 0% (v/v) glycerol supplemented with 0.25 M sucrose and 0.5% (w/v) BSA. In Experiment 1, blastocysts that developed from DNA-injected embryos were individually classified into three morphological groups and three stages of development prior to freezing. DNA-injected blastocysts of excellent quality at freezing showed a higher survival rate (78.8+/-10.6%) after thawing than those of good (60. 9+/-16.4%) or fair (12.5+/-5.9%) quality (P<0.05). Post-thaw survival rate, judged in vitro, increased with more advanced stage of blastocyst development at freezing (early 48.8+/-15.9%, mid 52. 1+/-12.6% and expanded 71.2+/-1.1; P<0.05). In Experiment 2, the frozen/thawed embryos were transferred to recipients to examine in vivo viability. Following transfer of one or two embryos per recipient, pregnancy rates at 60 days of gestation were 13.6% (13/96) for frozen embryos and 26.5% (43/162) for fresh embryos (P<0. 05). Of the 12 live calves born from the frozen/thawed embryos, two males (18.3%) were transgenic. None of the live-born calves derived from fresh embryos exhibited the transgene. One of transgenic bulls did not produce transgenic sperm. Three out of 23 calves (13.0%) produced from cows inseminated with semen of the other bull were transgenic, suggesting that this animal was a germ-line mosaic. These studies indicated that the viability of in vitro produced, DNA-injected bovine blastocysts was affected by freezing and by both the quality and stage of development of the embryo prior to freezing. The generation of transgenic cattle demonstrates that it is feasible to freeze DNA-injected, in vitro produced embryos.

Animals↗