Delving into the reducing effects of the GABAB positive allosteric modulator, KK-92A, on alcohol-related behaviors in rats.

Recent studies have demonstrated the ability of the positive allosteric modulator (PAM) of the GABAB receptor (GABAB PAM), KK-92A, to suppress operant alcohol self-administration and reinstatement of alcohol seeking in selectively bred Sardinian alcohol-preferring (sP) rats. The present study was designed to scrutinize the suppressing effects of KK-92A on alcohol-related behaviors; to this end, four separate experiments were conducted to address just as many new research questions, some of which bear translational value. Experiment 1 found that 7-day treatment with KK-92A (0, 5, 10, and 20 mg/kg, intraperitoneally [i.p.]) effectively reduced alcohol intake in male sP rats exposed to the home-cage 2-bottle "alcohol (10% v/v) vs. water" choice regimen with 1 hour/day limited access, extending to excessive alcohol drinking the ability of KK-92A to suppress operant alcohol self-administration. Experiment 2 demonstrated that the ability of KK-92A to reduce lever-responding for alcohol was maintained also after acute, intragastric treatment (0, 20, and 40 mg/kg) in female sP rats trained to lever-respond for 15% (v/v) alcohol under the fixed ratio 5 schedule of reinforcement. In Experiment 3, acutely administered KK-92A (0, 5, 10, and 20 mg/kg, i.p.) dampened alcohol-seeking behavior in female sP rats exposed to a single session under the extinction responding schedule. Experiment 4 used a taste reactivity test to demonstrate that acute treatment with KK-92A (0 and 20 mg/kg, i.p.) did not alter either hedonic or aversive reactions to a 15% (v/v) alcohol solution in male sP rats, ruling out that KK-92A-induced reduction of alcohol drinking and self-administration could be due to alterations in alcohol palatability. Together, these results enhance the behavioral pharmacological profile of KK-92A and further strengthen the notion that GABAB PAMs may represent a novel class of ligands with therapeutic potential for treating alcohol use disorder.

Development of Partial Tolerance to the Suppressing Effect of the Positive Allosteric Modulator of the GABAB Receptor, KK-92A, on Alcohol Self-Administration in Rats.

AIMS: A recent study reported how acute treatment with KK-92A, a newly synthesized positive allosteric modulator (PAMs) of the GABAB receptor (GABAB PAMs), suppressed a series of alcohol-related behaviors, including operant oral alcohol self-administration, in selectively bred Sardinian alcohol-preferring (sP) rats. These findings lead to the addition of KK-92A to the long list of GABAB PAMs capable of reducing, after acute treatment, alcohol self-administration in rats. As a further step toward a more complete characterization of the anti-addictive properties of KK-92A, the present study was designed to assess the effect of repeated treatment with the compound on alcohol self-administration. METHODS: sP rats were trained to lever-respond for oral alcohol (15%, v/v) under the fixed ratio 5 (FR5) schedule of reinforcement. Once lever-responding behavior had stabilized, KK-92A (0, 5, 10 and 20 mg/kg, i.p.) was administered 30 min prior to 10 consecutive daily self-administration sessions (likewise occurring under the FR5 schedule). RESULTS: The first injection of KK-92A produced a dose-related suppression in number of lever-responses for alcohol and amount of self-administered alcohol. Magnitude of the suppressing effect of KK-92A decreased over the following two self-administration sessions and then tended to stabilize on continuation of treatment. Statistical significance at post hoc analysis was maintained only by the highest dose tested (20 mg/kg). CONCLUSIONS: These data suggest the development of partial tolerance to the reducing effect of repeatedly administered KK-92A on alcohol self-administration. The agonistic component of the ago-allosteric profile of KK-92A is discussed as the likely key element underlying the observed tolerance.

The Novel Positive Allosteric Modulator of the GABAB Receptor, KK-92A, Suppresses Alcohol Self-Administration and Cue-Induced Reinstatement of Alcohol Seeking in Rats.

Positive allosteric modulators (PAMs) of the GABAB receptor (GABAB PAMs) are of interest in the addiction field due to their ability to suppress several behaviors motivated by drugs of abuse. KK-92A is a novel GABAB PAM found to attenuate intravenous self-administration of nicotine and reinstatement of nicotine seeking in rats. This present study was aimed at extending to alcohol the anti-addictive properties of KK-92A. To this end, Sardinian alcohol-preferring rats were trained to lever-respond for oral alcohol (15% v/v) or sucrose (0.7% w/v) under the fixed ratio (FR) 5 (FR5) schedule of reinforcement. Once lever-responding behavior had stabilized, rats were exposed to tests with acutely administered KK-92A under FR5 and progressive ratio schedules of reinforcement and cue-induced reinstatement of previously extinguished alcohol seeking. KK-92A effect on spontaneous locomotor activity was also evaluated. Treatment with 10 and 20 mg/kg KK-92A suppressed lever-responding for alcohol, amount of self-administered alcohol, and breakpoint for alcohol. Treatment with 20 mg/kg KK-92A reduced sucrose self-administration. Combination of per se ineffective doses of KK-92A (2.5 mg/kg) and the GABAB receptor agonist, baclofen (1 mg/kg), reduced alcohol self-administration. Treatment with 5, 10, and 20 mg/kg KK-92A suppressed reinstatement of alcohol seeking. Only treatment with 80 mg/kg KK-92A affected spontaneous locomotor activity. These results demonstrate the ability of KK-92A to inhibit alcohol-motivated behaviors in rodents and confirm that these effects are common to the entire class of GABAB PAMs. The remarkable efficacy of KK-92A is discussed in terms of its ago-allosteric properties.

Accumulation of Silicon and Changes in Water Balance under Drought Stress in Brassica napus var. napus L.

The aim of this study was to investigate the accumulation of silicon in oilseed rape and to characterize the changes in chosen water balance parameters in response to drought. The following parameters were estimated: water content, osmotic and water potential, evapotranspiration, stomatal conductance and abscisic acid level under optimal and drought conditions. It was shown that oilseed rape plants accumulate silicon after its supplementation to the soil, both in the case of silicon alone and silicon together with iron. It was revealed that silicon (without iron) helps maintain constant water content under optimal conditions. While no silicon influence on osmotic regulation was observed, a transpiration decrease was detected under optimal conditions after silicon application. Under drought, a reduction in stomatal conductance was observed, but it was similar for all plants. The decrease in leaf water content under drought was accompanied by a significant increase in abscisic acid content in leaves of control plants and those treated with silicon together with iron. To sum up, under certain conditions, silicon is accumulated even in non-accumulator species, such as oilseed rape, and presumably improves water uptake under drought stress.

Drysdalin, a snake neurotoxin with higher affinity for soluble acetylcholine binding protein from Aplysia californica than from Lymnaea stagnalis.

Acetylcholine binding proteins (AChBPs), structural and functional surrogates of the extracellular binding domain of nicotinic acetylcholine receptor (nAChRs), in complex with various antagonists and agonists have provided detailed insights into the neurotransmitter binding site of nAChRs. The classical long-chain α-neurotoxins bungarotoxin (44-fold) and cobratoxin (7-fold) bind to Lymnaea stagnalis (Ls)-AChBP with higher affinity compared to Aplysia californica (Ac)-AChBP. In this study, we describe a novel long chain α-neurotoxin Drysdalin, which has higher binding affinity (7-fold) to Ac-AChBP when compared to Ls-AChBP. This suggests an involvement of different regions or modes of interaction of drysdalin, when compared to the bungarotoxin and cobratoxin. We also found that the C-terminal 24-amino acid residues of drysdalin are critical for the binding to Ac-AChBP and its removal caused ~90-fold reduction in affinity. Further to understand the interaction of drysdalin with Ac-AChBP, we studied the role of three non-conserved amino acid residues of drysdalin, namely Arg30, Leu34 and Ala37. Substitution of Arg30 with the conserved Phe residue caused a ~100-fold reduction, Leu34 with conserved Arg caused a ~6-fold reduction, whereas substitution of Ala37 with conserved Arg enhanced the binding by 3-fold. The dramatic influence of this carboxyl terminal sequence enriched in arginine and proline residues suggests that the toxin binding pose is influenced primarily by this extended sequence.

Synthesis, Pharmacological Characterization, and Structure-Activity Relationships of Noncanonical Selective Agonists for α7 nAChRs.

A lack of selectivity of classical agonists for the nicotinic acetylcholine receptors (nAChR) has prompted us to identify and develop a distinct scaffold of α7 nAChR-selective ligands. Noncanonical 2,4,6-substituted pyrimidine analogues were framed around compound 40 for a structure-activity relationship study. The new lead compounds activate selectively the α7 nAChRs with EC50's between 30 and 140 nM in a PNU-120596-dependent, cell-based calcium influx assay. After characterizing the expanded lead landscape, we ranked the compounds for rapid activation using Xenopus oocytes expressing human α7 nAChR with a two-electrode voltage clamp. This approach enabled us to define the molecular determinants governing rapid activation, agonist potency, and desensitization of α7 nAChRs after exposure to pyrimidine analogues, thereby distinguishing this subclass of noncanonical agonists from previously defined types of agonists (agonists, partial agonists, silent agonists, and ago-PAMs). By NMR, we analyzed pKa values for ionization of lead candidates, demonstrating distinctive modes of interaction for this landscape of ligands.

A versatile catalyst system for enantioselective synthesis of 2-substituted 1,4-benzodioxanes.

We report the synthesis of enantiomerically enriched 1,4-benzodioxanes containing alkyl, aryl, heteroaryl, and/or carbonyl substituents at the 2-position. The starting 1,4-benzodioxines were readily synthesized via ring closing metathesis using an efficient nitro-Grela catalyst at ppm levels. Excellent enantioselectivities of up to 99:1 er were obtained by using the versatile catalyst system [Ir(cod)Cl]2/BIDIME-dimer in the asymmetric hydrogenation of 2-substituted 1,4-benzodioxines. Furthermore, DFT calculations reveal that the selectivity of the process is controlled by the protonation step; and coordinating groups on the substrate may alter the interaction with the catalyst, resulting in a change in the facial selectivity.

Antitumor Humoral and T Cell Responses by Mucin-1 Conjugates of Bacteriophage Qß in Wild-type Mice.

Mucin-1 (MUC1) is one of the top ranked tumor associated antigens. In order to generate effective anti-MUC1 immune responses as potential anticancer vaccines, MUC1 peptides and glycopeptides have been covalently conjugated to bacteriophage Qß. Immunization of mice with these constructs led to highly potent antibody responses with IgG titers over one million, which are among the highest anti-MUC1 IgG titers reported to date. Furthermore, the high IgG antibody levels persisted for more than six months. The constructs also elicited MUC1 specific cytotoxic T cells, which can selectively kill MUC1 positive tumor cells. The unique abilities of Qß-MUC1 conjugates to powerfully induce both antibody and cytotoxic T cell immunity targeting tumor cells bode well for future translation of the constructs as anticancer vaccines.

KK-92A, a novel GABAB receptor positive allosteric modulator, attenuates nicotine self-administration and cue-induced nicotine seeking in rats.

RATIONALE: GABAB receptors (GABABR) play a critical role in GABAergic neurotransmission in the brain and are thought to be one of the most promising targets for the treatment of drug addiction. GABABR positive allosteric modulators (PAMs) have shown promise as potential anti-addictive therapies, as they lack the sedative and muscle relaxant properties of full GABAB receptor agonists such as baclofen. OBJECTIVES: The present study was aimed at developing novel, selective, and potent GABABR PAMs with efficacy on abuse-related effects of nicotine. RESULTS: We synthetized ~100 analogs of BHF177, a GABABR PAM that has been shown to inhibit nicotine taking and seeking, and tested their activity in multiple cell-based functional assays. Among these compounds, KK-92A displayed superior PAM properties at the GABABR. Interestingly, our results revealed the existence of pathway-selective differential modulation of GABABR signaling by the structurally related GABABR allosteric modulators BHF177 and KK-92A. In vivo, similarly to BHF177, KK-92A inhibited intravenous nicotine self-administration under both fixed- and progressive-ratio schedules of reinforcement in rats. In contrast to BHF177, KK-92A had no effect on food self-administration. Furthermore, KK-92A decreased cue-induced nicotine-seeking behavior without affecting food seeking. CONCLUSIONS: These results indicate that KK-92A is a selective GABABR PAM with efficacy in inhibition of the primary reinforcing and incentive motivational effects of nicotine, and attenuation of nicotine seeking, further confirming that GABABR PAMs may be useful antismoking medications.

T cells control the generation of nanomolar-affinity anti-glycan antibodies.

Vaccines targeting glycan structures at the surface of pathogenic microbes must overcome the inherent T cell-independent nature of immune responses against glycans. Carbohydrate conjugate vaccines achieve this by coupling bacterial polysaccharides to a carrier protein that recruits heterologous CD4 T cells to help B cell maturation. Yet they most often produce low- to medium-affinity immune responses of limited duration in immunologically fit individuals and disappointing results in the elderly and immunocompromised patients. Here, we hypothesized that these limitations result from suboptimal T cell help. To produce the next generation of more efficacious conjugate vaccines, we have explored a synthetic design aimed at focusing both B cell and T cell recognition to a single short glycan displayed at the surface of a virus-like particle. We tested and established the proof of concept of this approach for 2 serotypes of Streptococcus pneumoniae. In both cases, these vaccines elicited serotype-specific, protective, and long-lasting IgG antibodies of nanomolar affinity against the target glycans in mice. We further identified a requirement for CD4 T cells in the anti-glycan antibody response. Our findings establish the design principles for improved glycan conjugate vaccines. We surmise that the same approach can be used for any microbial glycan of interest.

Substituted 2-Aminopyrimidines Selective for α7-Nicotinic Acetylcholine Receptor Activation and Association with Acetylcholine Binding Proteins.

Through studies with ligand binding to the acetylcholine binding protein (AChBP), we previously identified a series of 4,6-substituted 2-aminopyrimidines that associate with this soluble surrogate of the nicotinic acetylcholine receptor (nAChR) in a cooperative fashion, not seen for classical nicotinic agonists and antagonists. To examine receptor interactions of this structural family on ligand-gated ion channels, we employed HEK cells transfected with cDNAs encoding three requisite receptor subtypes: α7-nAChR, α4ß2-nAChR, and a serotonin receptor (5-HT3AR), along with a fluorescent reporter. Initial screening of a series of over 50 newly characterized 2-aminopyrimidines with affinity for AChBP showed only two to be agonists on the α7-nAChR below 10 µM concentration. Their unique structural features were incorporated into design of a second subset of 2-aminopyrimidines yielding several congeners that elicited α7 activation with EC50 values of 70 nM and Kd values for AChBP in a similar range. Several compounds within this series exhibit specificity for the α7-nAChR, showing no activation or antagonism of α4ß2-nAChR or 5-HT3AR at concentrations up to 10 µM, while others were weaker antagonists (or partial agonists) on these receptors. Analysis following cocrystallization of four ligand complexes with AChBP show binding at the subunit interface, but with an orientation or binding pose that differs from classical nicotinic agonists and antagonists and from the previously analyzed set of 2-aminopyrimidines that displayed distinct cooperative interactions with AChBP. Orientations of aromatic side chains of these complexes are distinctive, suggesting new modes of binding at the agonist-antagonist site and perhaps an allosteric action for heteromeric nAChRs.

Chemical Synthesis of GM2 Glycans, Bioconjugation with Bacteriophage Qß, and the Induction of Anticancer Antibodies.

The development of carbohydrate-based antitumor vaccines is an attractive approach towards tumor prevention and treatment. Herein, we focused on the ganglioside GM2 tumor-associated carbohydrate antigen (TACA), which is overexpressed in a wide range of tumor cells. GM2 was synthesized chemically and conjugated with a virus-like particle derived from bacteriophage Qß. Although the copper-catalyzed azide-alkyne cycloaddition reaction efficiently introduced 237 copies of GM2 per Qß, this construct failed to induce significant amounts of anti-GM2 antibodies compared to the Qß control. In contrast, GM2 immobilized on Qß through a thiourea linker elicited high titers of IgG antibodies that recognized GM2-positive tumor cells and effectively induced cell lysis through complement-mediated cytotoxicity. Thus, bacteriophage Qß is a suitable platform to boost antibody responses towards GM2, a representative member of an important class of TACA: the ganglioside.

Significant Impact of Immunogen Design on the Diversity of Antibodies Generated by Carbohydrate-Based Anticancer Vaccine.

Development of an effective vaccine targeting tumor associated carbohydrate antigens (TACAs) is an appealing approach toward tumor immunotherapy. While much emphasis has been typically placed on generating high antibody titers against the immunizing antigen, the impact of immunogen design on the diversity of TACA-specific antibodies elicited has been overlooked. Herein, we report that the immunogen structure can significantly impact the breadth and the magnitude of humoral responses. Vaccine constructs that induced diverse TACA-binding antibodies provided much stronger recognition of a variety of Tn positive tumor cells. Optimization of the breadth of the antibody response led to a vaccine construct that demonstrated long lasting efficacy in a mouse tumor model. After challenged with the highly aggressive TA3Ha cells, mice immunized with the new construct exhibited a statistically significant improvement in survival relative to controls (0% vs 50% survival; p < 0.0001). Furthermore, the surviving mice developed long-term immunity against TA3Ha. Thus, both the magnitude and the breadth of antibody reactivity should be considered when designing TACA-based antitumor vaccines.

The GABA(B) receptor positive modulator BHF177 attenuated anxiety, but not conditioned fear, in rats.

GABAB (γ-aminobutyric acid B) receptors may be a therapeutic target for anxiety disorders. Here we characterized the effects of the GABAB receptor positive allosteric modulator (PAM) BHF177 on conditioned and unconditioned physiological responses to threat in the light-enhanced startle (LES), stress-induced hyperthermia, and fear-potentiated startle (FPS) procedures in rats. The effects of BHF177 on LES were compared with those of the GABAB receptor agonists baclofen and CGP44532, and the positive control buspirone, a 5-HT1A receptor partial agonist with anxiolytic activity in humans. Baclofen (0.4, 0.9 and 1.25 mg/kg) and CGP44532 (0.065, 0.125 and 0.25 mg/kg) administration had significant sedative, but not anxiolytic, activity reflected in overall decrease in the startle response in the LES tests. BHF177 (10, 20 and 40 mg/kg) had no effect on LES, nor did it produce an overall sedative effect. Interesting, however, when rats were grouped by high and low LES responses, BHF177 had anxiolytic-like effects only on LES in high, but not low, LES responding rats. BHF177 also blocked stress-induced hyperthermia, but had no effect on conditioned fear responses in the FPS test. Buspirone (1 and 3 mg/kg) had an anxiolytic-like profile in both LES and FPS tests. These results indicate that BHF177 may specifically attenuate unconditioned anxiety in individuals that exhibit a high anxiety state, and has fewer sedative effects than direct agonists. Thus, BHF177 or other GABAB receptor PAMs may be promising compounds for alleviating increased anxiety seen in various psychiatric disorders with a superior side-effect profile compared to GABAB receptor agonists.

Structural basis for cooperative interactions of substituted 2-aminopyrimidines with the acetylcholine binding protein.

The nicotinic acetylcholine receptor (nAChR) and the acetylcholine binding protein (AChBP) are pentameric oligomers in which binding sites for nicotinic agonists and competitive antagonists are found at selected subunit interfaces. The nAChR spontaneously exists in multiple conformations associated with its activation and desensitization steps, and conformations are selectively stabilized by binding of agonists and antagonists. In the nAChR, agonist binding and the associated conformational changes accompanying activation and desensitization are cooperative. AChBP, which lacks the transmembrane spanning and cytoplasmic domains, serves as a homology model of the extracellular domain of the nAChRs. We identified unique cooperative binding behavior of a number of 4,6-disubstituted 2-aminopyrimidines to Lymnaea AChBP, with different molecular variants exhibiting positive, nH > 1.0, and negative cooperativity, nH < 1.0. Therefore, for a distinctive set of ligands, the extracellular domain of a nAChR surrogate suffices to accommodate cooperative interactions. X-ray crystal structures of AChBP complexes with examples of each allowed the identification of structural features in the ligands that confer differences in cooperative behavior. Both sets of molecules bind at the agonist-antagonist site, as expected from their competition with epibatidine. An analysis of AChBP quaternary structure shows that cooperative ligand binding is associated with a blooming or flare conformation, a structural change not observed with the classical, noncooperative, nicotinic ligands. Positively and negatively cooperative ligands exhibited unique features in the detailed binding determinants and poses of the complexes.

Boosting immunity to small tumor-associated carbohydrates with bacteriophage qß capsids.

The development of an effective immunotherapy is an attractive strategy toward cancer treatment. Tumor associated carbohydrate antigens (TACAs) are overexpressed on a variety of cancer cell surfaces, which present tempting targets for anticancer vaccine development. However, such carbohydrates are often poorly immunogenic. To overcome this challenge, we show here that the display of a very weak TACA, the monomeric Tn antigen, on bacteriophage Qß virus-like particles elicits powerful humoral responses to the carbohydrate. The effects of adjuvants, antigen display pattern, and vaccine dose on the strength and subclasses of antibody responses were established. The local density of antigen rather than the total amount of antigen administered was found to be crucial for induction of high Tn-specific IgG titers. The ability to display antigens in an organized and high density manner is a key advantage of virus-like particles such as Qß as vaccine carriers. Glycan microarray analysis showed that the antibodies generated were highly selective toward Tn antigens. Furthermore, Qß elicited much higher levels of IgG antibodies than other types of virus-like particles, and the IgG antibodies produced reacted strongly with the native Tn antigens on human leukemia cells. Thus, Qß presents a highly attractive platform for the development of carbohydrate-based anticancer vaccines.

Comparison of the effects of the GABAB receptor positive modulator BHF177 and the GABAB receptor agonist baclofen on anxiety-like behavior, learning, and memory in mice.

γ-Aminobutyric acid B (GABAB) receptor activation is a potential therapeutic approach for the treatment of drug addiction, pain, anxiety, and depression. However, full agonists of this receptor induce side-effects, such as sedation, muscle relaxation, tolerance, and cognitive disruption. Positive allosteric modulators (PAMs) of the GABAB receptor may have similar therapeutic effects as agonists with superior side-effect profiles. The present study behaviorally characterized N-([1R,2R,4S]-bicyclo[2.2.1]hept-2-yl)-2-methyl-5-(4-[trifluoromethyl]phenyl)-4-pyrimidinamine (BHF177), a GABAB receptor PAM, in mouse models of anxiety-like behavior, learning and memory. In addition, the effects of BHF177 were compared with the agonist baclofen. Unlike the anxiolytic chlordiazepoxide, baclofen (0.5, 1.5, and 2.5 mg/kg, intraperitoneally) and BHF177 (10, 20, and 40 mg/kg, orally) had no effect on anxiety-like behavior in the elevated plus maze, light/dark box, or Vogel conflict test. Baclofen increased punished drinking in the Vogel conflict test, but this effect may be attributable to the analgesic actions of baclofen. At the highest dose tested (2.5 mg/kg), baclofen-treated mice exhibited sedation-like effects (i.e., reduced locomotor activity) across many of the tests, whereas BHF177-treated mice exhibited no sedation-like effects. BHF177 exhibited pro-convulsion properties only in mice, but not in rats, indicating that this effect may be species-specific. At doses that were not sedative or pro-convulsant, baclofen and BHF177 had no selective effects on fear memory retrieval in contextual and cued fear conditioning or spatial learning and memory in the Barnes maze. These data suggest that BHF177 has little sedative activity, no anxiolytic-like profile, and minimal impairment of learning and memory in mice.

Design, Synthesis, and in Vitro Evaluation of Novel Aminomethyl-pyridines as DPP-4 Inhibitors.

A collection of novel aminomethyl-pyridines was designed, synthesized, and investigated as potential inhibitors of DPP-4. Optimization of the screening hit afforded a number of 5-aminomethyl-pyridines with inhibitory activity in the nanomolar range. Selected DPP-4 inhibitors were further evaluated for their selectivity over the closely related peptidase DPP-8. 5-Aminomethyl-4-(2,4-dichloro-phenyl)-6-methyl-pyridine-2-carboxylic acid cyanomethyl-amide showed high potency and excellent DPP-4 selectivity [IC50: 10 (DPP-4) and 6600 nM (DPP-8)] and no toxicity in mammalian cell culture.

The effectiveness of high-resolution-comparative genomic hybridization in detecting the most common chromosomal abnormalities in pediatric myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) are a diverse and heterogeneous group of clonal and potentially malignant bone marrow (BM) disorders. The up-to-date used criteria are the ones proposed by the French-American-British (FAB) group in 1982, the World Health Organization (WHO) classification, and a new, recently presented classification: categories cytology cytogenetics (CCC) system or 2003 WHO classification scheme. Comparative genomic hybridization (CGH) is a technique that permits the detection of chromosomal imbalances within a "one step" analysis. In our study, we present 5 cases of MDS and 4 cases of acute myelogenous leukemia (AML). By means of high-resolution CGH (HR-CGH) analysis, we were able to detect DNA copy number alterations in 8 out of 9 samples. The changes were as follows: -7, -Y, del(5)(q33q34), del(11)(q22q24), del(5p), del(9)(q21q31), nullisomy X, and +8. In 5/9 cases the HR-CGH data were highly comparable with conventional cytogenetics and interphase/metaphase fluorescence in situ hybridization findings. Additionally, in 3 BM samples the HR-CGH revealed the presence of changes that had not been detected by conventional cytogenetics: del(5p), del(5)(q33q34), del(9)(q21q31), and nullisomy X. The high effectiveness, specificity, and sensitivity of this method are in concordance with the conventional cytogenetics and FISH findings and the ability to detect new changes.