The goal of this project is to elucidate the role of five enzymes in the metabolic processes we think are involved in activation/deactivation of estrogens in the pathway leading to tumor initiation. We have hypothesized that estrogens initiate breast, prostrate and other human cancers by reaction of catechol estrogens-3,4-quinones (CE-3,4-Q) with DNA to form adducts that lead to oncogenic mutations. In this process, the estrogens, estrogen and 17beta-estradiol are metabolized to the 4- catechol estrogens (4-CE), which are further oxidized to CE-3,4-Q. Hydroxylation of estrogens to 2-CE is catalyzed by cytochrome P450 (CYP) 1A1. Hydroxylation of estrogens to 4-CE is catalyzed by the activating enzyme cytochrome CYP1B1, but further oxidation of the 4- CE to CE-4,4-Q is usually blocked by catechol-O-methyltransferase (COMT)-catalyzed methylation of the 4-CE, a deactivating step. The CE- Q are reduced to CE by quinone oxidoreductase (QOR), a deactivating event. Another key event may be the conversion of androgens to estrogens by CYP19, aromatase. To complement the information gained in Project 1, we plan to investigate two of the factors that can affect the activity of these enzymes in human tissues: the level of expression of the enzyme and its genetic variants. We propose to accomplish the following specific aims: (1) Assay the expression of aromatase, CYP1A1, CYP1B1, QOR and COMT in the mammary gland of female ACI rats and prostate gland of male Noble rats by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and by their catalytic activity in microsomes. (2) Assay the expression of aromatase, CYP1A1, CYP1B1, QOR and COMT by RT-PCR and their polymorphic variations in human breast and prostate samples obtained from women and men with and without breast or prostate cancer. The results of these studies will provide evidence on the role of the five enzymes in the initiation of breast and prostate tumors, as well as complementing the information gained in Project 1. These findings will help us understand the role of estrogens in initiation cancer and form the basis of developing preventative strategies.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Program Projects (P01)
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Subcommittee E - Prevention &Control (NCI)
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University of Nebraska Medical Center
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Cavalieri, Ercole; Saeed, Muhammad; Zahid, Muhammad et al. (2012) Mechanism of DNA depurination by carcinogens in relation to cancer initiation. IUBMB Life 64:169-79
Zahid, Muhammad; Saeed, Muhammad; Rogan, Eleanor G et al. (2010) Benzene and dopamine catechol quinones could initiate cancer or neurogenic disease. Free Radic Biol Med 48:318-24
Saeed, Muhammad; Rogan, Eleanor; Cavalieri, Ercole (2009) Mechanism of metabolic activation and DNA adduct formation by the human carcinogen diethylstilbestrol: the defining link to natural estrogens. Int J Cancer 124:1276-84
Saeed, Muhammad; Higginbotham, Sheila; Gaikwad, Nilesh et al. (2009) Depurinating naphthalene-DNA adducts in mouse skin related to cancer initiation. Free Radic Biol Med 47:1075-81
Lu, Fang; Zahid, Muhammad; Wang, Cheng et al. (2008) Resveratrol prevents estrogen-DNA adduct formation and neoplastic transformation in MCF-10F cells. Cancer Prev Res (Phila Pa) 1:135-45
Gaikwad, Nilesh W; Yang, Li; Muti, Paola et al. (2008) The molecular etiology of breast cancer: evidence from biomarkers of risk. Int J Cancer 122:1949-57
Chakravarti, Dhrubajyoti; Venugopal, Divya; Mailander, Paula C et al. (2008) The role of polycyclic aromatic hydrocarbon-DNA adducts in inducing mutations in mouse skin. Mutat Res 649:161-78
Zahid, Muhammad; Saeed, Muhammad; Lu, Fang et al. (2007) Inhibition of catechol-O-methyltransferase increases estrogen-DNA adduct formation. Free Radic Biol Med 43:1534-40
Gaikwad, Nilesh W; Rogan, Eleanor G; Cavalieri, Ercole L (2007) Evidence from ESI-MS for NQO1-catalyzed reduction of estrogen ortho-quinones. Free Radic Biol Med 43:1289-98
Zahid, Muhammad; Gaikwad, Nilesh W; Rogan, Eleanor G et al. (2007) Inhibition of depurinating estrogen-DNA adduct formation by natural compounds. Chem Res Toxicol 20:1947-53

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