Klinik für Gynäkologie, Universität Halle, Halle/Saale, Germany.
PLoS One. 2013;8(1):e54261. doi: 10.1371/journal.pone.0054261. Epub 2013 Jan 18.
Cellular functions are regulated by complex networks of many different signaling pathways. The TGFβ and cAMP pathways are of particular importance in tumor progression. We analyzed the cross-talk between these pathways in breast cancer cells in 2D and 3D cultures. We found that cAMP potentiated TGFβ-dependent gene expression by enhancing Smad3 phosphorylation. Higher levels of total Smad3, as observed in 3D-cultured cells, blocked this effect. Two Smad3 regulating proteins, YAP (Yes-associated protein) and TβRI (TGFβ receptor 1), were responsive to cAMP. While YAP had little effect on TGFβ-dependent expression and Smad3 phosphorylation, a constitutively active form of TβRI mimicked the cAMP effect on TGFβ signaling. In 3D-cultured cells, which show much higher levels of TβRI and cAMP, TβRI was unresponsive to cAMP. Upregulation of TβRI expression by cAMP was dependent on transcription. A proximal TβRI promoter fragment was moderately, but significantly activated by cAMP suggesting that cAMP increases TβRI expression at least partially by activating TβRI transcription. Neither the cAMP-responsive element binding protein (CREB) nor the TβRI-regulating transcription factor Six1 was required for the cAMP effect. An inhibitor of histone deacetylases alone or together with cAMP increased TβRI expression by a similar extent as cAMP alone suggesting that cAMP may exert its effect by interfering with histone acetylation. Along with an additive stimulatory effect of cAMP and TGFβ on p21 expression an additive inhibitory effect of these agents on proliferation was observed. Finally, we show that mesenchymal stem cells that interact with breast cancer cells can simultaneously activate the cAMP and TGFβ pathways. In summary, these data suggest that combined effects of cAMP and TGFβ, as e.g. induced by mesenchymal stem cells, involve the upregulation of TβRI expression on the transcriptional level, likely due to changes in histone acetylation. As a consequence, cancer cell functions such as proliferation are affected.
细胞功能受到许多不同信号通路组成的复杂网络的调节。TGFβ 和 cAMP 通路在肿瘤进展中尤为重要。我们分析了在 2D 和 3D 培养物中的乳腺癌细胞中这些通路之间的串扰。我们发现，cAMP 通过增强 Smad3 磷酸化增强了 TGFβ 依赖性基因表达。在 3D 培养细胞中观察到的更高水平的总 Smad3 阻断了这种作用。两种调节 Smad3 的蛋白质，YAP（Yes 相关蛋白）和 TβRI（TGFβ 受体 1），对 cAMP 有反应。虽然 YAP 对 TGFβ 依赖性表达和 Smad3 磷酸化几乎没有影响，但组成型激活形式的 TβRI 模拟了 cAMP 对 TGFβ 信号的作用。在 3D 培养细胞中，TβRI 和 cAMP 的水平明显升高，TβRI 对 cAMP 无反应。cAMP 上调 TβRI 表达依赖于转录。cAMP 适度但显著激活 TβRI 启动子片段，表明 cAMP 通过激活 TβRI 转录至少部分增加 TβRI 表达。cAMP 效应既不需要 cAMP 反应元件结合蛋白 (CREB) 也不需要调节 TβRI 转录的转录因子 Six1。单独的组蛋白去乙酰化酶抑制剂或与 cAMP 一起增加 TβRI 表达的程度与 cAMP 相似，表明 cAMP 可能通过干扰组蛋白乙酰化来发挥其作用。cAMP 和 TGFβ 对 p21 表达的相加刺激作用伴随着这些药物对增殖的相加抑制作用。最后，我们表明与乳腺癌细胞相互作用的间充质干细胞可以同时激活 cAMP 和 TGFβ 通路。总之，这些数据表明，cAMP 和 TGFβ 的联合效应，例如由间充质干细胞诱导的，涉及 TβRI 表达的转录水平上调，可能是由于组蛋白乙酰化的变化。因此，受影响的是癌症细胞的功能，如增殖。
