Collins Nicole L, Reginato Maurico J, Paulus Jessica K, Sgroi Dennis C, Labaer Joshua, Brugge Joan S
Department of Cell Biology, Harvard Medical School, 240 Longwood Ave., Boston, MA 02115, USA.
Mol Cell Biol. 2005 Jun;25(12):5282-91. doi: 10.1128/MCB.25.12.5282-5291.2005.
Proper attachment to the extracellular matrix is essential for cell survival. Detachment from the extracellular matrix results in an apoptotic process termed anoikis. Anoikis induction in MCF-10A mammary epithelial cells is due not only to loss of survival signals following integrin disengagement, but also to consequent downregulation of epidermal growth factor (EGFR) and loss of EGFR-induced survival signals. Here we demonstrate that G(1)/S arrest by overexpression of the cyclin-dependent kinase inhibitors p16(INK4a), p21(Cip1), or p27(Kip1) or by treatment with mimosine or aphidicolin confers anoikis resistance in MCF-10A cells. G(1)/S arrest-mediated anoikis resistance involves suppression of the BH3-only protein Bim. Furthermore, in G(1)/S-arrested cells, Erk phosphorylation is maintained in suspension and is necessary for Bim suppression. Following G(1)/S arrest, known proteins upstream of Erk, including Raf and Mek, are not activated. However, retained Erk activation under conditions in which Raf and Mek activation is lost is observed, suggesting that G(1)/S arrest acts at the level of Erk dephosphorylation. Thus, anoikis resistance by G(1)/S arrest is mediated by a mechanism involving Bim suppression through maintenance of Erk activation. These results provide a novel link between cell cycle arrest and survival, and this mechanism could contribute to the survival of nonreplicating, dormant tumor cells that avert apoptosis during early stages of metastasis.
与细胞外基质的适当附着对于细胞存活至关重要。从细胞外基质脱离会导致一种称为失巢凋亡的凋亡过程。MCF - 10A乳腺上皮细胞中失巢凋亡的诱导不仅归因于整合素脱离后存活信号的丧失，还归因于随后表皮生长因子（EGFR）的下调以及EGFR诱导的存活信号的丧失。在这里，我们证明通过过表达细胞周期蛋白依赖性激酶抑制剂p16(INK4a)、p21(Cip1)或p27(Kip1)，或用含羞草碱或阿非迪霉素处理使细胞停滞在G(1)/S期，可赋予MCF - 10A细胞失巢凋亡抗性。G(1)/S期停滞介导的失巢凋亡抗性涉及对仅含BH3结构域蛋白Bim的抑制。此外，在G(1)/S期停滞的细胞中，悬浮状态下Erk磷酸化得以维持，这对于抑制Bim是必需的。在G(1)/S期停滞之后，已知的Erk上游蛋白，包括Raf和Mek，并未被激活。然而，在Raf和Mek激活丧失的条件下仍观察到Erk的持续激活，这表明G(1)/S期停滞作用于Erk去磷酸化水平。因此，G(1)/S期停滞介导的失巢凋亡抗性是通过一种涉及通过维持Erk激活来抑制Bim的机制实现的。这些结果在细胞周期停滞与存活之间建立了一种新的联系，并且这种机制可能有助于非复制性、休眠的肿瘤细胞在转移早期避免凋亡而存活。
