Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transcription factor E2F is regulated during the cell cycle through interactions with the product of the retinoblastoma susceptibility gene and related proteins. It is thought that E2F-mediated gene regulation at the G1/S boundary and during S phase may be one of the rate-limiting steps in cell proliferation. It was reported that in vivo overexpression of E2F-1 in fibroblasts induces S phase entry and leads to apoptosis. This observation suggests that E2F plays a role in both cell cycle regulation and apoptosis. To further understand the role of E2F in cell cycle progression, cell death, and tumor development, we have blocked endogenous E2F activity in HBL-100 cells, derived from nonmalignant human breast epithelium, using dominant-negative mutants under the control of a tetracycline-dependent expression system. We have shown here that induction of dominant-negative mutants led to strong downregulation of transiently transfected E2F-dependent chloramphenicol acetyl transferase reporter constructs and of endogenous c-myc, which has been described as a target gene of the transcription factor E2F/DP. In addition, we have shown that blocking of E2F could efficiently protect from apoptosis induced by serum starvation within a period of 10 d, whereas control cells started to die after 24 h. Surprisingly, blocking of E2F did not alter the rate of proliferation or of DNA synthesis of these cells; this finding indicates that cell-cycle progression could be driven in an E2F-independent manner. In addition, we have been able to show that blocking of endogenous E2F in HBL-100 cells led to rapid induction of tumor growth in severe combined immunodeficiency mice. No tumor growth could be observed in mice that received mock-transfected clones or tetracycline to block expression of the E2F mutant constructs in vivo. Thus, it appears that E2F has a potential tumor-suppressive function under certain circumstances. Furthermore, we provide evidence that dysregulation of apoptosis may be an important step in tumorigenesis.
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PMID:Blocking the transcription factor E2F/DP by dominant-negative mutants in a normal breast epithelial cell line efficiently inhibits apoptosis and induces tumor growth in SCID mice. 864 62

In normal (NMEC), transformed (HBL-100) and malignant human mammary epithelial cells (MCF 7, BT-20, MDA-MB 231), we have examined the expression and the regulation by serum of FGF1 and FGF2 mRNA. FGF2 mRNA level was higher in NMEC and in a HBL-100 than in malignant cell lines (MDA-MB-231, BT-20). No FGF2 mRNA was detected in the malignant cell line, MCF-7. In contrast, the FGF1 mRNA was detected in all the mammary epithelial cells but at different levels. NMEC, HBL-100 and MDA-MB231 cells expressed similar level of FGF1 and higher than that observed in BT-20 and MCF-7. In contrast to FGF2 which is only expressed in nonmalignant cells, no correlation between FGF1 mRNA expression and the phenotype of the cells was observed. We followed the expression of four FGF1 mRNA, heterogenous in their 5' untranslated regions. This study demonstrated that (i) the FGF1 mRNA 1.A was not expressed by mammary epithelial cells, (ii) the FGF1 mRNA 1.B was only expressed in normal mammary epithelial cells and (iii) the transcripts 1.C and 1.D were expressed in normal and malignant cells with specific patterns. The expression of FGF1 mRNAs responded in a cell specific manner to serum starvation. The mRNA 1.A was only expressed in normal cells cultured in the absence of serum while 1.C was either up- or down-regulated by serum in transformed cells and the expression of 1.D was greater in presence of serum in all cell lines. These results show that the regulation of FGF1 mRNAs expression is cell specific and does not correlate with a tumorigenic or transformed cell phenotype.
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PMID:Expression and regulation by serum of multiple FGF1 mRNA in normal transformed, and malignant human mammary epithelial cells. 864 41

Hepatocyte growth factor (HGF) is a potent mitogen for a variety of cell types, but it is also known as an antimitogenic factor for several types of tumor cell lines. The biological processes by which HGF inhibits tumor cell growth remain poorly understood. Here we report a comparative study of HGF-mediated signal transduction events between two opposite responding types of human hepatoblastoma cell lines, HuH6 and HepG2. Following serum starvation, both cell lines were cultured in hepatocyte growth medium (HGM), a chemically defined medium, in the presence or absence of HGF. Under these culture conditions, cell growth in HuH6 was promoted by HGF, while it was inhibited in HepG2. Phosphorylation of p42/mitogen-activated protein (MAP) kinase was observed within 10 min after HGF stimulation in both cell lines. The level of phosphorylated MAP kinase in HuH6 declined to basal levels after 2 hr. However, in HepG2 the phosphorylated form was detectable at 6 hr. p21/waf1 was induced in both cell lines where levels peaked 4-6 hr after HGF stimulation. In HuH6, a marked decrease of p21/waf1 was observed at 8-12 hr, while a high level of p21/waf1 was sustained for at least 24 hr in HepG2. HGF treatment depressed cdk2 activity in a time-dependent manner in HepG2 while the activity increased in HuH6. When serum-starved HepG2 was growth stimulated with serum in the presence or absence of HGF, the cells treated with HGF underwent growth inhibition correlating with a sustained induction of p21/waf1 and a decrease of cdk2 activity. Immunoprecipitation analysis revealed accumulation of cdk2-associated p21/waf1 in the HGF-treated HepG2. Together, the results suggest that sustained induction of p21/waf1 mediates growth inhibition in HepG2 in the presence of HGF.
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PMID:Possible involvement of p21/waf1 in the growth inhibition of HepG2 cells induced by hepatocyte growth factor. 973 53

The transport of D-glucose into rainbow trout (Oncorhynchus mykiss) and river lamprey (Lampetra fluviatilis) hepatocytes, as well as into rainbow trout hepatoblastoma cell line RTH-149 was studied using tracer methods. The half-time for D-glucose equilibration was 15 s for rainbow trout. The half-times for the non-metabolizable D-glucose analog, 3-O-methyl-D-glucose equilibration were 8 s, 37 s and 38 s for rainbow trout, lamprey and RTH-149 cells, respectively. The 3-O-methyl-D-glucose was taken up by rainbow trout hepatocytes by facilitated diffusion in addition to simple diffusion. The uptake showed saturation kinetics with the K(m) of 37 mM and V(max) of 62 mmol kg(-1) cells min(-1). The uptake was sensitive to phloretin and cytochalasin B, but not affected by ouabain. The 3-O-methyl-D-glucose uptake by lamprey hepatocytes and RTH-149 cells showed no indication of saturation up to 160 mM, and was not affected by phloretin, cytochalasin B or ouabain, which suggests the mode of transport to be by passive diffusion. However, immunocytochemical stainings revealed the existence of mammalian type GLUT1 and GLUT2 transporters in all cells studied. The lack of a functioning carrier-mediated glucose uptake in lamprey hepatocytes might be due to its physiological state (prespawning starvation). The minor 3-O-methyl-D-glucose uptake into RTH-149 cells compared to freshly isolated rainbow trout hepatocytes might reflect low metabolic activity of the cell lines. Under the conditions applied the RTH-149 cell line is no suitable in vitro model for glucose transport in fish cells.
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PMID:D-Glucose uptake in fish hepatocytes: mediated by transporter in rainbow trout (Oncorhynchus mykiss), but only by diffusion in prespawning lamprey (Lampetra fluviatilis) and in RTH-149 cell line. 1461 5

Hepatocyte growth factor/scatter factor (HGF) is a ubiquitously expressed molecule that elicits pleiotropic functions on epithelial cells, including mitogenic, motogenic, differentiating, angiogenic and morphogenic effects. In hepatoblastoma (HB), post-operative residual tumor growth and tumor recurrences are often associated with markedly elevated serum levels of HGF, suggesting a link between this molecule and tumor malignancy. Here, we demonstrate that HGF has no impact on overall cell viability and proliferation of HB cells, although signal transduction occurs downstream of HGF, such as c-Met phosphorylation, activation of phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK)/ERK-1/2 signaling. Instead of being mitogenic, HGF confers anti-apoptotic properties upon serum starvation and moreover protects HB cells against strong apoptotic inducers such as cisplatin and camptothecin, thereby contributing to chemotherapeutic resistance. This effect is mainly dependent on the PI3K/AKT signaling pathway, since inhibition by wortmannin resulted in abrogation of HGF-mediated survival, whereas inhibition of the MAPK pathway had no effect. Together, these findings highlight the importance of HGF in tumor cell survival and suggest that HGF and its cognate receptor c-Met should be considered as a candidate for combined therapeutic strategies of advanced pediatric liver tumors.
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PMID:Hepatocyte growth factor protects hepatoblastoma cells from chemotherapy-induced apoptosis by AKT activation. 2037 1

Hepatoblastoma (HB) is a rare cancer but represents the most common liver malignancy in children under 3 years of age. Nevertheless, a clear understanding of the pathogenesis is lacking. Although the treatment of HB has been dramatically improved by combining chemotherapy regimens with surgery, its fatal outcome of fast development and recurrence makes new treatment strategies for HB, based on an improved understanding of the pathogenesis, essential. Autophagy is believed to be important in the progression of cancers. However, the role of autophagy in HB remains to be elucidated. Here, we show that autophagy is activated in HB tissues and cells under the conditions of starvation or chemotherapy, coupled with the over-expression of autophagic-related genes BECN1 and ATG5. Suppression of autophagy with pharmacological agents and small interfering RNAs significantly increased cell apoptosis and retarded proliferation in response to nutrition deprivation and treatment with chemotherapeutics. Our data demonstrate that the BECN1 and ATG5-dependent phosphoinositide 3-kinase (PI3K) signaling pathway is essential for the survival of HB cells and their tolerance to chemotherapy and starvation-induced death, and suggests that modifying such autophagic genes may suppress the development of HB, thus offering a therapeutic potential for patients with HB.
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PMID:Inhibition of autophagy may suppress the development of hepatoblastoma. 2197 44

NS5ATP9, a gene up-regulated by NS5A, plays a crucial oncogenic role in several types of human tumours. However, the underlying mechanisms remain unclear. Autophagy, an evolutionarily conserved catabolic process, maintains cellular homeostasis under stress conditions, such as starvation, and plays a crucial role in tumour initiation and progression. Here, we report that NS5ATP9 mRNA and protein expression was up-regulated in starved HepG2 cells and that the up-regulated NS5ATP9 played a functional role in starvation-induced autophagy. Overexpression or silencing of this gene showed contrasting effects on Beclin 1 and on starvation-induced autophagy. Furthermore, NS5ATP9-mediated autophagy is required for promotion of tumour cell growth, and this effect could be inhibited with 3-methyladenine, chloroquine or by Beclin 1-silencing. Thus, the mechanism for NS5ATP9-promoted autophagy is Beclin 1-dependent in the condition of starvation, and for hepatoblastoma cell growth is also Beclin 1-dependent.
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PMID:NS5ATP9 Promotes Beclin 1-Dependent Starvation-Induced Autophagy of Hepatoblastoma Cells. 2564 30