Koli K M, Ramsey T T, Ko Y, Dugger T C, Brattain M G, Arteaga C L
Department of Medicine,Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
J Biol Chem. 1997 Mar 28;272(13):8296-302. doi: 10.1074/jbc.272.13.8296.
We have studied the role of autocrine transforming growth factor-beta (TGF-beta) signaling on antiestrogen-mediated growth inhibition of hormone-dependent T47D and MCF-7 human breast carcinoma cells. Tamoxifen treatment increased the secretion of TGF-beta activity into serum-free cell medium and the cellular content of affinity cross-linked type I and III TGF-beta receptors in both cell lines. Anti-pan-TGF-beta antibodies did not block anti-estrogen-induced recruitment in G1 and inhibition of anchorage-dependent and -independent growth of both cell lines. Early passage MCF-7 cells, which exhibit detectable type II TGF-beta receptors at the cell surface and exquisite sensitivity to exogenous TGF-beta1, were transfected with a tetracycline-controllable dominant-negative TGF-betaRII (DeltaRII) construct. Although the TGF-beta1 response was blocked by removal of tetracycline in MCF-7/DeltaRII cells, tamoxifen-mediated suppression of Rb phosphorylation, recruitment in G1, and inhibition of cell proliferation were identical in the presence and absence of tetracycline. TGF-beta1 treatment up-regulated the Cdk inhibitor p21 and induced its association with Cdk2 in MCF-7 cells; these responses were blocked by the DeltaRII transgene product. In MCF-7 cells with a functional TGF-beta signaling pathway, tamoxifen did not up-regulate p21 nor did it induce association of p21 with Cdk2, suggesting alternative mechanisms for antiestrogen-mediated cytostasis. Finally, transfection of late-passage, TGF-beta1 unresponsive MCF-7 cells with high levels of TGF-betaRII restored TGF-beta1-induced growth inhibition but did not enhance tamoxifen response in culture. Taken together these data strongly argue against any role for TGF-beta signaling on tamoxifen-mediated growth inhibition of hormone-dependent breast cancer cells.
我们研究了自分泌转化生长因子-β（TGF-β）信号传导在抗雌激素介导的激素依赖性T47D和MCF-7人乳腺癌细胞生长抑制中的作用。他莫昔芬处理增加了无血清细胞培养基中TGF-β活性的分泌以及两种细胞系中亲和交联的I型和III型TGF-β受体的细胞含量。抗泛TGF-β抗体并未阻断抗雌激素诱导的G1期募集以及两种细胞系的贴壁依赖性和非贴壁依赖性生长的抑制。早期传代的MCF-7细胞在细胞表面表现出可检测到的II型TGF-β受体，并且对外源TGF-β1极为敏感，用四环素可控的显性负性TGF-βRII（DeltaRII）构建体进行转染。尽管在MCF-7/DeltaRII细胞中去除四环素可阻断TGF-β1反应，但在有或没有四环素的情况下，他莫昔芬介导的Rb磷酸化抑制、G1期募集以及细胞增殖抑制是相同的。TGF-β1处理上调了MCF-7细胞中的细胞周期蛋白依赖性激酶抑制剂p21并诱导其与Cdk2结合；这些反应被DeltaRII转基因产物阻断。在具有功能性TGF-β信号通路的MCF-7细胞中，他莫昔芬既不上调p21，也不诱导p21与Cdk2结合，提示抗雌激素介导的细胞停滞存在其他机制。最后，用高水平的TGF-βRII转染晚期传代、对TGF-β1无反应的MCF-7细胞可恢复TGF-β1诱导的生长抑制，但并未增强培养物中他莫昔芬的反应。综上所述，这些数据有力地反驳了TGF-β信号传导在他莫昔芬介导的激素依赖性乳腺癌细胞生长抑制中起任何作用的观点。
