A simple method to determine whole cell uptake of radiolabelled oestrogen and progesterone and their subcellular localization in breast cancer cell lines in monolayer culture

Inhibition of fibroblast proliferation in a culture of human endometrial stromal cells using a medium containing D-valine

A nutrient medium in which D-valine was substituted for L-valine inhibited fibroblast proliferation in a culture of human endometrial stromal cells. Fibroblasts were not killed by D-valine and were able to grow again when D-valine was replaced by L-valine. The stromal cells proliferate in the D-valine medium only when seeded at high density. They were distinguished from fibroblasts by their morphology in light microscopy, their surface characteristics at scanning electron microscopy and their lower staining with fibronectin antibodies.

The effects of Mg2+ ions or EDTA on nuclear integrity and apparent subcellular distribution of unoccupied oestrogen receptors in breast cancer cells

Homogenisation and fractionation of cells in the presence of Mg2+ or EDTA resulted in unoccupied oestrogen receptor being recovered in the particulate fraction. Nuclei were partially purified by pelleting at 100,000 g through 41% and 44% (w/w) sucrose (in buffer containing Mg2+ or EDTA), plasma membranes being collected from the top of the 41% barrier. In Mg2+-prepared fractions, both 5'-nucleotidase and unoccupied receptor were distributed between plasma membrane, partially-pure nuclei and mitochondrial/microsomal pellets. Lactate dehydrogenase was not a significant contaminant of particulate fractions. In EDTA fractions, the majority of binding activity was in the partially-pure nuclei (which were extensively disrupted) and mitochondrial/microsomal pellets. Little or no binding was found in the EDTA-prepared plasma membranes which were amorphous in appearance. Mg2+-prepared nuclei, freed of membranous contamination by pelleting through 1.8 M sucrose, were intact by electron microscopy but had no 5'-nucleotidase or unoccupied receptor. These data suggest that recovery of receptor in partially-pure nuclei during fractionation is not caused by trapping of cytosolic protein but rather by redistributed nuclear receptor having become bound to adhering plasma membrane fragments during homogenisation. Implications for the study of cell-free systems are discussed.

Effects of tumor promoters on growth and on cellular redistribution of phospholipid/Ca2+-dependent protein kinase in human breast cancer cells

Active, structurally unrelated tumor promoters (12-0-tetradecanoyl-phorbol-13-acetate (TPA), teleocidin and aplysiatoxin) inhibit growth of mammary carcinoma cells (MCF7- greater than BT-20 greater than MDA-MB-231 greater than = ZR-75-1 greater than HBL-100). This efficiency in inhibiting cell growth correlates with the tumor-promoting activity of a series of phorbol ester derivatives. The phospholipid/calcium-dependent protein kinase (PKC), a target for phorbol ester action, was measured by polyacrylamide gel electrophoresis. The levels of PKC were higher (p less than 0.001) in estrogen-receptor-negative than in estrogen-receptor-positive cells. Treatment of cells with active tumor promoters results in time- and dose-dependent translocation of cytosolic PKC to membrane fractions. Less potent phorbol esters induce only partial translocation of PKC (i.e., decrease of cytosolic without increase in membrane-bound PKC), whereas inactive esters have no effect. No correlation was found between PKC concentration or the amount of PKC translocated to membranes and the sensitivity of the respective cells to TPA. It is concluded that tumor-promoter-mediated growth inhibition of breast cancer cell lines is due to mechanism(s) occurring after the translocation of PKC.

Correlation between hormone dependency and the regulation of epidermal growth factor receptor by tumor promoters in human mammary carcinoma cells

The effects of the tumor promoter phorbol 12-tetradecanoate 13-acetate (TPA) on the epidermal growth factor (EGF) receptor levels were investigated in hormone-dependent (MCF-7, T-47-D, and ZR-75-1) and hormone-independent (MDA-MB-231, HBL-100, and BT-20) human mammary carcinoma cell lines. In the absence of TPA, hormone-independent cell lines contained high concentrations of low-affinity EGF receptors (apparent Kd = 8 X 10(-10) M), whereas hormone-dependent cell lines exhibited low concentrations of high-affinity receptors (apparent Kd = 1 X 10(-10) M). TPA causes a change of the receptor from a high- to the low-affinity state in hormone-dependent cell lines (MCF-7, T-47-D, and ZR-75-1), as well as in the hormone-independent HBL-100, whereas the affinity remained unchanged in MDA-MB-231 and BT-20 cells. In addition, progesterone receptor levels are decreased after TPA treatment in the hormone-dependent cell lines MCF-7, T-47-D, and ZR-75-1, whereas the estrogen receptor levels remained unchanged. Tumor promoters such as TPA or teleocidin inhibited the proliferation of these cell lines at concentrations above 10 microM with the exception of the T-47-D cells. The most sensitive cell line towards growth inhibition by tumor promoter was the hormone-dependent MCF-7 cell line. Evaluation of different TPA analogs indicated a positive correlation between the growth-inhibitory effects and their ability to stimulate the subcellular redistribution of protein kinase C activity in MCF-7 cells. These data suggest a protein kinase C-mediated down-regulation of the progesterone receptor concentration and of the EGF receptor affinity, which is supposed to mediate the mitogenic response. Furthermore, these results support the hypothesis that the tumor-derived growth factors induced by estradiol act via the EGF receptor in hormone-dependent mammary carcinoma cells.

The effects of retinoid treatment and antiestrogens on the growth of T47D human breast cancer cells

The ability of all-trans-retinoic acid, 13-cis-retinoic acid, the free acid of etretinate (RO 10-1670), the 'arotinoid' RO 13-6298 and its free acid RO 13-7410 to affect the growth of T47D human breast cancer cells in vitro was investigated. The growth of T47D cells was inhibited by all of the retinoids tested, with the arotinoids being up to 100 times more effective than all-trans-retinoic acid. The presence of cellular retinoic acid binding protein (cRABP) was indicated by the cellular uptake of [3H]all-trans-retinoic acid. Maximum binding was 460 fmol/micrograms DNA. All of the retinoids with a polar terminal free carboxyl group readily competed for the binding sites, but none of the retinoids competed for the estrogen or progesterone receptor. Co-treatment of the T47D cells with 0.1 microM all-trans-retinoic acid and either tamoxifen (1 microM) or hydroxytamoxifen (10 nM or 0.1 microM) produced an additive effect on growth inhibition. No such additive effect was observed when T47D cells were co-treated with arotinoids and antiestrogens. The results showed that the T47D cells can serve as a useful model in vitro to test the effects of the synthetic retinoids and antiestrogens on steroid receptor-positive human breast cancer.

Assay for estrogen and progesterone receptors of breast cancer cell lines in monolayer culture

A whole-cell assay for measuring estrogen (ER) and progesterone (PgR) receptors in monolayer culture of human breast cancer cell lines is described. It is based on the measurement of incorporated tritiated ligands during 50 min of incubation (i.e. [3H]estradiol for ER, [3H]ORG-2058 for PgR). The assay fulfills all criteria of specificity as shown by competitive studies and measurements of the dissociation constants of the binding reactions. Moreover, a subcellular fractionation of MCF-7 labeled cells revealed that the majority of incorporated steroids was associated with the nuclear fraction. This finding is consistent with the concept of nuclear location of steroid-receptor complexes. Cultures in the presence of 10(-8) M estradiol indicated that the methodology is adequate for detecting the well-known estrogenic induction of PgR synthesis. The assay proved suitable for the quantitative assessment of the receptor content of various neoplastic (MCF-7; ZR-75-1, Cama-1, Evsa-T) and non-neoplastic (HBL-100) cell lines. The methodology has the other advantages of being simple and rapid, of requiring small amounts of cells and of allowing histological examination of the latter before, during and after biochemical analysis.

Flow cytometric analysis of fluorescein-conjugated estradiol (E-BSA-FITC) binding in breast cancer suspensions

With greater utilization of histochemical methods for detecting estrogen binding (ER) in tumor cells, there is an increasing need to quantitate objectively these fluorescently stained cells. This study utilizes flow cytometry (FCM) to examine the binding specificity and kinetics of 17 beta-estradiol-6-CMO-BSA-FITC(E-BSA-FITC) in two human mammary carcinoma cell lines, MCF-7 and 47-DN. Cells are rendered permeable to this ligand by freeze-thawing, a process analogous to the routine staining of frozen tumor sections with E-BSA-FITC for the clinical detection of ER. FCM quantification of E-BSA-FITC binding intensity demonstrates a saturable dose-response that is specifically reduced in the presence of diethylstilbestrol (DES) in doses known to saturate Type I ER. Scatchard analysis suggests that E-BSA-FITC binding occurs with receptors of varying affinities (Kd). Lineweaver-Burk plots show that the DES inhibition is competitive for a high-affinity receptor binding to E-BSA-FITC with a Kd of approximately 50 nM. This report also compares both FCM and biochemical methods of quantitating ER under two conditions of tumor cell growth potentially encountered in clinical specimens: quiescent versus actively proliferating cells, and cells pretreated with the antiestrogen tamoxifen. By FCM analysis, the cells with greater proliferating activity contain tenfold more specifically bound E-BSA-FITC, and tamoxifen pretreatment reduces this specific binding by 50%. These FCM measurements correlate well with biochemical results and suggest that this new methodology may supplement the detection of E-BSA-FITC binding by fluorescence microscopy.