Deog-Yeon Jo

Chemotaxis of primitive hematopoietic cells in response to stromal cell–derived factor-1

Stromal cell-derived factor-1 (SDF-1) provides a potent chemotactic stimulus for CD34(+) hematopoietic cells. We cultured mobilized peripheral blood (PB) and umbilical cord blood (CB) for up to 5 weeks and examined the migratory activity of cobblestone area-forming cells (CAFCs) and long-term culture-initiating cells (LTC-ICs) in a transwell assay. In this system, SDF-1 or MS-5 marrow stromal cells placed in the lower chamber induced transmembrane and transendothelial migration by 2- and 5-week-old CAFCs and LTC-ICs in 3 hours. Transmigration was blocked by preincubation of input CD34(+) cells with antibody to CXCR4. Transendothelial migration of CB CAFCs and LTC-ICs was higher than that of PB. We expanded CD34(+) cells from CB in serum-free medium with thrombopoietin, flk-2 ligand, and c-kit ligand, with or without IL-3 and found that CAFCs cultured in the absence of IL-3 had a chemotactic response equivalent to noncultured cells, even after 5 weeks. However, addition of IL-3 to the culture reduced this response by 20-50%. These data indicate that SDF-1 induces chemotaxis of primitive hematopoietic cells signaling through CXCR4 and that the chemoattraction could be downmodulated by culture ex vivo.

Downregulation of APE1/Ref-1 Is Involved in the Senescence of Mesenchymal Stem Cells†‡

The senescence of human mesenchymal stem cells (hMSCs) causes disruption of tissue and organ maintenance, and is thus an obstacle to stem cell‐based therapies for disease. Although some researchers have studied changes in the characteristics of hMSCs (decreases in differentiation ability and self‐renewal), comparing young and old ages, the mechanisms of stem cell senescence have not yet been defined. In this study, we developed a growth curve for human bone marrow derived MSCs (hBMSCs) which changes into a hyperbolic state after passage number 7. Senescence associated β‐galactosidase (SA β‐gal) staining of hBMSCs showed 10% in passage 9 and 45% in passage 11. We detected an increase in endogenous superoxide levels during senescence that correlated with senescence markers (SA β‐gal, hyperbolic growth curve). Interestingly, even though endogenous superoxide increased in a replicative senescence model, the expression of APE1/Ref‐1, which is sensitive to intracellular redox state, decreased. These effects were confirmed in a stress‐induced senescence model by exogenous treatment with H2O2. This change is related to the p53 activity that negatively regulates APE1/Ref‐1. p21 expression levels, which represent p53 activity, were transiently increased in passage 9, meaning that they correlated with the expression of APE1/Ref‐1. Overexpression of APE1/Ref‐1 suppressed superoxide production and decreased SA β‐gal in hBMSCs. In conclusion, intracellular superoxide accumulation appears to be the main cause of the senescence of hBMSCs, and overexpression of APE1/Ref‐1 can rescue cells from the senescence phenotype. Maintaining characteristics of hBMSCs by regulating intracellular reactive oxygen species production can contribute to tissue regeneration and to improved cell therapy. STEM CELLS 2009;27:1455–1462

Influence of enzyme and transporter polymorphisms on trough imatinib concentration and clinical response in chronic myeloid leukemia patients

BACKGROUND This study explored the impact of genetic polymorphisms in cytochrome P450 (CYP) enzymes and transporters on the plasma trough concentration of imatinib mesylate (IM) and clinical response in chronic myeloid leukemia (CML). PATIENTS AND METHODS In total, 82 patients with CML who had been administered 400 mg IM daily for over 6 months were genotyped for 11 single-nucleotide polymorphisms in nine genes (CYP3A4, CYP3A5, CYP2C9, CYP2C19, CYP2D6, ABCB1, SLC22A1, SLC22A2 and ABCG2) using blood samples. The trough imatinib concentration and clinical responses were assessed 6 months after the initiation of IM therapy. RESULTS The CC, CA and AA genotypes in ABCG2 421C>A gave significantly different frequencies for the major molecular response (MMR) (P = 0.02). However, no significant differences were found between the genotypes of the CYP enzymes and transporters identified in this study and the imatinib plasma trough concentrations and clinical response frequencies, except for the correlation of ABCG2 with MMR. CONCLUSIONS The results of the present study may indicate that the ABCG 421C>A genetic polymorphism influences the MMR of imatinib in patients with CML.

CXC chemokines and chemokine receptors in gastric cancer: From basic findings towards therapeutic targeting

Gastric cancer is the fourth most common cancer, and the second-highest cause of cancer-related deaths worldwide. Despite extensive research to identify novel diagnostic and therapeutic agents, patients with advanced gastric cancer suffer from a poor quality of life and poor prognosis, and treatment is dependent mainly on conventional cytotoxic chemotherapy. To improve the quality of life and survival of gastric cancer patients, a better understanding of the underlying molecular pathologies, and their application towards the development of novel targeted therapies, is urgently needed. Chemokines are a group of small proteins associated with cytoskeletal rearrangements, the directional migration of several cell types during development and physiology, and the host immune response via interactions with G-protein coupled receptors. There is also growing evidence to suggest that chemokines not only play a role in the immune system, but are also involved in the development and progression of tumors. In gastric cancer, CXC chemokines and chemokine receptors regulate the trafficking of cells in and out of the tumor microenvironment. CXC chemokines and their receptors can also directly influence tumorigenesis by modulating tumor transformation, survival, growth, invasion and metastasis, as well as indirectly by regulating angiogenesis, and tumor-leukocyte interactions. In this review, we will focus on the roles of CXC chemokines and their receptors in the development, progression, and metastasis of gastric tumors, and discuss their therapeutic potential for gastric cancer.

Direct and Indirect Effects of Androgens on Survival of Hematopoietic Progenitor Cells In Vitro

Androgens remain a common treatment for certain type of anemia, based upon its myelostimulating effects; however, it has not been established whether androgens affect apoptosis of hematopoietic progenitor cells (HPCs). We investigated the effects of the androgens, such as testosterone, 5β-dihydrotestosterone (5-DHT), and oxymetholone, on apoptosis of normal hematopoietic progenitor cells in vitro. Androgens did not rescue normal bone marrow (BM) CD34+ cells and colony-forming cells (CFCs), other than mature erythroid CFCs, from apoptosis induced by serum- and growth factor deprivation. Oxymetholone did not affect growth factor-mediated survival of normal CD34+ cells or its inhibition by interferon-gamma (IFN-γ). In a standard methylcellulose clonogenic assay, low concentrations of oxymetholone and 5-DHT stimulated the clonal growth of colony-forming unit (CFU)-erythroid, but did not affect growth of CFU-granulocyte/macrophage or burst-forming unit-erythroid. Oxymetholone and 5-DHT stimulated the production of stem cell factor in normal bone marrow stromal cells (BMSCs) via transcriptional regulation. In agreement with this, oxymetholone-treated BMSCs better supported the survival of HPCs. These data indicate that survival-enhancing or growth-stimulatory effects of androgens on hematopoietic progenitor cells are minimal and mostly restricted to mature erythroid progenitors, and its myelostimulating effects could be attributed, at least in part, to the stimulation of production of hematopoietic growth factors in BMSCs.

Multiple myeloma in Korea: past, present, and future perspectives. Experience of the Korean Multiple Myeloma Working Party.

The incidence of multiple myeloma suggests an ethnic difference. Compared to Caucasians, who have an incidence rate of 3–5/100,000, Asians show much lower incidence rate compared to them, in the range of 0.5–3/100,000. In Korea, The very first case report of multiple myeloma was published in 1959 [1], and was followed by a few case reports until the 1970s. Since that time, the number of cases of multiple myeloma in Korea increased steadily, reaching 100 cases/year in 1990 [2] and 500 cases/year in 2000 [3], and it is still going up. Currently in Korea, 1,000 patients are estimated to be diagnosed with multiple myeloma, and 700 patients are assumed to die of this disease every year, and 4,000–5,000 patients are suffering from this disease [4]. The most updated, age-standardized, incidence rate of multiple myeloma in Korea is 1.4/100,000, and ranked as the third most common among the hematologic malignancies, only surpassed by non-Hodgkin’s lymphoma and acute myeloid leukemia [5]. Besides, the mortality from multiple myeloma

Expression regulation and function of Pref-1 during adipogenesis of human mesenchymal stem cells (MSCs).

Preadipocyte Factor 1 (Pref-1), also known as Delta-like Protein 1 (DLK-1) is an epidermal growth factor-like domain-containing trans-membrane protein that is involved in adipogenesis and cell fate decision. Its function in adipogenesis is reported inconsistently based on different cellular model systems. Here, by using human mesenchymal stem cells (MSCs), we show that Pref-1 is modulated by both dexamethasone and 3-isobutyl-1methylxanthine (IBMX), two components of the adipogenic induction mixture during the adipogenesis in vitro. IBMX induces the expression of Pref-1 in a time- and dose-dependent manner through cyclic AMP and cyclic GMP independent pathway and attenuates adipocyte differentiation by down-regulating PPARgamma (peroxisome proliferator activated receptor gamma) expression. Dexamethasone, on the other hand, is capable of subduing the inhibitory effect of IBMX-induced Pref-1 and initiating the adipogenesis by up-regulating PPARgamma expression. Moreover, the treatment of IBMX or dexamethasone alone fails to develop MSCs into mature adipocytes, however, treating cells with both IBMX and dexamethasone leads to a complete adipocyte differentiation as evaluated by lipid-droplet formation. Taken together, our study demonstrates that IBMX accelerates accumulation of lipid in MSCs only under the circumstance that the negative effect of Pref-1 induced by IBMX on the adipogenesis is overcome by dexamethasone.

Clinical implications of elevated antiphospholipid antibodies in adult patients with primary immune thrombocytopenia.

Background/Aims Antiphospholipid antibodies (aPL) have been detected in various proportions of patients with primary immune thrombocytopenia (ITP), but the clinical significance of this is debatable. The present study aimed to determine the frequency and clinical implications of elevated aPL in adult patients with ITP. Methods We prospectively studied newly diagnosed adult patients with ITP who were enrolled between January 2003 and December 2008 at Chungnam National University Hospital. They were evaluated for the presence of lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) at diagnosis and were followed for the development of thrombosis. Results Seventy consecutive patients with ITP (median age, 48 years; range, 18 to 79) were enrolled. Twenty patients (28.5%) were positive for aPL at the time of diagnosis: aCL alone in 15 (75%), aCL and LA in two (10%), and LA alone in three (15%). Patients who had platelet counts < 50,000/µL were administered oral prednisolone with or without intravenous immune globulin. No difference was found between the aPL-positive and -negative groups regarding gender, initial platelet count, and response to the therapy. After a median follow-up of 20 months (range, 2 to 68), two of 20 patients who were aPL-positive (10%) developed thrombosis, whereas no thrombotic event was found among those who were aPL-negative. Conclusions Our data suggest that aPL levels should be determined at the initial presentation of ITP and that patients found to be aPL-positive should receive closer follow-up for thrombotic events.

Human bone marrow endothelial cells elaborate non-stromal-cell-derived factor-1 (SDF-1)-dependent chemoattraction and SDF-1-dependent transmigration of haematopoietic progenitors

Summary. This study investigated human bone marrow endothelial cells (BMEC) chemoattractive activity in relation to haematopoietic cell trafficking. BMEC‐conditioned medium induced chemoattraction of haematopoietic progenitor cells. Migration was not inhibited by pretreating the cells with pertussis toxin (PTX) or 12G5, indicating that the chemoattractive activity was not dependent on stromal‐cell‐derived factor‐1 (SDF‐1). Spontaneous migration, but not SDF‐1‐mediated chemotaxis of haematopoietic progenitors, was better supported by BMEC as compared with umbilical vein endothelial cells. The superior migration was abolished by pretreating the cells with PTX, indicating that BMEC‐derived SDF‐1 favours bone marrow endothelium, with better transmigration of haematopoietic progenitors.

Dexamethasone and hypoxia upregulate CXCR4 expression in myeloma cells

We investigated the modulation of CXCR4 expression by cytokines, dexamethasone, and hypoxia in myeloma cells in vitro. Tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta1 (TGF-β1), and vascular endothelial growth factor (VEGF) enhanced CXCR4 expression in RPMI8226 cells. In the myeloma cell lines examined and primary bone marrow (BM) CD138+ cells, dexamethasone enhanced CXCR4 expression both in the cytoplasm and on the cell surface, while downregulating SDF-1 expression and secretion in BM stromal cells. Incubation of cells under hypoxic conditions (1% O2) also induced upregulation of CXCR4 in the cytoplasm and on the cell surface and enhanced chemotaxis in response to stromal cell-derived factor-1 (SDF-1). Cell surface CXCR4 expression was more prominent in annexin V-positive apoptotic cells. Given the roles of the SDF-1/CXCR4 axis in the development and progression of myeloma, CXCR4-downregulating agents may enhance the antitumor effects of dexamethasone.