Kijima Ikuko, Itoh Toru, Chen Shiuan
Department of Surgical Research, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, CA 91010, USA.
J Steroid Biochem Mol Biol. 2005 Dec;97(4):360-8. doi: 10.1016/j.jsbmb.2005.09.003. Epub 2005 Nov 2.
Two third-generation aromatase inhibitors, letrozole and anastrozole, and the antiestrogen tamoxifen, were compared for growth-inhibiting activity in two estrogen receptor (ER)-positive aromatase-overexpressing human breast cancer cell lines, MCF-7aro and T-47Daro. Inhibition of hormone (1 nM testosterone)-stimulated proliferation was evaluated in both monolayer cultures and in three-dimensional spheroid cultures. Letrozole and anastrozole were also compared for effectiveness of aromatase inhibition, and relative affinity for aromatase, under both monolayer and spheroid growth conditions. Letrozole was an effective inhibitor of MCF-7aro monolayer cell proliferation, with an estimated 50% inhibitory concentration (IC50) of 50-100 nM, whereas an IC50 was not reached with anastrozole at any concentration tested (100-500 nM). An IC50 of tamoxifen was 1000 nM. Proliferation of T-47Daro monolayer cells was more sensitive to inhibition by all three agents; as with MCF-7aro cells, letrozole was the most effective inhibitor. MCF-7aro spheroids were slightly less sensitive than monolayer cells proliferation-inhibiting effects of letrozole (IC50 about 200 nM), and there was no significant inhibition with 100-200 nM anastrozole or 200-1000 nM tamoxifen. Letrozole and anastrozole significantly inhibited T-47Daro spheroid cell proliferation, at 15-25 and 50 nM, respectively, consistent with the greater sensitivity of T-47Daro monolayer cells to inhibition of proliferation by these agents. Tamoxifen failed to significantly inhibit T-47Daro spheroid cell proliferation over a 100-500 nM concentration range. Determination of aromatase inhibition in monolayers of both cell lines by a direct-access microsomal assay and an intact-cell assay revealed that letrozole was more active than anastrozole in monolayers of both cell lines and in both assays. In MCF-7aro spheroids following cell lysis, only letrozole significantly inhibited aromatase activity, supporting the conclusion that letrozole binds stronger to aromatase than anastrozole does. Our results demonstrate that MCF-7aro and T-47Daro spheroids could be a suitable model for evaluation of growth-inhibitory effects of agents used in hormonal therapy of breast cancer.
在两种雌激素受体（ER）阳性且芳香化酶过表达的人乳腺癌细胞系MCF-7aro和T-47Daro中，比较了两种第三代芳香化酶抑制剂来曲唑和阿那曲唑以及抗雌激素他莫昔芬的生长抑制活性。在单层培养和三维球体培养中评估了激素（1 nM睾酮）刺激的增殖抑制情况。还比较了来曲唑和阿那曲唑在单层和球体生长条件下的芳香化酶抑制效果以及对芳香化酶的相对亲和力。来曲唑是MCF-7aro单层细胞增殖的有效抑制剂，估计50%抑制浓度（IC50）为50 - 10 nM，而在任何测试浓度（100 - 500 nM）下阿那曲唑都未达到IC50。他莫昔芬的IC50为1000 nM。T-47Daro单层细胞的增殖对所有三种药物的抑制更敏感；与MCF-7aro细胞一样，来曲唑是最有效的抑制剂。MCF-7aro球体对来曲唑增殖抑制作用的敏感性略低于单层细胞（IC50约为200 nM），100 - 200 nM阿那曲唑或200 - 1000 nM他莫昔芬无明显抑制作用。来曲唑和阿那曲唑分别在15 - 25 nM和50 nM时显著抑制T-47Daro球体细胞增殖，这与T-47Daro单层细胞对这些药物增殖抑制作用更敏感一致。在100 - 500 nM浓度范围内，他莫昔芬未能显著抑制T-47Daro球体细胞增殖。通过直接接入微粒体测定法和完整细胞测定法对两种细胞系单层中的芳香化酶抑制进行测定，结果显示在两种细胞系的单层以及两种测定方法中，来曲唑比阿那曲唑更具活性。在MCF-7aro球体细胞裂解后，只有来曲唑显著抑制芳香化酶活性，支持来曲唑比阿那曲唑与芳香化酶结合更强的结论。我们的结果表明，MCF-7aro和T-47Daro球体可能是评估用于乳腺癌激素治疗药物生长抑制作用的合适模型。
