Estrogen receptor-Sp1 complexes mediate estrogen-induced cathepsin D gene expression in MCF-7 human breast cancer cells

Cathepsin D is an estrogen (17 beta-estradiol, E2)-inducible lysosomal protease. A putative estrogen receptor (ER)-Sp1-like sequence (GGGCGG(n)23ACGGG) has been identified in the non-coding strand of the cathepsin D promoter (-199 to -165), and electromobility shift assays of nuclear extracts from MCF-7 and HeLa cells confirm that both the ER and Sp1 protein bind to 32P-labeled ER/Sp1 oligo. For example, nuclear extracts from MCF-7 cells bind to the 32P-labeled ER/Sp1 oligo; however, ER/Sp1 binding can be decreased by selective competition with excess unlabeled estrogen responsive element and Sp1 oligos, immunodepletion with ER or Sp1 antibodies, and by treating cells with ICI 164,384, an antiestrogen which inhibits formation of ER homodimer. Moreover, E2-induced chloramphenicol acetyltransferase (CAT) activity in MCF-7 cells cotransfected with a human estrogen receptor expression plasmid and a plasmid containing an ER/Sp1 sequence cloned upstream to a thymidine kinase promoter and a CAT reporter. In cotreatment studies, ICI 164,384 inhibited E2-induced CAT activity. In contrast, E2 did not induce CAT activity in MCF-7 cells transfected with plasmids containing mutations in the ER or Sp1 segments of the ER/Sp1 oligo, thus confirming that both cognate binding sites are required for estrogen responsiveness

Polynuclear aromatic hydrocarbon carcinogens as antiestrogens in MCF-7 human breast cancer cells: role of the Ah receptor

Treatment of MCF-7 cells with 1.0 μM 3-methylcholanthrene (MC) caused a decrease in cell proliferation and [3H]thymidine uptake whereas no effects were observed at a lower (0.1 μM) concentration. Co-treatment of the cells with 1 nM 17β-estradiol plus 0.1 or 1.0 μ MC resulted in a significant inhibition of 17β-estradiol-induced growth and [3H]thymidine uptake. MC also inhibited the 17β-estradiol-induced secretion of the 52 kDa protein (procathepsin D) in MCF-7 cells and caused a concentration-dependent decrease in the nuclear estrogen receptor (ER) as determined by either velocity sedimentation analysis or immunoquantitation with human ER antibodies. The effects of several different polynuclear aromatic hydrocarbon (PAH) congeners on the nuclear ER in MCF-7 cells were also determined. Only those congeners which bound to the aryl hydrocarbon (Ah) receptor, namely benzo[a]pyrene, benz[a]anthracene, 7,12-dimethylbenz[a]anthracene and MC, caused a decrease in nuclear ER levels. In contrast, benzo[ghi]perylene, a congener which did not bind to the Ah receptor did not affect nuclear ER levels in MCF-7 cells. Moreover, with some congeners the decrease in nuclear ER levels could be observed without any significant induction of ethoxyresorufin O-deethylase activity, a P4501A1-dependent monooxygenase. These data suggest that the Ah receptor liganded with MC and related PAHs induced a broad spectrum of antiestrogenic responses in MCF-7 cells and complements the results of previous studies which report the antiestrogenic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and other halogenated aromatics which are also Ah receptor agonists

Quantitative Models and Implicit Complexity

We give new proofs of soundness (all representable functions on base types lies in certain complexity classes) for Elementary Affine Logic, LFPL (a language for polytime computation close to realistic functional programming introduced by one of us), Light Affine Logic and Soft Affine Logic. The proofs are based on a common semantical framework which is merely instantiated in four different ways. The framework consists of an innovative modification of realizability which allows us to use resource-bounded computations as realisers as opposed to including all Turing computable functions as is usually the case in realizability constructions. For example, all realisers in the model for LFPL are polynomially bounded computations whence soundness holds by construction of the model. The work then lies in being able to interpret all the required constructs in the model. While being the first entirely semantical proof of polytime soundness for light logi cs, our proof also provides a notable simplification of the original already semantical proof of polytime soundness for LFPL. A new result made possible by the semantic framework is the addition of polymorphism and a modality to LFPL thus allowing for an internal definition of inductive datatypes.Comment: 29 page