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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report here that osteoblasts and osteoblast-like osteosarcoma cells express PMCA1b, an alternatively spliced transcript of plasma membrane Ca(2+)-ATPase. Synthetic oligonucleotide pairs were designed based upon unique regions of the cDNA encoding known PMCA isoforms (PMCA1-3) and used as primers in PCR-mediated amplification of cDNA synthesized from ROS 17/2.8 osteosarcoma cell RNA. A product was observed only when PMCA1-specific primers were present; no products were seen with PMCA2 or PMCA3 primers unless cDNA synthesized from rat brain RNA was present. Examination of the cDNA encoding the C terminus of PMCA1 from ROS 17/2.8 cells revealed that the mRNA is spliced to yield the PMCA1b isoform, a Ca(2+)-ATPase containing a consensus phosphorylation site for cAMP-dependent protein kinase A and a modified calmodulin binding domain. PMCA1b was also detected in UMR-106-01 osteosarcoma cells and unpassaged primary rat calvarial osteoblasts. These results suggest that the regulation of osteoblast function by agents that act via cAMP-mediated pathways may involve alterations in the activity of the plasma membrane Ca(2+)-ATPase.
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PMID:Osteoblasts express the PMCA1b isoform of the plasma membrane Ca(2+)-ATPase. 750 68

Malignantly transformed cells usually display a rosette-like morphology of substratum adhesions (called podosomes) and disorganized microfilaments, and are often associated with elevated production of chondroitin sulphate. We previously showed that many tissues and cells express alternatively spliced multiforms of the large chondroitin sulphate proteoglycan termed PG-M (versican is one of the short transcripts). Since PG-M/versican inhibits many types of cell-substratum adhesion and is found to be excluded from focal contacts of cultured fibroblasts, it is likely that this proteoglycan is generally involved in regulating cell-substratum adhesion. We report here that PG-M/versican is selectively excluded from podosomes of human osteosarcoma cells and that specific inhibition of its biosynthesis by an antisense method suppresses such a malignant cell-adhesive phenotype. The results support the idea that PG-M/versican acts as an anti-adhesive molecule and raise the possibility that PG-M/versican controls one type of cancer cell behaviour.
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PMID:Repression of a malignant cell-substratum adhesion phenotype by inhibiting the production of the anti-adhesive proteoglycan, PG-M/versican. 753 Dec 2

The mts1 gene is one of the genes specifically expressed in mouse metastatic tumors and tumor cell lines. In this paper, we present data on cloning and sequencing of two variants of human mts1 cDNAs (hu-mts1 and hu-mts1 (var)), as well as of the corresponding region in the human genome. Comparison of the genomic sequence with the sequence of the mts1 cDNAs demonstrates presence of two alternatively spliced variants of the mts1 in the human osteosarcoma cell line (OHS). The alternative splicing occurs within the 5'-untranslated region (UTR) of human mts1 pre-mRNA. Both splice variants, hu-mts1 and hu-mts1 (var), retain similar stability in the cells, contain one open reading frame coding for the MTS1 protein and differ only slightly in their translational capacity. The splice variants demonstrate dramatic variations in the level of expression in different human tissues and in human tumor cell lines. Although we have not revealed substantial differences in the mode of action of the two splice variants in the cells, the observed tissue specificity of expression supports the notion that it plays an important role in determining the activity of mts1 in different tissues.
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PMID:Characterization of two splice variants of metastasis-associated human mts1 gene. 760 66

Decorin is a leucine-rich, chondroitin/dermatan sulfate proteoglycan which binds collagen and growth factors. We have recently completed the genomic organization of human decorin and discovered two alternatively spliced leader exons, designated exon Ia and Ib, in the 5'-untranslated region. Initial analysis of the sequences upstream to these two exons showed that promoter Ia contained only two GC boxes while promoter Ib contained a CAAT and two TATA boxes in close proximity to the transcription start site. To determine if these 5'-flanking sequences exhibited promoter activity, chimeric chloramphenicol acetyltransferase expression plasmids containing the promoter region of either exon Ia or Ib were transfected into HeLa and MG-63 osteosarcoma cells. The results showed that only the region flanking exon Ib was functional. In vitro transcription assay generated two transcripts of 92 and 82 base pairs (bp) indicating that both TATA boxes could be used. Using stepwise 5' deletion analysis we found that the minimum promoter region at -140 bp from the transcription start site, which contained only the CAAT and the two TATA boxes, exhibited strong promoter activity. When a larger construct containing an additional 800 bp of upstream region was tested, a significant increase in transcriptional activity was observed. Interestingly, this promoter region contained several putative binding sites for ubiquitous factors (AP1, AP5, and NF-kappa B) and for transforming growth factor-beta and a 150-bp homopurine/homopyrimidine element with several mirror repeats. When contained in a supercoiled plasmid, this sequence exhibited sensitivity to endonuclease S1, an enzyme that preferentially digests single-stranded DNA. Precise S1 mapping, obtained by direct sequencing of nine distinct S1-generated clones, revealed that in all cases the borders of the sensitive sequence resided within the pur/pyr segment. We propose that this region of the promoter could adopt an intramolecular hairpin triplex structure in vivo and may play a role in the chromatin organization at the decorin gene locus. In addition, this region was able to up-regulate a minimal heterologous promoter in transient transfection assays. The results show that the structure of the decorin gene promoter is different from that of any other proteoglycan promoter characterized so far and indicate that the pur/pyr segment plays a role in the regulation of gene transcription.
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PMID:Structural and functional characterization of the human decorin gene promoter. A homopurine-homopyrimidine S1 nuclease-sensitive region is involved in transcriptional control. 827 54

Identical complementary DNAs (cDNAs) that encode a 593-amino acid human PTH (PTH)/PTH-related peptide (PTHrP) receptor were isolated by hybridization techniques from two cDNA libraries which had been constructed from human kidney and human osteoblast-like osteosarcoma cells (SaOS-2). Northern blot analysis of total RNA from human bone- and kidney-derived tissue revealed one single major messenger RNA species of about 2.5 kilobases in both tissues. The human PTH/PTHrP receptor has 91% and 81% identity, respectively, with the previously cloned rat and opossum receptors, indicating a high degree of conservation among mammals. Despite this striking degree of amino-acid conservation, the human PTH/PTHrP receptor has several unique biological properties when transiently expressed in COS-7 cells. The apparent dissociation constants for [Nle8,18,Tyr34] bovine PTH(1-34) amide [bPTH(1-34)] are similar for the human and the rat receptor (approximately 8 vs. approximately 15 nM) whereas [Tyr36]PTHrP(1-36) amide has a slightly lower affinity for the human (15-40 nM) than for the rat receptor (approximately 15 nM). Both ligands stimulate efficiently and with similar efficacy the accumulation of intracellular cAMP. The affinities for the antagonists [Nle8,18,Tyr34] bPTH(3.34) amide [bPTH(3-34)] and in particular for [Nle8,18,Tyr34] bPTH(7-34) amide [bPTH(7-34)] are considerably higher for the human receptor, e.g. approximately 8 nM vs. 30 nM for bPTH(3-34) and approximately 100 nM vs. 5000 nM for bPTH(7-34), respectively. Similar biological findings were previously attributed to differences in species- and/or organ-specific PTH/PTHrP receptors. The expression of the recombinant, highly homologous rat and human receptors in a uniform environment indicate that the moderate differences in the primary receptor structure have profound consequences for the receptor binding affinity of amino-terminally truncated PTH analogs. Furthermore, the molecular cloning of identical cDNAs encoding a human PTH/PTHrP receptor from the two major target organs for PTH, bone and kidney, provides strong evidence for one single PTH/PTHrP receptor in both organs, although additional and/or alternatively spliced receptors cannot be excluded.
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PMID:Identical complementary deoxyribonucleic acids encode a human renal and bone parathyroid hormone (PTH)/PTH-related peptide receptor. 838 12

Two forms of the transmembrane human protein tyrosine phosphatase (PTP sigma), generated by alternative splicing, were identified by cDNA cloning and Northern hybridization with selective cDNA probes. The larger form of PTP sigma is expressed in various human tissues, human osteosarcoma, and rat tibia. The hPTP sigma cDNA codes for a protein of 1911 amino acid residues and is composed of a cytoplasmic region with two PTP domains and an extracellular region that can be organized into three tandem repeats of immunoglobulin-like domains and eight tandem repeats of fibronectin type III-like domains. In the brain, the major transcript of PTP sigma is an alternatively spliced mRNA, in which the coding region for the fibronectin type III-like domains number four to seven are spliced out, thus coding for a protein of 1502 amino acid residues similar to the rat PTP sigma and rat PTP-NE3. Using in situ hybridization, we assigned hPTP sigma to chromosome 6, arm 6q and band 6q15. The bacterial-expressed hPTP sigma exhibits PTPase activity that was inhibited by orthovanadate (IC50 = 0.02 microM) and by two bisphosphonates used for the treatment of bone diseases, alendronate (ALN) (IC50 = 0.5 microM) and etidronate (IC50 = 0.2 microM). In quiescent calvaria osteoblasts, micromolar concentrations of vanadate, ALN and etidronate stimulate cellular proliferation. These findings show tissue-specific alternative splicing of PTP sigma and suggest that PTPs are putative targets of bisphosphonate action.
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PMID:Human protein tyrosine phosphatase-sigma: alternative splicing and inhibition by bisphosphonates. 899 85

This study examines the cooperative effects of a human estrogen receptor-alpha (ERalpha) isoform on estrogen (E2)-mediated gene activation in U2-OS osteosarcoma cells. Delta5ERalpha, an alternatively spliced ERalpha variant lacking exon 5, is coexpressed with normal ERalpha in several E2-responsive neoplastic tissues. However, the potential interactions of delta5ERalpha with normal ERalpha have not been functionally characterized. Delta5ERalpha encodes the hormone-independent trans-activating function (AF-1), as well as the constitutive receptor dimerization and DNA-binding domains. It is generated by an alternate splice event that omits exon 5 and alters the reading frame of the resulting mRNA. The delta5ERalpha protein is prematurely truncated and lacks the majority of the hormone-binding and activating function-2 (AF-2) domains. When delta5ERalpha mammalian expression vector was transfected alone in human ERalpha/ERbeta-negative osteosarcoma U2-OS cells, it had no effect on either basal or E2-mediated EREtk81Luc reporter transcriptional activity, while transfected cells expressing control normal ERalpha increased EREtk81 Luc activity up to 20-fold in response to 10 nM E2. However, when delta5ERalpha was cotransfected with normal ERalpha, both basal and E2-stimulated EREtk81Luc reporter activation were increased approximately 500% over levels observed when cells were transfected with ERalpha alone. Similar effects of delta5ERalpha and normal ERa coexpression were observed using an E2-responsive human C3 promoter/luciferase reporter construct. The effects of delta5ERalpha on normal ERalpha were further assessed in U2-OS cells stably transfected with normal ERalpha. Transfection of increasing amounts of delta5ERalpha expression vector into [ERalpha+]OS cells resulted in potentiation of E2-stimulated ERELuc activity in a synergistic, dose-dependent manner. Moreover, coexpression of delta5ERalpha in [ERalpha+]OS cells improved E2 sensitivity 100-fold over cells expressing ERalpha alone. Proliferation rates of stable U2-OS cell lines expressing delta5ERalpha were significantly increased (P < 0.05), with cell doubling times reduced from 35 h in control parental U2-OS cells to 28 h in [delta5ERalpha]OS cells. However, growth rates were not affected by either E2 or tamoxifen treatment. Electromobility shift/supershift assays using nuclear extracts of U2-OS cells stably transfected with ERalpha and delta5ERalpha confirmed the constitutive binding of delta5ERalpha and ERalpha protein to estrogen-response element (ERE) sequence independent of E2 and also showed an increase in delta5ERalpha/ERalpha-ERE complexes with E2 treatment. These data are consistent with interactive effects of normal ERalpha and delta5ERalpha on transcription from classic ERE gene promoters. Delta5ERalpha appears to therefore act as a dominant positive receptor that increases both basal and E2-stimulated gene transactivation of normal ERalpha.
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PMID:A tumor-specific truncated estrogen receptor splice variant enhances estrogen-stimulated gene expression. 973 4

The beneficial influence of E2 in the maintenance of healthy bone is well recognized. However, the way in which the actions of this hormone are mediated is less clearly understood. Western blot analysis of ERalpha in osteoblasts clearly demonstrated that the well characterized 66-kDa ERalpha was only one of the ERalpha isoforms present. Here we describe a 46-kDa isoform of ERalpha, expressed at a level similar to the 66-kDa isoform, that is also present in human primary osteoblasts. This shorter isoform is generated by alternative splicing of an ERalpha gene product, which results in exon 1 being skipped with a start codon in exon 2 used to initiate translation of the protein. Consequently, the transactivation domain AF-1 of this ERalpha isoform is absent. Functional analysis revealed that human (h)ERalpha46 is able to heterodimerize with the full-length ERalpha and also with ERbeta. Further, a DNA-binding complex that corresponds to hERalpha46 is detectable in human osteoblasts. We have shown that hERalpha46 is a strong inhibitor of hERalpha66 when they are coexpressed in the human osteosarcoma cell line SaOs. As a functional consequence, proliferation of the transfected cells is inhibited when increasing amounts of hERalpha46 are cotransfected with hERalpha66. In addition to human bone, the expression of the alternatively spliced ERalpha mRNA variant is also detectable in bone of ERalpha knockout mice. These data suggest that, in osteoblasts, E2 can act in part through an ERalpha isoform that is markedly different from the 66-kDa receptor. The expression of two ERalpha protein isoforms may account, in part, for the differential action that estrogens and estrogen analogs have in different tissues. In particular, the current models of the action of estrogens should be reevaluated to take account of the presence of at least two ERalpha protein isoforms in bone and perhaps in other tissues.
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PMID:ERalpha gene expression in human primary osteoblasts: evidence for the expression of two receptor proteins. 1173 9

We have previously reported the alternatively spliced transcripts of fibroblast growth factor 3 (FGFR3 ATs and MTs) derived by aberrant splicing and usage of cryptic splicing sites. Here, we describe a soluble variant of FGFR3 (FGFR3 AT-III) arising from skipping exons 8, 9, and 10 in human SaOS-2 osteosarcoma cell. This splicing event leads to the generation of an mRNA encoding a FGFR3 in which the COOH-terminal portion of the Ig-like-III domain and transmembrane domain are deleted while the remainder of the mature molecule is fused in-frame to the COOH-terminal cytoplasmic kinases domains. Sf9 cells transfected with the corresponding cDNA express the soluble form of FGFR3 AT-III into the condition medium and its secreted form was able to bind both FGF-1 and FGF-2 leading to loss of ligand binding specificity. These results indicate that the FGFR3 AT-III mRNAs are transcribed due to exon skipping with altered ligand binding specificity. These results suggest that the presence of soluble transcripts of FGFRs gene is a common feature due to mRNA splicing and this splicing plays an important role in the regulation of FGFRs function.
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PMID:Identification and characterization of soluble isoform of fibroblast growth factor receptor 3 in human SaOS-2 osteosarcoma cells. 1190 72

Latent TGF-beta-binding proteins (LTBPs) were initially identified through their binding to the growth factor. Three of the four known LTBPs are able to associate covalently with the small latent forms of TGF-beta and mediate their efficient secretion. LTBPs have subsequently been found to associate with the extracellular matrix. We report here the cDNA cloning and characterization of the human LTBP-3 protein, which is the smallest LTBP. The hLTBP-3 gene consists of 28 exons, including one alternatively spliced exon. The splice variant contains an additional epidermal-growth-factor-like repeat in the C-terminus. The gene is transcribed to produce a approximately 4.6 kb mRNA, which is expressed at high levels in human heart, skeletal muscle, prostate and ovaries and in certain osteosarcoma and fibroblastic cell lines. Antibodies were generated against recombinant fragment of hLTBP-3 and used to detect the protein and its secretion from cultured COS-7 and osteosarcoma cells. Immunoblotting analysis indicated that efficient secretion of overexpressed hLTBP-3 from COS-7 cells required co-expression of TGF-beta1, which resulted in the secretion of high molecular weight complexes of approximately 240 kDa. hLTBP-3 protein was secreted from cultured osteosarcoma cells as high molecular weight complexes rather than in the free form. Similar complexes were recognized with antibodies specific to beta1*LAP. These findings indicate that human LTBP-3 has an essential role in the secretion and targeting of TGF-beta1.
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PMID:Secretion of human latent TGF-beta-binding protein-3 (LTBP-3) is dependent on co-expression of TGF-beta. 1215 76


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