摘要:

AbstractWe describe studies on human breast cancer in which it is shown that specific growth factors (IGF‐I, TGFα, PDGF) are secreted by human breast cancer cells and likely to be involved in tumor growth and progression. These activities are regulated by estradiol in hormone‐dependent breast cancer and secreted constitutively by hormone‐independent cells. These growth factor activities can induce the growth of hormone‐dependent cells in vivo in athymic nude mice. Hormone‐dependent breast cancer cells also secrete TGFβ, a growth‐inhibitory substance, when treated with antiestrogens. TGFβ functions as a negative autocrine growth regulator and is responsible for some of the growth‐inhibitory effects

ISSN:0730-2312    

DOI:10.1002/jcb.240350102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractIn 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 man‐nose‐6‐phosphate signals. This precursor display 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 i

ISSN:0730-2312    

DOI:10.1002/jcb.240350103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractWe have examined the nature of biochemical degradation of an isolated basement membrane matrix (bovine lens capsule) using different methodologies. The first strategy was quantitation of the release of surface‐bound125I and a second the documentation by SDS‐PAGE of the appearance of putative cleavage products and the loss of high‐molecular‐weight components from the matrix. Basement membrane matrix bands resolved on SDS‐PAGE were identified by their protease sensitivities as well as by Western immunoblots using monoclonal antibodies developed for this study. Radioiodinated components were found predominantly at positions on the gel equivalent to 160–200 kd and 400 kd proteins. Since these labeled moieties were sensitive to bacterial collagenase digestion and stained with anticollagen type IV antibodies, they were determined to represent various configurations of collagen type IV. Several other lower‐molecular‐weight bands also stained with the anticollagen IV antibodies. Monoclonal antibodies reactive with laminin exhibited a complex staining pattern on the gels, which included the expected 200 and 400 kd components. We confirmed that lens capsule basement membrane contained only a single heparan sulfate glycosaminoglycan species, and tumor cell‐induced glycosaminoglycan degradation within the basement membrane matrix was detected using cellulose acetate electrophoresis.Distinctive putative cleavage products were resolved on SDS‐PAGE gels from matrices subjected to digestion by a variety of purified proteases as well as by metastatic tumor cells or their conditioned media. Tumor cells of different histio‐types produced different characteristic cleavage patterns, suggestive of the existence of several pathways of matrix degradation. Overall, primary tumor cells exhibited a greater degradative activity towards the basement membrane matrix than did long‐term tissue culture‐passaged cells. The same tumor cell line could exhibit considerably different patterns of both protein and glycosaminoglycan degradation depending on recent culture history. The relevance of these biochemical studies to the pathogenesis of malignant neoplasms is shown by: (1) the evaluation of degradative activities of B16 tumor cell populations exhibiting enhanced lung‐colonizing phenotypes, and (2) the ability of a known antimetastatic moiety with antiproteasc activity (Haementerialeech species salivary gland extract) to protect matrix components from degradation by tu

ISSN:0730-2312    

DOI:10.1002/jcb.240350104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThis brief review explores some recent observations relating to the structure of untransformed glucocorticoid and progesterone receptors and the mechanism by which the receptors are transformed to the DNA‐binding state. In their molybdate‐stabilized, untransformed state, progesterone and glucocorticoid receptors exist as a heteromeric 8‐9S complex containing one unit of steroid binding phosphoprotein and one or two units of the 90 kD heat shock protein hsp90. When the receptors are transformed, the steroid‐binding protein dissociates from hsp90. In cytosol preparations, temperature‐mediated dissociation proceeds much more rapidly in the presence of hormone. The dissociated receptor binds to DNA with high affinity, regardless of whether it is in the hormone‐bound or the hormone‐free state. These observations raise the possibility that the primary, and perhaps the only, role for the hormone is to promote dissociation of the receptor‐hsp90 complex.Molybdate, vanadate, and tungstate inhibit receptor transformation to the DNA‐binding form, an effect that appears to reflect the ability of these transition metal oxyanions to stabilize the complex between the steroid receptor and hsp90. By promoting the formation of disulfide bonds, hydrogen peroxide also stabilizes the glucocorticoid receptor‐hsp90 complex and prevents receptor transformation. A small, heat‐stable factor present in all cytosol preparations inhibits receptor transformation, and, when the factor is removed, glucocorticoid receptors are rapidly transformed. This ubiquitous factor has the physical properties of a metal anion, and it is proposed that molybdate and vanadate affect steroid receptor complexes by interacting with a metal anion‐binding site that is normally occupied by this endogenous rece

ISSN:0730-2312    

DOI:10.1002/jcb.240350105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe secondary activation of the avian vitellogenin II gene in isolated liver nuclei by cytoplasmatic liver extracts of estradiol‐treated chicks is accompanied by the binding of a protein from the extract to the structural part of the cloned gene. Both the DNA‐binding and gene‐stimulatory activities, which cochromatograph on heparin‐Sepharose, are apparently present only in the cytoplasmatic liver extracts of estradiol‐treated roosters and in the oviduct extracts of egg‐laying hens. DNA‐binding competition assays combined with exonuclease III footprinting showed that the factor binds to the imperfect dyad‐symmetry structure5‘GTCTTGTTCCAAAC3’ within the third intron of the gene. The factor is sequence specific and binds equally well to both single‐ and double‐stranded DNA with an estimated dissociation c

ISSN:0730-2312    

DOI:10.1002/jcb.240350106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240350101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY