Telang N T, Suto A, Wong G Y, Osborne M P, Bradlow H L
Breast Cancer Research Laboratory, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
J Natl Cancer Inst. 1992 Apr 15;84(8):634-8. doi: 10.1093/jnci/84.8.634.
Estrogens are potent mammary tumor promoters influencing post-initiation events via epigenetic mechanisms. The upregulation (i.e., induction) of the C16 alpha-hydroxylation pathway during 17 beta-estradiol (E2) biotransformation has been associated with mammary cell transformation. The action of E2 metabolites on tumorigenic transformation, however, is poorly understood.
The newly established mammary epithelial cell line C57/MG, derived from the C57BL mouse strain, was used to examine whether E2 or its metabolites, 16-hydroxyestrone (16 alpha-OHE1) and estriol (E3), function as initiators of mammary cell transformation.
DNA repair (hydroxyurea-insensitive thymidine uptake), estrogen metabolism (3H exchange to form 3H2O), hyperproliferation (increased cell number), and acquisition of anchorage-independent growth (soft-agar colonies) were used as quantitative end points to measure the relative extent of transformation.
Treatment of cells with 200 ng/mL 16 alpha-OHE1 resulted in a 55.2% increase in DNA repair synthesis, a 23.09% increase in proliferative activity, and a 18-fold increase in the number of soft-agar colonies, relative to the solvent controls (P less than .0001). The extent of upregulation of the three end points was similar to that induced by the genotoxic mammary carcinogen 7, 12-dimethylbenz[a]anthracene (DMBA, positive control). DMBA treatment also upregulated the ratio of 16 alpha/C2 hydroxylation of E2 leading to increased formation of 16 alpha-OHE1. E2 and E3 were not effective in upregulating these markers for transformation.
These results demonstrate that in nontransformed C57/MG cells, 16 alpha-OHE1 may function as an initiator, perturbing the intermediate biomarkers for preneoplastic transformation.
雌激素是强大的乳腺肿瘤促进剂，通过表观遗传机制影响启动后的事件。在17β-雌二醇（E2）生物转化过程中，C16α-羟化途径的上调（即诱导）与乳腺细胞转化有关。然而，E2代谢产物对致瘤转化的作用尚不清楚。
使用新建立的源自C57BL小鼠品系的乳腺上皮细胞系C57/MG，来检测E2或其代谢产物16-羟雌酮（16α-OHE1）和雌三醇（E3）是否作为乳腺细胞转化的启动剂。
DNA修复（羟基脲不敏感的胸苷摄取）、雌激素代谢（3H交换形成3H2O）、过度增殖（细胞数量增加）以及获得非锚定依赖性生长（软琼脂集落）被用作定量终点，以测量转化的相对程度。
相对于溶剂对照，用200 ng/mL 16α-OHE1处理细胞导致DNA修复合成增加55.2%，增殖活性增加23.09%，软琼脂集落数量增加18倍（P小于0.0001）。这三个终点的上调程度与遗传毒性乳腺致癌物7,12-二甲基苯并[a]蒽（DMBA，阳性对照）诱导的相似。DMBA处理还上调了E2的16α/C2羟化比率，导致16α-OHE1形成增加。E2和E3在上调这些转化标志物方面无效。
这些结果表明，在未转化的C57/MG细胞中，16α-OHE1可能作为启动剂，扰乱肿瘤前转化的中间生物标志物。
