580 resultados para oncogene
Resumo:
Osteopontin (OPN) is a phosphorylated glycoprotein that binds to alpha v-containing integrins and is important in malignant transformation and cancer. Previously, we have utilized suppressive subtractive hybridization between mRNAs isolated from the Rama 37 (R37) rat mammary cell line and a subclone rendered invasive and metastatic by stable transfection with an expression vector for OPN to identify RAN GTPase (RAN) as the most overexpressed gene, in addition to that of OPN. Here we show that transfection of noninvasive R37 cells with an expression vector for RAN resulted in increased anchorage-independent growth, cell attachment and invasion through Matrigel in vitro, and metastasis in syngeneic rats. This induction of a malignant phenotype was induced independently of the expression of OPN, and was reversed by specifically reducing the expression of RAN using small-interfering RNAs. By using a combination of mutant protein and inhibitors, it was found that RAN signal transduction occurred through the c-Met receptor and PI3 kinase. This study therefore identifies RAN as a novel effector of OPN-mediated malignant transformation and some of its downstream signaling events in a mammary epithelial model of cancer invasion/metastasis.
Resumo:
Death receptors can directly (type I cells) or indirectly induce apoptosis by activating mitochondrial-regulated apoptosis (type II cells). The level of caspase 8 activation is thought to determine whether a cell is type I or II, with type II cells less efficient at activating this caspase following death receptor activation. FLICE-inhibitory protein (FLIP) blocks death receptor-mediated apoptosis by inhibiting caspase 8 activation; therefore, we assessed whether silencing FLIP could convert type II cells into type I. FLIP silencing-induced caspase 8 activation in Bax wild-type and null HCT116 colorectal cancer cells; however, complete caspase 3 processing and apoptosis were only observed in Bax wild-type cells. Bax-null cells were also more resistant to chemotherapy and tumor necrosis factor-related apoptosis inducing ligand and, unlike the Bax wild-type cells, were not sensitized to these agents by FLIP silencing. Further analyses indicated that release of second mitochondrial activator of caspases from mitochondria and subsequent inhibition of X-linked inhibitor of apoptosis protein (XIAP) was required to induce full caspase 3 processing and apoptosis following FLIP silencing. These results indicate that silencing FLIP does not necessarily bypass the requirement for mitochondrial involvement in type II cells. Furthermore, targeting FLIP and XIAP may represent a therapeutic strategy for the treatment of colorectal tumors with defects in mitochondrial-regulated apoptosis.
Resumo:
Most cytotoxic drugs kill cells by instigating the process of apoptosis and it has been suggested that apoptotic markers may provide an indication of tumour chemosensitivity. The aim of this study was to determine if such a relationship exists in acute myeloid leukaemia (AML). The levels of spontaneous apoptosis, bcl-2 and bax were evaluated in 56 newly diagnosed AML patients to determine if they correlated with a response to cytotoxic therapy. Spontaneous apoptosis was lower, but bcl-2, bax and the bcl-2/bax ratio were higher in AML compared with normal individuals. AML patients with high bax expression at diagnosis had significantly better prognosis for disease-free survival, event-free survival and overall survival (P = 0.016). In the standard risk group, high bax expression was in keeping with significantly improved survival. Multivariate analysis revealed bax to be an independent predictor of survival. There was a significant reduction in bcl-2 and bax expression when AML patients entered complete remission and also in relapsed AML patients who entered a second remission. This study suggests that bax is a useful prognostic indicator in AML and may assist with therapeutic decision-making for patients in the standard risk category.
Resumo:
The radiation-induced bystander effect (RIBE) increases the probability of cellular response and therefore has important implications for cancer risk assessment following low-dose irradiation and for the likelihood of secondary cancers after radiotherapy. However, our knowledge of bystander signaling factors, especially those having long half-lives, is still limited. The present study found that, when a fraction of cells within a glioblastoma population were individually irradiated with helium ions from a particle microbeam, the yield of micronuclei (MN) in the nontargeted cells was increased, but these bystander MN were eliminated by treating the cells with either aminoguanidine (an inhibitor of inducible nitric oxide (NO) synthase) or anti-transforming growth factor beta1 (anti-TGF-beta1), indicating that NO and TGF-beta1 are involved in the RIBE. Intracellular NO was detected in the bystander cells, and additional TGF-beta1 was detected in the medium from irradiated T98G cells, but it was diminished by aminoguanidine. Consistent with this, an NO donor, diethylamine nitric oxide (DEANO), induced TGF-beta1 generation in T98G cells. Conversely, treatment of cells with recombinant TGF-beta1 could also induce NO and MN in T98G cells. Treatment of T98G cells with anti-TGF-beta1 inhibited the NO production when only 1% of cells were targeted, but not when 100% of cells were targeted. Our results indicate that, downstream of radiation-induced NO, TGF-beta1 can be released from targeted T98G cells and plays a key role as a signaling factor in the RIBE by further inducing free radicals and DNA damage in the nontargeted bystander cells.
Resumo:
It is ten years since the publication of three papers describing the cloning of a new proto-oncogene serine/threonine kinase termed protein kinase B (PKB)/Akt. Key roles for this protein kinase in cellular processes such as glucose metabolism, cell proliferation, apoptosis, transcription and cell migration are now well established. The explosion of publications involving PKB/Akt in the past three years emphasizes the high level of current interest in this signalling molecule. This review focuses on tracing the characterization of this kinase, through the elucidation of its mechanism of regulation, to its role in regulating physiological and pathophysiological processes,to our current understanding of the biology of PKB/Akt, and prospects for the future.
Resumo:
The proto-oncogene Ras undergoes a series of post-translational modifications at its carboxyl-terminal CAAX motif that are essential for its proper membrane localization and function. One step in this process is the cleavage of the CAAX motif by the enzyme Ras-converting enzyme 1 (RCE1). Here we show that the deubiquitinating enzyme USP17 negatively regulates the activity of RCE1. We demonstrate that USP17 expression blocks Ras membrane localization and activation, thereby inhibiting phosphorylation of the downstream kinases MEK and ERK. Furthermore, we show that this effect is caused by the loss of RCE1 catalytic activity as a result of its deubiquitination by USP17. We also show that USP17 and RCE1 co-localize at the endoplasmic reticulum and that USP17 cannot block proliferation or Ras membrane localization in RCE1 null cells. These studies demonstrate that USP17 modulates Ras processing and activation, at least in part, by regulating RCE1 activity.
Resumo:
Osteopontin is a secreted, integrin-binding and phosphorylated acidic glycoprotein, which has an important role in tumour progression. We have shown that Wnt, Ets, AP-1, c-jun and beta-catenin/Lef-1/Tcf-1 stimulates OPN transcription in rat mammary carcinoma cells by binding to a specific promoter sequence. However, co-repressors of OPN have not been identified. In this study, we have used the bacterial two-hybrid system to isolate cDNA-encoding proteins that bind to OPN and modulate its role in malignant transformation. Using this approach we isolated interferon-induced transmembrane protein 3 gene (IFITM3) as a potential protein partner. We show that IFITM3 and OPN interact in vitro and in vivo and that IFITM3 reduces osteopontin (OPN) mRNA expression, possibly by affecting OPN mRNA stability. Stable transfection of IFITM3 inhibits OPN, which mediates anchorage-independent growth, cell adhesion and cell invasion. Northern blot analysis revealed an inverse mRNA expression pattern of IFITM3 and OPN in human mammary cell lines. Inhibition of IFITM3 by antisense RNA promoted OPN protein expression, enhanced cell invasion by parental benign non-invasive Rama 37 cells, indicating that the two proteins interact functionally as well. We also identified an IFITM3 DNA-binding domain, which interacts with OPN, deletion of which abolished its inhibitive effect on OPN. This work has shown for the first time that IFITM3 physically interacts with OPN and reduces OPN mRNA expression, which mediates cell adhesion, cell invasion, colony formation in soft agar and metastasis in a rat model system. Oncogene (2010) 29, 752-762; doi: 10.1038/onc.2009.379; published online 9 November 2009
Resumo:
The Hox family are master transcriptional regulators of developmental processes, including hematopoiesis. The Hox regulators, caudal homeobox factors (Cdx1-4), and Meis1, along with several individual Hox proteins, are implicated in stem cell expansion during embryonic development, with gene dosage playing a significant role in the overall function of the integrated Hox network. To investigate the role of this network in normal and aberrant, early hematopoiesis, we employed an in vitro embryonic stem cell differentiation system, which recapitulates mouse developmental hematopoiesis. Expression profiles of Hox, Pbx1, and Meis1 genes were quantified at distinct stages during the hematopoietic differentiation process and compared with the effects of expressing the leukemic oncogene Tel/PDGFRß. During normal differentiation the Hoxa cluster, Pbx1 and Meis1 predominated, with a marked reduction in the majority of Hox genes (27/39) and Meis1 occurring during hematopoietic commitment. Only the posterior Hoxa cluster genes (a9, a10, a11, and a13) maintained or increased expression at the hematopoietic colony stage. Cdx4, Meis1, and a subset of Hox genes, including a7 and a9, were differentially expressed after short-term oncogenic (Tel/PDGFRß) induction. Whereas Hoxa4-10, b1, b2, b4, and b9 were upregulated during oncogenic driven myelomonocytic differentiation. Heterodimers between Hoxa7/Hoxa9, Meis1, and Pbx have previously been implicated in regulating target genes involved in hematopoietic stem cell (HSC) expansion and leukemic progression. These results provide direct evidence that transcriptional flux through the Hox network occurs at very early stages during hematopoietic differentiation and validates embryonic stem cell models for gaining insights into the genetic regulation of normal and malignant hematopoiesis.
Resumo:
CCN3, a founding member of the CCN family of growth regulators, was linked with hematology in 2003(1) when it was detected in human serum. CCN3 is expressed and secreted by hematopoietic progenitor cells in normal bone marrow. CCN3 acts through the core stem cell signalling pathways including Notch and Bone Morphogenic Protein, connecting CCN3 with the modulation of self-renewal and maturation of a number of cell lineages including hematopoietic, osteogenic and chondrogenic. CCN3 expression is disrupted in Chronic Myeloid Leukemia as a consequence of the BCR-ABL oncogene and allows the leukemic clone to evade growth regulation. In contrast, naive cord blood progenitors undergo enhanced clonal expansion in response to CCN3. Altered CCN3 expression is associated with numerous solid tumors including glioblastoma, melanoma. adrenocortical tumours, prostate cancer and bone malignancies including osteosarcoma. Mature CCN3 protein has five distinct modules and truncated protein variants with altered function are found in many cancers. Regulation by CCN3 is therefore cell type and isoform specific. CCN3 has emerged as a key player in stem cell regulation, hematopoiesis and a crucial component within the bone marrow microenvironment. (c) 2008 Elsevier Ltd. All rights reserved.
Resumo:
Although the potential role of Pim2 as a cooperative oncogene has been well described in lymphoma, its role in leukemia has remained largely unexplored. Here we show that high expression of Pim2 is observed in patients with acute promyelocytic leukemia (APL). To further characterize the cooperative role of Pim2 with promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR alpha), we used a well-established PML-RAR alpha (PR alpha) mouse model. Pim2 coexpression in PR alpha-positive hematopoietic progenitor cells (HPCs) induces leukemia in recipient mice after a short latency. Pim2-PR alpha cells were able to repopulate mice in serial transplantations and to induce disease in all recipients. Neither Pim2 nor PR alpha alone was sufficient to induce leukemia upon transplantation in this model. The disease induced by Pim2 overexpression in PR alpha cells contained a slightly higher fraction of immature myeloid cells, compared with the previously described APL disease induced by PR alpha. However, it also clearly resembled an APL-like phenotype and showed signs of differentiation upon all-trans retinoic acid (ATRA) treatment in vitro. These results support the hypothesis that Pim2, which is also a known target of Flt3-ITD (another gene that cooperates with PML-RAR alpha), cooperates with PR alpha to induce APL-like disease. (Blood. 2010; 115(22): 4507-4516)
Resumo:
Evidence that activating mutations of the KRAS oncogene abolish the response to anti-epidermal growth factor receptor therapy has revolutionized the treatment of advanced colorectal cancer. This has resulted in the urgent demand for KRAS mutation testing in the clinical setting to aid choice of therapy. The Am of this study was to evaluate six different KRAS mutation detection methodologies on two series of primary colorectal cancer samples. Two series of 80 frozen and 74 formalin-fixed paraffin-embedded tissue samples were sourced and DNA was extracted at a central site before distribution to seven different testing sites. KRAS mutations in codons 12 and 13 were assessed by using single strand conformation polymorphism analysis, pyrosequencing, high resolution melting analysis, dideoxy sequencing, or the commercially available TIB Molbiol (Berlin, Germany) or DxS Diagnostic innovations (Manchester, UK) kits. in frozen tissue samples, concordance in KRAS status (defined as consensus in at least five assays) was observed in 66/80 (83%) cases. In par-affin tissue, concordance was 46/74 (63%) if all assays were considered or 71/74 (96%) using the five best performing assays. These results demonstrate that a variety of detection methodologies are suitable and provide comparable results for KRAS mutation analysis of clinical samples. (J Mol Diagn 2009, 11:543-552; DOI: 10.2353/jmoldx.2009.090057)
Resumo:
In vitro experiments have shown the PIM1 kinase to have diverse biological roles in cell survival, proliferation and differentiation. In humans, PIM1 is often expressed in both normal and transformed cells. The PIM1 kinase is a true oncogene implicated in early transformation and tumour progression in haematopoietic malignancies and prostate carcinomas. it is associated with aggressive subgroups of lymphoma, is a marker of poor prognosis in prostate carcinomas and has been suggested to have a role in hormone insensitivity of prostate malignancies. PIM1 has a possible role in other carcinomas with 6p21 genomic alterations. On one hand, PIM1 (due to its role in malignancy) appears to be a promising target for drug development programmes but, on the other hand, the complexity of its molecular structure has posed challenges in the development of PIM1 inhibitors. In this review we discuss PIM1 expression in human tissues (including some new data from our laboratory), its role in human malignancies, as well as the possibilities and challenges in the development of target therapy for PIM1. (c) 2008 Elsevier Ltd. All rights reserved.