Detection of (11;22)(q24;q12) translocation-bearing cells in peripheral blood progenitor cells of patients with Ewing's sarcoma family of tumors.
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Base Sequence↗
Biomedical subjects
L Neckers
Publications and source records attributed to L Neckers.
Inhibition of protein-tyrosine kinase activity in intact cells by the aptameric action of oligodeoxynucleotides.
Direct interaction of oligodeoxynucleotides (ODNs) with proteins represents one of the nonantisense-mediated effects of ODNs. Phosphorothioate-capped ODNs have been shown to inhibit directly the in vitro kinase activity of the chronic myelogenous leukemia-associated protein-tyrosine kinase p210bcr-abl. In this study we have determined the efficacy of this aptameric ODN in a cellular system using the K562 chronic myelogenous leukemia-derived cell line. Significant effects upon cellular phosphotyrosine content, as well as cellular growth in soft agar, are observed. These effects are sequence specific and are not mediated through changes in p210bcr-abl protein levels. Additional ODNs are described that also reduce cellular phosphotyrosine levels and inhibit growth in soft agar but do not inhibit p210bcr-abl kinase activity in vitro.
Base Sequence↗
Contribution of sequence and phosphorothioate content to inhibition of cell growth and adhesion caused by c-myc antisense oligomers.
c-myc is overexpressed in glioblastoma multiforme, the most common form of brain tumor. To find a suitable target for in vivo antisense therapy of gliomas, we investigated the biological effects on the human glioma cell line, U87MG, of antisense oligonucleotides targeted against the translation start site of c-myc mRNA. Parameters examined included c-myc protein level, cell proliferation, and cell adhesion to substratum. Oligonucleotides were administered by electroporation as capped phosphorothioates. Antisense oligomers caused a reduction in c-myc protein expression, loss of cell adhesion to plastic, and complete growth inhibition. Various control sequences, including sense, scrambled, and three-base mismatched oligomers, were also tested. Some of the controls retained a dG quartet found in the antisense sequence. Reduction in c-myc protein and cell growth and loss of cell adhesion were specific to the antisense sequence. Surprisingly, fully thioated antisense and scrambled sequences, either containing or lacking a dG quartet, were equally inhibitory to both cell growth and adhesion. Loss of cell adhesion was observed with only phosphorothioate-containing oligomers, not with either their phosphodiester or nuclease-resistant PA congeners, and was completely reversed when cells were plated onto fibronectin. These results demonstrate that a commonly used c-myc antisense oligomer also displays dramatic, sequence- but not antisense-specific effects on cell proliferation and cellular adhesion, depending on the backbone.
Animals↗
Aptameric inhibition of p210bcr-abl tyrosine kinase autophosphorylation by oligodeoxynucleotides of defined sequence and backbone structure.
Protein tyrosine kinases play key roles in cellular physiology. Specific inhibitors of these enzymes are important laboratory tools and may prove to be novel therapeutic agents. In this report we describe a new class of tyrosine kinase inhibitor, synthetic oligodeoxynucleotides (ODNs). An ODN is described which specifically inhibits p210bcr-abl tyrosine kinase autophosphorylation in vitro with a Ki of 0.5 microM. Inhibition is non-competitive with respect to ATP. The effects upon inhibitory activity of ODN structure modifications are described. The inhibition described is not mediated by classical antisense mechanisms and represents an example of the recently recognized aptameric properties of ODNs.
3T3 Cells↗
Interleukin-6 antisense deoxyoligonucleotides inhibit bone resorption by giant cells from human giant cell tumors of bone.
The effects of antisense constructs to IL-6 on the bone-resorbing capacity of purified giant cells from giant cell tumors of bone were examined to further define the role of IL-6 in human osteoclastic bone resorption. In addition, we wanted to determine the utility of antisense constructs to cytokines produced by osteoclasts as probes to identify the molecular events responsible for the bone-resorptive process. Giant cells were cultured on sperm whale dentin for 24 h in the presence of fluoresceinated antisense or scrambled antisense deoxyoligonucleotides complementary to IL-6 mRNA. The giant cells actively incorporated these oligonucleotides, as evidenced by their intense fluorescence. The number of resorptive lacunae formed and the area of the dentin resorbed were significantly decreased in cultures of giant cells treated with antisense IL-6 constructs compared with control cultures treated with scrambled antisense constructs to IL-6 (60 +/- 13 versus 12 +/- 6 lacunae and 1.2 +/- 0.3 versus 0.26 +/- 0.1 x 10(5) microns2). IL-6 levels in conditioned media from giant cell cultures treated with IL-6 antisense constructs were fourfold lower than those in control media obtained from giant cells treated with scrambled antisense constructs to IL-6. These data confirm the capacity of IL-6 antisense oligomers to block IL-6 production by these cells. These observations show that IL-6 plays an important role in the bone-resorptive process of human osteoclasts and suggest that antisense constructs to cytokines produced by bone cells may be useful for determining the molecular events occurring during bone resorption.
Animals↗
Antisense inhibition of CHP100 C-myc expression results in reduced in vitro growth kinetics and loss of in vivo tumorigenesis.
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Blotting, Western↗
Electroporation enhances c-myc antisense oligodeoxynucleotide efficacy.
Obtaining high transfection efficiencies and achieving appropriate intracellular concentrations and localization are two of the most important barriers to the implementation of gene targeted therapy. The efficiency of endogenous uptake of oligodeoxynucleotides (ODNs) varies from cell type to cell type and may be a limiting factor of antisense efficacy. The use of electroporation to obtain high intracellular concentrations of a synthetic ODN in essentially 100% of viable cells is described. It is also shown that the transfected ODNs initially localize to the nucleus and remain there for at least 48 hours. The cellular trafficking of electroporated ODNs is shown to be an energy dependent process. Targeting of the c-myc proto-oncogene of U937 cells by electroporation of phosphorothioate-modified ODNs results in rapid and specific suppression of this gene at ODN concentrations much lower than would otherwise be required. This technique appears to be applicable to a variety of cell types and may represent a powerful new investigate tool as well as a promising approach to the ex vivo treatment of hematologic disorders.
Animals↗
Effect of over-expression of bacterial ribonuclease H on the utility of antisense MYC oligodeoxynucleotides in the monocytic leukemia cell line U937.
RNase H has been clearly implicated in vitro in mediating some antisense effects. In vivo evidence is limited to experiments performed in Xenopus oocytes in which antisense oligonucleotides are microinjected. In other mammalian cell systems scant data have been obtained to support or deny a role for RNase H as an antisense mediator in vivo. These experiments were designed to test the hypothesis that RNase H mediates the MYC antisense-induced reduction in MYC protein observed in the human monocytic leukemia cell line U937. A bacterial RNase H-containing episomal replicon was constructed and stable transfectants were obtained which expressed E coli RNase H in their cytoplasm at a 10-fold higher level than endogenous RNase H. These cells failed to demonstrate heightened sensitivity to MYC antisense (phosphorothioate, end capped and phosphodiester) compared with untransfected or E coli RNase H antisense transfected cells. PCR analysis of each transfectant treated and untreated with MYC antisense failed to demonstrate the appearance of truncated MYC mRNA. These results do not support a role for RNase H in the mediation of MYC antisense-induced MYC protein reduction and growth inhibition in U937 cells.
Base Sequence↗
Antisense technology: biological utility and practical considerations.
Antisense RNA and DNA techniques have been developed as a relatively recent approach to the specific modulation of gene expression in vitro and in vivo. This review discusses general considerations for the application of antisense techniques. We shall examine the relative advantages and disadvantages of DNA versus RNA techniques, as well as the common pitfalls peculiar to each strategy.
Animals↗
Specific inhibition of oncogene expression in vitro and in vivo by antisense oligonucleotides.
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Animals↗
Antisense inhibition of oncogene expression.
To understand the role of individual genes in regulating biological processes, one must be able to interfere specifically with either their expression or function. While monoclonal antibodies have proven very useful in studying cell surface proteins, the specific inhibition of intracellular proteins in viable cells is a much more difficult problem. The goal of antisense technology is to develop small oligonucleotides, plasmids, or retroviral vectors which can be readily introduced into living cells in order to inhibit specific gene expression. In this review, we briefly describe the principles of antisense usage, including problems of cellular uptake and intracellular distribution, mechanism of antisense action, and the properties of various oligonucleotide derivatives. In addition we present several examples of the biological effects of antisense administration used to study the role of specific genes in the regulation of cell growth and differentiation.
Animals↗
Gamma/delta lineage relationship within a consecutive series of human precursor T-cell neoplasms.
We analyzed the gene rearrangements associated with the newly described delta T-cell receptor (TCR) gene from a series of 19 consecutive precursor T-cell (lymphoblastic) neoplasms that represent discrete stages surrounding the TCR gene rearrangement process. Significantly, the delta TCR gene showed rearrangement in most (13 of 19) of these T cells, and in addition it was rearranged in two cells displaying no rearrangement for any other TCR gene. Our survey showed three types of delta gene rearrangements associated with cell-surface TCR expression that presumably represent usage of three V delta genes. This analysis demonstrates (1) a major subclass of human precursor T-cell neoplasms belonging to the gamma/delta T-cell receptor-rearranging subtype; (2) a narrow repertoire of human V delta gene usage; and (3) the utility of delta gene rearrangements as a diagnostic clonal marker in precursor T lymphoblastic neoplasms.
Amino Acid Sequence↗
Site-selective cyclic AMP analogs as new biological tools in growth control, differentiation, and proto-oncogene regulation.
The physiologic role of cyclic adenosine monophosphate (cAMP) in the growth control of a spectrum of human cancer lines, including leukemic lines, and v-rasH oncogene-transformed NIH/3T3 cells is demonstrated by the use of site-selective cAMP analogs. These cAMP analogs, which can select either of the two known cAMP binding sites of the cAMP receptor protein, induce potent growth inhibition, phenotypic change, and differentiation (leukemic cells) of cancer cells at micromolar concentrations with no sign of cytotoxicity. The growth inhibition parallels selective modulation of cAMP-dependent protein kinase isozymes, type I versus type II, and suppression of cellular proto-oncogene expression. Site-selective cAMP analogs thus provide new biological tools for investigating cell proliferation and differentiation and also for the improved management of human cancers.
Animals↗
Synergistic inhibition of growth of breast and colon human cancer cell lines by site-selective cyclic AMP analogues.
Our past studies on the mechanism of cyclic AMP (cAMP)-mediated control of tumor growth, using the experimental rat mammary tumor models as well as human breast cancer cell lines, indicated that the action of cAMP is mediated by the RII cAMP receptor protein, the regulatory subunit of cAMP-dependent protein kinase type II (Y. S. Cho-Chung, J. Cyclic Nucleotide Res., 6: 163, 1980). We now shown that the site-selective cAMP analogues, which are manyfold more active in binding to the cAMP receptor protein than previously studied analogues, demonstrate a potent growth inhibition of seven breast and three colon human cancer cell lines. The cAMP receptor protein has two different cAMP binding sites, and cAMP analogues that selectively bind to either one of the two binding sites are known as either site 1 selective (C-8 analogues) or site 2 selective (C-6 analogues). Nineteen site-selective analogues, C-6 and C-8 monosubstituted and C-6,-8 disubstituted, were tested for their growth regulatory effect. The majority of these analogues demonstrated an appreciable growth inhibition, with no sign of toxicity in all 10 cancer lines at micromolar concentrations. The three most potent inhibitors were 8-Cl-, N6-benzyl-, and N6-phenyl-8-thio-p-chlorophenyl-cAMP, demonstrating 50% growth inhibition at 5-25 microM concentrations (IC50). Furthermore, N6-analogues, in combination with halogen or thio derivatives of C-8 analogues, demonstrated synergistic enhancement of growth inhibition. The growth inhibition paralleled a change in cell morphology, an augmentation of the RII cAMP receptor protein, and a reduction in p21 ras protein. The growth inhibition by 8-Cl-cAMP was not due to its metabolite, 8-Cl-adenosine, since: (a) the growth inhibition by 8-Cl-cAMP was released upon cessation of treatment, whereas that by 8-Cl-adenosine was not released; (b) 8-Cl-cAMP treatment did not affect cell cycle progression, whereas 8-Cl-adenosine brought about G1 synchronization; (c) 8-Cl-cAMP treatment caused reduction of p21 ras protein, whereas 8-Cl-adenosine did not affect p21 levels; and (d) 8-Cl-adenosine was not detected in either cell extracts or medium from the cells treated with 8-Cl-cAMP for 48-72 h. Site-selective cAMP analogues thus provide a new physiological means to control the growth of breast and colon human cancer cells.
Breast Neoplasms↗
Reverse transformation of Harvey murine sarcoma virus-transformed NIH/3T3 cells by site-selective cyclic AMP analogs.
Eighteen site-selective cAMP analogs modified at either the C-8 position or the C-6 position were tested for their growth regulatory effects on the Harvey murine sarcoma virus-transformed NIH/3T3 clone 13-3B-4 cells grown in a serum-free defined medium. All 18 analogs, when tested individually, exhibited an appreciable growth inhibitory effect at micromolar concentrations. The most potent growth inhibitory analogs contained a thio moiety at the C-8 position. In general, C-6 analogs required 5-10-fold greater concentrations than C-8 analogs to produce the same degree of growth inhibition. The growth inhibition induced by these analogs was accompanied by a change in cell morphology; cells treated with the analogs exhibited the morphology characteristic of untransformed fibroblasts, while untreated cells retained a transformed phenotype. The regulatory subunit of cAMP-dependent protein kinase, the cAMP receptor protein, has two different intrachain cAMP binding sites, and cAMP analogs modified at the C-8 position (C-8 analogs) are generally selective for Site 1, while analogs modified at the C-6 position (C-6 analogs) are generally selective for Site 2. Thus, C-8 and C-6 analogs were tested in combination to enhance the growth regulatory effect. Both growth inhibition and morphological change were enhanced synergistically by a combination of the C-6 and C-8 analogs. Two C-6 analogs or two C-8 analogs added together did not cause synergism. For both growth inhibition and phenotypic change, C-8 thio analogs acted far more synergistically than C-8 amino analogs when cells were treated in combination with C-6 analogs, suggesting a response of the RII rather than the RI cAMP receptor protein. DEAE-cellulose chromatography revealed that the growth inhibition, in fact, correlates with an increase of the RII cAMP receptor protein and a decrease of the RI receptor protein. The growth inhibitory effect of the site-selective analogs was not due to the cytotoxic effect of adenosine metabolites as shown by the different behavior of 8-Cl-cAMP compared with 8-Cl-adenosine in 1) cell cycle effects and 2) release from growth inhibition. It is concluded that the observed growth inhibition and phenotypic reversion of 13-3B-4 cells is most likely mediated through the cellular effector, the RII cAMP receptor protein.
Animals↗
Site-selective cyclic AMP analogs provide a new approach in the control of cancer cell growth.
Site-selective cyclic AMP analogs bind to site 1 or site 2 of the known cAMP-binding sites depending on the position of substituents on the purine ring, either at C-2 and C-8 (site 1) or at C-6 (site 2). The growth inhibitory effect of such site-selective cAMP analogs used in this investigation with 15 human cancer cell lines surpassed that of analogs previously tested. The most potent analogs were 8-chloro, N6-benzyl and N6-phenyl-8-p-chlorophenylthio-cAMP. The combination of a C-8 with an N6 analog had synergistic effects. The 24 site-selective analogs tested produced growth inhibition ranging from 30 to 80% at micromolar concentrations with no sign of toxic effects. Growth inhibition was not due to a block in a specific phase of the cell cycle but paralleled a change in cell morphology, an increase of the RII cAMP receptor protein and a decrease of p21 ras protein. Since the adenosine counterpart of the 8-chloro analog produced G1 synchronization without affecting the RII and p21 ras protein levels, it is unlikely that an adenosine metabolite is involved in the analog effect. Site-selective cAMP analogs thus provide a new biological tool for control of cancer growth.
Breast Neoplasms↗
Spontaneous alteration of idiotype in a monoclonal B-cell lymphoma. Escape from detection by anti-idiotype.
The surface immunoglobulin of B-cell neoplasms provides a specific point of attack for potential antibody therapy. The capacity of anti-idiotype antibody to home to the target neoplasm requires that the idiotype be unique and that it be expressed by every cell in the neoplastic clone. We describe the evolution of an altered idiotype in a follicular lymphoma that resulted in escape from laboratory detection by monoclonal anti-idiotype antibody. This was not due to the emergence of a second (biclonal) lymphoma, since all the neoplastic cells were otherwise identical both phenotypically and genotypically, as determined by flow cytometry and genomic DNA (Southern blot) hybridization, respectively. All cells expressed the same B-cell immunotype and bore a constant amount of IgMk. The demonstration of a single configuration of immunoglobulin-gene DNA confirmed monoclonality and established that the change in idiotype was not a result of new gene rearrangements but was more likely due to somatic mutation of the variable region--a process presumed to occur naturally in B cells. These data demonstrate the lability of idiotype expression and define a mechanism by which B-cell neoplasms may become unresponsive to anti-idiotype therapy.
Adult↗
Deficient helper cell function as a cause of diminished pokeweed mitogen blastogenic responses in patients with non-Hodgkin's lymphomas.
An investigation has been made of immunoregulatory T-cell function in the non-Hodgkin's lymphomas by comparing immunoregulation of healthy control and patient peripheral blood lymphocyte blastogenic responses to pokeweed mitogen. Normal mononuclear leukocytes (MNL) had significantly higher responses than patient MNL. MNL were subsequently separated into T- and non-T-cell fractions by differential E-rosette sedimentation for co-culture experiments. When normal non-T-cells and autologous irradiated T-cells were recombined, the mitogenic response again exceeded the response of patient non-T-cells recombined with their own irradiated T-cells. However, when normal non-T-cells were co-cultured with patient irradiated T-cells, the mitogenic response was diminished. Moreover, when patient non-T-cells were co-cultured with normal irradiated T-cells, a normal proliferative response occurred. These differences in non-T-cell response are not simply a result of allogeneic effects, since normal non-T-cell responses were the same regardless of whether autologous or normal allogeneic irradiated T-cells were used as helpers. Furthermore, co-culture of normal non-T-cells simultaneously with autologous irradiated T-cells and patient irradiated T-cells revealed no diminution of blastogenic response compared with co-cultures of normal non-T-plus autologous irradiated T only, suggesting no net suppression by patient irradiated T-cells. Studies with monoclonal antibodies revealed that patient T-cells had normal to increased ratios of OK-T4+:OK-T8+ cells. These results suggest that peripheral blood T-cells from patients with non-Hodgkin's lymphomas, despite the presence of a normal to increased ratio of OK-T4+:OK-T8+ cells, are functionally deficient in their helper capacity for non-T-cell blastogenic response to pokeweed mitogen. Abnormal helper T-cell function may explain some of the immune deficits in patients with non-Hodgkin's lymphoma and may be important in the pathogenesis of these diseases.
Adult↗