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

Inhibition of cyclin-dependent kinases (CDKs) is a novel strategy in the therapy of human malignancies. The pharmacological CDK inhibitors representing a few distinct classes of compounds exert different target specificity. Considering the fact that dividing and quiescent cells differ in their CDK activity and in the pattern of their expression, one might expect that anti-proliferative efficiency of the pharmacological CDK inhibitors would depend on the mitotic index of treated cells. The present article shows that olomoucine (OLO), a weak CDK2 inhibitor has new, unexpected activity. At concentrations up to 100 microM OLO did not inhibit proliferation of normal human cells, but arrested growth of human HL-60 leukemia cells. The anti-proliferative effect of OLO was clearly weaker than that of roscovitine (ROSC). Surprisingly, OLO at low doses strongly up-regulated a cellular protein with approximately 65 kDa in normal, but not in immortalized and cancer cells. By mass spectrometric analysis CLIMP-63, a cytoskeleton-linking membrane protein was identified as the major component of the up-regulated protein band. These results were subsequently confirmed by immunoblotting. Further experiments revealed that OLO, but not ROSC, strongly up-regulates CLIMP-63 in a dose- and time-dependent manner solely in senescent cells.
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PMID:A new, unexpected action of olomoucine, a CDK inhibitor, on normal human cells: up-regulation of CLIMP-63, a cytoskeleton-linking membrane protein. 1797 94

Mcl-1 is an antiapoptotic Bcl-2 family member, whose degradation is supposedly required for the induction of apoptosis. However, histone deacetylase inhibitors (HDACi) induce apoptosis primarily through the Bak/Mcl-1/Noxa and Bim pathways without decreasing Mcl-1. To investigate this discrepancy, we examined the role of Mcl-1 on HDACi-mediated apoptosis. Inhibition of either class I or class II HDAC by selective HDACi caused an upregulation of Mcl-1 mRNA and protein. Downregulation of Mcl-1 by three structurally unrelated cyclin-dependent kinase inhibitors potentiated HDACi-mediated apoptosis in primary chronic lymphocytic leukemic (CLL) cells and K562 cells. Sensitivity to HDACi-induced apoptosis was increased approximately 10-fold by the cyclin-dependent kinase inhibitors. Nanomolar concentrations of HDACi, approximately 300-fold lower than that required to induce apoptosis alone, sensitized cells to TRAIL, emphasizing that the mechanism(s) whereby HDACi induce apoptosis is clearly distinct from those by which they sensitize to TRAIL. Furthermore, knockdown of Mcl-1-potentiated HDACi-mediated apoptosis in K562 cells. Thus, HDACi-mediated Mcl-1 upregulation plays an important antiapoptotic regulatory role in limiting the efficacy of HDACi-induced apoptosis, which can be overcome by combination with an agent that downregulates Mcl-1. Thus, a clinical trial in some cancers is warranted using a combination of an HDACi with agents that downregulate Mcl-1.
Leukemia 2008 Apr
PMID:Downregulation of Mcl-1 potentiates HDACi-mediated apoptosis in leukemic cells. 1823 21

Human T-cell leukemia virus type I (HTLV-I) can infect a variety of cell types, so the cause of T-cell-specific oncogenesis remains to be elucidated. The trans-activator protein Tax of HTLV-I can promote cell-cycle progression in resting T cells along with induction of cyclin D2 and cyclin-dependent kinase (cdk6) gene expression. Here, we found that Tax cannot induce cell-cycle progression in resting fibroblasts and analysed the molecular basis of the cell-type specificity. Tax activated cyclin D2 and cdk6 promoters in T cells, but not in fibroblasts, depending on its ability to activate the transcription factor nuclear factor (NF)-kappaB. Expression of cyclin D2 and CDK6 activated the transcription factor E2F, which is essential for cell-cycle progression, in both T cells and fibroblasts. Short-hairpin RNA (shRNA)-mediated inhibition of cyclin D2 and CDK6 induction suppressed Tax-induced activation of E2F in T cells. Finally, shRNA-mediated downregulation of NF-kappaB p65 or p100 expression reduced Tax-induced activation of cyclin D2 and/or cdk6 promoters and cell-cycle progression in T cells. These results indicate that Tax-induced cell-cycle progression in T cells is mediated, at least in part, through cell-type-specific activation of the cyclin D2 and cdk6 genes through NF-kappaB and may be important for the cell-type-specific oncogenesis.
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PMID:Activation of the cyclin D2 and cdk6 genes through NF-kappaB is critical for cell-cycle progression induced by HTLV-I Tax. 1850 28

Wogonin, a natural monoflavonoid, has been shown to have tumor therapeutic potential in vitro and in vivo. Recently many studies have focused on the induction of apoptosis of tumor cells by wogonin. In this study, we found that wogonin could induce differentiation and G1 phase arrest of human U-937 leukemia cells. The growth of U-937 cells incubated with wogonin was inhibited in a time- and concentration-dependent manner. After treatment with wogonin, U-937 cells exhibited the characteristics of mature granulocytes, such as increased cytoplasmic-to-nuclear ratio, enhanced prominence of cytoplasmic granules, membrane ruffling, a higher NBT-reducing ability, and an increased expression of CD11b. Moreover, wogonin could induce G1 phase arrest and influenced the expression of associated proteins. For example, the expression of phorsphorylated protein kinase C (PKC) delta, p21 increased, while that of cyclin D1/cyclin-dependent kinase (CDK) 4, p-Rb decreased. The upregulation of p21 could be reversed by rottlerin, an inhibitor of PKCdelta. Taken together, wogonin induced U-937 cells to undergo granulocytic differentiation and G1 phase arrest via PKCdelta phosphorylation-induced upregulation of p21 proteins.
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PMID:Wogonin induced differentiation and G1 phase arrest of human U-937 leukemia cells via PKCdelta phosphorylation. 1857 79

Inhibition of differentiation has been proposed as an important mechanism for Myc-induced tumorigenesis, but the mechanisms involved are unclear. We have established a genetically defined differentiation model in human leukemia K562 cells by conditional expression of the cyclin-dependent kinase (Cdk) inhibitor p27 (inducible by Zn(2+)) and Myc (activatable by 4-hydroxy-tamoxifen). Induction of p27 resulted in erythroid differentiation, accompanied by Cdk inhibition and G(1) arrest. Interestingly, activation of Myc inhibited p27-mediated erythroid differentiation without affecting p27-mediated proliferation arrest. Microarray-based gene expression indicated that, in the presence of p27, Myc blocked the upregulation of several erythroid-cell-specific genes, including NFE2, JUNB, and GATA1 (transcription factors with a pivotal role in erythropoiesis). Moreover, Myc also blocked the upregulation of Mad1, a transcriptional antagonist of Myc that is able to induce erythroid differentiation. Cotransfection experiments demonstrated that Myc-mediated inhibition of differentiation is partly dependent on the repression of Mad1 and GATA1. In conclusion, this model demonstrates that Myc-mediated inhibition of differentiation depends on the regulation of a specific gene program, whereas it is independent of p27-mediated cell cycle arrest. Our results support the hypothesis that differentiation inhibition is an important Myc tumorigenic mechanism that is independent of cell proliferation.
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PMID:Myc inhibits p27-induced erythroid differentiation of leukemia cells by repressing erythroid master genes without reversing p27-mediated cell cycle arrest. 1883 34

Chronic lymphoid leukemias include well defined mature B-cell and T-cell neoplasms with diverse natural history and specific morphological, immunophenotypic and molecular characteristics. The most common adult leukemia in the Western world is chronic lymphocytic leukemia (CLL). Rarer indolent lymphoid leukemias include prolymphocytic leukemia, hairy cell leukemia, large granular lymphocyte leukemia and T-cell leukemia/lymphoma. Recently, several new agents have been explored and have shown promise in CLL treatment. Novel therapies are being evaluated both in pre-clinical studies and in early clinical trials. These treatments include new purine nucleoside analogs, antisense oligonucleotides, agents targeting the antiapoptotic Bcl-2 family of proteins, receptors involved in mediation of survival signals from the microenvironment, cyclin-dependent kinase inhibitors, protein kinase C inhibitors, tyrosine kinase inhibitors, immunomodulating drugs, new monoclonal antibodies and other agents. At present, available therapies are only partially efficient and there is an obvious need to develop better strategies and new, more specific and active drugs. This review will focus on agents currently being explored in preclinical studies and in early clinical trials.
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PMID:Novel drugs for chronic lymphoid leukemias: mechanism of action and therapeutic activity. 1951 88

Previously, we demonstrated that magnolol isolated from the bark of Magnolia officinalis has anticancer activity in colon, hepatoma, and leukemia cell lines. In this study, we show that magnolol concentration dependently (0-40 microM) decreased the cell number in a cultured human glioblastoma cancer cell line (U373) and arrested the cells at the G0/G1 phase of the cell cycle. Magnolol treatment decreased the protein levels of cyclins A and D1 and increased p21/Cip1, but not cyclins B and D3, cyclin-dependent kinase (CDK)2, CDK4, CDC25C, Weel, p27/Kip1, and p53. The CDK2-p21/Cip1 complex was increased, and the CDK2 kinase activity was decreased in the magnolol-treated U373. Pretreatment of U373 with p21/Cip1 specific antisense oligodeoxynucleotide prevented the magnolol-induced increase of p21/Cip1 protein levels and the decrease of DNA synthesis. Magnolol at a concentration of 100 microM induced DNA fragmentation in U373. Our findings suggest the potential applications of magnolol in the treatment of human brain cancers.
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PMID:Magnolol inhibits human glioblastoma cell proliferation through upregulation of p21/Cip1. 1964 6

We isolated two phytochemical lignans, schisandrin and schisandrin C, from Schizandra chinensis Baill and investigated their anti-cancer effects in human leukemia U937 cells. Schisandrin C inhibited cell growth in a dose-dependent manner, which was associated with the induction of G1 arrest of the cell cycle and apoptosis; schisandrin did not inhibit growth. Schisandrin C induced G1 arrest was correlated with down-regulation of cyclin D1, cyclin E, cyclin-dependent kinase (Cdk) 4 and E2Fs expression, inhibition of phosphorylation of retinoblastoma protein (pRB), and up-regulation of the Cdk inhibitor p21(WAF1/CIP1). In addition, schisandrin C-induced apoptosis was associated with down-regulation of expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, proteolytic activation of caspase-3 and -9, and a concomitant degradation of poly(ADP-ribose) polymerase (PARP). Furthermore, schisandrin C-induced apoptosis was significantly inhibited by a caspase-3 specific inhibitor z-DEVD-fmk, indicating an important role for caspase-3 in the schisandrin C mechanism. In summary, growth inhibition by schisandrin C is related to cell cycle arrest at G1 and induction of caspase-3-dependent apoptosis in U937 cells; these findings suggest that schisandrin C may be a useful chemotherapeutic agent.
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PMID:Induction of G1 arrest and apoptosis by schisandrin C isolated from Schizandra chinensis Baill in human leukemia U937 cells. 1972 90

Linalool, a natural small molecule monoterpene, has been shown to have anti-tumor activity against several human tumor cell lines in vitro; however, the anti-leukemia spectrum and molecular mechanisms inhibiting tumor cell growth are not fully understood. In the present study, we demonstrated that linalool preferentially induced growth arrest and apoptosis of a variety of human leukemia cells, but spared normal hematopoietic cells. Treatment of leukemia cells by linalool for 12h led to strong activation of p53, cyclin-dependent kinase inhibitors (CDKIs), GADD45alpha, c-jun and phosphorylated-JNK, suggesting that linalool-induced apoptosis might be associated with activation of p53 and CDKIs. The findings here warrant further investigation of this class of natural product as lead compound for developing novel therapeutic agents for leukemia.
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PMID:Linalool preferentially induces robust apoptosis of a variety of leukemia cells via upregulating p53 and cyclin-dependent kinase inhibitors. 1992 62

An elevated level of nucleophosmin (NPM) is often found in actively proliferative cells including human tumors. To identify the regulatory role for NPM phosphorylation in proliferation and cell cycle control, a series of mutants targeting the consensus cyclin-dependent kinase (CDK) phosphorylation sites was created to mimic or abrogate either single-site or multi-site phosphorylation. Simultaneous inactivation of two CDK phosphorylation sites at Ser10 and Ser70 (NPM-AA) induced G(2)/M cell cycle arrest, phosphorylation of Cdk1 at Tyr15 (Cdc2(Tyr15)) and increased cytoplasmic accumulation of Cdc25C. Strikingly, stress-induced Cdk1(Tyr15) and Cdc25C sequestration was suppressed by expression of a phosphomimetic NPM mutant created on the same CDK sites (S10E/S70E, NPM-EE). Further analysis revealed that phosphorylation of NPM at both Ser10 and Ser70 was required for proper interaction between Cdk1 and Cdc25C. Moreover, NPM-EE directly bound to Cdc25C and prevented phosphorylation of Cdc25C at Ser216 during mitosis. Finally, NPM-EE overrided stress-induced G(2)/M arrest and increased leukemia blasts in a NOD/SCID xenograft model. Thus, these findings reveal a novel function of NPM on regulation of cell cycle progression, in which phosphorylation of NPM controls cell cycle progression at G(2)/M transition through modulation of Cdk1 and Cdc25C activities.
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PMID:NPM phosphorylation stimulates Cdk1, overrides G2/M checkpoint and increases leukemic blasts in mice. 1993 6


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