bromochloroacetic-acid and afimoxifene

Fulvestrant (ICI 182, 780) is a selective estrogen receptor downregulator (SERD) and potent antiestrogen. In estrogen receptor-alpha-positive ERalpha(+) breast cancer, the drug immobilizes ERalpha in the nuclear matrix, inducing receptor polyubiquitination and subsequent degradation via the 26S proteasome. We previously reported that fulvestrant-induced ERalpha degradation depends on the interaction of ERalpha with cytokeratins 8 and 18 (CK8/CK18). Here we further investigate the role of these two cytokeratins in the antagonistic activity of the SERD. Using ER-responsive reporter assays, we demonstrate greater antiestrogenic activity of fulvestrant in CK8/CK18(+) vs. CK8/CK18(-) cancer cells and loss of CK8/CK18 expression was observed in a breast cancer cell model for acquired fulvestrant resistance. In contrast, the presence of CK8/CK18 had no effect on the antiestrogenic activity of 4-hydroxytamoxifen, which was unable to induce an interaction between these CKs and ERalpha. By utilizing the ligand activity inversion ERalpha mutant L540Q to further examine the mechanism of fulvestrant action, we demonstrate that the ERalpha mutant does not interact with CK8/CK18 in the presence of fulvestrant and L540Q is not immobilized to the nuclear matrix after antiestrogen treatment. In transcription assays, fulvestrant displayed agonist activity, stimulating L540Q-mediated gene expression. In addition, fulvestrant did not induce an ERbeta interaction with CK8/CK18 and subsequent ERbeta degradation. Collectively, these results suggest that CK8/18 play an important role in the antiestrogenic action of fulvestrant in breast cancer cells and that these two cytokeratins could serve as prognostic markers for SERD therapy response in breast cancer patients.

Topics: Breast Neoplasms; Estradiol; Estrogen Antagonists; Estrogen Receptor alpha; Estrogen Receptor beta; Estrogen Receptor Modulators; Female; Fulvestrant; Humans; Keratins; Oligonucleotides; Proteasome Endopeptidase Complex; Receptors, Estrogen; Tamoxifen

We have generated mice with a floxed fak allele under the control of keratin-14-driven Cre fused to a modified estrogen receptor (CreER(T2)). 4-Hydroxy-tamoxifen treatment induced fak deletion in the epidermis, and suppressed chemically induced skin tumor formation. Loss of fak induced once benign tumors had formed inhibited malignant progression. Although fak deletion was associated with reduced migration of keratinocytes in vitro, we found no effect on wound re-epithelialization in vivo. However, increased keratinocyte cell death was observed after fak deletion in vitro and in vivo. Our work provides the first experimental proof implicating FAK in tumorigenesis, and this is associated with enhanced apoptosis.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Apoptosis; Blotting, Western; DNA Primers; Flow Cytometry; Fluorescent Antibody Technique; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Gene Deletion; Genotype; Hydroxytestosterones; Immunohistochemistry; Integrases; Keratin-14; Keratinocytes; Keratins; Mice; Mice, Transgenic; Neoplasm Metastasis; Protein-Tyrosine Kinases; Receptors, Estrogen; Skin Neoplasms; Tamoxifen

The adjuvant endocrine therapy of breast cancer with non-steroidal antiestrogens of the triphenylethylene-type such as tamoxifen is clinically well established, and pure steroidal antiestrogens are being introduced in clinical trials to circumvent the probable occurrence of tamoxifen resistance. Nevertheless, there do still remain some unsolved questions about the exact mechanisms of these substances. We therefore investigated the different effects of 4-OH-Tamoxifen (OHT), a non-steroidal antiestrogen, versus ZM 182780, a pure steroidal antiestrogen, on the morphology and on the cytoskeleton of MCF-7 (estrogen receptor-positive) and MX-1 (estrogen receptor-negative) cells. For this purpose cells were treated for 2, 5 and 7 days with OHT, ZM182780 and different concentrations of beta-estradiol. Interestingly, in scanning electron microscopy, MCF-7 cells showed more differentiation by forming three-dimensional structures such as acini or tubule-like structures under ZM 182780 therapy than with OHT. As expected, MX-1 cells showed no effects after ZM 182780-therapy, but OHT led to a decrease in the number of these cells and produced a fibroblast-like appearance of the estrogen receptor-negative MX-1 cells. The following immunocytochemical experiments on the tubulin, vimentin, cytokeratin and actin cytoskeleton surprisingly did not show marked differences within the morphologically differentiated ZM 182780-treated population compared to the control group of MCF-7 cells. Only the OHT-treated cells of both, the ER(+) and the ER(-) cells, showed a rearrangement of actin filaments and cytokeratin which appeared even more pronounced within the ER(-) MX-1 cells. No experimental group showed morphologically detectable changes in tubulin or vimentin distribution. These data suggest a non ER-mediated OHT-effect on the cytoskeleton that also affects the ER(-) cell line MX-1.

Topics: Actins; Antineoplastic Agents; Breast Neoplasms; Cytoskeleton; Estradiol; Estrogen Antagonists; Female; Fulvestrant; Humans; Immunohistochemistry; Keratins; Microscopy, Electron, Scanning; Receptors, Estrogen; Tamoxifen; Tubulin; Tumor Cells, Cultured; Vimentin

Antagonists of steroid hormones are clinically important in the management of breast cancer. However, the duration of response is limited due to the development of hormone-independent tumors in virtually all cases. In an attempt to obtain insight into the mechanisms underlying antiestrogen resistance, the consequences of epigenetic changes in gene expression were studied in vitro. Estrogen-dependent ZR-75-1 human breast cancer cells were treated with 5-azacytidine, an inhibitor of DNA methylation, and cultured in the absence of estradiol or in the presence of antiestrogens. Estrogen-independent cell colonies developed within 3 weeks at high frequency in 5-azacytidine-treated cultures (0.7 x 10(-3), in contrast to control cultures (< or = 10(-8). The derived cells (ZR/AZA) were resistant to 4-hydroxytamoxifen and ICI 164,384, independent of the selection protocol, but had lost the ability to grow anchorage-independent. Whereas expression of estrogen receptor, progesterone receptor, and pS2 were down-regulated, expression of epidermal growth factor (EGF) receptor and HER2/neu were increased in ZR/AZA cells. In contrast to the stable altered expression patterns of estrogen receptor and EGF receptor, transient keratin 7 expression was observed. Transforming growth factor-alpha mRNA was identified in ZR-75-1 cells and ZR/AZA cells and EGF-like peptides were secreted in the culture medium. Proliferation of ZR/AZA cells could be partially inhibited with an EGF receptor-blocking antibody. Presence of both growth factor receptors and possible ligands suggests the development of an autocrine growth mechanism. Our data show that epigenetic alterations of gene expression result in rapid progression of breast cancer cells to hormone independence.

Topics: Azacitidine; Breast Neoplasms; Down-Regulation; ErbB Receptors; Estradiol; Estrogen Antagonists; Estrogens; Female; Gene Expression Regulation, Neoplastic; Humans; Keratins; Neoplasm Proteins; Neoplasms, Hormone-Dependent; Polyunsaturated Alkamides; Proteins; Receptor, ErbB-2; Receptors, Estradiol; Receptors, Progesterone; Tamoxifen; Trefoil Factor-1; Tumor Cells, Cultured; Tumor Suppressor Proteins