No / NAD(P)H:quinone oxidoreductase-1 (NQO1) is a potential target for therapeutic intervention but attempts to exploit NQO1 using quinone-based bioreductive prodrugs have been largely compromised by toxicity to organs that inherently express high levels of NQO1. In an attempt to circumvent this problem, this study describes the development of a tripartite quinone-based drug delivery system, the ultimate objective of which is to release a targeted therapeutic agent following the reduction of a quinone "trigger" by NQO1. Molecular modeling of drug/NQO1 interactions were conducted prior to the synthesis of N-{4-[bis-(2-chloroethyl)-amino]-phenyl}-beta,beta,2,4,5-pentamethyl-3,6-dioxo-1,4-cyclohexadiene-1-propanamide (prodrug 1). Prodrug 1 is a good substrate for purified NQO1 (V(max) and K(m) values of 11.86 +/- 3.09 micromol/min/mg and 2.70 +/- 1.14 micromol/L, respectively) and liquid chromatography-mass spectrometry analysis of the metabolites generated showed that lactone 3 and aniline mustard 4 were generated in a time- and NQO1-dependent manner. Chemosensitivity studies showed that prodrug 1 is selectively toxic to cells that overexpress NQO1 under aerobic conditions, and comet assay analysis confirmed the presence of elevated interstrand cross-links in NQO1-rich compared with NQO1-deficient cells. Hypoxic sensitization (hypoxic cytotoxicity ratio = 15.8) was observed in T47D cells that overexpress cytochrome P450 reductase. In conclusion, the results of this study provide mechanistic proof of principle that a tripartite benzoquinone drug delivery system is enzymatically reduced to release an active therapeutic agent. Further development of this concept to fine-tune substrate specificity for specific reductases and/or the inclusion of alternative therapeutic agents is warranted.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2012-08-29T21:11:40Z No. of bitstreams: 1 Silvana Sousa Paz Avaliação de marcadores....pdf: 756990 bytes, checksum: 5aac886be232eac44d86b25a30837ac4 (MD5) / Made available in DSpace on 2012-08-29T21:11:40Z (GMT). No. of bitstreams: 1 Silvana Sousa Paz Avaliação de marcadores....pdf: 756990 bytes, checksum: 5aac886be232eac44d86b25a30837ac4 (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, Bahia, Brasil / As leucemias são malignidades hematopoiéticas, caracterizadas por subgrupos biologicamente distintos, sendo os tipos mais frequentes de cânceres em crianças e adolescentes. Polimorfismos em genes de enzimas que metabolizam xenobióticos podem estar relacionados com a inserções/deleções, polimorfismos de nucleotídeo simples (SNP’s) e variações no número de cópias e têm sido relacionados com a patogênese de algumas neoplasias hematológicas, como a leucemia linfóide aguda (LLA). O objetivo deste estudo foi o de determinar as frequências de polimorfismos em genes associados ao estresse oxidativo e metabolismo de xenobióticos (GSTT1, GSTM1, CYP2E1, NQO1 e MPO), em pacientes pediátricos com LLA, associando-as a aspectos clínicos e marcadores de evolução da doença. A casuística foi composta por 37 pacientes pediátricos seguidos na clínica ONCO e tratados pelo protocolo GBTLI-LLA 93. O perfil hematológico dos pacientes foi realizado ao diagnóstico e durante o tratamento e os polimorfismos gênicos foram investigados por reação da polimerase em cadeia - polimorfismo de tamanho de fragmento de restrição (PCR-RFLP) e por reação da polimerase em cadeia multiplex (PCR Multiplex). As análises estatísticas apresentaram significância para os valores de leucócitos totais nos D1 e D7 (p= 0,0016) e nos D1 e D14 (p= 0,0059); linfócitos nos D1 e D7 (p= 0,0088) e D1 e D14 (p= 0,0101); segmentados neutrófilos nos D1 e D7 (p= 0,0033) e D1 e D14 (p= 0,0252); blastos periféricos D1 e D7 (p< 0,0001) e D1 e D14 (p< 0,0001) e; para a contagem de blastos na medula óssea (MO) nos D1 e D15 (p<0,0001), D1 e D28 (p< 0,0001) e D15 e D28 (p= 0,0005). As frequências alélicas e genotípicas para os genes estudados estavam em equilíbrio de Hardy-Weinberg. A mutação do gene MPO foi associada a infiltração da MO (p= 0,0473) e presença de blastos no líquor (p= 0,0473). O polimorfismo do gene GSTT1 foi associado à contagem de leucócitos (p= 0,014) e plaquetas (p= 0,0034) no D1 e a contagem de leucócitos (p=0,037) e segmentados neutrófilos (p= 0,0008) no D7. A presença do polimorfismo no gene NQO1 foi associado à infiltração da MO (p= 0,0410) e a presença de blastos no líquor (p= 0,0410). Entretanto, o polimorfismo NQO1 apresentou associação com a presença de palidez (p=0,0096). Os dados encontrados corroboram em parte com dados encontrados na literatura, sendo necessária a realização de um estudo com numero maior de pacientes para confirmação dos achados relacionados aos genes investigados e a LLA. / Leukemia is characterized by biologically distinct subgroups and is the most frequent hematological malignity in childhood. Polymorphisms in genes of enzymes that metabolize xenobiotics may be related to insertions/ deletions, single nucleotide polymorphisms (SNP's) and gene copies variation and have been related to the pathogenesis of some hematologic malignancies, including acute lymphoblastic leukemia (ALL). The aim of this study was to investigate genes polymorphisms associated with the oxidative stress and xenobiotic metabolism (GSTT1, GSTM1, CYP2E1, NQO1 and MPO) in a group of childhood ALL patients, associating them with clinical evolution and prognostic markers. The casuistic was compound by 37 pediatric patients followed and treated at the clinic ONCO with the protocol GBTLI-LLA 93. The hematological profile of patients was performed at diagnosis and during treatment and gene polymorphisms were investigated by Polimerase Chain Reaction - Restriction Fragment Length Polymorfism (PCR-RFLP) and Polimerase Chain Reaction Multiplex (Multiplex PCR). Statistical analyses were significant for values of total leukocytes in D1 and D7 (p= 0.0016) and in D1 e D14 (p= 0.0059); lymphocytes in D1 and D7 (p= 0.0088), D1 and D14 (p= 0.0101); neutrophils in D1 and D7 (p= 0.0033), D1 and D14 (p= 0.0252). It was also find statistical significance at the number of peripheral blasts in D1 and D7 (p< 0.0001), D1 and D14 (p< 0.0001); the blast count in bone marrow (BM) in D1 and D15 (p<0.0001), D1 and D28 (p< 0.0001) and D15 and D28 (p= 0.0005). The allelic and genotypic frequencies of all gene polymorphism investigated were in Hardy-Weinberg equilibrium. The MPO gene mutation was associated with infiltration of the BM in D28 (p= 0.0473) and the presence of blasts in the CSF (p= 0.0473). The GSTT1 gene polymorphism was associated with leukocyte (p= 0.014) and platelet counts (p= 0.0034) in D1 and with leukocytes (p=0,037) and neutrophils counts (p= 0.0008) in D7. The NQO1 gene polymorphism presence was associated with BM infiltration at D28 (p= 0.0410) and the presence of blasts in the CSF (p= 0.0410). However, the NQO1 polymorphism was associated with the presence of pallor (p=0.0096). Result described here corroborated in part with previous described data, being necessary to carry out additional study with a larger number of patients to confirm the finding related to genes polymorphism investigated and the clinical evolution of ALL patients.