Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The loss of p53 function is a key event in tumorigenesis. Inactivation of p53 in primary tumors and cell lines is mediated by several molecular mechanisms, including deletions and rearrangements. However, generation of a p53 fusion gene has not yet been reported. Here we report a novel p53/an autosomal homolog of the fragile X mental retardation (FXR2) chimeric gene generated by an interstitial deletion. Western blot analyses have shown that the p53/FXR2 protein is indeed expressed in a Down syndrome-related acute megakaryoblastic leukemia cell line, CMK11-5 cells. To investigate the properties of the p53/FXR2 protein, we observed its subcellular localization. Flag-tagged expression vectors were transfected into COS-7 cells and the proteins were stained with an anti-Flag antibody. The p53/FXR2 protein was expressed at high levels in the cytoplasm, whereas wild-type p53 and FXR2 were localized primarily in the nucleus and in the periphery of the nucleus, respectively. Treatment with a topoisomerase II inhibitor, VP16, failed to induce expression of a p53 target gene, the cyclin-dependent kinase inhibitor p21(WAF-1/CIP1), in CMK11-5 cells, and transient transfection analysis showed that the p53/FXR2 protein failed to transactivate the p21(WAF-1/CIP1) promoter. These results suggest that the p53/FXR2 fusion protein lacks the ability of wild-type p53 to function as a transcription factor. The p53/FXR2 gene is the first reported p53 fusion gene.
 ...
PMID:Cloning and characterization of the novel chimeric gene p53/FXR2 in the acute megakaryoblastic leukemia cell line CMK11-5. 1677 63

The interferon inducible protein TRIM22 has been identified as a p53 target gene, with possible involvement in proliferation and differentiation of leukaemia cells. Here, the expression levels of TRIM22 during haematopoietic differentiation are characterised. Expression of TRIM22 correlates inversely to differentiation, as TRIM22 is highly expressed in CD34(+) human bone marrow progenitor cells, but declines in mature populations. The erythroid lineage appears as a special case, as TRIM22 expression shows an extreme decrease during late erythroid maturation and is completely undetectable in nucleated erythroid populations in contrast to other lineages. In conclusion, our data could suggest lineage-specific roles for TRIM22 during haematopoietic differentiation.
 ...
PMID:Expression of the IFN-inducible p53-target gene TRIM22 is down-regulated during erythroid differentiation of human bone marrow. 1725 75

Apoptosis resistance is crucially involved in cancer development and progression, represents the leading cause for failure of anticancer therapy and is caused, for example, by downregulation of proapoptotic intracellular signaling molecules such as caspase-8. We found that the cytotoxic drugs methotrexate (MTX) and 5-fluorouracil (5-FU) were both able to sensitize resistant tumor cells for induction of apoptosis by p53-mediated upregulation of caspase-8. Increase in caspase-8 messenger RNA and protein expression disabled tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced proliferation and restored sensitivity toward TRAIL-induced apoptosis which was inhibited by transfection of p53 decoy oligonucleotides, p53 shRNA and caspase-8 shRNA. Upregulation of caspase-8 and sensitization toward TRAIL-induced apoptosis was found both in a broad panel of tumor cell lines with downregulated caspase-8 and in TRAIL-resistant primary tumor cells of children with acute leukemia. Taken together, we have identified caspase-8 as an important p53 target gene regulated by cytotoxic drugs. These findings highlight a new drug-induced modulation of physiological apoptosis pathways, which may be involved in successful anticancer therapy using MTX and 5-FU in leukemia and solid tumors over decades.
 ...
PMID:Cytotoxic drug-induced, p53-mediated upregulation of caspase-8 in tumor cells. 1763 40

Human T-lymphotropic virus type 1 (HTLV-1) is the etiologic agent for adult T-cell leukemia. The HTLV-1-encoded protein Tax transactivates the viral long terminal repeat and plays a critical role in virus replication and transformation. Previous work from our laboratory demonstrated that coactivator-associated arginine methytransferase 1, a protein arginine methytransferase, was important for Tax-mediated transactivation. To further investigate the role of methyltransferases in viral transcription, we utilized adenosine-2,3-dialdehyde (AdOx), an adenosine analog and S-adenosylmethionine-dependent methyltransferase inhibitor. The addition of AdOx decreased Tax transactivation in C81, Hut102, and MT-2 cells. Unexpectedly, we found that AdOx potently inhibited the growth of HTLV-1-transformed cells. Further investigation revealed that AdOx inhibited the Tax-activated NF-kappaB pathway, resulting in reactivation of p53 and induction of p53 target genes. Analysis of the NF-kappaB pathway demonstrated that AdOx treatment resulted in degradation of the IkappaB kinase complex and inhibition of NF-kappaB through stabilization of the NF-kappaB inhibitor IkappaBalpha. Our data further demonstrated that AdOx induced G(2)/M cell cycle arrest and cell death in HTLV-1-transformed but not control lymphocytes. These studies demonstrate that protein methylation plays an important role in NF-kappaB activation and survival of HTLV-1-transformed cells.
 ...
PMID:Inhibition of methyltransferases results in induction of g2/m checkpoint and programmed cell death in human T-lymphotropic virus type 1-transformed cells. 1794 56

The transcription factor PU.1 is essential for terminal myeloid differentiation, B- and T-cell development, erythropoiesis and hematopoietic stem cell maintenance. PU.1 functions as oncogene in Friend virus-induced erythroleukemia and as tumor suppressor in acute myeloid leukemias. Moreover, Friend virus-induced erythroleukemia requires maintenance of PU.1 expression and the disruption of p53 function greatly accelerates disease progression. It has been hypothesized that p53-mediated expression of the p21(Cip1) cell cycle inhibitor during differentiation of pre-erythroleukemia cells promotes selection against p53 function. In addition to the blockage of erythroblast differentiation provided by increased levels of PU.1, we propose that PU.1 alters p53 function. We demonstrate that PU.1 reduces the transcriptional activity of the p53 tumor suppressor family and thus inhibits activation of genes important for cell cycle regulation and apoptosis. Inhibition is mediated through binding of PU.1 to the DNA-binding and/or oligomerization domains of p53/p73 proteins. Lastly, knocking down endogenous PU.1 in p53 wild-type REH B-cell precursor leukemia cells leads to increased expression of the p53 target p21(Cip1).
 ...
PMID:PU.1 binding to the p53 family of tumor suppressors impairs their transcriptional activity. 1819 90

Inhibitors of the MDM2-p53 interaction are actively being developed as anti-cancer agents. Drug-induced interference with the MDM2 E3 ligase function or with MDM2 protein-protein interactions abrogates tonic suppression and destruction of the p53 protein; consequently, p53 steady state levels rise resulting in the induction of p53-dependent anti-proliferative and pro-apoptotic genes. Some cancerous cells harboring wild type p53 respond to MDM2 inhibitor-induced elevated p53 protein levels with apoptotic cell death while non-malignant cells, for poorly understood reasons, appear relatively resistant. Deciphering the mechanisms of resistance or susceptibility to MDM2 inhibitor-induced cancer cell death is of significant importance for the clinical development and applications of MDM2 inhibitory compounds and serves to illuminate aspects of MDM2 and p53 biology. Using data from ex vivo MDM2 inhibitor treatment of a large cohort of molecularly highly characterized CLL cases, we were able to demonstrate the central role of p53 status as a determinant of resistance in this common leukemia. In the context of these experimental findings, we summarize pertinent knowledge of the biology of p53, MDM2, p53 target genes and MDM2 binding proteins. Finally, using data from a large SNP-array-based high-density genomic profiling study in CLL, we summarize the genomic copy number and allele status for important p53 effector genes as well as for MDM2 binding/target proteins, thus demonstrating the power of high resolution genomic analysis in support of targeted drug development.
 ...
PMID:The pre-clinical development of MDM2 inhibitors in chronic lymphocytic leukemia uncovers a central role for p53 status in sensitivity to MDM2 inhibitor-mediated apoptosis. 1841 49

The cellular response to Nutlin-3, a small-molecule inhibitor of the p53 repressor MDM2, varies widely among human cancer-derived cell types. Whereas HCT116 colorectal carcinoma cells display sustained cell cycle arrest, BV173 leukemia cells undergo rapid apoptosis and other cell lines show an intermediate response. We found that the expression of the p53 target genes p21, 14-3-3sigma and the microRNA miR-34a correlates tightly with the cell fate choice adopted. All three genes were strongly induced in arresting cells, but silenced in cells undergoing Nutlin-3-induced apoptosis. In contrast, key apoptotic p53 target genes were equally expressed in arresting and apoptotic cells. Interestingly, we establish that miR-34a cooperates with p21 and 14-3-3sigma to override the apoptotic signals generated by p53 activation. Strikingly, p53 binding to chromatin and p53-mediated recruitment of certain coactivators to all three target loci does not vary among cell types. Instead, the cell type-specific silencing of these genes is due to enhanced p21 mRNA degradation, 14-3-3sigma promoter DNA methylation and reduced processing of the miR-34a primary transcript. Thus, p53-independent events regulating expression of protein-coding genes and microRNAs within the network can define the cellular outcome of p53 activation.
 ...
PMID:Multiple p53-independent gene silencing mechanisms define the cellular response to p53 activation. 1867 10

Mantle cell lymphoma (MCL) is a clinically aggressive B-cell non-Hodgkin lymphoma characterized by the t(11;14)(q13;q32) and overexpression of cyclin D1. A high proportion of MCL tumors harbor wild-type (wt) and potentially functional p53 gene. We show here that stabilization and activation of wt-p53 using a recently developed potent MDM2 inhibitor, nutlin 3A, results in significant p53-dependent G1-S cell cycle arrest and apoptosis in MCL cells through regulation of p53 target genes. As mTOR signaling is activated in MCL and may control cyclin D1 levels, we show that p53 activation may downregulate the AKT/mTOR pathway through a mechanism involving AMP kinase (AMPK). Despite the non-genotoxic mode of nutlin 3A treatment, we show evidence that stabilization of p53 is associated with its phosphorylation at serine 15 residue and activation of AMPK. Stimulation of AMPK kinase activity using AICAR inhibits phosphorylation of critical downstream effectors of mTOR signaling, such as 4E-BP1 and rpS6. Pharmacologic inhibition of AMPK using compound C in nutlin-3A-treated MCL cells harboring wt-p53 did not affect the level of (ser15)p-p53, suggesting that the (ser15)p-p53 --> AMPK is the direction involved in the p53/AMPK/mTOR cross talk. These data establish a p53 --> AMPK --> mTOR mechanism in MCL and uncover a novel biologic effect of potent MDM2 inhibitors in preclinical models of MCL.
Leukemia 2009 Apr
PMID:Stabilization and activation of p53 downregulates mTOR signaling through AMPK in mantle cell lymphoma. 1922 36

Philadelphia chromosome positive chronic myeloid leukemia has a progressive course starting in a benign phase and terminating in a blastic phase. In this study, we show that human homolog double minute 2 (HDM2) inhibition, with MI-219-a novel compound, and consequently p53 stabilization induce chronic myeloid leukemia (CML) blast crisis cells to undergo apoptosis regardless of the presence of the T315I mutation in the BCR-ABL kinase domain. The response to MI-219 is associated with the downregulation of c-Myc and the induction of p21(WAF1). The p53 target and pro-apoptotic proteins PUMA, Noxa and Bax are induced, whereas full length Bid protein decreases with increased activity of pro-apoptotic cleaved Bid, and decrease of Mcl-1 is observed by increased caspase activity. CD95/FAS (FAS antigen) receptor is also induced by MI-219, indicating that both intrinsic and extrinsic apoptotic responses are transcriptionally induced. In addition, p53 protein accumulates in the mitochondrial fraction of treated cells involved in transcription-independent induction of apoptosis. We conclude that HDM-2 inhibition with MI-219 effectively induces p53-dependent apoptosis in most blast crisis CML cells, with or without BCR-ABL mutation(s).
Leukemia 2011 May
PMID:p53 stabilization induces apoptosis in chronic myeloid leukemia blast crisis cells. 2135 May 58

The human T-cell leukemia cell line MOLT-4 is highly radiosensitive, and thus it is often used as a model of p53-dependent radiation-induced apoptosis. Two branches of the p53-mediated apoptotic pathway are reported: "transcription-dependent" and "transcription-independent." However, the relative contribution of each in different types of cells is not yet clearly defined. Moreover, recent studies have shown that the codon 72 polymorphic variants of p53 show different sensitivities to apoptosis signals. The Arg72 variant has a more potent apoptosis-inducing activity in mitochondria than the Pro72 variant. Here, we initially investigated the codon 72 polymorphism of p53 in MOLT-4 cells. Analysis of the p53 exon 4 genomic DNA sequence, which includes codon 72, revealed that MOLT-4 cells are homozygous for the allele encoding Arg72. We next investigated the involvement of the transcription-independent function of p53 using an RNA synthesis inhibitor, actinomycin D (ActD), and a protein synthesis inhibitor, cycloheximide (CHX), and found that the apoptosis was suppressed by CHX but not by ActD. We also revealed that the suppressive effect of CHX on apoptosis was specifically mediated by p53, using a p53-knockdown MOLT-4 transfectant. Furthermore, the suppressive effect of CHX on apoptosis was highly correlated with the suppression of p53 protein accumulation, and less correlated with the suppression of p53 target genes expression. These results indicated that p53 transactivation is not necessary to induce apoptosis, and that p53 protein accumulation itself is both necessary and sufficient to do so.
 ...
PMID:Cycloheximide suppresses radiation-induced apoptosis in MOLT-4 cells with Arg72 variant of p53 through translational inhibition of p53 accumulation. 2146 39


<< Previous 1 2 3 Next >>