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)

Glucocorticoid (GC) administration induces atrophy of skin, bone, and other organs, partly by reducing tissue content of glycosaminoglycans, particularly hyaluronic acid (HA). We took advantage of the recent cloning of the three human hyaluronan synthase (HAS) enzymes (HAS1, HAS2 and HAS3), to explore the molecular mechanisms of this side effect. Northern and slot blots performed on RNA extracted from cultured dermal fibroblasts and the MG-63 osteoblast-like osteosarcoma cell line indicated that HAS2 is the predominant HAS mRNA in these cells. Incubation of both cell types for 24 h in the presence of 10(-6) M dexamethasone (DEX) resulted in a striking 97--98% suppression of HAS2 mRNA levels. Time-course studies in fibroblasts demonstrated suppression of HAS2 mRNA to 28% of control by 1 h, and to 1.2% of control by 2 h, after addition of DEX. Dose-response studies in fibroblasts indicated that the majority of the suppressive effect required concentrations characteristic of cell-surface GC receptors, a point confirmed by persistent DEX-induced suppression in the presence of RU486, an antagonist of classic cytosolic steroid hormone receptors. Nuclear run-off experiments showed a 70% suppression of HAS2 gene transcription in nuclei from DEX-treated fibroblasts, which is unlikely to fully explain the rapid 50--80-fold reduction in message levels. Experiments with actinomycin D (AMD) demonstrated that the message half-life was 25 min in cells without DEX, whereas the combination of AMD with DEX dramatically increased the half-life of HAS2 mRNA, suggesting that DEX acts by inducing a short-lived destabilizer of the HAS2 message. Direct assessment of HAS2 mRNA stability by wash-out of incorporated uridine label established a half-life of 31 min in cells without DEX, which substantially shortened in the presence of DEX. In conclusion, GCs induce a rapid and sustained, near-total suppression of HAS2 message levels, mediated through substantial decreases in both gene transcription and message stability. These effects may contribute to the loss of HA in GC-treated organs.
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PMID:Glucocorticoids induce a near-total suppression of hyaluronan synthase mRNA in dermal fibroblasts and in osteoblasts: a molecular mechanism contributing to organ atrophy. 1086 Dec 15

Recently three isoforms of hyaluronan synthase (HAS), the enzyme responsible for hyaluronate/hyaluronan (HA) biosynthesis, have been cloned, allowing us to study their expression pattern. Our objective was to determine which of the HAS isoenzymes were expressed in human articular chondrocytes, synovial fibroblasts and osteosarcoma cells, whether their expression could be modulated by growth factors (insulin-like growth factor-1, basic fibroblast growth factor and transforming growth factor (TGF-beta1) and cytokines [interleukin 1beta1 (IL-1beta)], and whether changes in the rate of HA synthesis by the cells correlated with changes in mRNA levels for one or more of the HAS isoforms. All three HAS isoforms were found to be expressed in the cultured cells analysed in this study, although the relative proportions varied for each cell type. HAS2 mRNA was usually predominant in chondrocytes, whereas synovial cells contained increased amounts of HAS1. HAS3 was always the least abundant message. The rapidly growing osteosarcoma cells contained almost exclusively HAS2 message. HAS usage in uncultured cartilage and synovial tissues was similar to that in the cultured cells, with HAS2 message being the predominant species in cartilage and HAS1 usually being the predominant species in synovium. HA synthesis was stimulated by the growth factors, but the extent of the response was cell-type specific. Synovial cells responded particularly well to IL-1beta, and showed a unique synergistic response when IL-1beta was used in combination with TGF-beta1. This response was much reduced in articular chondrocytes and absent in the osteosarcoma cells. Analysis of changes in HAS message levels indicated that there was often no correlation with the changes in HA secretion following exposure to growth factors. Although HAS-1 mRNA was increased in synovial cells after exposure to TGF-beta1/IL-1beta, the magnitude of the change was far less than the effect on HA synthesis. Our data thus suggest that HAS gene usage is tissue specific, and the regulation by growth factors is unique for each HAS gene and is further modulated by cell-specific factors. In addition, regulation of HA biosynthesis appears to be multi-faceted, with control of HAS gene expression and mRNA levels being only one aspect of this process.
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PMID:Differential regulation and expression of hyaluronan synthases in human articular chondrocytes, synovial cells and osteosarcoma cells. 1117 Oct 74

We report the identification of a natural antisense mRNA of hyaluronan synthase 2 that we have chosen to designate as HASNT (for HA synthase 2 antisense) in human and mouse. HASNT is transcribed from the opposite strand of the HAS2 gene locus and is represented by several independent expressed sequence tags in human. Portions of the mouse Hasnt gene were identified through an exon-trapping approach. Sequence conservation is extremely low between human and mouse HASNT, and it is not clear whether these mRNAs contain functional open reading frames. HASNT has an alternate splice site in both human and mouse. This splice site is located at an identical position within the gene in both species and results in mRNAs of two different lengths. In each species, the antisense portion of the HASNT gene is complementary to the first exon of HAS2, which represents the 5'-untranslated region. To study the biological activity of HASNT, two human expressed sequence tag clones, representing long and short HASNT splice variants, were cloned into a tetracycline-inducible vector and were stably transfected into human osteosarcoma U2-OS Tet-on cells. The long and short HASNT-expressing cells had a reduction in HAS2 mRNA levels up to 94 and 86%, respectively, whereas hyaluronan biosynthesis was inhibited by 40 and 37%, respectively. Cell proliferation was reduced throughout the time frame of the experiment. Exogenous high molecular mass hyaluronan failed to rescue the suppressed cell proliferation, whereas adenoviral-mediated overexpression of hyaluronan synthase 3, which stimulated endogenous hyaluronan biosynthesis, was able to rescue. Collectively, our data suggest that natural antisense mRNAs of HAS2 are able to regulate HAS2 mRNA levels and hyaluronan biosynthesis in a cell culture model system and may have an important and novel regulatory role in the control of HAS2, HA biosynthesis, and HA-dependent cell functions in vivo.
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PMID:Natural antisense mRNAs to hyaluronan synthase 2 inhibit hyaluronan biosynthesis and cell proliferation. 1584 73

Several studies have suggested that increased production of hyaluronan (HA) is associated with metastatic behavior in various malignant tumors. To our knowledge, HA molecular weights required for metastasis are still unsolved in osteosarcoma. We examined the size of HA and hyaluronan synthase (HAS) isoforms related to biological functions required for metastasis in the LM8 stably highly metastatic osteosarcoma cell line. We found that HA of molecular weight which HAS3 produces enhanced biological functions related to metastasis such as cell proliferation, invasion, and degradation of extracellular matrix. Moreover, cell proliferation and invasion were inhibited by suppressing the activity of HAS3 expressed in LM8 cells, using hyaluronan synthase suppressor, 4-methylumbelliferone (MU). HA with the molecular weight related to HAS2 was the most adherent to CD44 in LM8 cells, suggesting that HAS2 may play an important role in pericellular coat formation. These results suggest that HAS3-related HA enhances crucial biological activities necessary for metastasis and that HAS2-related HA offers an advantageous environment for osteosarcoma cells.
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PMID:HAS3-related hyaluronan enhances biological activities necessary for metastasis of osteosarcoma cells. 1677 98