Apparent DNA-binding protein specific for cells transformed by avian acute leukemia viruses

An apparent DNA-binding protein is described that is specific for cells transformed by avian acute leukemia viruses. This protein cannot be demonstrated in cells transformed by any of the avian sarcoma viruses or in cells infected with nontransforming avian retroviruses. The protein also is not detectable in noninfected quail or chicken embryo primary cultures or in noninfected chicken hematopoietic cells. The apparent molecular weight of this protein is 105,000 and it is referred to as DBP105.

Defective v-erbB genes can be complemented by v-erbA in erythroblast and fibroblast transformation

We have introduced 3'-terminal deletions of increasing size in the v-erbB oncogene and analysed the effects of these mutations on the transformation of fibroblasts and erythroblasts. The results show that the transforming activity of the mutants is gradually diminished, and completely abolished in those mutants that do not produce stable v-erbB proteins. The capacity to transform erythroblasts is lost before fibroblast transformation is severely affected, suggesting that a larger part of the C-terminal domain is required for mitogenic signalling in erythroid cells than in fibroblasts. In addition, the v-erbA oncogene was found to cooperate with v-erbB not only in erythroblast but also in fibroblast transformation, inducing a fully transformed phenotype in fibroblasts partially transformed by a mutant erbB oncogene.

Prominent glutamine oxidation activity in mitochondria of avian transplantable hepatoma induced by MC-29 virus

Well coupled mitochondria were isolated from transplantable chicken hepatoma induced by MC-29 virus. The mitochondrial phosphate-dependent and phosphate-independent glutaminase activities were increased compared with those from normal chicken liver. Glutamate dehydrogenase was undetectable in the tumor mitochondria. Oxypolarographic tests showed the following: glutamine oxidation was prominent in the tumor mitochondria and was mediated through an NAD-linked reaction, while mitochondria from the liver showed a feeble glutamine oxidation; glutamine oxidation by tumor mitochondria was inhibited either by aminooxyacetate, inhibitor of transaminases, or prior incubation of mitochondria with DON (6-diazo-5-oxonorleucine), which inhibited mitochondrial glutaminases. Bromofuroate, inhibitor of glutamate dehydrogenase, had little or no effect; and glutamate oxidation was also inhibited by aminooxyacetate, while it was not affected by DON. These findings clearly show a high glutamate oxidation activity in the hepatoma and indicate that the product of glutamine hydrolysis, glutamate, is catabolized via transamination in the mitochondria to supply ATP.

Design of retroviral vectors for the insertion of foreign deoxyribonucleic acid sequences into the avian germ line

Because the available avian leukosis viral (ALV) vectors are moderately oncogenic in vivo, they are not suitable for insertion into the germ line. A significant reduction in the oncogenicity of the ALV vectors can be achieved by substituting the noncoding long terminal repeats (LTR) regions of the ALV virus with the LTR of the nononcogenic endogenous RAV-O virus. There is good evidence that the resulting RAV-O LTR vectors can be inserted into the germ line of domestic chickens and have the potential for inserting cloned sequences that can be used for poultry improvement.

The pathway of glutamate oxidation in isolated mitochondria from the avian hepatomatous growth induced by MC-29 virus

The mitochondria isolated from transplantable chicken hepatomatous growth induced by MC-29 virus were deficient in glutamate dehydrogenase. Oxypolarographic tests showed that glutamate oxidation in the tumor mitochondria was initiated via transamination, while glutamate was deaminated by glutamate dehydrogenase in liver mitochondria to supply adenosine triphosphate. Prominent glutamate oxidation and transformation-linked low glutamine synthetase activity may be favorable to the bioenergetics of this fast-growing tumor.

Enhanced transcription of c-myc in bursal lymphoma cells requires continuous protein synthesis

In several bursal lymphoma cell lines in which c-myc transcription is regulated by avian leukosis virus (ALV) long terminal repeat (LTR) sequences, protein synthesis inhibition decreases the transcriptional activity of c-myc as well as other LTR driven viral genes. This decrease in transcription is associated with a change in the chromatin structure of c-myc, as measured by deoxyribonuclease I (DNase I) hypersensitivity, and a shift of transcription from the LTR to the normal c-myc promoter. In contrast, cycloheximide had little or no effect on the transcription of LTR driven genes in infected chicken embryo fibroblasts treated with the drug. These results suggest that a labile, cell type-specific protein may interact with the retroviral LTR and regulate transcription of genes under LTR control. Further, the results demonstrate that the increase in intracellular concentration of c-myc RNA induced by cycloheximide treatment of normal cells is the result of stabilization of this message.

Analysis of a tyrosine-specific protein kinase activity associated with the retroviral erbB oncogene product

The transforming protein erbB of avian erythroblastosis virus (AEV) has considerable sequence homology with the epidermal growth factor (EGF) and appears to represent a truncated form of this receptor. The sequence of the erbB gene is furthermore related to that of other viral transforming genes such as src, fps, yes or abl. The transforming proteins of these src-related oncogenes as well as receptors for EGF, platelet-derived growth factor (PDGF), and insulin are associated with tyrosine-specific protein kinases. It has been difficult to demonstrate this activity for the erbB protein. To analyze the erbB gene product, we prepared polyclonal antibodies against a bacterially expressed erbB DNA restriction fragment (BamHI/BamHI). The antiserum is shown to immunoprecipitate the erbB protein from AEV-transformed chicken fibroblasts and also recognizes the EGF receptor protein. Both proteins become phosphorylated in vitro on tyrosine residues upon the addition of [gamma-32P]ATP. The protein kinase activity is low compared to other oncogene-specific kinases. This is not due to kinase blocking by the serum, because erbB carboxyterminal synthetic peptide antibodies give rise to low levels of protein kinase activity as well indicating that this may be a characteristic property of erbB in vitro.

Enhanced viral inhibition of lymphocyte mitogenesis in patients with advanced breast cancer

Virus particles are frequently able to non-specifically inhibit the capacity of human peripheral blood lymphocytes to respond to mitogenic or antigenic stimuli. In the case of breast cancer patients with advanced disease, the quantity of virus required to abrogate responsiveness to phytohaemagglutinin (PHA) was approximately four-fold less than that found when cells from healthy donors were employed. The results show that such virus co-incubated cultures are deficient with regard to their ability to synthesize detectable quantities of T cell growth factor (TCGF) activity, and that the extent of responsiveness to PHA in each case corresponds roughly to the amount of TCGF activity that is present in the cultures. While the addition of exogenous purified TCGF to cultures containing virus, normal cells and stimulus caused a reversal of the usual inhibitory effect, this finding was generally not obtained in the case of lymphocytes obtained from patients with advanced breast cancer. These data suggest that one mechanism of explaining diminished cellular immune responsiveness in breast cancer patients may be a relative inability of appropriate cells or subsets of cells to respond effectively to TCGF.

Effect of avian osteopetrosis virus infection on cells and their collagen synthesis in vitro

Primary avian tendon fibroblasts and calvarial osteoblasts were infected with the avian osteopetrosis virus MAV.2-O, in vitro. The infected tendon cells could be cloned in soft agar and kept in culture for at least 25 passages, a number not reached by uncloned infected cells. In contrast to many other virus-transformed fibroblasts, these cells continued making collagen and fibronectin, and there were no gross morphological changes as observed in the light microscope. Changes were seen in their cytoskeletal structure, however, as observed by immunofluorescence. The cloned cells were not tumorigenic in nude mice, nor had they an altered pattern of protein phosphorylation. MAV.2-O-infected fibroblasts and the cloned cells synthesized 2-3 times more collagen type I, the main product of their biosynthetic machinery, than control cells. The proportion of the total cellular RNA consisting of specific mRNAs for the precursor of collagen, procollagen pro-alpha 1 and pro-alpha 2 chains, was higher in the infected cells than in normal fibroblasts. Southern blotting experiments indicated that there was no rearrangement of the collagen genes after infection with this virus. Furthermore, large viral DNA fragments were not integrated into the immediate vicinity of the 5' end of the alpha 2-collagen gene.

Morphological transformation, autonomous proliferation and colony formation by chicken heart mesenchymal cells infected with avian sarcoma, erythroblastosis and myelocytomatosis viruses

Normal chicken heart mesenchymal cells at low density in monolayer culture in plasma-containing medium have a polygonal shape and are proliferatively quiescent. The combination of epidermal growth factor and insulin at hyperphysiological concentration, an insulin-like growth factor surrogate, causes these cells to assume a fusiform shape and to increase 40-fold in number during four days of incubation. These mitogenic hormones do not, however, induce normal chicken heart mesenchymal cells to form colonies in agarose suspension culture. Chicken heart mesenchymal cells infected with the Schmidt-Ruppin or Prague-A strains of Rous sarcoma virus or with the Fujinami or Y73 avian sarcoma viruses assume spindle and round shapes, increase 50-100 fold in number during four days of monolayer culture in the absence of mitogenic hormones and form macroscopic colonies during 3-4 days of agarose suspension culture. The autonomous (mitogenic hormone-independent) proliferation, in monolayer culture, of cells infected with temperature-sensitive transformation mutants of Rous sarcoma virus (tsNY68, tsNY72, tsLA24, tsLA29) is temperature-sensitive. Chicken heart mesenchymal cells infected with avian erythroblastosis virus assume spindle shapes and proliferate in monolayer culture at a rate comparable to that of sarcoma virus-infected cells but do not, however, form colonies in agarose suspension culture. Cells infected with the myelocytomatosis virus MC29 assume stellate shapes and increase 18-fold in number during four days of monolayer culture. Cells infected with the myelocytomatosis virus MH2 assume fusiform shapes and increase fourfold in number during four days of monolayer culture. Neither MC29 nor MH2 renders chicken heart mesenchymal cells capable of colony formation in agarose suspension culture. Infection with avian leukosis viruses (RAV-1, RAV-2, RPL-42) or with transformation-defective mutants of Rous sarcoma virus (tdNY105, 107, 109) does not affect the morphology or proliferative behavior of chicken heart mesenchymal cells. Monolayer culture of chicken heart mesenchymal cells in plasma-containing medium appears, therefore, to define the ability of onc genes of acute transforming avian retroviruses to induce autonomous (mitogenic hormone-independent) cell proliferation, the essential characteristic of neoplasia. The differences in transformed morphology and rates of autonomous proliferation between cells infected with different acute transforming retroviruses probably reflects differences in the modes of action of the transforming proteins encoded by the onc genes of the respective viruses.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-asbestos-related malignant mesothelioma. A review

Malignant mesothelioma is an uncommon, but increasingly important, neoplasm. The existing English-language medical literature concerning non-asbestos-related malignant mesotheliomas was reviewed for evidence of other agents associated with the induction of malignant mesothelioma. Both animal and human data were reviewed. In most reviews of malignant mesothelioma, there are a significant proportion of cases without documented asbestos exposure (range, 0% to 87%). Furthermore, there are several fairly well-documented agents other than asbestos that induce malignant mesothelioma in animals, and strong evidence exists that such is the case in man. In reviews of malignant mesothelioma, the percentage of cases with asbestos exposure varies, but a significant number are apparently not asbestos related. It is believed that sufficient evidence exists to suggest that non-asbestos agents can induce malignant mesotheliomas in man, and additional epidemiologic studies in this area are needed.

Proteins encoded by v-myc and c-myc oncogenes: identification and localization in acute leukemia virus transformants and bursal lymphoma cell lines

We have prepared an antiserum against a synthetic dodecapeptide whose sequence corresponds to the C terminus of the MC29 v-myc protein. This antiserum (anti-v-myc 12C) specifically precipitates the known gag-myc fusion proteins produced by the defective leukemia viruses MC29, CMII, and OK10, but does not react with gag-precursor or product proteins. In addition, proteins of 62 kd and 61/63 kd are precipitated by anti-v-myc 12C from OK10 and MH2 transformants, respectively. The serum also recognizes comigrating 62 kd proteins from three chicken bursal lymphoma cell lines and from the products of in vitro translation of c-myc-specific mRNA. All of these myc-related proteins are phosphorylated and all appear to be localized in the cell nucleus. In uninfected quail cells, anti-v-myc 12C also recognizes a candidate c-myc protein of 60 kd, which does not appear to be phosphorylated and is present in low levels relative to v-myc and lymphoma c-myc proteins.

Influence of diet on a retrovirus-induced obesity and stunting syndrome

An avian retrovirus, RAV-7, causes a syndrome characterized by stunting, high mortality, and obesity. In this study, the influence of the lipid content of the diet on the RAV-7-induced syndrome was examined. Failure to gain weight, a measure of the stunting, was not influenced by fat content of the diet, but a slight increase in mortality was noted with a low-fat diet.

Naturally occurring retroviruses (RNA tumor viruses). I

This is the first of two papers describing the naturally occurring retroviruses (RNA tumor viruses). Here, the general properties of these viruses and the biology of the fish, reptilian, chicken, and mouse retroviruses are described. In the next issue of Cancer Investigation the biologic properties of the cat, cattle, primate, and newly discovered human retroviruses will be discussed.

Animal model of human disease. Skeletal hyperostoses: viral induction of avian osteopetrosis

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A monoclonal antibody with specificity for leukemic cells transformed by defective avian leukemia viruses

Mouse anti-chicken monoclonal antibodies were raised against an avian myeloblastosis virus (AMV)-transformed myeloblastic leukemic cell line. One monoclonal antibody, S1-37 (IgG2a), reacted with producer and nonproducer myeloblastic leukemia cell lines transformed by AMV and by E-26 virus, but it did not react with chicken fibroblasts infected with RAV-2, MAV-2, MAV-1, or RAV-7. S1-37 also did not react with normal chicken hemopoietic cells, except for yolk sack macrophages and a small population of embryonal and adult bone marrow cells that morphologically resembled macrophages. Cytotoxicity studies of GM-CFU, the normal stem cell population of the granulocytic macrophage lineage, indicated that these cells lack the surface antigen recognized by S1-37. Immunoprecipitation studies of 125I surface-labeled myeloblastic leukemic cells indicated that S1-37 binds a 42,000 Mr polypeptide. The possible role of this polypeptide in the process of transformation and differentiation of chicken myeloid cells is discussed.

Biochemical characterization of transformation-specific proteins of acute avian leukemia and sarcoma viruses

The biological and biochemical properties of the transformation-specific proteins of three avian oncornaviruses with different oncogenic potentials were compared, namely the gag-myc protein of the avian myelocytomatosis virus MC29, the gag-erb A protein of the avian erythroblastosis virus AEV, and the gag-fps protein of Fujinami sarcoma virus FSV. These oncogenes were analyzed in transformed fibroblasts that expressed only the transforming proteins but showed no virus replication. Monoclonal antibodies against the viral structural protein p19, which is the N-terminus of the proteins, were used for indirect immunofluorescence, for immunoprecipitation of the proteins from subcellular fractions, and for immunoaffinity column chromatography. With this last method a 3000-fold purification of the proteins was obtained. By indirect immunofluorescence it was shown that the gag-myc protein was located in the nucleus, and bound to DNA after purification. The gag-erb A protein was not nuclear but probably located in the cytoplasm and did not bind to DNA after purification. Neither of the two proteins exhibited protein kinase activity. In contrast, the gag-fps protein did not bind to DNA but showed protein kinase activity after purification. It was not located in the nucleus either.

Histone H5 in the immature blood cells of chickens with leukosis induced by avian leukosis virus strain E26

Whole histone was isolated from the immature cells of the peripheral blood of White Leghorn chickens, line 151, with leukosis experimentally induced by avian leukosis virus, strain E26 (ALV-E26). Histone H5 was demonstrated in all samples of these cells and was characterized by electrophoresis in polyacrylamide gel, extraction with perchloric acid, amino acid analysis, and immunodiffusion in agarose gel. Histone H5 was not detected in the myeloblasts of chickens with myeloblastosis caused by the avian myeloblastosis virus. It was concluded that the immature cells (IBC-E26) obtained from the peripheral blood of chickens responding positively to ALV-E26 belonged to the erythroid blood cell series and that ALV-E26 induced in vivo erythroblastosis but not myeloblastosis in chickens. The relative amount of histone H5 in IBC-E26 was two times higher than that in the erythroblasts obtained from the peripheral blood of chickens with erythroblastosis caused by avian erythroblastosis virus, strain R of Engelbreth-Holm. Thus the erythroblasts in the circulating blood of chickens with leukosis induced by ALV-E26 seemed to be more differentiated.

Pathogenesis of virus-induced osteopetrosis in the chicken

Infection of chicken embryos with a nondefective avian leukosis virus MAV-2(0) induced bone hyperplasia and profound suppression of bursal and thymic lymphoid cell development within 2- to 3 weeks after hatching. A time-course study of infectivity during embryonal life showed a gradual loss of susceptibility between the 10th day of incubation and hatching. This finding suggests that an embryonal stem cell either before or early after seeding into the bone and primary lymphoid organs is a virus-susceptible target cell. Histologic observations of the bursa indicated only mild damage during the 1st week and severely impaired proliferation of follicular lymphoid cells during subsequent weeks of development. Thus, viral infection conferred a cytostatic rather than a cytolytic effect upon the lymphoid target cell. Infection of stem cells, which are progenitors of lymphoid cells as well as of bone osteoclasts, is compatible with the manifestations of the disease. A model of cellular disorders of the bone and lymphoid tissues is proposed. Adoptive transfer of lymphoid cells from adult MAV-2(0)-immunized chickens into histocompatible virus-infected juvenile recipients abrogated the manifestation of osteopetrosis. Passive injection of antiserum containing virus-neutralizing antibodies was also effective. Anti-gp85 viral surface glycoprotein-binding antibodies in sera from adoptively protected chickens receiving immune cells were exclusively of cell donor IgG allotype.

Viral DNA in bursal lymphomas induced by avian leukosis viruses

Avian leukosis viruses (ALV) induce malignant lymphoma of the bursa of Fabricius. Viral DNA in tumors and normal tissues from infected birds were analyzed by using restriction endonucleases. Viral DNA fragments diagnostic of the exogenous ALV were easily detected in tumors, uninvolved bursal tissue, kidney, and erythrocyte nuclei. Exogenous viral DNA was more difficult to detect in liver. Using a restriction endonuclease (SacI) which cleaves linear unintegrated ALV DNA in a single site to define integration sites in DNA from the various tissues, we were able to detect ALV DNA only in tumor tissue. We concluded that the proviral DNA detected in the various nontumor tissue must be integrated in multiple sites. The appearance of ALV integration sites uniquely in tumors suggests that they are clonal growths. Furthermore, the data suggested the presence of a single exogenous integration site for the ALV provirus in each of six early neoplastic bursal nodules. This provirus appeared to retain the organization of EcoRI and BamHI recognition sequences present in the genome of virus used to infect the birds. The ALV integration site appeared different in each of the tumors studied. In a widespread metastatic lymphoma, multiple ALV integration sites were found as well as structural alterations in at least some copies of the ALV provirus.