1,25-DIHYDROXYVITAMIN-D3 BINDING IN ESTROGEN-RESPONSIVE RAT BREAST-TUMOR
1,25-DIHYDROXYVITAMIN-D3 BINDING IN ESTROGEN-RESPONSIVE RAT BREAST-TUMOR
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DOI：
10.1210/endo-119-1-397
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发表时间：
1986-07-01
期刊：
影响因子：
4.8
通讯作者：
COOMBES, RC
中科院分区：
文献类型：
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作者：
COLSTON, K;WILKINSON, JR;COOMBES, RC
1,25-二羟基维生素D3受体[1,25-(OH)2D3]已在乳腺组织中报道；然而，多个结合位点的存在和有限的人类肿瘤组织的可用性阻碍了对乳腺癌受体的完整生化表征。本研究采用大鼠乳腺癌模型，分析了乳腺肿瘤组织中125 -(OH)2D3的结合蛋白。用致癌物亚硝基甲基脲诱导成年雌性大鼠乳腺肿瘤。这类肿瘤先前已被证明具有高水平的雌激素受体，并且依赖于雌激素。用蔗糖密度梯度分析0.3 M KCl肿瘤组织提取物中1,25-(OH)2D3的结合蛋白。在蔗糖密度梯度上分析了两种结合蛋白。检测到两种结合蛋白：一种是在5-6秒时沉淀，代表125 -(OH)2D3与25羟基维生素D3 （25OHD3）结合蛋白的结合；另一种是像大鼠肠道受体一样，在3.3秒时沉淀，二羟基代谢物与更快沉积蛋白的结合可以通过在孵育培养基中加入放射性25OHD3来消除。采用羟基磷灰石法研究大鼠乳腺肿瘤的受体含量，方法是用饱和浓度的1,25-(OH)2-[3H]D3和未标记的250HD3培养肿瘤提取物，以消除激素与5-6-S物种的结合。经Scatchard分析，125 -(OH)2D3与肿瘤提取物结合的表观解离常数（Kd）为0.33 nM。总之，亚硝基甲基脲诱导的大鼠乳腺肿瘤显示含有高亲和力的1,25-(OH)2D3受体，其性质与其他哺乳动物靶器官中受体的性质非常相似。在这些大鼠乳腺肿瘤中存在125 -(OH)2D3受体，这表明该组织可能对激素有反应。
Receptors for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] have been reported in breast tissue; however, the presence of multiple binding sites and limited availability of human tumor tissue have precluded complete biochemical characterization of the receptor in breast cancer. In the present study, binding proteins for 1,25-(OH)2D3 in breast tumor tissue were analyzed using a rat model of breast cancer. Breast tumors were induced in adult female rats with the carcinogen nitrosomethylurea. Such tumors previously have been shown to possess high levels of estrogen receptors and are estrogen dependent. Binding proteins for 1,25-(OH)2D3 in 0.3 M KCl extracts of tumor tissue were analyzed on sucrose density gradients. Two binding proteins were analyzed on sucrose density gradients. Two binding proteins were detected: one sedimenting at 5-6 S representing binding of 1,25-(OH)2D3 to the 25 hydroxyvitamin D3 (25OHD3) binding protein and a second moiety sedimenting, like the rat intestinal receptor, at 3.3 S. Binding of the dihydroxy metabolite to the faster sedimenting protein could be eliminated by inclusion of radioinert 25OHD3 in the incubation medium. Receptor content of rat breast tumor was investigated using an hydroxylapatite assay by incubating tumor extracts with a saturating concentration of 1,25-(OH)2-[3H]D3, plus unlabeled 250HD3 to eliminate binding of the hormone to the 5-6-S species. Scatchard analysis of 1,25-(OH)2D3 binding to the tumor extracts yielded on apparent dissociation constant (Kd) of 0.33 nM. In summary, breast tumors induced in rats by nitrosomethylurea were shown to contain high affinity 1,25-(OH)2D3 receptors with properties very similar to those reported for the receptor in other mammalian target organs. The presence of receptors for 1,25-(OH)2D3 in these rat breast tumors implies that the tissue is potentially responsive to the hormone.