Differentiation of erythroleukemic cells in vitro: irreversible induction by dimethyl sulfoxide (DMSO)

Lessons we can learn from neurons to make cancer cells quiescent

Cancer is a major concern for contemporary societies. However, the incidence of cancer is unevenly distributed among tissues and cell types. In particular, the evidence indicates that neurons are absolutely resistant to cancer and this is commonly explained on the basis of the known postmitotic state of neurons. The dominant paradigm on cancer understands this problem as a disease caused by mutations in cellular genes that result in unrestrained cell proliferation and eventually in tissue invasion and metastasis. However, the evidence also shows that mutations and gross chromosomal anomalies are common in functional neurons that nevertheless do not become neoplastic. This fact suggests that in the real nonexperimental setting mutations per se are not enough for inducing carcinogenesis but also that the postmitotic state of neurons is not genetically controlled or determined, otherwise there should be reports of spontaneously transformed neurons. Here we discuss the evidence that the postmitotic state of neurons has a structural basis on the high stability of their nuclear higher order structure that performs like an absolute tumor suppressor. We also discuss evidence that it is possible to induce a similar structural postmitotic state in nonneural cell types as a practical strategy for stopping or reducing the progression of cancer.

Marmoset induced pluripotent stem cells: Robust neural differentiation following pretreatment with dimethyl sulfoxide

The marmoset is an important nonhuman primate model for regenerative medicine. For experimental autologous cell therapy based on induced pluripotent (iPS) cells in the marmoset, cells must be able to undergo robust and reliable directed differentiation that will not require customization for each specific iPS cell clone. When marmoset iPS cells were aggregated in a hanging drop format for 3 days, followed by exposure to dual SMAD inhibitors and retinoic acid in monolayer culture for 3 days, we found substantial variability in the response of different iPS cell clones. However, when clones were pretreated with 0.05-2% dimethyl sulfoxide (DMSO) for 24 hours, all clones showed a very similar maximal response to the directed differentiation scheme. Peak responses were observed at 0.5% DMSO in two clones and at 1% DMSO in a third clone. When patterns of gene expression were examined by microarray analysis, hierarchical clustering showed very similar responses in all 3 clones when they were pretreated with optimal DMSO concentrations. The change in phenotype following exposure to DMSO and the 6 day hanging drop/monolayer treatment was confirmed by immunocytochemistry. Analysis of DNA content in DMSO-exposed cells indicated that it is unlikely that DMSO acts by causing cells to exit from the cell cycle. This approach should be generally valuable in the directed neural differentiation of pluripotent cells for experimental cell therapy.

Erythroid differentiation ability of butyric acid analogues: identification of basal chemical structures of new inducers of foetal haemoglobin

Several investigations have demonstrated a mild clinical status in patients with β-globin disorders and congenital high persistence of foetal haemoglobin. This can be mimicked by a pharmacological increase of foetal γ-globin genes expression and foetal haemoglobin production. Our goal was to apply a multistep assay including few screening methods (benzidine staining, RT-PCR and HPLC analyses) and erythroid cellular model systems (the K562 cell line and erythroid precursors collected from peripheral blood) to select erythroid differentiation agents with foetal haemoglobin inducing potential. With this methodology, we have identified a butyric acid derivative, namely the 4174 cyclopropanecarboxylic acid compound, able to induce erythroid differentiation without antiproliferative effect in K562 cells and increase of γ-globin gene expression in erythroid precursor cells. The results are relevant for pharmacological treatments of haemoglobinopathies, including β-thalassaemia and sickle cell anaemia.

Activation of the cnidarian oxidative stress response by ultraviolet radiation, polycyclic aromatic hydrocarbons and crude oil

Organisms are continuously exposed to reactive chemicals capable of causing oxidative stress and cellular damage. Antioxidant enzymes, such as superoxide dismutases (SODs) and catalases, are present in both prokaryotes and eukaryotes and provide an important means of neutralizing such oxidants. Studies in cnidarians have previously documented the occurrence of antioxidant enzymes (transcript expression, protein expression and/or enzymatic activity), but most of these studies have not been conducted in species with sequenced genomes or included phylogenetic analyses, making it difficult to compare results across species due to uncertainties in the relationships between genes. Through searches of the genome of the sea anemone Nematostella vectensis Stephenson, one catalase gene and six SOD family members were identified, including three copper/zinc-containing SODs (CuZnSODs), two manganese-containing SODs (MnSODs) and one copper chaperone of SOD (CCS). In 24 h acute toxicity tests, juvenile N. vectensis showed enhanced sensitivity to combinations of ultraviolet radiation (UV) and polycyclic aromatic hydrocarbons (PAHs, specifically pyrene, benzo[a]pyrene and fluoranthene) relative to either stressor alone. Adult N. vectensis exhibited little or no mortality following UV, benzo[a]pyrene or crude oil exposure but exhibited changes in gene expression. Antioxidant enzyme transcripts were both upregulated and downregulated following UV and/or chemical exposure. Expression patterns were most strongly affected by UV exposure but varied between experiments, suggesting that responses vary according to the intensity and duration of exposure. These experiments provide a basis for comparison with other cnidarian taxa and for further studies of the oxidative stress response in N. vectensis.

Platelets from mice lacking the aryl hydrocarbon receptor exhibit defective collagen-dependent signaling

BACKGROUND

We previously identified aryl hydrocarbon receptor (AHR) as a novel regulator of megakaryocytic differentiation and polyploidization and reported that AHR-null mice have approximately 15% fewer platelets than do wild-type mice, yet they exhibit a dramatic, unexplained bleeding phenotype.

OBJECTIVES

The current work tests our hypothesis that AHR-null platelets are functionally deficient, contributing to the previously reported (yet unexplained) bleeding phenotype present in AHR-null mice.

METHODS

AHR-null bone marrow was ex vivo differentiated with thrombopoietin with or without AHR ligands or AHR inhibitors and analyzed for degree of megakaryopoiesis and polyploidization. Platelet function of AHR-null mice was assessed with aggregation and spreading assays. Platelet signaling was examined using Western analysis and Rac activity assays.

RESULTS

AHR ligands differentiate murine bone marrow-derived progenitors into polyploid megakaryocytes in the absence of thrombopoietin, and AHR inhibitors block thrombopoietin-induced megakaryocytic differentiation. Despite their responsiveness toward thrombin, AHR-null platelets demonstrate decreased aggregation and spreading in response to collagen compared with wild-type platelets. AHR-null platelets bind fibrinogen after stimulation with thrombin or AYPGKF and aggregate in response to AYPGKF and adenosine diphosphate. Mechanistically, AHR absence led to down-regulation of Vav1 and Vav3, altered phospholipase Cγ2 phosphorylation, decreased Rac1 activation, and reduced platelet activation in response to collagen.

CONCLUSIONS

These results are consistent with a role for AHR in platelet function, especially as it relates to platelet aggregation and spreading in response to collagen. Our work suggests AHR is a critical component of the physiologic response that platelets undergo in response to collagen and may provide novel treatment options for patients with bleeding disorders.

Dimethyl sulfoxide has an impact on epigenetic profile in mouse embryoid body

Dimethyl sulfoxide (DMSO), an amphipathic molecule, is widely used not only as a solvent for water-insoluble substances but also as a cryopreservant for various types of cells. Exposure to DMSO sometimes causes unexpected changes in cell fates. Because mammalian development and cellular differentiation are controlled epigenetically by DNA methylation and histone modifications, DMSO likely affects the epigenetic system. The effects of DMSO on transcription of three major DNA methyltransferases (Dnmts) and five well-studied histone modification enzymes were examined in mouse embryonic stem cells and embryoid bodies (EBs) by reverse transcription-polymerase chain reaction. Addition of DMSO (0.02%-1.0%) to EBs in culture induced an increase in Dnmt3a mRNA levels with increasing dosage. Increased expression of two subtypes of Dnmt3a in protein levels was confirmed by Western blotting. Southern blot analysis revealed that DMSO caused hypermethylation of two kinds of repetitive sequences in EBs. Furthermore, restriction landmark genomic scanning, by which DNA methylation status can be analyzed on thousands of loci in genic regions, revealed that DMSO affected DNA methylation status at multiple loci, inducing hypomethylation as well as hypermethylation depending on the genomic loci. In conclusion, DMSO has an impact on the epigenetic profile: upregulation of Dnmt3a expression and alteration of genome-wide DNA methylation profiles with phenotypic changes in EBs.

Effects on erythroid differentiation of platinum(II) complexes of synthetic bile acid derivatives

In this study, we compared some bile acid derivatives and their platinum(II) complexes with respect to their ability to induce erythroid differentiation of human leukemic K562 cells. The complexes analyzed were cis-[(3-dehydrocholanoyliden-L-tartrate)-diammineplatinum(II)] (compound 1) and cis-[di(dehydrocholanoate)-bis(triphenylphosphine)-platinum(II)] (compound 3), together with their free ligands, respectively, 3-dehydrocholanoyliden-L-tartaric acid (compound 2) and dehydrocholanoic acid (4), and their parent compounds, respectively, cisplatin and cis-[dichloride-bis(triphenylphosphine)-platinum(II)] (5). We found that compound 1 stimulates erythroid differentiation of K562 cells and an increase of fetal hemoglobin (HbF) production in erythroid precursor cells isolated from peripheral blood of human subjects. This increase is similar to that obtained by hydroxyurea, a potent inducer of HbF production both in vitro and in vivo. Another important conclusion of this study is related to the evaluation of the effects of compound 1 on production of gamma-globin mRNA in human erythroid precursors grown in the two-stage liquid culture system. We demonstrated that compound 1 induces preferential accumulation of gamma-globin mRNA. The results presented in this manuscript could have practical impact, since it is well known that an increase in HbF production could ameliorate the clinical status of patients with beta-thalassemia and sickle cell anemia.

Modulation of trophoblast stem cell and giant cell phenotypes: analyses using the Rcho-1 cell model

Trophoblast giant cells are located at the maternal-embryonic interface and have fundamental roles in the invasive and endocrine phenotypes of the rodent placenta. In this report, we describe the experimental modulation of trophoblast stem cell and trophoblast giant cell phenotypes using the Rcho-1 trophoblast cell model. Rcho-1 trophoblast cells can be manipulated to proliferate or differentiate into trophoblast giant cells. Differentiated Rcho-1 trophoblast cells are invasive and possess an endocrine phenotype, including the production of members of the prolactin (PRL) family. Dimethyl sulfoxide (DMSO), a known differentiation-inducing agent, was found to possess profound effects on the in vitro development of trophoblast cells. Exposure to DMSO, at non-toxic concentrations, inhibited trophoblast giant cell differentiation in a dose-dependent manner. These concentrations of DMSO did not significantly affect trophoblast cell proliferation or survival. Trophoblast cells exposed to DMSO exhibited an altered morphology; they were clustered in tightly packed colonies. Trophoblast giant cell formation was disrupted, as was the expression of members of the PRL gene family. The effects of DMSO were reversible. Removal of DMSO resulted in the formation of trophoblast giant cells and expression of the PRL gene family. The phenotype of the DMSO-treated cells was further determined by examining the expression of a battery of genes characteristic of trophoblast stem cells and differentiated trophoblast cell lineages. DMSO treatment had a striking stimulatory effect on eomesodermin expression and a reciprocal inhibitory effect on Hand1 expression. In summary, DMSO reversibly inhibits trophoblast differentiation and induces a quiescent state, which mimics some but not all aspects of the trophoblast stem cell phenotype.

A proposal regarding the mechanism which underlies lineage choice during hematopoietic differentiation

We present a simple Boolean Network model of a genetic regulatory network which can account for the differentiation of hemopoietic cells. In this model while decision choice is stochastic, the probability of differentiating along a specific pathway is determined by the gene expression state of the cell when the signal to differentiate appears. This probability can be altered by the acute and chronic needs of the individual. Mutations disrupt normal maturation. The paper also presents a larger Boolean Network model which can be used to study normal and leukemic stem cell attractor states.

Repression of neu-induced clonogenicity by dimethylsulfoxide correlates with decreased levels of neu-encoded cell-surface p185 and changes in phosphotyrosine content of endogenous proteins

Treatment of neu-transformed fibroblasts with dimethylsulfoxide (DMSO), results in change in morphology and loss of clonogenicity. Although the total amount of neu-encoded p185 protein and mRNA remained constant after DMSO treatment, cell-surface p185 decreased by 60%, indicating that transmembrane p185 protein is not located in its physiological position. The aberrant location of p185 induced by DMSO resulted in increased tyrosine phosphorylation of p185 and concomitant decreased tyrosine phosphorylation of potential substrate proteins of p185 in the cell. However, the autophosphorylation activity of p185 in vitro was unaffected by DMSO. Thus, DMSO-induced loss of clonogenicity may be due to inappropriate location of p185, which prevents interaction between p185 and its substrates and therefore inhibits p185-mediated signal transduction pathway.

Alkylformamides as inducers of tumour cell differentiation--a mini-review

The induction of terminal differentiation in tumour cells represents a possible therapeutic strategy for treating cancer. The alkylformamides are 1 group of experimental compounds which have been shown to induce terminal differentiation in human HL-60 leukemia and murine Friend erythroleukemia cells in vitro. Their mechanism of action is unknown. Dimethylformamide has been used as a model inducer in carcinoma and fibroblastic models. Analysis of the relationship between structure and inducing activity of the alkylformamides in vitro reveals that no specificity of structure exists and that their properties as inducers of terminal differentiation extend to related compounds, e.g. the alkylacetamides and alkylureas. This is in contrast to the marked specificity of N-methylformamide (NMF) as an in vivo antitumour agent. The potency of these compounds as inducers of differentiation is predictable and correlated with their molecular weight. High concentrations of NMF are required to induce differentiation in vitro and these concentrations are not achievable in vivo. However, while NMF is unlikely to be a useful inducer in vivo many of its higher MW analogues are very much more potent as inducers in vitro and yet no more toxic (to the host) in vivo. Some of these (e.g. tetramethylurea or 1,3-dimethylurea) may be capable of achieving inducing concentrations in vivo.

Induction of human malignant T-lymphoblastic cell lines MOLT-3 and jurkat by 12-O-tetradecanoylphorbol-13-acetate: biochemical, physical, and morphological characterization

The process of induction of human malignant T-lymphoblastic cell line MOLT-3 by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was examined. It was found that the induction process by TPA, which included increase in cells with receptors to sheep red blood cells (E--rosette positive--E+) and decrease in the levels of the marker enzyme terminal deoxynucleotidyl transferase (TdT) was not affected by the presence of DNA synthesis inhibitor arabinofuranosylcytosine (Ara-C). The exposure time to TPA required to elicit these changes was found to be short, in the order of 1 hour or less. The kinetics of the increased in E+ cells, decrease in the levels of TdT in these cells, or decrease in the ability to proliferate as measured by colony formation were similar with exposure to TPA for 1, 6, 24, or 96 hours. We have examined the effect of antitumor promoter compounds on their ability to block induction of MOLT-3 cells by TPA. Results indicated that none of these compounds, dexamethasone, antipain, retinoic acid, and L-1-tosylamide-2-phenylethylchloromethyl ketone (TPCK), was effective in reducing the number of E+ cells induced by TPA. Examination of three other leukemic T-cell lines indicated that, in addition to MOLT-3, the leukemic T-cell line Jurkat also responded to TPA, whereas two other leukemic T-cells lines CCRF-CEM and CCRF-HSB-2 did not. Certain physical and morphological changes were also observed after stimulation of MOLT-3 cells and Jurkat cells by TPA. We found that, following the addition of TPA, the cell volumes of MOLT-3 cells decreased from an average of 1150 micrometers3 to about 500 micrometers3, whereas those of Jurkat were reduced to about 700 micrometers3 from 1100 micrometers3. Electron microscopic studies of these lymphoblasts also revealed that after treatment with TPA the induced cells were generally smaller in size with increase in the density of the nuclear materials and condensation of the chromatin structures.

Early changes in ornithine decarboxylase activity during Friend leukemia cell differentiation

Agents such as dimethylsulfoxide, N,N'-dimethylformamide and bisacetyldiaminopentane that induce erythroid differentiation of Friend leukemia cells, cause a rapid increase in ornithine decarboxylase (EC 4.1.1.17) activity in intact cells during the 'latent' period preceding the accumulation of hemoglobin-containing cells. Blockage of erythroid differentiation with 5-bromo-2'-deoxyuridine did not prevent these alterations in enzyme activity. Addition of each chemical inducer in the extracts of these cells stimulate the basal levels of ornithine decarboxylase activity. These data indicate that the chemical inducers of differentiation modify the normal pattern of ornithine decarboxylase activity in this system.

New aspects of preleukemic disorders

Preleukemic disorders are a controversial group of panmyelopathic disturbances that often precede the emergence of acute myeloblastic or myelomonocytic leukemia. In most instances, these preleukemic disorders are characterized by slowly developing myeloblastosis of the bone marrow. They include preleukemia, primary acquired panmyelopathy with myeloblastosis or smouldering acute leukemia, erythroleukemia, and subacute myelomonocytic leukemia. Sometimes, transitions between these various preleukemic disorders may be observed in a single individual. Abnormalities in cellular differentiation are expressed in cytochemical aberrations and in elaboration of colony forming units by marrow cells of patients with preleukemic disorders. Cytogenic and cellular kinetic abnormalities link preleukemic disorders closely to acute myeloblastic or myelomonocytic leukemia, although in many patients with preleukemic disorders, conversion to acute leukemia is not observed or perhaps not recognized. Understanding pathogenetic and pathophysiological aspects of preleukemic disorders may shed light on aspects of cellular proliferation and cellular differentiation in the acute leukemias.

Friend leukemia cells: relationship between differentiation, clonogenicity and malignancy

Friend leukemia cells were cultured in vitro in the presence or absence of agents which induce erythroid differentiation. The cultures were harvested and the degree of differentiation determined. Clonogenicity of the cells in vitro and malignancy in vivo were determined as well. There was an inverse exponential relationship between the degree of differentiation and the clonogenicity of the culture. Differentiation was also associated with a modest decline in malignancy. Of interest was the observation that bromodeoxyuridine inhibited the biochemical manifestations of erythroid differentiation, but did not prevent the decline in clonogenicity which accompanied differentiation.

Early and late volume changes during erythroid differentiation of cultured Friend leukemic cells

Friend erythroleukemic cells (FLC) can be induced to differentiate in vitro by addition of dimethylsulfoxide (DMSO). We have studied the kinetics of induction by measuring cell volume, volume coefficient of variation and cell doubling time. Two distinct volume changes (early and late) are observed after the addition of the inducing agent. The early change occurs after ten hours and consist of a 10-20% decrease in volume compared to an untreated control population. This shift persists for two days and its magnitude is proportional to both the concentration of DMSO and the number of differentiated cells seen on day 5. FLC lines which induce weakly or not all with DMSO exhibit a reduced or absent early volume shift. Inclusion of a local anaesthetic in the culture prevents the appearance of differentiated cells and also counteracts the early volume shift. The exact time of the early volume change is a function of cell growth rate and appears to be cell cycle related. Synchronized cell populations exposed to DMSO during G2 and S phase undergo one round of mitosis before expression of the volume change whereas cells in G2-M express the change only after a second mitosis. A later, more gradual decrease in volume is observed in those cultures which begin to produce hemoglobin. It occurs after approximately five doubling times and coincides with the first appearance of hemoglobin-containing cells. Volume distribution parameters indicate that only a proportion of the population becomes smaller in size.

The in vivo effect of dimethyl sulphoxide (DMSO) on protein synthesis and the polyribosome profile in Paramecium

When Paramecium tetraurelia in log phase growth is treated with 4% dimethyl sulphoxide (DMSO) for five minutes the amount of polyribosomes is reduced 3- to 4-fold while there is a corresponding increase in 80s ribosomal material. Reducing the concentration of DMSO to 1% allows immediate reversal of the condition. Paramecium polyribosomes subjected to 4% DMSO either in whole cell homogenates or during purification through sucrose density gradients appear unaffected while cycloheximide at concentrations up to 100 mug/ml did not prevent DMSO from exerting its effect in vivo. Analyses of 14C amino acid incorporation experiments indicated a strict correspondence between the effect of DMSO on polyribosomes and overall protein synthesis. The reduction of acid precipitable radioactivity in the polyribosomal region after DMSO treatment was associated with a corresponding increase in radioactivity in the 80s region. There was no comparable increase in the acid precipitable radioactivity in the soluble fraction. The overall results of the study suggest that DMSO acts on polyribosommes indirectly through some unknown primary reaction with cell constitutents, and that the mode of action is such as to cause the release of ribosomes from messenger RNA (mRNA) rather than to prevent initiation of the ribosome-mRNA complex. Our data suggest that the effect may be selective. Finally, it is of interest that high concentrations of DMSO (above 8%) appear to have the opposite effect of lower concentrations of DMSO, i.e., they appear to "freeze" the ribosomes to mRNA.

Clones of Friend leukemia cells: differences in karyotypes and responsiveness to inducers of differentiation

Several clones of Friend leukemia cells have been established which differ in their chromosome composition. These cells also vary with regard to their responsiveness to DMSO, whereas all are responsive to butyric acid. Hence, there appears to be independent assortment of the ability of a cell line to respond to DMSO and to butyric acid, suggesting a different mechanism of action for each agent. Further, individual Friend cells possess the ability to simultaneously contain chloroacetate esterase and heme--two biochemical properties which have previously been believed to be mutually exclusive.

Inducers of Friend leukaemic cell differentiation in vitro--effects of in vivo administration

Studies were conducted of the in vivo therapeutic potential of compounds which induce the differentiation of Friend leukaemia cells (FLC) in vitro. DBA2/J mice were inoculated with Friend leukaemia cells grown in tissue culture and at various times thereafter were treated with either N-methylacetamide, dimethylacetamide, or tetramethylurea. While survival was only occasionally prolonged, in every study these agents significantly inhibited leukaemia cell proliferation in the spleen and to a lesser extent in the marrow. These agents had no effect on the rate of proliferation of FLC growing subcutaneously nor on the proliferation of myeloid leukaemia in RFMS mice. These studies indicate that the administration of inducing agents to mice bearing Friend leukaemia can alter the proliferation characteristics of the leukaemia cells and hence suggest that these agents may have therapeutic potential.