Serotonergic modulation in neuropathy induced by oxaliplatin: Effect on the 5HT(2C) receptor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Encapsulation of paclitaxel into a bio-nanocomposite. a study combining inelastic neutron scattering to thermal analysis and infrared spectroscopy

The anticancer drug paclitaxel was encapsulated into a bio-nanocomposite formed by magnetic nanoparticles, chitosan and apatite. The aim of this drug carrier is to provide a new perspective against breast cancer. The dynamics of the pure and encapsulated drug were investigated in order to verify possible molecular changes caused by the encapsulation, as well as to follow which interactions may occur between paclitaxel and the composite. Fourier transformed infrared spectroscopy, thermal analysis, inelastic and quasi-elastic neutron scattering experiments were performed. These very preliminary results suggest the successful encapsulation of the drug.

Evaluation of mutagenicity and metabolism-mediated cytotoxicity of the naphthoquinone 5-methoxy-3,4-dehydroxanthomegnin from Paepalanthus latipes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Identifying regulational alterations in gene regulatory networks by state space representation of vector autoregressive models and variational annealing

Background: In the analysis of effects by cell treatment such as drug dosing, identifying changes on gene network structures between normal and treated cells is a key task. A possible way for identifying the changes is to compare structures of networks estimated from data on normal and treated cells separately. However, this approach usually fails to estimate accurate gene networks due to the limited length of time series data and measurement noise. Thus, approaches that identify changes on regulations by using time series data on both conditions in an efficient manner are demanded. Methods: We propose a new statistical approach that is based on the state space representation of the vector autoregressive model and estimates gene networks on two different conditions in order to identify changes on regulations between the conditions. In the mathematical model of our approach, hidden binary variables are newly introduced to indicate the presence of regulations on each condition. The use of the hidden binary variables enables an efficient data usage; data on both conditions are used for commonly existing regulations, while for condition specific regulations corresponding data are only applied. Also, the similarity of networks on two conditions is automatically considered from the design of the potential function for the hidden binary variables. For the estimation of the hidden binary variables, we derive a new variational annealing method that searches the configuration of the binary variables maximizing the marginal likelihood. Results: For the performance evaluation, we use time series data from two topologically similar synthetic networks, and confirm that our proposed approach estimates commonly existing regulations as well as changes on regulations with higher coverage and precision than other existing approaches in almost all the experimental settings. For a real data application, our proposed approach is applied to time series data from normal Human lung cells and Human lung cells treated by stimulating EGF-receptors and dosing an anticancer drug termed Gefitinib. In the treated lung cells, a cancer cell condition is simulated by the stimulation of EGF-receptors, but the effect would be counteracted due to the selective inhibition of EGF-receptors by Gefitinib. However, gene expression profiles are actually different between the conditions, and the genes related to the identified changes are considered as possible off-targets of Gefitinib. Conclusions: From the synthetically generated time series data, our proposed approach can identify changes on regulations more accurately than existing methods. By applying the proposed approach to the time series data on normal and treated Human lung cells, candidates of off-target genes of Gefitinib are found. According to the published clinical information, one of the genes can be related to a factor of interstitial pneumonia, which is known as a side effect of Gefitinib.

Antimicrobial Activity of Essential Oils against Streptococcus mutans and their Antiproliferative Effects

This study aimed to evaluate the activity of essential oils (EOs) against Streptococcus mutans biofilm by chemically characterizing their fractions responsible for biological and antiproliferative activity. Twenty EO were obtained by hydrodistillation and submitted to the antimicrobial assay (minimum inhibitory (MIC) and bactericidal (MBC) concentrations) against S. mutans UA159. Thin-layer chromatography and gas chromatography/mass spectrometry were used for phytochemical analyses. EOs were selected according to predetermined criteria and fractionated using dry column; the resulting fractions were assessed by MIC and MBC, selected as active fractions, and evaluated against S. mutans biofilm. Biofilms formed were examined using scanning electron microscopy. Selected EOs and their selected active fractions were evaluated for their antiproliferative activity against keratinocytes and seven human tumor cell lines. MIC and MBC values obtained for EO and their active fractions showed strong antimicrobial activity. Chemical analyses mainly showed the presence of terpenes. The selected active fractions inhibited S. mutans biofilm formation (P < 0.05) did not affect glycolytic pH drop and were inactive against keratinocytes, normal cell line. In conclusion, EO showed activity at low concentrations, and their selected active fractions were also effective against biofilm formed by S. mutans and human tumor cell lines.

Gastrin-releasing peptide receptor (GRPR) mediates chemotaxis in neutrophils

Neutrophil migration to inflamed sites is crucial for both the initiation of inflammation and resolution of infection, yet these cells are involved in perpetuation of different chronic inflammatory diseases. Gastrin-releasing peptide (GRP) is a neuropeptide that acts through G protein coupled receptors (GPCRs) involved in signal transmission in both central and peripheral nervous systems. Its receptor, gastrin-releasing peptide receptor (GRPR), is expressed by various cell types, and it is overexpressed in cancer cells. RC-3095 is a selective GRPR antagonist, recently found to have antiinflammatory properties in arthritis and sepsis models. Here we demonstrate that i.p. injection of GRP attracts neutrophils in 4 h, and attraction is blocked by RC-3095. Macrophage depletion or neutralization of TNF abrogates GRP-induced neutrophil recruitment to the peritoneum. In vitro, GRP-induced neutrophil migration was dependent on PLC-beta 2, PI3K, ERK, p38 and independent of G alpha i protein, and neutrophil migration toward synovial fluid of arthritis patients was inhibited by treatment with RC-3095. We propose that GRPR is an alternative chemotactic receptor that may play a role in the pathogenesis of inflammatory disorders.

Development of Cationic Solid Lipid Nanoparticles with Factorial Design-Based Studies for Topical Administration of Doxorubicin

Topical chemotherapy using doxorubicin, a powerful anticancer drug, can be used as an alternative with reduced systemic toxicity when treating skin cancer. The aim of the present work was to use factorial design-based studies to develop cationic solid lipid nanoparticles containing doxorubicin; further investigations into the influence of these particles on the drug's cytotoxicity and cellular uptake in B16F10 murine melanoma cells were performed. A 3(2) full factorial design was applied for two different lipid phases; one phase used stearic acid and the other used a 1:2 mixture of stearic acid and glyceryl behenate. The two factors investigated included the ratio between the lipid and the water phase and the ratio between the surfactant (poloxamer) and the co-surfactant (cetylpyridinium chloride). It was observed that the studied factors did not affect the mean diameter or the polydispersity of the obtained nanoparticles; however, they did significantly affect the zeta potential values. Optimised formulations with particle sizes ranging from 251 to 306 nm and positive zeta potentials were selected for doxorubicin incorporation. High entrapment efficiencies were achieved (97%) in formulations with higher amounts of stearic acid, suggesting that cationic charges on doxorubicin molecules may interact with the negative charges in stearic acid. Melanoma culture cell experiments showed that cationic solid lipid nanoparticles without drug were not cytotoxic to melanoma cells. The encapsulation of doxorubicin significantly increased cytotoxicity, indicating the potential of these nanoparticles for the treatment of skin cancer.

Populene D Analogues: Design, Concise Synthesis and Antiproliferative Activity

An efficient and concise synthesis of nine populene D analogues was performed using an iodine-catalyzed Prins cyclization as the key transformation. The antiproliferative activity of these new pyrans against several cancer cell lines was then investigated. Among them, an isochromene with moderate activity (mean logGI(50) = 0.91) was found. Additionally, compounds with selectivity toward the tumor cell lines NCI-ADR/RES, OVCAR-3, and HT29 were discovered.

Antiproliferative activity of Eremanthus crotonoides extracts and centratherin demonstrated in brain tumor cell lines

The genus Eremanthus is recognized by the predominance of sesquiterpene lactones from the furanoheliangolide type, a class of substances extensively tested against cancer cell lines. Thus, the species E. crotonoides (DC.) Sch. Bip., Asteraceae, obtained on "restinga" vegetation was evaluated against U251 and U87-MG glioma cell lines using the MTT colorimetric assay. Dichloromethane fraction was cytotoxic to both glioblastoma multiforme cell lines. We then conducted UPLC-PDA-ESI-MS/MS analysis of the dichloromethane fraction, which allowed the identification of the sesquiterpene lactones centratherin and goyazensolide. The isolation of centratherin was performed using chromatographic techniques and the identification of this substance was confirmed according to NMR data. Cytotoxic activity of centratherin alone was also evaluated against both U251 and U87-MG cells, which showed IC50 values comparable with those obtained for the commercial anticancer drug doxorubicin. All the tested samples showed cytotoxic activity against glioblastoma multiforme cells which suggests that E. crotonoides extracts may be important sources of antiproliferative substances and that the centratherin may serve as prototype for developing new antiglioblastoma drugs.

Ruolo dell'Enantiomero (R)-9-HSA nel controllo della proliferazione in una linea di Adenocarcinoma del Colon umano

9-hydroxystearic acid (9-HSA) is an endogenous lipoperoxidation product and its administration to HT29, a colon adenocarcinoma cell line, induced a proliferative arrest in G0/G1 phase mediated by a direct activation of the p21WAF1 gene, bypassing p53. We have previously shown that 9-HSA controls cell growth and differentiation by inhibiting histone deacetylase 1 (HDAC1) activity, showing interesting features as a new anticancer drug. The interaction of 9-HSA with the catalytic site of the 3D model has been tested with a docking procedure: noticeably, when interacting with the site, the (R)-9-enantiomer is more stable than the (S) one. Thus, in this study, (R)- and (S)-9-HSA were synthesized and their biological activity tested in HT29 cells. At the concentration of 50 M (R)-9-HSA showed a stronger antiproliferative effect than the (S) isomer, as indicated by the growth arrest in G0/G1. The inhibitory effect of (S)-9-HSA on HDAC1, HDAC2 and HDAC3 activity was less effective than that of the (R)-9-HSA in vitro, and the inhibitory activity of both the (R)- and the (S)-9-HSA isomer, was higher on HDAC1 compared to HDAC2 and HDAC3, thus demonstrating the stereospecific and selective interaction of 9-HSA with HDAC1. In addition, histone hyperacetylation caused by 9-HSA treatment was examined by an innovative HPLC/ESI/MS method. Analysis on histones isolated from control and treated HT29 confirmed the higher potency of (R)-9-HSA compared to (S)-9-HSA, severely affecting H2A-2 and H4 acetylation. On the other side, it seemed of interest to determine whether the G0/G1 arrest of HT29 cell proliferation could be bypassed by the stimulation with the growth factor EGF. Our results showed that 9-HSA-treated cells were not only prevented from proliferating, but also showed a decreased [3H]thymidine incorporation after EGF stimulation. In this condition, HT29 cells expressed very low levels of cyclin D1, that didn’t colocalize with HDAC1. These results suggested that the cyclin D1/HDAC1 complex is required for proliferation. Furthermore, in the effort of understanding the possible mechanisms of this effect, we have analyzed the degree of internalization of the EGF/EGFR complex and its interactions with HDAC1. EGF/EGFR/HDAC1 complex quantitatively increases in 9-HSA-treated cells but not in serum starved cells after EGF stimulation. Our data suggested that 9-HSA interaction with the catalytic site of the HDAC1 disrupts the HDAC1/cyclin D1 complex and favors EGF/EGFR recruitment by HDAC1, thus enhancing 9-HSA antiproliferative effects. In conclusion 9-HSA is a promising HDAC inhibitor with high selectivity and specificity, capable of inducing cell cycle arrest and histone hyperacetylation, but also able to modulate HDAC1 protein interaction. All these aspects may contribute to the potency of this new antitumor agent.

Transcriptional functions of DNA Topoisomerases at a genome-wide scale and a single gene levels

The DNA topology is an important modifier of DNA functions. Torsional stress is generated when right handed DNA is either over- or underwound, producing structural deformations which drive or are driven by processes such as replication, transcription, recombination and repair. DNA topoisomerases are molecular machines that regulate the topological state of the DNA in the cell. These enzymes accomplish this task by either passing one strand of the DNA through a break in the opposing strand or by passing a region of the duplex from the same or a different molecule through a double-stranded cut generated in the DNA. Because of their ability to cut one or two strands of DNA they are also target for some of the most successful anticancer drugs used in standard combination therapies of human cancers. An effective anticancer drug is Camptothecin (CPT) that specifically targets DNA topoisomerase 1 (TOP 1). The research project of the present thesis has been focused on the role of human TOP 1 during transcription and on the transcriptional consequences associated with TOP 1 inhibition by CPT in human cell lines. Previous findings demonstrate that TOP 1 inhibition by CPT perturbs RNA polymerase (RNAP II) density at promoters and along transcribed genes suggesting an involvement of TOP 1 in RNAP II promoter proximal pausing site. Within the transcription cycle, promoter pausing is a fundamental step the importance of which has been well established as a means of coupling elongation to RNA maturation. By measuring nascent RNA transcripts bound to chromatin, we demonstrated that TOP 1 inhibition by CPT can enhance RNAP II escape from promoter proximal pausing site of the human Hypoxia Inducible Factor 1 (HIF-1) and c-MYC genes in a dose dependent manner. This effect is dependent from Cdk7/Cdk9 activities since it can be reversed by the kinases inhibitor DRB. Since CPT affects RNAP II by promoting the hyperphosphorylation of its Rpb1 subunit the findings suggest that TOP 1inhibition by CPT may increase the activity of Cdks which in turn phosphorylate the Rpb1 subunit of RNAP II enhancing its escape from pausing. Interestingly, the transcriptional consequences of CPT induced topological stress are wider than expected. CPT increased co-transcriptional splicing of exon1 and 2 and markedly affected alternative splicing at exon 11. Surprisingly despite its well-established transcription inhibitory activity, CPT can trigger the production of a novel long RNA (5’aHIF-1) antisense to the human HIF-1 mRNA and a known antisense RNA at the 3’ end of the gene, while decreasing mRNA levels. The effects require TOP 1 and are independent from CPT induced DNA damage. Thus, when the supercoiling imbalance promoted by CPT occurs at promoter, it may trigger deregulation of the RNAP II pausing, increased chromatin accessibility and activation/derepression of antisense transcripts in a Cdks dependent manner. A changed balance of antisense transcripts and mRNAs may regulate the activity of HIF-1 and contribute to the control of tumor progression After focusing our TOP 1 investigations at a single gene level, we have extended the study to the whole genome by developing the “Topo-Seq” approach which generates a map of genome-wide distribution of sites of TOP 1 activity sites in human cells. The preliminary data revealed that TOP 1 preferentially localizes at intragenic regions and in particular at 5’ and 3’ ends of genes. Surprisingly upon TOP 1 downregulation, which impairs protein expression by 80%, TOP 1 molecules are mostly localized around 3’ ends of genes, thus suggesting that its activity is essential at these regions and can be compensate at 5’ ends. The developed procedure is a pioneer tool for the detection of TOP 1 cleavage sites across the genome and can open the way to further investigations of the enzyme roles in different nuclear processes.

DNA block copolymers - synthesis, morphologies and applications

The last decades have witnessed significant and rapid progress in polymer chemistry and molecular biology. The invention of PCR and advances in automated solid phase synthesis of DNA have made this biological entity broadly available to all researchers across biological and chemical sciences. Thanks to the development of a variety of polymerization techniques, macromolecules can be synthesized with predetermined molecular weights and excellent structural control. In recent years these two exciting areas of research converged to generate a new type of nucleic acid hybrid material, consisting of oligodeoxynucleotides and organic polymers. By conjugating these two classes of materials, DNA block copolymers are generated exhibiting engineered material properties that cannot be realized with polymers or nucleic acids alone. Different synthetic strategies based on grafting onto routes in solution or on solid support were developed which afforded DNA block copolymers with hydrophilic, hydrophobic and thermoresponsive organic polymers in good yields. Beside the preparation of DNA block copolymers with a relative short DNA-segment, it was also demonstrated how these bioorganic polymers can be synthesized exhibiting large DNA blocks (>1000 bases) applying the polymerase chain reaction. Amphiphilic DNA block copolymers, which were synthesized fully automated in a DNA synthesizer, self-assemble into well-defined nanoparticles. Hybridization of spherical micelles with long DNA templates that encode several times the sequence of the micelle corona induced a transformation into rod-like micelles. The Watson-Crick motif aligned the hydrophobic polymer segments along the DNA double helix, which resulted in selective dimer formation. Even the length of the resulting nanostructures could be precisely adjusted by the number of nucleotides of the templates. In addition to changing the structural properties of DNA-b-PPO micelles, these materials were applied as 3D nanoscopic scaffolds for organic reactions. The DNA strands of the corona were organized by hydrophobic interactions of the organic polymer segments in such a fashion that several DNA-templated organic reactions proceeded in a sequence specific manner; either at the surface of the micelles or at the interface between the biological and the organic polymer blocks. The yields of reactions employing the micellar template were equivalent or better than existing template architectures. Aside from its physical properties and the morphologies achieved, an important requirement for a new biomaterial is its biocompatibility and interaction with living systems, i.e. human cells. The toxicity of the nanoparticles was analyzed by a cell proliferation assay. Motivated by the non-toxic nature of the amphiphilic DNA block copolymers, these nanoobjects were employed as drug delivery vehicles to target the anticancer drug to a tumor tissue. The micelles obtained from DNA block copolymers were easily functionalized with targeting units by hybridization. This facile route allowed studying the effect of the amount of targeting units on the targeting efficacy. By varying the site of functionalization, i.e. 5’ or 3’, the outcome of having the targeting unit at the periphery of the micelle or in the core of the micelle was studied. Additionally, these micelles were loaded with an anticancer drug, doxorubicin, and then applied to tumor cells. The viability of the cells was calculated in the presence and absence of targeting unit. It was demonstrated that the tumor cells bearing folate receptors showed a high mortality when the targeting unit was attached to the nanocarrier.

Untersuchung der DNA-bindenden Eigenschaften neuer Nukleobasen-gekoppelter Pyrrolcarboxamide, Combilexine und Hetaren[a]carbazol-Derivate: Validierung und Etablierung von in-vitro- und in-silico-Methoden

Da maligne Neoplasien durch Mutationen in Proto-Onko- und/oder Tumorsuppressorgenen ausgelöst werden, stellt die DNA eines der wichtigsten Targets für die Entwicklung neuer Zytostatika dar. Auch bei den im Arbeitskreis Pindur designten und synthetisier-ten Verbindungen der Nukleobasen-gekoppelten Pyrrolcarboxamid-, der Hetaren[a]carbazol- und der Combilexin-Reihe handelt es sich um DNA-Liganden mit potentiell antitumoraktiven Eigenschaf-ten. Die einen dualen Bindemodus aufweisenden Combilexine bestehen aus einem Interkalator (u. a. Naphthalimid, Acridon), der über einen Linker variabler Kettenlänge mit einer rinnenbin-denden, von Netropsin abgeleiteten Bispyrrol-, oder einer bioisosteren Imidazol-, Thiazol- oder Thiophen-pyrrolcarboxamid-struktur verknüpft ist. Das N-terminale Ende der Combilexine wird von einer N,N-Dimethylaminopropyl- oder -ethyl-Seitenkette gebildet. Die DNA-Affinitäten der Liganden wurden mittels Tm-Wert-Messung-en bestimmt. Diese Denaturierungsexperimente wurden sowohl mit poly(dAdT)2- als auch mit Thymus-DNA (~42% GC-Anteil) durchge-führt, um Aussagen zur Stärke und zur Sequenzselektivität der DNA-Bindung machen zu können. Des Weiteren wurden die Bindekon-stanten einiger ausgewählter Vertreter mit Hilfe des Ethidium-bromid-Verdrängungsassays ermittelt; einige Testverbindungen wurden zudem auf potentiell vorhandene, TOPO I-inhibierende Eigenschaften untersucht. Diese biochemischen und biophysika-lischen Tests wurden durch Molecular Modelling-Studien ergänzt, die die Berechnung von molekularen Eigenschaften, die Durch-führung von Konformerenanalysen und die Simulation von DNA-Ligand-Komplexen (Docking) umfassten. Durch Korrelation der in vitro-Befunde mit den in silico-Daten gelang es, vor allem für die Substanzklasse der Combilexine einige richtungweisende Struktur-Wirkungsbeziehungen aufzustellen. So konnte gezeigt werden, dass die Einführung eines Imidazol-Rings in die rinnen-bindende Hetaren-pyrrolcarboxamid-Struktur der Combilexine aufgrund der H-Brücken-Akzeptor-Funktion des sp2-hybridisierten N-Atoms eine Verschiebung der Sequenzselektivität der DNA-Bindung von AT- zu GC-reichen Arealen der DNA bedingt. Zudem erwies sich ein C3-Linker für die Verknüpfung des Naphthalimids mit dem rinnenbindenden Strukturelement als am besten geeignet, während bei den Acridon-Derivaten die Verbindungen mit einem N-terminalen Buttersäure-Linker die höchste DNA-Affinität aufwiesen. Dies ist sehr wahrscheinlich auf die im Vergleich zum Naphthalimid-Molekül geringere y-Achsen-Ausdehnung (bzgl. eines x/y-Koordinatensystems) des Acridons zurückzuführen. Die ermittelten Struktur-Wirkungsbeziehungen können dazu herangezogen werden, das rationale Design neuer DNA-Liganden mit potentiell stärkerer DNA-Bindung zu optimieren.

DNA-Reparatur und Zelltod nach gentoxischem Stress in Monozyten, dendritischen Zellen und Makrophagen

Monozyten wie auch dendritische Zellen (DCs) und Makrophagen sind ein wichtiger Bestandteil des angeborenenen unspezifischen Immunsystems. Ein Kennzeichen dieser Zellen ist die Produktion von reaktiven Sauerstoffspezies (ROS) zur Abtötung von Pathogenen. Im Fall von chronischen Entzündungen oder Infekten kann es zu einer explosionsartigen Freisetzung freier Radikale kommen ('Oxidative Burst'). Aus vorangegangenen Untersuchungen war bekannt, dass die Expression der beiden Basen Exziosions Reparatur (BER)-Proteine XRCC1 und Ligase III während der Ausreifung humaner Monozyten zu DCs induziert wird (Briegert and Kaina, 2007). Dies lies vermuten, dass Monozyten aufgrund einer defekten BER eine hohe Sensitivität gegenüber ROS aufweisen. Um diese Hypothese zu überprüfen, wurde die Wirkung von ROS auf humane Monozyten und daraus abgeleiteten DCs und Makrophagen untersucht. In der vorliegenden Arbeit konnte gezeigt werden, dass Monozyten eine hohe Sensitivität gegenüber oxidativem Stress aufweisen, was auf eine höhere Einzelstrangbruch-Rate zurückzuführen war. Ursache hierfür ist das Fehlen der BER-Proteine XRCC1, Ligase III und PARP-1. Die fehlende Expression dieser Proteine resultierte letztendlich in Monozyten in einem Defekt der BER und DNA-Einzelstrangbruchreparatur. rnDie Proteine XRCC1, Ligase III und PARP-1 sind auch Bestandteil des Apparats des B-NHEJ ('backup-non homologous end joining'), was auf eine Beeinträchtigung der Monozyten hinsichtlich der Prozessierung von Doppelstrangbrüchen (DSBs) schließen lässt. Zur Untersuchung dieser Vermutung, wurde die Wirkung von Ionisierender Strahlung ('ionizing radiation'; IR) auf Monozyten, DCs und Makrophagen bestimmt. Monozyten zeigten eine signifikant höhere Sensitivität gegenüber IR als DCs und Makrophagen, was auf eine erhöhte DSB-Rate in den Monozyten nach IR zurückzuführen war. Expressionsanalysen und ein DNA-PK-Aktivitäts-Assay zeigten zusätzlich, dass Monozyten keine DNA-PKcs, ein bedeutender Faktor des C-NHEJ, exprimieren. Somit haben Monozyten sowohl einen Defekt im B-NHEJ als auch im C-NHEJ und sind demnach nicht in der Lage, DSBs zu reparieren.rnAuch gegenüber dem Alkylanz und Chemotherapeutikum Temozolomid bewirken die Reparaturdefekte eine hohe Sensitivität der Monozyten. Zur Therapie von Hirntumoren werden neben der Operation, die Bestrahlung und Chemotherapie mit Temozolomid angewendet. Die hohe Sensitivität von Monozyten gegenüber IR und Temozolomid könnte eine Erklärung für die starke Immunsuppression bei einer derartigen Therapie sein.rn

Pharmacogenetics in palliative care

Response to analgesics, anticancer pharmacotherapy and pharmacotherapy of other cancer related symptoms vary broadly between individuals. Age, disease, comorbidities, concomitant medication, organ function and patients' compliance may partly explain the differences. However, the focus of ongoing research has shifted towards genomic variants of phase I and II drug metabolizing enzymes with one important goal being an individual dose adjustment according to a patient's genotype. Polymorphisms of the cytochrome P 450 2D6 influence the metabolism of many drugs including the analgesics codeine, tramadol, hydrocodone and oxycodone, as well as the metabolism of tricyclic antidepressants and the anticancer drug tamoxifen. Other candidate genes such as (opioid)-receptors, transporters and other molecules important for pharmacotherapy in pain management are discussed. Although pharmacogenetics as a diagnostic tool has the potential to improve patient therapy, study results are often equivocal and limited by small sample sizes and often by their retrospective design. Well designed studies are needed to demonstrate superiority of pharmoacogenetics to conventional dosing regimes.