Farrell R E, Greene J J
Department of Biology, Catholic University of America, Washington, DC 20064.
J Cell Physiol. 1992 Nov;153(2):429-35. doi: 10.1002/jcp.1041530223.
The influence of cell shape on the expression of proto-oncogenes was examined in normal and malignant human cells that varied in their sensitivities to contact-inhibition of proliferation. Cells were constrained into varying degrees of roundness by plating onto culture surfaces coated with different concentrations of poly(2-hydroxyethyl methacrylate) (poly[HEMA]) and assayed for proliferation capacity and levels of c-myc, c-ras, c-fos, and c-fes mRNAs. Proliferation of contact-inhibited normal CUA-1 fibroblasts and the variant HT-IFNr cells was highly coupled to cell shape. As these cells became more rounded, a critical degree of roundness was reached at which proliferation ceased. In contrast, proliferation of non-contact-inhibited malignant HT-1080 cells was independent of cell shape. Northern analysis revealed that expression of c-myc and c-ras was highly sensitive to cell shape in the normal CUA-1 cells but not in the malignant HT-1080 or variant HT-IFNr cells. Levels of c-myc and c-ras mRNAs declined to nearly undetectable levels in CUA-1 cells at degrees of roundness that correlated with loss of proliferative ability. Expression of c-fos and c-fes oncogenes were independent of cell shape in all cells tested. Quantification of transcription rates by the nuclear run-off assay showed that shape modulation of c-myc and c-ras oncogene expression occurred at the transcriptional level. These data suggest that changes in cell shape can modulate expression of certain oncogenes and that these changes correlate with the cell's ability to proliferate. Moreover, inability to regulate c-myc and c-ras oncogene expression is associated with loss of shape-dependent growth controls and contact inhibition but that loss of this regulation alone is not sufficient to release cells from contact-inhibited controls.
在对增殖接触抑制敏感性不同的正常和恶性人类细胞中，研究了细胞形状对原癌基因表达的影响。通过将细胞接种到涂有不同浓度聚（甲基丙烯酸2-羟乙酯）（聚[HEMA]）的培养表面上，使细胞受到不同程度的圆形约束，并检测其增殖能力以及c-myc、c-ras、c-fos和c-fes mRNA的水平。接触抑制的正常CUA-1成纤维细胞和变异的HT-IFNr细胞的增殖与细胞形状高度相关。随着这些细胞变得更加圆润，达到了一个关键的圆润程度，此时增殖停止。相比之下，非接触抑制的恶性HT-1080细胞的增殖与细胞形状无关。Northern分析显示，c-myc和c-ras的表达在正常CUA-1细胞中对细胞形状高度敏感，但在恶性HT-1080或变异的HT-IFNr细胞中则不然。在与增殖能力丧失相关的圆润程度下，CUA-1细胞中c-myc和c-ras mRNA的水平下降到几乎检测不到的水平。在所有测试细胞中，c-fos和c-fes原癌基因的表达与细胞形状无关。通过核转录分析对转录速率进行定量显示，c-myc和c-ras原癌基因表达的形状调节发生在转录水平。这些数据表明，细胞形状的变化可以调节某些原癌基因的表达，并且这些变化与细胞的增殖能力相关。此外，无法调节c-myc和c-ras原癌基因的表达与形状依赖性生长控制和接触抑制的丧失有关，但仅这种调节的丧失不足以使细胞从接触抑制控制中释放出来。
