Polyglactin 910/polydioxanone bicomponent totally resorbable vascular prostheses

Previous studies from our laboratory have shown that bioresorbable vascular prostheses woven from lactide-glycolide copolymers and implanted into arteries of several animal models become replaced by cellular tissues; the rate of replacement parallels the kinetics of prosthetic resorption. This study evaluates the efficacy of bicomponent resorbable prostheses as a method of augmenting resistance to dilatation during the resorption period of the more rapidly resorbed component. Bicomponent prostheses (n = 37) were woven from compound yarns containing 74% polyglactin 910 (PG910) and 26% polydioxanone (PDS) and were interposed into adult white New Zealand rabbit infrarenal aortas. Resultant prosthesis-tissue complexes were harvested after 2 weeks to 12 months. Specimens were photographed and sectioned for light, scanning, and transmission electron microscopy. Randomly selected fresh explants at 1 and 3 months and control aortic segments from the same rabbits were simultaneously perfused with culture media (37 degrees C, 100/80 mm Hg, 60 ml/min) and perfusates assayed by means of tritiated radioimmunoassay techniques for the stable prostacyclin metabolite 6-keto-PGF1 alpha before and after the addition of sodium arachidonate (10 micrograms/ml) to the media. Results showed 100% patency, no aneurysms, and stenosis in 1 of 37 prostheses (3%). PG910 was totally resorbed by 2 months and PDS by 6 months. By 1 month inner capsule thickness was 303 +/- 30 microns. In contrast to previous reports this was significantly thicker than that within 100% PDS (230 +/- 40 microns) and significantly less thick than in 100% PG910 (530 +/- 62 microns). Inner capsules in all three groups stabilized at similar thicknesses (417 to 502 microns).(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of spontaneous wheat germ agglutinin-resistant human melanoma mutants displaying remarkably different metastatic profiles in nude mice

Spontaneous wheat germ agglutinin (WGA)-resistant mutants of the MeWo human malignant melanoma line were isolated after sequential selection in increasingly toxic concentrations of WGA, without prior mutagenesis. They were isolated in an attempt to obtain "membrane glycosylation mutants" having significantly altered metastatic properties when grown in nude mice, and to characterize the biochemical (oligosaccharide) changes associated with altered metastatic behavior. The lines were assessed for their sensitivity to other lectins, membrane glycoprotein profiles, ploidy levels, and their ability to produce "artificial" metastases in nude mice after i.v. inoculation. One mutant, called 70-W, manifested a 3- to 4-fold resistance to WGA compared with wild-type cells. When inoculated into NIH Swiss nude mice, 70-W cells not only produced extensive lung colony formation but also showed an extraordinary ability to disseminate widely and extensively in a clinical fashion to many extrapulmonary sites such as the subcutis, mesentery, muscle, and brain. Moreover the majority of these metastases were deeply pigmented facilitating visual identification of very small visceral metastases. A second mutant called 3S5 was isolated and found to be highly resistant to WGA (greater than 20-fold resistance). This line was virtually devoid of metastatic ability and was found by biochemical analysis to be phenotypically similar to the class I WGA resistant non-metastatic mutants previously isolated from the highly metastatic murine tumor MDAY-D2 which are known to be deficient in sialic acid and galactose. The similarity between these and earlier results using lectin resistant mutant rodent cell lines strongly suggests that sialylated glycoconjugates contribute to the metastasis of both animal and human tumors of different tissue origin. These new spontaneously derived WGA resistant MeWo mutants should be valuable new tools for the study of human tumor progression in vivo and factors involved in metastasis, especially the contribution of oligosaccharide moieties of cell surface glycoconjugates.

Double restriction in NK cell recognition is linked to transmethylation and can be triggered by asparagine-linked oligosaccharides on tumor cells

The determinants of tumor cell susceptibility to NK cell-mediated cytolysis were analyzed in a two stage model. The binding of tumor cells to NK effectors was measured by target-effector conjugation and cold target competition in 51Cr-release assays, whereas triggering was measured by assaying phospholipid methylation in NK cells stimulated by intact targets. Representative targets could be grouped into three phenotypes based on the data. Those such as YAC 1.2 could bind and trigger NK cells whereas the mutagenized variant, YAC 6.28.8, could bind but was unable to trigger NK cells and therefore resisted lysis. The third phenotype was represented by HL-60 which could neither bind nor trigger NK cells and was therefore completely NK resistant. The oligosaccharide nature of the triggering molecules was demonstrated by showing that purified, high mannose containing, asparagine-linked oligosaccharides from tumor cell targets were potent stimulators of NK transmethylation at submicromolar levels. Tunicamycin pretreatment of target cells inhibited their triggering capacity but not their NK binding function. These results suggest a double restriction in NK specificity involving two independent but sequential stages in recognition represented in binding and triggering by asn-linked oligosaccharides on the tumor cell surface.

Beta 1-6 branching of Asn-linked oligosaccharides is directly associated with metastasis

Neoplastic transformation has been associated with a variety of structural changes in cell surface carbohydrates, most notably increased sialylation and beta 1-6-linked branching of complex-type asparagine (Asn)-linked oligosaccharides (that is, -GlcNAc beta 1-6Man alpha 1-6Man beta 1-). However, little is known about the relevant glycoproteins or how these transformation-related changes in oligosaccharide biosynthesis may affect the malignant phenotype. Here it is reported that a cell surface glycoprotein, gp 130, is a major target of increased beta 1-6-linked branching and that the expression of these oligosaccharide structures is directly related to the metastatic potential of the cells. Glycosylation mutants of a metastatic tumor cell line were selected that are deficient in both beta 1-6 GlcNAc transferase V activity and metastatic potential in situ. Moreover, induction of increased beta 1-6 branching in clones of a nonmetastatic murine mammary carcinoma correlated strongly with acquisition of metastatic potential. The results indicate that increased beta 1-6-linked branching of complex-type oligosaccharides on gp 130 may be an important feature of tumor progression related to increased metastatic potential.

Compound polyglactin 910/polypropylene small vessel prostheses

This study evaluated morphologic and functional characteristics of tissue reactions to compound prostheses of 69% absorbable polyglactin 910 (PG910) and 31% nonabsorbable polypropylene in the rabbit. Forty-two woven PG910/polypropylene prostheses (24 X 4 mm internal diameter) implanted into rabbit infrarenal aortas were harvested after 2 weeks to 12 months. Each explant was photographed and sectioned for light microscopy and transmission and scanning electron microscopy. Randomly selected explants underwent either compliance and bursting strength measurements or assays of production of prostacyclin and thromboxane metabolites by luminal surfaces of both regenerated conduits and normal control aortas in response to administered sodium arachidonate. Results showed 100% patency with no aneurysms and 2% stenoses (1 of 42 prostheses). Confluent endothelial-like cellular luminal surfaces covering oriented smooth muscle-like myofibroblasts comprised the inner capsules whose thicknesses stabilized at 1 to 2 months. Only residual polypropylene remained in the prostheses after 2 months. Compliance studies reflected a 0.65 mm (14%) change over a pressure range of 0 to 160 mm Hg. All regenerated prosthesis-tissue complexes had bursting strengths greater than the proximal perianastomotic native aortas, which burst between 600 and 2000 mm Hg. At 1 month the rate of production of 6-keto-PGF1 alpha per square millimeter of surface area of experimental segments was normal. Production of 6-keto-PGF1 alpha by experimental segments at 3 months had increased fourfold whereas thromboxane B2 (TxB2) production remained unchanged. The 6-keto-PGF1 alpha/TxB2 ratio increased from 1 to 4 months. This study demonstrates clinically efficacious morphologic, mechanical, and biochemical characteristics of PG910/polypropylene-elicited vascular prosthesis-tissue complexes.

Noninvasive cardiac monitoring

Several noninvasive techniques are currently utilized to safely assess cardiac function beyond the limits of the physical examination and EKG. These studies can accurately document rhythm and valvular abnormalities as well as the heart's ability to withstand stress. Results of these tests provide a solid base on which to decide if invasive diagnostic or therapeutic modalities may be required.

Biomaterial pretreatment with ECGF to augment endothelial cell proliferation

ECGF, a polypeptide of bovine hypothalamic derivation, is the most potent endothelial cell mitogen known, with mitogenic and chemotactic effects well demonstrated in vitro on human endothelial cells. These effects are synergized by heparin. In vivo re-endothelialization of blood-contacting biomaterials may be enhanced by bonding ECGF and heparin to prosthetic surfaces. Long woven Dacron (24 mm) and woven PDS vascular prostheses were treated first with human plasma fibronectin (10 micrograms/cm2). Porcine sodium heparin (20 micrograms/cm2) was added by means of fibronectin's heparin affinity. Pure 125I-ECGF (95% alpha, 5% beta; 1 ng/cm2) was next fixed by the heparin affinity of ECGF and followed by a second heparin layer (20 micrograms/cm2) to synergize with and stabilize ECGF. 125I-ECGF adherences were determined by scintillation counts. Attachment efficiency averaged 25%. Prostheses were interposed into rabbit aortas and harvested in triplicate from 0 to 30 days to establish in vivo washout curves. After explantation, residual 125I-ECGF was eluted from prostheses, and intact ECGF was identified by SDS gel electrophoresis. Similarly prepared but nonradioiodinated Dacron and PDS prostheses were explanted after 7 days and their ECGF eluted off for in vitro activity documentation. This ECGF retained its mitogenic properties, causing a 1000% to 1200% increase in 3H-thymidine incorporation into newly synthesized DNA in test murine LE-II cells. Fibronectin-heparin-ECGF fixation to blood-contacting biomaterials may enhance spontaneous re-endothelialization and/or hasten the confluence of transplanted endothelial cells.

Glycosphingolipids of lectin-resistant mutants of the highly metastatic mouse tumor cell line, MDAY-D2

Neutral and acidic glycolipids in MDAY-D2, a highly metastatic murine tumor cell line, were examined and compared with glycolipids of MDW4 and D33W25-1, two lectin-resistant mutants of MDAY-D2 from distinct genetic complementation classes. D33W25-1 remained highly metastatic while MDW4 cells were found to be nonmetastatic (Dennis, J. W., Donaghue, T., Florian, M., and Kerbel, R. S., Nature (Lond.), 292: 242-245, 1981 and Dennis, J. W. et al., Cancer Res., 46: 4594-4600, 1986). Glycolipid structures were identified by fast-atom bombardment mass spectrometry, methylation analysis, exoglycosidase treatment, and immunostaining. The metastatic MDAY-D2 was found to contain GM3, GM2, IV3GalNAc-GM1b, and high levels of GM1a, GM1b, and GD1a. MDW4 showed a 3-fold decrease in total ganglioside content compared to MDAY-D2 and a corresponding increase in the precursor, glucosylceramide. MDW4 was deficient in GM1 and accumulated GM2 and NeuNG-GM2, indicating a lack of gangliosides having NeuNAc alpha 2-3Gal beta 1-3 terminal sequence. Neosynthesis of GD3 was also observed in MDW4. The metastatic mutant D33W25-1 had a similar pattern of gangliosides as that found in MDAY-D2 cells with N-glycolyl rather than N-acetyl neuraminic acid. These results suggest that the metastatic property of these cell lines may be related to the level of ganglioside, and that the substitution of N-glycolyl for N-acetyl neuraminic acid does not reduce metastatic capacity.

Tumor cell surface carbohydrate and the metastatic phenotype

The synthesis and expression of cell surface carbohydrates is a developmentally regulated process that appears to affect a number of cell-cell interactions. To determine whether specific oligosaccharide structures present on highly malignant cells are required for expression of the metastatic phenotype, we have isolated lectin resistant tumor cell mutants with defects in the biosynthesis of oligosaccharides. The mutants selected from the highly aggressive lymphoreticular-like tumor line MDAY-D2 were grouped into genetic complementation classes, compared for metastatic ability and for changes in cell surface glycoconjugates. The Asn-linked oligosaccharides and glycolipids of class 1 mutants were deficient in both sialic acid and galactose and the cells showed a greatly attenuated metastatic phenotype compared to the parental cells. A revertant of the class 1 mutation selected in vitro regained the wild type glycoconjugate profile and the highly metastatic phenotype indicating a direct association between the mutation and the loss of metastatic potential. Class 2 mutants remained highly metastatic and had Asn-linked oligosaccharide structures very similar to those found in the wild type cells with N-glycolylneuraminic acid rather than the N-acetylneuraminic acid. Swainsonine, an inhibitor of golgi alpha-mannosidase II, blocks the synthesis of complex-type Asn-linked oligosaccharides resulting in the expression of hybrid-type oligosaccharides at the cell surface and the cells display a lectin resistant phenotype. Although swainsonine inhibited neither tumor cell growth in vitro nor solid tumor growth in situ, the drug dramatically reduced the incidence of lung colonies after i.v. inoculation of both MDAY-D2 and B16F10 melanoma cells. These results, taken together, indicate that certain sialylated Asn-linked oligosaccharides found on metastatic tumor cells are required for expression of the metastatic phenotype.

Asn-linked oligosaccharides in lectin-resistant tumor-cell mutants with varying metastatic potential

MDW4, a wheat germ agglutinin-resistant mutant of the metastatic murine tumor MDAY D2 has previously been shown to be poorly metastatic when injected intravenously and non-metastatic when injected subcutaneously into syngeneic mice. W4EB8, a Bandeiraea simplicifolia (BSII) lectin-selected subline of MDW4 has previously been shown to be intermediate between that of MDAY-D2 and MDW4 cell for sensitivity to lectin and metastatic phenotype when injected intravenously into mice. The Asn-linked oligosaccharides from MDAY-D2, MDW4 and W4EB8 cells were released enzymatically with peptide N-glycosidase, reduced with tritiated sodium borohydride and fractionated by Concanavalin-A--Sepharose affinity chromatography and high-performance liquid chromatography (HPLC). Structures of the major fractions were determined by a combination of glycosidase digestion and sizing, gas-liquid chromatography/mass spectrometry and by proton nuclear magnetic resonance. Wild-type and mutant cells processed high-mannose-type structures to biantennary (GlcNAc)2(Man)3(GlcNAc)2. In MDAY-D2 cells this structure was processed further to sialylated tetra-antennary complex with polylactosamine-containing antennae terminating in either sialic acid or alpha 1-3-linked galactose. MDW4 cells had four or five times more (GlcNAc)2(Man)3(GlcNAc)2 than MDAY-D2 cells and a major component of tri-antennary (GlcNAc)3(Man)3(GlcNAc)2 (i.e. 2,2,6-substituted tri-mannosyl core) that was not found in wild-type cells. The partial revertant, W4EB8 had intermediate levels of mutant (GlcNAc)3(Man)3(GlcNAc)2 and sialylated complex-type carbohydrates. The results indicate that a shift in expression from incomplete complex type to sialylated tri/tetra-antennary complex-type carbohydrates in tumor cell may enhance the metastatic potential of tumor cells in the experimental metastasis assay. In addition, somatic cell hybridization analysis indicated that the defect in MDW4 cells was identical to that of the Chinese hamster ovary mutant Lec8: a deficiency in UDP-galactose transport into the golgi.

Effects of swainsonine and polyinosinic:polycytidylic acid on murine tumor cell growth and metastasis

Increased sialylation and branching of asparagine-linked oligosaccharides have recently been associated with both neoplastic transformation and the metastatic phenotype. Swainsonine, an inhibitor of Golgi alpha-mannosidase II blocks the synthesis of sialylated tri- and tetraantennary asparagine-linked oligosaccharides and results in the expression of hybrid-type oligosaccharides at the cell surface. Both the lymphoid tumor line MDAY-D2 and B16F10 melanoma cells were less metastatic when grown in swainsonine (0.3 micrograms/ml) for 48 h prior to injection of the cells into the lateral tail veins of mice. The addition of swainsonine (2.5 micrograms/ml) to the drinking water of the mice further reduced the incidence of lung colonization by B16F10 melanoma cells. MDAY-D2 tumors removed from mice on swainsonine-supplemented drinking water showed a loss of leukoagglutinin-binding complex-type oligosaccharides similar to that of tumor cells cultured in medium containing swainsonine. The growth rate of s.c. MDAY-D2 tumors was not reduced by the addition of swainsonine to the drinking water of the host; however, when mice were given two i.p. injections of the interferon-inducing agent polyinosinic:polycytidylic acid in addition to swainsonine, the primary tumor grew at a reduced rate compared to either treatment alone. Swainsonine alone did not inhibit tumor cell growth in vitro; however, the drug enhanced the antiproliferative effect of interferon. The survival time of mice bearing established MDAY-D2 metastases was extended by treating the animals with swainsonine and polyinosinic:polycytidylic acid; however, the number of long-term survival was unchanged. Swainsonine-treated tumor cells appeared to be compromised in two ways: reduced organ colonization potential; and drug-treated MDAY-D2 cells were more sensitive to the antiproliferative effects of interferon in vitro and in vivo.

Co-reversion of a lectin-resistant mutation and non-metastatic phenotype in murine tumor cells

Three independent isolates, one obtained spontaneously and the others obtained after in vitro mutagenesis, of a WGA-resistant mutation were compared to the highly metastatic parental murine cell line MDAY-D2 for alterations in plasma membrane glycoproteins and changes in metastatic behavior. The mutants were non-metastatic from an s.c. site of injection and poor organ-colonizers when administered i.v. Each of the mutant lines had the same lesion in N-linked oligosaccharide structure, which rendered the cells hypersensitive to the N-acetylglucosamine-binding lectin BSII in vitro. The phenotypic similarities between the 3 WGA-resistant isolates indicated that the mutation was directly related to the attenuated malignant phenotype. Direct confirmation was obtained by the isolation of a BSII-resistant clone of the mutant cells that co-reverted for lectin-sensitivity, lectin binding glycoproteins and malignant aggressiveness. The results indicate a direct relationship between malignant behavior and cell-surface oligosaccharide structure.

Different metastatic phenotypes in two genetic classes of wheat germ agglutinin-resistant tumor cell mutants

Spontaneous wheat germ agglutinin (WGA)-resistant mutants of the highly metastatic tumor line MDAY-D2 have been grouped into two classes by (a) genetic complimentation in somatic cell hybrids, (b) lectin binding to plasma membrane glycoproteins, and (c) metastatic phenotypes. Class 1 mutants were recessive in somatic cell hybrids between mutant and wild type cells; they were poorly metastatic in an organ colonization assay and nonmetastatic in the spontaneous metastasis assay. The class 1 mutants had prematurely truncated asparagine-linked oligosaccharides terminating in N-acetylglucosamine, rather than the sialylated N-acetyllactosamine found in wild type cells. The class 2 mutation was dominant in somatic cell hybrids between mutant and wild type cells. The cell lines retained the highly metastatic phenotype in both organ colonization and spontaneous metastasis assays. The plasma membrane glycoproteins of the class 2 mutants were similar to those of MDAY-D2 cells including the presence of sialylated polylactosamine-containing antennae in the asparagine-linked oligosaccharide. However, the cells synthesized N-glycolylneuraminic acid rather than the N-acetylneuraminic acid, a form of sialic acid that does not bind WGA. Previous studies by other investigators have shown that lectin-resistant mutants selected in WGA were often less metastatic than their respective wild type cell. Our results demonstrate that the loss of metastatic potential in WGA-resistant mutants of MDAY-D2 depends on the phenotypic class of the isolates and their characteristic changes in glycoconjugate structure.

Anastomotic pseudoaneurysms. A continuing late complication of vascular reconstructive procedures

Anastomotic pseudoaneurysms continue to be a late complication of vascular grafting procedures. We reviewed the records of 48 patients who presented with 65 abdominal or lower extremity anastomotic pseudoaneurysms during 1977 to 1985. The interval between the original operation and the development of a pseudoaneurysm was 6.2 years (range, 2.5 months to 19 years). Most patients underwent resection of the involved segment of graft and artery with placement of an interposition graft. Graft patency was 97.5% during a mean follow-up of 2.4 years (range, two months to five years), and one operative mortality occurred. Four patients had emergency procedures; one patient underwent reconstruction, and three others underwent resection of the pseudoaneurysms alone. Two of those patients died, and the one survivor eventually required a high amputation. We recommend aggressive diagnosis and surgical reconstruction in these patients usually by interposition grafts or anastomotic revisions because the short- and long-term results are excellent. Morbidity and mortality are greatly increased when these procedures are done emergently.

Recognition of asparagine-linked oligosaccharides on murine tumor cells by natural killer cells

MDW4, a wheat germ agglutinin resistant mutant of the murine tumor line MDAY-D2, expresses abnormal asparagine-linked oligosaccharides, is less metastatic when injected intravenously, and is hypersensitive to natural killer (NK) lysis in vitro. To determine whether these phenotypes may be related, variants of the YAC-1 lymphoma and a YAC-1 X MDAY-D2 hybrid line were compared for sensitivity to four different lectins and to NK cell lysis in vitro. A relationship between sensitivity to concanavalin A (Con A) and NK cell lysis in vitro was observed. Although no single plasma membrane glycoprotein separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with 125I-labeled Con A correlated with NK and Con A sensitivities of the cell lines, a relationship between these phenotypes and the collective 125I-Con A staining intensity on the gels was apparent. In a more direct test of carbohydrate recognition by NK cells, specific glycopeptide structures isolated from tumor cells and added to the NK cell assay in microM quantities were found to inhibit tumor cell lysis. Thus, a subset of asparagine-linked oligosaccharides, including high mannose and some incomplete complex structures on a number of cell surface glycoproteins, appears to be recognized as part of the target structures for NK cell lysis. The administration of polyinosinic:polycytidylic acid stimulated splenic NK activity in vivo but had no effect on the growth of the NK-resistant MDAY-D2 cells. However, the low tumorigenicity of MDW4 cells injected intravenously was reduced further by pretreating the mice with polyinosinic:polycytidylic acid, which indicated a role for NK cells in the elimination of circulating tumor cells expressing high mannose and/or incomplete complex asparagine-linked oligosaccharides.

An exoglycosidase-sensitive triggering site on NK cells which is coupled to transmethylation of membrane phospholipids

Glycosidic enzymes were used as probes to analyze the mechanism of NK cell-mediated cytotoxicity. Pretreatment of nylon wool-enriched CBA/J spleen cells, a murine NK clone, or human peripheral blood lymphocytes (PBL) with alpha-mannosidase, an exoglycosidase, led to a marked dose-dependent inhibition of NK lytic activity against YAC-1.2 or K562 tumor cells. Maximal inhibition occurred after a 60-min pretreatment of murine effectors at 37 degrees C, and the kinetics of NK inhibition by alpha-mannosidase was similar to the reported kinetics for enzymatic activity. Released hexose was detected chemically in the supernatant of mouse spleen cells treated with NK inhibitory dose of alpha-mannosidase, and inactivation of enzymatic function with EDTA reversed the NK inhibitory effect. These results suggest that alpha-mannosidase inhibited NK function by virtue of its enzymatic action. Culture of human PBL for 20-hr after treatment with this enzyme led to a greater than 70% recovery in NK lytic function. Recovery was blocked by incorporating tunicamycin, a glycosylation inhibitor of asparagine-linked glycoproteins, into the culture medium. These results suggest that the alpha-mannosidase-sensitive site may be de novo synthesized glycoprotein. Neuraminidase, beta-galactosidase, endo-beta-N-acetylglucosaminidase-D and H, and peptide-N-glycosidase treatments did not inhibit human NK cell lysis of K562 cells. Pretreatment of nylon wool-enriched CBA/J spleen cells or Percoll-enriched human LGL with alpha-mannosidase did not influence their capacity to bind YAC 1.2 target cells or K562 target cells, respectively, Ca++ pulse experiments revealed that the alpha-mannosidase-sensitive site on the NK cells was involved after target-effector binding but before the Ca++ influx. Pretreatment of effector cells with this enzyme which normally occurs after effector-target cell interaction. These results suggest that the phospholipid methylation reaction is coupled to the alpha-mannosidase-sensitive site on the NK cells. By analogy to other physiologic systems, such as histamine release in mast cells, the triggering of phospholipid methylation in the NK cells may serve as a mechanism for signal transduction across the plasma membrane.

An exoglycosidase-sensitive triggering site on NK cells which is coupled to transmethylation of membrane phospholipids

Glycosidic enzymes were used as probes to analyze the mechanism of NK cell-mediated cytotoxicity. Pretreatment of nylon wool-enriched CBA/J spleen cells, a murine NK clone, or human peripheral blood lymphocytes (PBL) with alpha-mannosidase, an exoglycosidase, led to a marked dose-dependent inhibition of NK lytic activity against YAC-1.2 or K562 tumor cells. Maximal inhibition occurred after a 60-min pretreatment of murine effectors at 37 degrees C, and the kinetics of NK inhibition by alpha-mannosidase was similar to the reported kinetics for enzymatic activity. Released hexose was detected chemically in the supernatant of mouse spleen cells treated with NK inhibitory dose of alpha-mannosidase, and inactivation of enzymatic function with EDTA reversed the NK inhibitory effect. These results suggest that alpha-mannosidase inhibited NK function by virtue of its enzymatic action. Culture of human PBL for 20-hr after treatment with this enzyme led to a greater than 70% recovery in NK lytic function. Recovery was blocked by incorporating tunicamycin, a glycosylation inhibitor of asparagine-linked glycoproteins, into the culture medium. These results suggest that the alpha-mannosidase-sensitive site may be de novo synthesized glycoprotein. Neuraminidase, beta-galactosidase, endo-beta-N-acetylglucosaminidase-D and H, and peptide-N-glycosidase treatments did not inhibit human NK cell lysis of K562 cells. Pretreatment of nylon wool-enriched CBA/J spleen cells or Percoll-enriched human LGL with alpha-mannosidase did not influence their capacity to bind YAC 1.2 target cells or K562 target cells, respectively, Ca++ pulse experiments revealed that the alpha-mannosidase-sensitive site on the NK cells was involved after target-effector binding but before the Ca++ influx. Pretreatment of effector cells with this enzyme which normally occurs after effector-target cell interaction. These results suggest that the phospholipid methylation reaction is coupled to the alpha-mannosidase-sensitive site on the NK cells. By analogy to other physiologic systems, such as histamine release in mast cells, the triggering of phospholipid methylation in the NK cells may serve as a mechanism for signal transduction across the plasma membrane.

Partial reversion of the metastatic phenotype in a wheat germ agglutinin-resistant mutant of the murine tumor cell line MDAY-D2 selected with Bandeiraea simplicifolia seed lectin

MDW4, a wheat germ agglutinin (WGA)-resistant (WGAr) mutant of the metastatic murine tumor cell line MDAY-D2, was previously shown to be nonmetastatic in the syngeneic DBA/2 host. A substantial portion of the asparagine (Asn)-linked carbohydrate in MDW4 terminated in N-acetylglucosamine (GlcNAc) and appeared to be a premature truncation product of the sialylated poly-N-acetyllactosamine-containing complex found in MDAY-D2 cells. This lesion in carbohydrate structure has been shown to contribute to the more adhesive behavior of MDW4 cells on laminin, fibronectin, and type IV collagen and to the increased sensitivity of MDW4 to natural killer (NK) cell lysis in vitro. For further characterization of the relationship between Asn-linked carbohydrate structures, cell adhesion, NK cell sensitivity, and metastasis, mutants of MDW4 were selected for resistance to the GlcNAc-binding lectin from Bandeiraea simplicifolia seeds (BSII). Three independently selected BSII-resistant (BSIIr) mutants of MDW4 chosen for further study had a lectin resistance phenotype intermediate between that of MDAY-D2 and that of MDW4. Plasma membrane glycoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with iodinated WGA, BSII, and leukoagglutinin also indicated an intermediate phenotype, with the presence of both GlcNAc-terminating structures and sialylated complex. Compared to MDW4, the BSIIr mutants of MDW4 showed a return to the more malignant phenotype of MDAY-D2 when injected iv. The double mutants were less sensitive to NK cell lysis in vitro and to the in vivo effects of the NK cell boosting agent polyinosinic-polycytidylic acid. The double mutants retained the ability to attach to fibronectin, laminin, and collagen type IV in vitro, a property that may have contributed to their low malignancy when the cells were injected sc. MDW4 cells have been shown to fuse at low frequency with host-derived bone marrow cells at the sc site of injection, thereby acquiring the wild-type lectin resistance and metastatic phenotypes. The same process appears to occur in mice given an injection of the double mutants. The results suggest that the WGA-binding oligosaccharides found in MDAY-D2 and the BSIIr mutants of MDW4 enhance the malignant phenotype of the cells in the experimental metastasis assay.

Adoptive immune therapy in mice bearing poorly immunogenic metastases, using T lymphocytes stimulated in vitro against highly immunogenic mutant sublines

MDW3, a highly immunogenic and non-tumorigenic (tum-) mutant of the poorly immunogenic metastatic murine tumor called MDAY-D2, has been employed in an immune therapy scheme for the treatment of widespread established visceral MDAY-D2 metastases in syngeneic mice. MDW3 was selected from a mutagenized population of MDAY-D2 cells for the ability to grow in the presence of toxic concentrations of wheat-germ agglutinin (WGA) in vitro. The mutant expresses a common tumor-associated antigen (TAA) present on MDAY-D2 as well as a new antigen whose presence enhances the anti-TAA cell-mediated immune response in vivo and in mixed lymphocyte tumor cultures (MLTC) in vitro. For immune therapy, spleen cells from DBA/2 mice which had rejected an inoculum of MDW3 cells were restimulated in MLTC and injected i.v. into MDAY-D2 tumor-bearing mice. Two protocols were used. In the first, mice were given an i.v. injection of 10(3) MDAY-D2 cells ("artificial metastasis") and subsequently treated with 400 R whole-body irradiation and MDW3-stimulated T cells. Such mice had a 75% long-term survival rate, whereas 400 R alone, or no treatment, resulted in 25% and 0% long-term survivors, respectively. In the second protocol, treatment of mice bearing a 12-day-old subcutaneous MDAY-D2 tumor by surgical removal of the solid tumor, 400 R whole-body irradiation, and systemic administration of MDW3-stimulated spleen cells, resulted in a 75-100% survival rate, whereas omitting any part of the treatment resulted in 0-50% survival rates. The treatment increased splenic anti-TAA CTL activity, and the mice acquired immunity against the new antigen on MDW3, suggesting that the injected lymphocytes were proliferating in the host. The optimal combination of resection, whole-body irradiation and passive infusion of MDW3-stimulated spleen cells was ineffective when used on mice bearing a tumor-antigen-loss variant of MDAY-D2, suggesting that success of our immune therapy protocol required specific recognition of the tumor-associated antigen of MDAY-D2.

Asparagine-linked oligosaccharides in murine tumor cells: comparison of a WGA-resistant (WGAr) nonmetastatic mutant and a related WGA-sensitive (WGAs) metastatic line

MDW40, a wheat germ agglutinin-resistant (WGAr) mutant of the highly metastatic tumor cell line called MDAY-D2, is restricted to local growth at the subcutaneous site of inoculation. The WGAr tumor cells acquire metastatic ability by fusing spontaneously with a normal host cell followed by chromosome segregation, a process accompanied by reversion of the WGAr phenotype (i.e., WGAs). Since lectin-resistant mutant cell lines often have oligosaccharide alterations that may affect membrane function and consequently metastatic capacity, we compared the major Asn-linked glycopeptides in WGAr and WGAs cell lines. [2-3H]mannose-labeled glycopeptides were separated into four fractions on a DEAE-cellulose column and then further fractionated on a concanavalin A-Sepharose column. Glycopeptide structures were determined by: (a) sequential exoglycosidase digestion followed by chromatography on lectin/agarose and Bio-Gel P-4 columns and (b) proton nuclear magnetic resonance analysis. The metastatic WGAs cells had a sialylated poly-N-acetyllactosamine-containing glycopeptide which was absent in the nonmetastatic mutant cell line. Unique to the mutant was a neutral triantennary class of glycopeptide lacking sialic acid and galactose; the WGAr lesion therefore appeared to be a premature truncation of the antennae of the poly-N-acetyllactosamine-containing glycopeptide found in the WGAs cells. High mannose glycopeptides containing five to nine mannose residues constituted a major class in both WGAr and WGAs cells. Lysates of both wild-type and mutant cells had similar levels of galactosyltransferase activity capable of adding galactose to the N-acetylglucosamine-terminated glycopeptide isolated from mutant cells; the basis of the WGAr lesion remains to be determined.

Identification of asparagine-linked oligosaccharides involved in tumor cell adhesion to laminin and type IV collagen

MDW4, a wheat germ agglutinin-resistant nonmetastatic mutant of the highly metastatic murine tumor cell line called MDAY-D2 has previously been shown to attach to fibronectin and type IV collagen, whereas MDAY-D2 and phenotypic revertants of MDW4 attached poorly to these substrates. The increased adhesiveness of the mutant cells appeared to be closely related to a lesion in cell surface carbohydrate structures. In an effort to identify the carbohydrates involved in cell attachment, glycopeptides isolated from mutant and wild-type cells as well as from purified glycoproteins were tested for their ability to inhibit the attachment of MDW4 cells to plastic surfaces coated with fibronectin, laminin, or type IV collagen. The addition of mannose-terminating glycopeptide to the adhesion assay inhibited MDW4 cell attachment to type IV collagen. In contrast, a sialylated poly N-acetyllactosamine-containing glycopeptide, isolated from wheat germ agglutinin-sensitive MDAY-D2 cells but absent in MDW4 cells, inhibited MDW4 attachment to laminin. None of the glycopeptides used in this study inhibited attachment of MDW4 cells to fibronectin-coated plastic. Peptide N-glycosidase treatment of the cells to remove surface asparagine-linked oligosaccharides inhibited MDW4 adhesion to type IV collagen, but not to laminin, and the same treatment of the wheat germ agglutinin-sensitive cells enhanced attachment to laminin. Tumor cell attachment to, and detachment from, the sublaminal matrix protein laminin and type IV collagen are thought to be important events in the metastatic process. Our results indicate that tumor cell attachment to these proteins may be partially modulated by the expression of specific oligosaccharide structures associated with the cell surface.