Intratumoral expression of genes encoding Cytochrome P450 enzymes (CYP) might play a critical role not only in cancer development but also in the metabolism of anticancer drugs. The purpose of this study was to compare the mRNA expression patterns of seven representative CYPs in paired tumor and normal tissue of child patients with rabdomyosarcoma (RMS). Using real time quantitative RT-PCR, the gene expression pattern of CYP1A1, CYP1A2, CYP1B1, CYP2E1, CYP2W1, CYP3A4, and CYP3A5 were analyzed in tumor and adjacent non-tumor tissues from 13 child RMS patients. Protein concentration of CYPs was determined using Western blot. The expression levels were tested for correlation with the clinical and pathological data of the patients. Our data showed that the expression levels of CYP1A1 and CYP1A2 were negligible. Elevated expression of CYP1B1 mRNA and protein was detected in most RMS tumors and adjacent normal tissues. Most cancerous samples exhibit higher levels of both CYP3A4 and CYP3A5 compared with normal tissue samples. Expression of CYP2E1 mRNA was found to be significantly higher in tumor tissue, however no relation was found with protein levels. CYP2W1 mRNA and/or protein are mainly expressed in tumors. In conclusion, we defined the CYP gene expression profile in tumor and paired normal tissue of child patients with RMS. The overexpression of CYP2W1, CYP3A4 and CYP3A5 in tumor tissues suggests that they may be involved in RMS chemoresistance; furthermore, they may be exploited for the localized activation of anticancer prodrugs.

This study demonstrates that chronic aspartame (ASP) consumption leads to an increase of phase I metabolizing enzymes (cytochrome P450 (CYP)) in rat brain. Wistar rats were treated by gavage with ASP at daily doses of 75 and 125 mg/kg body weight for 30 days. Cerebrum and cerebellum were used to obtain microsomal fractions to analyse activity and protein levels of seven cytochrome P450 enzymes. Increases in activity were consistently found with the 75 mg/kg dose both in cerebrum and cerebellum for all seven enzymes, although not at the same levels: CYP 2E1-associated 4-nitrophenol hydroxylase (4-NPH) activity was increased 1.5-fold in cerebrum and 25-fold in cerebellum; likewise, CYP2B1-associated penthoxyresorufin O-dealkylase (PROD) activity increased 2.9- and 1.7-fold respectively, CYP2B2-associated benzyloxyresorufin O-dealkylase (BROD) 4.5- and 1.1- fold, CYP3A-associated erythromycin N-demethylase (END) 1.4- and 3.3-fold, CYP1A1-associated ethoxyresorufin O-deethylase (EROD) 5.5- and 2.8-fold, and CYP1A2- associated methoxyresorufin O-demethylase (MROD) 3.7- and 1.3-fold. Furthermore, the pattern of induction of CYP immunoreactive proteins by ASP paralleled that of 4-NHP-, PROD-, BROD-, END-, EROD- and MROD-related activities only in the cerebellum. Conversely, no differences in CYP concentration and activity were detected in hepatic microsomes of treated animals with respect to the controls, suggesting a brain-specific response to ASP treatment.

This study demonstrates that aspartame consumption and insulin treatment in a juvenile diabetic rat model leads to increase in cytochrome P450 (CYP) 2E1 and CYP3A2 isozymes in brain. Diabetes mellitus was induced in postweaned 21-day-old Wistar male rat by streptozotocin. Animals were randomly assigned to one of the following groups: untreated control, diabetic (D), D-insulin, D-aspartame, or the D-insulin + aspartame-treated group. Brain and liver tissue samples were used to analyze the activity of CYP2E1 and CYP3A2 and protein levels. Our results indicate that combined treatment with insulin and aspartame in juvenile diabetic rats significantly induced CYP2E1 in the cerebrum and cerebellum without modifying it in the liver, while CYP3A2 protein activity increased both in the brain and in the liver. The induction of CYP2E1 in the brain could have important in situ toxicological effects, given that this CYP isoform is capable of bioactivating various toxic substances. Additionally, CYP3A2 induction in the liver and brain could be considered a decisive factor in the variation of drug response and toxicity.

The effect of transfluthrin (TF) or D-allethrin (DA) pyrethroid (PYR) vapors, often contained as main ingredients in two commercially available mosquito repellent mats, on cytochrome P450 (CYP) enzymes of rat brain and liver was assessed. Immunodetection of CYP2E1 and CYP3A2 proteins revealed their induction in cerebrum and cerebellum, but not in liver microsomes of rats exposed by inhalation to TF or DA. This overexpression of proteins correlated with an increase of their catalytic activities. The specifically increased expression of CYP isoenzymes, due to PYR exposure in the rat brain, could perturb the normal metabolism of endogenous and xenobiotic compounds and leads to increased risks of neurotoxicity by bioactivation, lipid peroxidation and DNA damage.

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