CATHEPSIN-D GENE OF HUMAN MCF7 CELLS CONTAINS ESTROGEN-RESPONSIVE SEQUENCES IN ITS 5' PROXIMAL FLANKING REGION

Cathepsin D is a lysosomal protease produced and secreted in excess by most human breast cancer cells. In MCF7 cells, estrogens stimulate cathepsin D expression at the mRNA level via a mechanism independent of de novo protein synthesis. We have isolated the human cathepsin D gene and its 5′ flanking sequences from a MCF7 genomic library. To demonstrate its transcriptional estrogen regulation, we constructed chimeric recombinants bearing different fragments of the cathepsin D gene 5′ proximal region inserted in front of the bacterial chloramphenicol acetyl transferase reporter gene. By transient cotransfection with the estrogen receptor expression vector into MCF7 cells, we showed that a 240 bp fragment located in the 5′ proximal region of the gene was able to mediate transcriptional estrogen activation. This induction was concentration-dependent and suppressed by the antiestrogen ICI 164, 384. © 1991.