Kyusam Choi

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (10)83.19 Total impact

  • No preview · Article · Aug 2013 · Cancer Research
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    [Show abstract] [Hide abstract] ABSTRACT: Ovarian clear cell adenocarcinoma (Ov-CCA) is a distinctive subtype of ovarian epithelial carcinoma. In this study, we performed array comparative genomic hybridization (aCGH) and paired gene expression microarray of 19 fresh-frozen samples and conducted integrative analysis. For the copy number alterations, significantly amplified regions (false discovery rate [FDR] q <0.05) were 1q21.3 and 8q24.3, and significantly deleted regions were 3p21.31, 4q12, 5q13.2, 5q23.2, 5q31.1, 7p22.1, 7q11.23, 8p12, 9p22.1, 11p15.1, 12p13.31, 15q11.2, 15q21.2, 18p11.31, and 22q11.21 using the Genomic Identification of Significant Targets in Cancer (GISTIC) analysis. Integrative analysis revealed 94 genes demonstrating frequent copy number alterations (>25% of samples) that correlated with gene expression (FDR <0.05). These genes were mainly located on 8p11.21, 8p21.2-p21.3, 8q22.1, 8q24.3, 17q23.2-q23.3, 19p13.3, and 19p13.11. Among the regions, 8q24.3 was found to contain the most genes (30 of 94 genes) including PTK2. The 8q24.3 region was indicated as the most significant region, as supported by copy number, GISTIC, and integrative analysis. Pathway analysis using differentially expressed genes on 8q24.3 revealed several major nodes, including PTK2. In conclusion, we identified a set of 94 candidate genes with frequent copy number alterations that correlated with gene expression. Specific chromosomal alterations, such as the 8q24.3 gain containing PTK2, could be a therapeutic target in a subset of Ov-CCAs.
    Full-text · Article · May 2013 · Cancer Genetics
  • Kyusam Choi · Hyunjeong Ju · Young Hyeh Ko
    [Show abstract] [Hide abstract] ABSTRACT: Copy number alteration was investigated in three cases of EBV + nodal peripheral T cell lymphoma of cytotoxic phenotype using Agilent array comparative genomic hybridization platform. While no recurrent abnormality among three cases was identified, genomic abnormalities involving 9p23.3, 16p13.3, and 7q34 were overlapped with changes reported in other type of NK or T cell lymphomas previously. Chromosomal region 9p23.3 contains CDKN2A and CDKN2B which are frequently mutated or deleted in various types of cancer and may be a target to find genes associated with the pathogenesis of EBV-positive nodal peripheral T cell lymphoma.
    No preview · Article · Feb 2013 · Methods in molecular biology (Clifton, N.J.)
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    [Show abstract] [Hide abstract] ABSTRACT: Lung adenocarcinoma, the most common subtype of non-small cell lung cancer, is responsible for more than 500,000 deaths per year worldwide. Here, we report exome and genome sequences of 183 lung adenocarcinoma tumor/normal DNA pairs. These analyses revealed a mean exonic somatic mutation rate of 12.0 events/megabase and identified the majority of genes previously reported as significantly mutated in lung adenocarcinoma. In addition, we identified statistically recurrent somatic mutations in the splicing factor gene U2AF1 and truncating mutations affecting RBM10 and ARID1A. Analysis of nucleotide context-specific mutation signatures grouped the sample set into distinct clusters that correlated with smoking history and alterations of reported lung adenocarcinoma genes. Whole-genome sequence analysis revealed frequent structural rearrangements, including in-frame exonic alterations within EGFR and SIK2 kinases. The candidate genes identified in this study are attractive targets for biological characterization and therapeutic targeting of lung adenocarcinoma.
    Full-text · Article · Sep 2012 · Cell
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    [Show abstract] [Hide abstract] ABSTRACT: AKT1 signaling pathway is important for the regulation of protein synthesis and cell survival with implications in carcinogenesis. In this study, we explored the prognostic significance of AKT1 pathway in intrahepatic cholangiocarcinomas. We investigated the status of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), phosphorylated (p) AKT1 (p-AKT1), p-mammalian target of rapamycin (p-MTOR), p-p70 ribosomal protein S6 kinase (p-RPS6KB2) and p-eukaryotic initiation factor 4E-binding protein-1 (p-EIF4EBP1) in 101 intrahepatic cholangiocarcinomas by immunohistochemistry. Western blot analysis was performed to verify the expression levels of p-AKT1 and p-MTOR. The relationship of protein expression with clinicopathological data and the correlations of protein expression levels were explored. The overexpression of p-AKT1, p-MTOR, and PTEN was associated with a better survival in patients with intrahepatic cholangiocarcinoma (P=0.0137, 0.0194, and 0.0337, respectively). In a multivariate analysis, PTEN was an independent prognostic factor, and p-AKT1 showed tendency (P=0.032 and 0.051, respectively). The overexpression of p-MTOR was correlated with well-to-moderately differentiated tumors (P<0.001) and tumors without metastasis (P=0.046). Expression levels of the AKT1 signaling pathway proteins in this study showed positive correlations with each other, except for PTEN. Aberrant expressions of p-AKT1 and p-MTOR in intrahepatic cholangiocarcinoma were associated with a favorable prognosis, possibly in a PTEN-independent manner. Our results indicate that dysregulation of the AKT1 pathway may have an important role in the development of intrahepatic cholangiocarcinoma, but not necessarily in the progression of the disease.
    Full-text · Article · Aug 2011 · Modern Pathology
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    [Show abstract] [Hide abstract] ABSTRACT: Ovarian cancer is a leading cause of death in women. Early detection of ovarian cancer is essential to decrease mortality. However, the early diagnosis of ovarian cancer is difficult due to a lack of clinical symptoms and suitable molecular diagnostic markers. Thus, identification of meaningful tumor biomarkers with potential clinical application is clearly needed. To search for a biomarker for the early detection of ovarian cancer, we identified human anterior gradient 2 (AGR2) from our systematic analysis of paired normal and ovarian tumor tissue cDNA microarray. We noted a marked overexpression of AGR2 mRNA and protein in early stage mucinous ovarian tumors compared to normal ovarian tissues and serous type ovarian tumors by Western blot analysis and immunohistochemistry. To further elucidate the role of AGR2 in ovarian tumorigenesis, stable 2774 human ovarian cancer cell lines overexpressing AGR2 were established. Forced expression of AGR2 in 2774 cells enhanced the growth and migration of ovarian cancer cells. AGR2 protein was detected in the serum of mucinous ovarian cancer patients by Western blot and ELISA analysis. Thus, AGR2 is a potential biomarker for the diagnosis of mucinous ovarian cancer and an ELISA assay may facilitate the early detection of mucinous ovarian cancer using patient serum.
    Full-text · Article · Feb 2011 · Experimental and Molecular Medicine
  • Seung Bae Rho · Kyusam Choi · Kyoungsook Park · Je-Ho Lee
    [Show abstract] [Hide abstract] ABSTRACT: Promyelocytic leukemia zinc finger is a negative regulator of cell cycle progression. In this study, we showed that PLZF inhibits endothelial cell angiogenesis using a human umbilical vein endothelial cell system. We also focused on characterizing the specific function of the BTB domain of PLZF as a novel apoptotic and anti-angiogenic protein via deletion mapping analysis. The BTB domain directly inhibited tube formation, as well as the biological functions of angiostatic activity in vivo, and reduced the expression of p-Akt and p-eNOS, which play a significant role in angiogenesis when stimulated by VEGF. These results strongly suggest that the BTB domain could potentially modulate the apoptotic and anti-angiogenic effects of PLZF.
    No preview · Article · Mar 2010 · Cancer letters
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    [Show abstract] [Hide abstract] ABSTRACT: During carcinogenesis, NF-gammaB mediates processes associated with deregulation of the normal control of proliferation, angiogenesis, and metastasis. Thus, suppression of NF-gammaB has been linked with chemoprevention of cancer. Accumulating findings reveal that heat shock protein 90 (HSP90) is a molecular chaperone and a component of the IgammaB kinase (IKK) complex that plays a central role in NF-gammaB activation. HSP90 also stabilizes key proteins involved in cell cycle control and apoptosis signaling. We have determined whether the exogenous administration of isoflavone-deprived soy peptide prevents 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced rat mammary tumorigenesis and investigated the mechanism of action. Dietary administration of soy peptide (3.3 g/rat/day) significantly reduced the incidence of ductal carcinomas (50%), the number of tumors per multiple tumor-bearing rats (49%; P<0.05), and extended the latency period of tumor development (8.07+/-0.92 weeks) compared to control diet animals (10.80+/-1.30; P<0.05). Our results have further demonstrated that soy peptide (1) dramatically inhibits the expression of HSP90, thereby suppressing signaling pathway leading to NF-gammaB activation; (2) induces expression of p21, p53, and caspase-3 proteins; and (3) inhibits expression of VEGF. In agreement with our in vivo data, soy peptide treatment inhibited the growth of human breast MCF-7 tumor cells in a dose-dependent manner and induced apoptosis. Taken together, our in vivo and in vitro results suggest chemopreventive and tumor suppressive functions of isoflavone-deprived soy peptide by inducing growth arrest and apoptosis.
    Preview · Article · Apr 2009 · Experimental and Molecular Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Bcl-2 is involved in the progression of human malignancies, but the precise role and mechanism of Bcl-2 for tumor invasion and metastasis remains unclear. In this study, we have investigated the role and mechanism of Bcl-2 on tumor cell invasion and metastasis by using Bcl-2 overexpressing non-small cell lung cancer cells. Matrix metalloproteinases (MMPs) are important proteins involved in the processes of tumor invasion and metastasis. In vitro Matrigel invasion assays showed that Bcl-2 overexpression increased tumor cell invasion by 15-fold. Moreover, Bcl-2 overexpression enhanced in vivo lung metastasis by 4-fold. Consistent with its effect on invasion and metastasis, Bcl-2 overexpression induced not only MMP-2 mRNA and its protein expression, but this also activated the pro-MMP-2 protein to its active form. To explore the induction mechanism of MMP-2 by Bcl-2, we investigated the effects of Bcl-2 overexpression on MMP-2 transcriptional regulation. Nuclear run-on assays showed a 6-fold increase in the transcription rate of MMP-2 mRNA in the Bcl-2 transfectants (H157/Bcl-2) compared with that of the H157/vector control cells (H157/C). Overexpression of Bcl-2 induced the nuclear transcription factor activator protein 1 family, including the c-Jun, JunD, c-Fos, FosB, and Fra-1 proteins. Reporter assays combined with deletion mutagenesis analysis and gel shift assays showed the involvement of activator protein 1 in the activation of MMP-2 promoter activity by Bcl-2. Taken together, we have shown that Bcl-2 promotes tumor invasion and lung metastasis by inducing MMP-2 gene expression through the combined action of transcriptional and posttranslational mechanisms.
    Preview · Article · Aug 2005 · Cancer Research
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    [Show abstract] [Hide abstract] ABSTRACT: The stability of wild-type p53 is critical for its apoptotic function. In some cancers, wild-type p53 is inactivated by interaction with viral and cellular proteins, and restoration of its activity has therapeutic potential. Here, we identify homeobox Msx1 as a p53-interacting protein and show its novel function as a p53 regulator. Overexpression of homeobox Msx1 induced apoptosis of cancer cells harboring nonfunctional wild-type p53 and suppressed growth of human tumor xenografts in nude mice. The homeodomain of Msx1 functions as a protein-protein interacting motif rather than a DNA-binding domain and is essential for stabilization, nuclear accumulation, and apoptotic function of wild-type p53. The identification of a novel function of Msx1 as a p53 regulator may open new avenues for developing improved molecular therapies for tumors with a nonmutational p53 inactivation mechanism.
    Full-text · Article · Mar 2005 · Cancer Research