Jelovac Danijela, Sabnis Gauri, Long Brian J, Macedo Luciana, Goloubeva Olga G, Brodie Angela M H
Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Cancer Res. 2005 Jun 15;65(12):5380-9. doi: 10.1158/0008-5472.CAN-04-4502.
Ovariectomized mice bearing tumor xenografts grown from aromatase-transfected estrogen receptor (ER)-positive human breast cancer cells (MCF-7Ca) were injected s.c. with 10 microg/d letrozole for up to 56 weeks. Western blot analysis of the tumors revealed that ERs (ERalpha) were increased at 4 weeks but decreased at weeks 28 and 56. Expression of erbB-2 and p-Shc increased throughout treatment, whereas growth factor receptor binding protein 2 (Grb2) increased only in tumors proliferating on letrozole (weeks 28 and 56). In cells isolated from tumors after 56 weeks and maintained as a cell line (LTLT-Ca) in 1 micromol/L letrozole, ERalpha was also decreased whereas erbB-2, adapter proteins (p-Shc and Grb2), and the signaling proteins in the mitogen-activated protein kinase (MAPK) cascade were increased compared with MCF-7Ca cells. Growth was inhibited in LTLT-Ca cells but not in MCF-7Ca cells treated with MAPK kinase 1/2 inhibitors U0126, and PD98059 (IC(50) approximately 25 micromol/L). PD98059 (5 micromol/L) also reduced MAPK activity and increased ERalpha to the levels in MCF-7Ca cells. Epidermal growth factor receptor kinase inhibitor, gefitinib (ZD1839) inhibited growth of LTLT-Ca cells (IC(50) approximately 10 micromol/L) and restored their sensitivity to tamoxifen and anastrozole. In xenografts, combined treatment with ER down-regulator fulvestrant and letrozole, prevented increases in erbB-2 and activation of MAPK and was highly effective in inhibiting tumor growth throughout 29 weeks of treatment. These results indicate that blocking both ER- and growth factor-mediated transcription resulted in the most effective inhibition of growth of ER-positive breast cancer cells.
将转染芳香化酶的雌激素受体（ER）阳性人乳腺癌细胞（MCF-7Ca）接种建立肿瘤异种移植模型的去卵巢小鼠，皮下注射10μg/d来曲唑，持续56周。对肿瘤进行蛋白质免疫印迹分析显示，ER（ERα）在4周时增加，但在28周和56周时减少。在整个治疗过程中，erbB-2和p-Shc的表达增加，而生长因子受体结合蛋白2（Grb2）仅在来曲唑作用下增殖的肿瘤中增加（28周和56周）。在56周后从肿瘤中分离并在1μmol/L来曲唑中维持为细胞系（LTLT-Ca）的细胞中，与MCF-7Ca细胞相比，ERα也减少，而erbB-2、衔接蛋白（p-Shc和Grb2）以及丝裂原活化蛋白激酶（MAPK）级联中的信号蛋白增加。LTLT-Ca细胞的生长受到抑制，但用MAPK激酶1/2抑制剂U0126和PD98059（IC50约25μmol/L）处理的MCF-7Ca细胞生长未受抑制。PD98059（5μmol/L）也降低了MAPK活性，并使ERα增加至MCF-7Ca细胞中的水平。表皮生长因子受体激酶抑制剂吉非替尼（ZD1839）抑制LTLT-Ca细胞的生长（IC50约10μmol/L），并恢复其对他莫昔芬和阿那曲唑的敏感性。在异种移植模型中，ER下调剂氟维司群与来曲唑联合治疗可防止erbB-2增加和MAPK激活，并且在整个29周的治疗过程中对抑制肿瘤生长非常有效。这些结果表明，同时阻断ER和生长因子介导的转录可最有效地抑制ER阳性乳腺癌细胞的生长。
