Cosgaya J M, Perona R, Aranda A
Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Ciéntificas, Madrid, Spain.
Oncogene. 1997 Feb 6;14(5):579-87. doi: 10.1038/sj.onc.1200865.
Conditioned medium from PC12 cells incubated with retinoic acid (RA) increases [3H]thymidine incorporation in normal rat kidney (NRK) fibroblasts and 3D9 epithelial cells. The medium also causes anchorage-independent growth of NRK cells, which is strongly potentiated either in the presence of EGF or after activation of latent forms of transforming growth factors (TGFs) by acidification. These results suggest that RA regulates the release of more than one growth factor by PC12 cells. Conditioned media from control or NGF-treated PC12 cells causes growth of NRK cells in soft agar only after acidification. An increase in expression of the TGF-beta1 gene is coincident with NGF-induced neuronal differentiation of PC12 cells. In addition, RA also causes a dose- and time-dependent increase in content of TGF-beta1 transcripts. This increase is, at least in part, secondary to transcriptional activation. Sequences responsible for the effect of RA and NGF are located in the 5'-flanking region of the TGF-beta1 gene. The TFG-beta1 gene has two promoters and in transient transfection assays RA and NGF significantly enhance the activity of constructs containing the second promoter. High-affinity TGF-beta1 receptors were undetectable in PC12 cells both before and after NGF or RA treatment. RA and NGF decrease PC12 cell proliferation and a neutralizing anti-TGF-beta1 antibody does not reverse this inhibition. In summary, an increase in expression and secretion of TGF-beta1 accompanies RA and NGF-induced PC12 cell growth arrest, but TGF-beta1 does not play an autocrine role in this inhibition.
用视黄酸（RA）孵育PC12细胞得到的条件培养基可增加正常大鼠肾（NRK）成纤维细胞和3D9上皮细胞中[3H]胸苷的掺入。该培养基还可导致NRK细胞的非贴壁依赖性生长，在表皮生长因子（EGF）存在时或通过酸化激活转化生长因子（TGF）的潜伏形式后，这种生长会得到显著增强。这些结果表明，RA可调节PC12细胞释放多种生长因子。来自对照或神经生长因子（NGF）处理的PC12细胞的条件培养基仅在酸化后才会使NRK细胞在软琼脂中生长。TGF-β1基因表达的增加与NGF诱导的PC12细胞神经元分化同时发生。此外，RA还会导致TGF-β1转录本含量呈剂量和时间依赖性增加。这种增加至少部分是转录激活的结果。负责RA和NGF作用的序列位于TGF-β1基因的5'侧翼区域。TGF-β1基因有两个启动子，在瞬时转染实验中，RA和NGF可显著增强含有第二个启动子的构建体的活性。在NGF或RA处理前后，PC12细胞中均未检测到高亲和力的TGF-β1受体。RA和NGF可降低PC12细胞的增殖，而中和性抗TGF-β1抗体并不能逆转这种抑制作用。总之，RA和NGF诱导PC12细胞生长停滞时，TGF-β1的表达和分泌会增加，但TGF-β1在这种抑制作用中不发挥自分泌作用。
