Showing papers on "Friend leukemia published in 1976"

Sequential induction of heme pathway enzymes during erythroid differentiation of mouse Friend leukemia virus-infected cells.

Abstract: The process of erythroid differentiation in mouse Friend leukemia virus transformed cells (T3-C1-2) was examined by following changes in several enzyme activities of the heme biosynthetic pathway and in heme concentration while the cells were undergoing erythroid differentiation after treatment with dimethylsulfoxide. Untreated cells on the one hand, have a limited capacity for spontaneous differentiation. On the other hand, dimethylsulfoxide(DMSO)-treated cells showed an increase in the activities of delta-aminolevulinic acid (ALA) synthetase, ALA dehydratase, uroporphyrinogen-I synthetase, ferrochelatase, and heme concentration by days 1, 1.5, 2, and 4, respectively. The increase of the heme pathway enzymes and heme concentration followed the order of these enzymes or products as they are arranged in the heme biosynthetic pathway. These changes induced by DMSO were effectively inhibited by treatment with actinomycin D, suggesting that continued RNA synthesis is required for the differentiation process. 5-bromo-2'-deoxyuridine (BrdU) (10(-5) M) inhibited the DMSO-induced changes of the heme pathway enzymes. BrdU was most effective when it was present during the first 2 days of cell culture. It gradually lost its inhibitory effect when added after the 3rd day or later. The BrdU-mediated inhibition was completely overcome by the addition of thymidine (7 x 10(-5) M), but not by uridine (7 x 10(-5) M). All these data suggest that a sequential induction of the heme pathway enzyme takes place during erythroid differentiation of Friend leukemia cells, and that the sequential induction of the enzymes may be due to a sequential activation of genes coding for these enzyme activities.

Erythroid Differentiation in Cultured Friend Leukemia Cells Treated with Metabolic Inhibitors

Abstract: Summary The induction of erythroid differentiation in the T3-CI2 clone of Friend leukemia cells by dimethyl sulfoxide is accompanied by reduction in viral RNA-dependent DNA polymerase activity with increased cellular δ-aminolevulinic acid synthetase activity and hemoglobin synthesis. These cells were treated with a variety of compounds to determine whether other drugs are capable of inducing erythroid differentiation. While several hormones, inhibitors of RNA synthesis, organic solvents, inhibitors of DNA polymerase, sulfhydryl inhibitors, and inducers of δ-aminolevulinic acid synthetase administered singly did not stimulate hemoglobin synthesis like dimethyl sulfoxide, inhibitors of DNA and RNA synthesis such as adriamycin, mitomycin C, and hydroxyurea:mithramycin were synergistic in stimulating erythroid differentiation.

Studies on the role of the host immune response in recovery from Friend virus leukemia. II. Cell-mediated immunity.

Abstract: Congenic mouse strains differing only at genes within the H-2 complex were found to have virus-specific cytotoxic effector cells in their spleens during or after recovery from Friend leukemia virus-induced splenomegaly. These effector cells were theta-positive T lymphocytes which functioned in vitro without help or inhibition by B lymphocytes or glass-adherent cells. The antigenic specificities recognized by the effector cells were viral-induced cellular antigens apparently different from those identified by serological techniques.

Mouse strain resistant to N-, B-, and NB-tropic murine leukemia viruses.

Abstract: Mouse strain G was studied for its susceptibility to various strains of murine leukemia and sarcoma viruses. Both N- and NB-tropic Friend leukemia viruses neither induced splenomegaly nor grew efficiently in strain G mice. Using the XC test, cultured embryo cells were found to be resistant, but not absolutely, to all the tested viruses, N-tropic AKR virus, N- and NB-tropic Friend leukemia viruses, NB-tropic Rauscher leukemia virus, B-tropic WN1802B virus, NB-tropic Moloney leukemia and sarcoma viruses, and N-tropic Kirsten sarcoma virus, although the resistance to Moloney leukemia and sarcoma viruses is sometimes not as strong as that for other viruses. Thus, the strain G mice are unique among mouse strains because they show resistance that is not related to the N-B tropism of murine leukemia viruses.

Relationship of Friend murine leukemia virus production to growth and hemoglobin synthesis in cultured erythroleukemia cells.

Abstract: The factors that control oncornavirus formation were analyzed in Friend leukemia cells that undergo hematopoiesis when treated with dimethyl sulfoxide. Suspension cultures of Ostertag FSD-1 cell line were found to enter a G or resting state at the end of their proliferative phase and to simultaneously cease producing helper and dependent components of Friend virus. Whereas the decline in virus production is at least 100-fold, rates of cellular RNA and protein synthesis are only slightly lower in resting than in growing cells. Both resting and growing cells contain similarly large concentrations of the viral proteins P(30) and P(12). Dimethyl sulfoxide induces hemoglobin synthesis in growing cells, but its effects on virus production appear to be indirect results of its action to inhibit cell growth and thus to delay entry of cells into the G resting state. Furthermore, variant cell lines were obtained with differing abilities to synthesize virus or hemoglobin. Some lines no longer produce infectious virus, although they all harbor murine leukemia virus genes which are expressed to varying extents. The major internal protein of these oncornaviruses, P(30), is synthesized in large amounts by all of the cell lines. These results suggest that Friend virus production is not coinduced with erythroid differentiation, as had been proposed, but rather is controlled by a cellular growth cycle.

Isolation and characterization of high and low differentiation-inducible Friend leukemia lines.

Abstract: Induction of erythrodifferentiation was carried out by addition of dimenthyl sulfoxide or butyric acid to the culture medium among 80 subclones of T-3-Cl-2 Friend mouse leukemia line. Hemoglobin-positive cells were counted on day 5 of the inducer treatment on the hemocytometer after benzidine staining. Some cell lines were indicible by both of the inducers, but others were insensitive to dimethyl sulfoxide, but sensitive to butyric acid. Eight characteristic T-3-Cl-2 subclones have been selected; 2 highly inducible, 2 moderately inducible, and 4 minimally inducible. The data of differentiation inducibility together with the history of the T-3-Cl-2 line may facilitate extensive application of the T-3-Cl-2 system.

Granulocytic stem cells in Friend leukemia.

Abstract: Friend virus induces a leukemia characterized by the proliferation of neoplastic hematopoietic cells believed to be erythroid precursors. In vitro studies were conducted with spleen cells from mice with terminal Friend leukemia in order to determine their capacity for leukocytic differentiation. Spleen cells were obtained from leukemic DBA/2 mice 1 to 2 days before anticipated death and cultured in the presence or absence of colony-stimulating activity (CSA). Growth in liquid culture in diffusion chambers was dependent on CSA and resulted in the generation of normally differentiated granulocytes and macrophages. Colony formation in agar was also dependent on CSA, and the cloning efficiency of leukemic spleen cells was found to be approximately 10 times normal. The colonies formed were composed of leukocytes, which appeared morphologically normal. Total in vitro colony-forming units per leukemic spleen exceeded normal by more than 300-fold, but cells elaborating CSA were decreased. Although it is uncertain whether the stem cells stimulated by CSA are “normal” or “leukemic,” it is clear that Friend leukemia has profound effects on the proliferation and differentiation of nonerythroid stem cells.

Cell-mediated Immunity to Leukemia Virus- and Tumor-associated Antigens in Mice

Abstract: Cell-mediated immune reactions appear to play an important role in resistance against growth of leukemia cells in mice. Possible mechanisms for in vivo protection in two tumor systems are discussed. These tumor models, which are a Friend leukemia virus-induced transplantable tumor, FBL-3, and primary murine sarcoma virus (MSV) -induced tumors, are strongly antigenic; under some conditions, tumors regress completely. In mice with regressing FBL-3 tumors, cell-mediated cytotoxicity was measured by release of [125I]iododeoxyuridine. The response was biphasic, with an initial peak at 10 days and a 2nd peak after 30 days. A boost in reactivity could be elicited by later challenge with tumor cells. All of the reactivity was dependent on T-cells, being eliminated by treatment with anti-theta plus complement. The specificity of the reactions was not completely defined, but it was consistent with Friend type-specific antigen plus broader, common antigens. In mice with regressing MSV tumors, strong cell-mediated cytotoxicity, measured mainly by release of 51Cr, was seen against RBL-5, a Rauscher virus-induced leukemia. A single peak of response occurred at about 14 days after virus inoculation. Upon later challenge with RBL-5 cells, a vigorous and rapid secondary response was elicited, mainly in the region of tumor challenge. This cytotoxic reactivity and in vivo resistance to leukemia.lso was completely dependent on T-cells. In addition, macrophage-mediated inhibition of leukemia cell growth in vitro was seen in this system at the time of peak tumor development. The 51Cr release cytotoxicity was specific and directed primarily against an antigen, MEV-SA1, associated with mouse endogenous C-type viruses. The macrophage-induced growth inhibition appeared to be nonspecific. In both the FBL-3 and MSV tumor systems, protection against tumor growth could be adoptively transferred by immune lymphoid cells. In addition to induction of cell-mediated immunity by tumor cell or virus inoculation, cell-mediated cytotoxic reactivity was found to occur naturally in most young mice. This natural killer activity was quite distinct from the experimentally elicited reactions, being mediated by N-cells, a subpopulation of lymphoid cells with no clearly identifiable cell surface markers. The natural cytotoxicity was also directed against antigenic specificities different from those recognized by the MSV-immune cells. The central issue in all of these studies has been to determine the relationships between the in vitro-detected cell-mediated reactivity and in vivo resistance to leukemia.

Inhibition of friend murine leukemia virus production by low-ionic-strength medium.

Abstract: The effect of medium of low ionic strength on the release of virus from Friend leukemia cells has been studied. The release of infectious Friend leukemia virus is almost completely inhibited in medium of low ionic strength, as measured by a focus-forming assay (XC assay), by endogenous RNA-dependent DNA polymerase activity of released virus particles, and by electron microscope studies of the production of C-type particles. Friend leukemia virus-transformed proerythroblasts undergo extensive morphological changes in low-ionic-strength medium. The cells are viable in this medium, but they can no longer be stimulated with dimethyl sulfoxide to produce hemoglobin and increase virus production. Infectious virus is released between 30 and 120 min of resuspension of inhibited cells in normal medium. The rate of virus release after reversal of the inhibition is much greater than the rate of virus release during normal cell growth. The morphological changes occurring after dimethyl sulfoxide stimulation of Friend leukemia cells are compared with those resulting from resuspension in normal medium of cells inhibited by low ionic strength.

Immunodepression by Rowson-Parr virus in mice; lymphocyte markers and capping response of spleen and lymph node cells after infection.

Abstract: Infection with Rowson-Parr virus (RPV) induced a rapid reduction in the number of immunoglobulin-positive and theta antigen-positive cells detectable by immunofluorescence in the spleens of susceptible BALB/c mice. The changes produced by RPV infection in the lymph nodes were different, since the number of immunoglobulin-positive cells was increased and the proportion of theta-positive cells remained unchanged. However, the ability of immunoglobulin-bearing cells to redistribute their receptors into caps was reduced in both types of lymphoid tissue. A similar pattern of changes was produced by infection with Friend leukemia complex, from which RPV was originally obtained. These effects of RPV and Friend leukemia complex may contribute to the immunodepressed state of infected mice.

The Spleen in Friend Leukemia. II. Nonleukemic Nature of Spleen Stroma

Abstract: Pieces of Friend leukemic spleens implanted sc into mice regenerated into normal-appearing spleens if animals were protected against the leukemia. In unimmunized animals, the implant regenerated normally, but was subsequently infiltrated by leukemia cells. This leukemia cell infiltration required at least 30% stromal regeneration of the implant. The hematopoietic regeneration was primarily a repopulation with cells from the host animal, not with cells indigenous to the donor spleen. The development of the implant, whether normal or leukemic, was retarded by the presence of the host spleen, whether leukemic or normal. These studies strongly suggested that the stromal cells of the spleen are not directly involved in the virus-induced leukemic process but acted as supporting structure for the malignant cells.

Physiopathology of Human and Virus-induced Murine Leukemias

Abstract: The authors describe a coherent model for differentiated leukemias derived from physiopathological studies on Friend leukemia. In Friend leukemia, Friend virus induces permanent differentiation of erythropoietin-responsive cells. This erythropoietic proliferation and maturation is accompanied by a marked cell loss and provokes enlargement of the stem cell compartment. The so-called leukemic cells have a limited proliferation capacity and may not be truly malignant as opposed to blastic cells in acute leukemias. Clinical, hematological, and physiopathological data that are presently available in chronic granulocytic leukemia, polycythemia vera, and the erythroblastic component of erythroleukemia are compatible with the Friend physiopathological model. It is suggested that these differentiated leukemias initiate from an uncontrolled differentiation of a committed cell compartment, which stimulates proliferation of the stem cell compartment. The disease would be due to a proliferation and accumulation of “subnormal” cells characterized by a shorter mean life-span than the normal differentiated cell population. Although limited, the data available suggest that the physiopathology of acute leukemias is clearly distinguishable from that of differentiated leukemias; several immunological and therapeutic applications of this model are outlined.

Influence of immune stimulators on viral leukemogenesis.

Abstract: Injection of RNA, extracted from statolon by the SDS-phenol method, into FLV-infected mice 24 hours before SRBC immunization restored the immune response to SRBC to normal levels. Leukemosuppression was observed in 50% of the RNA-treated FLV-infected mice. These RNA-treated mice were clinically normal 25 days after infection, whereas all untreated infected mice developed erythroleukemia. Furthermore, all RNA-treated mice with suppressed erythroleukemia produced antibody which was cytotoxic for Friend leukemia cells. Our studies, and studies by others, indicate that the immunostimulatory and leukemosuppressive principle in statolon appears to be a dsRNA.

The spleen in Friend leukemia. I. Prolonged survival of leukemic mice after autoimplantation of spleen tissue.

Abstract: Friend virus infection of susceptible mice led rapidly to fulminant erythroleukemia and death. Subcutaneous implantation of leukemia spleen bits into splenectomized normal animals led to their early death from Friend leukemia. In contrast, bits of leukemic spleen implanted sc into splenectomized leukemic mice prolonged the survival of these animals. Concomitant with this survival was a reversal of the virus-induced immunosuppression and an increase in the levels of circulating, neutralizing, antivirus activity. This marked difference in response to leukemic spleen implants by leukemic as compared to normal mice reflected previous contact of the former with Friend Virus. Our studies indicated that the Friend virus-infected mouse mounted a resistance to the virus infection, which under certain conditions is capable of reversing the disease process.

Translation level control in normal and leukemic cells.

Abstract: A useful model for consideration of the biochemical aspects of cancer holds the primary lesion to be a block in the normal processes of differentiation. Erythroleukemia induced in susceptible mice by Friend leukemia virus appears to fit this model which is illustrated in Figure 1. This virus blocks the differentiation of erythroid cells at the proerythroblast stage (1, 2) before any appreciable synthesis of hemoglobin takes place (3). Friend virus transformed proerythroblasts from leukemic mice can be carried as permanent lines and are easily propagated in suspension culture. Differentiation as reflected by hemoglobin synthesis may be induced in vitro by the simple expedient of adding certain aprotonic solvents, such as dimethylsulfoxide (DMSO), to the tissue culture nutrient in which the Friend leukemia cells (FLC) are grown (3–5). Thus, these cell lines provide an excellent system for the study of both transcriptional and translational control mechanisms involved in differentiation leading to the synthesis of hemoglobin. A better understanding of these controls eventually could lead to the manipulation of the regulatory elements involved in leukemia.

Study on the mechanism of interference between Friend leukemia and Sindbis viruses in tissue culture.

Abstract: Some mechanisms of interference developing in BALB/c mouse embryo fibroblast culture (MEC) infected with Friend leukemia virus (FLV) and 48 hours later superinfected with Sindbis virus (SV) was studied. In FLV-infected cells the amount of SV antigen formed was 2-3 times lower than in SV monoinfection, as indicated by immunofluorescence and cytofluorimetry. Electron microscopic examination showed that in mixed infection the number of newly formed SV particles decreased markedly (by 90%) despite the presence of compact aggregates of viral nucleocapsids in the cytoplasm. When the cells were initially infected with arbovirus and then superinfected with FLV, formation of virus antigen and virions of both viruses was not disturbed. Pre-treatment of cell monolayer with dactinomycin (0.2 mug/ml) blocked interferon production in MEC culture and inhibited interference between FLV and SV. It is assumed that interference between FLV and SV is associated with known mechanisms of interferon action as well as with disturbance of the stage of SV particles assembly and their release from the cell. Due to incomplete cycle of SV reproduction interrupted at the stage of ribonucleoprotein formation, productive type of its interaction with MEC cells is disturbed.

Incomplete viral synthesis in friend leukemia virusinduced reticulum cell sarcomas

Abstract: Tissue-culture-passaged, Friend leukemia virus (FV)-induced reticulum cell sarcomas from BALB/c mice (FVTCT-BALB) did not produce infectious FV, although retrieval of infectious FV occurred when these cells were co-cultivated with cell lines replicating non-defective murine leukemia viruses (MLVs). The level of FV expression in the FVTCT-BALB cell line was studied to understand better the process of FV retrieval. 3H-uridine labelling techniques and reverse transcriptase assays showed that FVTCT-BALB cells did not release C-type virus particles. Nucleic acid hybridization techniques demonstrated that the level of viral RNA synthesis in the FVTCT-BALB non-producer cell line was indistinguishable from that in cell lines productively infected with MLVs. These data suggest that in the FVTCT-BALB cell line the synthesis of FV is blocked in some late stage of virus assembly.