Regulation of signal transduction for growth factors in mammary epithelial cells.

乳腺上皮细胞的增殖受胰岛素、IGF-I和EGF等生长因子的调节，这些生长因子的信号转导在许多细胞中被研究。然而，该途径并没有完全澄清。为了研究这些生长因子对乳腺上皮细胞生长的调控及其信号转导途径，我们分析了乳腺上皮细胞中细胞周期蛋白A、B_1、D_1、D_2、D_3和E以及细胞周期蛋白依赖性激酶的变化。免疫<odc2><odk2>沉淀后用免疫印迹法检测p34^和p33^。用逆转录-聚合酶链反应（RT-PCR）分析了细胞周期蛋白A、D_2和E的表达。它们在妊娠早期乳腺上皮细胞增殖活跃时明显增加，表明生长因子通过这些细胞周期蛋白调节生长。而细胞周期素B_1、D_1和D_3在妊娠期和哺乳期变化不大。我们进一步观察到一个特殊的事实，即编码p21和p27的信使RNA，肿瘤抑制基因相关的细胞周期蛋白抑制剂，在妊娠早期增加。这些抑制剂可能参与细胞周期的某个阶段，正常控制上皮细胞分裂，以避免肿瘤transformation.To澄清细胞周期中的阶段特异性表达的细胞周期蛋白，从乳腺上皮细胞系建立同步化血清剥夺。免疫印迹法检测细胞周期蛋白D_1表达的变化。Cyclin D_1在G_1/S转换期高于前期和后期。

Porliferation of the mammary epithelial cell is regulated by growth factors including insulin, IGF-I and EGF.Signal transduction for these growth factors is investigated in many cells. However, the pathway is not completely clarified. To investigate the regulation of growth in the mammary epithelial cell by these growth factors and also investigate their signal transduction pathways, changes in cyclins A,B_1, D_1, D_2, D_3 and E,and cyclin-dependent kinases were analyzed in the mammary epithelial cell. p34^<odc2> and p33^<odk2> were detected by immunoblotting after immunoprecipitation. These proteins were found more in the cell lysate from early pregnant mice of which mammary cells actively grow than in that from lactating cells.The expression of cyclins A,D_2 and E were analyzed by the reverse transcription-polymerase chain reaction. They have shown clear increase during early pregnancy where the proliferation of mammary epithelium is active, suggesting that the regulation of growth by growth factors are through these cyclins. On the other hand, cyclins B_1, D_1 and D_3 did not change very much through pregnancy and lactation. We have further observed a peculiar fact that messenger RNA encoding p21 and p27, tumor suppressor gene-related inhibitors of cyclin, increased during early pregnancy. It is probable that these inhibitors take part in some stage of cell cycle for normally controlled cell division of the epithelium to avoid tumor transformation.To clarify the stage-specific expression of cyclins in the cell cycle, a cell line established from the mammary epithelium was synchronized by serum deprivation. Changes in the expression of cyclin D_1 was examined by the immunoblotting method. Cyclin D_1 level was higher at G_1/S transition than in the prior and later periods.