Publications by authors named "Jikyoung Park"

Acute lymphoblastic leukemia (ALL) with hyperleukocytosis at diagnosis is associated with early morbidity and mortality due to complications of leukostasis. Of 535 pediatric ALL patients (January 2004 to December 2016 from the Yeungnam region of Korea), 72 (13.5%) patients with an initial white blood cell (WBC) count of ≥100×10/L were included in this study, of whom 38 patients had extreme hyperleukocytosis (WBC>200×10/L) at diagnosis.

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Objectives: We aimed to evaluate treatment outcomes of pediatric acute lymphoblastic leukemia (ALL) subgroups by risk-stratification, in the Yeungnam region of Korea.

Methods: We reviewed the courses of 409 newly diagnosed ALL patients from January 2004 to December 2013 in the Yeungnam region.

Results: All patients were classified into three risk groups: standard risk (SR, n=212), high risk (HR, n=153) and very high risk (VHR, n=44).

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Mdm2 E3 ubiquitin ligase-mediated p53 degradation is generally accepted as the major mechanism for p53 regulation; nevertheless, the in vivo significance of this function has not been unequivocally established. Here, we have generated an Mdm2(Y487A) knockin mouse; Mdm2(Y487A) mutation inactivates Mdm2 E3 ligase function without affecting its ability to bind its homolog MdmX. Unexpectedly, Mdm2(Y487A/Y487A) mice were viable and developed normally into adulthood.

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Ras association domain family protein 1A (RASSF1A) is a tumor suppressor gene silenced in cancer. Here we report that RASSF1A is a novel regulator of intestinal inflammation as Rassf1a(+/-) , Rassf1a(-/-) and an intestinal epithelial cell specific knockout mouse (Rassf1a (IEC-KO) ) rapidly became sick following dextran sulphate sodium (DSS) administration, a chemical inducer of colitis. Rassf1a knockout mice displayed clinical symptoms of inflammatory bowel disease including: increased intestinal permeability, enhanced cytokine/chemokine production, elevated nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB) activity, elevated colonic cell death and epithelial cell injury.

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The Ras effector NORE1 is frequently silenced in primary adenocarcinomas, although the significance of this silencing for tumorigenesis is unclear. Here we show that NORE1 induces polyubiquitination and proteasomal degradation of oncoprotein HIPK1 by facilitating its interaction with the Mdm2 E3 ubiquitin ligase. Endogenous HIPK1 is stabilized in Nore1-deficient mouse embryonic fibroblasts, and depletion of HIPK1 in NORE1-silenced lung adenocarcinoma cells inhibits anchorage-independent cell growth and tumour formation in nude mice.

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Epigenetic silencing of RASSF (Ras association domain family) genes RASSF1 and RASSF5 (also called NORE1) by CpG hypermethylation is found frequently in many cancers. Although the physiological roles of RASSF1 have been studied in some detail, the exact functions of RASSF5 are not well understood. Here, we show that RASSF5 plays an important role in mediating apoptosis in response to death receptor ligands, TNF-α and TNF-related apoptosis-inducing ligand.

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Granulocyte colony-stimulating factor (G-CSF)-mobilized donor graft tissue used for peripheral blood stem cell transplantation contains a large number of immature myeloid cells that suppress alloreactive donor T cells, resulting in an inhibition of acute graft-versus-host disease (GVHD). However, the molecular mechanism underlying the suppressive function of immature myeloid cells is not fully understood. Here, we investigated whether indoleamine 2,3-dioxygenase (IDO) is related to the suppressive mechanism of G-CSF-induced immature myeloid cells (gMCs).

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