Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oncogenic protein Bcl-2 functions as a potent inhibitor of programmed cell death. This survival activity has been shown in some settings to be influenced by the Bcl-2 phosphorylation state. It has been demonstrated that treatment with microtubule-targeted agents results in phosphorylation of both Raf-1 kinase and Bcl-2. The Bcl-2-related family member Bcl-xL also exhibits a death suppressive activity, but its potential for phosphorylation following exposure to drugs that interact with microtubules has not been evaluated. Several tumor cell lines with low or undetectable levels of Bcl-2 protein expression were found to express Bcl-xL. A more slowly migrating Bcl-xL band was observed on immunoblots after cells were treated with microtubule-targeted agents. The appearance of this band was responsive to dose and was absent when the cell lysates were treated with lambda protein phosphatase. Using a Bcl-xL-specific monoclonal antibody, the phosphorylated form of Bcl-xL was immunoprecipitated from cells treated with paclitaxel and metabolically labeled with 32P-labeled inorganic orthophosphate. Herein, we report that Bcl-xL is phosphorylated in malignant cells after incubation with agents that target tubulin, including paclitaxel, vincristine, vinblastine, colchicine, and nocodazole. Moreover, paclitaxel-resistant ovarian carcinoma cell lines that have mutations in tubulin failed to exhibit phosphorylation of Bcl-xL after paclitaxel exposure, but they did demonstrate Bcl-xL phosphorylation in the presence of other tubulin-targeting agents. As observed for Bcl-2, phosphorylation of Bcl-xL was accompanied by phosphorylation of Raf-1. Interestingly, phosphorylation of these three proteins failed to occur or was much less pronounced when cells grown at high density were challenged with drug. Also, reduced Raf-1 expression, observed after treatment of cells with geldanamycin prior to and during incubation with the microtubule-active drugs, correlated with diminished Bcl-xL phosphorylation. Taken together, these results suggest that Bcl-xL, like Bcl-2, is phosphorylated by agents that disrupt microtubule architecture. By analogy with Bcl-2, this phosphorylation may play a critical role in modulating Bcl-xL function and may be an important determinant of microtubule-directed chemotherapeutic efficacy in human tumors.
 ...
PMID:Bcl-xL is phosphorylated in malignant cells following microtubule disruption. 969 63

Prior investigations document that proliferative signaling cascades, under some circumstances, initiate apoptosis, although mechanisms that dictate the final outcome are largely unknown. In COS-7 cells, ceramide signals Raf-1 activation through Ras (Zhang, Y., Yao, B., Delikat, S., Bayoumy, S., Lin, X. H., Basu, S., McGinley, M., Chan-Hui, P. Y., Lichenstein, H., and Kolesnick, R. (1997) Cell 89, 63-72), but not apoptosis. However, expression of small amounts of the pro-apoptotic Bcl-2 family member, BAD, conferred ceramide-induced apoptosis onto COS-7 cells. Ceramide signaled apoptosis in BAD-expressing cells by a pathway involving sequentially kinase suppressor of Ras (KSR)/ceramide-activated protein kinase, Ras, c-Raf-1, and MEK1. Downstream, this pathway linked to BAD dephosphorylation at serine 136 by prolonged inactivation of Akt/PKB. Further, mutation of BAD at serine 136 abrogated ceramide signaling of apoptosis. The present study indicates that when ceramide signals through the Ras/Raf cascade, the availability of a single target, BAD, may dictate an apoptotic outcome.
 ...
PMID:BAD enables ceramide to signal apoptosis via Ras and Raf-1. 980 8

This is the first report demonstrating that NIH/3T3 fibroblasts utilize the Raf-1/MAPK pathway to sensitize themselves to tumor necrosis factor-alpha (TNF-alpha) cytotoxicity under Ha-rasVal12 oncogene-overexpressed conditions. This paper clearly shows that the sensitivity of NIH/3T3 cells to TNF-alpha cytotoxicity positively correlated with the expression level of activated Ha-ras transgene, which was manipulated either positively by isopropyl-beta-d-thiogalactoside (IPTG) induction or negatively by a ribozyme or a dominant negative Ras suppression. Further analysis revealed that after TNF-alpha treatment, Ha-ras-overexpressed transformants underwent apoptosis. Overexpression of dominant negative Raf-1, Rac1, or RhoA in the Ha-ras transformants clarified that among these factors, only dominant negative Raf-1 could reverse the cell sensitivity to TNF-alpha, indicating that Raf-1, as a proapoptotic factor, indeed participates in TNF-alpha cytotoxicity. The anti-apoptotic roles of Bcl-2 and PI(3) kinase are also demonstrated by the Ha-ras transformants which became more resistant to TNF-alpha while overexpressing Bcl-2 or the activated p110 catalytic subunit. The analyses of the cell cycle and nuclear transcription factor activities revealed that TNF-alpha treatment caused the Ha-ras overexpressed transformants to shift from S to G0/G1 phase and increased the responses of AP-1, c-fos, and c-myc. Taken together, we suggest that the possible action of Ha-ras overexpression to sensitize TNF-alpha-treated fibroblasts is predominantly through the Ras/Raf-1/MAPK pathway to increase the responses of AP-1, c-fos, and c-myc, which are possibly involved in the aberration of cell cycle machinery, and subsequently to turn on the death program.
 ...
PMID:Selective activation of Ha-ras(val12) oncogene increases susceptibilityof NIH/3T3 cells to TNF-alpha. 1022 51

BAG-1 is a Hsp70/Hsc70-binding protein that interacts with Bcl-2, Raf-1, steroid hormone receptors, Siah-1, and hepatocyte growth factor (HGF) receptors, implying multiple functions for the BAG-1 protein. Here, we provide evidence that gene transfer-mediated overexpression of BAG-1 markedly enhances the motility of human gastric cancer cells. Two independent in vitro migration assays showed that the BAG-1-expressing MKN74 cells exhibited more active migration compared with control transfectants or parent MKN74 cells. In MKN74 cells, the overexpression of BAG-1 affected neither cell adhesion capability nor migration responses to HGF. The promotive effect of BAG-1 on cell migration was similarly observed in transfectants of another human gastric cancer MKN45 cell line. In BAG-1 transfected gastric cancer MKN74 cells, BAG-1 colocalized with cytokeratin as well as actin filaments, and was concentrated at membrane ruffles induced by lysophosphatidic acid (LPA). Taken together, these studies demonstrate that BAG-1 has a novel function as promoter of cell migration in human gastric cancer cells, possibly through cooperation with cytoskeletal proteins.
 ...
PMID:BAG-1 accelerates cell motility of human gastric cancer cells. 1035 30

Serum deprivation of Ha-ras-transformed brown adipocyte cell line resulted in a dramatic apoptotic cell death, as detected either by DNA laddering or by an increase in the percentage of hypodiploid cells or by nuclei condensation and fragmentation, as compared with immortalized cell line or primary fetal brown adipocytes. Moreover, transient transfection of immortalized brown adipocytes with a constitutively active ras gene (Ha-raslys12) mimics the high rate of apoptosis detected in the transformed cell line. On the other hand, transient transfection of the dominant-negative construct of raf-1 rescued serum-deprived Ha-ras-transformed brown adipocytes from apoptosis, decreasing the percentage of hypodiploid cells, the external display of phosphatidylserine, and the DNA laddering. However, inhibition of mitogen-activated protein kinase with PD098059 did not preclude apoptosis and in fact increased the rate of apoptosis observed in serum-deprived Ha-ras-transformed cells, indicating that the Ras/Raf-1 pathway induced apoptosis throughout a mitogen-activated protein kinase kinase 1 (MEK-1)-independent pathway. Furthermore, apoptosis in Ha-ras-transformed brown adipocytes is concurrent with an up-regulation in the expression of the pro-apoptotic protein Bcl-xS, the expression of the anti-apoptotic protein Bcl-2 being down-regulated. Finally, an association of Ras and Raf with phosphorylated Bcl-2 protein was demonstrated in immunoprecipitates from apoptotic cells. Thus, we propose a mechanism of apoptosis in Ha-ras-transformed adipocytes under serum deprivation involving Raf-1 association with phosphorylated Bcl-2, down-regulation of Bcl-2 expression, and up-regulation of Bcl-xS expression.
 ...
PMID:Activated Ha-ras induces apoptosis by association with phosphorylated Bcl-2 in a mitogen-activated protein kinase-independent manner. 1038 81

Raf-1 activation and Bcl-2 hyperphosphorylation following treatment with paclitaxel (Taxol) or other microtubule-active drugs is associated with mitotic arrest. Here we show that microtubule-active drugs do not activate the mitogen-activated protein kinase (MAPK) pathway in leukemia cells. PD98059, a MEK inhibitor, and SB202190, a p38 MAP kinase inhibitor, do not abrogate Bcl-2 phosphorylation nor apoptosis. Simultaneously with PARP cleavage, paclitaxel induces cleavage of Bcl-2 protein yielding a potentially pro-apoptotic 22 kDa product. In comparison, the stimulation of Raf-1 by phorbol ester (TPA) activates the MAPK pathway, causes MAPK-dependent p21WAF1/CIP1 induction, Rb dephosphorylation and growth arrest without Bcl-2 phosphorylation or apoptosis. Like TPA, cAMP induces p21WAF1/CIP1 but does not cause Bcl-2 phosphorylation. MEKK1 and Ras, upstream activators of JNK and ERK MAPK, also fail to induce Bcl-2 hyperphosphorylation. Although Lck tyrosine kinase has been recently implicated in Raf-1 activation during mitotic arrest, microtubule-active drugs induce Raf-1/Bcl-2 hyperphosphorylation and apoptosis in a Lck-deficient Jurkat cells. Therefore, microtubule-active drugs induce apoptosis which is associated with Raf-1 and Bcl-2 phosphorylation and Bcl-2 cleavage but is independent of the MAPK pathway. In contrast, TPA-activated MAPK pathway causes p21WAF1/CIP1-dependent growth arrest without apoptosis.
 ...
PMID:Mitogen-activated protein kinase pathway is dispensable for microtubule-active drug-induced Raf-1/Bcl-2 phosphorylation and apoptosis in leukemia cells. 1040 Apr 18

There is at present, much optimism about the possibility of finding selective anticancer drugs that will eliminate the cytotoxic side effects associated with conventional cancer chemotherapy. This hope is based on uncovering many novel molecular targets that are 'cancer-specific', which will allow the targeting of cancer cells while normal cells are spared. Thus far, encouraging results have been obtained with several of these novel agents at the preclinical level, and clinical trials have begun. These targets are involved at one level or more in tumor biology, including tumor cell proliferation, angiogenesis and metastasis. Novel targets for which advances are being made include the following: growth factor receptor tyrosine kinases such as the epidermal growth factor receptor and HER-2/neu (proliferation); the vascular endothelial growth factor receptor and the basic fibroblast growth factor receptor (angiogenesis); the oncogenic GTP-binding protein Ras (especially agents targeting Ras farnesylation, farnesyltransferase inhibitors) (proliferation); protein kinase C (proliferation and drug resistance); cyclin-dependent kinases (proliferation); and matrix metalloproteinases and angiogenin (angiogenesis and metastasis). Less explored, but potentially useful targets include the receptor tyrosine kinase platelet-derived growth factor receptor, mitogen-activated protein kinase cascade oncogenes such as Raf-1 and mitogen-activated protein kinase kinase, cell adhesion molecules such as integrins, anti-apoptosis proteins such as Bcl-2, MDM2 and survivin, and the cell life-span target telomerase.
 ...
PMID:Novel anticancer drug discovery. 1041 54

BAG-1 is an anti-apoptotic protein that interacts with Bcl-2, Bcl-XL, Hsp70/Hsc70, Raf-1 and numerous hormone or growth factor receptors. Recently, BAG-1 has been found to be overexpressed in a variety of human cancer cell lines and some tumors. However, the molecular mechanism of BAG-1 upregulation is still unclear. In this study, we cloned 0.9 kb of human genomic DNA, BGEV, 5' flanking the BAG-1 open reading frame. BGEV subcloned into a promoterless luciferase reporter vector conferred high promoter activity in various human cancer cell lines. Deletion analysis of this sequence localized the region of maximal BAG-1 promoter activity from nucleotide positions -353 to -54, upstream of the first start codon CTG. Sequence analysis of the BAG-1 promoter region showed the absence of a TATA box but identified a CCAAT box, several GC boxes, a CpG island and several transcriptional factor binding sites, which may be important in the regulation of BAG-1 transcription. Most importantly, functional characterization of the BAG-1 promoter in vivo demonstrated that gain-of-function p53 mutants derived from human tumors upregulated the transcription of BAG-1 RNA and the expression of a reporter gene from the BAG-1 promoter. These results indicated that we have isolated the functional constitutive BAG-1 promoter. Furthermore, the data suggested that overexpression of BAG-1 in some tumors may be due to upregulation of the human BAG-1 promoter by mutant p53.
 ...
PMID:Cloning and characterization of the human BAG-1 gene promoter: upregulation by tumor-derived p53 mutants. 1046 99

The proportions of aneuploid/polyploid versus euploid cells formed after treatment with spindle poisons like nocodazole are of course dependent on the relative survival of cells with numerical chromosome aberrations. This work aimed at studying the survival of polyploid cells formed after treatment with a nocodazole concentration sufficient to significantly decrease tubulin polymerization (0.1 microg/ml). First, normal primary lymphocytes were analysed and the following complementary chromosomal parameters were quantified: mitotic index, frequency of abnormal mitoses, polyploid metaphases and apoptotic cells. The results clearly indicate a positive correlation between abnormal mitotic figures, apoptosis and the induction of polyploidy. They therefore led to a single cell approach in which both apoptosis and polyploidy induction could be scored in the same cell. For this purpose, actively proliferating cells are required and two human leukaemic cell lines were used, KS (p53-positive) and K562 (p53-negative), which have a near-triploid karyotype. Cells were separated into an apoptotic and a viable fraction by means of annexin-V staining and flow cytometry. In KS, treatment with nocodazole induced a similar fraction of hexaploid cells in both the viable and apoptotic fraction, but no dodecaploid cells were ever observed. In contrast, a population of dodecaploid cells (essentially viable) was clearly observed in the K562 cell line. The results in KS, as compared with K562, confirm that wild-type p53 can prevent further cycling of polyploid cells by blocking rereplication. The most probable explanation for these data is that not only the mitotic spindle but also interphase microtubules are sensitive to nocodazole treatment. Our data thus strongly suggest that besides the G(1)/S checkpoint under the control of p53, the G(2)/M transition may be sensitive to depolymerization of microtubules, possibly under the control of Cdc2, Bcl-2, Raf-1 and/or Rho.
 ...
PMID:Induction of polyploidy and apoptosis after exposure to high concentrations of the spindle poison nocodazole. 1047 56

Drug resistance is a well recognized problem in cancer therapy. Despite the current dogma that drug resistance is always an obstacle for treatment, here I show that it provides opportunities for selective protection of non-resistant cells with killing of drug-resistant cancer cells. According to the proposed 'two-drug' strategy, the first drug should be ineffective against a target drug-resistant cell (ie the drug is a substrate of MRP or Pgp pumps). In addition, it must be cytostatic but not cytotoxic. The second drug, which is applied in sequence, must be a cycle-dependent apoptotic drug to which the target cell is not cross-resistant. Thus, low doses of adriamycin, etoposide and actinomycin D, used as the first drugs, were cytostatic to parental HL60 cells. Therefore, these drugs precluded Bcl-2/Raf-1 phosphorylation, PARP cleavage and cell death which are otherwise induced by paclitaxel, a mitosis-selective apoptotic drug for HL60 cells. In contrast, HL60/ADR cells which express MRP, a transporter which pumps out the first drugs from a cell, were insensitive to the first drugs and therefore readily underwent apoptosis following the second drug. This strategy also allowed a selective killing of HL60/TX cells which express MDR-1, with the only difference being that the second drug, paclitaxel, was substituted for epothilones, non-Pgp substrates. Lack of protection by the first drug, a Pgp substrate, resulted in HL60/TX killing by the second drug, whereas parental HL-60 cells were fully protected. Therefore, drug resistant cells can be selectively killed by a combination of drugs not killing sensitive cells. Lack of toxicity against normal cells will be clinically translated in reduction of adverse side-effects of chemotherapy against drug-resistant malignancies.
 ...
PMID:Drug-resistance enables selective killing of resistant leukemia cells: exploiting of drug resistance instead of reversal. 1060 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>