ALKYL PCDFS--INHIBITION OF MAMMARY CANCER

以往的研究表明，2，3，7，8-四氯二苯并-p- 二恶英(TCDD)抑制雌激素诱导的大鼠脑内多种反应 雌性大鼠子宫和MCF-7人乳腺癌细胞。TCDD还 抑制大鼠和小鼠乳腺移植瘤的形成 Mcf-7细胞。6-甲基-1，3，8-三氯二苯并呋喃及其相关化合物 烷基多氯二苯并呋喃(PCDF)是相对无毒的类似物 TCDD在体外和体内表现出类似的抗雌激素和 抗肿瘤活性。因此，烷基多氯二苯并呋喃代表了一类新的 通过芳香烃受体信号起作用的抗雌激素 转导途径，因此可能具有临床应用潜力。 治疗乳腺癌的化疗药物。TCDD和MCDF，是 T47D和MCF-7人乳腺癌细胞(ER-和 AHR阳性，ER+AhR+)，但在ER-AhR-MDA-MB-231中活性最低 细胞。烷基PCDFS或TCDD对ER-AhR+的体内外作用 或ER+AhR-细胞之前没有被研究过，因为 无法获得这些细胞系。该项目的实验1将 一系列ER-AhR+和ER+AhR变异型乳房的特征 癌细胞系。ER+AhR-细胞将通过培养MCF-7和 1微摩尔苯并[a]芘(BaP)和ER+AhR变异体中的T47D细胞 细胞系将被充分描述。Er-AhR+变异细胞将是 从高传代T47D细胞和MDA-MB-231细胞(ER-AhR-)中分离得到 稳定地转染人ARNT基因，恢复了阿- 这一细胞系的反应性。所得到的稳定的转染体将 代表迄今尚未描述的ER-AhR+表型。 此外，由于MDA-MB-231细胞对内分泌和细胞毒性具有抵抗力 药物治疗，ER-AhR+细胞将作为评估 AhR激动剂(如烷基)的抗肿瘤和抗增殖作用 多氯二苯并呋喃)。虽然MDA-MB-231细胞的生长 雌激素非依赖性，多种生长因子(胰岛素样生长因子-L，表皮生长因子，转化生长因子α， 胰岛素)作为有丝分裂原，因此由生长因子诱导 ER-AhR+稳定的增殖和其他一些特征 将对转基因细胞系进行彻底的调查。免疫缺陷 移植了乳腺癌细胞的小鼠将被用于实验 2(A)确定控制肿瘤发展的因素 裸鼠移植野生型和变异型乳腺癌 实验1和(B)中描述的细胞系评估相对 TCDD和烷基PCDF作为化疗药物在本研究中的潜力 活体模型。在平行研究中，烷基的相对势能 作为抗雌激素的PCDF也将在雌性大鼠子宫中被确定。 这些短期研究将提供关键的相对效力数据 这一系列烷基多氯二苯并呋喃对雌激素具有良好的反应性 靶器官及其在活体研究中的优先使用(实验4) DMBA诱导的大鼠肿瘤模型中部分同系物的抗癌活性 模特。这些拟议的研究将提供有关 AhR激动剂作为抗雌激素和抗肿瘤作用的机制 在两个体内模型中的药物，并确定哪些烷基PCDF应该是 进一步研究作为治疗食道癌的潜在化疗药物 乳腺癌。

Previous studies have demonstrated that 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD) inhibits a broad spectrum of estrogen-induced responses in the female rat uterus and in MCF-7 human breast cancer cells. TCDD also inhibits mammary tumor formation in rats and in mice transplanted with MCF-7 cells. 6-Methyl-1,3,8-trichlorodibenzofuran (MCDF) and related alkyl polychlorodibenzofurans (PCDFs) are relatively non-toxic analogs of TCDD which exhibit comparable in vitro and in vivo antiestrogenic and antitumorigenic activities. Thus, the alkyl PCDFs represent a new class of antiestrogens which act through the aryl hydrocarbon (Ah) receptor signal transduction pathway and thus may have clinical potential as chemotherapeutic agents for treatment of breast cancer. TCDD and MCDF, are potent antiestrogens in T47D and MCF-7 human breast cancer cells (ER- and AhR-positive, ER+AhR+) but exhibit minimal activity in ER-AhR- MDA-MB-231 cells. The in vitro or in vivo effects of alkyl PCDFs or TCDD on ER-AhR+ or ER+AhR- cells have not been previously investigated due to the unavailability of these cell lines. Experiment 1 of this project will thoroughly characterize a series of ER-AhR+ and ER+AhR- variant breast cancer cell lines. ER+AhR- cells will be isolated by culturing MCF-7 and T47D cells in 1 micromole benzo[a]pyrene (BaP) and the ER+AhR- variant cell lines will be fully characterized. ER-AhR+ variant cells will be isolated from high passage T47D cells and from MDA-MB-231 cells (ER-AhR-) stably transfected with the human arnt gene which restores Ah- responsiveness in this cell line. The resultant stable transfectants will represent an ER-AhR+ phenotype which hitherto has not been described. Moreover, since MDA-MB-231 cells are resistant to endocrine and cytotoxic drug therapy, the ER-AhR+ cells will serve as a model for assessing the antitumorigenic and antiproliferative effects of AhR agonists (e.g. alkyl PCDFs) in these cells. Although the growth of MDA-MB-231 cells are estrogen-independent, various growth factors (IGF-l, EGF, TGFalpha, insulin) act as mitogens and, therefore, growth factor-induced proliferation and a number of other characteristics of the ER-AhR+ stable transfectant cell lines will be thoroughly.investigated. Immune deficient mice transplanted with breast cancer cells will be utilized in Experiment 2 to (a) determine the factors which control the development of tumors in athymic mice transplanted with the wild-type and variant breast cancer cell lines characterized in Experiment 1 and (b) assess the relative potencies of TCDD and the alkyl PCDFs as chemotherapeutic agents in this in vivo model. In parallel studies, the relative potencies of the alkyl PCDF as antiestrogens will also be determined in the female rat uterus. These short-term studies will provide critical relative potency data for this series of alkyl PCDFs in a well-established estrogen-responsive target organ and prioritize their use in in vivo studies (Experiment 4) on the antitumorigenicity of selected congeners in the DMBA-induced rat tumor model. These proposed studies will provide critical new data on the mechanism of action of AhR agonists as antiestrogens and antitumorigenic agents in two in vivo models and determine which alkyl PCDFs should be further investigated as potential chemotherapeutic agents for treatment of mammary cancer.