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)

We have recently shown, using antisense strategy, that the RII beta regulatory subunit of cAMP-dependent protein kinase is essential for cAMP-induced growth inhibition and differentiation of HL-60 human leukemia cells. We constructed a retroviral vector for RII beta (MT-RII beta) by inserting human RII beta complementary DNA into the OT1521 retroviral vector plasmid that contains an internal mouse metallothionein-1 promoter and a neomycin resistance gene. The PA317 packaging cell line was then transfected with MT-RII beta plasmid to produce the amphotrophic stock of MT-RII beta retroviral vector. The infection with MT-RII beta and treatment with CdCl2 brought about growth arrest in HL-60 human leukemia and Ki-ras-transformed NIH 3T3 clone DT cells in monolayer culture with no sign of toxicity. The growth inhibition correlated with the expression of RII beta and accompanied changes in cell morphology; cells became flat, exhibiting enlarged cytoplasm. The growth of these cells in semisolid medium (anchorage-independent growth) was almost completely suppressed. In contrast, overexpression of the RI alpha subunit of protein kinase enhanced the cell proliferation in DT cells. The MT-RII beta-infected cells exhibited an increased sensitivity toward treatment with cAMP analogues, such as 8-Cl-cAMP and N6-benzyl-cAMP, as compared with the parental noninfected cells. In MT-RII beta HL-60 cells, N6-benzyl-cAMP treatment greatly enhanced the expression of monocytic surface markers. These results suggest that the RII beta cAMP receptor, by binding to its ligand, cAMP, acts as a tumor suppressor protein exerting growth inhibition, differentiation, and reverse transformation.
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PMID:Retroviral vector-mediated overexpression of the RII beta subunit of the cAMP-dependent protein kinase induces differentiation in human leukemia cells and reverts the transformed phenotype of mouse fibroblasts. 794 90

cAMP induced rapid apoptosis (> 90% cell death in 6 h) of non-growth-arrested rat leukemia IPC-81 cells. A cell clone selected for cAMP resistance had a normally functioning apoptotic machinery whose triggering required about 30-fold higher cellular cAMP than in the parent cells. The cAMP subresponsiveness was due to a heterozygous point mutation (Ala336-->Asp) in the RI subunit of cAMP-dependent protein kinase I. In fact, apoptosis correlated with intracellular cAMP binding to the subresponsive RI. The mutated alanine is invariantly present in cyclic nucleotide kinases, but of unknown function. The mutation decreased the cAMP affinity to site B by increasing the cAMP dissociation rate 500x. The ability of site B to discriminate adenine-modified cAMP analogues was affected, suggesting that Ala336 faced the adenine moiety of cAMP. That the heterozygously expressed RID336 was a dominant suppressor of apoptosis was explained by a higher expression of R than C subunits in the mutant cells by preferential expression of the mutant form of RI, and by the ability of mutant RI to exert dominant negative control of activation of wild type cAMP kinase at moderate cAMP levels. Apoptosis was induced at a similar cAMP level in cells treated with cholera toxin or other cAMP elevating agents, indicating that cAMP kinase was essential for toxin action.
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PMID:Antiapoptotic effect of heterozygously expressed mutant RI (Ala336-->Asp) subunit of cAMP kinase I in a rat leukemia cell line. 838 40

Rat IPC-81 promyelocytic leukemia cells responded to cAMP analog by undergoing apoptotic cell death both when anchored to fibronectin and when free in the medium. The protein kinase C stimulator 12-O-tetradecanoylphorbol 13-acetate enhanced the anchoring to substratum without impeding cAMP-induced cell death. The immobilized cells could be microinjected. This made it possible to study the effect on apoptosis of microinjected catalytic (C alpha) and regulatory (RI alpha D199) subunits of cAMP-dependent protein kinase as well as of phosphatase inhibitors. Microinjection of C alpha reproduced the morphological effects of cAMP, including nuclear fragmentation. RI alpha D199 blocked the effect of C alpha. Injection of microcystin-LR, which inhibits protein phosphatases 1 and 2A, led to pronounced apoptoid changes of the leukemia cells, but failed to produce nuclear fragmentation. Microinjection of peptide inhibitors ("inhibitor 1" and "inhibitor 2") specific for phosphatase 1 had no effect on cell morphology. The failure of the phosphatase inhibitors to reproduce completely the effect of the C subunit underscores the specificity of action of the latter.
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PMID:Microinjected catalytic subunit of cAMP-dependent protein kinase induces apoptosis in myeloid leukemia (IPC-81) cells. 838 20

Increased expression of the RI alpha subunit of cAMP-dependent protein kinase type I has been shown in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. The sequence-specific inhibition of RI alpha gene expression by an antisense oligodeoxynucleotide results in the differentiation of leukemia cells and growth arrest of cancer cells of epithelial origin. A single-injection RI alpha antisense treatment in vivo also causes a reduction in RI alpha expression and inhibition of tumor growth. Tumor cells behave like untransformed cells by making less protein kinase type I. The RI alpha antisense, which produces a biochemical imprint for growth control, requires infrequent dosing to restrain neoplastic growth in vivo.
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PMID:Protein kinase A-directed antisense restrains cancer growth: sequence-specific inhibition of gene expression. 891 9

Transcription factor Sp1 is a phosphoprotein whose level and DNA binding activity are markedly increased in doxorubicin-resistant HL-60 (HL-60/AR) leukemia cells. The trans-activating and DNA binding properties of Sp1 in HL-60/AR cells are stimulated by cAMP-dependent protein kinase (PKA) and PKA agonists and inhibited by PKA antagonists as well as by the PKA regulatory subunit. Reporter gene activity under the control of the Sp1-dependent SV40 promoter is stimulated in insect cells transiently expressing Sp1 and PKA, and the DNA binding activity of recombinant Sp1 is activated by exogenous PKA in vitro. These results indicate that Sp1 is a cAMP-responsive transcription factor and that Sp1-dependent genes may be modulated through a cAMP-dependent signaling pathway.
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PMID:Modulation of transcription factor Sp1 by cAMP-dependent protein kinase. 926 Nov 18

The cAMP pathway plays a central role in the response to hormonal signals for cell proliferation, differentiation and apoptosis. In IPC-81 leukaemia cells, activation of the cAMP pathway by prostaglandin E1 treatment, or other cAMP-elevating agents, induces apoptosis within 4-6 h. Inhibition of mRNA or protein synthesis during the first 2 h of cAMP induction protects cells from apoptosis, suggesting a requirement for early gene expression. cAMP-dependent protein kinase phosphorylates a class of nuclear factors and thereby regulates the transcription of a specific set of genes. Here we show that CREM (cAMP Responsive Element Modulator) expression is induced rapidly upon prostaglandin E1 treatment of IPC-81 cells. The induced transcripts correspond to the early product ICER (Inducible cAMP Early Repressor). ICER expression remains elevated until the burst of cell death. Protein synthesis inhibitors which prevent cAMP-induced apoptosis also block de novo ICER synthesis. Transfected IPC-81 cell lines, constitutively expressing high level of ICER are resistant to cAMP-induced cell death. In these transfected cells, cAMP fails to upregulate the ICER transcripts demonstrating that ICER exerts strongly its repressor function on CRE-containing genes. That an early expression of ICER blocks apoptosis, suggests that gene repression by endogenous ICER in IPC-81 is insufficient or occurs too late to protect cells against death. ICER transfected cells rescued from cAMP-induced apoptosis are growth arrested. It shows for the first time that CREM activation directly participates to the decision of the cell to die. ICER, by sequentially repressing distinct sets of CRE-containing genes could modulate cell fate.
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PMID:The transcriptional repressor ICER and cAMP-induced programmed cell death. 926 69

An elevated cAMP concentration results in growth arrest and protein synthesis-dependent apoptosis in the promyelocytic leukaemia cell line IPC-81. A comparison of two-dimensional gels of extracts from these cells labelled with [(35)S]methionine revealed that five distinct protein spots were induced by cAMP in a protein-synthesis-dependent manner. The spots seemed to result from the acidic shift of a precursor protein. The most abundant spot was phospho-actin. The spots induced by cAMP in intact cells were induced by cAMP-dependent protein kinase (cAPK) during the translation in vitro of mRNA from the leukaemia cells. The effect of cAPK was strictly co-translational, none of the spots being induced when cAPK was added after translation. This suggested that the protein spots arose by co-translational phosphorylation catalysed by cAPK. Two of the protein spots, phospho-actin and a protein with a molecular mass of 30 kDa and an isoelectric point of 4.5, were studied further with respect to expression. They were produced during the whole pre-apoptotic period, had cellular half-lives of several hours and were induced by the same concentrations of cAMP analogue that induced apoptosis. It is suggested that the accumulation of co-translationally modified proteins could be important for long-term cAMP signalling.
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PMID:cAMP induces co-translational modification of proteins in IPC-81 cells. 1045 24

Overexpression of the RIalpha subunit of cAMP-dependent protein kinase (PKA) has been demonstrated in various human cancers. PKA has been suggested as a potential target for cancer therapy. The goal of the present study was to evaluate an anti-PKA antisense oligonucleotide (mixed-backbone oligonucleotide) as a therapeutic approach to human cancer treatment. The identified oligonucleotide inhibited the growth of cell lines of human colon cancer (LS174T, DLD-1), leukemia (HL-60), breast cancer (MCF-7, MDA-MB-468), and lung cancer (A549) in a time-, concentration-, and sequence-dependent manner. In a dose-dependent manner, the oligonucleotide displayed in vivo antitumor activity in severe combined immunodeficient and nude mice bearing xenografts of human cancers of the colon (LS174T), breast (MDA-MB-468), and lung (A549). The routes of drug administration were intraperitoneal and oral. Synergistic effects were found when the antisense oligonucleotide was used in combination with the cancer chemotherapeutic agent cisplatin. The pharmacokinetics of the oligonucleotide after oral administration of (35)S-labeled oligonucleotide into tumor-bearing mice indicated an accumulation and retention of the oligonucleotide in tumor tissue. This study further provides a basis for clinical studies of the antisense oligonucleotide targeted to the RIalpha subunit of PKA (GEM 231) as a cancer therapeutic agent used alone or in combination with conventional chemotherapy.
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PMID:Antitumor activity and pharmacokinetics of a mixed-backbone antisense oligonucleotide targeted to the RIalpha subunit of protein kinase A after oral administration. 1057 Jan 86

Enhanced expression of the RIa subunit of cAMP-dependent protein kinase type I (PKA-I) has been shown during carcinogenesis, in human cancer cell lines and in primary tumors. We demonstrate that the sequence-specific inhibition of RIa gene expression by antisense oligonucleotides results in the differentiation of leukemia cells and growth arrest of cancer cells of epithelial origin and tumors in mice. The loss of RI by the antisense results in rapid increase in the half-life of the competitor molecule, RII protein, via its stabilization in a holoenzyme complex (PKA-II) that insures depletion of PKA-I and sustained inhibition of tumor growth. RI antisense, which restrains tumor cell growth by turning on the signals for blockade of tumor cell survival, namely blockade of the tyrosine kinase signaling, cell cycle deregulation and apoptosis, provides a single gene-targeting approach to treatment of cancer.
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PMID:Antisense DNA-targeting protein kinase A-RIA subunit: a novel approach to cancer treatment. 1057 86

The primary mediator of cAMP action in mammalian cells is cAMP-dependent protein kinase (PKA). There are two types of PKA, type I (PKA-I) and type II (PKA-II), which share a common catalytic subunit but contain distinct regulatory subunits, RI and RII, respectively. Evidence suggests that increased expression of RIalpha/PKA-I correlates with neoplastic cell growth. Here, we show that sequence-specific oligonucleotide inhibition of RIalpha expression results in inhibition of growth and modulation of cAMP signaling in cancer cells. The antisense promoted growth inhibition in a time-dependent, concentration-dependent, and sequence-dependent manner in human cancer cells in monolayer culture, and it inhibited colony formation in soft agar and tumor growth in nude mice. Among the cancer cells are LS-174T, HCT-15, and Colo-205 colon carcinoma cells; A-549 lung carcinoma cells; LNCaP prostate adenocarcinoma cells; Molt-4 leukemia cells; and Jurkat T lymphoma cells. Northern blot and immunoprecipitation analyses revealed that the growth inhibitory effect of the antisense correlated with a decrease in RIalpha expression at both the mRNA and protein levels. Pulse-chase experiments revealed that the antisense-directed inhibition of RIalpha expression resulted in compensatory changes in expression of the isoforms of R and C subunits and cAMP signaling in a cell type-specific manner. These results demonstrate that cAMP is ubiquitous in the regulation of cell growth and that the antisense oligonucleotide, which inhibits the synthesis of the RIalpha subunit of PKA, can be targeted to a single gene for treatment of cancer in a variety of cell types.
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PMID:Oligonucleotide sequence-specific inhibition of gene expression, tumor growth inhibition, and modulation of cAMP signaling by an RNA-DNA hybrid antisense targeted to protein kinase A RIalpha subunit. 1119 26


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