Cytotoxicity of cyclophosphamide, paclitaxel, and docetaxel for tumor cell lines in vitro: effects of concentration, time and cytochrome P450-catalyzed metabolism

Gut, Ivan; Danielová, V.; Holubová, J; Souček, Pavel; Kluckova, H.

doi:10.1007/s002040000141

Cited by 25 publications

(16 citation statements)

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“…The concentration of microsomal protein was determined according to the method of Lowry et al (1951), with bovine serum albumin as standard. Specific induction of CYP3A1/2 in rats by pregnenolone 16␣-carbonitrile pretreatment (inducing higher levels than dexamethasone) was immunochemically characterized as described previously (Nedelcheva et al, 1998;Gut et al, 2000). Specific P450 contents are shown in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Different in Vitro Metabolism of Paclitaxel and Docetaxel in Humans, Rats, Pigs, and Minipigs

Václavíková

Souček²,

Svobodová³

et al. 2004

Drug Metab Dispos

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ABSTRACT:We investigated cytochrome P450 (P450)-catalyzed metabolism of the important cancer drugs paclitaxel and docetaxel in rat, pig, minipig, and human liver microsomes and cDNA-expressed P450 enzymes. In rat microsomes, paclitaxel was metabolized mainly to C3-hydroxypaclitaxel (C3-OHP) and to a lesser extent to C2-hydroxypaclitaxel (C2-OHP), di-hydroxypaclitaxel (di-OHP), and another unknown monohydroxylated paclitaxel. In pig and minipig microsomes, this unknown hydroxypaclitaxel was the main metabolite, whereas C3-OHP was a minor product. In minipigs, C2-OHP was the next minor product. In human liver microsomes, 6␣-hydroxypaclitaxel (6␣-OHP) was the main metabolite, followed by C3-OHP and C2-OHP. Among different cDNAexpressed human P450 enzymes (CYP1A2, 1B1, 2A6, 2C9, 2E1, and 3A4), only CYP3A4 enzyme formed C3-OHP and C2-OHP. Docetaxel was metabolized in pig, minipig, rat, and human liver microsomes mainly to hydroxydocetaxel (OHDTX), whereas CYP3A-induced rat microsomes produced primarily diastereomeric hydroxyoxazolidinones. Human liver microsomes from 10 different individuals formed OHDTX at different rates correlated with CYP3A4 content. Troleandomycin as a selective inhibitor of CYP3A inhibited the formation of C3-OHP, C2-OHP, and di-OHP, as well as the unknown OHP produced in rat, minipig, and pig microsomes. In human liver microsomes, troleandomycin inhibited C3-OHP and C2-OHP formation, and a suitable inhibitor of human CYP2C8, fisetin, strongly inhibited the formation of 6␣-OHP, known to be catalyzed by human CYP2C8. In conclusion, the metabolism of docetaxel is the same in all four species, but metabolism of paclitaxel is different, and 6␣-OHP remains a uniquely human metabolite. Pigs and minipigs compared with each other formed the same metabolites of paclitaxel.

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Section: Methodsmentioning

confidence: 99%

Different in Vitro Metabolism of Paclitaxel and Docetaxel in Humans, Rats, Pigs, and Minipigs

Václavíková

Souček²,

Svobodová³

et al. 2004

Drug Metab Dispos

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“…[12][13][14][15][16][17][18][19] The enzymes in these families are involved in the metabolism of xenobiotic substances such as carcinogens, pro-carcinogens and chemotherapeutics. [20][21][22][23] Of note, CYP1B1 and, more recently, CYP2W1 have been identified as having tumor-specific expression. 15,17,18,24,25 These observations have lead to a greater appreciation for the role of CYPs in tumor formation and development.…”

Section: Introductionmentioning

confidence: 99%

Targeting Cytochrome P450 Enzymes: A New Approach in Anticancer Drug Development

Bruno

Njar

2007

ChemInform

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Cytochrome P450s (CYPs) represent a large class of heme-containing enzymes that catalyze the metabolism of multitudes of substrates both endogenous and exogenous. Until recently, however, CYPs have been largely overlooked in cancer drug development, acknowledged only for their role in Phase I metabolism of chemotherapeutics. The first successful strategy targeting CYP enzymes in cancer therapy was the development of potent inhibitors of CYP19 (aromatase) for the treatment of breast cancer. Aromatase inhibitors ushered in a new era in hormone ablation therapy for estrogen dependent cancers, and have paved the way for similar strategies (i.e. inhibition of CYP17) that combat androgen dependent prostate cancer. Identification of CYPs involved in the inactivation of anti-cancer metabolites of Vitamin D 3 and Vitamin A has triggered development of agents that target these enzymes as well. The discovery of the over-expression of exogenous metabolizing CYPs, such as CYP1B1, in cancer cells has roused interest in the development of inhibitors for chemoprevention and of prodrugs designed to be activated by CYPs only in cancer cells. Finally, the expression of CYPs within tumors has been utilized in the development of bioreductive molecules that are activated by CYPs only under hypoxic conditions. This review offers the first comprehensive analysis of strategies in drug development that either inhibit or exploit CYP enzymes for the treatment of cancer.

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“…Furthermore, both cultured hepatocytes and hepatoma cell lines have low levels of P450 isoforms in the absence of specific inducers (24, 25). Although hepatocytes are useful for approximating liver toxicity, human toxicity can be due to effects of the metabolites on other organs.In contrast with hepatocytes, a direct mimic of first-pass human metabolism can be achieved by using microsomal or recombinant P450 preparations (26)(27)(28)(29). Isolated enzymes, however, must be linked to cell-based screening to assess the toxicity of the generated metabolites.…”

mentioning

confidence: 99%

“…In contrast with hepatocytes, a direct mimic of first-pass human metabolism can be achieved by using microsomal or recombinant P450 preparations (26)(27)(28)(29). Isolated enzymes, however, must be linked to cell-based screening to assess the toxicity of the generated metabolites.…”

mentioning

confidence: 99%

Metabolizing enzyme toxicology assay chip (MetaChip) for high-throughput microscale toxicity analyses

Lee

Park

Dordick

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

152

110

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The clinical progression of new chemical entities to pharmaceuticals remains hindered by the relatively slow pace of technology development in toxicology and clinical safety evaluation, particularly in vitro approaches, that can be used in the preclinical and early clinical phases of drug development. To alleviate this bottleneck, we have developed a metabolizing enzyme toxicology assay chip (MetaChip) that combines high-throughput P450 catalysis with cell-based screening on a microscale platform. The MetaChip concept is demonstrated by using sol-gel encapsulated P450s to activate the prodrug cyclophosphamide, which is the major constituent of the anticancer drug Cytoxan, as well as other compounds that are activated by P450 metabolism. The MetaChip provides a high-throughput microscale alternative to currently used in vitro methods for human metabolism and toxicology screening based on liver slices, cultured human hepatocytes, purified microsomal preparations, or isolated and purified P450s. This technology creates opportunities for rapid and inexpensive assessment of ADME͞Tox (absorption, distribution, metabolism, excretion͞toxicology) at very early phases of drug development, thereby enabling unsuitable candidates to be eliminated from consideration much earlier in the drug discovery process.in situ drug metabolism ͉ in vitro cytotoxicity ͉ P450 ͉ sol-gel encapsulation I n the past decade, there has been a dramatic increase in the number of new chemical entities (NCEs) and screenable drug targets as a result of combinatorial chemistry and advances in genomics and proteomics (1-4). Nevertheless, these advances have not translated into an increased number of new drug approvals (5, 6), in part because of the high failure rate due to toxicity of the NCE or its metabolite(s) (7). Furthermore, screening for toxicity at early stages of the drug discovery process is precluded by the large number of compounds available at the lead discovery stage, forcing medicinal chemists to select compounds for lead optimization based on limited information about their toxicological properties. In particular, there remains a lack of in vitro techniques that can adequately mimic human metabolism and therefore assess cell-specific toxicity of NCEs and their metabolites at speeds consistent with high-throughput biological activity screening.The human body, primarily the liver, contains a variety of enzymes that are involved in the metabolism of the myriad chemicals that comprise today's pharmaceuticals. By far the most important class of metabolic enzymes is the cytochromes P450, which are directly involved in the initial (or ''first-pass'') clearance of drugs from the body (8, 9). During this process, drug metabolites are generated, some of which are biologically active in their own right and exert the desired pharmacological effect. For example, conversion of the antihistamine loratadine to descarboethoxyloratadine by CYP2D6 and CYP3A4 is required for biological activity (10). Often, however, drug metabolism can lead to undesirable ...

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Cytotoxicity of cyclophosphamide, paclitaxel, and docetaxel for tumor cell lines in vitro: effects of concentration, time and cytochrome P450-catalyzed metabolism

Cited by 25 publications

References 0 publications

Different in Vitro Metabolism of Paclitaxel and Docetaxel in Humans, Rats, Pigs, and Minipigs

Different in Vitro Metabolism of Paclitaxel and Docetaxel in Humans, Rats, Pigs, and Minipigs

Targeting Cytochrome P450 Enzymes: A New Approach in Anticancer Drug Development

Metabolizing enzyme toxicology assay chip (MetaChip) for high-throughput microscale toxicity analyses

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