Sung-Ho Goh

High levels of GDF15 in thalassemia suppress expression of the iron regulatory protein hepcidin

In thalassemia, deficient globin-chain production during erythropoiesis results in anemia. Thalassemia may be further complicated by iron overload (frequently exacerbated by blood transfusion), which induces numerous endocrine diseases, hepatic cirrhosis, cardiac failure and even death. Accumulation of iron in the absence of blood transfusions may result from inappropriate suppression of the iron-regulating peptide hepcidin by an erythropoietic mechanism. To test this hypothesis, we examined erythroblast transcriptome profiles from 15 healthy, nonthalassemic donors. Growth differentiation factor 15 (GDF15), a member of the transforming growth factor-β superfamily, showed increased expression and secretion during erythroblast maturation. Healthy volunteers had mean GDF15 serum concentrations of 450 ± 50 pg/ml. In comparison, individuals with β-thalassemia syndromes had elevated GDF15 serum levels (mean 66,000 ± 9,600 pg/ml; range 4,800–248,000 pg/ml; P < 0.05) that were positively correlated with the levels of soluble transferrin receptor, erythropoietin and ferritin. Serum from thalassemia patients suppressed hepcidin mRNA expression in primary human hepatocytes, and depletion of GDF15 reversed hepcidin suppression. These results suggest that GDF15 overexpression arising from an expanded erythroid compartment contributes to iron overload in thalassemia syndromes by inhibiting hepcidin expression.

Let-7 microRNAs are developmentally regulated in circulating human erythroid cells

BackgroundMicroRNAs are ~22nt-long small non-coding RNAs that negatively regulate protein expression through mRNA degradation or translational repression in eukaryotic cells. Based upon their importance in regulating development and terminal differentiation in model systems, erythrocyte microRNA profiles were examined at birth and in adults to determine if changes in their abundance coincide with the developmental phenomenon of hemoglobin switching.MethodsExpression profiling of microRNA was performed using total RNA from four adult peripheral blood samples compared to four cord blood samples after depletion of plasma, platelets, and nucleated cells. Labeled RNAs were hybridized to custom spotted arrays containing 474 human microRNA species (miRBase release 9.1). Total RNA from Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines provided a hybridization reference for all samples to generate microRNA abundance profile for each sample.ResultsAmong 206 detected miRNAs, 79% of the microRNAs were present at equivalent levels in both cord and adult cells. By comparison, 37 microRNAs were up-regulated and 4 microRNAs were down-regulated in adult erythroid cells (fold change > 2; p < 0.01). Among the up-regulated subset, the let-7 miRNA family consistently demonstrated increased abundance in the adult samples by array-based analyses that were confirmed by quantitative PCR (4.5 to 18.4 fold increases in 6 of 8 let-7 miRNA). Profiling studies of messenger RNA (mRNA) in these cells additionally demonstrated down-regulation of ten let-7 target genes in the adult cells.ConclusionThese data suggest that a consistent pattern of up-regulation among let-7 miRNA in circulating erythroid cells occurs in association with hemoglobin switching during the fetal-to-adult developmental transition in humans.

eIF3m expression influences the regulation of tumorigenesis-related genes in human colon cancer

Abnormal regulation of gene expression is essential for tumorigenesis. Recent studies indicate that regulation of oncogene expression and neoplastic transformation are controlled by subunits of eukaryotic translation initiation factors (eIFs). Here we focused on eIF3 performing a pivotal role in protein synthesis and the differential expression of its subunits in cancer. The most uncharacterized non-core subunit eIF3m was confirmed to be highly expressed in human cancer cell lines and colon cancer patient tissues. By expression silencing with eIF3m-specific small interfering RNA (siRNA), we confirmed that eIF3m influences cell proliferation, cell cycle progression and cell death in human colon cancer cell line HCT-116. Using a ribonomics approach, we identified a subset of elF3m-influenced genes and showed that the expression of two highly represented tumorigenesis-related genes, MIF and MT2, were affected by eIF3m at the mRNA level. We also confirmed eIF3m-dependent regulation of MT2A downstream molecule CDC25A, which is necessary for cell cycle progression in HCT-116 cells. These results suggest that eIF3m mediates regulation of tumorigenesis-related genes in human colon cancer. Further investigations on tumorigenesis-related genes and their regulation by eIFs will provide clues for designing targeted therapy for cancer.

Hembase: browser and genome portal for hematology and erythroid biology

Hembase (http://hembase.niddk.nih.gov) is an integrated browser and genome portal designed for web-based examination of the human erythroid transcriptome. To date, Hembase contains 15,752 entries from erythroblast Expressed Sequenced Tags (ESTs) and 380 referenced genes relevant for erythropoiesis. The database is organized to provide a cytogenetic band position, a unique name as well as a concise annotation for each entry. Search queries may be performed by name, keyword or cytogenetic location. Search results are linked to primary sequence data and three major human genome browsers for access to information considered current at the time of each search. Hembase provides interested scientists and clinical hematologists with a genome-based approach toward the study of erythroid biology.

Differential gene expression pattern in early gastric cancer by an integrative systematic approach.

To elucidate the molecular basis of early gastric cancer (EGC), the genome-wide expression pattern of cancer and normal tissues from 27 patients were analyzed by a microarray-based method. Using an integrative systematic bioinformatics approach, we classified the differentially expressed genes in EGC. Interestingly, the more highly expressed genes in EGC exhibited the most significant correlation with cell migration and metastasis. This implies that, even at the early stage of gastric cancer, the molecular properties usually observed in late-stage cancer are already present. Furthermore, we have found a novel association between the expression pattern and molecular pathways of EGC and estrogen receptor α (ERα)-negative breast cancer through cross-experimental analysis. These results provide new insights into the biological properties of EGC, as well as yielding useful basic data for the study of molecular mechanisms of EGC carcinogenesis.

CD44v8-10 as a potential theranostic biomarker for targeting disseminated cancer cells in advanced gastric cancer

Gastric cancer is the third most common cause of cancer mortality, and the survival rate of stage IV advanced gastric cancer (AGC) patients with distant metastasis is very low. Thus, the detection and eradication of disseminated cancer cells by targeting cell surface molecules in AGC would improve patient survival. The hyaluronic acid receptor, CD44, has various isoforms generated by alternative splicing, and some isoforms are known to be correlated to gastric cancer. In this study, to find out the most appropriate CD44v for targeting AGC, we analysed the expression differences of CD44 isoforms at the mRNA level in stomach cancer cell lines as well as in 74 patients with AGC by using exon-specific qRT-PCR. Among the CD44v isoforms, CD44v8-10 was determined as the most promising biomarker for the development of theranostic agents of gastric cancer. Next, we synthesised the conjugate of anti-CD44v9 antibody with near-infrared fluorophore or photosensitiser, and then demonstrated its feasibility for target cell-specific imaging and photoimmunotherapy in gastric cancer. As a result, these conjugates have clearly demarcated the surface of CD44v8-10 expressing cancer cells and showed efficient phototoxic effects. Therefore, this study revealed that CD44v8-10 is the efficient theranostic biomarker to target disseminated cancer cells in AGC.

Redox-Responsive Manganese Dioxide Nanoparticles for Enhanced MR Imaging and Radiotherapy of Lung Cancer

In this study, we synthesized manganese dioxide nanoparticles (MnO2 NPs) stabilized with biocompatible polymers (polyvinylpyrrolidone and polyacrylic acid) and analyzed their effect on non-small cell lung cancer (NSCLC) cells with or without gefitinib resistance in vitro. MnO2 NPs showed glutathione (GSH)-responsive dissolution and subsequent enhancement in magnetic resonance (MR) imaging. Of note, treatment with MnO2 NPs induced significant cytotoxic effects on NSCLC cells, and additional dose-dependent therapeutic effects were obtained upon X-ray irradiation. Normal cells treated with MnO2 NPs were viable at the tested concentrations. In addition, increased therapeutic efficacy could be achieved when the cells were treated with MnO2 NPs in hypoxic conditions. Therefore, we conclude that the use of MnO2 NPs in MR imaging and combination radiotherapy may be an efficient strategy for the imaging and therapy of NSCLC.

Crystal structures of spleen tyrosine kinase in complex with novel inhibitors: structural insights for design of anticancer drugs

Spleen tyrosine kinase (SYK) is a cytosolic nonreceptor protein tyrosine kinase that mediates key signal transduction pathways following the activation of immune cell receptors. SYK regulates cellular events induced by the B‐cell receptor and Fc receptors with high intrinsic activity. Furthermore, SYK has been regarded as an attractive target for the treatment of autoimmune diseases and cancers. Here, we report the crystal structures of SYK in complex with seven newly developed inhibitors (G206, G207, O178, O194, O259, O272, and O282) to provide structural insights into which substituents of the inhibitors and binding regions of SYK are essential for lead compound optimization. Our kinase inhibitors exhibited high inhibitory activities against SYK, with half‐maximal inhibitory concentrations (IC50) of approximately 0.7–33 nm, but they showed dissimilar inhibitory activities against KDR, RET, JAK2, JAK3, and FLT3. Among the seven SYK inhibitors, O272 and O282 exhibited highly specific inhibitions against SYK, whereas O194 exhibited strong inhibition of both SYK and FLT3. Three inhibitors (G206, G207, and O178) more efficiently inhibited FLT3 while still substantially inhibiting SYK activity. The binding mode analysis suggested that a highly selective SYK inhibitor can be developed by optimizing the functional groups that facilitate direct interactions with Asn499.

Cl‐IB‐MECA inhibits human erythropoiesis

Candidate drugs are being sought for the suppression of human erythropoiesis. Cl‐IB‐MECA [2‐chloro‐N6‐(3‐iodobenzyl)‐adenosine‐5′‐N‐methyluronamide] is a derivative of adenosine that inhibits the growth of leukaemic cell lines. To determine the effects of Cl‐IB‐MECA upon erythropoiesis, studies were performed by using an ex vivo culture system of primary human CD34+ cells. Cl‐IB‐MECA suppressed erythroblast growth and maturation at doses ≥50 μmol/l through a mechanism of cell cycle inhibition and accumulation of cells in the G1/G0 phase. These findings demonstrate that Cl‐IB‐MECA inhibits human erythropoiesis, and suggest that further consideration of this drug is warranted for patients with erythrocytosis or polycythemia syndromes.

Overexpression of KLHL23 protein from read‐through transcription of PHOSPHO2‐KLHL23 in gastric cancer increases cell proliferation

Gene fusion, as a prototypical pathognomonic mutation, contributes to genome complexity, and the cis‐transcription‐induced gene fusions generated by read‐through transcription of adjacent genes have been found to be important for tumor development. We screened read‐through transcription events from stomach adenocarcinoma RNA‐seq data and selected three candidates PHOSPHO2‐KLHL23, RPL17‐C18orf32, and PRR5‐ARHGAP8, to assess their biological role in gastric cancer. The expression of all three read‐through fusion transcripts was confirmed in gastric cancer cell lines and paired normal/tumor gastric cancer tissues by real‐time quantitative reverse transcription polymerase chain reaction and their expression was found to be significantly higher in the tumor (P < 0.05; n = 75). The correlation between the expression level and clinicopathological information was statistically analyzed. The level of the PHOSPHO2‐KLHL23 read‐through fusion transcript correlated with the Lauren classification and was significantly associated with the presence of perineural invasion. Overexpression of KLHL23 from PHOSPHO2‐KLHL23 read‐through transcript led to a significant increase in cell proliferation and resistance to anticancer drug treatment. Silencing of KLHL23 expression decreased cyclin D1 levels. The expression of KLHL23 from prevalent read‐through transcripts of PHOSPHO2‐KLHL23 in gastric cancer may undermine the efficacy of anticancer drug treatment.