P53 and Egr-1 additively suppress transformed growth in HT1080 cells but Egr-1 counteracts p53-dependent apoptosis
P53 and Egr-1 additively suppress transformed growth in HT1080 cells but Egr-1 counteracts p53-dependent apoptosis
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DOI：
10.1038/sj.onc.1202696
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发表时间：
1999-06-17
期刊：
影响因子：
8
通讯作者：
Adamson, ED
中科院分区：
文献类型：
--
作者：
de Belle, I;Huang, RP;Adamson, ED
我们利用人纤维肉瘤细胞系HT1080克隆H-4来确定p53和Egr-1的转化抑制功能是否具有相同的潜在机制。该细胞系仅表达突变型p53，未检测到Egr-1，稳定表达Egr-1的H4克隆与Egr-1表达水平成正比，转化较少，通过诱导TGF β 1基因起作用。在这里，H4细胞和Egr-1表达最高的克隆仅仅转染了表达正常人p53的载体，以获得表达p53的稳定克隆。H4细胞中p53的表达抑制转化生长，降低致瘤性。p53和Egr-1共表达的作用是加性的，产生的细胞株生长速度是正常的30%，致瘤性比对照降低了7倍。这些结果表明，虽然每个因子都增加了p21（WAF1）细胞周期抑制剂的水平，但每个因子可能通过不同的途径独立作用。然而，将h4来源的细胞暴露在UV-C照射下产生了相反的效果。细胞周期分析表明，p53的存在与辐照后G1和S细胞凋亡的丧失有关。相反，Egr-1的表达增加了细胞周期的S/G2期，通过FAK升高和caspase活性降低的机制增加了细胞凋亡。凋亡仅在不表达Egr-1的细胞系中观察到，特别是那些表达wt-p53的细胞系，并且在高caspase活性之前。综上所述，Egr-1通过TGF β 1、FN、p21和FAK的协同激活来抑制转化和抵消凋亡，导致细胞附着增强，caspase活性降低。在双表达细胞系中，Egr-1的存活作用优于p53的凋亡作用。
The human fibrosarcoma cell line, HT1080, clone H-4, was used to determine if the transformation suppressive functions of p53 and Egr-1 have the same underlying mechanism. This cell Line expresses only mutant p53 and no detectable Egr-1, H4 clones stably expressing Egr-1 are less transformed in proportion to the level of Egr-1 expressed, acting through the induction of the TGF beta 1 gene. Here, H4 cells and the highest Egr-1 expressing clone mere transfected with a vector expressing normal human p53 to derive stable clones expressing p53. The expression of p53 in H4 cells inhibited transformed growth and reduced tumorigenicity. The effect of coexpression of both p53 and Egr-1 was additive, producing cell lines with 30% of normal growth rate and sevenfold reduced tumorigenicity compared with control lines. These results indicated that each factor may act independently by different pathways, although each additively increased the level of p21(WAF1) cell cycle inhibitor. However, exposure of the H4-derived cells to UV-C irradiation produced contrasting effects. Cell cycle analyses shelved that the presence of p53 was associated with loss of the G1 and S cells to apoptosis after irradiation. In contrast, the expression of Egr-1 increased entry into S/G2 phase of the cell cycle with Little apoptosis via a mechanism involving elevated FAK and low caspase activities. Apoptosis was observed only in the cell lines that expressed no Egr-1, especially those expressing wt-p53, and was preceded by high caspase activity. In summary, Egr-1 suppressed transformation and counteracted apoptosis by the coordinated activation of TGF beta 1, FN, p21 and FAK, leading to enhanced cell attachment and reduced caspase activity. In the doubly expressing cell line, the survival effect of Egr-1 was dominant over the apoptotic effect of p53.