Human cytochromes P450 1A1 and 1B1 catalyze ring oxidation but not nitroreduction of environmental pollutant mononitropyrene isomers in primary cultures of human breast cells and cultured MCF-10A and MCF-7 cell lines

Yuan-Wan Sun, F. Peter Guengerich, Arun Sharma, Telih Boyiri, Shantu Amin, Karam El-Bayoumy

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Abstract

The position of the nitro group determines the relative carcinogenic activities of mononitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways. Qualitatively similar metabolic patterns were observed but quantitative differences were evident. On the basis of cochromatography with synthetic standards in two HPLC systems, metabolites of 1-NP were identified as 1-OH-Py, 3-, 6-, and 8-OH-1-NP and 1-AP. In the case of 2-NP, 6-OH-2-NP and 2-AP were identified. 4-NP was metabolized to 9,10-DHD-4-NP, Py-4,5-Q, 9,10-Q-4-NP, 9/10-OH-4-NP, 6/ 8-OH-4-NP, and 4-AP. Varying degrees of sulfate and glucuronide conjugation of mono-NP metabolites were detected. In MCF-7 cells, we found that 1-, 2-, and 4-NP bind to DNA at levels of 68, 17, and 132 pmol/mg DNA, respectively. Following HPLC analysis of the DNA hydrolysates, we detected multiple DNA adducts including those derived from nitro reduction of 2- and 4-NP; however, none was detected in the case of 1-NP. To determine the P450 enzymes responsible for the metabolic activation of these carcinogens, we incubated [3H]mono-NPs with recombinant human P450 1A1 or 1B1. Metabolites identified were primarily derived from ring oxidation; both P450s 1A1 and 1B1 yielded similar metabolic profiles. This is the first report demonstrating that human breast (target organ) cells, immortalized human mammary epithelial cell line MCF-10A, and breast cancer cell line MCF-7 are capable of activating mono-NPs to metabolites that can damage DNA.

Original languageEnglish (US)
Pages (from-to)1077-1085
Number of pages9
JournalChemical Research in Toxicology
Volume17
Issue number8
DOIs
StatePublished - Aug 1 2004

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Environmental Pollutants
MCF-7 Cells
Isomers
Cytochrome P-450 Enzyme System
Cultured Cells
Metabolites
Breast
Cells
Cell Line
Oxidation
DNA
Chemical activation
DNA Adducts
Glucuronides
Transcription Factor AP-1
Epithelial Cells
High Pressure Liquid Chromatography
Breast Neoplasms
Cell culture
Carcinogens

All Science Journal Classification (ASJC) codes

  • Toxicology

Cite this

@article{ad9b789757894ca5b0b41cccb8fb68b8,
title = "Human cytochromes P450 1A1 and 1B1 catalyze ring oxidation but not nitroreduction of environmental pollutant mononitropyrene isomers in primary cultures of human breast cells and cultured MCF-10A and MCF-7 cell lines",
abstract = "The position of the nitro group determines the relative carcinogenic activities of mononitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways. Qualitatively similar metabolic patterns were observed but quantitative differences were evident. On the basis of cochromatography with synthetic standards in two HPLC systems, metabolites of 1-NP were identified as 1-OH-Py, 3-, 6-, and 8-OH-1-NP and 1-AP. In the case of 2-NP, 6-OH-2-NP and 2-AP were identified. 4-NP was metabolized to 9,10-DHD-4-NP, Py-4,5-Q, 9,10-Q-4-NP, 9/10-OH-4-NP, 6/ 8-OH-4-NP, and 4-AP. Varying degrees of sulfate and glucuronide conjugation of mono-NP metabolites were detected. In MCF-7 cells, we found that 1-, 2-, and 4-NP bind to DNA at levels of 68, 17, and 132 pmol/mg DNA, respectively. Following HPLC analysis of the DNA hydrolysates, we detected multiple DNA adducts including those derived from nitro reduction of 2- and 4-NP; however, none was detected in the case of 1-NP. To determine the P450 enzymes responsible for the metabolic activation of these carcinogens, we incubated [3H]mono-NPs with recombinant human P450 1A1 or 1B1. Metabolites identified were primarily derived from ring oxidation; both P450s 1A1 and 1B1 yielded similar metabolic profiles. This is the first report demonstrating that human breast (target organ) cells, immortalized human mammary epithelial cell line MCF-10A, and breast cancer cell line MCF-7 are capable of activating mono-NPs to metabolites that can damage DNA.",
author = "Yuan-Wan Sun and Guengerich, {F. Peter} and Arun Sharma and Telih Boyiri and Shantu Amin and Karam El-Bayoumy",
year = "2004",
month = "8",
day = "1",
doi = "10.1021/tx049889d",
language = "English (US)",
volume = "17",
pages = "1077--1085",
journal = "Chemical Research in Toxicology",
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TY - JOUR

T1 - Human cytochromes P450 1A1 and 1B1 catalyze ring oxidation but not nitroreduction of environmental pollutant mononitropyrene isomers in primary cultures of human breast cells and cultured MCF-10A and MCF-7 cell lines

AU - Sun, Yuan-Wan

AU - Guengerich, F. Peter

AU - Sharma, Arun

AU - Boyiri, Telih

AU - Amin, Shantu

AU - El-Bayoumy, Karam

PY - 2004/8/1

Y1 - 2004/8/1

N2 - The position of the nitro group determines the relative carcinogenic activities of mononitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways. Qualitatively similar metabolic patterns were observed but quantitative differences were evident. On the basis of cochromatography with synthetic standards in two HPLC systems, metabolites of 1-NP were identified as 1-OH-Py, 3-, 6-, and 8-OH-1-NP and 1-AP. In the case of 2-NP, 6-OH-2-NP and 2-AP were identified. 4-NP was metabolized to 9,10-DHD-4-NP, Py-4,5-Q, 9,10-Q-4-NP, 9/10-OH-4-NP, 6/ 8-OH-4-NP, and 4-AP. Varying degrees of sulfate and glucuronide conjugation of mono-NP metabolites were detected. In MCF-7 cells, we found that 1-, 2-, and 4-NP bind to DNA at levels of 68, 17, and 132 pmol/mg DNA, respectively. Following HPLC analysis of the DNA hydrolysates, we detected multiple DNA adducts including those derived from nitro reduction of 2- and 4-NP; however, none was detected in the case of 1-NP. To determine the P450 enzymes responsible for the metabolic activation of these carcinogens, we incubated [3H]mono-NPs with recombinant human P450 1A1 or 1B1. Metabolites identified were primarily derived from ring oxidation; both P450s 1A1 and 1B1 yielded similar metabolic profiles. This is the first report demonstrating that human breast (target organ) cells, immortalized human mammary epithelial cell line MCF-10A, and breast cancer cell line MCF-7 are capable of activating mono-NPs to metabolites that can damage DNA.

AB - The position of the nitro group determines the relative carcinogenic activities of mononitropyrene isomers (mono-NPs) in the rat mammary gland. To determine whether the results obtained in rodents treated with these environmental pollutants can be applicable to humans, we examined their metabolic activation in primary cultures of human breast cells derived from reduction mammoplasty, as well as in the cultured human breast cancer cell line MCF-7 and the immortalized human mammary epithelial cell line MCF-10A. Primary cultures as well as cell lines were competent in metabolizing all three isomers via both ring oxidation and nitro reduction pathways. Qualitatively similar metabolic patterns were observed but quantitative differences were evident. On the basis of cochromatography with synthetic standards in two HPLC systems, metabolites of 1-NP were identified as 1-OH-Py, 3-, 6-, and 8-OH-1-NP and 1-AP. In the case of 2-NP, 6-OH-2-NP and 2-AP were identified. 4-NP was metabolized to 9,10-DHD-4-NP, Py-4,5-Q, 9,10-Q-4-NP, 9/10-OH-4-NP, 6/ 8-OH-4-NP, and 4-AP. Varying degrees of sulfate and glucuronide conjugation of mono-NP metabolites were detected. In MCF-7 cells, we found that 1-, 2-, and 4-NP bind to DNA at levels of 68, 17, and 132 pmol/mg DNA, respectively. Following HPLC analysis of the DNA hydrolysates, we detected multiple DNA adducts including those derived from nitro reduction of 2- and 4-NP; however, none was detected in the case of 1-NP. To determine the P450 enzymes responsible for the metabolic activation of these carcinogens, we incubated [3H]mono-NPs with recombinant human P450 1A1 or 1B1. Metabolites identified were primarily derived from ring oxidation; both P450s 1A1 and 1B1 yielded similar metabolic profiles. This is the first report demonstrating that human breast (target organ) cells, immortalized human mammary epithelial cell line MCF-10A, and breast cancer cell line MCF-7 are capable of activating mono-NPs to metabolites that can damage DNA.

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