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)

Alterations in ras oncogene expression have been associated with increased cellular resistance to ionizing radiation. As an extension of studies with murine cell models, we have now explored the radioresponses of human osteosarcoma (HOS) sub-clones that differ in their EJras expression. Quantitative analysis revealed a tight correlation between the amounts of ras-encoded mRNA and p21 produced, and the degree of cell radioresistance. Interestingly, treatment of the ras-transformed cells with lovastatin, an inhibitor of p21ras post-translational processing via the mevalonate pathway, markedly decreased their radioresistance. Under the experimental conditions used, lovastatin prevented the membrane association, but not the biosynthesis, of p21. The decline in radiation resistance following lovastatin treatment could not be attributed to perturbation of cholesterol metabolism or to non-specific cell-cycle effects. In agreement, lovastatin did not alter the radiation responses of control HOS cells that do not express EJras, or those with an activated met oncogene. The results indicate that elevation in ras gene expression can lead to increased radioresistance of human tumor cells. It appears, however, that p21ras membrane localization is critical for maintenance of the radioresistant phenotype, thus providing a target for pharmacological intervention.
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PMID:Increased radioresistance of EJras-transformed human osteosarcoma cells and its modulation by lovastatin, an inhibitor of p21ras isoprenylation. 842 69

Efforts to investigate the progression of events that lead normal human cells in culture to become neoplastic in response to carcinogenic agents have been aided by the development of the suitable in vitro model systems. For initial human cell transformation studies, a flat, nontumorigenic clonal line, originally derived from a human osteosarcoma (HOS), was used. When treated with chemical carcinogens such as N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and 3-methyl-cholanthrene (3MC), the HOS cells underwent morphological alterations and acquired tumorigenic properties. These cell lines were very useful inasmuch as a non-ras cellular transforming gene, met, and an activated H-ras oncogene have been isolated from MNNG-transformed and 3MC-transformed HOS lines, respectively, by DNA transfection procedure. Alteration of p53 gene in chemically transformed HOS cell lines has recently been shown. Although carcinogens cause human cancer, normal human cells in culture have proven difficult to achieve. Neoplastic transformation of human cells in culture has recently been achieved by a stepwise fashion-immortalization and conversion of the immortalized cells to tumorigenic cells. One of the critical initial events in the progression of normal human cells to tumor cells is the escape from cellular senescence. With few exceptions, normal human cells require immortalization to provide a practical system for transformation studies. Thus, the role of carcinogenic agents in the development of human cancers is now being defined using a variety of human cells. The neoplastic transformation in human cell cultures is reviewed. In doing so, this author attempts to put into perspective the history of human cell transformation by carcinogenic agents, and to discuss the current state of the art in transformation of human cells in culture; thus providing insight into the molecular and cellular mechanisms involved in the conversion of normal cells to a neoplastic state of growth.
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PMID:Neoplastic transformation of human cells in vitro. 848 2

We investigated the structure and the expression of various oncogenes in three of the most common human bone tumors-osteosarcoma (36 samples from 34 patients), giant cell tumor (10 patients), and chondrosarcoma (18 patients)-in an attempt to identify the genetic alterations associated with these malignancies. Alterations of RB and p53 were detected only in osteosarcomas. Alterations of c-myc, N-myc, and c-fos were detected in osteosarcomas and giant cell tumors. Ras alterations (H-ras, Ki-ras, N-ras) were rare. Chondrosarcomas did not contain any detectable genetic alterations. Our results suggest that alterations of c-myc, N-myc, and c-fos oncogenes occur in osteosarcomas, in addition to those previously described for the tumor suppressor genes RB and p53. Moreover, statistical analyses indicate that c-fos alterations occur more frequently in osteosarcoma patients with recurrent or metastatic disease.
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PMID:Oncogene alterations in primary, recurrent, and metastatic human bone tumors. 889 2

Human herpesvirus 6A (HHV-6A) strain U1102 was previously shown to contain a 1473 bp transformation suppressor gene (ts) (Araujo et al., 1995). Ts inhibited transformation of NIH3T3 cells by H-ras and transcription of the H-ras and human immunodeficiency type 1 (HIV-1) promoters in transient transfection experiments. In the current study, stable NIH3T3 cell lines expressing ts protein were established by transfection with pRc-ts containing the ts gene under the control of the Rous sarcoma virus (RSV) long terminal repeat (LTR) and a neomycin selectable marker. Selected cell lines contained approximately one to two copies per cell of intact ts sequences, expressed ts protein and grew at approximately the same rate as parental NIH3T3 cells. These cell lines were protected from H-ras transformation while parental and NIH3T3 cells containing the ts gene cloned in the antisense orientation were not. Expression of the chloramphenicol acetyl transferase (CAT) gene under the control of the EJ-H-ras promoter was also suppressed in the ts cell lines but not when the CAT gene was under the control of the murine osteosarcoma virus LTR or human cytomegalovirus immediate early promoter. When NIH3T3 cell lines expressing ts protein were established by infection with the retrovirus, LNCts, the cells expressed ts protein and were protected from H-ras transformation. Furthermore, bovine papillomavirus type 1 (BPV-1) transformation was also suppressed in cells co-transfected with BPV-1 plus ts and in ts expressing cell lines transfected with BPV-1. The BPV-1 p89 and p2443 promoters were down-regulated in 3T3-ts lines. Because the human papillomavirus type 16 (HPV-16) p97 promoter has similarity to the BPV-1 p89 promoter, the ability of ts to suppress p97 was also tested. Like the H-ras and BPV-1 promoters, HPV-16 p97 was down-regulated in 3T3-ts lines. The data indicate the utility of ts against H-ras, BPV-1 and HPV-16 promoters and their respective oncogenes.
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PMID:Cell lines containing and expressing the human herpesvirus 6A ts gene are protected from both H-ras and BPV-1 transformation. 905 Sep 93

Protein kinase CK2 (formerly casein kinase II) exhibits elevated expression in a variety of cancers, induces lymphocyte transformation in transgenic mice, and collaborates with Ha-Ras in fibroblast transformation. To systematically examine the cellular functions of CK2, human osteosarcoma U2-OS cells constitutively expressing a tetracycline-regulated transactivator were stably transfected with a bidirectional plasmid encoding either catalytic isoform of CK2 (i.e. CK2alpha or CK2alpha') together with the regulatory CK2beta subunit in order to increase the cellular levels of either CK2 isoform. To interfere with either CK2 isoform, cells were also transfected with kinase-inactive CK2alpha or CK2alpha' (i. e. GK2alpha (K68M) or CK2alpha'(K69M)) together with CK2beta. In these cells, removal of tetracycline from the growth medium stimulated coordinate expression of catalytic and regulatory CK2 subunits. Increased expression of active forms of CK2alpha or CK2alpha' resulted in modest decreases in cell proliferation, suggesting that optimal levels of CK2 are required for optimal proliferation. By comparison, the effects of induced expression of kinase-inactive CK2alpha differed significantly from the effects of induced expression of kinase-inactive CK2alpha'. Of particular interest is the dramatic attenuation of proliferation that is observed following induction of CK2alpha'(K69M), but not following induction of CK2alpha(K68M). These results provide evidence for functional specialization of CK2 isoforms in mammalian cells. Moreover, cell lines exhibiting regulatable expression of CK2 will facilitate efforts to systematically elucidate its cellular functions.
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PMID:Inducible expression of protein kinase CK2 in mammalian cells. Evidence for functional specialization of CK2 isoforms. 1031 65

Tissue inhibitors of metalloproteinases-1 (TIMP-1) and TIMP-2 have growth-stimulating activity for a wide range of cell types. Ras, which comprises a family of three members, i.e, Ha-Ras, Ki-Ras, and H-Ras, is known to participate in growth control in all its facets, including cell proliferation, transformation, differentiation, and apoptosis. In this study, we tested the hypothesis that Ras might be involved in the cell growth-promoting activity of TIMPs. Using MG-63 human osteosarcoma cells, we demonstrated that both TIMP-1 and TIMP-2 caused an increase in the Ras-GTP level in a dose-dependent manner. Our previous results indicated that TIMP-1 activity is mediated through the tyrosine kinase (TYK)/mitogen-activated protein kinase (MAPK) pathway. Here, we demonstrated that Ras activation by TIMP-1 was inhibited by a specific TYK inhibitor, herbimycin A, suggesting that the TYK/MAPK signaling pathway was involved in Ras activation by TIMP-1. However, the activation of Ras by TIMP-2 was inhibited by an inhibitor specific for cyclic AMP-dependent protein kinase (PKA), H89, suggesting the involvement of the PKA-mediated pathway. Furthermore, TIMP-2 promoted the formation of a complex between Ras-GTP and phosphoinositide 3-kinase.
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PMID:Both tissue inhibitors of metalloproteinases-1 (TIMP-1) and TIMP-2 activate Ras but through different pathways. 1214 51

Some investigators have reported that the histological features of osteosarcoma (OS) arising in elderly patients are different from those in younger patients; however, a molecular biologic study of OS in elderly patients has not been documented. In this study, 23 cases of OS (15 osteoblastic and 8 MFH-like types) and 18 cases of MFH of bone in patients 40 years of age or older were analyzed for mutation of the p53 gene, amplification of the MDM2 gene, and mutation of the H-ras gene, using formalin-fixed paraffin-embedded materials. We also examined the expression of p53, MDM2, and p21WAF1 protein immunohistochemically and assessed the proliferative activities using the monoclonal antibody MIB-1. p53 immunoreactivity was recognized in 5 of 23 OS cases (22%), whereas p53 gene mutations were also detected in 5 of 23 OS cases (22%; osteoblastic [4/15; 27%] and MFH-like [1/8; 18%] types) and in 4 of 18 cases of MFH of bone (22%). There was a statistically significant correlation between p53 immunoreactivity and p53 mutation status in OS (P =.0482). All those cases of osteoblastic OS and MFH of bone that had p53 mutations, with the exception of one case of MFH of bone that had a silent mutation, showed aggressive biologic behavior (dead of disease within 12 mo), in contrast to the MFH-like OS cases (alive without disease at 22 mo). Three cases of OS (13%) and three cases of MFH of bone (17%) showed immunoreactivity for MDM2. As for gene alteration, three cases of OS (13%) and 3 cases of MFH of bone (17%) demonstrated MDM2 amplification. MDM2 amplification showed a significant correlation with the expression of MDM2 protein in OS (P =.0344). p21WAF1 expression was detected in three cases of OS (13%) and in six cases of MFH of bone (33%). MDM2 alteration and p21WAF1 expression were not observed in any of the cases of MFH-like OS. MIB-1-LI showed a statistically significant correlation with p53 immunoreactivity and MDM2 immunoreactivity in OS (P =.0307 and P =.0358, respectively). H-ras mutation at Codons 12 and 13 was not recognized in any of the cases of OS or MFH of bone. In conclusion, although treatment differences during the time of study make it difficult to compare survival analysis, in the current study, p53 mutation in osteoblastic OS and MFH of bone in elderly patients seemed to be closely associated with the progression of the tumor, which was not the case in MFH-like OS. Furthermore, MDM2 alteration and p21WAF1 expression were demonstrated only in osteoblastic OS and MFH of bone, whereas they were not recognized in MFH-like OS. Although the number of patients in this analysis was small, it would appear that MFH-like OS may have some characteristic biologic aspects when compared with osteoblastic OS and MFH of bone in elderly patients.
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PMID:Molecular analysis of p53, MDM2, and H-ras genes in osteosarcoma and malignant fibrous histiocytoma of bone in patients older than 40 years. 1218 Dec 74

Low-grade central osteosarcoma is an uncommon form that is characterized by a long premorbid history, and is compatible with prolonged survival after treatment. However, molecular abnormalities are rare in low-grade central osteosarcomas, whereas p53 mutations occur in approximately 20% of conventional high-grade osteosarcomas. In this study, 21 cases of low-grade central osteosarcoma were analyzed for mutations of the p53 gene, amplification of the MDM2 gene, and mutations of the H-ras gene using formalin-fixed, paraffin-embedded materials. We also examined the expression of p53, MDM2, and p21WAF1 protein immunohistochemically and assessed the proliferation activities using the monoclonal antibody MIB-1. One case (4.7%) showed strong p53 immunoreactivity, whereas p53 gene mutations were not detected at all. Seven cases (33.3%) showed immunoreactivity for MDM2 protein. As for gene alterations, MDM2 amplification was found in four cases (19.0%). p21WAF1 expression was detected in 12 cases (57.1%). MIB-1-LI showed very low levels in all the cases and no significant correlation with p53 or MDM2 immuno-reactivity. None of the tumors showed H-ras mutations. In conclusion, the number of p53 gene alterations in low-grade central osteosarcomas is lower than that in conventional high-grade osteosarcomas. MDM2 alterations and p21WAF1 expression might be involved in the tumorigenesis of low-grade central osteosarcomas.
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PMID:Molecular analysis of p53, MDM2 and H-ras genes in low-grade central osteosarcoma. 1531 Jan 47

Several studies have shown that forced expression of oncogenic H-ras can induce a senescence-like permanent growth arrest in normal cells. Here we report that expression of oncogenic H-ras in human osteosarcoma U2OS cells also resulted in a senescence-like flat and enlarged cell morphology and permanent growth arrest. In contrast to normal human fibroblasts, U2OS cells were arrested independently of the p16 and ARF tumor suppressors. Treatment with a MEK inhibitor or a p38MAPK inhibitor interrupted oncogenic H-ras-induced growth arrest in U2OS cells, suggesting that activation of MAPK pathways is important. To further determine whether this process is unique to oncogenic H-ras signaling, we examined the effect of oncogenic K-ras on normal cells and human osteosarcoma cells. Similar to oncogenic H-ras, oncogenic K-ras also induced senescence in normal fibroblasts, while transforming immortalized mouse fibroblasts. However, in contrast to oncogenic H-ras, oncogenic K-ras failed to induce a permanent growth arrest in osteosarcoma U2OS cells. Additionally, cells transduced with oncogenic K-ras exhibited distinguishable cellular changes compared to those transduced with oncogenic H-ras. In summary, we report for the first time that oncogenic H-ras signaling can trigger a senescence-like growth arrest in tumor cells, independent of the p16 and ARF tumor suppressors. This result suggests that tumor cells may harbor a senescence-like program that can be activated by ras signaling. Moreover, our study uncovered a cell type-dependent differential response to oncogenic K-ras, as compared to oncogenic H-ras.
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PMID:Differential oncogenic Ras signaling and senescence in tumor cells. 1549 1

Upregulation of the p16 tumor suppressor is a hallmark of senescence in human fibroblasts. In this study, we investigated potential protein modification of p16 in senescent human fibroblasts using 2D SDS-PAGE analysis. Three distinct p16 variants with isoelectric points of 5.2, 5.4, and 5.6, were consistently detected in normal human IMR90 fibroblasts that had undergone senescence due to forced expression of oncogenic H-ras or culture passage. Moreover, in contrast to short-term serum starvation, which induces quiescence, IMR90 fibroblasts cultured in low serum for a prolonged period exhibited senescent phenotypes and expression of the three p16 variants. All three p16 variants are unlikely phosphoproteins since they failed to react with antibodies against phospho-serine, and were resistant to the treatment with phosphatases. Functionally, co-immunoprecipitation assays using antibodies against cdk4 and/or cdk6 revealed that only the two most acidic p16 variants associated with cdk4/6. Moreover, senescence induced by the forced expression of p16 in early passage IMR90 fibroblasts or osteosarcoma U2OS cells was accompanied by expression of the two most acidic p16 variants, which also associated with cdk4/6. In summary, we report that prolonged serum starvation-induced senescence may provide an additional model for studying biochemical changes in senescence, including p16 regulation. Furthermore, induction of endogenous p16 in senescent human fibroblasts correlates with the expression of three distinct p16 variants independent of protein phosphorylation. Lastly, expression of the two cdk-bound variants is sufficient to induce senescence in human cells.
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PMID:Expression of p16INK4A variants in senescent human fibroblasts independent of protein phosphorylation. 1566 6


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