J. Denry Sato

Heparin promotes the growth of human embryonic stem cells in a defined serum-free medium

A major limitation in developing applications for the use of human embryonic stem cells (HESCs) is our lack of knowledge of their responses to specific cues that control self-renewal, differentiation, and lineage selection. HESCs are most commonly maintained on inactivated mouse embryonic fibroblast feeders in medium supplemented with FCS, or proprietary replacements such as knockout serum-replacement together with FGF-2. These undefined culture conditions hamper analysis of the mechanisms that control HESC behavior. We have now developed a defined serum-free medium, hESF9, for the culture of HESCs on a type I-collagen substrate without feeders. In contrast to other reported media for the culture of HESCs, this medium has a lower osmolarity (292 mosmol/liter), l-ascorbic acid-2-phosphate (0.1 μg/ml), and heparin. Insulin, transferrin, albumin conjugated with oleic acid, and FGF-2 (10 ng/ml) were the only protein components. Further, we found that HESCs would proliferate in the absence of exogenous FGF-2 if heparin was also present. However, their growth was enhanced by the addition of FGF-2 up to 10 ng/ml although higher concentrations were deleterious in the presence of heparin.

Integrins Regulate Mouse Embryonic Stem Cell Self-Renewal

Extracellular matrix (ECM) components regulate stem‐cell behavior, although the exact effects elicited in embryonic stem (ES) cells are poorly understood. We previously developed a simple, defined, serum‐free culture medium that contains leukemia inhibitory factor (LIF) for propagating pluripotent mouse embryonic stem (mES) cells in the absence of feeder cells. In this study, we determined the effects of ECM components as culture substrata on mES cell self‐renewal in this culture medium, comparing conventional culture conditions that contain serum and LIF with gelatin as a culture substratum. mES cells remained undifferentiated when cultured on type I and type IV collagen or poly‐d‐lysine. However, they differentiated when cultured on laminin or fibronectin as indicated by altered morphologies, the activity of alkaline phosphatase decreased, Fgf5 expression increased, and Nanog and stage‐specific embryonic antigen 1 expression decreased. Under these conditions, the activity of signal transducer and activator of transcription (STAT)3 and Akt/protein kinase B (PKB), which maintain cell self‐renewal, decreased. In contrast, the extracellular signal‐regulated kinase (ERK)1/2 activity, which negatively controls cell self‐renewal, increased. In the defined conditions, mES cells did not express collagen‐binding integrin subunits, but they expressed laminin‐ and fibronectin‐binding integrin subunits. The expression of some collagen‐binding integrin subunits was downregulated in an LIF concentration‐dependent manner. Blocking the interactions between ECM and integrins inhibited this differentiation. Conversely, the stimulation of ECM‐integrin interactions by overexpressing collagen‐binding integrin subunits induced differentiation of mES cells cultured on type I collagen. The results of the study indicated that inactivation of the integrin signaling is crucial in promoting mouse embryonic stem cell self‐renewal.

Treatment with siRNA and antisense oligonucleotides targeted to HIF-1α induced apoptosis in human tongue squamous cell carcinomas

Overexpression of hypoxia inducible factor‐1α (HIF‐1α) in cancers has been correlated to a more aggressive tumor phenotype. We investigated the effect of HIF‐1α knockout on the in vitro survival and death of human tongue squamous cell carcinomas (SCC‐4 and SCC‐9). Under normoxic condition, a basal level of HIF‐1α protein was constitutively expressed in SCC‐9 cells, albeit an undetectable level of HIF‐1α messages. Exposure to hypoxia induced only a transient increase in mRNA transcript but a prolonged elevation of HIF‐1α protein and its immediate downstream target gene product, VEGF. Under normoxic or hypoxic conditions, treatment of SCC‐9 cells with AS‐HIF‐1α ODN suppressed both constitutive and hypoxia‐induced HIF‐1α expression at both mRNA and protein levels. Knockout of HIF‐1α gene expression via either AS‐HIF‐1α ODN or siRNA (siRNAHIF‐1α) treatment resulted in inhibition of cell proliferation and induced apoptosis in SCC‐4 and SCC‐9 cells. We also demonstrated that exposure of SCC‐9 cells to hypoxia led to a time‐dependent increase in the expression of bcl‐2 and IAP‐2, but not p53. The attenuated levels of bcl‐2 and IAP‐2, and the enhanced activity of caspase‐3 after treatment with AS‐HIF‐1α ODN may contribute partly to the effects of HIF‐1α blockade on SCC‐9 cell death. Collectively, our data suggest that a constitutive or hypoxia‐induced expression of HIF‐1α in SCC‐9 and SCC‐4 cells is sufficient to confer target genes expression essential for tumor proliferation and survival. As a result, interfering with HIF‐1α pathways by antisense or siRNA strategy may provide a therapeutic target for human tongue squamous cell carcinomas.

Growth inhibition by keratinocyte growth factor receptor of human salivary adenocarcinoma cells through induction of differentiation and apoptosis

We have reported that normal human salivary gland-derived epithelial cells exclusively express keratinocyte growth factor receptor (KGFR). In the process of malignant transformation of human salivary gland tumors, KGFR gene expression disappeared concomitantly with the de novo expression of the fibroblast growth factor receptor 1 (FGFR1) and FGFR4 genes. In the present study, we introduced wild-type KGFR cDNA or chimeric KGFR/FGFR1 cDNA, which encoded the extracellular domain of KGFR and the intracellular domain of FGFR1, into the HSY human salivary adenocarcinoma cell line. The KGFR tyrosine kinase suppressed the activity of FGF receptor substrate 2 (FRS2) and inhibited the growth of HSY by inducing differentiation and apoptosis in vitro and in vivo. Our results provided significant insight into the mechanism of KGFR tumor suppression and suggest that KGFR gene therapy might be a viable method of inhibiting human salivary adenocarcinoma growth.

LEUKEMIA INHIBITORY FACTOR AS AN ANTI-APOPTOTIC MITOGEN FOR PLURIPOTENT MOUSE EMBRYONIC STEM CELLS IN A SERUM-FREE MEDIUM WITHOUT FEEDER CELLS

SummaryWe have developed a serum-free medium, designated ESF7, in which leukemia inhibitory factor (LIF) clearly stimulated murine embryonic stem (ES) cell proliferation accompanied by increased expression of nanog and Rex-1 and decreased FGF-5 expression. These effects were dependent on the concentration of LIF. The ES cells maintained in ESF7 medium for more than 2 yr retained an undifferentiated phenotype, as manifested by the expression of the transcription factor Oct-3/4, the stem cell marker SSEA-1, and alkaline phosphatase. Withdrawal of LIF from ESF7 medium resulted in ES cell apoptosis. Addition of serum to ESF7 medium promoted ES cell differentiation. Addition of MBP4 promoted ES cell differentiation into simple epithelial-like cells. In contrast, FGF-2 promoted ES cell differentiation into neuronal and glial-like cells. Under serum-free culture conditions, LIF was sufficient to stimulate cell proliferation, it inhibited cell differentiation, and it maintained self-renewal of ES cells. Because this simple serum-free adherent monoculture system supports the long-term propagation of pluripotent ES cells in vitro, it will allow the elucidation of ES cell responses to growth factors under defined conditions.

Immunohistochemical study of overexpression of fibroblast growth factor-1 (FGF-1), FGF-2, and FGF receptor-1 in human malignant salivary gland tumours.

Fibroblast growth factor‐1 (FGF‐1) and FGF‐2 are broad spectrum mitogens. The expression of FGF‐1, FGF‐2, and their receptor, FGF receptor‐1 (FGFR‐1), was examined in malignant salivary gland tumours and normal salivary glands, using immunohistochemical methods. In seven cases of adenoid cystic carcinoma (ACC), both duct‐like cells and modified myoepithelial cells were apparently immunopositive for FGF‐1, FGF‐2, and FGFR‐1. In five cases of mucoepidermoid carcinoma (MC), all three types of tumour cells including epidermoid cells, mucous cells, and intermediate cells expressed immunoreactive FGF‐1, FGF‐2, and FGFR‐1. In these malignant salivary gland tumours, increased expression of FGFR‐1 correlated with the intensity of both FGF‐1 and FGF‐2 immunoreactivity. In contrast to malignant salivary gland tumours, eight cases of normal salivary gland showed negative immunostaining for FGF‐1, FGF‐2, and FGFR‐1 while four cases were weakly immunoreactive for FGF and its receptor. These results demonstrate that malignant salivary gland tumours overexpress FGF‐1, FGF‐2, and FGFR‐1 compared with normal salivary glands and suggest that these growth factors may play an important role in facilitating neoplastic progression in human salivary glands.

Bifunctional effects of transforming growth factor-β (TGF-β) on endothelial cell growth correlate with phenotypes of TGF-β binding sites

Abstract Transforming growth factor-β (TGF-β) is a bifunctional, dose-dependent regulator of endothelial cell proliferation induced in vitro by heparin-binding growth factor 1 (HBGF-1, acidic FGF). Here we have examined the relationship between endothelial cell growth and the expression of cell surface binding sites for TGF-β and HBGF-1. Fetal bovine heart endothelial cell (FBHEC) growth was stimulated by low concentrations of TGF-β and inhibited by high concentrations of TGF-β while expressing two distinct classes of TGF-β binding sites with binding constants of 24 p M (6300 sites/cell) and 900 p M (12,000 sites/cell). In contrast, human umbilical vein endothelial cells (HUVEC), whose growth was slightly promoted by TGF-β, exhibited a single class of high-affinity TGF-β binding sites ( K d = 45 p M , 4500 sites/cell). Affinity crosslinking using [ 125 I]TGF-β showed that FBHEC expressed two distinct low molecular weight TGF-β binding sites ( M r 85,000 and 58,000), while HUVEC expressed a single type of low molecular weight TGF-β binding site ( M r 85,000). As detected by binding of [ 125 I]HBGF-1, preincubation of FBHEC with high concentrations of TGF-β transmodulated the expression of high-affinity HBGF-1 receptors. In contrast, no transmodulation of HBGF-1 receptors occurred in FBHEC during preincubation with low concentrations of TGF-β. Furthermore, preincubation of HUVEC with TGF-β did not transmodulate the expression of HBGF-1 receptors. The data suggest that the ability of TGF-β to stimulate or inhibit endothelial cell proliferation in a dose-dependent manner correlated with the expression of specific TGF-β binding site subtypes and involved the transmodulation of HBGF-1 receptors.

Constitutive activating mutation of the FGFR3b in oral squamous cell carcinomas

A G to T mutation at nucleotide position 2128 in the human FGFR3b coding region resulting in a Cys for Gly substitution (G697C) in the tyrosine kinase domain was observed in 62% (44/71) of oral squamous cell carcinomas (OSCC) examined. Immunostained FGFR3b was found in the cytoplasm of prickle cells in normal epithelia, and FGFR3b was localized in the cytoplasm and nucleus in non‐FGFR3b mutant OSCC. Overexpressed FGFR3b protein on plasma membranes was noted in OSCC bearing the FGFR3b mutation. Enhanced tyrosine kinase activity of G697CFGFR3b was confirmed. Our results indicate that G697C is an activating mutation causing constitutive ligand‐independent FGFR3b signaling. This mutation may be involved in the progression of OSCC and thus the FGFR3b coding sequence may have diagnostic or prognostic value for OSCC.

The Role of SGK and CFTR in Acute Adaptation to Seawater in Fundulus Heteroclitus

Killifish are euryhaline teleosts that adapt to increased salinity by up regulating CFTR mediated Cl- secretion in the gill and opercular membrane. Although many studies have examined the mechanisms responsible for long term (days) adaptation to increased salinity, little is known about the mechanisms responsible for acute (hours) adaptation. Thus, studies were conducted to test the hypotheses that the acute homeostatic regulation of NaCl balance in killifish involves a translocation of CFTR to the plasma membrane and that this effect is mediated by serum-and glucocorticoid-inducible kinase (SGK1). Cell surface biotinyation and Ussing chamber studies revealed that freshwater to seawater transfer rapidly (1 hour) increased CFTR Cl- secretion and the abundance of CFTR in the plasma membrane of opercular membranes. Q-RT-PCR and Western blot studies demonstrated that the increase in plasma membrane CFTR was preceded by an increase in SGK1 mRNA and protein levels. Seawater rapidly (1 hr) increases cortisol and plasma tonicity, potent stimuli of SGK1 expression, yet RU486, a glucocorticoid receptor antagonist, did not block the increase in SGK1 expression. Thus, in killifish SGK1 does not appear to be regulated by the glucocorticoid receptor. Since SGK1 has been shown to increase the plasma membrane abundance of CFTR in Xenopus oocytes, these observations suggest that acute adaptation (hours) to increased salinity in killifish involves translocation of CFTR from an intracellular pool to the plasma membrane, and that this effect may be mediated by SGK1.

PLURIPOTENT DIFFERENTIATION IN VITRO OF MURINE ES-D3 EMBRYONIC STEM CELLS

SummaryAlthough the ES-D3 murine embryonic stem cell line was one of the first derived, little information exists on the in vitro differentiation potential of these cells. We have used immunocytochemical and flow cytometric methods to monitor ES-D3 embryoid body differentiation in vitro during a 21-d period. Spontaneous differentiation of embryoid body cells was induced by leukemia inhibitory factor withdrawal in the absence of feeder cells. The pluripotent stem cell markers Oct-3/4, SSEA-1, and EMA-1 were found to persist for at least 7 d, whereas the primitive endoderm marker cytokeratin endo-A was expressed at increasing levels from day 6. The localization of these antigens within the embryoid bodies suggested that embryonic ectoderm- and primitive endoderm-derived tissues were segregated. Localized expression of class III beta-tubulin and sarcomeric myosin also was detected, indicating that representatives of all three embryonic germ layers were present after induction of differentiation in vitro.