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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Apoptosis is a particular process that leads to the programmed cell death, and it has been a potentially therapeutic target of cancer. In this study, we evaluated the possible apoptotic effects of glycolic acid on human leukemia cell line (HL-60) in vitro. The morphological changes, cell viability, apoptosis induction, and caspase-3 activity were measured by phase microscopy, flow cytometry, and Western blot analysis. Morphological changes including shrinkage of cells were clearly demonstrated in HL-60 cells treated with increasing concentrations of glycolic acid. Cell viability was significantly affected by glycolic acid treatment in a dose- and time-dependent manner. In comparison to the control group, glycolic acid treatment had a profound effect in the induction of apoptosis by flow cytometric assays. In the cell cycle analysis, glycolic acid caused the increased percentage of cells in G2/M phase and the decreased expression of the cyclin A and cyclin B1, suggesting the induction of G2/M arrest of cell cycle by glycolic acid. Moreover, glycolic acid treatment promoted caspase-9 and -3 activity in a dose-dependent manner, but caspse-8 activity was not affected during the same process. Glycolic acid co-administrated with broad-spectrum caspase inhibitor, z-VAD-fmk, caspase-3 activity was blunted and apoptosis was also markedly blocked in HL-60 cells. In conclusion, glycolic acid-induced apoptosis in HL-60 cells may be through the activation of caspase-3. Future studies focusing on cell signaling and biological significance of glycolic acid-induced apoptosis would lead to exploring the mechanisms of chemotherapeutic potency of glycolic acid in human cancers.
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PMID:Effects of glycolic acid on the induction of apoptosis via caspase-3 activation in human leukemia cell line (HL-60). 1535 Jun 75

Therapy-related myeloid leukemia (t-AML) is a distinctive clinical syndrome occurring after exposure to chemotherapy (CT) or radiotherapy (RT). We studied 306 consecutive patients referred to the University of Chicago with cytogenetic analyses. Since 1972, 141 males and 165 females with a median age of 51 years (range: 3-83 years) at primary diagnosis and 58 years (range: 6-86 years) at secondary diagnosis were analyzed. Patients had received various cytotoxic agents including alkylating agents (240 patients, 78%) and topoisomerase II inhibitors (115 patients, 39%). One hundred and twenty-one (40%) had received CT alone, 43 (14%) had received RT alone, and 139 (45%) had received both modalities. At diagnosis of t-AML, 282 (92%) had clonal abnormalities involving chromosome 5 (n=63), chromosome 7 (n=85), both chromosomes 5 and 7 (n=66), recurring balanced rearrangements (n=31), or other clonal abnormalities (n=39); 24 had a normal karyotype. Abnormalities of chromosomes 5 and/or 7 accounted for 76% of all cases with an abnormal karyotype. Seventeen patients had developed t-AML after autologous stem cell transplantation, but no unique pattern of cytogenetic abnormalities was observed. Patients presenting with acute leukemia were more likely to have a balanced rearrangement than those presenting with myelodysplasia (28% versus 4%, p<0.0001). Shorter latency was observed for patients with balanced rearrangements (median: 28 months versus 67 months; p<0.0001). Median survival after diagnosis of t-AML was 8 months; survival at 5 years was less than 10%. To gain insights into the molecular basis of this disease, we performed gene expression profiling of CD34+ hematopoietic progenitor cells from t-AML patients. We found distinct subtypes of t-AML that have characteristic gene expression patterns. Common to each of the subgroups are gene expression patterns typical of arrested differentiation in early progenitor cells. Leukemias with a -5/del(5q) have a higher expression of genes involved in cell cycle control (CCNA2, CCNE2, CDC2), checkpoints (BUB1), or growth (MYC), and loss of expression of the gene encoding interferon consensus sequence-binding protein (ICSBP). A second subgroup of t-AML is characterized by down-regulation of transcription factors involved in early hematopoiesis (TAL1, GATA1, and EKLF) and overexpression of proteins involved in signaling pathways in myeloid cells (FLT3) and cell survival (BCL2). Establishing the molecular pathways involved in t-AML may facilitate the identification of selectively expressed genes that can be exploited for the development of targeted therapies.
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PMID:Therapy-related myeloid leukaemia: a model for leukemogenesis in humans. 1593 16

Variolin B (VAR-B) is a natural product isolated from the sponge Kirkpatrickia variolosa, found in Antarctica. VAR-B has been shown previously to possess potent pro-apoptotic activity. This study was undertaken to investigate the mechanism of action of chemically synthesised VAR-B and its analogue deoxy-variolin B (dVAR-B). In different human cancer cell lines both compounds inhibited colony formation, caused cell cycle perturbations and induced apoptosis at concentrations ranging from 0.1 to 2 microM. LoVo/Dx cells over-expressing Pgp were equally sensitive as the parental cell line to VAR-B and dVAR-B, indicating that variolins are not substrates of Pgp. Although variolins induced an increase in the levels of p53 with an increase in p21, their cytotoxicities did not appear to be dependent on p53 status as their potency was comparable in cells with wild-type p53, or in sub-lines with inactivated p53. Both VAR-B and dVAR-B prevent the cells from entering S phase, blocking cells in G1 and cause an accumulation of cells in G2. The apoptosis induced by VAR-B and dVAR-B occurs very rapidly in some cell lines (e.g., Jurkat leukaemia cells) and is already evident 4h after the beginning of treatment. Although intercalation of dVAR-B in DNA has been demonstrated, neither VAR-B nor dVAR-B produce detectable breaks in DNA. These results are consistent with the in vitro biochemical assays that also demonstrated that dVAR-B is not topoisomerase I or II poison. Instead, each of these variolins appears to inhibit cyclin-dependent kinases (CDKs) in the muM range. CDK1-cyclin B, CDK2-cyclin A and CDK2/cylin E complexes were inhibited in a range of concentrations lower than those required to inhibit the activity of CDK4/cyclin D or CDK7/cyclin H complexes. In conclusion, these variolins are a new class of CDK inhibitors that activate apoptosis in a p53-independent fashion and thus they may be effective against tumours with p53 mutations or deletions.
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PMID:Variolin B and its derivate deoxy-variolin B: new marine natural compounds with cyclin-dependent kinase inhibitor activity. 1618 79

MEF is an ETS-related transcription factor with strong transcriptional activating activity that affects hematopoietic stem cell behavior and is required for normal NK cell and NK T-cell development. The MEF (also known as ELF4) gene is repressed by several leukemia-associated fusion transcription factor proteins (PML-retinoic acid receptor alpha and AML1-ETO), but it is also activated by retroviral insertion in several cancer models. We have previously shown that cyclin A-dependent phosphorylation of MEF largely restricts its activity to the G(1) phase of the cell cycle; we now show that MEF is a short-lived protein whose expression level also peaks during late G(1) phase. Mutagenesis studies show that the rapid turnover of MEF in S phase is dependent on the specific phosphorylation of threonine 643 and serine 648 at the C terminus of MEF by cdk2 and on the Skp1/Cul1/F-box (SCF) E3 ubiquitin ligase complex SCF(Skp2), which targets MEF for ubiquitination and proteolysis. Overexpression of MEF drives cells through the G(1)/S transition, thereby promoting cell proliferation. The tight regulation of MEF levels during the cell cycle contributes to its effects on regulating cell cycle entry and cell proliferation.
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PMID:The ETS protein MEF is regulated by phosphorylation-dependent proteolysis via the protein-ubiquitin ligase SCFSkp2. 1658 86

The human T-lymphotropic virus type 1 (HTLV-1) Tax binds the anaphase promoting complex (APC) and activates it ahead of schedule. Here, we show that APC activation by Tax induces rapid senescence (tax-IRS) independently of p53 and pRB. In response to tax, cyclin A, cyclin B1, securin, and Skp2 becomes polyubiquitinated and degraded starting in S phase. This is followed by a surge in p21(CIP1/WAF1) and p27(KIP1) in mid to late S and G2/M leading to a permanent G1 arrest. Tax-positive HTLV-1-transformed T-cell lines express elevated levels of p21(CIP1/WAF1), but low levels of p27(KIP1). Finally, Tax can be stably expressed in p27(KIP1)-null NIH3T3 cells. These results indicate that APC activation by Tax causes inactivation of SCF(Skp2) and stabilization of p21(CIP1/WAF1) and p27(KIP1). The build-up of p21(CIP1/WAF1) and especially p27(KIP1) commits cells to senescence. Evading tax-IRS through a loss of p27(KIP1) function is likely to be critical for cell transformation by Tax and development of adult T-cell leukemia after HTLV-1 infection. Finally, activation of APC ahead of schedule may be exploited to arrest cancer cell growth.
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PMID:Activation of the anaphase promoting complex by HTLV-1 tax leads to senescence. 1660 96

Adaphostin (NSC680410), a small molecule congener of tyrphostin AG957, has been demonstrated previously to have significant anti-proliferative effects in several leukemia models. However, this effect of adaphostin in adherent cells/solid tumor models has not been examined. In this study, we investigated the anti-proliferative effects of adaphostin in the human prostate cancer cell line PC-3. Specifically, we explored the potential molecular mechanism(s) by which adaphostin elicits its anti-proliferative effect(s). We demonstrate that adaphostin inhibits the proliferation of PC-3 cells by inducing a G(1) phase cell cycle arrest. This adaphostin-induced G(1) arrest was associated with an increase in the expression of p21 and p27 and a decrease in the expression of G(1)-specific cyclins (cyclin A, D1, and D3) and cyclin-dependent kinases 4 and 6. Consequently, a dramatic decrease in the phosphorylation of retinoblastoma protein was also observed. Additionally, we found that adaphostin treatment induced a decrease in the phosphorylation of nucleophosmin, a major nuclear phosphoprotein, and that this decreased phosphorylation was a result of the p21- and p27-mediated inactivation of cyclin E-cyclin-dependent kinase 2 complex kinase activity. Furthermore, we have determined that the adaphostin-mediated cell cycle arrest of PC-3 cells is dependent upon activation of the p38 MAPK. We also demonstrate that the hepatocyte growth factor receptor-c-Met is involved in the adaphostin-mediated signaling events that regulate p38 MAPK. Taken together, these results identify for the first time a signaling cascade of adaphostin-mediated G(1) phase-specific cell cycle arrest in PC-3 cells. These findings suggest that the tyrphostin member has a broader spectrum of activity than originally predicted.
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PMID:Molecular mechanism of adaphostin-mediated G1 arrest in prostate cancer (PC-3) cells: signaling events mediated by hepatocyte growth factor receptor, c-Met, and p38 MAPK pathways. 1695 84

Chronic lymphocytic leukemia (CLL) B-cells are hyporesponsive to many proliferative signals that induce activation of normal B-lymphocytes. However, a heterogeneous response has recently been observed with immunostimulatory CpG-oligodeoxynucleotides (CpG ODN). We now show that CpG ODN induce proliferation mainly in CLL B-cells from patients with progressive disease and unmutated immunoglobulin V(H) genes, whereas G(1)/S cell cycle arrest and apoptosis are induced in leukemic B-cells from stable/V(H) mutated CLL. Examination of early signaling events demonstrated that all CLL B-cells respond to CpG ODN stimulation by degradation of the NF-kappaB inhibitor IkappaB and activation of the Akt, ERK, JNK and p38 MAPK kinases, but the magnitude and duration of the signaling response was greater in the proliferating cases. Pharmacological inhibition of these pathways showed that simultaneous activation of Akt, ERK and JNK is required for cell cycle progression and proliferation. Conversely, introduction of constitutively active Akt in nonproliferating CLL B-cells resulted in induction of cyclin A following CpG ODN stimulation, indicating that increased Akt activation is sufficient to overcome the hyporesponsiveness of these cells to proliferative signals. Thus, the magnitude of Akt signaling may determine the distinct responses observed in leukemic B-cells belonging to the different prognostic subgroups.
Leukemia 2007 Jan
PMID:The Akt signaling pathway determines the different proliferative capacity of chronic lymphocytic leukemia B-cells from patients with progressive and stable disease. 1765 15

Cardiotoxin III (CTX III) is a basic polypeptide of 60-amino acid residues isolated from Naja naja atra venom, exerts its anti-proliferative activity in human leukemia K562 cells. In the present study, the expression of mRNAs and proteins related to cell cycle and apoptosis in human leukemia K562 cells induced by CTX III was investigated by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. Flow cytometric analysis revealed that CTX III resulted in G2/M phase arrest in the cell cycle progression, which was associated with a marked decrease in the mRNA and protein expressions of cyclin A, cyclin B1, and Cdk 2, with no detectable changes in the levels of Cdk 1, cyclin D1, and cyclin E. Moreover, the increase in apoptosis was associated with the Bax gene and protein levels significantly increased as treatment durations of CTX III increased, while the Bcl-2 mRNA and protein levels exhibited no changes. We also observed that caspase-9 and caspase-3 genes remained unchanged up to 12 h with 2 microg/ml CTX III. These molecular alterations provide an insight into CTX III-caused growth inhibition, G2/M arrest, and apoptotic death of K562 cells.
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PMID:Effects of cardiotoxin III on expression of genes and proteins related to G2/M arrest and apoptosis in K562 cells. 1714 43

The relationship between apoptosis and the cell cycle remains unclear. In the present study we have investigated the relationship between cell cycle progression and the activation of caspases (caspase-3 and caspase-8) in Fas (CD95)-mediated apoptosis in asynchronously growing leukemia cells. We found that cells expressing the active form of caspase-3 were cyclin A/B1 and Ki-67 negative but cyclin E positive, whereas expression of the active form of caspase-8 was detected in cyclin A/B1/E-negative and Ki-67-negative cells. In addition, both the activation of caspases and Fas-mediated apoptosis were completely abolished when leukemia cells were arrested in early G1 phase. Using post-sorting western blot analysis, we demonstrated that caspase-3 and caspase-8 were activated in p27-negative cells. These results suggest that caspase-3 would be activated in cells entering into late G1 or early S phase, and caspase-8 would be activated in middle or late G1 phase. The speed of cell cycle progression from G1 to S phase might be influential in the speed of caspase activation and induction of Fas-mediated apoptosis.
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PMID:Cell cycle dependency of caspase activation in Fas-induced apoptosis in leukemia cells. 1756 74

Cyclin A(2) plays critical role in DNA replication, transcription, and cell cycle regulation. Its overexpression has been detected and related to many types of cancers including leukemia, suggesting that suppression of cyclin A(2) would be an attractive strategy to prevent tumor progression. Herein, we apply functionalized single wall carbon nanotubes (f-SWNTs) to carry small interfering RNA (siRNA) into K562 cells and determine whether inhibition of cyclin A(2) would be a potential therapeutic target for chronic myelogenous leukemia. The results show functionalized SWNTs can facilitate the coupling of siRNA specifically targeting human cyclin A(2) to form cyclin A(2) siRNA-f-SWNTs complexes. These functionalized SWNTs readily enter K562 cells, resulting in suppression of cyclin A(2) expression. We demonstrate that depletion of cyclin A(2) in this manner inhibits cell proliferation and promotes apoptosis, and cyclin A(2) can serve as a novel therapeutic target. siRNA against cyclin A(2) delivered by functionalized single wall carbon nanotubes may be a useful therapeutic strategy for chronic myelogenous leukemia cells. This would provide new insights on additional therapeutic options for chronic myelogenous leukemia beyond chemotherapy in light of increasing multidrug resistance.
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PMID:Targeted RNA interference of cyclin A2 mediated by functionalized single-walled carbon nanotubes induces proliferation arrest and apoptosis in chronic myelogenous leukemia K562 cells. 1828 53


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