Western immunoblotting and enzymatic activity analysis of cathepsin D in human breast cancer cell lines of different invasive potential. Regulation by 17beta-estradiol, tamoxifen and ICI 182,780.

We used enzymatic activity and immunochemical quantifications to analyse the expression and secretion of cathepsin D by human breast cancer cell lines of different invasive potentials (MCF-7/6, MCF-7/AZ, MDA-MB-231). This study does not directly prove that cathepsin D or procathepsin D is involved in human breast cancer cell invasion and metastasis but it shows that the proportion of procathepsin D (activity and antigen) secreted by the human breast cancer cell lines tested correlates with their invasive potential. In the estrogen receptor-positive MCF-7 subclones, this proportion is increased by estradiol only in the invasive MCF-7/6 variant.

Intracellular levels and secretion of insulin-like-growth-factor-binding proteins in MCF-7/6, MCF-7/AZ and MDA-MB-231 breast cancer cells. Differential modulation by estrogens in serum-free medium.

The synthesis and secretion of insulin-like growth factor binding proteins (IGFBPs) were studied in MDA-MB-231 (estrogen-receptor-negative), MCF-7/6 (estrogen-receptor-positive, invasive) and in MCF-7/AZ (estrogen-receptor-positive, non-invasive) human breast carcinoma cell lines. Cells were grown or maintained in a chemically defined medium. Under these conditions, we found different patterns of IGFBPs in the three cell types.

Estrogen and insulin modulation of intracellular insulin-like growth factor binding proteins in human breast cancer cells: possible involvement in lysosomal hydrolases oversecretion.

Differences in insulin-like growth factor binding proteins (IGFBPs) expressed within estrogen receptor positive (ER+, MCF-7/6) and negative (ER-, MDA-MB-231) human breast cancer cells cultured in chemically defined medium were observed. In the absence of insulin, 17 beta-estradiol affects this expression in ER+ cells by significantly reducing 34 and 28 kDa species. In ER+ cells, insulin appears to minimize the estrogen induced reduction of these 34 and 28 kDa IGFBPs and stimulates a 24 kDa type.

Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria.

Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved the migration of the osteoblasts on glass fragments before trypsinization.

Tumorigenic Xenopus cells express several maternal and early embryonic mRNAs.

Recombinant cDNA libraries were constructed from poly(A)+ RNA isolated from different stages of oogenesis and embryogenesis from the clawed toad Xenopus laevis. Hybridization analyses were used to describe the accumulation of specific RNAs represented by these cDNA clones in oocytes, embryos, adult liver, a cell line derived from Xenopus borealis embryos (Xb693), and a tumorigenic substrain of that cell line (Xb693T). It was found that from 550 cDNA clones analysed, six sequences accumulate to higher titers in poly(A)+ RNA isolated from the tumorigenic cell line compared with the non-tumorigenic cell line.