TY - JOUR
T1 - Comparative action of 1,4-phenylenebis(methylene)selenocyanate and its metabolites against 7,12-dimethylbenz[a]anthracene-DNA adduct formation in the rat and cell proliferation in rat mammary tumor cells
AU - El-Bayoumy, Karam
AU - Das, Arunangshu
AU - Boyiri, Telih
AU - Desai, Dhimant
AU - Sinha, Raghu
AU - Pittman, Brian
AU - Amin, Shantu
N1 - Funding Information:
This work was supported by grants from NCI: PO1 CA 46589, and the AHF Cancer Center Support Grant, P30 CA 17613.
PY - 2003/10/25
Y1 - 2003/10/25
N2 - 1,4-Phenylenebis(methylene)selenocyanate (p-XSC) inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis and DMBA-DNA binding in the rat mammary gland. Tetraselenocyclophane (TSC) was identified in rat feces as a metabolite of p-XSC. This led us to postulate the metabolic pathway: p-XSC→glutathione conjugate (p-XSeSG)→aromatic selenol (p-XSeH)→TSC. Whether p-XSC or one of its metabolites is responsible for cancer prevention is the focus of this study. We utilized the DMBA-DNA binding assay with p-XSC as a positive control to evaluate the chemopreventive potential of p-XSC metabolites at dietary selenium levels of 10ppm. Rats were fed AIN-76A diet supplemented with various selenium compounds for 1 week prior to the oral administration of a single dose of [ 3H]DMBA (5mg per rat, specific activity 51.3mCi/mmol). The rats were sacrificed 24h later and DNA was isolated from the mammary fat pads. Relative levels of total binding were: [pmol/mg DNA, mean±S.D., n=6]; DMBA [7.2±1.6]; DMBA+p-XSC [3.5±2.7]; DMBA+p-XSeSG [2.2±1.1]; DMBA+TSC [5.6±2.9]. All selenium compounds, except TSC, significantly inhibited DMBA-DNA adduct formation; however, the difference between p-XSC and p-XSeSG was not statistically significant. The inhibition of total binding was attributed to a reduction in the formation of the three major adducts derived from bay-region diol epoxides of DMBA. On the basis of their chromatographic characteristics, these were identified as anti-diol-epoxide:deoxyguanosine, syn-diol-epoxide:deoxyadenosine, and anti-diol-epoxide:deoxyadenosine. Our results suggest that p-XSeSG, but not TSC, is the likely inhibitor of mammary cancer. Selenium levels measured by atomic absorption spectroscopy in the target organ (mammary fat pads) and in plasma following the dietary administration of selenium compounds were in the order of p-XSeSG≅p- XSC>TSC. These results appear to be consistent with their order of inhibitory effects on total DMBA-DNA binding. Further in vitro studies of the effect of selenium compounds on cell proliferation suggest that, depending on the dose and time point selected, p-XSC is comparable to or better than p-XSeSG; but both are more effective than TSC. Collectively, our in vivo and in vitro results indicate that p-XSC and its conjugate are better candidates than TSC for future studies on mammary cancer chemoprevention.
AB - 1,4-Phenylenebis(methylene)selenocyanate (p-XSC) inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis and DMBA-DNA binding in the rat mammary gland. Tetraselenocyclophane (TSC) was identified in rat feces as a metabolite of p-XSC. This led us to postulate the metabolic pathway: p-XSC→glutathione conjugate (p-XSeSG)→aromatic selenol (p-XSeH)→TSC. Whether p-XSC or one of its metabolites is responsible for cancer prevention is the focus of this study. We utilized the DMBA-DNA binding assay with p-XSC as a positive control to evaluate the chemopreventive potential of p-XSC metabolites at dietary selenium levels of 10ppm. Rats were fed AIN-76A diet supplemented with various selenium compounds for 1 week prior to the oral administration of a single dose of [ 3H]DMBA (5mg per rat, specific activity 51.3mCi/mmol). The rats were sacrificed 24h later and DNA was isolated from the mammary fat pads. Relative levels of total binding were: [pmol/mg DNA, mean±S.D., n=6]; DMBA [7.2±1.6]; DMBA+p-XSC [3.5±2.7]; DMBA+p-XSeSG [2.2±1.1]; DMBA+TSC [5.6±2.9]. All selenium compounds, except TSC, significantly inhibited DMBA-DNA adduct formation; however, the difference between p-XSC and p-XSeSG was not statistically significant. The inhibition of total binding was attributed to a reduction in the formation of the three major adducts derived from bay-region diol epoxides of DMBA. On the basis of their chromatographic characteristics, these were identified as anti-diol-epoxide:deoxyguanosine, syn-diol-epoxide:deoxyadenosine, and anti-diol-epoxide:deoxyadenosine. Our results suggest that p-XSeSG, but not TSC, is the likely inhibitor of mammary cancer. Selenium levels measured by atomic absorption spectroscopy in the target organ (mammary fat pads) and in plasma following the dietary administration of selenium compounds were in the order of p-XSeSG≅p- XSC>TSC. These results appear to be consistent with their order of inhibitory effects on total DMBA-DNA binding. Further in vitro studies of the effect of selenium compounds on cell proliferation suggest that, depending on the dose and time point selected, p-XSC is comparable to or better than p-XSeSG; but both are more effective than TSC. Collectively, our in vivo and in vitro results indicate that p-XSC and its conjugate are better candidates than TSC for future studies on mammary cancer chemoprevention.
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U2 - 10.1016/j.cbi.2003.08.004
DO - 10.1016/j.cbi.2003.08.004
M3 - Article
C2 - 14597131
AN - SCOPUS:0142218067
SN - 0009-2797
VL - 146
SP - 179
EP - 190
JO - Chemico-Biological Interactions
JF - Chemico-Biological Interactions
IS - 2
ER -