Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The E2F family of transcription factors controls the expression of genes that are involved in cell cycle regulation. E2F DNA-binding activity is found in complex with the retinoblastoma protein, pRb, and with the pRb-related p107 and p130. To date, cDNAs for three members of the E2F gene family have been isolated. However, all three E2Fs associate in vivo exclusively with pRb. We report here the cloning and functional analysis of a fourth E2F family member. E2F-4 encodes a 413-amino-acid protein with significant homology to E2F-1. E2F-4 antibodies recognize a 60-kD protein in anti-p107 immunoprecipitates, indicating that E2F-4 associates with p107 in vivo. Like the other E2Fs, E2F-4 requires DP-1 for efficient DNA binding and transcriptional activation of E2F site-containing promoters. Increased expression of E2F-4 and DP-1 in SaoS-2 osteosarcoma cells causes a shift from G1-phase cells to S and G2/M-phase cells, suggesting a role for E2F-4 in regulation of cell-cycle progression. We show that expression of E2F-4 and DP-1 together with an activated ras oncogene in rat embryo fibroblasts, causes transformation, indicating that E2F-4 has oncogenic activity.
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PMID:E2F-4, a new member of the E2F gene family, has oncogenic activity and associates with p107 in vivo. 795 25

The retinoblastoma tumor suppressor gene product (pRb) is involved in controlling cell cycle progression from G1 into S. pRb functions, in part, by regulating the activities of several transcription factors, making pRb involved in the transcriptional control of cellular genes. Transient-transfection assays have implicated pRb in the transcription of several genes, including c-fos, the interleukin-6 gene, c-myc, cdc-2, c-neu, and the transforming growth factor beta2 gene. However, these assays place the promoter in an artificial context and exclude the effects of far 5' upstream regions and chromosomal architecture on gene transcription. In these experiments, we have studied the role of pRb in the control of cell cycle-related genes within a chromosomal context and within the context of the G1 phase of the cell cycle. We have used adenovirus vectors to overexpress pRb in human osteosarcoma cells and breast cells synchronized in early G1. By RNase protection assays, we have assayed the effects of this virus-produced pRb on gene expression in these cells. These results indicate that pRb is involved in the transcriptional downregulation of the E2F-1, E2F-2, dihydrofolate reductase, thymidine kinase, c-myc, proliferating-cell nuclear antigen, p107, and p21/Cip1 genes. However, it has no effect on the transcription of the E2F-3, E2F-4, E2F-5, DP-1, DP-2, or p16/Ink4 genes. The results are consistent with the notion that pRb controls the transcription of genes involved in S-phase promotion. They also suggest that pRb negatively regulates the transcription of two of the transcription factors whose activity it also represses, E2F-1 and E2F-2, and that it plays a role in downregulating the immediate-early gene response to serum stimulation.
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PMID:Regulation of cellular genes in a chromosomal context by the retinoblastoma tumor suppressor protein. 967 66

We previously demonstrated that P16Ink4a (p16) expression in p16-deficient U343 astrocytoma cells causes a G1 cell cycle arrest, profound changes in cytoskeletal proteins and alterations in expression and activity of the pRB and E2F family proteins. We examine here the effects of expressing wild type or mutant versions of the downstream targets of p16 in U343 astrocytomas. We first attempted to block proliferation of U343 cells using the dominant mutant of pRB, deltap34. Expression of this mutant in the human osteosarcoma, SAOS-2, potently blocked proliferation but did not affect the cell cycle of U343 cells. We next showed that expression of E2F-1, E2F-2, E2F-3 and E2F-4 are each able to overcome this p16-dependent cell cycle arrest but exhibit distinct biological activities. Adenoviral-mediated expression of E2F-1, E2F-2, E2F-3, or E2F-4 overcame the p16-dependent cell cycle block and induced alterations in cell morphology. E2F-5, only in conjunction with DP1, promoted cell cycle progression. For both E2F-1 and E2F-2, but not E2F-3 or E2F-5/DP1, cell cycle re-entry was associated with almost quantitative cell death. Only small numbers of dying cells were observed in E2F-4-expressing cultures. Expression of the different E2F's altered the expression of distinct sets of cell cycle regulatory proteins. E2F-1 induced endogenous E2F-4 expression and also caused an increase in pRB, p107 and cyclin E levels. Expression of E2F-4 caused a weak increase in E2F-1 levels but also strongly induced pRB, p107, p130 and cyclin E. However, E2F-1 and E2F-4 clearly regulate expression of distinct genes, demonstrated when E2F-4 caused a threefold increase in the levels of cdk2 whereas E2F-1 failed to increase in this cyclin dependent kinase. Similarly, expression of E2F-1 or E2F-2 were shown to have distinct effects on the expression of cdk2, cyclin E and pRB despite both of these closely related E2F-family members potently inducing cell death. Thus, E2F-1, E2F-2, E2F-3 and E2F-4 are able to overcome the p16-dependent proliferative block in U343 astrocytoma cells. While overcoming this cell cycle block, each of the E2F's uniquely affect the expression of a number of cell cycle regulatory proteins and have distinct abilities to promote cell death.
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PMID:The E2F-family proteins induce distinct cell cycle regulatory factors in p16-arrested, U343 astrocytoma cells. 978 3

The Epstein-Barr Virus (EBV) immediate-early protein BRLF1 is one of two transactivators which mediate the switch from latent to lytic replication in EBV-infected cells. DNA viruses often modulate the function of critical cell cycle proteins to maximize the efficiency of virus replication. Here we have examined the effect of BRLF1 on cell cycle progression. A replication-deficient adenovirus expressing BRLF1 (AdBRLF1) was used to infect normal human fibroblasts and various epithelial cell lines. BRLF1 expression induced S phase entry in contact-inhibited fibroblasts and in the human osteosarcoma cell line U-2 OS. AdBRLF1 infection produced a dramatic increase in the level of E2F1 but not E2F4. In contrast, the levels of Rb, p107, and p130 were decreased in AdBRLF1-infected cells. Electrophoretic mobility shift assays confirmed an increased level of free E2F1 in the AdBRLF1-infected human fibroblasts. Consistent with the previously described effect of E2F1, AdBRLF1-infected fibroblasts had increased levels of p53 and p21 and died by apoptosis. BRLF1-induced activation of E2F1 may be required for efficient EBV lytic replication, since at least one critical viral replication gene (the viral DNA polymerase) is activated by E2F (C. Liu, N. D. Sista, and J. S. Pagano, J. Virol. 70:2545-2555, 1996).
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PMID:The Epstein-Barr virus protein BRLF1 activates S phase entry through E2F1 induction. 1040 Jul 50

The retinoblastoma family proteins pRB, p107, and p130 are phosphorylated and released from E2Fs in the late G(1) phase of the cell cycle. This phosphorylation is thought to contribute to the derepression of E2F-responsive genes and to be mediated, in part, by Cdk4 and Cdk6. Evidence that Cdk4/6 activity is inhibited by p16(INK4A) in most pRB(-) cells suggests that p107 and p130 may be underphosphorylated and remain associated with E2Fs during G(1)-S progression in cells that lack pRB. To examine this, we evaluated the cell cycle-dependent phosphorylation and E2F binding abilities of p107 and p130 in pRB(-), p16(+) Saos-2 osteosarcoma cells. p130, but not p107, was phosphorylated and released from E2F-4 in late G(1) and S phase cells, although p130 phosphorylation differed qualitatively in these and other pRB(-), p16(+) cells as compared with pRB(+), p16(-) cell types. p130 phosphorylation occurred in the absence of cyclin D-Cdk4/6 complexes, coincided with cyclin E- and Cdk2-associated kinase activity, and was prevented by expression of dominant negative Cdk2. Moreover, dominant negative Cdk2 prevented the dissociation of endogenous p130-E2F-4 complexes and inhibited E2F-4-dependent transcription. These findings show that p130 can be phosphorylated and functionally inactivated in a Cdk2-dependent process, and they highlight the involvement of distinct Cdks in the regulation of different pRB family proteins.
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PMID:Cdk2-dependent phosphorylation and functional inactivation of the pRB-related p130 protein in pRB(-), p16INK4A(+) tumor cells. 1090 46

Since osteogenic sarcoma (OGS) predominantly affects children, its etiology and progression may be determined more by genetic than environmental factors. A few genes have been associated with OGS, however, their value in the diagnosis and/or prognosis of the disease remains poor. Evidently, more markers need to be identified for improving management of patients with OGS. To identify potential genetic markers for OGS, we have extended preferential amplification of coding sequences (PACS) to screen multiple samples simultaneously. The extended method is termed multi-PACS. Multi-PACS was applied between a normal osteoblast and four OGS-derived cell lines to identify differentially expressed coding sequence tags (dCST) that identified 145 dCSTs. Subsequently, differential mRNA expression was validated for a chosen subset of 22 dCSTs. These chosen dCSTs include among others cyclins D and E, two cyclin dependent kinases, two other kinases, transcription factors E2F4, E2F5, and p130, a DNA repair gene, a gene for the signalosome subunit, and potential guanine nucleotide binding factors. We infer that these genes could be so easily identified because PACS preferentially identifies coding instead of non-coding sequences. We also infer that these genes identify signaling pathways pertinent to OGS. mRNA expression profile of these 22 genes/dCSTs generated distinct expression signature of the OGS-derived cell lines suggesting that further work on clinical samples with these dCSTs will yield valuable information for OGS. We conclude that these 22 genes/dCSTs are candidate markers for OGS.
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PMID:Identification of twenty-two candidate markers for human osteogenic sarcoma. 1170 42

Mechanisms underlying multidrug resistance (MDR), one of the major causes of cancer treatment failure, are still poorly understood. We selected the osteosarcoma MDR HosDXR150 cell line by culturing Hos cells in the presence of increasing doxorubicin doses and showed that it is crossresistant to vinblastine. Similarly to the Hos parental cell line, HosDXR150 cells present mutated p53, functionally inactivated pRb/p105 and wild-type pRb2/p130. Owing to p53 mutation, MDR-1 gene, codifying for P-glycoprotein, is upregulated. Evasion of apoptosis in HosDXR150 cells is only partially explained by drug extrusion because of P-glycoprotein overexpression. Analysis of gene expression level profiles showed that parental cell line undergoes apoptosis through an E2F1/p73-dependent pathway while its resistant variant evades it. This result can be explained by the presence of distinct E2Fs-pRb2/p130 complexes on the p73 promoter. Namely, in Hos p73 transcription is activated by E2F1-Rb2/p130-p300 complexes, while in HosDXR150 it is kept repressed by E2F4-Rb2/p130-HDAC1 complexes.
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PMID:Triggering of p73-dependent apoptosis in osteosarcoma is under the control of E2Fs-pRb2/p130 complexes. 1278 60

Previous studies have shown that decreased expression of the reduced folate carrier (RFC) and increased expression of dihydrofolate reductase (DHFR) are associated with intrinsic and acquired methotrexate resistance, respectively, in osteosarcoma (OS). It has also been shown in colorectal cancer that E2F-1 expression correlates with thymidylate synthase (TS) and, to a lesser extent, DHFR expression. To begin to investigate the regulation of DHFR and RFC expression in OS samples, mRNA expression of E2F-1 and E2F-4 were measured in OS tumor samples and related to DHFR, RFC, and TS mRNA expression. Using fluorescent quantitative real-time PCR, 112 human OS patient samples were investigated for potential E2F-1/E2F-4:DHFR, E2F-1/E2F-4:RFC, and E2F-1/E2F-4:TS correlations. The expression ranges for each gene are as follows: DHFR, 0.02-33.13 (median = 0.20); RFC, 0.02-229.13 (median = 1.91); TS, 0.01-9.99 (median = 0.15); E2F-1, 0.05-69.07 (median = 0.52); and E2F-4, 0.24-52.35 (median = 1.45). Spearman correlation coefficients (r(s)) for E2F-1:DHFR, E2F-1:RFC, E2F-1:TS, E2F-4:DHFR, E2F-4:RFC, and E2F-4:TS were calculated to be 0.53, 0.63, 0.60, 0.41, 0.58, and 0.33, respectively (P < 0.001). On the basis of this data, moderate correlations exist between E2F-1/E2F-4 and DHFR, RFC, and TS. These results suggest E2F-1/E2F-4 may play a role in the regulation of RFC expression, which has not been reported previously. The E2F transcription factors are also related to DHFR and TS expression in OS samples, suggesting a possible involvement in methotrexate resistance. Although E2F mRNA levels correlate with DHFR, RFC, and TS mRNA expression, additional experiments are necessary to determine the direct effects of these transcription factors and identify other proteins that may influence this relationship.
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PMID:mRNA expression levels of E2F transcription factors correlate with dihydrofolate reductase, reduced folate carrier, and thymidylate synthase mRNA expression in osteosarcoma. 1281 32

Osteosarcomas (OS) are complex bone tumors with various genomic alterations. These alterations affect the expression and function of several genes due to drastic changes in the underlying gene regulatory network. However, we know little about critical gene regulators and their functional consequences on the pathogenesis of OS. Therefore, we aimed to determine microRNA and transcription factor (TF) co-regulatory networks in OS cell proliferation. Cell proliferation is an essential part in the pathogenesis of OS and deeper understanding of its regulation might help to identify potential therapeutic targets. Based on expression data of OS cell lines divided according to their proliferative activity, we obtained 12 proliferation-related microRNAs and corresponding target genes. Therewith, microRNA and TF co-regulatory networks were generated and analyzed regarding their structure and functional influence. We identified key co-regulators comprising the microRNAs miR-9-5p, miR-138, and miR-214 and the TFs SP1 and MYC in the derived networks. These regulators are implicated in NFKB- and RB1-signaling and focal adhesion processes based on their common or interacting target genes (e.g., CDK6, CTNNB1, E2F4, HES1, ITGA6, NFKB1, NOTCH1, and SIN3A). Thus, we proposed a model of OS cell proliferation which is primarily co-regulated through the interactions of the mentioned microRNA and TF combinations. This study illustrates the benefit of systems biological approaches in the analysis of complex diseases. We integrated experimental data with publicly available information to unravel the coordinated (post)-transcriptional control of microRNAs and TFs to identify potential therapeutic targets in OS. The resulting microRNA and TF co-regulatory networks are publicly available for further exploration to generate or evaluate own hypotheses of the pathogenesis of OS (http://www.complex-systems.uni-muenster.de/co_networks.html).
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PMID:How microRNA and transcription factor co-regulatory networks affect osteosarcoma cell proliferation. 2400 96

We identify the cell cycle-regulated mRNA transcripts genome-wide in the osteosarcoma-derived U2OS cell line. This results in 2140 transcripts mapping to 1871 unique cell cycle-regulated genes that show periodic oscillations across multiple synchronous cell cycles. We identify genomic loci bound by the G2/M transcription factor FOXM1 by chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) and associate these with cell cycle-regulated genes. FOXM1 is bound to cell cycle-regulated genes with peak expression in both S phase and G2/M phases. We show that ChIP-seq genomic loci are responsive to FOXM1 using a real-time luciferase assay in live cells, showing that FOXM1 strongly activates promoters of G2/M phase genes and weakly activates those induced in S phase. Analysis of ChIP-seq data from a panel of cell cycle transcription factors (E2F1, E2F4, E2F6, and GABPA) from the Encyclopedia of DNA Elements and ChIP-seq data for the DREAM complex finds that a set of core cell cycle genes regulated in both U2OS and HeLa cells are bound by multiple cell cycle transcription factors. These data identify the cell cycle-regulated genes in a second cancer-derived cell line and provide a comprehensive picture of the transcriptional regulatory systems controlling periodic gene expression in the human cell division cycle.
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PMID:Identification of cell cycle-regulated genes periodically expressed in U2OS cells and their regulation by FOXM1 and E2F transcription factors. 2410 97


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