TY - JOUR
T1 - Benzo[c]phenanthrene is activated to DNA-binding diol epoxides in the human mammary carcinoma cell line MCF-7 but only limited activation occurs in mouse skin
AU - Einolf, Heidi J.
AU - Amin, Shantu
AU - Yagi, Haruhiko
AU - Jerina, Donald M.
AU - Baird, William M.
N1 - Funding Information:
This work was supported in part by grants CA28825 and CA40228 (WMB) and contract no. N01-CP-21115 (SA) from the National Cancer Institute, DHHS. H.Einolf received support from a Purdue Research Foundation Graduate Fellowship.
PY - 1996/10
Y1 - 1996/10
N2 - Benzo[c]phenanthrene (B[c]Ph) is an environmental contaminant with low carcinogenic activity in rodent bioassays, B[c]Ph-3,4-diol-1,2-epoxides (B[c]PhDE), however, are among the most tumorigenic diol epoxides known. To determine whether human cells are capable of activating B[c]Ph to DNA-binding metabolites, cultures of the human mammary cell line, MCF-7, were exposed to 10 μM B[c]Ph for 48, 72 and 96 h or to 1 μM (±)-B[c]Ph-3,4-dihydrodiol for 48 h. The B[c]Ph-DNA adducts were analyzed by 33P-postlabeling and reverse-phase HPLC. The major B[c]Ph-DNA adducts were formed by the trans-addition of (4R,3S)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-B[c]Ph to deoxyadenosine [(-)-B[c]PhDE-2dA(t)] and by the cis- and trans-addition of (4S,3R)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-B[c]Ph to deoxyadenosine [(+)-B[c]PhDE-1dA(c) and (+)-B[c]PhDE-1dA(t). Smaller amounts of the trans-addition of (-)-B[c]PhDE-2 were bound to deoxyguanosine. To determine whether B[c]Ph can be metabolically activated to diol epoxides in mouse epidermis, female SENCAR mice were treated topically with 2 μmol B[c]Ph for 24, 48 or 72 h or with 0.4 μmol (±)-B[c]Ph-3,4-dihydrodiol for 24 or 48 h. In B[c]Ph-treated mice, only small amounts of three B[c]PhDE-DNA adducts were detected B[c]PhDE-2dA(t), (+)-B[c]PhDE-1dA(t) and (+)-B[c]PhDE-1dA(c)] at 24, 48 and 72 h. In contrast, mice treated topically with 0.4 μmol (±)-B[c]Ph-3,4-dihydrodiol formed B[c]PhDE-DNA adducts at levels 6-fold greater than those observed with B[c]Ph at 48 h. The higher formation of B[c]PhDE-DNA adducts by (±)-B[c]Ph-3,4-dihydrodiol correlates with the greater potency of (±)-B[c]Ph-3,4-dihydrodiol than of B[c]Ph as a tumor initiator in mouse skin. The low extent of formation of B[c]PhDE from B[c]Ph in mouse epidermis may explain the low tumorigenicity of B[c]Ph in this tissue. These results indicate activation of B[c]Ph in mouse skin and tumorigenesis results in that tissue may not adequately assess the potential capability of cells from humans to activate B[c]Ph to ultimate carcinogenic metabolites.
AB - Benzo[c]phenanthrene (B[c]Ph) is an environmental contaminant with low carcinogenic activity in rodent bioassays, B[c]Ph-3,4-diol-1,2-epoxides (B[c]PhDE), however, are among the most tumorigenic diol epoxides known. To determine whether human cells are capable of activating B[c]Ph to DNA-binding metabolites, cultures of the human mammary cell line, MCF-7, were exposed to 10 μM B[c]Ph for 48, 72 and 96 h or to 1 μM (±)-B[c]Ph-3,4-dihydrodiol for 48 h. The B[c]Ph-DNA adducts were analyzed by 33P-postlabeling and reverse-phase HPLC. The major B[c]Ph-DNA adducts were formed by the trans-addition of (4R,3S)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-B[c]Ph to deoxyadenosine [(-)-B[c]PhDE-2dA(t)] and by the cis- and trans-addition of (4S,3R)-dihydroxy-(2S,1R)-epoxy-1,2,3,4-tetrahydro-B[c]Ph to deoxyadenosine [(+)-B[c]PhDE-1dA(c) and (+)-B[c]PhDE-1dA(t). Smaller amounts of the trans-addition of (-)-B[c]PhDE-2 were bound to deoxyguanosine. To determine whether B[c]Ph can be metabolically activated to diol epoxides in mouse epidermis, female SENCAR mice were treated topically with 2 μmol B[c]Ph for 24, 48 or 72 h or with 0.4 μmol (±)-B[c]Ph-3,4-dihydrodiol for 24 or 48 h. In B[c]Ph-treated mice, only small amounts of three B[c]PhDE-DNA adducts were detected B[c]PhDE-2dA(t), (+)-B[c]PhDE-1dA(t) and (+)-B[c]PhDE-1dA(c)] at 24, 48 and 72 h. In contrast, mice treated topically with 0.4 μmol (±)-B[c]Ph-3,4-dihydrodiol formed B[c]PhDE-DNA adducts at levels 6-fold greater than those observed with B[c]Ph at 48 h. The higher formation of B[c]PhDE-DNA adducts by (±)-B[c]Ph-3,4-dihydrodiol correlates with the greater potency of (±)-B[c]Ph-3,4-dihydrodiol than of B[c]Ph as a tumor initiator in mouse skin. The low extent of formation of B[c]PhDE from B[c]Ph in mouse epidermis may explain the low tumorigenicity of B[c]Ph in this tissue. These results indicate activation of B[c]Ph in mouse skin and tumorigenesis results in that tissue may not adequately assess the potential capability of cells from humans to activate B[c]Ph to ultimate carcinogenic metabolites.
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U2 - 10.1093/carcin/17.10.2237
DO - 10.1093/carcin/17.10.2237
M3 - Article
C2 - 8895494
AN - SCOPUS:0029824917
SN - 0143-3334
VL - 17
SP - 2237
EP - 2244
JO - Carcinogenesis
JF - Carcinogenesis
IS - 10
ER -