Zhang M, Zou Z, Maass N, Sager R
Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Cancer Res. 1995 Jun 15;55(12):2537-41.
Elafin is an elastase inhibitor with a unique structure, not related to the serpin family, which includes the neutrophil elastase inhibitor. The gene was identified in this laboratory by subtractive hybridization between RNAs from human mammary tumor-derived cells and cDNAs from normal human mammary epithelial cells. Elafin is consistently expressed in normal mammary epithelial cells, but is down-regulated in most breast tumor cell lines. Restriction fragment analysis detected no gross deletions or rearrangement of the gene in any of the tumor cell lines examined. The elafin gene was cloned, and both the cDNA and the promoter region were sequenced. A major positive upstream promoter element was identified by chloramphenicol acetyltransferase assay and deletion analysis, active in normal cell extracts but not in extracts of tumor cells. These results demonstrate that differential expression of elafin in normal mammary epithelial cells and breast tumor cells is regulated at the transcriptional level. Cell synchronization experiments demonstrated that elafin mRNA is down-regulated in S phase in normal cells. These results suggest that elafin may act as an inhibitor of cell cycle progression.
弹性蛋白酶抑制因子是一种具有独特结构的弹性蛋白酶抑制剂，与丝氨酸蛋白酶抑制剂家族无关，该家族包括中性粒细胞弹性蛋白酶抑制剂。该基因是由本实验室通过人乳腺肿瘤衍生细胞的RNA与正常人乳腺上皮细胞的cDNA之间的消减杂交鉴定出来的。弹性蛋白酶抑制因子在正常乳腺上皮细胞中持续表达，但在大多数乳腺肿瘤细胞系中表达下调。限制性片段分析在任何检测的肿瘤细胞系中均未检测到该基因的大片段缺失或重排。弹性蛋白酶抑制因子基因被克隆，其cDNA和启动子区域均被测序。通过氯霉素乙酰转移酶测定和缺失分析鉴定出一个主要的上游正向启动子元件，该元件在正常细胞提取物中具有活性，但在肿瘤细胞提取物中无活性。这些结果表明，弹性蛋白酶抑制因子在正常乳腺上皮细胞和乳腺肿瘤细胞中的差异表达在转录水平上受到调控。细胞同步化实验表明，弹性蛋白酶抑制因子mRNA在正常细胞的S期表达下调。这些结果提示弹性蛋白酶抑制因子可能作为细胞周期进程的抑制剂发挥作用。
