Colorectal carcinoma invasion inhibition by CO17-1A/GA733 antigen and its murine homologue

BACKGROUND

The gastrointestinal carcinoma antigen GA733 is a potential target for passive and active immunotherapy for patients with colorectal carcinoma. This antigen has been characterized previously as a homophilic adhesion (i.e., adhesion to self) protein, but the functional consequences of homophilic adhesion for tumor growth and invasion are unknown. The availability of a murine homologue of GA733, i.e., murine epithelial glycoprotein (mEGP), allows for functional analysis of cell adhesion as it relates to tumor growth and invasion, both in vitro and in vivo.

METHODS

CT-26 murine colorectal carcinoma cells were transfected with complementary DNAs encoding either the human or the murine antigen. GA733- or mEGP-producing cells were evaluated for homophilic adhesion, growth on plastic surfaces, colony formation in soft agar, and invasion through a reconstructed basement membrane (Matrigel). mEGP-producing cells were also examined for their capacity to metastasize in mice. Reported P values are two-sided.

RESULTS

Compared with control cells, mEGP-producing cells showed significantly lower growth rates, colony formation, and invasion through Matrigel in vitro (all P values <.05). Compared with vector-only transfected cells and parental cells, mEGP-producing cells showed a reduction in metastatic potential in syngeneic immunodeficient and immunocompetent mice (all P values <.05). In contrast to mEGP-transfected cells, GA733-transfected cells did not exhibit significantly reduced growth or colony formation in vitro (all P values >.05). However, GA733-transfected cells did show reduced invasion through Matrigel compared with vector-only transfected cells or parental cells (all P values <.05).

CONCLUSION

The adhesion proteins GA733 and mEGP inhibit invasion of tumor cells.

A new set of versatile vectors for the heterologous expression of foreign genes using the baculovirus system

A new set of versatile advanced baculovirus (BV) vectors for the production of fused proteins in insect cells, under the control of the strong polyhedrin promoter of the Autographa california nuclear polyhedrosis virus (AcMNPV), has been constructed. The vectors contain peptide tags which allow immunological detection, as well as purification of recombinant protein produced via the BV expression system.

Functional expression of the Aequorea victoria green fluorescent protein in insect cells using the baculovirus expression system

A DNA fragment encoding the green fluorescent protein (GFP) was isolated via PCR from a jellyfish Aequorea victoria cDNA, cloned and sequenced. Subsequently, a recombinant baculovirus bearing the coding region of the GFP under the transcriptional control of the Autographa californica nuclear polyhedrosis virus (AcMNPV) polyhedrin gene promoter was constructed and isolated. High-level expression of GFP could be easily monitored in Spodoptera frugiperda (Sf9) insect cells after infection with recombinant baculovirus, due to the intrinsic fluorescence (lambda(max) = 508 nm) of the recombinant protein after excitation with blue light (lambda(max) = 400 nm). The functional recombinant GFP displayed an apparent molecular mass of approximately 43 kDa and the fluorescence emission spectrum of the recombinant protein was virtually identical to that of the native green fluorescent protein.

Constitutive expression of the human D2S-dopamine receptor in the unicellular yeast Saccharomyces cerevisiae

The cDNA for the human D2S-dopamine receptor has been functionally expressed in the unicellular yeast Saccharomyces cerevisiae. Two expression plasmids pRS421D2 (original D2S-gene coding region) and pRS421D2S (the first 24 aa of the yeast STE2-gene are fused to the N-terminus of the D2S-gene) were constructed and transformed into the protease deficient S. cerevisiae strain cI3-ABYS-86. Northern blot analysis of total RNA from transformed yeast clones revealed that for both constructs the D2S-gene was constitutively transcribed from the plasmids PMA1 promoter. Membranes prepared from recombinant S. cerevisiae exhibited saturable binding with the antagonist [3H]methylspiperone. Competition studies revealed pharmacological properties for these sites which were comparable to those reported for the D2-receptor heterologously expressed in mammalian cells. The expression of the receptor was monitored by Western blot analysis using an antiserum raised against a peptide from the third intracellular domain of the receptor protein and by ligand binding assay.

Delineation of putative mechanisms involved in antibody-mediated clearance of rabies virus from the central nervous system

The in vitro biological activities of several rabies virus-neutralizing monoclonal antibodies (mAbs) were compared with their ability to prevent a lethal rabies virus encephalomyelitis. The protective activity of a particular mAb in vivo did not correlate with its virus-neutralizing activity in vitro; rather it was related to the mAb's ability to inhibit virus spread from cell to cell and to restrict rabies virus RNA transcription. Since treatment of rabies virus-infected cells with virus-neutralizing mAbs results in an endocytosis of the antibody, we hypothesize that an antibody may exert its inhibitory activity even after uptake by the cell. Post-exposure treatment of rats with a mAb that inhibited both virus spread and virus RNA transcription in vitro resulted in viral clearance from the central nervous system and protected the animals against a lethal rabies virus infection.

Primary structure and functional expression of the Na/Ca,K-exchanger from bovine rod photoreceptors

Complementary DNA encoding the Na/Ca,K-exchanger was isolated from bovine retina cDNA libraries. The complete full-length cDNA is approximately 4 kb long and contains an open reading frame of 3597 bp. The deduced amino acid sequence corresponds to a protein of 1199 amino acids with a calculated molecular weight of approximately 130 kDa. Hydrophobicity analysis revealed the presence of two alternating sets of hydrophobic and hydrophilic domains. There also exists a hydrophobic region at the N-terminus which may be part of a cleavable signal peptide. The protein shares limited sequence homology with the Na/Ca-exchanger from cardiac sarcolemma. Northern blot analysis indicates that the approximately 6 kb transcript is highly specific for retinal tissue. Insect cells infected with recombinant baculovirus bearing the full-length cDNA express a functional Na/Ca,K-exchanger with an apparent relative molecular weight of approximately 210 kDa, as determined by Western blotting.

Expression and cell membrane localization of rat M3 muscarinic acetylcholine receptor produced in Sf9 insect cells using the baculovirus system

A recombinant baculovirus bearing the cDNA coding for the rat muscarinic acetylcholine receptor subtype M3 placed under the control of the Autographa californica nuclear polyhedrosis virus polyhedrin gene promoter, was constructed. Polymerase chain reaction screening was used to identify the recombinant baculovirus. Northern blot analysis of total RNA from insect cells infected with the recombinant baculovirus indicated that the transcripts were abundant. Binding assays carried out with the muscarinic antagonist [3H]quinuclidinyl benzilate indicated that more than 1 x 10(6) receptors were produced per cell. Immunofluorescence microscopy showed that the receptor is located on the cell surface.

Purification and functional characterization of the human beta 2-adrenergic receptor produced in baculovirus-infected insect cells

A human cDNA fragment bearing the complete coding region for the beta 2-adrenergic receptor was introduced into the genome of Autographa california nuclear polyhedrosis virus under the control of the polyhedrin promoter. Binding studies using [125I]iodocyanopindolol showed that Sf9 insect cells infected with the recombinant virus expressed approximately 1 x 10(6) beta 2-adrenergic receptors on their cell surface. Photoaffinity labeling of whole cells and membranes revealed a molecular weight of approximately 46,000 for the expressed receptor. The receptor produced in insect cells is glycosylated but the extent and pattern differ from that of the receptor from human tissue. The heterologously expressed receptor was purified by alprenolol affinity chromatography, and was able to activate isolated Gs-protein.

Microtubule assembly is required for the formation of the pronuclei, nuclear lamin acquisition, and DNA synthesis during mouse, but not sea urchin, fertilization

Microtubule assembly is required for the formation of the male and female pronuclei during mouse, but not sea urchin, fertilization. In mouse oocytes, 50 microM colcemid prevents the decondensation of the maternal meiotic chromosomes and of the incorporated sperm nucleus during in vitro fertilization. Nuclear lamins do not associate with either of the parental chromatin sets although peripherin, the Pl nuclear peripheral antigen, appears on both. DNA synthesis does not occur in these fertilized, colcemid-arrested oocytes. This effect is limited to the first hours after ovulation, since colcemid added 4-6 hours later no longer prevents pronuclear development, lamin acquisition, or DNA synthesis. Neither microtubule stabilization with 10 microM taxol nor microfilament inhibition with 10 microM cytochalasin D or 2.2 micrograms/ml latrunculin A prevent these pronuclear events; these drugs will inhibit the apposition of the pronuclei at the egg center. In sea urchin eggs, colcemid or griseofulvin treatment does not result in the same effect and the male pronucleus forms with the attendant accumulation of the nuclear lamins. The differences in the requirement for microtubule assembly during pronucleus formation may be related to the cell cycle: In mice the sperm enters a meiotic cytoplasm, whereas in sea urchin eggs it enters an interphase cytoplasm. Refertilization of mitotic sea urchin eggs was performed to test the possibility that this phenomenon is related to whether the sperm enters a meiotic/mitotic cytoplasm or one at interphase; during refertilization at first mitosis, the incorporated sperm nucleus is unable to decondense and acquire lamins. These results indicate a requirement for microtubule assembly for the progression from meiosis to first interphase during mouse fertilization and suggest that the cytoskeleton is required for changes in nuclear architecture necessary during fertilization and the cell cycle.

CT, MR, and pathology in HIV encephalitis and meningitis

The value and limitations of CT and MR in human immunodeficiency virus (HIV) infection of the brain was determined by a retrospective analysis of the CT scans (22) and MR images (7) in 22 patients with pathologically proved HIV encephalitis (21) or meningitis (1). Our clinical-radiologic-pathologic correlation suggested that, especially in the early stages of the disease, CT and MR were relatively insensitive in detecting the primary changes of HIV encephalitis. The multiple bilateral diffuse microscopic glial nodules with multinucleated giant cells of HIV found at autopsy in both gray and white matter were usually not directly visualized by either CT or MR. Secondary, nonspecific changes, however, were seen. These included cortical atrophy, found in virtually all patients with HIV encephalitis, and HIV-induced foci of demyelination found in the minority of cases. On CT the latter were seen in the white matter as nonenhancing, nonmass-producing areas of low density; on MR they were seen as frequently progressive high-intensity signal abnormalities on T2-weighted images, usually in the periventricular white matter and centrum semiovale. MR was more sensitive in detecting these demyelinative lesions than was CT. The clinical diagnosis of HIV encephalitis usually antedated the radiographic diagnosis. In HIV meningitis, contrast CT was more definitive than MR, showing striking enhancement of the subarachnoid spaces, although MR was more sensitive in detecting the secondary parenchymal changes.

Kinetochore appearance during meiosis, fertilization and mitosis in mouse oocytes and zygotes

The events of mammalian fertilization overlap with the completion of meiosis and first mitosis; the pro-nuclei never fuse, instead the parental genomes first intermix at the mitotic spindle equator at metaphase. Since kinetochores are essential for the attachment of chromosomes to spindle microtubules, this study explores their appearance and behavior in mouse oocytes, zygotes and embryos undergoing the completion of meiosis, fertilization and mitoses. Kinetochores are traced with immunofluorescence microscopy using autoimmune sera from patients with CREST (CREST = calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) scleroderma. These sera cross-react with the 17 kDa centromere protein (CENP-A) and the 80 kDa centromere protein (CENP-B) found at the kinetochores in human cell cultures. The unfertilized oocyte is ovulated arrested at second meiotic metaphase and kinetochores are detectable as paired structures aligned at the spindle equator. At meiotic anaphase, the kinetochores separate and remain aligned at the distal sides of the chromosomes until telophase, when their alignment perpendicular to the spindle axis is lost. The female pronucleus and the second polar body nucleus each receive a detectable complement of kinetochores. Mature sperm have neither detectable centrosomes nor detectable kinetochores, and shortly after sperm incorporation kinetochores become detectable in the decondensing male pronucleus. In pronuclei, the kinetochores are initially distributed randomly and later found in apposition with nucleoli. At mitosis, the kinetochores behave in a pattern similar to that observed at meiosis or mitosis in somatic cells: irregular distribution at prophase, alignment at metaphase, separation at anaphase and redistribution at telophase. They are also detectable in later stage embryos. Colcemid treatment disrupts the meiotic spindle and results in the dispersion of the meiotic chromosomes along the oocyte cortex; the chromosomes remain condensed with detectable kinetochores. Fertilization of Colcemid-treated oocytes results in the incorporation of a sperm which is unable to decondense into a male pronucleus. Remarkably kinetochores become detectable at 5 h post-insemination, suggesting that the emergence of the paternal kinetochores is not strictly dependent on male pronuclear decondensation.

HTLV-I infection of cerebrospinal fluid T cells from patients with chronic neurologic disease

Antibodies reacting with HTLV-I, the etiologic agent of acute T cell leukemia/lymphoma and a transforming agent for T4-positive lymphocytes in vitro, have recently been described in sera of patients with chronic neurologic disease in the absence of lymphoproliferative disorders. The largest number of such cases was described in Japan and in the Caribbean and parts of South America. We report here two cases of patients with chronic neurologic disease whose cerebrospinal fluid (CSF)-derived T cells contain HTLV-I specific RNA sequences and antigens and are expressing retroviral particles. Only one of these patients has demonstrable antibody to HTLV-I in serum or CSF.

Keratin-like proteins that coisolate with intermediate filaments of BHK-21 cells are nuclear lamins

Four proteins of Mr approximately equal to 60,000, 65,000, 67,000, and 70,000 coisolate with the major intermediate filament (IF) structural proteins of BHK-21 cells. These proteins are keratin-like, they form distinctive paracrystals in vitro, and they are concentrated at the nuclear surface. Since these properties indicate similarities with the nuclear lamins, we have prepared conventional fractions of BHK-21 nuclei from which the same type of paracrystal is obtained. Furthermore, biochemical and immunological data demonstrate that the lamins are identical to the Mr 60,000-70,000 proteins found in IF preparations, and both sets of proteins are similar to keratin. These results suggest that an IF-like protein network is present in the nuclear lamina. We speculate that in some unknown way this network connects to the cytoplasmic IF network that courses from the juxtanuclear region to the cell surface. These proposed interconnecting networks may form part of the infrastructure of cytoskeletal-nuclear matrix-connecting links involved in signal transmission between the nuclear and cytoplasmic compartments of eukaryotic cells.

Monoclonal antibody to a highly glycosylated protein reacts in fixed tissue with melanoma and other tumors

A highly glycosylated protein with a molecular weight of 30,000 to 60,000 and a protein core of 20,000 daltons has been identified by antimelanoma monoclonal antibodies. The antigenicity of this melanoma-associated glycoprotein (MAG) was not destroyed in fixed paraffin-embedded melanoma tissue, and was present in malignant cells of cutaneous superficial spreading melanomas in skin (31/33) and in half of all metastatic melanomas examined (5/10). The antigen was not expressed by normal melanocytes. The strong reactivity of dysplastic nevi with the anti-MAG antibodies was comparable to that seen in radial growth phase melanoma. Antigen expression was much weaker in compound nevi where reactivity ranged from moderate in the junctional component and the upper dermis to absent at the base of the nevus.

Tumor induction by simian virus 40 in mice is controlled by long-term persistence of the viral genome and the immune response of the host

Simian virus 40 (SV40), which transforms mouse cells in vitro, has not been previously observed to cause tumors when injected in immunocompetent mice. We have investigated both the fate of the injected virion in mice and several immunological parameters as potential factors controlling tumorigenicity. We find that although SV40 does not replicate in mouse cells, the viral DNA can persist for many months postinjection; the majority of the viral DNA is found in the cytoplasm, but a small amount of the viral DNA is integrated at multiple sites in the host nuclear DNA. The persistence of the viral genome is independent of the ability of the mouse to mount an SV40 TSTA specific cytotoxic T-cell response and may be attributed to the cytoplasmic location of the majority of the viral genome. However, in long-term studies of SV40-injected mice, genetically identical except for the major histocompatibility complex, we find that tumors were induced in some mice of the H-2d (low cytotoxic T-lymphocyte responder to SV40 TSTA) but not of the H-2k (high responder to SV40 TSTA) haplotype. Thus, a combination of inefficient disposal of the injected virion and inefficient immunological surveillance and elimination of cells containing nuclear SV40 DNA can eventually result in SV40-induced tumors at multiple sites in mice.

Possible mechanism for donor DNA binding and transport in Haemophilus

Morphological differences were observed in competent and noncompetent Haemophilus parainfluenzae and Haemophilus influenzae when thin sections of these cells were examined by electron microscopy. The membranous extensions present on the surface of competent H. parainfluenzae cells disappeared on treatment with transforming DNA, while vacuole-like structures appeared in the periplasm. Noncompetent cells had 1/5th as many extensions on their surface as competent cells, and no vacuoles were observed after treatment with homologous DNA. Competent cells treated with radiolabeled DNA were disrupted and the clarified lysate was centrifuged on CsCl density gradients. Material having a density of 1.34 g/ml was found to contain the majority of the DNase-resistant radioactive DNA recovered from the bacteria and was shown by electron microscopy to be composed of membrane vesicles. The polypeptide composition of this dense membrane fraction was similar to that of H. parainfluenzae outer membrane.

Positive detection of mycoplasma contamination by the whole-mount preparation of cell cultures for transmission electron microscopy

Low-level mycoplasma contamination of cell cultures is difficult to recognize with presently available techniques. This report describes the adaptation of the whole-mount technique, usually used for scanning microscopy, for transmission electron microscopy. The differentiation between microvilli and the equal-sized filamentous mycoplasma is based on the differential density obtained by the use of the method described. This method allows positive identification of mycoplasma and reduces the preparation time and the time necessary for scanning the preparation.

Multiple knife cuts between the medial and lateral hypothalamus in the rat: a reevaluation of hypothalamic feeding circuitry

Single or multiple sets of bilateral knife cuts were made in female rats just lateral to the ventromedial hypothalamus (VMH) and/or just medial to the lateral hypothalamus (LH). The lateral VMH cuts by themselves produced greater hyperphagia and obesity than did the medial LH cuts. The lateral VMH knife cuts also significantly increased food intake and body weight in rats previously given bilateral cuts along the medial LH border. These findings indicate that the feeding inhibitory fibers responsible for the hyperphagia syndrome do not project from the VMH to the LH, and this calls for a reevaluation of hypothalamic circuitry. It was also discovered that sham surgery has a significant suppressive effect on the hyperphagia syndrome produced by hypothalamic knife cuts.