Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 4 de 4
Filter
Add more filters










Database
Language
Publication year range
1.
Cancer Res ; 69(8): 3291-9, 2009 Apr 15.
Article in English | MEDLINE | ID: mdl-19336574

ABSTRACT

Previous studies have established that UV irradiation results in epidermal growth factor receptor (EGFR) activation in keratinocytes. However, the signaling pathways and cellular effects related to this process remain incompletely elucidated. Herein, we describe for the first time that UVA-mediated EGFR activation results in beta-catenin tyrosine phosphorylation at the Y654 residue responsible for the dissociation of E-cadherin/alpha-catenin/beta-catenin complexes. Moreover, UVA induces an EGFR-dependent, but Wnt-independent, beta-catenin relocalization from the membrane to the nucleus followed by its association with T-cell factor 4 (TCF4). This newly formed beta-catenin/TCF4 complex binds to a specific site on matrix metalloproteinase 1 (MMP1) promoter and governs MMP1 gene and protein expression, as well as cell migration in collagen and gelatin. Altogether, these results suggest that UVA stimulates keratinocyte invasiveness through two coordinated EGFR-dependent processes: loss of cell-to-cell contact due to beta-catenin/E-cadherin/alpha-catenin dissociation and increased cell migration through extracellular matrix component degradation due to beta-catenin/TCF4-dependent MMP1 regulation. These events may represent an important step in epidermis repair following UVA injury and their abnormal regulation could contribute to photoaging and photocarcinogenesis.


Subject(s)
ErbB Receptors/metabolism , Keratinocytes/metabolism , Keratinocytes/radiation effects , Matrix Metalloproteinase 1/metabolism , TCF Transcription Factors/metabolism , beta Catenin/metabolism , Cell Adhesion/physiology , Humans , Phosphorylation/radiation effects , Signal Transduction/radiation effects , Transcription Factor 7-Like 2 Protein , Transcription, Genetic/radiation effects , Ultraviolet Rays
2.
Blood ; 111(4): 2269-79, 2008 Feb 15.
Article in English | MEDLINE | ID: mdl-18056483

ABSTRACT

Receptor or nonreceptor tyrosine kinases (TKs) are known to play an important role in leukemogenesis. Here we studied the level of protein tyrosine phosphorylations in a series of fresh AML samples and evaluated the effect of TK inhibitors. Compared with normal hematopoietic progenitors, a high level of tyrosine phosphorylation was detected in most acute myeloid leukemia (AML) samples. The Src family kinases (SFKs) appeared constitutively activated in most cases, including in the CD34(+)CD38(-)CD123(+) compartment as revealed by the level of phosphorylated tyrosine 416. Lyn was the major SFK family member expressed in an active form in AML cells where it was abnormally distributed throughout the plasma membrane and the cytosol as opposed to normal hematopoietic progenitors. The SFK inhibitor, PP2, strongly reduced the global level of tyrosine phosphorylations, inhibited cell proliferation, and induced apoptosis in patient samples without affecting normal granulomonocytic colony forming units. Moreover, silencing Lyn expression by small interfering RNA in primary AML cells strongly inhibited proliferation. Interestingly, a link between Lyn and the mTOR pathway was observed as PP2 and a Lyn knockdown both affected the phosphorylation of mTOR targets without inhibiting Akt phosphorylation. Lyn should be considered as a novel pharmacologic target for AML therapy.


Subject(s)
Leukemia, Myeloid, Acute/pathology , Oncogene Proteins, Viral/physiology , src-Family Kinases/physiology , Apoptosis/drug effects , Bone Marrow Cells/cytology , Bone Marrow Cells/drug effects , Bone Marrow Cells/pathology , Cell Line, Tumor , Chromones/pharmacology , Enzyme Inhibitors , Flow Cytometry , Humans , Morpholines/pharmacology , Phosphotyrosine/metabolism , RNA, Small Interfering/genetics , Reference Values , Sirolimus/pharmacology , U937 Cells
3.
Cancer Res ; 66(14): 7128-35, 2006 Jul 15.
Article in English | MEDLINE | ID: mdl-16854822

ABSTRACT

The effects of cell adhesion on leukemia cell proliferation remain poorly documented and somehow controversial. In this work, we investigated the effect of adhesion to fibronectin on the proliferation of acute myeloid leukemia (AML) cell lines (U937 and KG1a) and CD34+ normal or leukemic primary cells. We observed an increased rate of proliferation of AML cells when adhered to fibronectin, concomitant with accelerated S-phase entry and accumulation of CDC25A. Conversely, normal CD34+ cell proliferation was decreased by adhesion to fibronectin with a concomitant drop in CDC25A expression. Importantly, we showed that both small interfering RNA (siRNA)-mediated CDC25A down-regulation and a recently developed CDC25 pharmacologic inhibitor impaired this adhesion-dependent proliferation, establishing a functional link between CDC25A accumulation and adhesion-dependent proliferation in leukemic cells. CDC25A accumulation was found only slightly dependent on transcriptional regulation and essentially due to modifications of the proteasomal degradation of the protein as shown using proteasome inhibitors and reverse transcription-PCR. Interestingly, CDC25A regulation was Chk1 dependent in these cells as suggested by siRNA-mediated down-regulation of this protein. Finally, we identified activation of the phosphatidylinositol 3-kinase/Akt pathway as an adhesion-dependent regulation mechanism of CDC25A protein expression. Altogether, our data show that in leukemic cells adhesion to fibronectin increases CDC25A expression through proteasome- and Chk1-dependent mechanisms, resulting in enhanced proliferation. They also suggest that these adhesion-dependent proliferation properties of hematopoietic cells may be modified during leukemogenesis.


Subject(s)
cdc25 Phosphatases/biosynthesis , Acute Disease , Cell Adhesion/physiology , Cell Growth Processes/physiology , Checkpoint Kinase 1 , Fibronectins/metabolism , HL-60 Cells , Humans , Jurkat Cells , Leukemia, Myeloid/enzymology , Leukemia, Myeloid/genetics , Leukemia, Myeloid/pathology , Phosphatidylinositol 3-Kinases/metabolism , Proteasome Endopeptidase Complex/metabolism , Protein Kinases/metabolism , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , RNA, Small Interfering/genetics , TOR Serine-Threonine Kinases , U937 Cells , Up-Regulation , cdc25 Phosphatases/genetics , cdc25 Phosphatases/metabolism
4.
Blood ; 106(9): 3200-5, 2005 Nov 01.
Article in English | MEDLINE | ID: mdl-16020509

ABSTRACT

Telomerase catalytic subunit (hTERT) has been shown to play a critical role not only in telomere homeostasis but also in cellular survival, DNA repair, and genetic stability. In a previous study, we described that tumor necrosis factor-xalpha (TNFxalpha) induced in the leukemic KG1 cells a senescence state characterized by decreased hTERT activity followed by prolonged growth arrest, increasedx beta-galactosidase activity, telomere shortening, and major chromosomal instability. Interestingly, granulocyte-macrophage colony-stimulating factor (GM-CSF) abrogated all these events. In the present study, we show for the first time that TNFxalpha acts by inhibiting the hTERT gene in both normal CD34x+ cells and fresh leukemic cells. Using KG1 cells as a representative cellular model, we show that TNFxalpha induced sphingomyelin hydrolysis, ceramide production, and c-Jun N-terminal kinase (JNK) activation, all of which are critical components of TNFxalpha signaling, resulting in hTERT gene inhibition. Moreover, we provide evidence that the protective effect of GM-CSF is related to its capacity to interfere with both ceramide generation and ceramide signaling. Negative regulation of the hTERT gene may represent one mechanism by which TNFxalpha interferes with normal hemopoiesis.


Subject(s)
DNA-Binding Proteins/genetics , Gene Expression Regulation/drug effects , Leukemia/enzymology , Leukemia/genetics , Myeloid Cells/drug effects , Myeloid Cells/enzymology , Telomerase/genetics , Tumor Necrosis Factor-alpha/pharmacology , Cells, Cultured , Ceramides/metabolism , DNA-Binding Proteins/biosynthesis , DNA-Binding Proteins/metabolism , Enzyme Inhibitors/pharmacology , Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology , Humans , Mitogen-Activated Protein Kinases/metabolism , Telomerase/biosynthesis , Telomerase/metabolism , Tumor Necrosis Factor-alpha/physiology
SELECTION OF CITATIONS
SEARCH DETAIL
...