The role of Ets family member of Fli-1 in malignancy of mammary tumors and pancreatictumors

在11例乳腺肿瘤和4例胰腺癌中，多种ETS家族基因的表达水平与uPA(尿激酶型纤溶酶原激活物)、MMP(基质金属蛋白酶)等侵袭相关基因的表达呈正相关。Ets-1的表达水平与肿瘤的恶性程度密切相关，已有大量报道。然而，Fli-1在实体瘤中的作用尚未很好地阐明。因此，我们将Fli-1的表达载体导入人低恶性乳腺癌细胞MCF-7中，获得了多个高水平表达Fli-1蛋白的克隆。在含10%胎牛血清和1%胎牛血清的培养条件下，Fli-1基因转染体和模型转染体的生长无明显差异。然而，Fli-1转染组比模型转染组更能抵抗血清耗竭所致的细胞凋亡。血清d-…诱导Fli-1和bcl2的表达Fli-1转染组的细胞凋亡率和表达水平均高于模型转染组。加入JNK(Jun末端激酶)抑制剂可抑制这种诱导，提示JNK参与了血清耗竭诱导Fli-1和bcl2的表达。在紫外光照射下，Fli-1基因转染体的细胞凋亡率也较高。由于bcl-2基因在其启动子区域具有Ets结合位点，因此实体瘤中Fli-1表达增强可能在抑制细胞凋亡中起着关键作用。通过使用siRNA，我们随后研究了其他ETS家族基因的功能作用，这些基因在人类乳腺肿瘤中的表达经常增强。将针对Ets-1、Ets-2、Er81或E1a-F基因的siRNA导入恶性程度较高的人乳腺癌细胞MDA-MB-231。针对Ets-1的siRNA抑制了Ets-1的表达，下调了MMP1、MMP3和MMP9基因的表达。针对Ets-2的siRNA下调了MMP1、MMP3和MMP7基因的表达。尽管siRNA的引入抑制了BAD基因的表达，但针对Er81的siRNA对基质金属蛋白酶基因的表达没有影响。这些结果表明，在同一肿瘤中高表达的ETS家族基因通过影响单个或共同的靶基因的表达而参与恶性肿瘤的发生。较少

Positive correlation was found between the expression levels of several Ets family genes and invasion-related genes such as the uPA(urokinase-type plasminogen activator) and MMP(matrix metalloproteinase) genes in human malignant tumor cell lines including 11 mammary tumors and 4 pancreatic tumors. There are many reports concerning about tight correlation between the expression level of Ets-1 and tumor malignancy. However, the role of Fli-1 in solid tumors has not been elucidated well. Therefore, we introduced an expression vector of Fli-1 into MCF-7 human low-malignant mammary tumor cells to get several clones expressing high levels of Fli-1 protein. There were not so significant differences between Fli-1-transfectants and mock-transfectants in growth under culture conditions with 10% and 1% fetal bovine serum. However, Fli-1-transfectants were more resistant to apoptotic cell death induced by serum depletion than mock-transfectants. Expression of Fli-1 and bcl-2 was induced by serum d … More epletion and the expression levels were higher in Fli-1-transfectants than mock-transfectants. The induction was suppressed by adding a JNK (Jun terminal kinase) inhibitor, suggesting that JNK is in volved in induction of Fli-1 and bcl-2 expression by serum depletion. Fli-1-transfectants also showed the higher rates of inhibition of apoptosis by UV-irradiation. Since the bcl-2 gene has Ets-binding sites on its promoter region, it is likely that enhanced Fli-1 expression in solid tumors plays a critical role in inhibition of apoptosis. By using siRNA, we then examined the functional roles of other Ets family genes whose expression is often enhanced in human mammary tumors. Highly malignant MDA-MB-231 human mammary tumor cells were transfected with siRNA against the Ets-1,Ets-2,ER81 or E1A-F gene. Expression of the MMP-1,MMP-3 and MMP-9 genes was down-regulated accompanied by suppression of Ets-1 expression with siRNA against Ets-1 in the cells. Expression of the MMP-1,MMP-3 and MMP-7 genes was down-regulated with siRNA against Ets-2. No changes were observed in expression of the MMP genes with siRNA agaist ER81,although introduction of the siRNA resulted in suppression of expression of the bad gene. These results suggest that the Ets family genes highly expressed in the same tumors participate in malignancy by affecting expression of individual or common target genes. Less