Bcl-xL Level (bcl-xl + level)

Distribution by Scientific Domains

Selected Abstracts

Contribution of the Src family of kinases to the appearance of malignant phenotypes in renal cancer cells

Yuko Yonezawa
Abstract Although the constitute activation of the Src family of kinases (Src) has been established as a poor prognostic factor in several types of cancer, the role of Src in renal cell carcinoma (RCC) has not been defined. This study aimed to determine whether Src could contribute to the appearance of malignant phenotypes in RCC. The role of Src in the appearance of malignant phenotypes in RCC was examined in two human renal cancer cell lines, Caki-1 from human metastatic RCC and ACHN from human primary RCC. Src activity in Caki-1 cells was higher than that in ACHN cells, and this difference corresponded to the difference of PP1 (a Src family inhibitor)-induced cytotoxicity on the two cells. The difference in cytotoxicity between the cells did not depend on cell cycle regulation but on the induction of apoptosis, and the difference in apoptosis particularly related to the reduction of the Bcl-xL level. Furthermore, in Caki-1 cells with higher Src activity, Src stimulated the production of vascular endothelial growth factor (VEGF), partially via the activation of Stat3, and the inhibition of Src activity caused a reduction of the VEGF level in serum, angiogenesis, and tumor development in a xenograft model. These results suggested that Src contributed to the appearance of malignant phenotypes in renal cancer cells, particularly due to the resistance against apoptosis by Bcl-xL and angiogenesis stimulated by Src-Stat3-VEGF signaling. © 2005 Wiley-Liss, Inc. [source]

IL-7 inhibits dexamethasone-induced apoptosis via Akt/PKB in mature, peripheral T cells

Hadassah Sade
Abstract We have investigated the mechanism of IL-7-mediated inhibition of dexamethasone-induced apoptosis in T cells. Broad-spectrum caspase inhibitors block dexamethasone-triggered nuclear fragmentation, but not the loss of mitochondrial transmembrane potential or membrane integrity in CD3+ mature T cells isolated from adult mouse spleens. IL-7 blocked dexamethasone-induced apoptosis and the processing of caspase-3 and caspase-7. IL-7 also blocked dexamethasone-triggered dephosphorylation of the serine-threonine kinase Akt/PKB and its target, the Ser136 residue in Bad. The loss of anti-apoptotic proteins Bcl-xL and inhibitor of apoptosis protein-2 (IAP-2) was also blocked by IL-7. The protective effect was attenuated by pharmacological inhibitors of phosphatidylinositol-3 kinase (PI3K) with one exception: inhibition of PI3K did not abrogate Bcl-xL expression in the presence of IL-7. The anti-apoptotic role of Akt suggested by these experiments was tested by overexpression of constitutively active Akt, which blocked dexamethasone-induced apoptosis and elevated IAP-2 but not Bcl-xL levels in a mature T cell line. Thus, IL-7 regulates IAP-2 expression and inhibits dexamethasone-induced apoptosis by activating Akt via PI3K-dependent signaling, but regulates Bcl-xL expression via a PI3K-independent pathway in mature T cells. [source]

TG101209, a novel JAK2 inhibitor, has significant in vitro activity in multiple myeloma and displays preferential cytotoxicity for CD45+ myeloma cells,

Vijay Ramakrishnan
Interaction of myeloma cells with the bone marrow microenvironment is mediated in large part through different cytokines, especially VEGF and IL6. These cytokines, especially IL6, leads to upregulation of the JAK/STAT pathway in myeloma cell, contributing to increased proliferation, decreased apoptosis, and acquired drug resistance. Here, we examined the preclinical activity of a novel JAK2 inhibitor TG101209. TG101209 induced dose- and time-dependent cytotoxicity in a variety of multiple myeloma (MM) cell lines. The induction of cytotoxicity was associated with inhibition of cell cycle progression and induction of apoptosis in myeloma cell lines and patient-derived plasma cells. Evaluation of U266 cell lines and patient cells, which have a mix of CD45 positive and negative cells, demonstrated more profound cytotoxicity and antiproliferative activity of the drug on the CD45+ population relative to the CD45, cells. Exploring the mechanism of action of TG101209 indicated downregulation of pJak2, pStat3, and Bcl-xl levels with upregulation of pErk and pAkt levels indicating cross talk between signaling pathways. TG101209, when used in combination with the PI3K inhibitor LY294002, demonstrated synergistic cytotoxicity against myeloma cells. Our results provide the rationale for clinical evaluation of TG101209 alone or in combination with PI3K/Akt inhibitors in MM. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc. [source]

Endogenous and Exogenous Fibroblast Growth Factor 2 Support Survival of Chick Retinal Neurons by Control of Neuronal Neuronal bcl-xL and bcl-2 Expression Through a Fibroblast Berowth Factor Receptor 1- and Erk-Dependent Pathway

Laurent Désiré
Abstract : Fibroblast growth factor (FGF) 2 is a survival factor for various cell types, including retinal neurons. However, little is understood about the molecular bases of the neuroprotective role of FGF2 in the retina. In this report, FGF2 survival activity was studied in chick retinal neurons subjected to apoptosis by serum deprivation. Exogenous FGF2 supported neuronal survival after serum deprivation and increased neuronal bcl-xL and bcl-2 expression, through binding to its receptor R1 (FGF-R1), and subsequent extracellular signal-regulated kinase (ERK) activation. Endogenous FGF2 was transiently overexpressed after serum deprivation. Its down-regulation by antisense oligonucleotides and blockade of its signaling pathway (binding to FGF-R1, tyrosine phosphorylation, and ERK inhibition) decreased bcl-xL and bcl-2 levels and and enhanced apoptosis, suggesting that endogenous FGF2 supported neuronal survival through a pathway similar to that of exogenous FGF2. This pathway may serve to up-regulate, or maintain, bcl-xL and bcl-2 levels that normally decrease during the onset of apoptosis. Indeed, long-term ERK activation and high bcl-xL levels are necessary for the survival activity of both exogenous and endogenous FGF2. Because FGF2 is upregulated following retinal injury in vivo, we suggest that an injury-stimulated autocrine/paracrine FGF2 loop may serve to maintain high levels of survival proteins, such as Bcl-xL, through ERK activation in retinal neurons. [source]