Estrogen-induced lysosomal proteases secreted by breast cancer cells: A role in carcinogenesis?

In an attempt to understand the mechanism by which estrogens stimulate cell proliferation and mammary carcinogenesis, metastatic human breast cancer cell lines (MCF7, ZR75-1) were found to secrete a 52,000 dalton (52K) protein under estrogen stimulation. Following its purification to homogeneity, the 52K protein was identified as a secreted procathepsin-D-like aspartyl protease bearing mannose-6-phosphate signals. This precursor displays an in vitro autocrine mitogenic activity on estrogen-deprived MCF7 cells and is able to degrade basement membrane and proteoglycans following its autoactivation. The total protease (52K + 48K and 34K) was detected and assayed by monoclonal antibodies and was found to be highly concentrated in proliferative and cystic mastopathies. In breast cancer, its cytosolic concentration appears to be correlated more to tumor invasiveness than to hormone responsiveness. The mRNA of the 52K protease accumulates rapidly following estradiol treatment, as was shown by Northern blot analysis with cloned cDNA. The 52K cathepsin-D-like protease is the first example of a lysosomal protease induced by estrogens in cancer cells. Results obtained using different approaches suggest that two cysteinyl cathepsins are also related to cell transformation and invasiveness. It has been proposed that cathepsin-B is involved in breast cancer and metastatic melanoma, and its regulation by estrogen has been shown in the rat uterus. Cathepsin-L corresponds to the major excreted protein (MEP) whose synthesis and secretion are markedly increased by transformation of NIH 3T3 cells with Ki ras and are regulated by several growth factors. In addition to secreted autocrine growth factors and to other proteases (plasminogen activator, collagenase), lysosomal cathepsins may therefore play an important role in the process of tumor growth and invasion as long as their precursor is secreted abundantly.     

Circumferential analysis of digitalized gamma angiocardiography by assessment of regional left ventricular contraction

After acquisition of a digital equilibrium gamma-angiocardiographie, circumferential analysis of end-diastolic and end-systolic frames gives 120 points diastolic and systolic curves. Their difference represents systolic volume and leads to regional left ventricular ejection fraction assessment at the considered radius level. The circumferential analysis evolute gives the regional left ventricular ejection fraction representative curves which allows especially differential diagnosis between left ventricular akinesia and dyskinesia.     

Binding of anti-fibronectin to early amphibian ectoderm does not result in inhibition of neural induction under in vitro conditions

Summary Antibodies directed to fibronectin (anti-FN) were injected into the blastocoel of late blastulae of Xenopus laevis. Two animal caps (ectoderm) were isolated, when control embryos reached the early gastrula stage, and were combined with untreated upper blastopore lip in the sandwich method. In two control series fibronectin or Holtfreter solution was injected into the blastocoel. The results of the experiments suggest that neural induction cannot be prevented by binding anti-FN to fibronectin, which covers the blastocoelic side of the ectoderm. The data support the view that extracellular matrix proteins are not themselves responsible for neural induction. However, in comparison with the control series a slight shift of the differentiation pattern in the spinocaudal direction could be observed in the anti-FN series. The possible role of extracellular proteins in the formation of a close juxtaposition of mesodermal and ectodermal target cells as a prerequisite for shortdistance transmission of neural inducers is discussed.     

Dibutyryl-cyclic AMP inhibits cholesterol esterification in J 774 monocyte-like cells

The effect of dibutyryl-cyclic AMP (dbcAMP) and theophylline was investigated on oleic acid incorporation into cholesteryl esters and triacylglycerols in the mouse monocyte-macrophage cell line J 774. 24h pretreatment of macrophages with dbcAMP decreased cholesteryl ester formation in a dose-dependent manner (about 4 fold reduction for dbcAMP 10(-4)M + theophylline 10(-3)M), while oleic acid incorporation into triacylglycerols was markedly (2 to 3 fold) enhanced. The catabolism of acetylated LDL was only slightly affected (about 15-20% reduction with dbcAMP 5 X 10(-4)M + theophylline 10(-3)M). Acyl Coenzyme A: cholesterol-O-acyl-transferase activity, measured in vitro on cell homogenates, was reduced in dbcAMP-treated cells, whereas diacylglycerol acyltransferase activity was increased. These results suggest that cyclic AMP can modulate cholesteryl ester and triacylglycerol formation in macrophages, and that these metabolisms are inversely regulated. Agents which increase cyclic AMP intracellular level could be of interest for reducing cholesteryl ester accumulation in macrophages.     

Microheterogeneity of the malate dehydrogenase from several sources

Different homogeneously purified cytosolic malate dehydrogenases gave, on isoelectric focusing, several active bands. The phenomenon could not be assigned to differences in their molecular weights or to alterations in the enzyme preparations during the purification procedure. Resolution of the multiple malate dehydrogenase active bands was achieved by chromatofocusing. The aged isolated subforms always yielded the original electrofocusing pattern. This fact suggests that conformational isomerism is a likely explanation for the charge heterogeneity of the enzymes studied.     

Production and characterization of four monoclonal antibodies against porcine pancreatic colipase

Four monoclonal antibodies directed against porcine colipase have been generated by hybridization of myeloma cells with spleen cells of BALB/c immunized mice. Antibodies were screened by binding to immobilized colipase in a solid-phase assay. Monoclonal antibodies were purified by affinity chromatography on colipase coupled to Sepharose. All monoclonal antibodies are of the IgG1 class with high affinity for the antigen. The dissociation constant of the complex formed in solution between porcine colipase and antibody varied from 1.1 X 10(-10) M to 1.8 X 10(-8) M. Epitope specificity was studied for each antibody and in pairs with an enzyme-linked immunosorbent assay (ELISA). Results indicate that the four monoclonal antibodies react with at least three different antigenic regions of colipase. Finally, three monoclonal antibodies were found to be potent inhibitors of colipase activity. Antiporcine monoclonal antibodies appear to be suitable probes for studying the lipid affinity site of the protein cofactor of pancreatic lipase.     

Regional assignment of the gene for diphtheria toxin sensitivity using subchromosomal fragments in microcell hybrids

Human x mouse microcell hybrids resistant to G418 were constructed between mouse hepatoma cells and human x mouse whole cell hybrids containing only intact human chromosome 5 and 22 with an integrated neo ^r-gene. Among these, microcell hybrid BG15 produced four subclones, BG15-4, BG15-6, BG15-7 and BG15-9, which contained variously sized complements of human chromosome 5. BG15-6 contained an intact human chromosome 5, BG15-7 a deleted human chromosome 5 (5pter-q22) and BG15-4 and BG15-9 a translocation between parts of human chromosome 5 (pter-qter? and pter-q23, respectively) and a mouse chromosome. Southern DNA blot analysis showed that the human dihydrofolate reductase (DHFR) gene was present in all four subclones, whereas the human homolog of the v-fms gene was present in BG15-4 and 15-6, but absent from BG15-7 and 15-9. BG15-4, 15-6 and 15-9 were sensitive to diphtheria toxin, and only BG15-7 was resistant to the toxin. We used these microcell hybrids to restrict further the regional location of the gene for diphtheria toxin sensitivity to the q23 region of human chromosome 5.     

In vitro and in vivo synthesis of dolichol and other main mevalonate products in various organs of the rat

The relative rate of biosynthesis of dolichol from [3H]mevalonate in nine rat organs was studied in slices and in the whole animal. This biosynthesis was also compared to that of cholesterol and ubiquinone. All tissues examined are able to synthesize dolichol, as well as ubiquinone and cholesterol. Comparison of the data from slices in vitro with the in vivo studies demonstrated relatively good agreement for dolichol and ubiquinone synthesis. Although dolichol of high specific radioactivity was recovered in the blood, redistribution between organs, such as occurs with cholesterol, appears to be insignificant. The highest rates of dolichol biosynthesis were found in kidney, spleen and liver. On the other hand, muscle makes the largest contribution to total body dolichol synthesis. Newly synthesized dolichol also appears in the bile, but excretion by this route is far from sufficient to account for dolichol turnover. Incorporation of mevalonate into the final products is mainly dependent on biosynthetic activity. For comparison of the biosynthetic rates in different organs, possible sources of errors (such as variations in the size of the precursor pool, limitation by the rate of precursor uptake or non-linear incorporation) were investigated the size of the mevalonate pool in various organs. Equilibration of this pool with exogenous mevalonate is a rapid and passive process. The size of the mevalonate pool does not determine the rates of cholesterol and dolichol biosynthesis, indicating the presence of regulatory steps in the terminal portion of these biosynthetic pathways.     

Factors affecting malate dehydrogenase activity in freezing-thawing processes

Malate dehydrogenases from several sources show different behaviour when frozen-thawed in 100 mM sodium phosphate buffer, pH 7.4, containing chaotropic ions. The effects produced by the addition of various metabolites, protein concentration and buffer medium used on the loss of activity induced by the freezing-thawing process are reported. The major part of the loss of activity is caused by the formation of "wrong" aggregates of high mol. wt.     

Potential secondary structure at translation-initiation sites.

Since translational start codons also occur internally, more-complex features within mRNA must determine initiation. We compare the potential secondary structure of 123 prokaryotic mRNA start regions to that of regions coding for internal methionines. The latter display an unexpectedly-uniform, almost-periodic pattern of pairing potential. In contrast, sequences 5' to start codons have little self-pairing, and do not pair extensively with the proximal coding region. Pairing potential surrounding start codons was found to be less than half of that found near internal AUGs. In groups of random sequences where the distribution of nucleotides at each position, or of trinucleotides at each in-frame codon position, matched the observed natural distribution, there was no periodicity in the pairing potential of the internal sequences. Randomized internal sequences had less pairing: the ratio of pairing intensity between internals and starts was reduced from 2.0 to 1.6 by randomization. We propose that the transition from the relatively-unstructured start domains to the highly-structured internal sequences may be an important determinant of translational start-site recognition.