Yon Ko

Osteopontin is a hematopoietic stem cell niche component that negatively regulates stem cell pool size

Stem cells reside in a specialized niche that regulates their abundance and fate. Components of the niche have generally been defined in terms of cells and signaling pathways. We define a role for a matrix glycoprotein, osteopontin (OPN), as a constraining factor on hematopoietic stem cells within the bone marrow microenvironment. Osteoblasts that participate in the niche produce varying amounts of OPN in response to stimulation. Using studies that combine OPN-deficient mice and exogenous OPN, we demonstrate that OPN modifies primitive hematopoietic cell number and function in a stem cell–nonautonomous manner. The OPN-null microenvironment was sufficient to increase the number of stem cells associated with increased stromal Jagged1 and Angiopoietin-1 expression and reduced primitive hematopoietic cell apoptosis. The activation of the stem cell microenvironment with parathyroid hormone induced a superphysiologic increase in stem cells in the absence of OPN. Therefore, OPN is a negative regulatory element of the stem cell niche that limits the size of the stem cell pool and may provide a mechanism for restricting excess stem cell expansion under conditions of niche stimulation.

Efficacy of TG101348, a Selective JAK2 Inhibitor, in Treatment of a Murine Model of JAK2V617F-Induced Polycythemia Vera

We report that TG101348, a selective small-molecule inhibitor of JAK2 with an in vitro IC50 of approximately 3 nM, shows therapeutic efficacy in a murine model of myeloproliferative disease induced by the JAK2V617F mutation. In treated animals, there was a statistically significant reduction in hematocrit and leukocyte count, a dose-dependent reduction/elimination of extramedullary hematopoiesis, and, at least in some instances, evidence for attenuation of myelofibrosis. There were no apparent toxicities and no effect on T cell number. In vivo responses were correlated with surrogate endpoints, including reduction/elimination of JAK2V617F disease burden assessed by quantitative genomic PCR, suppression of endogenous erythroid colony formation, and in vivo inhibition of JAK-STAT signal transduction as assessed by flow cytometric measurement of phosphorylated Stat5.

Comparison of rapidly cycled tandem high-dose chemotherapy plus peripheral-blood stem-cell support versus dose-dense conventional chemotherapy for adjuvant treatment of high-risk breast cancer: results of a multicentre phase III trial

BACKGROUND Breast cancer with extensive axillary-lymph-node involvement has a poor prognosis after conventional treatment. In trials with historical controls, high-dose chemotherapy produced improved outcomes. We compared an intensive double-cycle high-dose chemotherapy regimen with an accelerated conventionally dosed regimen in high-risk breast cancer in a multicentre trial. METHODS Patients with at least nine positive nodes were randomly assigned either two courses of accelerated (2-week intervals, with filgrastim support), conventionally dosed epirubicin and cyclophosphamide followed by two courses of high-dose chemotherapy (epirubicin, cyclophosphamide, and thiotepa supported by peripheral-blood progenitors) or four identical cycles of epirubicin and cyclophosphamide followed by three cycles of accelerated cyclophosphamide, methotrexate, and fluorouracil. The primary endpoint was event-free survival. Analyses were done both by intention to treat and per protocol. FINDINGS 403 patients were enrolled; 201 were assigned high-dose chemotherapy and 202 conventional treatment. The mean number of positive nodes was 17.6, and median follow-up was 48.6 months. 4-year event-free survival (intention-to-treat analysis) was 60% (95% CI 53-67) in the high-dose chemotherapy group and 44% (37-52) in the control group (p=0.00069). The corresponding overall survival was 75% (69-82) versus 70% (64-77; p=0.02). There were no treatment-related deaths. INTERPRETATION Our finding of significant improvements in both event-free and overall survival for high-dose chemotherapy compared with a dose-dense conventional regimen contrasts with the results of other studies. The discrepancy might be due partly to design differences (tandem, brief induction) between our regimen and those studied in other trials. This approach merits further study.

Green tea compounds inhibit tyrosine phosphorylation of PDGF β-receptor and transformation of A172 human glioblastoma.

The effect of the green tea compounds 2‐(3,4‐dihydroxyphenyl)‐3,4‐dihydro‐2H‐1‐benzopyran‐3,5,7‐triol (catechin), epicathechin (EC), epigallocathechin‐3 gallate (EGCG), epicathechin‐3 gallate (ECG) and catechin‐3 gallate (CG) on the tyrosine phosphorylation of PDGF β‐receptor (PDGF‐Rβ) and on the anchorage‐independent growth of A172 glioblastoma cells in semisolid agar has been investigated. Treatment of A172 glioblastoma with 50 μM CG, ECG, EGCG and 25 μM Tyrphostin 1296 resulted in an 82±17%, 77±21%, 75±8% and 55±11%, respectively (mean±S.D., n=3) inhibition of the PDGF‐BB‐induced tyrosine phosphorylation of PDGF‐Rβ. The PDGF‐Rβ downstream intracellular transduction pathway including tyrosine phosphorylation of phospholipase C‐γ1 (PLC‐γ1) and phosphatidylinositol 3′‐kinase (PI 3′‐K) was also inhibited. Spheroid formation was completely inhibited by 50 μM ECG, CG, EGCG and by 25 μM Tyrphostin 1296. We conclude that catechins of the green tea possessing the gallate group in their chemical structure act as anticancer agents probably partly via their ability to suppress the tyrosine kinase activity of the PDGF‐Rβ.

Risk of estrogen receptor-positive and -negative breast cancer and single-nucleotide polymorphism 2q35-rs13387042

BACKGROUND A recent genome-wide association study identified single-nucleotide polymorphism (SNP) 2q35-rs13387042 as a marker of susceptibility to estrogen receptor (ER)-positive breast cancer. We attempted to confirm this association using the Breast Cancer Association Consortium. METHODS 2q35-rs13387042 SNP was genotyped for 31 510 women with invasive breast cancer, 1101 women with ductal carcinoma in situ, and 35 969 female control subjects from 25 studies. Odds ratios (ORs) were estimated by logistic regression, adjusted for study. Heterogeneity in odds ratios by each of age, ethnicity, and study was assessed by fitting interaction terms. Heterogeneity by each of invasiveness, family history, bilaterality, and hormone receptor status was assessed by subclassifying case patients and applying polytomous logistic regression. All statistical tests were two-sided. RESULTS We found strong evidence of association between rs13387042 and breast cancer in white women of European origin (per-allele OR = 1.12, 95% confidence interval [CI] = 1.09 to 1.15; P(trend) = 1.0 x 10(-19)). The odds ratio was lower than that previously reported (P = .02) and did not vary by age or ethnicity (all P > or = .2). However, it was higher when the analysis was restricted to case patients who were selected for a strong family history (P = .02). An association was observed for both ER-positive (OR = 1.14, 95% CI = 1.10 to 1.17; P = 10(-15)) and ER-negative disease (OR = 1.10, 95% CI = 1.04 to 1.15; P = .0003) and both progesterone receptor (PR)-positive (OR = 1.15, 95% CI = 1.11 to 1.19; P = 5 x 10(-14)) and PR-negative disease (OR = 1.10, 95% CI = 1.06 to 1.15; P = .00002). CONCLUSION The rs13387042 is associated with both ER-positive and ER-negative breast cancer in European women.

Common Breast Cancer Susceptibility Loci Are Associated with Triple-Negative Breast Cancer

Triple-negative breast cancers are an aggressive subtype of breast cancer with poor survival, but there remains little known about the etiologic factors that promote its initiation and development. Commonly inherited breast cancer risk factors identified through genome-wide association studies display heterogeneity of effect among breast cancer subtypes as defined by the status of estrogen and progesterone receptors. In the Triple Negative Breast Cancer Consortium (TNBCC), 22 common breast cancer susceptibility variants were investigated in 2,980 Caucasian women with triple-negative breast cancer and 4,978 healthy controls. We identified six single-nucleotide polymorphisms, including rs2046210 (ESR1), rs12662670 (ESR1), rs3803662 (TOX3), rs999737 (RAD51L1), rs8170 (19p13.1), and rs8100241 (19p13.1), significantly associated with the risk of triple-negative breast cancer. Together, our results provide convincing evidence of genetic susceptibility for triple-negative breast cancer.

Association of ESR1 gene tagging SNPs with breast cancer risk

We have conducted a three-stage, comprehensive single nucleotide polymorphism (SNP)-tagging association study of ESR1 gene variants (SNPs) in more than 55,000 breast cancer cases and controls from studies within the Breast Cancer Association Consortium (BCAC). No large risks or highly significant associations were revealed. SNP rs3020314, tagging a region of ESR1 intron 4, is associated with an increase in breast cancer susceptibility with a dominant mode of action in European populations. Carriers of the c-allele have an odds ratio (OR) of 1.05 [95% Confidence Intervals (CI) 1.02-1.09] relative to t-allele homozygotes, P = 0.004. There is significant heterogeneity between studies, P = 0.002. The increased risk appears largely confined to oestrogen receptor-positive tumour risk. The region tagged by SNP rs3020314 contains sequence that is more highly conserved across mammalian species than the rest of intron 4, and it may subtly alter the ratio of two mRNA splice forms.

One-Carbon Metabolism and Breast Cancer Risk: No Association of MTHFR, MTR, and TYMS Polymorphisms in the GENICA Study from Germany

Neoplastic development and growth are suspected to be influenced by availability and metabolism of folate due to effects on gene expression through DNA methylation and on genome integrity through DNA synthesis and repair ([1][1]-[3][2]). Key enzymatic regulators are methylene-tetrahydrofolate

Mechanisms of the inhibitory effects of epigallocatechin-3 gallate on platelet-derived growth factor-BB-induced cell signaling and mitogenesis

An enhanced activity of receptor tyrosine kinases (RTKs), such as the platelet‐derived growth factor (PDGF) α‐receptor (PDGF‐Rα) or the PDGF β‐receptor (PDGF‐Rβ), is involved in the development of proliferative diseases. We have previously demonstrated that green tea catechins containing a galloyl group in the third position of the catechin structure interfere with PDGF‐BB‐ induced mitogenic signaling pathways by inhibiting tyrosine phosphorylation of the PDGF‐Rβ. However, the underlying cellular and molecular mechanisms are unknown. Using human vascular smooth muscle cells (VSMC) and porcine endothelial cells (AEC) stably transfected with PDGF‐Rα and ‐β, respectively, we demonstrate that EGCG preferably inhibited PDGF‐BB isoform‐mediated signal transduction pathways and cell proliferation. To elucidate cellular and molecular mechanisms of the inhibitory effects of EGCG, we studied the distribution of incorporated EGCG into cellular compartments after subcellular fractionation. Interestingly, most (85%) of the EGCG was found in the cytoplasmic fraction, whereas only ∼2% was found within the cell plasma membranes. However, no alteration of membrane fluidity has been observed after treatment of VSMC with 50 µM EGCG. Binding studies with [125I]‐PDGF‐BB on EGCG‐treated VSMC demonstrated that the specific binding of PDGF‐BB was completely abolished. Moreover, when [125I]‐PDGF‐BB was incubated with VSMC in the presence of EGCG, a 50% reduction of cellular [125I]‐PDGF‐BB binding was observed. Our findings suggest that plasma membrane incorporated EGCG or soluble EGCG directly interacts with PDGF‐BB, thereby preventing specific receptor binding.

Stromal cell‐derived factor 1α (SDF‐1α) induces gene‐expression of early growth response‐1 (Egr‐1) and VEGF in human arterial endothelial cells and enhances VEGF induced cell proliferation

Abstract. Stromal cell‐derived factor‐1 (SDF‐1), mainly known as a chemotactic factor for haematopoietic progenitor cells, also provides angiogenetic potency. Since the intracellular signalling of SDF‐1‐induced neovascularization remains unclear, we studied in human umbilical arterial endothelial cells (HUAEC) the influence of SDF‐1α on induction of the genes of early growth response‐1 (Egr‐1) and VEGF, as well as the activation of extracellular regulated kinases (ERK) 1/2, which are all known to be involved in endothelial cell proliferation. We found a time‐dependent induction of Egr‐1 and VEGF mRNA expression and phosphorylation of ERK1/2 by SDF‐1α. Furthermore, we demonstrated that Egr‐1 expression is dependent on ERK 1/2 activation. Finally, we tried to confirm the relevance of the induced gene expression by detecting the [3H]thymidine incorporation as a marker for cell proliferation in HUAEC after stimulation with SDF‐1α alone or together with VEGF. This particular test showed, that SDF‐1α alone has no effect, but is able to significantly enhance VEGF induced DNA synthesis. In summary, SDF‐1α is involved in different steps of endothelial cell proliferation, but, since Egr‐1 and VEGF offer different functions, it may also play a so far undefined role on other conditions of the endothelium.