High passage T47D human breast cancer cells: altered endocrine and 2,3,7,8-tetrachlorodibenzo-p-dioxin responsiveness

Key parameter optimization using multivariable linear model for the evaluation of the in vitro estrogenic activity assay in T47D cell lines (CXCL-test)

In comparison to analytical tools, bioassays provide higher sensitivity and more complex evaluation of environmental samples and are indispensable tools for monitoring increasing in anthropogenic pollution. Nevertheless, the disadvantage in cellular assays stems from the material variability used within the assays, and an interlaboratory adaptation does not usually lead to satisfactory test sensitivities. The aim of this study was to evaluate the influence of material variability on CXCL12 secretion by T47D cells, the outcome of an estrogenic activity assay, the CXCL-test. For this purpose, the cell line sources, sera suppliers, experimental and seeding media, and the amount of cell/well were tested. The multivariable linear model (MLM), employed as an innovative approach in this field for parameter evaluation, identified that all the tested parameters had significant effects. Knowledge of the contributions of each parameter has permitted step-by-step optimization. The most beneficial approach was seeding 20,000 cells/well directly in treatment medium and using DMEM for the treatment. Great differences in both basal and maximal cytokine secretions among the three tested cell lines and different impacts of each serum were also observed. Altogether, both these biologically based and highly variable inputs were additionally assessed by MLM and a subsequent two-step evaluation, which revealed a lower variability and satisfactory reproducibility of the test. This analysis showed that not only parameter and procedure optimization but also the evaluation methodology must be considered from the perspective of interlaboratory method adaptation. This overall methodology could be applied to all bioanalytical methods for fast multiparameter and accurate analysis.

Progesterone reverses the mesenchymal phenotypes of basal phenotype breast cancer cells via a membrane progesterone receptor mediated pathway

Introduction

Basal phenotype breast cancers (BPBC) are often associated with apparent epithelial to mesenchymal transition (EMT). The role of progesterone (P4) in regulating EMT of BPBC has not been reported.

Methods

The EMT relevant biology was investigated in vitro using human BPBC cell models (MDA-MB468 and MDA-MB231) with P4, PR agonist (RU486), and PR antagonist (R5020) treatments. The essential role of membrane progesterone receptor α (mPRα) in the P4-regulated EMT was demonstrated by knocking down the endogenous gene and/or stably transfecting exogenous mPRα gene in the BPBC cell models.

Results

The expression of snail and down-stream EMT proteins such as occludin, fibronectin, and E-cadherin was significantly regulated by P4 incubation, which was accompanied by cell morphological reversion from mesenchymal to epithelial phenotypes. In searching for the cell mediator of P4' action in the MDA-MB468 (MB468) cells, it was found that mPRα but not the nuclear PR has an essential role in the P4 mediated EMT inhibition. Knocking down the expression of mPRα with specific siRNA blocked the P4's effects on expression of the EMT proteins. In another BPBC cell line - MDA-MB231 (MB231), which is mPRα negative by Western blotting, P4 treatment did not alter cell proliferation and EMT protein expressions. Introduction of the exogenous mPRα cDNA into these cells caused cell proliferation, but not EMT, to become responsive to P4 treatment. In further studies, it was found that activation of the PI3K/Akt pathway is necessary for the P4-induced EMT reversion. To define the potential inter-mediate steps between mPRα and PI3K, we demonstrated that mPRα, caveolin-1 (Cav-1), and epidermal growth factor receptor (EGFR) are colocalized in the membrane of caveolar vesicle and the P4-repressed EMT in MB468 cells can be blocked by EGFR inhibitor (AG1478) and PI3K inhibitor (wortmannin).

Conclusions

Our data suggest that the signaling cascade of P4 induced mesenchymal repression is mediated through mPRα and other caveolae bound signaling molecules namely Cav-1, EGFR, and PI3K. This novel finding may have great impact on fully understanding the pathogenesis of BPBC and provide an essential clue for developing a targeted therapeutic strategy for treatment of BPBC.

Irreversible loss of the oestrogen receptor in T47D breast cancer cells following prolonged oestrogen deprivation

The development of antioestrogen resistance is a major clinical obstacle encountered in the treatment of breast cancer. By long-term growth in oestrogen-free medium, we have derived an oestrogen-independent, anti-oestrogen resistant cell line from the oestrogen receptor (ER)-positive, oestrogen-dependent T47D human breast cancer cell line. This cell line grows maximally in oestrogen-free medium and is resistant to all tested antioestrogens. This cell line does not express any measurable amounts of ER mRNA or protein and, in short-term studies, these cells show no response to either oestrogens or antioestrogens. However, return of these cells to oestrogen-containing medium for more than 8 weeks resulted in the re-expression of ER mRNA and protein. Subsequent limiting dilution subcloning of the T47D:C4 line revealed two phenotypically distinct clones, one which did not express measurable ER after long-term growth in oestrogen-containing medium and one which expressed ER mRNA and protein after a number of weeks in oestrogen-containing medium. In the absence of oestrogen, both types of cells are ER-negative as determined by Northern and Western blotting and lack of any oestrogen-dependent responses. The clone which re-expresses the ER (T47D:C4:5W) now responds to E2 with a 50% increase in growth and a 30-fold induction of an ER-responsive luciferase reporter construct. Long-term growth of the stably ER-negative clone (T47D:C4:2W) causes no measurable oestrogen-mediated responses, as assessed by ER expression, growth stimulation or luciferase induction. Interestingly, ER mRNA can be detected in both cell types by using reverse transcriptase-polymerase chain reaction (RT-PCR). This suggests that the ER mRNA present in the T47D:C4:2W clone is either inefficiently translated or is present at such a low level as to be functionally irrelevant. These novel clonal cell lines will prove to be invaluable in the study of the regulation of ER expression and regulatory pathways leading to oestrogen-independent growth.