Sabnis Gauri J, Jelovac Danijela, Long Brian, Brodie Angela
Department of Pharmacology and Experimental Therapeutics, University of Maryland Baltimore, Baltimore, Maryland 21201, USA.
Cancer Res. 2005 May 1;65(9):3903-10. doi: 10.1158/0008-5472.CAN-04-4092.
To study the long-term effects of estrogen deprivation on breast cancer, MCF-7Ca human estrogen receptor-positive breast cancer cells stably transfected with human aromatase gene were cultured in the steroid-depleted medium for 6 to 8 months until they had acquired the ability to grow. Proliferation of these cells (UMB-1Ca) was accompanied by increased expression of human epidermal growth factor receptor 2, increased activation of AKT through phosphorylation at Ser473 and Thr308, and increased invasion compared with parental MCF-7Ca cells. Estrogen receptor expression was also increased 5-fold. Although growth was inhibited by the antiestrogen fulvestrant, the IC50 was 100-fold higher than for parental MCF-7Ca cells. Aromatase inhibitor letrozole also inhibited growth at 10,000-fold higher concentration than required for MCF-7Ca cells, whereas anastrozole, exemestane, formestane, and tamoxifen were ineffective at 100 nmol/L. Growth of UMB-1Ca cells was inhibited by phosphatidylinositol 3-kinase inhibitor wortmannin (IC50 approximately 25 nmol/L) and epidermal growth factor receptor kinase inhibitor gefitinib (ZD 1839; IC50 approximately 10 micromol/L) whereas parental MCF-7Ca cells were insensitive to these agents. Concomitant treatment of UMB-1Ca cells with the signal transduction inhibitors and anastrozole and tamoxifen restored their growth inhibitory effects. These studies show that estrogen deprivation results in up-regulation of growth factor signaling pathways, which leads to a more aggressive and hormone refractory phenotype. Cross-talk between ER and growth factor signaling was evident as inhibition of these pathways could restore estrogen responsiveness to these cells.
为研究雌激素剥夺对乳腺癌的长期影响，将稳定转染人芳香化酶基因的MCF-7Ca人雌激素受体阳性乳腺癌细胞在类固醇缺乏的培养基中培养6至8个月，直至其获得生长能力。与亲代MCF-7Ca细胞相比，这些细胞（UMB-1Ca）的增殖伴随着人表皮生长因子受体2表达增加、AKT通过Ser473和Thr308磷酸化而激活增加以及侵袭增加。雌激素受体表达也增加了5倍。尽管抗雌激素氟维司群抑制了生长，但其IC50比亲代MCF-7Ca细胞高100倍。芳香化酶抑制剂来曲唑也以比MCF-7Ca细胞所需浓度高10000倍的浓度抑制生长，而阿那曲唑、依西美坦、福美坦和他莫昔芬在100 nmol/L时无效。UMB-1Ca细胞的生长受到磷脂酰肌醇3激酶抑制剂渥曼青霉素（IC50约25 nmol/L）和表皮生长因子受体激酶抑制剂吉非替尼（ZD 1839；IC50约10 μmol/L）的抑制，而亲代MCF-7Ca细胞对这些药物不敏感。用信号转导抑制剂与阿那曲唑和他莫昔芬联合处理UMB-1Ca细胞可恢复其生长抑制作用。这些研究表明，雌激素剥夺导致生长因子信号通路上调，从而导致更具侵袭性和激素难治性的表型。雌激素受体与生长因子信号之间的相互作用很明显，因为抑制这些通路可恢复这些细胞对雌激素的反应性。
