Cellular uptake and intracellular fate of antisense oligonucleotides

Deficits in memory and hippocampal long-term potentiation in mice with reduced calbindin D28K expression

The influx of calcium into the postsynaptic neuron is likely to be an important event in memory formation. Among the mechanisms that nerve cells may use to alter the time course or size of a spike of intracellular calcium are cytosolic calcium binding or "buffering" proteins. To consider the role in memory formation of one of these proteins, calbindin D28K, which is abundant in many neurons, including the CA1 pyramidal cells of the hippocampus, transgenic mice deficient in calbindin D28K have been created. These mice show selective impairments in spatial learning paradigms and fail to maintain long-term potentiation. These results suggest a role for calbindin D28K protein in temporally extending a neuronal calcium signal, allowing the activation of calcium-dependent intracellular signaling pathways underlying memory function.

Interactions of phosphodiester and phosphorothioate oligonucleotides with intestinal epithelial Caco-2 cells

PURPOSE

Oral bioavailability for antisense oligonucleotides has recently been reported but the mechanistic details are not known. The proposed oral delivery of nucleic acids will, therefore, require an understanding of the membrane binding interactions, cell uptake and transport of oligonucleotides across the human gastro-intestinal epithelium. In this initial study, we report on the cell-surface interactions of oligonucleotides with human intestinal cells.

METHODS

We have used the Caco-2 cell line as an in vitro model of the human intestinal epithelium to investigate the membrane binding interactions of 20-mer phosphodiester (PO) and phosphorothioate (PS) oligonucleotides.

RESULTS

The cellular association of both an internally [3H]-labelled and a 5'end [32P]-labelled PS oligonucleotide (3.0% at 0.4 microM extracellular concentration) was similar and was an order of magnitude greater than that of the 5'end [32P]-labelled PO oligonucleotide (0.2%) after 15 minutes incubation in these intestinal cells. The cellular association of PS was highly saturable with association being reduced to 0.9% at 5 microM whereas that of PO was less susceptible to competition (0.2% at 5 microM, 0.1% at 200 microM). Differential temperature-dependence was demonstrated; PS interactions were temperature-independent whereas the cellular association of PO decreased by 75% from 37 degrees C to 17 degrees C. Cell association of oligonucleotides was length and pH-dependent. A decrease in pH from 7.2 to 5.0 resulted in a 2- to 3-fold increase in cell-association for both backbone types. This enhanced association was not due to changes in lipophilicity as the octanol:aqueous buffer distribution coefficients remained constant over this pH range. The ability of NaCl washes to remove surface-bound PS oligonucleotides in a concentration-dependent manner suggests their binding may involve ionic interactions at the cell surface. Cell-surface washing with the proteolytic enzyme, Pronase, removed approximately 50% of the cell-associated oligonucleotide for both backbone types.

CONCLUSIONS

Binding to surface proteins seems a major pathway for binding and internalization for both oligonucleotide chemistries and appear consistent with receptor (binding protein)-mediated endocytosis. Whether this binding protein-mediated entry of oligonucleotides can result in efficient transepithelial transport, however, requires further study.

DNA triplex formation selectively inhibits granulocyte-macrophage colony-stimulating factor gene expression in human T cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hemopoietic growth factor that is expressed in activated T cells, fibroblasts, macrophages, and endothelial cells. Although GM-CSF does not appear to be essential for normal hemopoiesis, overexpression of GM-CSF has been implicated in the pathogenesis of some diseases such as myeloid leukemia and chronic inflammation. An NF-kappaB/Rel binding site within the GM-CSF promoter, termed the kappaB element appears to be important for controlling expression in reporter gene assays in response to a number of stimuli in T cells. We investigated oligonucleotide-directed triple helix formation across this regulatory sequence as a potential tool to inhibit GM-CSF gene transcription. A 15-base oligonucleotide, GM3, was targeted to a purine-rich region in the GM-CSF proximal promoter, which overlaps the kappaB element. Gel mobility shift assays and DNase I footprinting demonstrated that GM3 formed a sequence-specific collinear triplex with its double-stranded DNA target. Triplex formation by GM3 blocked recombinant and nuclear NF-kappaB proteins binding to the GM-CSF element. GM3 also caused selective inhibition of the human T-cell lymphotrophic virus-1 Tax transactivator-induced luciferase activity from a reporter construct driven by the GM-CSF promoter in Jurkat T cells. Finally, GM3 greatly reduced the concentration of endogenous GM-CSF mRNA induced by different stimuli in Jurkat T cells but did not affect interleukin 3 mRNA levels in the same cells. We conclude that the kappaB element in the GM-CSF promoter plays a central role in the transcriptional activation of the endogenous GM-CSF gene. Colinear triplex formation acts as a selective transcriptional repressor of the GM-CSF gene and may have potential therapeutic application in cases of undesirable overexpression of this protein.

Fate of cationic liposomes and their complex with oligonucleotide in vivo

The present studies describe the biodistribution of cationic liposomes and cationic liposome/oligonucleotide complex following intravenous injection into mice via the tail vein. (111)In-diethylenetriaminepentaacetic acid stearylamide ((111)In-DTPA-SA) was used as a lipid-phase radiolabel. Inclusion of up to 5 mol% DTPA-SA in liposomes composed of 3beta-(N-(N',N'-dimethylaminoethane)carbamoyl)cholesterol (DC-Chol) and dioleoylphosphatidylethanolamine (DOPE) did not influence liposome formation or size, nor the binding/uptake or fusion of the cationic liposomes with CHO cells in vitro. Moreover, nuclear delivery of oligonucleotide to CHO cells was unaffected by the probe. The biodistribution of liposomes with increasing concentration of DC-Chol (1:4-4:1, DC-Chol/DOPE, mol/mol) at 24 h post-injection revealed no dependence on lipid composition. Uptake was primarily by liver, and accumulation in spleen and skin was also observed. Comparatively little accumulation occurred in lung. Clearance of injected liposomes by liver was very rapid (approximately 84.5% of the injected dose by 7.5 h post-injection). Liposome uptake by liver and spleen were equally efficient in the dose range of 3.33 to 33.33 mg/kg body weight, yet possible saturation of liver uptake at a dose of 66.80 mg/kg may have allowed for increased spleen accumulation. Preincubation of cationic liposomes with phosphorothioate oligonucleotide induced a dramatic yet transient accumulation of the lipid in lung which gradually redistributed to liver. Similar results were observed when monitoring iodinated oligonucleotide in the complex. Immuno-histochemical studies revealed large aggregates of oligonucleotide within pulmonary capillaries at 15 min post-injection, suggesting the early accumulation in lung was due to embolism. Immuno-histochemical studies further revealed labeled oligonucleotide to be localized primarily to Kupffer cells at 24 h post-injection. Immuno-electron microscopy revealed localization of oligonucleotide primarily to the lumen of pulmonary capillaries at 15 min post-injection. Immuno-electron microscopy revealed localization of oligonucleotide primarily to the lumen of pulmonary capillaries at 15 min post-injection, and to phagocytic vacuoles of Kupffer cells at 24 h post-injection. By these methods, nuclear delivery of oligonucleotide in vivo was not observed. Increasing concentration of mouse serum inhibited cellular binding/uptake of cationic liposomes in vitro, without or with complexed oligonucleotide. We therefore postulate that interaction with plasma components, including opsonin(s), inhibits cellular uptake of the injected liposomes as well as the liposome/oligonucleotide complex, and mediates rapid uptake by Kupffer cells of the liver. These results are relevant to the design of cationic liposomes for efficient delivery of nucleic acid in vivo.

Repression of transforming growth factor beta 1 protein by antisense oligonucleotide-induced increase of adrenal cell differentiated functions

Transforming growth factor beta 1 (TGF beta 1) is a potent inhibitor of several differentiated functions in bovine adrenal fasciculata cells (BAC). In addition, these cells express and secrete this factor. To determine whether this peptide plays an autocrine role in BAC, cells were transfected with 10 microM unmodified sense (SON) or antisense (AON) oligonucleotide complementary to the translation initiation region of the TGF beta 1 mRNA in an attempt to inhibit TGF beta 1 protein synthesis. We investigated first, the cellular uptake, the stability, and the intracellular distribution of 32P-labeled TGF beta 1 AON and SON; and second, the effects of both oligonucleotides on BAC specific functions. We have demonstrated that in BAC, the TGF beta 1 AON uptake reached a plateau after 8 h of transfection (16% of the radioactivity added) and remained fairly constant for at least 24 h. In contrast, the uptake of TGF beta 1 SON reached a plateau after 2 h of transfection (8% of the radioactivity added), remained stable for only 3 h, and then declined. After 8 h of transfection, followed by 44 h of culture without oligonucleotides, the intracellular level of TGF beta 1 AON was still high with about 8% of the radioactivity added, whereas that of TGF beta 1 SON represented only 1.2%. Moreover, AON was present in the cytoplasmic and nuclear fractions, and it was hybridized in both compartments. However, TGF beta 1 SON was present mainly in the cytoplasmic fraction where it was not hybridized. Neither TGF beta 1 AON nor SON modified TGF beta 1 mRNA levels; however, TGF beta 1 AON, but not SON, caused the disappearance of TGF beta 1 immunoreactivity inside the cells. Finally, the steroidogenic responsiveness of BAC transfected with TGF beta 1 AON increased about 2-fold, and this was associated with a 2-fold increase of the mRNA levels of both cytochrome P450 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase. Neither TGF beta 1 SON nor a scrambled oligonucleotide containing the same number of G nucleotides as TGF beta 1 AON had any effect on these parameters. Thus, these studies demonstrate that TGF beta 1 has an autocrine inhibitory effect on BAC differentiated functions, an effect that can be overcome by TGF beta 1 AON.

Prevention of Restenosis by Local Drug Delivery

Local drug therapy for preventing restenosis after angioplasty has been investigated for over a decade. Biologically active agents ranging from drugs to genes can be delivered locally using a wide variety of catheters. Microspheres, liposomes, and polymers have been used to enhance drug retention at the delivery site. More recently stents have been investigated as devices to attain local drug delivery, either by coating with polymers, seeding with genetically modified cells or by using them as a source of local radiation. Though the best method of delivering agents locally remains undefined, this approach is likely to emerge as an essential mode of therapy in the near future.

Evaluation of adjuvants that enhance the effectiveness of antisense oligodeoxynucleotides

PURPOSE

A factor limiting the effectiveness of antisense (AS) deoxyoligonucleotides (ODNs) is inefficient transport to their sites of action in the cytoplasm and in the nucleus. The extent of ODN transfer from endosomes to cytosol seems to be an important determinant of ODN effects. Consequently, the development of compounds (adjuvants) that enhance endosome to cytosol transfer may be vital in AS ODN therapeutics.

METHODS

In this report, we evaluated compounds for their potential to enhance the effects of phosphorothioate ODNs. The test system used a CHO cell line expressing the enzyme chloramphenicol acetyl-transferase (CAT) under the control of an inducible promoter. Several potential endosomal disrupting adjuvants were screened, including: (a) fusogenic peptides; (b) a pH sensitive polymer; (c) polymeric dendrimers, (d) cationic liposomes and (e) a pH sensitive surfactant N-dodecyl 2-imidazole-propionate (DIP). ODN effects were evaluated at the protein level by quantitating levels of CAT.

RESULTS

The use of AS ODN in co-incubation with the GALA peptide, cationic liposomes or 5th generation dendrimers resulted in a 35-40% reduction in CAT expression. The mis-matched ODN had no effect on CAT expression. Only modest effects were observed with the other adjuvants. DIP did not increase ODN activity by itself; however, when the liposomal form was used a significant reduction (48%) in CAT activity was seen.

CONCLUSIONS

We found the fusogenic peptide GALA, dendrimers, as well as the liposomal form of DIP, could significantly enhance the effects of ODNs.

Interaction of oligodeoxynucleotides with mammalian cells

Many previous studies have demonstrated that antisense oligodeoxynucleotides (ODNs) bind to surface proteins in a manner compatible with receptor-mediated endocytosis and, unless specifically modified, are internalized into endosomes with little access to the cytoplasmic structures or to the nucleus. Reports vary as to the specific proteins involved in the mechanism, and this study examines the conditions of binding, some proteins that might contribute to the process, and whether changes in binding patterns occur during differentiation. Native gel electrophoresis was used to optimize the surface binding of a phosphorothioate end-capped 16-mer to T15 mouse fibroblast cells, and comparisons are made with some human epithelial tumor cell lines. Binding to individual proteins was visualized using SDS-PAGE and autoradiography. Binding at 4 degrees C was almost exclusively to a 46 kDa protein and decreased in the presence of an excess of unlabeled ODN and heparin but not ATP. Increasing the temperature of ODN binding from 4 degrees C to 37 degrees C for 10 minutes changed the binding pattern observed. ODN binding to the total cytoplasmic and membrane proteins immobilized on a membrane showed a greater number of binding proteins, the most prominent being one of 30 kDa. Examination of the effects of serum on binding were made using the human lung carcinoma cell line COR-L23, which can be grown in serum-free conditions. Serum starvation led to an increased total binding seen on native gels coinciding with increased binding to a 46 kDa protein. Demonstration that changes in binding proteins occur when cells differentiate was made using the premacrophage cell line THP-1. Differentiation of these cells increased the total ODN binding and appeared to initiate the synthesis of some new binding proteins, although binding to a 46 kDa protein was reduced.

Novel polyaminolipids enhance the cellular uptake of oligonucleotides

Two new polyaminolipids have been synthesized for the purpose of improving cellular uptake of oligonucleotides. The amphipathic compounds are conjugates of spermidine or spermine linked through a carbamate bond to cholesterol. The polyaminolipids are relatively nontoxic to mammalian cells. In tissue culture assays, using fluorescent-tagged or radiolabeled triple helix-forming oligonucleotides, spermine-cholesterol and spermidine-cholesterol significantly enhance cellular uptake of the oligomers in the presence of serum. Spermine-cholesterol is comparable with DOTMA/DOPE (a 1:1 (w/w) formulation of the cationic lipid N-[1-(2,3-dioleyloxy)-propyl]-N,N,N-trimethylammonium chloride (DOTMA) and the neutral lipid dioleylphosphatidylethanolamine (DOPE)) in increasing cellular uptake of oligonucleotides, while spermidine-cholesterol is more efficient. The internalized oligonucleotides are routed to the nucleus as early as 20 min after treatment, suggesting that the polyaminolipids increase the permeability of cellular membranes to oligonucleotides. At later times, much of the incoming oligonucleotides are sequestered within punctate cytoplasmic granules, presumably compartments of endosomal origin. Coadministration with polyaminolipids markedly improves the cellular stability of the oligonucleotides; more than 80% of the material can be recovered intact up to 24 h after addition to cells. In the absence of the polyaminolipids, nearly all of the material is degraded within 6 h. These data suggest that the new polyaminolipids may be useful for the delivery of nucleic acid-based therapeutics into cells.

Antisense phosphorothioate oligodeoxynucleotides: introductory concepts and possible molecular mechanisms of toxicity

Over the past 5 years or so, much attention has been given to the possible use of synthetic antisense oligonucleotide analogs as a new class of therapeutic agents that function by sequence-specific inhibition of genetic expression. The basic design concepts which underline this novel approach to drug discovery are briefly described herein, together with some of the chemical, biochemical, and pharmacological aspects of phosphorothioate oligodeoxynucleotides that are first-generation antisense compounds now under clinical investigation. Possible molecular mechanisms of toxicity for this class, and other structural types of antisense compounds are discussed with the hope of stimulating interest in future toxicological studies in this emerging area of drug development.

Effects of cellular pharmacology on drug distribution in tissues

The efficacy of targeted therapeutics such as immunotoxins is directly related to both the extent of distribution achievable and the degree of drug internalization by individual cells in the tissue of interest. The factors that influence the tissue distribution of such drugs include drug transport; receptor/drug binding; and cellular pharmacology, the processing and routing of the drug within cells. To examine the importance of cellular pharmacology, previously treated only superficially, we have developed a mathematical model for drug transport in tissues that includes drug and receptor internalization, recycling, and degradation, as well as drug diffusion in the extracellular space and binding to cell surface receptors. We have applied this "cellular pharmacology model" to a model drug/cell system, specifically, transferrin and the well-defined transferrin cycle in CHO cells. We compare simulation results to models with extracellular diffusion only or diffusion with binding to cell surface receptors and present a parameter sensitivity analysis. The comparison of models illustrates that inclusion of intracellular trafficking significantly increases the total transferrin concentration throughout much of the tissue while decreasing the penetration depth. Increasing receptor affinity or tissue receptor density reduces permeation of extracellular drug while increasing the peak value of the intracellular drug concentration, resulting in "internal trapping" of transferrin near the source; this could account for heterogeneity of drug distributions observed in experimental systems. Other results indicate that the degree of drug internalization is not predicted by the total drug profile. Hence, when intracellular drug is required for a therapeutic effect, the optimal treatment may not result from conditions that produce the maximal total drug distribution. Examination of models that include cellular pharmacology may help guide rational drug design and provide useful information for whole body pharmacokinetic studies.

Transient decrease in high blood pressure by in vivo transfer of antisense oligodeoxynucleotides against rat angiotensinogen

The renin-angiotensin system plays an important role in blood pressure regulation. Angiotensinogen, which is mainly produced in the liver, is a unique component of the renin-angiotensin system, because angiotensinogen is only known as a substrate for angiotensin I generation. It is unclear whether circulating angiotensinogen is a rate-limiting step in blood pressure regulation. Recent findings of genetic studies and analyses suggest that the angiotensinogen gene may be a candidate as a determinant of hypertension. To test the hypothesis that angiotensinogen may modulate blood pressure, we transfected antisense oligonucleotides against rat angiotensinogen into the rat liver via the portal vein using liposomes that contain viral agglutinins to promote fusion with target cells, a technique that has been reported to be highly efficient. Transfection of antisense oligonucleotides resulted in a transient decrease in plasma angiotensinogen levels in spontaneously hypertensive rats from day 1 to day 7 after the injection, consistent with the reduction of hepatic angiotensinogen mRNA. Plasma angiotensin II concentration was also decreased in rats transfected with antisense oligonucleotides. Moreover, a transient decrease in blood pressure from day 1 to day 4 was observed, whereas transfection of sense and scrambled oligonucleotides did not result in any changes in plasma angiotensinogen level, blood pressure, or angiotensinogen mRNA level. Overall, our results demonstrate that transfection of antisense oligonucleotides against rat angiotensinogen resulted in a transient decrease in the high blood pressure of spontaneously hypertensive rats, accompanied by a decrease in angiotensinogen and angiotensin II levels.(ABSTRACT TRUNCATED AT 250 WORDS)

C-fos mediates antipsychotic-induced neurotensin gene expression in the rodent striatum

The ubiquitous inducibility of the immediate-early gene c-fos in the central nervous system has led to the search for downstream genes which are regulated by its product, Fos. Recent evidence suggests that c-fos induction by a single injection of the classical antipsychotic haloperidol may contribute to the subsequent increase in neurotensin gene expression in the rodent striatum. Consistent with this proposal, in the present study haloperidol-induced Fos-like immunoreactivity and neurotensin/neuromedin N messenger RNA were found to be expressed by the same population of striatal neurons. Moreover, inhibition of haloperidol-induced c-fos expression by intrastriatal injection of antisense phosphorothioate oligodeoxynucleotides complimentary either to bases 109-126 or 127-144 of c-fos attenuated the subsequent increase in neurotensin/neuromedin N messenger RNA. However, injection of a sense phosphorothioate oligodeoxynucleotide corresponding to bases 127-144 of c-fos did not reduce haloperidol-induced c-fos or neurotensin/neuromedin N expression. Furthermore, constitutive expression of Jun-like immunoreactivity in the striatum was not reduced by either the sense or antisense phosphorothioate oligodeoxynucleotides. Similarly, the sense and antisense phosphorothioate oligodeoxynucleotide failed to reduce proenkephalin messenger RNA, which is located in the same striatal neurons that express haloperidol-induced neurotensin/neuromedin N messenger RNA, which is located in the same striatal neurons that express haloperidol-induced neurotensin/neuromedin N messenger RNA. Lastly, haloperidol-induced increases in nerve growth factor I-A-, JunB- and FosB-like immunoreactivity and fosB messenger RNA were not decreased by intrastriatal injection of either the sense or antisense phosphorothioate oligodeoxynucleotides. These results indicate that the antisense phosphorothioate oligodeoxynucleotides attenuated haloperidol-induced neurotensin/neuromedin N expression by selectively reducing c-fos expression and emphasize the potential importance of immediate-early gene induction in the mechanism of action of this antipsychotic drug.

Radiolabeling of methylphosphonate and phosphorothioate oligonucleotides and evaluation of their transport in everted rat jejunum sacs

PURPOSE

The therapeutic use of antisense oligonucleotides will likely involve their administration over protracted periods of time. The oral route of drug dosing offers many advantages over other possible routes when chronic drug administration is necessary. However, little is known about the potential for oligonucleotide uptake from the gastrointestinal tract. This issue is addressed in the current work.

METHODS

We have developed a simple procedure for radiolabeling oligonucleotides by reductive alkylation with 14C-formaldehyde. We have utilized this approach, as well as 5' addition of fluorophores, to prepare labeled methylphosphonate and phosphorothioate oligonucleotides for use in intestinal transport studies. An everted rat gut sac model was employed to compare the transport of oligonucleotides to that of model compounds whose permeation properties are better understood.

RESULTS

We demonstrate that both methylphosphonate and phosphorothioate oligonucleotides are passively transported across the intestinal epithelium, probably by a paracellular route. The rates of transport for both types of oligonucleotides were similar, and were significantly greater than that of the very high MW polymer blue dextran, but were lower than the transport rate of valproic acid, a low MW compound known to have high oral availability.

CONCLUSIONS

A significant degree of permeation of oligonucleotides across the gastrointestinal epithelium does occur, but it is still unclear whether this is sufficient to permit effective oral administration of oligonucleotides as drugs.

Antisense oligonucleotide-induced block of individual GABAA receptor alpha subunits in cultured visual cortex slices reduces amplitude of evoked inhibitory postsynaptic currents

Whole cell patch clamp recordings were made in layer II-IV from organotypic slices of rat primary visual cortex, explanted at postnatal day 6 and maintained in a serum-free medium. Neurons evinced current clamp characteristics typical for stellate cells. Between 7 and 21 days in culture, both glutamate- and GABA-mediated postsynaptic currents were observed. Long-term culturing in the presence of a degenerate 15-mer antisense oligonucleotide directed against the transcripts of all alpha subunits genes of the GABAA receptor resulted in a dose dependent reduction of evoked GABA synaptic currents. This reduction was maximal (80%) at 20 microM. A randomized control oligo had no effect. Evoked glutamatergic excitatory postsynaptic currents were unaffected following oligo treatment. A 15-mer antisense oligo directed against the alpha 1 subunit gave variable effects: in some cells the amplitude of evoked GABAergic inhibitory postsynaptic currents (IPSCs) was reduced by 50-75%, while in other cells recorded from the same slices, there was little or no effect. An antisense oligo, directed against the alpha 2 subunit, however, gave a consistent and robust 80% reduction of the amplitude of evoked IPSCs. A 15-mer 3-base mismatch oligo against alpha 2 had no effect. We conclude that the alpha 2 subunit functions in postsynaptic GABAA receptors located on or close to the cell bodies of stellate cells. The role of the alpha 1 subunit is less clear, but this subunit seems spatially differentiated. The in situ antisense oligo technique should provide further insight into the biophysical and pharmacological consequences of the subunit composition of ligand gated channels at functional synapses.

In vitro inhibition of murine IFN gamma production by phosphorothioate deoxyguanosine oligomers

Phosphorothioate (PT) oligonucleotides are designed as specific agents for antisense therapy although they have been reported to exert non-specific immunomodulatory effects. To elucidate further their actions, the effect of PT deoxyguanosine oligomers (S-oligo(dG)) on in vitro cytokine production by mouse splenocytes was studied. S-oligo(dG)20 inhibited production of INF gamma induced by Con A, E. coli DNA or the combination of PMA and calcium ionophore A23187. The diester analogue was inactive, and of PT homo-oligomers tested, S-oligo(dG)20 was the most active. PT compounds with as few as 5 dG residues could also block INF gamma production. These results indicate that base composition and length, as well as the PT backbone, contribute to the inhibition of INF gamma production and extend the range of immunomodulatory effects of PT compounds.

A deficiency of the small GTPase rab8 inhibits membrane traffic in developing neurons

One of the major activities of developing neurons is the transport of new membrane to the growing axon. Candidates for playing a key role in the regulation of this intense traffic are the small GTP-binding proteins of the rab family. We have used hippocampal neurons in culture and analyzed membrane traffic activity after suppressing the expression of the small GTP-binding protein rab8. Inhibition of protein expression was accomplished by using sequence-specific antisense oligonucleotides. While rab8 depletion resulted in the blockage of morphological maturation in 95% of the neurons, suppression of expression of another rab protein, rab3a, had no effect, and all neurons developed normal axons and dendrites. The impairment of neuronal maturation by rab8 antisense treatment was due to inhibition of membrane traffic. Thus, by using video-enhanced differential interference contrast microscopy, we observed in the rab8-depleted cells a dramatic reduction in the number of vesicles undergoing anterograde transport. Moreover, by incubating antisense-treated neurons with Bodipy-labeled ceramide, a fluorescent marker for newly formed exocytic vesicles, we observed fluorescence labeling restricted to the Golgi apparatus, whereas in control cells labeling was found also in the neurites. These results show the role of the small GTPase rab8 in membrane traffic during neuronal process outgrowth.

Uptake, intracellular distribution, and stability of oligodeoxynucleotide phosphorothioate by Schistosoma mansoni

The in vitro uptake, cellular distribution, efflux, stability, and toxicity levels of an oligodeoxynucleotide phosphorothioate (PS-oligonucleotide) have been studied in mature Schistosoma mansoni worms. The intracellular accumulation of 35S-labeled PS-oligonucleotide occurred roughly in proportion to the worm body mass over a wide concentration range, whether the worms were exposed singly or in mating pairs. Cellular uptake was dependent on the extracellular concentration. A minor fraction (13%) of the PS-oligonucleotide taken up by the worm accumulated in the surface tegumental coat. Most of the PS-oligonucleotide taken up localized in the cytosol (54%) and the nuclei-enriched (33%) fractions. In a time course study on adult worms in culture, oligonucleotide uptake was observed within the first 2 h and peaked at about 36 h. A decrease in the intracellular concentration of the PS-oligonucleotide was observed by 42 h. Analysis of the extracted oligonucleotides showed that PS-oligonucleotide was digested slowly. Efflux of the oligonucleotide was time and temperature dependent. Significant toxicity to the cultured worms did not occur until the PS-oligonucleotide concentration was over 8 mg/ml (1 mM).

Digoxigenin-labeled phosphorothioate oligonucleotides: a new tool for the study of cellular uptake

The mechanisms and intracellular pathways by which many oligonucleotide analogs enter cells to exert the desired antisense effects are not fully understood and remain a matter of debate. In this study, we describe the synthesis of 5'-digoxigenin-labeled phosphorothioate oligonucleotides and show their use to examine intracellular oligonucleotide distribution within Epstein-Barr virus-transformed B cells. Comparison of digoxigenin-labeled and fluorescein-labeled oligonucleotide distribution shows the same intracellular fate, suggesting that digoxigenin modification does not interfere with intracellular routing. Double immunofluorescence studied by conventional fluorescence and confocal microscopy with antibodies to the labeling molecule and to lysosome-associated membrane protein indicate that oligonucleotides mainly accumulate in the lysosomal compartment. Digoxigenin labeling offers an alternative to study oligonucleotide uptake and distribution by immunoelectron microscopy. Two different approaches have been studied: immunogold labeling in heavily fixed and resin-embedded cells and immunogold labeling in lightly fixed and cryoultramicrotomy processed cells. The results confirm the major lysosomal accumulation of digoxigenin-labeled oligonucleotides and demonstrate that the antigenic capacity of digoxigenin is not damaged by any of the procedures used. Therefore, the conjugation of the functionalized digoxigenin molecule at the 5' end of phosphorothioate oligonucleotides provides a new tool in the study of oligonucleotide uptake and intracellular distribution at both cellular and ultrastructural levels.

Antisense oligonucleotide to AT1 receptor mRNA inhibits central angiotensin induced thirst and vasopressin

Antisense oligodeoxynucleotides (AS-ODN) to AT1 receptor mRNA inhibit high blood pressure in Spontaneously Hypertensive Rats (SHR) when injected into the brain. The effect is presumably through inhibition of the actions of brain angiotensin II (Ang II). Central injection of Ang II elicits several physiological responses including release of vasopressin and motivation to drink. The angiotensin II type-I (AT1) receptor is located in brain regions which have been implicated in mediating these effects. Therefore we hypothesized that AS-ODN to AT1 mRNA would inhibit the drinking and AVP response to central administration of Ang II in adult male SHR. AS-ODN were constructed to bases +63 to +77 (15-mer) of the AT1 receptor RNA. 24 h after AS-ODN treatment (50 micrograms/4 microliters) (intracerebroventricularly, i.c.v.), the drinking response to Ang II (50 ng, i.c.v.) was significantly reduced in the SHR (P < 0.05). The drinking response to Ang II (i.c.v.) was also reduced in the Sprague-Dawley rats (P < 0.05). There was no reduction of water intake in the control animals treated with scrambled ODN (SC-ODN). Repeated injection of AS-ODN did not produce a greater reduction in drinking response. Arginine vasopressin (AVP) release to central Ang II was significantly decreased after AS-ODN treatment when compared to vehicle (P < 0.05) and to SC-ODN injections (P < 0.05). Radioligand binding assays of the hypothalamic block after AS-ODN treatment showed a significant decrease of AT1 receptor binding (P < 0.05). The results show that the antisense inhibition of brain AT1 receptor gene expression decreases the Ang II induced drinking and AVP release responses.

Pharmacokinetics of antisense oligodeoxyribonucleotides (cyclin B1 and CDC 2 kinase) in the vessel wall in vivo: enhanced therapeutic utility for restenosis by HVJ-liposome delivery

Using a highly efficient viral HVJ (hemagglutinating virus of Japan) liposome-mediated transfer method, we examined the cellular fate of antisense oligodeoxyribonucleotides (oligos) in the vessel wall in vivo. Direct transfer of unmodified FITC (fluorescein isothiocyanate)-labeled oligos into injured rat carotid arteries showed, localized in the medial layer, fluorescence that disappeared within 1 day. In contrast, transfection of unmodified FITC-oligos by the HVJ-liposome method showed, concentrated in the medial layer, high levels of fluorescence that were sustained for at least 1 week. Moreover, we demonstrated nuclear localization and accumulation of fluorescence in the vessel wall using this method. To examine the therapeutic utility of this method, we transferred antisense phosphorothioate oligos against cyclin B1- and CDC2 kinase-encoding genes into balloon-injured rat carotid artery as a potential therapy for experimental restenosis. Two weeks after transfection, antisense oligo treatment directed against either CDC2 kinase or cyclin B1 resulted in a partial, but significant, inhibition in neointima formation. In contrast, transfection of either sense or scrambled control oligos had no effect. Interestingly, co-transfection of antisense oligos against CDC2 kinase and cyclin B resulted in further inhibition of neointima formation, as compared to blockade of either gene target alone. These results demonstrate that: (i) the HVJ-liposome method enhances the half life and nuclear localization of antisense oligos in the vessel wall in vivo; and (ii) HVJ-mediated administration of antisense CDC2 kinase and cyclin B1 oligos produces a sustained inhibition of neointima formation after balloon angioplasty.

c-fos expression in the amygdala: in vivo antisense modulation and role in anxiety

1. The amygdaloid complex is a key structure in mechanisms of fear and anxiety. Expression of the immediate-early gene c-fos has been reported in the central nucleus of the amygdala following various stressors, but the functional role of this phenomenon has remained unknown. 2. c-fos expression was observed in the central nucleus when rats were subjected to a pharmacologically validated animal model of anxiety, the Vogel conflict test, but not after mere exposure to the test apparatus. Bilateral amygdala injection of a 15-mer phosphorothioate c-fos antisense oligodeoxynucleotide prior to testing blocked conflict-induced c-fos expression and had behavioral effects similar to those of established antianxiety drugs. 3. Separate experiments determined that antisense treatment did not affect conflict behavior by acting on shock thresholds or drinking motivation. 4. These findings provide evidence that neuronal activation and c-fos induction in the amygdala may be of importance for mechanisms of fear and anxiety.

Depletion of catalytic and regulatory subunits of protein kinase CK2 by antisense oligonucleotide treatment of neuroblastoma cells

1. The use of antisense oligonucleotides to inhibit expression of the genes coding for the catalytic (alpha/alpha') and regulatory (beta) subunits of protein kinase casein kinase 2 (CK2) has allowed study of the role of this enzyme in mouse neuroblastoma cells. 2. Selective depletion of catalytic (alpha/alpha') subunits results in the blocking of neuritogenesis. The depletion of catalytic subunits also affects the sorting of the regulatory (beta) subunit of CK2, as the absence of catalytic subunits prevents the translocation of the regulatory subunit to the nuclei. These results emphasize the existence of a control mechanism linking the expression and sorting of CK2 catalytic and regulatory subunits. 3. Selective depletion of the regulatory (beta) subunit of protein kinase CK2 by an specific antisense oligonucleotide causes partial inhibition of neurite extension.

Transport of oligonucleotides across natural and model membranes

Oligo- and polynucleotides can not diffuse through lipid membrane, however they are taken up by eukaryotic cells by endocytosis mediated by the nucleic acid specific receptors. The compounds find some way to escape from endosomes and reach nucleic acids in both cell nucleus and cytoplasm. Oligonucleotides bind to a few cell surface proteins which take part in the virus-cell interaction and in the development of immune response. Interaction of nucleic acids with cell surface proteins may play a role in development of some pathologies. The biological role of this interaction is unclear. Efficient delivery of oligonucleotides into eukaryotic cells can be achieved in some conditions by natural mechanisms and by using artificial carriers--membrane vehicles and cationic polymer micelles.

Electron micrographic studies of transport of oligodeoxynucleotides across eukaryotic cell membranes

Unmodified oligodeoxynucleotides (ODNs) were synthesized and tested for their ability to cross external eukaryotic cell membranes and to enter the cytosol and nucleus in tissue cultures. The ODNs were labeled with high-specific-activity [3H]thymidine (> or = 100 Ci/mmol), or [ alpha-32P]ATP or [ gamma-32P]ATP (300-1000 Ci/mmol; 1 Ci = 37 GBq), and the label was either in the central portion of the molecule or at the 3' or 5' end. The cells employed were for the most part 3T6 murine fibroblasts, grown in monolayers, either semiconfluent or confluent, but some experiments were carried out with chicken embryo fibroblasts or human HeLa cells. Parallel wells in the same experiment were prepared for electron microscopy or for cell fractionation and radioactivity assays. Electron microscopic autoradiography indicated that ODNs cross the external cell membrane, traverse the cytosol, and begin to enter the cell nucleus within a few seconds to 5 min at 37 degrees C in Dulbecco's medium without added serum. After 30-60 min of incubation with ODNs, abundant silver grains were observed at or just inside the nuclear membrane or well distributed across the nucleus, particularly in association with euchromatin. There was a paucity of silver grains associated with nucleoli. Cell entry of oligomer was related to cell cycling events and was energy dependent. Degradation of oligomer to monomers, with reincorporation into DNA, does not appear to explain these results. No sequestration of labeled oligomer in cytoplasmic vesicles en route from the exterior of the cell to the nucleus was observed. The observations are more suggestive of internalization of oligonucleotide by a mechanism as yet unclear or, alternatively, by a caveolar, potocytotic mechanism rather than by endocytosis.

Intimal hyperplasia after vascular injury is inhibited by antisense cdk 2 kinase oligonucleotides

The cell cycle regulatory enzyme, cdk (cyclin-dependent kinase) 2 kinase, is activated in the rat carotid artery after balloon angioplasty injury, and may mediate smooth muscle proliferation. To test the hypothesis that inhibition of the expression of this key enzyme can inhibit intimal hyperplasia, we studied the effect of antisense phosphorothioate oligodeoxynucleotides (ODN) against cdk 2 kinase administered by intraluminal delivery using hemagglutinating virus of Japan (HVJ)-liposome-mediated transfer. The specificity of antisense cdk 2 ODN was confirmed by the observation that mRNA level of cdk 2 kinase in injured vessels was markedly diminished by the antisense ODN treatment. At 2 wk after transfection, antisense cdk 2 ODN treatment (15 microM) resulted in a significant inhibition (60%) in neointima formation, compared with sense ODN-treated and untreated vessels. Since we have previously observed that cell division cycle 2 kinase mRNA was also activated after vascular injury, we administered the combination of antisense cdc 2 and cdk 2 ODN in this study. Antisense cdc 2 ODN alone (15 microM) only reduced intimal formation by 40%. Combined antisense treatment resulted in near complete inhibition of neointima formation. To understand the mechanism of the sustained effect of a single antisense ODN administration, we examined kinetics of ODN in the vessel wall. Using phosphorothioate FITC-labeled ODN, we transfected carotid artery using the HVJ-liposome method. Fluorescence localized immediately to the medial layer, and persisted up to 2 wk after transfection. These results demonstrate that a single intraluminal administration of antisense ODN directed to cell cycle regulatory genes (e.g., cdk 2 kinase) using the HVJ method can result in a sustained inhibition of neointima formation after balloon angioplasty in rat carotid injury model.

Lipid membrane permeability of 2'-modified derivatives of phosphorothioate oligonucleotides

Antisense oligonucleotides have the ability to inhibit gene expression in viral infections, malignancy, and other diseases. Even though much work has been accomplished with oligonucleotides demonstrating in vitro therapeutic effects, little work has been done to address how these molecules gain access to the cell. One of the plausible means of entrance could be through passive diffusion of the oligonucleotides through the cellular lipid bilayer. To enhance membrane permeability of oligonucleotides lipophilic moieties at the 2' position of the ribose ring have been added. To evaluate the effect of this modification, a liposome system was used. The oligonucleotides evaluated were a series composed of poly A 10mers phosphorothioates labeled at the 5' end with fluorescein and modified at the 2' position of the ribose ring with lipophilic alkyl chains ranging from methyl to nonyl. Efflux studies were accomplished by monitoring the appearance of the oligonucleotide in the incubation medium. There were modest but significant differences between the efflux half-life times of the 2'-modified compounds and the control compound. The values ranged from approximately 6 days for the control, unmodified compound to 4.6 days for the propyl modification. The nonyl derivative had a longer efflux half-life time (8.3 days) compared with the control, unmodified phosphorothioate oligonucleotide.

Corticotropin-releasing factor and neuropeptide Y: role in emotional integration

The amygdala complex integrates stressful stimuli and is critical in transducing their aversive value into autonomic, endocrine and behavioural responses. Stimulation within the amygdala complex produces signs of fear without a relevant external object, while lesions in this region abolish normal fear responses. In a manner characteristic of phylogenetically old limbic brain areas, the complex neurochemical anatomy of the amygdala involves a large number of phylogenetically old peptide mediators. The distribution and connectivity of these peptide systems have been extensively studied, but less is known about their functional role. Recent evidence suggests that two neuropeptides, corticotropin-releasing factor (CRF) and neuropeptide Y (NPY) exert a reciprocal regulation of responsiveness to stressful stimuli, possibly via an interaction of these two systems in the amygdala.

The role of the 5' untranslated region of eukaryotic messenger RNAs in translation and its investigation using antisense technologies

This chapter discusses the recent advances in the field of translational control and the possibility of applying the powerful antisense technology to investigate some of the unanswered questions, especially those pertaining to the role of the 5’untranslated region ( UTR) on translation initiation. Translational regulation is predominantly exerted during the initiation phase that is considered to be the rate-limiting step. Two types of translational regulation can be distinguished: global, in which the initiation rate of (nearly) all cellular messenger RNA (mRNA) is controlled and selective, in which the translation rate of specific mRNAs varies in response to the biological stimuli. In most cases of global regulation, control is exerted via the phosphorylation state of certain initiation factors, whereas only a few examples of selective regulation have been characterized well enough to define the underlying molecular events. Interestingly, cis-acting regulatory sequences, affecting translation initiation, have been found not only in the 5’UTRs of selectively regulated mRNAs, but also in the 3’UTRs. Thus, in addition to the protein encoding open reading frames, both the 5’ and 3’UTRs of mRNAs must be considered for their effect on translation.

Specific inhibition of endogenous neuropeptide Y synthesis in arcuate nucleus by antisense oligonucleotides suppresses feeding behavior and insulin secretion

Neuropeptide Y (NPY), which is synthesized in neurons of the arcuate nucleus (ARC) that project to different hypothalamic nuclei, is known to have potent effects on eating behavior and hormone secretion after hypothalamic administration. To test the hypothesis that endogenous NPY is essential for the normal expression of these responses, the present study used to unmodified antisense oligodeoxynucleotides (ODNs) to disrupt the synthesis of NPY in the ARC and to examine the impact of this disturbance on nutrient intake, as well as on circulating levels of insulin and the adrenal steroids, corticosterone and aldosterone. Brain-cannulated rats maintained on macronutrient diets were given daily, bilateral injections, over a 4-day period, of NPY antisense ODNs, sense ODNs or saline into the ARC. The NPY antisense ODNs produced a significant decline (-33% relative to sense ODNs and -40% relative to saline, P < 0.05) in NPY levels in this nucleus, without causing any direct neural damage. Peptide levels in other hypothalamic areas, namely, the paraventricular nucleus and medial preoptic nucleus, were not significantly affected. In association with this reduction in ARC NPY, the antisense-treated animals exhibited a significant decrease in feeding behavior measured during the first 90 min of the natural feeding cycle, as well as over the 24-h period. In the 90-min interval, both carbohydrate and fat intake were suppressed by 65-70% (P < 0.05, relative to both saline and sense ODNs control scores).(ABSTRACT TRUNCATED AT 250 WORDS)

Triplex-forming oligonucleotide binding represses transcription of the human c-erbB gene in glioma

Mixed purine-pyrimidine oligodeoxynucleotides were designed to form collinear DNA triplexes with pyrimidine-rich elements in the EGFR gene promoter. Their effects as mediators of human epidermal growth factor receptor (EGFR) gene transcription and subsequent gene expression were evaluated using human squamous cell carcinoma (A431) and human glioma cell line (U251MG and U87MG). Gel shift analysis indicated that the oligonucleotide forms a collinear triplex within the duplex Sp-1 binding site. An in vitro assay system revealed a correlation between triplex formation and the repression of EGFR transcription. We postulate that guanine residues are not always optimum in apposition to G-C pairs to form triple helices in the target. Site-specific oligodeoxynucleotides binding to a DNA duplex may serve as the basis for an alternative program of gene control in vitro.

Stimulation of murine lymphocyte proliferation by a phosphorothioate oligonucleotide with antisense activity for herpes simplex virus

To investigate further the immunological properties of nucleic acids, the mitogenicity of a phosphorothioate oligonucleotide (S-oligo 1082) with antisense activity for herpes simplex virus was tested. This compound stimulated proliferation and antibody production by murine lymphocytes in in vitro cultures. Proliferation was dose-dependent and unaffected by T cell depletion. Furthermore, inclusion of a non-mitogenic DNA in the medium did not block stimulation. Since 1082 does not have homology to a known gene involved in lymphocyte activation, these observations suggest that S-oligo antisense compounds may display non-specific activating effects, at least on murine B cells.

Cellular uptake of oligodeoxynucleotide phosphorothioates and their analogs

The uptake and intracellular distribution of oligonucleotide phosphorothioates (S-oligonucleotides) and their analogs by various cells lines were studied using internally 35S-labeled oligonucleotides. Intracellular accumulation starts in the first 2 hr and reaches a maximum at about 16 hr. A decrease of intracellular concentration of the S-oligonucleotide was observed after 16 hr, probably due to a significant efflux transport. Cellular uptake was dependent on the extracellular concentration. The intracellular concentration was significantly higher than that in the medium. The uptake and the intracellular distribution were different in the various cell lines studied. Comparative studies of the uptake of the S-oligonucleotide and various 3' end-modified S-oligonucleotides show that end modified S-oligonucleotides with a hydrophobic group significantly increases the uptake. The introduction of methylphosphonothioate linkages at the 3' end of the S-oligonucleotide also resulted in an increase in uptake.

Pharmacokinetics of an antisense phosphorothioate oligodeoxynucleotide against rev from human immunodeficiency virus type 1 in the adult male rat following single injections and continuous infusion

An antisense phosphorothioate oligodeoxynucleotide 27-mer complementary to the rev gene mRNA of the human immunodeficiency virus (HIV-1) was administered to rats through intravenous injections and subcutaneous infusions in order to investigate the disposition of this compound. In addition, nonlethal toxic responses of the rat were evaluated. A biphasic plasma clearance with t1/2 alpha of 20-25 min and t1/2 beta of 27-41 hr was observed. Single doses ranging from 35 to 3257 micrograms were examined, and the plasma concentration and area under the plasma concentration-time curve (AUC) were found to be directly proportional to the dose. Continuous subcutaneous infusion of 50 mg over 28 days was also examined. The oligonucleotide is completely eliminated in the urine over 3 days. Electrophoretic analysis demonstrated that the excreted compound has the same mobility and UV-absorbance profile as the administered compound. Measurement of accumulation and distribution into tissues revealed unique tissue-specific rates and extent of oligonucleotide movement into and out of tissues. Results of the chronic infusion study suggest that uptake into tissue is not saturated, even after 28 days of infusion. Analysis of blood plasma from oligonucleotide-treated animals shows a possible transient elevation in levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aspartate aminotransferase (AST), but not alkaline phosphatase (AP), gamma-glutamyltransferase (GT), and bilirubin. The data collectively support the potential utility of phosphorothioate oligonucleotides as therapeutic agents in vivo.

Influence of base composition on membrane binding and cellular uptake of 10-mer phosphorothioate oligonucleotides in Chinese hamster ovary (CHRC5) cells

A key problem in antisense therapeutics is the relatively poor cell uptake of oligonucleotides and subsequent transport to the cytoplasm and nucleus. Although the chemical characteristics of oligonucleotides seem likely to affect their uptake by cells, little is known about this issue. In this article we explore the effect of base composition on oligonucleotide uptake. We show that phosphorothioate homo-G oligomers have a distinctly greater cellular uptake than other phosphorothioate homooligomers. This is probably due to a greater initial association with the plasma membrane, because homo-G oligomers show the greatest binding to liposome membranes, when tested at physiological ionic strength. Under different buffer conditions appreciable differences in membrane binding to liposomes were detected for the various homooligonucleotides.

Protein transport to the dendritic plasma membrane of cultured neurons is regulated by rab8p

In the companion paper (Huber, L. A., S. W. Pimplikar, R. G. Parton, H. Virta, M. Zerial, and K. Simons. J. Cell Biol. 123:35-45) we reported that the small GTPase rab8p is involved in transport from the TGN to the basolateral plasma membrane in epithelia. In the present work we investigated the localization and function of rab8p in polarized hippocampal neurons. By immunofluorescence microscopy we found that rab8p localized preferentially in the somatodendritic domain, and was excluded from the axon. Double-labeling immunofluorescence showed that some of the rab8p co-localized in the dendrites with the Semliki Forest Virus glycoprotein E2 (SFV-E2). An antisense oligonucleotide approach was used to investigate the role of rab8p in dendritic transport of newly synthesized viral glycoproteins. Antisense oligonucleotides corresponding to the initiation region of the rab8 coding sequence were added to the cultured neurons for four days. This treatment resulted in a significant decrease in cellular levels of rab8p and transport of SFV-E2 from the cell body to the dendrites was significantly reduced. However, no effect was observed on axonal transport of influenza HA. From these results we conclude that rab8p is involved in transport of proteins to the dendritic surface in neurons.

The effect of transforming growth factor-beta 2-specific phosphorothioate-anti-sense oligodeoxynucleotides in reversing cellular immunosuppression in malignant glioma

This in vitro study was aimed at restitution of transforming growth factor (TGF)-beta 2-mediated suppression of T-lymphocyte activation within malignant gliomas. In early-passage tumor cell cultures of two glioblastomas (HTZ-153 and HTZ-209) and one malignant astrocytoma classified as World Health Organization Grade III (HTZ-243), autologous peripheral blood mononuclear cells were activated by interleukin-1 alpha and interleukin-2 in vitro (lymphokine-activated killer cells) and tested for cytotoxic and proliferative activity. In expression studies (Western blot and Northern hybridization) of all three tumors, TGF-beta could be detected at the protein and messenger ribonucleic acid (mRNA) levels. A polyclonal anti-TGF-beta neutralizing antibody did not enhance lymphocyte proliferation upon stimulation with tumor targets (3H-thymidine incorporation) and slightly stimulated lymphocyte cytotoxicity against autologous target cells. Preincubation of target cells for 12 hours with TGF-beta 2-specific phosphorothioate-anti-sense oligodeoxynucleotides (S-ODN's) did, however, enhance lymphocyte proliferation up to 2.5-fold and autologous tumor cytotoxicity up to 60%, compared to controls not treated with S-ODN's. Incubation of tumor cells with TGF-beta 2-specific S-ODN's resulted in decreased TGF-beta-specific immunoreactivity in cultured glioma cells, in reduced TGF-beta 2 protein concentration (Western blot), and in a change in the expression pattern of TGF-beta 2 mRNA's. These observations may have implications for in vivo and in vitro activation of a cellular immune response against autologous malignant glioma cells.