TY - JOUR
T1 - Inhibition of catechol-O-methyltransferase increases estrogen-DNA adduct formation
AU - Zahid, Muhammad
AU - Saeed, Muhammad
AU - Lu, Fang
AU - Gaikwad, Nilesh
AU - Rogan, Eleanor
AU - Cavalieri, Ercole
N1 - Funding Information:
This research was supported by U.S. Public Health Service Grant P01 CA49210 from the National Cancer Institute and the U.S. Army Breast Cancer Research Program Grant DAMD 17-03-1-0229. Core support at the Eppley Institute was provided by Grant P30 CA36727 from the National Cancer Institute.
PY - 2007/12/1
Y1 - 2007/12/1
N2 - The association found between breast cancer development and prolonged exposure to estrogens suggests that this hormone is of etiologic importance in the causation of the disease. Studies on estrogen metabolism, formation of DNA adducts, carcinogenicity, cell transformation, and mutagenicity have led to the hypothesis that reaction of certain estrogen metabolites, predominantly catechol estrogen-3,4-quinones, with DNA forms depurinating adducts [4-OHE1(E2)-1-N3Ade and 4-OHE1(E2)-1-N7Gua]. These adducts cause mutations leading to the initiation of breast cancer. Catechol-O-methyltransferase (COMT) is considered an important enzyme that protects cells from the genotoxicity and cytotoxicity of catechol estrogens, by preventing their conversion to quinones. The goal of the present study was to investigate the effect of COMT inhibition on the formation of depurinating estrogen-DNA adducts. Immortalized human breast epithelial MCF-10F cells were treated with 4-OHE2 (0.2 or 0.5 μM) for 24 h at 120, 168, 216, and 264 h postplating or one time at 1-30 μM 4-OHE2 with or without the presence of COMT inhibitor (Ro41-0960). The culture media were collected at each point, extracted by solid-phase extraction, and analyzed by HPLC connected with a multichannel electrochemical detector. The results demonstrate that MCF-10F cells oxidize 4-OHE2 to E1(E2)-3,4-Q, which react with DNA to form the depurinating N3Ade and N7Gua adducts. The COMT inhibitor Ro41-0960 blocked the methoxylation of catechol estrogens, with concomitant 3- to 4-fold increases in the levels of the depurinating adducts. Thus, low activity of COMT leads to higher levels of depurinating estrogen-DNA adducts that can induce mutations and initiate cancer.
AB - The association found between breast cancer development and prolonged exposure to estrogens suggests that this hormone is of etiologic importance in the causation of the disease. Studies on estrogen metabolism, formation of DNA adducts, carcinogenicity, cell transformation, and mutagenicity have led to the hypothesis that reaction of certain estrogen metabolites, predominantly catechol estrogen-3,4-quinones, with DNA forms depurinating adducts [4-OHE1(E2)-1-N3Ade and 4-OHE1(E2)-1-N7Gua]. These adducts cause mutations leading to the initiation of breast cancer. Catechol-O-methyltransferase (COMT) is considered an important enzyme that protects cells from the genotoxicity and cytotoxicity of catechol estrogens, by preventing their conversion to quinones. The goal of the present study was to investigate the effect of COMT inhibition on the formation of depurinating estrogen-DNA adducts. Immortalized human breast epithelial MCF-10F cells were treated with 4-OHE2 (0.2 or 0.5 μM) for 24 h at 120, 168, 216, and 264 h postplating or one time at 1-30 μM 4-OHE2 with or without the presence of COMT inhibitor (Ro41-0960). The culture media were collected at each point, extracted by solid-phase extraction, and analyzed by HPLC connected with a multichannel electrochemical detector. The results demonstrate that MCF-10F cells oxidize 4-OHE2 to E1(E2)-3,4-Q, which react with DNA to form the depurinating N3Ade and N7Gua adducts. The COMT inhibitor Ro41-0960 blocked the methoxylation of catechol estrogens, with concomitant 3- to 4-fold increases in the levels of the depurinating adducts. Thus, low activity of COMT leads to higher levels of depurinating estrogen-DNA adducts that can induce mutations and initiate cancer.
KW - COMT inhibition
KW - Depurinating estrogen-DNA adducts
KW - Estrogen metabolism
KW - Estrogen protective enzymes
UR - http://www.scopus.com/inward/record.url?scp=35349013519&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=35349013519&partnerID=8YFLogxK
U2 - 10.1016/j.freeradbiomed.2007.08.005
DO - 10.1016/j.freeradbiomed.2007.08.005
M3 - Article
C2 - 17964424
AN - SCOPUS:35349013519
SN - 0891-5849
VL - 43
SP - 1534
EP - 1540
JO - Free Radical Biology and Medicine
JF - Free Radical Biology and Medicine
IS - 11
ER -