Asparagine-linked oligosaccharides associated with metastatic cancer

Malignant transformation and tumor progression are often accompanied by structural changes in the carbohydrate components of glycoproteins and glycolipids. Studies with tumor cell glycosylation mutants and specific inhibitors of glycosylation indicate that expression of sialylated and beta (1-6) branched asparagine (Asn)-linked oligosaccharides are required for tumor cell invasion and metastasis. The initiation of the beta (1-6) antenna appears to be oncodevelopmentally regulated and may be associated with the aberrant expression of blood group and embryonic carbohydrate sequences in Asn-linked oligosaccharides of tumors. Although the function of these oligosaccharides in the metastatic process remains unclear, there is some evidence that expression of these structures on certain cell-surface glycoproteins may reduce tumor cell adhesion to extracellular matrix. These observations suggest that low-toxicity drugs that inhibit the biosynthesis of these structures may be useful in the treatment of metastatic cancers.

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.

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.

Membrane-associated alterations detected in poorly tumorigenic lectin-resistant variant sublines of a highly malignant and metastatic murine tumor

A number of wheat germ agglutinin-resistant (WGAR) variants of a highly malignant and metastatic mouse tumor (called MDAY-D2) were selected. Two of these, MDW1 and MDW3, were poorly tumorigenic in the normal DBA/2 host but grew well in highly immunosuppressed recipients. In contrast, MDAY-D2, MDW4, and MDW5 were all highly tumorigenic in both normal and immunosuppressed hosts. Analysis of the WGAR variants by cytotoxic T-cell testing did not reveal any evidence for the acquisition of new tumor antigens by the MDW1 or MDW3 variant sublines, although they provoked a significantly stronger T killer cell response than did MDAY-D2, MDW4, or MDW5. Further studies indicated that the rate of tumor cell surface shedding in vitro correlated strongly with relative tumorigenicity and, furthermore, that changes in the cytoskeletal structure of MDW1 and MDW3 may have contributed to their reduced rate of shedding.

TMOD-18. DIRECT IN VIVO CRISPR SCREEN IDENTIFIES COOPERATING TUMOR SUPPRESSORS THAT DRIVE PROGRESSION OF IDH1-MUTANT LOW-GRADE GLIOMA TO AGGRESSIVE GLIOBLASTOMA

Low-grade glioma (LGG) are generally slowly growing brain cancers, that frequently undergo malignant progression to aggressive, secondary glioblastoma with a dismal prognosis. By combining genetically engineered Idh1-mutant mice with in vivo CRISPR gene editing we generated a mouse model faithfully recapitulating the founder mutations of LGG. Clonal activation of the neomorphic Idh1 R132H mutation cooperates with Trp53 and Atrx mutations to trigger development of brain tumors but only with ~30% penetrance and very long latency. To elucidate the molecular mechanisms underlying the malignant progression of IDH1-mutant LGG, we devised and deployed a direct in vivo CRISPR screen targeting genes commonly mutated in human IDH-mutant secondary glioblastoma. Stereotaxic delivery of a lentiviral sgRNA library targeting the mouse orthologs of these genes into the brain of Idh1 R132H ;Trp53;Atrx;Cas9 and control Idh1 wt ;Trp53;Atrx;Cas9 compound mutant mice resulted in rapid formation of tumors that recapitulate human Idh1-mutant glioblastoma. Deconvoluting the screen showed that PI3K pathway members Pten and Pik3ca as well as Notch1, Smarca4 and Fat1 are preferentially enriched in Idh1 R132H-tumors, while Rb1 and NF2 were enriched in Idh1 wt tumors. Co-mutation analysis further identified additional co-occurring driver combinations such as Bcor-Met, Olig2-Met, Olig2-Med12 or Bcor-Olig2. We validated the tumor suppressive function of Notch1 and Pten using conventional floxed knock-out alleles and found that Notch1 functions in a haploinsufficient manner. Interestingly, Idh1 R132H did not alter tumor latency or pathology in a high grade p53;Pten;Rb1 mutant background, indicating that the neomorphic IDH-mutations can drive low but not high grade glioma development. Our study provides a functional landscape of gliomagenesis suppressors in vivo.

Branching beta 1-6N-acetylglucosaminetransferases and polylactosamine expression in mouse F9 teratocarcinoma cells and differentiated counterparts

beta-All-trans-retinoic acid (RA)-induced endodermal differentiation of mouse F9 teratocarcinoma cells is accompanied by changes in glycoprotein glycosylation, including expression of i antigen (i.e. polylactosamine) and leukophytohemagglutinin-reactive oligosaccharides (i.e. -GlcNAc beta 1-6Man alpha 1-6-branched N-linked). We have used the F9 teratocarcinoma cells as a model to study developmental regulation of glycosyltransferase activities which are responsible for the biosynthesis of beta 1-6GlcNAc-branched N- and O-linked oligosaccharides and polylactosamine. Growth of F9 cells in the presence of 10(-6) M RA for 4 days increased core 2 GlcNAc transferase and GlcNAc transferase V activities by 13- and 6-fold, respectively, whereas the activities of GlcNAc transferase I, beta 1-3GlcNAc transferase (i), beta 1-4Gal transferase, and beta 1-3Gal transferase increased 2-4-fold. Induction of glycosyltransferase activities by RA was dose-dependent and showed a biphasic response with approximately half of the increase observed 3 days after RA treatment and the remainder occurred by day 4. PYS-2, a parietal endoderm cell line, showed levels of glycosyltransferase activities similar to those of RA-treated F9 cells. Glycosyltransferase activities in the RA-resistant F9 cell line (RA-3-10) were low and showed only a small induction by RA. These observations suggest that differentiation of F9 cells is closely associated with induction of multiple glycosyltransferase activities, with most pronounced increases in GlcNAc transferase V and 2',5'-tetradenylate (core 2) GlcNAc transferase. The increase in GlcNAc transferase V was also reflected by the 4-6-fold increase in the binding of 125I-leukophytohemagglutinin to several cellular glycoproteins, which occurred after 3 days of RA treatment. The endo-beta-galactosidase-sensitive polylactosamine content of membrane glycoproteins and, in particular, the LAMP-1 glycoprotein was markedly increased after RA treatment of F9 cells. Consistent with these observations, fucosylated polylactosamine (i.e. dimeric Lex) was also increased in RA-treated cells. Analysis of the aryl oligosaccharides produced by F9 cells cultured in the presence of aryl alpha-D-GalNAc showed that RA treatment enhanced the synthesis of disialyl core 2 O-linked oligosaccharides and increased the polylactosamine content of the aryl oligosaccharides by > 20-fold. The results suggest that differentiation of F9 cells into endoderm is closely associated with increased GlcNAc transferase V and core 2 GlcNAc transferase activities, enzymes which control the level of beta 1-6GlcNAc-branched N- and O-linked oligosaccharides, the preferred substrates for polylactosamine addition.

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.

New perspectives on the management of penetrating trauma in proximity to major limb arteries

Current management of penetrating injuries in the proximity of major extremity arteries with no evidence of vascular trauma remains controversial. A total of 318 such injuries in 254 patients were evaluated prospectively to clarify the appropriate timing and role of arteriography, as well as the natural history of these injuries. The arteries at risk were: axillary, 47; brachial, 57; superficial femoral, 176; and popliteal, 38. No deaths occurred, and no morbidity resulted from arteriographic delay of 6 to 24 hours after injury. Of the 48 arteriographic abnormalities detected, 16 involved noncritical branch vessels. There were 32 injuries to major arteries (10.0%), including localized narrowing (n = 13), intimal flap (n = 12), false aneurysm (n = 6), and arteriovenous fistula (n = 1). Shotgun wounds led to a greater arterial injury rate (3/17; 17.6%) than did gunshot wounds (24/247; 9.7%) or stab wounds (5/54; 9.3%). At the surgeon's discretion, three injuries underwent immediate exploration (one negative), whereas the remaining 29 vessel injuries were followed up nonoperatively by repeat arteriography (n = 22) or clinical examination (n = 7), for a mean interval of 2.8 months. Fifteen abnormalities resolved, 10 improved or remained unchanged, and 4 worsened. The four lesions (13.7%) that worsened (two shotgun and two axillary artery injuries) were identified within 3 months of injury and repaired surgically with no morbidity. In conclusion, only 6 operations were required out of 3218 potential injuries (1.8%), suggesting that routine arteriography is not a cost-effective means of evaluating these injuries.(ABSTRACT TRUNCATED AT 250 WORDS)

Superiority of end-diastolic volume and ejection fraction measurements over wedge pressures in evaluating cardiac function during aortic reconstruction

Marked changes occur in cardiac function during aortic reconstruction. Numerous factors (primarily compliance changes) limit the currently used pressure-based pulmonary artery catheters' ability to reflect these changes accurately. A new pulmonary artery catheter was used in 26 patients undergoing aortic reconstruction (7 patients with abdominal aortic aneurysms and 19 with occlusive disease) that directly measures right ventricular (RV) volumes and ejection fractions. The extent of coronary artery disease (CAD) was evaluated before surgery, and the patients were divided into three classes. The greatest changes in cardiac function were noted immediately after aortic cross-clamping. Cardiac output significantly decreased in patients with mild or moderate CAD (p less than 0.01 and p less than 0.001) but not in patients with no CAD (p less than 0.5). This correlated well with RV end-diastolic volume (RV-EDV) and stroke volume (RV-SV) measurements in the groups with mild (p less than 0.05) and moderate CAD (p less than 0.01) but not in the group with no CAD (p greater than 0.5). Wedge pressure showed poor correlation, with no significant change noted in any group (p greater than 0.5). Measurements taken later in the procedure documented a significant trend toward baseline in mild and moderate groups. At the opening of the second limb of the graft, the compensated values (CO, RV-EDV, and RV-SV) did not change significantly in the groups with mild and no CAD (p greater than 0.2) but approached significance in the group with moderate CAD (p less than 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)

SLC3A2 N-glycosylation and Golgi remodeling regulate SLC7A amino acid exchangers and stress mitigation

Proteostasis requires oxidative metabolism (ATP) and mitigation of the associated damage by glutathione, in an increasingly dysfunctional relationship with aging. SLC3A2 (4F2hc, CD98) plays a role as a disulfide-linked adaptor to the SLC7A5 and SLC7A11 exchangers which import essential amino acids and cystine while exporting Gln and Glu, respectively. The positions of N-glycosylation sites on SLC3A2 have evolved with the emergence of primates, presumably in synchrony with metabolism. Herein, we report that each of the four sites in SLC3A2 has distinct profiles of Golgi-modified N-glycans. N-glycans at the primate-derived site N381 stabilized SLC3A2 in the galectin-3 lattice against coated-pit endocytosis, while N365, the site nearest the membrane promoted glycolipid-galectin-3 (GL-Lect)-driven endocytosis. Our results indicate that surface retention and endocytosis are precisely balanced by the number, position, and remodeling of N-glycans on SLC3A2. Furthermore, proteomics and functional assays revealed an N-glycan-dependent clustering of the SLC3A2∗SLC7A5 heterodimer with amino-acid/Na+ symporters (SLC1A4, SLC1A5) that balances branched-chain amino acids and Gln levels, at the expense of ATP to maintain the Na+/K+ gradient. In replete conditions, SLC3A2 interactions require Golgi-modified N-glycans at N365D and N381D, whereas reducing N-glycosylation in the endoplasmic reticulum by fluvastatin treatment promoted the recruitment of CD44 and transporters needed to mitigate stress. Thus, SLC3A2 N-glycosylation and Golgi remodeling of the N-glycans have distinct roles in amino acids import for growth, maintenance, and metabolic stresses.

Oncodevelopmental expression of--GlcNAc beta 1-6Man alpha 1-6Man beta 1--branched asparagine-linked oligosaccharides in murine tissues and human breast carcinomas

Increased--GlcNAc beta 1-6Man alpha 1-6Man beta--branching in asparagine-linked oligosaccharides has been observed in murine and human tumor cells and has recently been linked to enhanced metastatic potential in experimental tumor models. Leukoagglutinin (L-PHA) requires the beta 1-6-linked lactosamine antenna (beta 1-6 branch) for high affinity binding and was used in this study to quantitate these structures on glycoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Normal rodent tissues and cell lines were used to standardize the experimental conditions required to quantitate beta 1-6-branched oligosaccharide structures and the glycosyltransferase activity which initiates the synthesis of the antenna, beta 1-6 N-acetylglucosamine (GlcNAc)-transferase V (EC 2.4.1.155). Secondly, the levels of L-PHA-reactive oligosaccharide were compared in a series of benign and malignant human breast biopsies. Normal human breast tissue and benign lesions showed low expression but 50% of the primary malignancies examined showed significantly elevated L-PHA reactivity. GlcNAc transferase V activities in the human breast carcinomas and in normal murine tissues correlated with the levels of L-PHA reactive oligosaccharide in the tissues. GlcNAc transferase V showed similar ranges of activities, differing by approximately 5-fold between high and low expressing mouse tissues; fibroblasts with and without an activated H-ras oncogene; and low and high expressing human breast carcinomas. The results show that beta 1-6 branching in asparagine-linked oligosaccharides is dependent on tissue-specific regulation of GlcNAc transferase V activity. Secondly, a subset of human breast malignancies showed elevated levels of beta 1-6-branched oligosaccharides compared to benign samples, suggesting that further studies are warranted to determine whether the presence of these oligosaccharides is associated with metastatic disease and reduced patient survival time.

N-linked oligosaccharide processing and tumor cell biology

A variety of alterations in carbohydrate structure have been observed in cancer cells. Most are carbohydrate sequences normally found in other adult or embryonic tissues and their expression in cancer cells appears to reflect a change in the differentiated state of transformed cells. The expression of branched and sialylated complex-type N-linked oligosaccharides in malignant tumor cells appears to be directly associated with metastatic potential. Inhibition of N-linked oligosaccharide processing in malignant cells is associated with increased susceptibility to natural immunity, increased cell adhesion to extracellular matrix and decreased tumor cell invasion in vitro. There is also growing evidence that branched complex-type oligosaccharides participate in organ retention of blood-borne tumor cells by acting as ligands for endothelial cell lectins. These observations suggest that inhibitors of N-linked oligosaccharide processing may be useful anti-cancer agents.

Autocrine and paracrine regulation of tissue inhibitor of metalloproteinases, transin, and urokinase gene expression in metastatic and nonmetastatic mammary carcinoma cells

Acquisition of metastatic competence by tumor cells is frequently accompanied by increased expression of extracellular proteases capable of degrading basement membrane and extracellular matrix. However, very little is known about how the genes encoding these enzymes and their inhibitor proteins are regulated in metastatic versus nonmetastatic cells. In this report, we have compared autocrine and paracrine regulation of tissue inhibitor of metalloproteinases (TIMP), transin, and urokinase plasminogen activator (uPA) genes in genetically related nonmetastatic SP1 and metastatic A3a cell lines. Compared to SP1 cells, metastatic A3a cells showed 15-20-fold higher transin, 3-5-fold less TIMP mRNA, and comparable levels of uPA mRNA. A qualitatively similar shift in expression of these genes was rapidly (i.e., 4-8 h) induced in nonmetastatic SP1 cells following the addition of conditioned medium from A3a cells. The gene-regulating activity present in A3a conditioned medium was heat-labile, suggesting that it was protein in nature. The responsiveness of SP1 cells to the factor(s) secreted by A3a conditioned medium was inhibited by cycloheximide. Basic fibroblast growth factor mimicked the effect of the A3a conditioned medium as an inducer of transin expression in the tumor cells. Although medium conditioned by the tumor cells did not affect uPA expression, addition of epidermal growth factor to the tumor cells transiently induced expression of uPA with a biphasic response that differed in SP1 and A3a cells. Initial induction of uPA at 2-4 h was similar for both cell lines, but after 24 h of exposure to epidermal growth factor, SP1 cells showed a net reduction in uPA, whereas metastatic cells returned to the unstimulated levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Genotypic and phenotypic evolution of a murine tumor during its progression in vivo toward metastasis

To follow the cellular progeny of the multiple-drug-marked benign murine tumor cell line MDW4 during its progression in vivo toward metastatic spread in DBA/2 mice, the following parameters were analyzed: retention of the drug-resistant markers ouabain resistance (OuaR) and thioguanine resistance (ThgR), lectin-resistance pattern (WGAR), and the karyotype of cell populations (and clones derived from these cells) removed at intervals from the solid tumor growing at the site of inoculation, as well as distant metastatic nodules. It was determined that the initially homogeneous inoculum composed of OuaR, ThgR, and WGAR hypotetraploid cells (mode: 68 +/- 2 chromosomes) was gradually overgrown and replaced by a new population of cells that were either OuaR or ouabain-sensitive but that became thioguanine-and lectin-sensitive and hyperploid (mode: 95 +/- 5). Regardless of the composition of the individual drug marker combinations, only cells with high chromosome contents were found to be able to disseminate to distant visceral organs and to rapidly produce metastases upon sc or iv reinjection. The presence of the same number of metacentric chromosomes in metastatic cells as in MDW4 and the coextinction of two recessive drug-resistant markers (WGAR and ThgR) suggested that cells endowed with invasive-metastatic potential represent the product of spontaneous somatic hybridization between the original nonmetastatic MDW4 cells and normal host cells of unknown origin. Such a fusion was followed by more or less extensive chromosome segregation that accounts for the karyotype mosaicism and the occasional drug marker heterogeneity identified in cell populations of metastatic nodules.

Science Signaling Podcast: 18 February 2014

The adaptor protein p66Shc decreases glucose uptake and metabolism by inhibiting mTOR signaling.

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.

The Internet and education in surgery

The purpose of this review is to explain the developing role of the Internet and the World Wide Web (WWW) in promoting education in surgery. Internet sites relevant to surgery are appearing rapidly. Remote literature searches can query for surgery trials and results. Societies are using the WWW for transmission and review of publication materials. News groups interactively discuss current developments and trends. Surgeons are using personal and institutional sites to advertise services. Conventional slide shows migrate to the WWW for convenient downloading for surgeons and patients. Multimedia capabilities of the WWW expand the depth of information transmission, enabling education emanating from remote sites with narration and video depiction of procedures. These sophisticated tools can be demonstrated today with real online applications. One site facilitates surgical education using the WWW for program information, symposium coordination, links to regional subspecialty societies, residency cataloging, patient question and answer forums, and multimedia procedure descriptions. The principles of WWW communication used in this website can adapt to meet any educational need. The specialty of surgery is well suited to incorporation of online multimedia education over the Internet to follow new developments in our field.

Increased UDP-GlcNAc:Gal beta 1-3GaLNAc-R (GlcNAc to GaLNAc) beta-1, 6-N-acetylglucosaminyltransferase activity in metastatic murine tumor cell lines. Control of polylactosamine synthesis

Malignant transformation of rodent cell lines by polyoma virus and by activated ras genes is associated with increased UDP-GlcNAc:Man alpha-R beta-1,6-N-acetylglucosaminyltransferase V (GlcNAc-transferase V) activity and it product -GlcNAc beta 1-6Man alpha 1-6Man beta 1-branched Asn-linked oligosaccharides. In this report, we have compared beta 1-6GlcNAc branching of core O- and N-linked oligosaccharides in three experimental models of malignancy, namely (a) rat2 fibroblasts and their malignant T24H-ras-transfected counterpart; (b) benign SP1 mammary carcinoma cells and two metastic sublines of SP1; and (c) the metastatic MDAY-D2 lymphoma cell line and its poorly metastatic glycosylation mutant KBL-1. In addition to the previously reported increase in GlcNAc-transferase V activity, UDP-GlcNAc:Gal beta 1-3GalNAc alpha-R (GlcNAc to GalNAc) beta-1,6-N-acetylglucosaminyltransferase (core 2 GlcNAc-transferase, EC 2.4.1.102) activity was found to be elevated by 70% in the malignant rat2 and SP1 cell lines while several other glycosyltransferase activities were not significantly different. The action of core 2 GlcNAc-transferase followed by beta 1-4Gal-transferase provides an N-acetyllactosamine antenna that can be extended with polylactosamine (i.e. repeating Gal beta 1-4GlcNAc beta 1-3) provided UDP-GlcNAc:Gal beta-R beta 1-3GlcNAc-transferase (GlcNAc-transferase) (i)) activity is present. Polylactosamine content in microsomal membrane glycoproteins was quantitated by labeling the GlcNAc termini resulting from the action of Escherichia freundii endo-beta-galactosidase with bovine galactosyltransferase/UDP-[3H] Gal. Glycopeptidase F- sensitive and -insensitive fractions were measured to assess the N- and O-linked components. In the SP1 tumor model, the metastatic sublines showed increased core 2 GlcNAc-transferase and GlcNAc-transferase V activities but no change in GlcNAc-transferase (i) activity, yet polylactosamine was increased in both O- and N-linked oligosaccharides. In rat2 cells, down-regulation of GlcNAc-transferase (i) following transformation was associated with decreased polyactosamine even though core 2 GlcNAc-transferase and GlcNAc-transferase V were elevated in the cells. Finally, a 3-fold decrease in GlcNAc-transferase V in KBL-1, the glycosylation mutant of MDAY-D2 cells, resulted in complete loss of polylactosamine in N-linked but no change in O-linked polylactosamine content. These results suggest that, provided GlcNAc-transferase (i) is not limiting, the beta 1-6-branching enzymes core 2 GlcNAc-transferase and GlcNAc-transferase V regulate the levels of polyactosamine in O- and N-linked oligosaccharides, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

EA rosettes using IgG monoclonal antibody-coated erythrocytes: degree of rosette formation correlates with the amount of antibody on the erythrocytes

The EA (Fc receptor) rosetting assay, which utilizes sheep erythrocytes (SRBC) coated with anti-SRBC antibodies as indicator cells (EA) is a rapid and convenient method for the detection of Fc-receptor-positive cells. To prevent haemagglutination of the EA indicator cells, it has been necessary to dilute conventional SRBC antisera. Owing to this technical restriction, it has not been possible to determine accurately the contribution of antibody density on the EA indicator cells to the level of Fc-receptor-positive cells measured in the EA rosetting assay. However, the availability of high-titred non-haemagglutinating monoclonal anti-SRBC antibodies has provided a means of examining this problem. Four non-haemagglutinating monoclonal anti-SRBC IgG preparations-two of the IgG2a subclass, an IgG2b subclass-specific and an IgG1 subclass-specific antiserum-were used to coat SRBC at antisera dilutions ranging from 1/20 to 1/2000. The amount of antibody bound to the SRBC was determined by an indirect radioimmunoassay utilizing 125I-labelled protein A. The four monoclonal anti-SRBC antibodies were shown to have unique affinities for the erythrocytes, and each was specific for antigens present in differing amounts on the SRBC. The number of Fc-receptor-positive cells detected in a spleen cell suspension or in a homogeneous Fc-receptor-positive tumour cell population by the EA (Fc) rosetting assay was found to be directly proportional to the amount of monoclonal antibody (regardless of the IgG subclass) bound to the EA indicator cells.

Tn antigen and UDP-Gal:GalNAc alpha-R beta 1-3Galactosyltransferase expression in human breast carcinoma

The serine/threonine O-linked carbohydrates GalNAc alpha and Gal beta 1-3GalNAc alpha, referred to as Tn and T antigens, respectively, appear to be more prevalent in some human carcinomas than in surrounding tissues. Tn/T antigens may represent incomplete synthesis of O-linked oligosaccharides, due to decreased activity of specific glycosyltransferases, or alternatively, increased glycosidases activity in tumors which may expose these internal O-linked oligosaccharide sequences. To explore these possibilities, we measured UDP-Gal:GalNAc alpha-R beta 1-3 galactosyltransferase (beta 3Gal-T) and Gal beta 1-3GalNAc alpha-R beta 1-3 galactosidase in a series of human breast tumors. In addition, glycoproteins extracted from the tumors were separated by SDS-PAGE and stained with the lectins HPA (GalNAc alpha-R reactive) and PNA (Gal beta-3GalNAc alpha-R reactive). The relative levels of HPA- to PNA-reactive glycoproteins in the carcinomas correlated inversely with beta 3Gal-T activities. The results suggest that Tn antigen expression in human breast carcinoma is due in part to low beta 3Gal-T activity, a situation similar to that observed previously in haematopoietic cells of individuals with a condition called Tn syndrome.

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.