[Purification and biochemical characteristics of myosin from rat malignant sarcoma-45]

Myosin was purified from rat tumour sarcoma-45 whose properties (effects of cations on ATPase activity, substrate specificity, temperature- and pH-optima, thermal stability, sensitivity of Mg2(+)-ATPase to F-actin, molecular mass, subunit composition) are similar to those of fast skeletal muscle myosin. Some parameters of the protein, namely, the levels of Ca2(+)- and K+, EDTA-ATPase activity, relative content of myosin light chains with Mr 16500 and the degree of tumoural myosin Mg2(+)-ATPase activation by F-actin, were significantly lower than those of skeletal muscle myosin.

Evidence that tumor necrosis induced by aminated beta 1-3D polyglucose is mediated by a concerted action of local and systemic cytokines

Aminated beta 1-3D polyglucose (AG) causes regression of Meth A sarcoma in syngeneic mice when injected systemically on day 7 after tumour inoculation. AG does not concentrate in the tumour, but distributes throughout the body. AG treatment causes release of large amounts of interleukin 1 (IL-1) both in vivo and in macrophage cultures in vitro. AG is a weak stimulus for tumour necrosis factor (TNF) release both in vitro and in vivo. However, tumour tissue and sera from untreated mice on days 3 and 7 after inoculation contain significant amounts of TNF, whereas tumour tissue and sera on day 14 contain insignificant amounts of TNF. This correlates exactly with the sensitivity to AG treatment. IL-1, and TNF when injected locally cause reduction in tumour blood circulation and also shrinkage of the tumour. All these facts taken together indicate that the tumour circulatory failure and necrosis induced by AG are mediated by local TNF-unrelated to the treatment--potentiated by systemic cytokines triggered by the AG.

[Changes induced by sarcolysine in vivo in the composition of DNA-bound lipids in sarcoma 37]

The two DNA fractions were isolated from sarcoma 37 by the use of the phenol method: supramolecular complex of DNA (SC DNA, 60%) and "phenol" nuclear matrix DNA (PNM DNA, 40%). The lipids in SC DNA represented of light and tightly bound components, the latter was similar to the lipid composition of PNM DNA. SC DNA contains 20 micrograms of neutral lipids (NL) and 6.5 micrograms of phospholipids (PL), while PNM DNA contains 9.8 micrograms of NL and 3.5 micrograms of PL per mg DNA. SC DNA-bound lipids of sarcoma 37 are deficient in free cholesterol (FC, 13%), but rich in cholesterol esters (CE, 39%) and free fatty acids (FFA, 23%); very rich in cardiolipin (CL, 43%) and phosphatidylethanolamine (PE, 28%), but deficient in phosphatidylcholine (PC, 12%). The tumor contains triglycerides (TG) that is absent in DNA of the normal cells. The injection of sarcolysine (10 micrograms/kg) markedly increased (1.5-3 times) the content of all LN and PL fractions in SC DNA, which was accompanied by both the accumulation of FC, TG, PC and the reduction of the remaining lipid fractions in PNM DNA. It is supposed, that DNA-bound lipids may be the target for the action of sarcolysine.

Structure of the major concanavalin A reactive oligosaccharides of the extracellular matrix component laminin

Laminin, a high molecular weight (1,000,000) glycoprotein component of basement membranes, was isolated from the EHS murine tumor as a noncovalent complex with entactin by lectin affinity chromatography using the alpha-D-galactosyl binding lectin Griffonia simplicifolia I (GS I). Entactin was removed from this complex by passage over Sephacryl S-1000 in the presence of SDS. Compositional analysis showed that the affinity-purified laminin contained 25-30% carbohydrate by weight. Methylation analysis revealed that the oligosaccharides of laminin contained bi- and triantennary chains, the blood group I structure, and repeating sequences of 3Gal beta 1,4GlcNAc beta 1 units. Free oligosaccharides were derived from the asparagine-linked glycans of affinity-purified laminin by hydrazinolysis, re-N-acetylation, and reduction with NaB3H4. When fractionated by affinity chromatography on concanavalin A (Con A)-Sepharose, 80% of the oligosaccharides passed through the column unretarded and a single peak corresponding to 20% of the oligosaccharides was adsorbed and specifically eluted with a linear gradient of 0-30 mM methyl alpha-D-glucopyranoside. Further fractionation of the Con A reactive oligosaccharides on GS I-Sepharose demonstrated that 70% of these oligosaccharides possess at least one terminal nonreducing alpha-D-galactopyranosyl unit. The Con A reactive oligosaccharides were subjected to sequential digestion with endo- and exoglycosidases, and the reaction products were analyzed by gel filtration chromatography on a column of Bio-Gel P4. We thereby obtained evidence for a variety of structures not previously reported to exist on murine laminin including hybrid biantennary complex and biantennary complex structures containing poly(lactosaminyl) repeating units. The poly(lactosaminyl) units occur either on one or on both branches of the biantennary chains, as well as in more highly branched blood group I poly(lactosamine) structures. All sialic acid is present as N-acetylneuraminic acid linked alpha 2,3 to galactose.

Isolation and characterization of proteins cross-linked to DNA by the antitumor agent methylene dimethanesulfonate and its hydrolytic product formaldehyde

This study attempted to characterize proteins cross-linked to DNA of Yoshida lymphosarcoma cells treated with methylene dimethanesulfonate (MDMS) and its hydrolytic products formaldehyde (HCHO) and methanesulfonic acid (MSA). MDMS and HCHO treatments produced a similar extent and type of DNA-protein cross-linking in Yoshida lymphosarcoma cells. All five major histones (H1, H2a, H2b, H3, and H4) were among the nuclear proteins cross-linked to DNA. Certain discrete differences were also apparent in these studies. MDMS cross-linked proteins of 29 and 48 kDa to DNA that were not observed following HCHO treatment alone, and HCHO cross-linked a 26-kDa protein to DNA that was not observed following MDMS treatment. Because semicarbazide prevented all MDMS-induced DNA-protein cross-linking, HCHO must be the component responsible for this lesion. The 26-kDa protein has been identified as an H4-H2b dimer. The formation of this dimer is particularly sensitive to MSA release on hydrolysis of MDMS because, in the presence of MSA, HCHO preferentially cross-linked an H2a-H2b dimer and a 48-kDa non-histone protein to DNA. Differences in DNA-protein cross-linking between these two agents are therefore proposed to arise from discrete changes in chromatin structure induced directly by MSA release.

Demonstration of tumor-selective retention of fluorinated nitroimidazole probes by 19F magnetic resonance spectroscopy in vivo

We have evaluated two fluorinated misonidazole analogues, Ro 07-0741 and CCI-103F, as potential probes for the non-invasive identification of hypoxic tumor cells by 19F magnetic resonance spectroscopy (MRS) in vivo. The equipment used was a 1.9 T Oxford Research Systems TMR-32 spectrometer, fitted with a 15 mm diameter surface coil. Signal was readily detectable, with similar intensity from EMT6 tumor, liver, and brain at early times (1-2 hr) after i.v. injection in BALB/c mice, indicative of an initial uniform biodistribution of parent probes. At later times (5-10 hr) there was a progressive reduction in signal intensity from brain and liver, but tumor levels remained constant or declined more slowly. This is illustrated by tumor/brain ratios at 6-7 hr of 2.9 (Ro 07-0741) and 4.2 (CCI-103F). In 4/5 mice analyzed at 20-24 hr after Ro 07-0741, and 1/2 following CCI-103F, tumor signal remained detectable. This occurred in the absence of parent probe as measured by HPLC, suggesting the involvement of a product of nitroreductive bioactivation. Studies with KHT and RIF-1 tumors in C3H/He mice showed a similar trend but retention in RIF-1 was less dramatic, and this was consistent with the known hypoxic fractions and comparative in vivo nitroreductase activities. These promising results support the continuing development of 19F nitroimidazole probes for non-invasive identification of hypoxic cells in vivo.

Characterization of a novel glycoprotein isolated from the basement membrane matrix of the Engelbreth-Holm-Swarm tumor

A previously undescribed protein has been isolated and purified from the extracellular matrix of the Engelbreth-Holm-Swarm (EHS) tumor, a murine tumor that synthesizes an extensive matrix composed of basement membrane molecules. Molecular characterization of the molecule determined that it is a glycoprotein with internal disulfide bonds and an isoelectric point of 6.0. Electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the glycoprotein migrated as a diffuse band with a molecular weight of approximately 72,000-80,000. The amino acid composition was significantly different from known basement membrane components. Polyclonal antibodies that specifically recognize the glycoprotein localized it to the kidney glomerular basement membrane. These antibodies did not cross-react with either known basement membrane components (laminin, type IV collagen, and heparan sulfate proteoglycan), with 70K "culture shock" protein or with components of normal mouse serum (including mouse transferrin, albumin, or alpha-fetoprotein), when analyzed by "Western" immunoblots. Our data indicate that the glycoprotein is synthesized by the EHS tumor cells and is present at relatively high levels in the EHS tumor matrix.

Comparative immunohistochemical reactivity of monoclonal and polyclonal antibodies to H-ras p21 in normal and neoplastic tissues of rodents and humans

Five mouse monoclonal antibodies (mES 2, 4, 8, 13 and 20) produced against bacterially expressed BALB ras p21 and five other monoclonal or polyclonal antibodies (Cetus rabbit or mouse pan p21, RAP-5, Triton Ha-ras, Y13-259) to H-ras p21 were used for comparative immunohistochemical detection of H-ras p21 by the avidin biotin peroxidase-complex technique in selected normal fixed tissues and tumors from rats, mice, and humans. Nine of these antibodies were immunoreactive with cell membranes and cytoplasm of harvey sarcoma virus-induced sarcoma cells, but usually only with Bouin's fixed tumors. A few normal tissues were immunoreactive with some of the antibodies except for many immunoreactive tissues found with mES 13. Although mES 13 stained sarcoma cells on the cell membrane, a prominent granular staining, which appeared to be mitochondrial or lysosomal, was seen in many normal and neoplastic rodent tissues and in normal human colon, colon polyps, and carcinomas. Interpretation of positive immunoreactivity with any antibody was sometimes difficult due to nonspecific (background) staining. The cellular pattern of specific reactivity (membrane or granular) and inhibition of immunoreactivity by absorption of the antisera with H-ras p21 was therefore important. Western blots with BALB transforming (Lys 12) p21 expressed in E. coli revealed reactivity of all antibodies except for RAP-5. In addition, immunoblots of solubilized proteins from the EJ cell line with RAP-5 indicated reactivity of this monoclonal antibody with proteins of several different molecular weights. RAP-5 also never specifically immunoreacted with cell membranes of normal or malignant cells including EJ cells. Interpretation of these findings in comparison with those in published reports of H-ras p21 localization in fixed tissue sections is discussed, including the importance of fixative, specific antibody and controls.

The use of electron microscopy and immunocytochemistry to characterise spontaneously-arising, transplantable rat tumors

When examined by light microscopy, transplanted animal tumors frequently bear little resemblance to the original neoplasm. If such tumors are to be used as models of human cancer they should be characterised as regards extant rather than historical features. Consequently, we have examined, by electron microscopy and immunocytochemistry, five spontaneously arising tumors transplantable in the WAB/Not rat that are currently diagnosed on the basis of historical features only. A typical sarcoma was used for comparison. Of four spontaneously arising tumors previously classified as carcinoma, Sp4 possessed epithelial features on both ultrastructural and immunocytochemical analysis, Sp107 on ultrastructural analysis only and Sp15 and Sp22 by neither technique. Expression of vimentin was most marked with Sp15 and Sp107. The putative sarcoma, Sp24, showed clear evidence of epithelial differentiation but no evidence of vimentin expression. This study (a) records the phenotypic drift of experimental tumors on transplantation (most clearly with Sp107) and the co-expression of cytokeratins and vimentin in putative carcinomas, (b) confirms the inadequacy of routine histology for accurate characterisation of such tumors and (c) details techniques for a more thorough assessment of state of differentiation that should guide the choice of experimental model.

Laminin, a multidomain protein. The A chain has a unique globular domain and homology with the basement membrane proteoglycan and the laminin B chains

Laminin (Mr = 800,000) is a glycoprotein consisting of three chains, A, B1, and B2, and has diverse biological activities. Previously we reported the complete primary structure of the B1 and B2 chains of mouse laminin deduced from cDNA sequence (Sasaki, M., Kohno, K., Kato, S., Martin, G. R., and Yamada, Y. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 935-939; Sasaki, M., and Yamada, Y. (1988) J. Biol. Chem. 262, 17111-17117). Here we describe the isolation, characterization, and sequence of cDNA clones spanning 9,520 bases which encode the entire A chain of mouse laminin. The nucleotide sequence of the clones contains an open reading frame of 3,084 amino acids including 24 amino acids of a signal peptide. The A chain contains some eight distinct domains including alpha-helices, cysteine-rich repeats and globules. There is considerable sequence and structural homology between the A chain and the B1 and B2 chains. However, the A chain has a unique globular structure containing homologous repeats at the carboxyl terminus and constituting one third of the molecular mass of the chain. Furthermore, the A chain contains three globules and three cysteine-rich domains at the amino terminus, whereas the B1 and B2 chains have only two each of such domains. The A chain shows homology to the basement membrane heparan sulfate proteoglycan core protein and the extracellular domain of the Drosophila neurogenic protein Notch. There is an RGD (Arg-Gly-Asp) sequence in one of the cysteine-rich domains of the A chain. This potential cell binding sequence could be active as another adhesion signal in addition to the previously identified cell binding sequence YIGSR (Tyr-Ile-Gly-Ser-Arg) of the B1 chain.

A recessive cellular mutation in v-fes-transformed mink cells restores contact inhibition and anchorage-dependent growth

A contact-inhibited revertant of mink cells transformed by the Gardner-Arnstein strain of feline sarcoma virus was isolated by fluorescence-activated sorting of cells stained with the mitochondria-specific dye rhodamine 123. The revertant cell line exhibited a decrease in its proliferative rate and saturation density and a complete loss of its capacity for anchorage-independent growth, but it remained tumorigenic when inoculated into nude mice. The revertant cells retained a rescuable Gardner-Arnstein feline sarcoma provirus, expressed high levels of the v-fes oncogene product and its associated tyrosine kinase activity, manifested elevated levels of phosphotyrosine-containing cellular proteins similar to those observed in v-fes-transformed cells, and were refractory to retransformation by retroviruses containing the v-fes, v-fms, and v-ras oncogenes. Fusion of the revertant and parental cells generated somatic cell hybrids which formed colonies in semisolid medium, indicating that the block in transformation was recessive. These data together with the observation that the revertant phenotype is unstable in continuous culture suggest that the loss of transformation is due to the presence of limiting quantities of a gene product which functions downstream of the v-fes-coded kinase in the mitogenic pathway.

Two human tumors with high basement-membrane-producing potential

Two human tumors, an adenoid cystic carcinoma and a yolk sac tumor, were found by immunocytochemical, ultrastructural, and biochemical studies to contain abundant basement membrane matrix in contrast to the vast majority of human tumors which contained either an absent or scant basement membrane matrix. These tumors were established as xenografts in athymic (nude) mice. Both xenografts maintained characteristic histologic features, immunocytochemical localization of basement membrane components, and reasonable yields of native laminin and Type IV collagen throughout three successive transplant generations. Although only a small fraction of the yield of that of the murine Engelbreth-Holm, Swarm (EHS) sarcoma, the yield of the human basement membrane-producing tumors could be increased by rendering the mice lathyritic. The human basement membrane proteins so extracted were identical on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to their murine counterparts. These human tumors then represent a potential source of human basement membrane proteins.

Immunogold quantitation of laminin, type IV collagen, and heparan sulfate proteoglycan in a variety of basement membranes

A series of basement membranes was immunolabeled for laminin, type IV collagen, and heparan sulfate proteoglycan in the hope of comparing the content of these substances. The basement membranes, including thin ones (less than 0.3 micron) from kidney, colon, enamel organ, and vas deferens, and thick ones (greater than 2 micron), i.e., Reichert's membrane, Descemet's membrane, and EHS tumor matrix, were fixed in formaldehyde, embedded in Lowicryl, and treated with specific antisera or antibodies followed by anti-rabbit immunoglobulin bound to gold. The density of gold particles, expressed per micron2, was negligible in controls (less than or equal to 1.1), but averaged 307, 146, and 23, respectively, for laminin, collagen IV, and proteoglycan over the thick basement membranes (except for Descemet's membranes, over which the density was 16, 5, and 34, respectively) and 117, 72, and 64, respectively, over the lamina densa of the thin basement membranes. Lower but significant reactions were observed over the lamina lucida. Interpretation of the gold particle densities was based on (a) the similarity between the ultrastructure of most thick basement membranes and of the lamina densa of most thin basement membranes, and (b) the biochemical content of the three substances under study in the EHS tumor matrix (Eur J Biochem 143:145, 1984). It was proposed that thick basement membranes (except Descemet's) contained more laminin and collagen IV but less heparan sulfate proteoglycan than the lamina densa of thin basement membranes. In the latter, there was a fair variation from tissue to tissue, but a tendency towards a similar molar content of the three substances.

Macrophages associated with murine tumours express plasminogen activator activity

The fibrinolytic activity of cancer cells has been repeatedly implicated in mechanisms of local spread and tumour invasiveness. Mononuclear phagocytes associated with solid tumours might also contribute to fibrin dissolution at the tumour/host interface through the expression of plasminogen activator (PA) activity. We have investigated the PA activity of tumour-associated macrophages (TAM) from 4 transplanted murine tumours in syngeneic hosts; peritoneal macrophages (native and thioglycolate-elicited) from both tumour-bearing and control animals were studied as reference cells. TAM from 3 tumours (MSV, mFS6, MN/MCAI) had basal levels of PA activity (20% plasminogen-independent) comparable to or higher than those of thioglycolate-elicited peritoneal macrophages from the same tumour-bearing animals. TAM isolated from 1 tumour (MS2) had a PA which was very low (60% plasminogen-independent), but higher than the activity of unstimulated peritoneal macrophages. Molecular analysis of PA by SDS-PAGE electrophoresis and fibrin autography revealed in all macrophages a single species having an apparent MW of 48 kDA. It thus appears that, in some experimental neoplasms, tumour cell vicinity may represent an in vivo stimulus for macrophage PA expression.

Separation and characterization of the subunits of the laminin of EHS sarcoma

A rapid and sensitive method was developed for the preparative separation of laminin subunits. Laminin was extracted and purified from mouse EHS sarcoma. On SDS-PAGE, the reduced and carboxymethylated molecule separated into two components corresponding to molecular weights of about 400 KDa (subunit A) and 200 KDa (subunit B). These two subunits were preparatively separated using heparin-agarose affinity chromatography. The larger subunit quantitatively adhered to the affinity column while the smaller one did not adhere. Amino acid analyses of the separated subunits showed distinct differences. Subunit B was further resolved into two distinct polypeptides of 200 KDa, B1 and B2, by means of reverse-phase HPLC. Although the amino acid compositions of B1 and B2 were very similar, the peptide maps generated by digestion of the B1 and B2 chains with Staphylococcus aureus V8 protease or by cyanogen bromide showed B1 and B2 to differ from each other. Thus, at least three different polypeptide subunits are present in this laminin and probably arise from separate gene origins. These studies provide a basis for the subsequent localization and analysis of the specialized structural and functional domains of laminin.

Comparison of fluorescence intensity of Hoechst 33342-stained EMT6 tumour cells and tumour-infiltrating host cells

Hoechst 33342 is a fluorescent dye used for cell selection from tumours based upon intratumour location. When the dye is administered i.v. to tumour-bearing animals, cellular fluorescence is directly related to the proximity of cells to blood vessels. The present study compared inherent Hoechst fluorescence between in vitro-stained EMT6/Ro (mouse mammary sarcoma) cells and host cells, to determine if these populations have different staining characteristics that may influence cell selection procedures. Tumour cell fluorescence exceeded host cell staining by 8-fold when pure cell populations (EMT6/Ro monolayer cells, mouse spleen and peritoneal cells) were compared, and 3-fold for tumour cell-enriched and host cell-enriched populations from solid tumours. Inherent uptake of HO 33342 appeared to be correlated with cell volume. These differences in inherent dye uptake between host and tumour cells were found to be minor in comparison to the fluorescence gradient between the 10% brightest and 10% dimmest (78-fold) cell populations from in vivo-stained tumours.

Structure and affinity for antithrombin of heparan sulfate chains derived from basement membrane proteoglycans

Metabolically 35S- or 3H-labeled heparan sulfate was isolated from murine Reichert's membrane, an extraembryonic basement membrane produced by parietal endoderm cells, and from the basement membrane-producing Engelbreth-Holm-Swarm mouse tumor. The polysaccharides were subjected to structural analysis involving identification of products formed on deamination of the polysaccharides with nitrous acid. The polysaccharide from Reichert's membrane contained N- and O-sulfate groups in approximately equal proportions. It bound almost quantitatively and with high affinity to antithrombin. A high proportion of antithrombin-binding sequence was also indicated by the finding that 3-O-sulfated glucosamine residues accounted for about 10% of the total O-sulfate groups. In contrast, at least 80% of the sulfate residues in the heparan sulfate isolated from the mouse tumor were N-substituents. Only a minor proportion of this polysaccharide bound with high affinity to antithrombin, and no 3-O-sulfated glucosamine residues were detected. These results are discussed in relation to the possible functional role of heparan sulfate in basement membranes.

Detection of an intracellular transforming protein (v-Ki-ras p21) using the flow activated cell sorter (FACS)

The transforming protein coded for by the Ki-ras oncogene, v-p21, localizes at the cytoplasmic face of the plasma membrane. A method is presented whereby the appearance of v-p21 in Kirsten murine sarcoma virus-transformed cells can be detected by flow cytometry, using a monoclonal antibody to v-p21 and methods modified from immunofluorescence microscopy. The method is sufficiently sensitive to differentiate between cellular and viral p21 levels, to detect small subpopulations of virus-transformed cells, and to monitor changes in p21 expression in response to physiologic variables. The method provides a rapid, quantitative means to investigate the expression of an intracellular transforming protein in heterogeneous cell populations.

Comparison of non-collagenous type IV collagen components in the human glomerulus and EHS tumor

A method for the isolation of the NC1 domain of type IV collagen has been developed using the EHS sarcoma, a basement membrane-producing mouse tumor. This NC1 domain has been compared to the NC1 of human glomerular basement membrane (hGBM) to assess its usefulness in the biochemical characterization of the Goodpasture antigen which is associated with NC1. Both NC1 isolates appeared to migrate by gel filtration as hexamers (Mr 160,000) and in SDS-polyacrylamide gel electrophoresis as dimers and monomers (Mr 54,000 and 26,000), and were shown to share biochemical identity by amino acid analysis. The hGBM NC1 showed greater complexity in the monomer region, and when compared by two-dimensional gel electrophoresis was found to contain more components in both regions than EHS NC1. Anti-GBM autoantibodies from patients with Goodpasture's syndrome reacted with the EHS NC1 by immunoblotting of two-dimensional gels. The EHS NC1 isolated by reverse phase HPLC partially inhibited the reactivity of the anti-GBM autoantibodies against hGBM NC1 by inhibition ELISA assay. Reverse phase HPLC elution of EHS and hGBM NC1 showed differences in subunit composition and interaction; complete dissociation of the EHS monomers and dimers in 0.1% trifluoroacetic acid was observed, whereas hGBM monomers and dimers eluted together. Rotary shadowing of hGBM NC1 domains revealed size heterogeneity of globular domains, compared with greater uniformity of EHS NC1 hexamers. We conclude that EHS NC1 contains an epitope(s) that is reactive with human autoantibodies to hGBM NC1. However, the immune response in Goodpasture's syndrome may involve antibodies directed against epitopes which are present in greater density and on a more complex array of peptides in the hGBM NC1 than in EHS NC1.

In vitro regulation of cartilage matrix assembly by a Mr 54,000 collagen-binding protein

In cartilage, type II collagen is present as thin, short, randomly oriented fibrils. In vitro, however, type II collagen forms fibrils of large diameter, indicating that additional factors may be involved in the regulation of collagen fibril formation. We have examined extracts of a cartilage-producing tumor for the presence of collagen-binding proteins. In addition to fibronectin and link protein, a Mr 54,000 protein was found to bind to collagen fibrils as well as to native and denatured type II collagen. Immunological studies using antibody against the protein indicate that it is a cartilage matrix protein, not present in bone or in several other tissues. In vitro studies show that the Mr 54,000 protein in combination with cartilage proteoglycan decreases the rate of type II fibril formation and causes the fibrils to be of small diameter (24 +/- 8 nm). These studies indicate that complexes between collagen and proteoglycans mediated by this protein may regulate the assembly of cartilage matrix.

Immunocytochemical localization of RasHa p21 in normal and neoplastic cells in fixed tissue sections from Harvey sarcoma virus-infected mice

An affinity purified sheep IgG antibody to a 20 amino acid peptide from the carboxyterminal end of RasHa p21 was used to localize RasHa p21 on fixed tissue sections of Harvey sarcoma (HaSV) virus-infected mice by the avidin-biotin-peroxidase immunocytochemical technique. Control sera included immune sheep sera absorbed with the peptide, preimmune sheep sera and a goat polyclonal antibody to Rauscher leukemia virus p30. Neonatal BALB/c mice were injected with HaSV/Moloney leukemia virus (MoLV), MoLV alone or buffer. Short-term fixation in Bouin's fixative was found to be the most effective method for demonstrating p21 in fixed tissue sections. RasHa p21 was found in 5-80% of the induced sarcoma cells, depending on the tissue fixative and antibody dilution. The antigen was localized to the cell membrane and in the cytoplasm. Tumors induced by NIH 3T3 cells transformed with cellular Ha-ras oncogenes had less than 1% immunoreactive tumor cells. Splenic erythroblasts in HaSV-induced erythroblastosis contained membrane antigen as did some reticular cells in lymph nodes draining the sarcomas. Normal tissues of virus-inoculated mice, uninoculated controls or fetuses and selected naturally occurring or induced liver tumors of mice, chemically induced skin tumors of mice, N-nitrosomethylurea-induced mammary tumors of rats, and naturally occurring tumors of F344/NCr rats did not contain immunoreactive p21. Thus, with the use of affinity purified IgG sheep polyclonal antibody to a peptide in RasHa p21, we were able to demonstrate RasHa p21 in tumors and other cells. The degree of immunoreactivity was related to the expected level of p21 expression.

Interaction between Raf and Myc oncogenes in transformation in vivo and in vitro

3611 MSV, a raf-oncogene-transducing murine retrovirus, induces fibrosarcomas and erythroid hyperplasia in newborn mice after a latency of 4-8 wk. In contrast, new recombinant murine retroviruses carrying the myc oncogene (J-3, J-5 construct viruses) do not induce tumors before greater than 9 wk. A combination of both oncogenes in an infectious murine retrovirus (J-2) induces hematopoietic neoplasms in addition to less prominent fibrosarcomas and pancreatic adenocarcinoma 1-3 wk after inoculation. The hematologic neoplasms consist of immunoblastic lymphomas of T and B cell lineage and erythroblastosis. If animals were inoculated with a variant of the J-3 virus, which induces altered foci in cultures of NIH 3T3 cells, carcinoma developed in the pancreas with a 2-6 mo latency. In parallel to the synergistic action of both oncogenes on hematopoietic cells in vivo, we find that raf-oncogene-induced transformation of bone marrow cells in culture is enhanced by the addition of myc, which by itself does not transform these cells when grown in standard media. We conclude that concomitant expression of raf and myc oncogenes in hematopoietic and epithelial cells alters their respective transforming activities. The contribution of v-myc in this synergism was examined by use of a series of recombinant murine retroviruses capable of expressing the avian v-myc to study the effect of altered myc expression on hematopoietic/lymphoid cells. With either interleukin 3- or interleukin 2-dependent cell lines, introduction of the recombinant viruses abrogated the requirement for IL 3 or IL 2 for growth, and associated with this was the suppression of c-myc expression. The findings suggest that myc is a component in the signal transduction pathway for IL 3 and IL 2 and support an autoregulatory mechanism of c-myc expression. In contrast to v-myc, expression of v-raf in primary lymphoid/hematopoietic cells has an immortalizing function without abrogating the requirement for IL 3 for growth. This suggests that v-raf and v-myc affect different components of growth regulation, as, for example, commitment (v-myc) and cell cycle progression (v-raf).

Enhanced granulopoiesis in mice transplanted with colony-stimulating factor-producing BMA1 tumor

Inoculation of BMA1 cells into BALB/c nude mice formed tumors (BMA1 tumor) that were transplantable into ddY mice, and induced marked granulopoiesis in vivo. Histological study revealed that the tumor was a fibrosarcoma, some parts of which were calcified, and consisted of hemopoietic foci surrounded by adipose tissue. This tumor was regarded as producing CSF in vivo as well as in vitro, since CSF activity was detected in sera of the tumor-bearing mice and tumor extract. Granulopoiesis and splenomegaly developed, associated with an increase of stem cells in the spleen. The number of CFUc and CFUs in the spleen increased to about 91 times and 21 times those of control mice, respectively, whereas the number of stem cells in the tibia did not change significantly. The number of peripheral leukocytes increased to 15 times that of normal mice and amounted to 78% of matured granulocytes. After tumor resection these hematological changes were reversed. The findings suggest that the granulopoiesis in BMA1 tumor-bearing mice may be induced by CSF produced by BMA1 tumor and that the spleen may be a direct target organ of the excessive amount of CSF.

Properties and functions of a nucleolus-specific phosphoprotein of mouse ascites sarcoma cells

A 110K-dalton phosphoprotein previously was isolated from the nucleoli of mouse ascites sarcoma cells. The localization of this phosphoprotein in the nucleoli was confirmed by an indirect immunofluorescence assay with rabbit antisera to the phosphoprotein. This phosphoprotein formed a complex of 280K daltons with a nonphosphoprotein of 32K daltons in a molar ratio of 1 to 1. The protein complex dissociated in the presence of 6 M guanidine hydrochloride or 1% sodium dodecylsulphate. The nucleolus-specific phosphoprotein complex bound preferentially to nucleolar DNAs other than the ribosomal RNA gene in vitro and located in nucleosomes prepared from the nucleoli. The major phosphoamino acid in the phosphoprotein was phosphoserine, and slight though significant amounts of phosphotyrosine and phosphothreonine also were detected. These phosphorylated amino acids were concentrated in a specific polypeptide fragment of about 30K daltons obtained by partial digestion with V8 protease. The phosphoprotein was phosphorylated in vitro by the protein kinase activity presented in the complex itself.

[Fibronectin in cultured mouse sarcoma cells induced by foreign bodies]

Indirect fluorescence was used to study distribution of fibronectin in cultured cells of 5 mouse foreign body-induced sarcomas (PS-4, PS-84, PS-100, PS-103, PS-130) and cells of early (2-3 months postimplantation) capsules surrounding implanted plastic films. Accumulation of pericellular or matrix fibronectin in dense cultures compared to sparse ones was noted in all the lines except PS-84. In confluent cultures of these lines, a three-dimensional fibrillar network of fibronectin typical for fibroblast-like cells was observed. The pattern was very similar to that found in dense cultures of non-neoplastic early capsule cells. The data obtained show that loss of pericellular fibronectin would not serve as a marker of neoplastic transformation in this cellular system.

Structure and interactions of heparan sulfate proteoglycans from a mouse tumor basement membrane

Various forms of heparan sulfate proteoglycan were solubilized from the mouse Engelbreth-Holm-Swarm (EHS) sarcoma by extraction with 0.5 M NaCl, collagenase digestion and extraction with 4 M guanidine. They could be separated into high (greater than or equal to 1.65 g/ml) and low (1.38 g/ml) buoyant density variants. The high-density form from the NaCl extract and collagenase digest had Mr = 130000 and So20,W = 4.5 S and contained 4-10% protein, indicating Mr = 5 000-12 000 for the protein core. This proteoglycan exhibited polydispersity as shown by rotary shadowing electron microscopy and ultracentrifugation. An average molecule consisted of four heparan sulfate chains (Mr = 29 000) each with a length of 32 +/- 10 nm. The low-density form (Mr about 400 000) could not be completely purified and contained about 50% protein. As shown by radioimmunoassay, the various proteoglycans shared similar protein cores. Labeling of the tumor in vivo or in vitro demonstrated preferential incorporation of radioactive sulfate in the high-density form. The high-density proteoglycan interacted in affinity chromatography by virtue of its heparan sulfate chains with laminin, fibronectin, the globular domain NC1 and the triple helix of collagen IV. These interactions were abolished at moderate concentrations of NaCl (0.1-0.2 M) and in the presence of heparin, chondroitin sulfate or dextran sulfate. Interactions with the globule NC1 could also be demonstrated by velocity band centrifugation in sucrose gradients and a binding constant of about 10(6) M-1 was derived.

Localization of proteoheparan sulfate in rat aorta

This study describes the distribution of heparan sulfate proteoglycan ( HSPG ) within the rat aorta using immunocytochemical (biotin-avidin-peroxidase) and immuno-electron microscopy (125I-autoradiography). Heparan sulfate proteoglycan was isolated from a basement membrane producing mouse EHS sarcoma ( Hassell et al. 1980) and used to generate antisera in rabbits. Light microscopic observations revealed intense immunostaining of the intima and media of normal aorta, adventitial vasa vasorum, and aortic intimal fibromuscular thickenings induced by experimental injury (balloon de-endothelialization). Immunoelectron microscopy using 125I labeled antibodies to HSPG revealed that proteoheparan sulfate was localized to the amorphous layer of basement membrane below aortic and capillary endothelium. In addition, labeled anti- HSPG could be localized to the external lamina surrounding the smooth muscle cells in the hyperplastic intima. These studies reveal that antibodies prepared against a proteoheparan sulfate isolated from a basement membrane producing EHS sarcoma cross react with basement membrane structures within the aortic wall. Furthermore, these results demonstrate that the basement membranes beneath aortic and capillary endothelium and the external lamina surrounding aortic smooth muscle cells contain a heparan sulfate proteoglycan that is antigenically similar.

Glass-bead affinity chromatography of cell attachment and spreading-promoting factors of human serum

The glass-binding properties of a number of purified glycoproteins capable of promoting attachment and spreading of a variety of types of animal cells in culture have been examined. Two such factors in human serum, fibronectin and serum spreading factor, exhibited strong affinities for glass beads and could be eluted from glass-bead columns under similar conditions. A number of other glycoproteins of human serum that do not promote cell adhesion did not bind to glass beads under conditions that resulted in binding of serum spreading factor or fibronectin. At a sufficiently low ratio of serum volume to glass-bead volume, human serum could be simultaneously depleted of serum spreading factor, fibronectin, and cell spreading-promoting activity by glass-bead affinity chromatography. Laminin, another cell spreading-promoting glycoprotein, possessed glass-binding properties similar to those of serum spreading factor and fibronectin while chondronectin, a fourth cell spreading-promoting factor of more limited specificity of biological activity and distribution in vivo, did not exhibit a strong interaction with glass beads under the same conditions. These observations suggest that glass-bead column affinity chromatography may prove useful as a general method for isolation and study of glycoprotein factors promoting attachment and spreading of cells in culture.

Solubility of a bone-inducing substance from a murine osteosarcoma

A bone-inducing substance (osteogenic factor) from a murine osteosarcoma was found to be soluble in 1% sodium lauryl sulfate (SDS), 1% deoxycholate, 1% Triton X-100, and 1% Nonidet P-40. A precipitate formed on removal of the detergents by dialysis against phosphate buffer, and this precipitate induced ectopic bone formation when implanted into allogeneic mice. The insoluble residue left after extraction with SDS or deoxycholate did not evoke new bone formation, indicating that the substance was solubilized completely. The bone-inducing substance was also partially solubilized with weak acids (pH, 2.6-3.0) but not with acidic solutions of lower or higher pH. These findings indicate that the solubility of the substance depends on the hydrogen ion concentration of the solution. The substance was not solubilized with EDTA or 6 M urea.

Identification of a laminin-like substance on the surface of high-malignant murine fibrosarcoma cells

High- and low-malignant murine fibrosarcoma cells were stained with anti-laminin antibodies using immunoperoxidase techniques and examined by electron microscopy. With the high-malignant cells, specific staining was observed along the cell surface. Use of normal rabbit serum in place of the rabbit anti-laminin or pretreatment of the anti-laminin with soluble laminin completely eliminated this staining. No immunoperoxidase staining was observed with the low-malignant cells. In additional studies, membrane fractions were prepared from the high- and low-malignant cells and used to immunize rabbits. The animals immunized with the membrane fractions from the high-malignant cells produced antibodies that reacted by enzyme-linked immunosorbent assay (ELISA) with murine laminin obtained from the EHS sarcoma. The animals immunized with membrane fractions from the low-malignant cells did not. These studies provide strong evidence that the high-malignant cells (but not the low) express on their cell surface a substance that is immunologically cross-reactive with laminin. In addition, the high-malignant cells (but not the low) secreted a material into the cell culture fluid that could be specifically immunoprecipitated with antilaminin antibodies. The immunoprecipitated material co-migrated with purified laminin when examined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis under reducing conditions. The existence of this substance associated with the surface of the high-malignant cells and its absence from that of the low-malignant cells may explain the previously noted difference between these cells in their ability to attach to type IV collagen. This difference may also contribute to the dissimilarity between these cells in their metastatic potential.

Nidogen: a new, self-aggregating basement membrane protein

Nidogen was purified from a mouse tumor basement membrane where it accounted for 2-3% of the total proteins. It was isolated as two forms (A and B) of a monomer (Mr = 80000) each consisting of a single polypeptide chain folded into a globular head connected to a small tail. The B form of the monomer was shown to be capable of aggregating into a nest-like structure (Mr greater than 250000). A smaller form (Mr = 45000) was observed in some of the extracts. The amino acid composition of nidogen was different to that of other basement membrane proteins. It contained about 10% carbohydrate, with N-linked and O-linked oligosaccharide chains in similar proportions. Isoelectrofocussing demonstrated a limited heterogeneity of nidogen with pI in the range 6.5 - 7. Monomeric nidogen failed to interact with other basement membrane components and heparin. Aggregation could be induced by limited proteolysis and was reversed by detergents or high salt concentrations. Together with the observation that most of the nidogen could be solubilized only after destroying the collagenous matrix, the data indicate that aggregation of nidogen reflects an activity involved in matrix assembly. Specific antibodies raised against nidogen did not distinguish between the monomeric and aggregated form of the protein but showed that the fragment was antigenically deficient. These antibodies did not cross-react with collagen type IV, laminin, entactin and heparansulfate proteoglycan. Immunofluorescence staining and absorption studies demonstrated that nidogen is a common component of authentic basement membranes. Larger forms of nidogen (Mr about 100000 and 150000) were found in organ cultures of Reichert's membrane suggesting that it is synthesized in precursor forms.

Incorporation of mannose 6-phosphate receptors into liposomes. Receptor topography and binding of alpha-mannosidase

A receptor that binds the lysosomal enzyme alpha-mannosidase via mannose 6-phosphate moieties (mannose 6-phosphate receptor) was purified from Swarm-rat chondrosarcoma and bovine liver microsomal membranes. Receptor-reconstituted liposomes were prepared by dialysis of taurodeoxycholate-dispersed lipids with purified mannose 6-phosphate receptor. Liposomes appeared by electron microscopy as 60-120 nm unilamellar vesicles. Receptor-reconstituted liposomes retained the ability to bind alpha-mannosidase specifically. Binding was saturable with an apparent Kd of 1 nM and was competitively inhibited by mannose 6-phosphate (Ki 2mM). Liposomes containing entrapped 125I-bovine serum albumin were used to demonstrate that treatment with 0.045% taurodeoxycholate rendered liposomes permeable to macromolecules without solubilizing the membrane. Receptor orientation in the liposome membrane was established by measuring binding of ligand to intact and detergent-treated liposomes. Unlike coated vesicles, which contain cryptic mannose 6-phosphate receptors [Campbell, Fine, Squicciarini & Rome (1983) J. Biol. Chem. 258, 2526-2533], treatment of liposomes with detergent revealed no additional cryptic binding sites. In addition, treatment of liposomes with 0.75% trypsin abolished total receptor binding activity. The results suggest that the receptor is inserted with its binding site facing the outside of the liposome.

Glycosaminoglycans of solid and ascites forms of the P1798 murine lymphosarcoma

Total glycosaminoglycan levels are similar from subcutaneous, ascites and mesenteric forms of the P1798 lymphosarcoma. However, P1798 cells implanted subcutaneously produce a solid tumor rich in hyaluronic acid with lesser amounts of chondroitin 4-/6-sulfates as well as an undersulfated species of chondroitin sulfate, while cells implanted intraperitoneally produce ascites tumors which generate hyaluronic acid, almost exclusively. Mice bearing advanced ascites tumors develop solid mesenteric tumors which exhibit chondroitin 4-/6-sulfates and under-sulfated chondroitin sulfate in addition to hyaluronic acid.

[Composition of gangliosides in experimental rat tumors]

Spectrum of gangliosides was studied in some tumors. It was the same in a hepatocellular carcinoma induced by N-nitrosomorpholine in Wistar rats as in control liver In addition, several tumors contained an unidentified fraction between GD1b and GT1b. There were total ganglioside differences both in tumours and controls. Lymphatic leukemia samples had lower contents of GD1a and higher contents of GM1 ganglioside. Spontaneous breast sarcoma of Lewis rats (SAM) failed to differ from a sarcoma of low grade malignancy induced by ferridextran (FL) with the exception of slight increase in GD1a and GD2. All the tumours contained higher gangliosides in concentration at least the same as controls.

Nuclear magnetic resonance imaging of a fibrosarcoma tumor implanted in the rat

Fibrosarcoma tumor cells were implanted in the hind legs of 25 rats and studied from the first to the sixth week postimplantation. Nuclear magnetic resonance imaging detected all tumors and did not yield any false-positives in five control rats. The T1 relaxation values of tumors overlapped those of muscle, and the T2 values overlapped those of fat, but the combination of the two values allowed discrimination of each of the three tissues with no overlap. The difference in relaxation time between tumor and muscle could be accounted for on the basis of water content, which was approximately 14% higher in the tumors. This study confirms data from previous studies suggesting that nuclear magnetic resonance imaging is a highly sensitive modality, but that T1 and T2 values are not specific for individual pathologic conditions.

Proteoglycans from the substratum adhesion sites of MSV-transformed BALB/c 3T3 cells

Kirsten murine sarcoma virus-transformed Balb/c 3T3 cells (KiMSV) are highly tumorigenic and metastatic in the appropriate murine host, are loosely adherent to the tissue culture substratum, and can be readily detached from the substratum by ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid treatment leaving their adhesion sites as substratum-attached material. Both long-term culture-generated adhesion sites (L-SAM) of KiMSV cells and newly formed adhesion sites of reattaching cells (R-SAM) contain high levels of hyaluronate (HA) and chondroitin sulfate (CS) whereas the R-SAM of parental Balb/c 3T3 cells is enriched in heparan sulfate (HS). A sizable fraction of KiMSV L-SAM proteoglycans (PG) and a smaller fraction of R-SAM PG's aggregate into two size classes of supramolecular complexes, after extraction off the substratum with 4 M guanidine hydrochloride, as determined by chromatography on columns of Sepharose CL2B in several buffer systems. Isopycnic density gradient analyses under associative conditions of KiMSV L-SAM generated three classes of material--high-density GA1 which contained some HA but principally CS and HS; intermediate-density GA2 which contained only HA; and low-density GA3 which contained some HA and principally glycoprotein. R-SAM gradients contained no GA2 but a sizable amount of "low-density" HA in GA3. When centrifuged under dissociative conditions, most of GA1 and all of GA2 from L-SAM shifted to the top of the gradient, whereas most of the HS-PG in R-SAM remained at the bottom of dissociative gradients. Comparison of these analyses with previous analyses of Balb/c 3T3 extracts demonstrates that (a) KiMSV cells generate adhesion sites with different PG contents than 3T3 sites; (b) the PG's of KiMSV sites have a reduced potential to aggregate into high-molecular-weight complexes but do form intermediate-size complexes not apparent in material from 3T3 sites; (c) these data support the hypothesis that HA is important in detachment of cells from extracellular matrices; and (d) HS-PG's in newly formed adhesion sites of KiMSV cells are considerably different from sites which have "matured," indicating that there is metabolic activity in these sites during prolonged adherence and movement of transformed cells.

Inhibition of glutathione synthesis augments lysis of murine tumor cells by sulfhydryl-reactive antineoplastics

GSH plays an important role in cellular defense against a wide variety of toxic electrophiles via the formation of thioether conjugates. We studied the role of GSH in murine tumor cell defense against a novel class of sulfhydryl-reactive antineoplastics, the sesquiterpene lactones (SL). Incubation of P815 mastocytoma cells with any of the four SL tested (vernolepin, helenalin, elephantopin, and eriofertopin) for 1 h resulted in 70-97% depletion of GSH. The importance of GSH resynthesis upon exposure of tumor cells to SL was evaluated with the use of buthionine sulfoximine (BSO), a selective, nontoxic inhibitor of gamma-glutamylcysteine synthetase. Inhibition of GSH synthesis with 0.2 mM BSO markedly enhanced SL-mediated cytolysis of four murine tumor cell lines. A 6- to 34-fold reduction in the amount of SL causing 50% lysis was obtained with BSO. Addition of BSO to P815cells either during or immediately after a 1-h pulse with 10 micrograms/ml of vernolepin increased cytolysis from less than 3% to 78-82%. However, a 1.5-h delay in the addition of BSO to such cells, which allowed for substantial resynthesis of GSH, reduced cytolysis to 30%. Recovery of GSH synthetic capacity after BSO treatment correlated with loss of the synergistic effect of BSO on lysis by vernolepin. BSO did not augment cytolysis by six other antineoplastics (doxorubicin, mitomycin C, vinblastine, cytosine arabinoside, maytansine, and 1,3-bis-[2-chloroethyl]-1-nitrosourea [BCNU]). Of these, only BCNU depleted cellular GSH. Lysis by jatrophone, another GSH-depleting antitumor agent, was increased 21-fold by BSO. Since prolonged incubation with BSO alone results in near-complete GSH depletion without loss of cell viability, SL-mediated cytolysis is probably not a result of GSH depletion. We have demonstrated, however, a critical role for GSH synthetic capacity as a determinant of tumor cell susceptibility to cytolysis by SL. GSH also plays an important role in cellular defense against oxidative injury. Vernolepin, acting as a GSH-depleting agent, markedly sensitized tumor cells to lysis by H2O2 (greater than 6.5-fold increase with 20 micrograms/ml of vernolepin). These findings suggest the possibility that the coordinated deployment of sulfhydryl-reactive antitumor agents, BSO, and oxidative injury might constitute an effective chemotherapeutic strategy.

Fibronectin in foreign body-induced sarcomas and preneoplastic cells

Foreign body (FB)-induced murine sarcoma cells and advanced preneoplastic cells as well as normal fibroblasts produce fibronectin (FN) in primary culture; cells at early preneoplasia do not. Hence, the neoplastic properties of FB-induced sarcomas do not depend on absence of FN. Temporary FN repression during early preneoplasia is associated with certain phenotypic cell characteristics.

Isolation and characterization of type IV procollagen, laminin, and heparan sulfate proteoglycan from the EHS sarcoma

We have studied the extractability of type IV collagen, laminin, and heparan sulfate proteoglycan from EHS tumor tissue growth in normal and lathyritic animals. Laminin and heparan sulfate proteoglycan were readily extracted with chaotropic solvents from both normal and lathyritic tissue. The collagenous component was only solubilized from lathyritic tissue in the presence of a reducing agent. These results indicate that lysine-derived cross-links and disulfide bonds stabilize the collagenous component in the matrix but not the laminin or the heparan sulfate proteoglycan. The majority of the collagen present in the extracts had a native triple helix based upon the pattern of peptides resistant to pepsin digestion and visualization in the electron microscope by the rotary shadow technique. This protein was composed of chains (Mr 185000 and 170000) identical in migration to the chains of newly synthesized type IV procollagen. This finding confirms earlier work that indicates that the biosynthetic form, type IV procollagen, is incorporated as such in the basement membrane matrix. Material with smaller chains (Mr 160000 and 140000) appeared on storage in acetic acid solutions. These results indicate that the lower molecular weight collagen in acid extracts of basement membrane arises artifactually due to an endogenous acid-active protease.

Structures of N-linked and O-linked oligosaccharides on proteoglycan monomer isolated from the Swarm rat chondrosarcoma

Monomer proteoglycans isolated from the Swarm rat chondrosarcoma contain O- and N-glycosidically linked oligosaccharides. The O-glycosidically linked ones were released from the protein core by alkaline borohydride treatment. After removal of sialic acid, the resulting oligosaccharide alditols were converted to N-trifluoroacetyl derivatives by trifluoroacetolysis. The N-trifluoroacetylated oligosaccharide alditols show shorter retention time on gas-liquid chromatography, as permethylated derivatives, than the corresponding N-acetyl derivatives. The mass spectra of these new derivatives also give more structural information and provide definitive structures. Alkaline borohydride treatment of the proteoglycans also released N-glycosidically linked oligosaccharide-peptides. These were purified and analyzed by Smith degradation, trifluoroacetolysis, and chromium trioxide oxidation. The results indicate that more than 70% of the N-glycosidically linked oligosaccharides have the following structure: (formula, see text) with the Fuc present on only about 60% of the oligosaccharides.

Cloned complementary deoxyribonucleic acid probes for untranslated messenger ribonucleic acid components of mouse sarcoma ascites cells

Mouse sarcoma ascites cells contain several abundant mRNA species that occur to a large extent in an untranslated state. RNA preparations enriched in these species were used as starting material to construct recombinant plasmids. Cloned plasmids bearing sequences homologous to four of the untranslated mRNA species were identified by translation of hybrid-selected material. These plasmids, as well as a recombinant plasmid derived from chick alpha-actin mRNA, were used as probes for the estimation of mRNA levels in polyribosomes and in small ribonucleoprotein (RNP) particles of the ascites cells. Considerable amounts of the mRNA molecules belonging to the untranslated species were present in polyribosomes as well as in mRNPs. The actin mRNA, on the other hand, was present almost exclusively in polyribosomes. The distributions obtained by the hybridization assay resembled those estimated by translation of the same RNA preparations in cell-free systems. This indicates that the mRNA molecules of a given species engaged in translation in the cells and those present as untranslated RNP particles are equally effective in cell-free translation systems.

[In vitro effect of culture fluids from neoplastic tissues on platelet aggregation. II. Experimental tumors]

We have investigated the effects on platelet function of culture media from 2 sublines of a benzopyrene-induced murine sarcoma (mFS6). Platelet aggregation was investigated according to Born's method. The cell line with greater "in vivo" invasiveness showed higher aggregating activity and higher increase on ADP-induced aggregation; these effects were inhibited by the preincubation of platelets with Aspirin (0,1 mM). These results suggest the role of platelets in metastasis formation; the possibility to inhibit pharmacologically the interactions between platelets and tumour cells could have important implications from both speculative and practical viewpoints.

Histological changes during regression induced by retinoic acid in a transplantable rat chondrosarcoma

Daily oral treatment with retinoic acid (100 mg/kg bodyweight) induced regression of a transplantable rat chondrosarcoma. In a previous biochemical investigation we have shown that the tissue breakdown is preceded by the loss of proteoglycan. The present study describes the histological changes induced by retinoic acid. A decrease in the intensity of metachromatic staining with toluidine blue was noted already after 1 day and the discoloration was almost complete after 4 days correlating with the loss of proteoglycan. Especially in the perichondrium there was a rapid proliferation of fibroblasts and monocytes. Osteoclast-like cells were missing, but tumor nodules were eroded and split up by penetrating perichondrium. After 4 days of treatment larger necrotic areas were found, initially in the center of tumor nodules only. In other areas the majority of tumorous chondroblasts survived. Tumor nodules appeared partly mesenchyma-like with some fibroblast-like cells suggesting a dedifferentiation of chondroblasts by retinoic acid. we believe that tumor regression induced by retinoic acid involved proteoglycan degradation by chondroblasts themselves and chondroclast-like activity of monocytes and fibroblasts.