Yang Shangxin, Lim Minyoung, Pham Linda K, Kendall Stephen E, Reddi A Hari, Altieri Dario C, Roy-Burman Pradip
Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
Cancer Res. 2006 Apr 15;66(8):4285-90. doi: 10.1158/0008-5472.CAN-05-4456.
We reported earlier that exposure to exogenous bone morphogenetic protein 7 (BMP7) could strongly inhibit serum starvation-induced apoptosis to C4-2B cell line, a variant of the LNCaP human prostate cancer cell line with propensity for bone metastasis. Whereas serum starvation suppressed the expression of survivin, a member of the inhibitor of apoptosis protein family, its expression was sustained in the presence of BMP7. In this study, we present evidence that BMP7 exposure up-regulated survivin promoter activity, an effect that was associated with activation of Smad, and could be repressed by dominant-negative Smad5. Additionally, serum starvation-induced suppression of c-jun NH2-terminal kinase (JNK) activity in C4-2B cells could be mostly restored by BMP7, and a JNK inhibitor could counteract the antiapoptotic effect of BMP7, without a significant effect on the level of survivin expression. Thus, we identified JNK pathway as another signaling mode for the antiapoptotic function of BMP7. To test the effect of endogenous up-regulation of BMP7, we genetically modulated the C4-2B cell line to overexpress BMP7 protein. Not only was this altered cell line resistant to serum starvation-induced apoptosis but it also exhibited patterns of Smad activation, survivin up-regulation, and JNK activation similar to those of the parental C4-2B cells exposed to exogenous BMP7. Consistent with these in vitro findings of BMP7 action, we acquired correlative results of Smad activation, survivin expression, and JNK activation in the progression of prostate cancer in the conditional Pten deletion mouse model, in which we first obtained the evidence of BMP7 overexpression.
我们之前报道过，外源性骨形态发生蛋白7（BMP7）的暴露可强烈抑制血清饥饿诱导的C4-2B细胞系凋亡，C4-2B细胞系是LNCaP人前列腺癌细胞系的一个变体，具有骨转移倾向。血清饥饿会抑制凋亡抑制蛋白家族成员survivin的表达，而在BMP7存在的情况下其表达得以维持。在本研究中，我们提供证据表明，BMP7暴露上调了survivin启动子活性，这一效应与Smad的激活相关，且可被显性负性Smad5抑制。此外，血清饥饿诱导的C4-2B细胞中c-jun氨基末端激酶（JNK）活性的抑制大部分可被BMP7恢复，并且一种JNK抑制剂可抵消BMP7的抗凋亡作用，而对survivin表达水平无显著影响。因此，我们确定JNK通路是BMP7抗凋亡功能的另一种信号传导模式。为了测试内源性上调BMP7的作用，我们对C4-2B细胞系进行基因改造以使其过表达BMP7蛋白。这种改变后的细胞系不仅对血清饥饿诱导的凋亡具有抗性，而且还表现出与暴露于外源性BMP7的亲代C4-2B细胞相似的Smad激活、survivin上调和JNK激活模式。与这些关于BMP7作用的体外研究结果一致我们在条件性Pten缺失小鼠模型中获得了前列腺癌进展过程中Smad激活、survivin表达和JNK激活的相关结果，在该模型中我们首先获得了BMP7过表达的证据。
