PubMed Health⌕ Search

Biomedical subjects

G Markus

Publications and source records attributed to G Markus.

At least 19 recordsLinked to original sources
PubMed1991

Characterization of a family of high-molecular-weight plasminogen activators secreted by a lung tumor cell line.

In an earlier publication (Harvey, et al. (1982) J. Biol. Chem., 257, 5645-5651) the discovery of a family of unusually large molecules with plasminogen activator activity in the conditioned medium of a human lung cancer cell line was reported. These molecules are related to urokinase (uPA) by functional and immunological criteria. We have now purified two representatives of this glycoprotein family of Mr 900,000 (PA900) and Mr 660,000 (PA660). While these could be fractionated into subspecies exhibiting size and charge differences, reduction yielded in all cases two predominant chains of 70 and 40 kDa, respectively. Since the amino acid composition of the subfractions was identical, we conclude that the heterogeneity is due to demonstrated differences in glycosylation. The amino acid composition of the unreduced species and of the major reduced chains differed from that of 55 kDa uPA. These enzymes are active toward the substrate, plasminogen, as well as toward the uPA-specific synthetic substrate, Spectrozyme UK, and these activities are inhibitable by diisopropylphosphorofluoridate (DFP). Treatment of PA660 with [3H]DFP resulted in the incorporation of 1.4 mol of DFP into 1 mol of enzyme, suggesting the presence of a single active site. The label was quantitatively recovered in a 21 kDa fragment in a reduction experiment. This fragment also demonstrated immunological reactivity with antiurokinase. It is postulated that PA660 is composed of five or six pairs of the 70 and 40 kDa chains, and of a single uPA-like entity. All of these chains are linked by disfulfide bonds. Whether larger portions of uPA are also present in this molecule, is not yet clear. By electron microscopy, PA900 shows a filamentous structure, while PA660 is predominantly globular. The occurrence of large uPA-like activators in extracts of human colon carcinomas that crossreact with monospecific antibody against uPA, is discussed.

Amino Acids↗
PubMed1991

Epidermal growth factor and 12-tetradecanoyl phorbol 13-acetate induction of urokinase in A431 cells.

The signal transduction pathways of urokinase (u-PA) in A431 cells, a human epidermoid carcinoma cell line, were studied using the inducers EGF and TPA. Based on the following observations, we conclude that the two pathways are different: (1) The effects are additive; (2) EGF induction of u-PA was not compromised either by down-regulation of PKC or selective inhibition of the same by H7; (3) 8-Br-cAMP has no effect by itself; however, it inhibits the EGF effect and doubles the TPA induction of u-PA; (4) after EGF-induced tyrosine phosphorylations are completed, addition of TPA can still induce u-PA, an effect that can be blocked by the addition of the tyrosine phosphorylation inhibitor, genistein, indicating that the two agents induce different tyrosine phosphorylation; (5) in 2-dimensional electrophoresis of 32P-labeled cell lysates, inducer-specific differences in the intensity of spots can be observed. Some of the spots weakened by genistein (tyrosine phosphorylations) are different, depending on the inducer used.

Chromogenic Compounds↗
PubMed1990

Urokinase secretion from human colon carcinomas induced by endogenous diglycerides.

Colon tumor cells are more responsive to certain growth modulators in their local environment in vivo than are normal colonocytes. Examples of this class of compounds are the fecal diglycerides (DGs)(E. Friedman et al., Cancer Res., 49: 544-548, 1989), which may act as endogenous tumor promoters. At the concentration found in vivo, fecal DGs composed of oleic, myristic, and palmitic fatty acids induced mitogenesis of all classes of benign tumor cells and of half of the resected carcinomas tested in primary culture, but induced no detectable mitogenesis of normal colonocytes. Colon tumor cells also exhibit selective responses to these endogenous modulators as measured by another biological parameter, secretion of urokinase from carcinomas than from normal colonocytes. Fecal DGs also induced a 13-fold increase in urokinase mRNA synthesis in colon carcinoma cells and induced secretion of active urokinase from each of five resected carcinomas. Colon carcinomas, at both the primary site and metastatic to the liver, secreted the Mr 55,000 form of urokinase constitutively and secreted the same form upon treatment with fecal DGs. An increase in the steady-state level of urokinase secretion by saturated-chain DGs exhibited a strong dependency on the chain length of the fatty acid residues, those of 14 and 16 carbons having the greatest activity. Thus, fecal DGs composed of oleic, myristic, and palmitic acid residues induce two biological activities selectively in colon tumor cells, each of which would enhance tumor development. Selective mitogenesis would increase adenoma and carcinoma cell number relative to normal colonocyte number, and induction of the proteolytic enzyme urokinase would aid local invasion of the carcinoma within the bowel wall.

Blotting, Western↗
PubMed1989

Directed migration of murine and human tumor cells to collagenases and other proteases.

Tumor cell motility and the passage of tumor cells through various tissue matrices, including basement membrane, are important components of the metastatic process. Proteolytic enzymes, including a type IV collagen-specific collagenase, have been demonstrated to play a significant role in extracellular matrix and basement membrane degradation. In addition, exogenous collagenase has been shown to enhance the motility of some tumor cells independent of its effect on collagen-containing material. Previous studies have also indicated that collagen fragments are chemotactic for many tumor cells. We therefore studied the effect of type I and type IV collagen-specific collagenases, other enzymes involved in collagenase activation and connective tissue degradation, and subsequent collagen degradation products on the directed migration of tumor cells. We report that type I and type IV collagen-specific mammalian collagenases were potent chemoattractants as were native type I and type IV collagens and collagen fragments. Collagenase inhibitor SC44483 inhibited the type IV collagenase-stimulated migration. Collagenase pretreatment of the tumor cells potentiated the migratory response of the tumor cells to collagen and collagen fragments. The plasminogen activator, urokinase, as well as plasminogen itself also enhanced the directed migration of tumor cells in concentrations that suggest involvement of the appropriate cell surface receptor. The chemotactic response of tumor cells to the proteases studied extends the prior report of a role for collagenases and other matrix-active enzymes in tumor cell behavior in addition to matrix degradation.

Animals↗
PubMed1989

A model for hydropathy-based peptide interactions.

Two peptides are specified when the noncoding DNA strand is read in the 5' to 3', or the 3' to 5' direction, and both peptides form strong complexes with the natural peptide, as found by J. E. Blalock and K. L. Bost with ACTH [1986) Biochem. J. 234, 679-683). We report here that strong hydropathic complementarity (pairing of hydrophobic with hydrophilic residues), the assumed basis of these interactions, is obtained only if the peptide resulting from reading in the 3' to 5' direction is aligned parallel to the natural peptide, or if the peptide derived by opposite reading of the DNA is aligned antiparallel to it. Complementary is abolished in other alignments, including all staggered ones. In the appropriate alignments of the constructs the amino acid residues opposite one another are specified by a pair of complementary codons in the DNA; Blalock and Bost have indeed shown that complementary pairs of codons specify amino acids of opposite hydropathy. A model is proposed to explain how hydropathic complementarity can lead to interaction between peptides. We propose that in the interacting peptides hydrophilic residues of both chains are oriented toward the aqueous solvent, while the hydrophobic ones form the interphase between the two chains. Tight packing is made possible by the stipulation that whenever a hydrophilic residue turns toward the aqueous phase, a space is liberated which can accommodate a hydrophobic residue from the opposing chain. This entropy-driven configuration can lead to strong interactions between portions of peptides consisting of hydropathically complementary residues.

Adrenocorticotropic Hormone↗
PubMed1988

The relevance of plasminogen activators to neoplastic growth. A review of recent literature.

The topics reviewed in this article include transcriptional regulation of plasminogen activators, their relevance to differentiation, tumor progression, and to the metastatic spread of cancer. Recent information on the nature of cellular plasminogen activator receptors is also discussed. Particular attention is paid to the increasing number of observations indicating that several of the inducers of plasminogen activator synthesis utilize distinct regulatory pathways.

Humans↗
PubMed1987

Plasminogen activator content of gynecological tumors and their metastases.

The plasminogen activator content of surgically excised gynecological tumors was measured with an azocaseinolytic assay. Ovarian (10 primary, 18 metastases) and uterine (5 primary and 6 metastases) tumors showed similar mean activator activities (21 CTA units/g tissue) mainly of the urokinase type with similar wide variations in each group. About 44% (14 of 32) of the tissues placed in short term organ culture were shown to produce and secrete urokinase activity. Results of the plasminogen activator activity found in the patient tumors or produced by the tumors during culture in the absence or presence of some drugs indicate a wide range of individual variations in sensitivity to these agents.

Aged↗
PubMed1986

Aminocaproic acid (AMICAR) in advanced colorectal carcinoma.

We treated 20 patients with measurable histologically confirmed colorectal adenocarcinoma with aminocaproic acid (AMICAR). There were 11 males and 9 females with a median age of 63 years. All 20 patients had received prior chemotherapy. The majority of monitoring lesions were distributed between lung and liver. We evaluated 12 patients in this series for response. Three patients had stable disease and nine patients had progressive disease. All patients were evaluable for toxic effects, the most common being nausea and vomiting. AMICAR given orally at 210 mg/kg of actual body weight/day is not an effective single agent in the treatment of metastatic colorectal carcinoma. In view of previously published animal data the role of AMICAR in the adjuvant setting for colorectal carcinoma still needs to be determined.

Adenocarcinoma↗
PubMed1985

Localization of plasminogen activators in human colon cancer by immunoperoxidase staining.

The immunoperoxidase technique, using antibodies against human urinary urokinase (Mr 55,000), was used for the localization of this enzyme in histological preparations of human colon tumors and normal colon tissue. The localization of tissue (vascular) activator was also investigated using antibodies against enzyme purified from human malignant melanoma. Both the "indirect method" and the peroxidase-antiperoxidase technique were found to be useful. Urokinase-reactive material was found in all tissues examined (33 primary cancers, 11 metastases, and 8 adenomas). In the normal colon, urokinase was found only in some of the goblet cells of the mucosal epithelium. In colon cancer, diffuse specific staining was observed in the cytoplasm, but the most intense staining was localized at the edge of the cancer cells bordering the lumen of the glands. In some cases, intense supranuclear staining could be observed in a location corresponding to the Golgi apparatus. In a few instances, urokinase could be seen associated with fibroblasts near the advancing front of an invading tumor. Adenoma, a benign tumor but often a precursor of cancer, also showed the presence of urokinase. Most significant were the observations showing that, in regions of the mucosal glands where normal epithelial cells were abruptly replaced by cancer cells, the appearance of cytoplasmic urokinase showed strict and exclusive association with the malignant cells, and the same was the case in transitions from normal epithelium to adenoma. In contrast to urokinase, tissue plasminogen activator was not associated with cancer cells, but was consistently present in the stroma which separates the cancer glands and was localized in the endothelium of the blood vessels. This visual evidence was supported by results of extraction of plasminogen activators from tumors, and from the separated mucosal and submucosal layers of the normal colon of the same patients, which showed that urokinase is most abundant in the tumor tissue and least abundant in the submucosa, while tissue activator is most prevalent in the well-vascularized mucosa and submucosa and scarce in the usually poorly vascularized adenocarcinomas.

Aged↗
PubMed1985

[Baroreceptor reflexes after exposure to the hypotensive action of prazosin blocking postsynaptic alpha 1-adrenergic receptors].

The effect of prazosin, a selective blocker of post-synaptic alpha 1-adrenergic receptors, on baroceptor regulation was studied in experiments on narcotized rabbits. Following the intravenous administration of prazosin (5, 10 and 50 micrograms/kg) the blood pressure decreased, depending on the drug dosage. Transmission of the vasomotor activity to the vascular musculature was disrupted only partially. The pressor and depressor responses to changes in the output value of the baroreflex remained intact. The reaction of cardiac rhythm slowing in response to an increased pressure in the aorta disappeared. The sensitivity of the baroceptors was considerably elevated. In addition to the effector structures, prazosin influenced many other components of the system of the blood circulation reflex regulation.

Animals↗
PubMed1984

Plasminogen activator content and secretion in explants of neoplastic and benign human prostate tissues.

The plasminogen activators of surgically excised prostate cancers (43 specimens) and benign prostatic hyperplasias (33 specimens) were extracted with an acetate:arginine:detergent buffer, and the activities were quantitated with azocaseinolytic tests. Immunoinhibition with anti-urokinase antibody served to distinguish between activator types. The mean activator activities (total; urokinase type; and nonurokinase type) of the neoplastic group were about 2 times higher (p less than 0.05) than that of the benign prostatic hyperplasia tissues. Each group had more non-urokinase-type activator activity relative to urokinase type. Studies with autopsy tissues (13 specimens) revealed that different anatomical compartments of the prostate contain about the same mean activator activity, indicating that the site of origin of the disease did not influence the results. Immunoperoxidase staining for urokinase revealed its presence in the tumor cells and, to a lesser extent, in the epithelial elements of some benign ducts and glands but not in the connective tissue. The secretion and synthesis of activator activities were monitored in short-term (approximately 120 hr) organ cultures (serum-free media) of 21 neoplastic tissues. On the average, about 12 times more activity (approximately 80% as urokinase type) was recovered in the media and postculture tissue extracts than was present in preculture tissues. Similar results were observed with 10 benign prostatic hyperplasia specimens. Wide individual variations were present in both groups (1.5 to 322 times more activity than the initial values). Except for one case, urokinase-type activity was secreted continuously, while nonurokinase was secreted only initially in quantities similar to that present in preculture tissue extracts. After culture, tissue explants contained higher quantities of both activator activities than were present initially. Dexamethasone (10 or 100 microM) decreased secretion and/or synthesis of activators by about 70%. This human organ culture model appears to be a reproducible system for individual tissues and may prove to be a valuable tool for further studies.

Dexamethasone↗
PubMed1984

Plasminogen activators in human malignant melanoma.

Metastatic malignant melanomas from 16 patients, extracted with Triton X-100, were analyzed for plasminogen activator activity by azocaseinolysis . In 6 cases tumor explants were set up also in short-term organ culture, and the rate of plasminogen activator secretion into the culture medium was determined. Both the extractable activator content [8.66 +/- 7.8 "Committee on Thrombolytic Agents" (CTA) U/g tissue] and the activator secretion rates (0.90 +/- 1.6 CTA U/g/hr) were low in comparison with values for other human tumors. In addition to the activity, the type of plasminogen activator also was determined by immunoinhibition with goat antihuman urokinase antibody in the azocaseinolytic assay, as well as by sodium dodecyl sulfate (SDS) gel electrophoresis followed by zymography on fibrin-agar, in the presence and absence of antibody. On the average, 77% of the activator activity was of the urokinase type in the extracts, and 90% in the culture fluids. Immunoperoxidase reaction for the detection of urokinase showed this enzyme to be localized mainly in the cell membrane of the melanoma cells; stromal elements showed no specific staining. These results are of interest in view of the findings made recently by investigators in several laboratories that in all but one of the melanoma cell cultures derived from metastatic human tumors, only the vascular type ("tissue activator") was cell associated or was secreted into the culture medium. The possible reasons for this discrepancy are discussed.

Adolescent↗
PubMed1983

Plasminogen activator secretion of human tumors in short-term organ culture, including a comparison of primary and metastatic colon tumors.

The secretion of plasminogen activator by explants of 92 human malignant tumors was studied in short-term organ culture. Where possible, adjacent normal tissue of the presumed origin of the tumors was also studied. The study included adenocarcinomas of the lung, colon, prostate, breast, and stomach and different types of sarcomas. In addition to the measurement of secretion rates, all tissues were quantitatively extracted to determine the amount of cell-bound enzyme. Both culture fluids and extracts were analyzed with respect to the type of plasminogen activator they contained by immunoinhibition with goat immunoglobulin G formed against purified human urinary urokinase sodium dodecyl sulfate:gel electrophoresis followed by zymography. The study yielded the following conclusions: (a) the measurement of plasminogen activator secretion rates gives a much sharper differentiation between malignant and normal tissues than does the amount of extractable enzyme; (b) the enzymes secreted in short-term organ culture are, in the great majority of the cases studied, of the urokinase type, even when a large fraction of the activator contained in the tissue is of the vascular type; (c) the secretion rates of metastatic tumors of the colon are much lower than those of the primary ones; (d) immunoperoxidase staining of tissue sections reveals that urokinase is localized predominantly in the tumor cells. The low secretion rates of metastatic tumors, probably a reflection of this property in the original cell that gave rise to the metastatic focus, could be of advantage to circulating cancer cells. Such cells would not dissolve the microthrombus thought to be essential for the arrest of cancer cells in the capillaries of target organs.

Adolescent↗
PubMed1982

Interference with dimethylhydrazine induction of colon tumors in mice by epsilon-aminocaproic acid.

The antifibrinolytic agent epsilon-aminocaproic acid given in the drinking water to Swiss ICR/Ha mice significantly counteracted the appearance of colorectal tumors induced by 21 weekly infections of 1,2-dimethylhydrazine. The drug affected both the number and the location of the tumors and, in some animals, altogether prevented their appearance. The low concentrations of epsilon-aminocaproic acid in the plasma of four control mice given the agent labeled with carbon-14 for 3 days suggest that the effect may depend not on inhibition of plasminogen activator activity, but on interference with the binding of some substance to the strong lysine binding site of plasminogen.

Adenocarcinoma↗
PubMed1981

Plasminogen activator content of neoplastic and benign human prostate tissues; fibrin augmentation of an activator activity.

The plasminogen activator content of the extracts of excise prostate cancers (25 specimens) was determined with an azocasein assay and found to be on the average 1.7 times higher than that of extracts of excised prostate benign hyperplasias (29 specimens). Both groups contained the same average percentage of human urokinase type activator (approximately 45%) as determined by the inhibition of activity when anti-human urokinase antibody was included in the assay system. The two types of activators were partially purified and found to have distinctly different properties. The most striking difference was the large augmentation of activity o the non-urokinase enzyme in fibrinolysis. The implications of an enhanced fibrinolysis relative to azocaseinolysis (or other) is discussed, particularly with respect to its importance in the quantitation and characterization of activators by different investigators. Highly purified urokinase-like activator was found to be similar to commercial urokinase preparation with respect to molecular weight, isoelectric point, inhibition by the antibody, and inhibition by placenta inhibitor.

Fibrin↗