spleen focus forming viruses


Summary: Strains of MURINE LEUKEMIA VIRUS that are replication-defective and rapidly transforming. The envelope gene plays an essential role in initiating erythroleukemia (LEUKEMIA, ERYTHROBLASTIC, ACUTE), manifested by splenic foci, SPLENOMEGALY, and POLYCYTHEMIA. Spleen focus-forming viruses are generated by recombination with endogenous retroviral sequences.

Top Publications

  1. Zon L, Moreau J, Koo J, Mathey Prevot B, D Andrea A. The erythropoietin receptor transmembrane region is necessary for activation by the Friend spleen focus-forming virus gp55 glycoprotein. Mol Cell Biol. 1992;12:2949-57 pubmed
    ..In addition, analysis of a soluble, secreted EPO-R and cysteine point mutants of the EPO-R show that the extracytoplasmic region of the EPO-R specifically interacts with gp55...
  2. Li J, Hu H, Niu Q, Fang C. Cell surface activation of the erythropoietin receptor by Friend spleen focus-forming virus gp55. J Virol. 1995;69:1714-19 pubmed
    ..Thus, our results support the hypothesis that the mitogenic activation of the EPO-R by gp55 requires the interaction of the two proteins at the cell surface...
  3. Wolff L, Ruscetti S. The spleen focus-forming virus (SFFV) envelope gene, when introduced into mice in the absence of other SFFV genes, induces acute erythroleukemia. J Virol. 1988;62:2158-63 pubmed
  4. Paul R, Schuetze S, Kozak S, Kabat D. A common site for immortalizing proviral integrations in Friend erythroleukemia: molecular cloning and characterization. J Virol. 1989;63:4958-61 pubmed
    ..Virol. 62:4129-4135, 1988). Exploiting the fact that each leukemia was a single clone that contained one tagged provirus, we have now molecularly cloned and characterized one common genomic site for immortalizing proviral integrations...
  5. Quang C, Wessely O, Pironin M, Beug H, Ghysdael J. Cooperation of Spi-1/PU.1 with an activated erythropoietin receptor inhibits apoptosis and Epo-dependent differentiation in primary erythroblasts and induces their Kit ligand-dependent proliferation. EMBO J. 1997;16:5639-53 pubmed
    ..They also suggest that the function of Spi-1/PU.1 in the late phase of Friend leukemia requires specific signaling from the gp55-modified EpoR generated during the early phase of the disease...
  6. Muszynski K, Ohashi T, Hanson C, Ruscetti S. Both the polycythemia- and anemia-inducing strains of Friend spleen focus-forming virus induce constitutive activation of the Raf-1/mitogen-activated protein kinase signal transduction pathway. J Virol. 1998;72:919-25 pubmed
  7. Aizawa S, Suda Y, Furuta Y, Yagi T, Takeda N, Watanabe N, et al. Env-derived gp55 gene of Friend spleen focus-forming virus specifically induces neoplastic proliferation of erythroid progenitor cells. EMBO J. 1990;9:2107-16 pubmed
    ..The p53 and Spi-1 genes were frequently aberrant in transplanted tumors and cell lines derived from them, but were not in primary leukemic spleens...
  8. Ruscetti S, Janesch N, Chakraborti A, Sawyer S, Hankins W. Friend spleen focus-forming virus induces factor independence in an erythropoietin-dependent erythroleukemia cell line. J Virol. 1990;64:1057-62 pubmed
  9. Muszynski K, Thompson D, Hanson C, Lyons R, Spadaccini A, Ruscetti S. Growth factor-independent proliferation of erythroid cells infected with Friend spleen focus-forming virus is protein kinase C dependent but does not require Ras-GTP. J Virol. 2000;74:8444-51 pubmed

More Information


  1. Nishigaki K, Thompson D, Hanson C, Yugawa T, Ruscetti S. The envelope glycoprotein of friend spleen focus-forming virus covalently interacts with and constitutively activates a truncated form of the receptor tyrosine kinase Stk. J Virol. 2001;75:7893-903 pubmed
    ..Our results suggest that SFFV gp55 may mediate its biological effects in vivo by interacting with and activating a truncated form of the receptor tyrosine kinase Stk...
  2. Demaison C, Parsley K, Brouns G, Scherr M, Battmer K, Kinnon C, et al. High-level transduction and gene expression in hematopoietic repopulating cells using a human immunodeficiency [correction of imunodeficiency] virus type 1-based lentiviral vector containing an internal spleen focus forming virus promoter. Hum Gene Ther. 2002;13:803-13 pubmed
  3. Johnson P, Chung S, Benchimol S. Growth suppression of Friend virus-transformed erythroleukemia cells by p53 protein is accompanied by hemoglobin production and is sensitive to erythropoietin. Mol Cell Biol. 1993;13:1456-63 pubmed
    ..This response to erythropoietin was not accompanied by down-regulation of viral gp55 protein...
  4. Ben David Y, Prideaux V, Chow V, Benchimol S, Bernstein A. Inactivation of the p53 oncogene by internal deletion or retroviral integration in erythroleukemic cell lines induced by Friend leukemia virus. Oncogene. 1988;3:179-85 pubmed
    ..The 5' end of the deletion originates within exon 4 and extends 3' to within the eighth intron. The significance of these findings with regard to the multi-stage nature of Friend virus induced erythroleukemia is discussed...
  5. Starck J, Doubeikovski A, Sarrazin S, Gonnet C, Rao G, Skoultchi A, et al. Spi-1/PU.1 is a positive regulator of the Fli-1 gene involved in inhibition of erythroid differentiation in friend erythroleukemic cell lines. Mol Cell Biol. 1999;19:121-35 pubmed
    ..1 transcription factor in SFFV-transformed cell lines. We further suggest that deregulated synthesis of Fli-1 may trigger a common mechanism contributing to erythroleukemia induced by either SFFV or F-MuLV...
  6. Yamamura Y, Senda H, Kageyama Y, Matsuzaki T, Noda M, Ikawa Y. Erythropoietin and Friend virus gp55 activate different JAK/STAT pathways through the erythropoietin receptor in erythroid cells. Mol Cell Biol. 1998;18:1172-80 pubmed
  7. Jelacic T, Thompson D, Hanson C, Cmarik J, Nishigaki K, Ruscetti S. The tyrosine kinase sf-Stk and its downstream signals are required for maintenance of friend spleen focus-forming virus-induced fibroblast transformation. J Virol. 2008;82:419-27 pubmed
    ..Our results indicate that sf-Stk is a molecular endpoint of transformation that could be targeted directly or with agents against its downstream effectors...
  8. Rulli K, Yugawa T, Hanson C, Thompson D, Ruscetti S, Nishigaki K. Ex vivo and in vivo biological effects of a truncated form of the receptor tyrosine kinase stk when activated by interaction with the friend spleen focus-forming virus envelope glycoprotein or by point mutation. J Virol. 2004;78:4573-81 pubmed
  9. Moreau Gachelin F, Tavitian A, Tambourin P. Spi-1 is a putative oncogene in virally induced murine erythroleukaemias. Nature. 1988;331:277-80 pubmed
    ..A 4.0-kilobase messenger RNA was detected in rearranged tumours. No Spi-1 rearrangement was detected in other virally induced myeloid, lymphoid or erythroid tumours tested...
  10. Chung S, Wolff L, Ruscetti S. Transmembrane domain of the envelope gene of a polycythemia-inducing retrovirus determines erythropoietin-independent growth. Proc Natl Acad Sci U S A. 1989;86:7957-60 pubmed
    ..Our results indicate that the 113-base-pair Fok I-Cla I fragment, which encodes primarily the transmembrane domain of the envelope protein, determines erythropoietin-independent growth...
  11. Nishigaki K, Hanson C, Ohashi T, Spadaccini A, Ruscetti S. Erythroblast transformation by the friend spleen focus-forming virus is associated with a block in erythropoietin-induced STAT1 phosphorylation and DNA binding and correlates with high expression of the hematopoietic phosphatase SHP-1. J Virol. 2006;80:5678-85 pubmed
    ..Our studies suggest that SFFV-infected erythroid cells become transformed when differentiation signals activated by STAT1/3 are blocked due to high SHP-1 levels induced by inappropriate expression of the PU.1 protein...
  12. D Andrea A, Yoshimura A, Youssoufian H, Zon L, Koo J, Lodish H. The cytoplasmic region of the erythropoietin receptor contains nonoverlapping positive and negative growth-regulatory domains. Mol Cell Biol. 1991;11:1980-7 pubmed
    ..Only the functional EPO-R mutants were activated by the gp55, however, suggesting that gp55- and EPO-mediated signaling occur via a similar mechanism. ..
  13. Hangoc G, Lu L, Oliff A, Gillis S, Hu W, Bicknell D, et al. Modulation of Friend virus infectivity in vivo by administration of purified preparations of human lactoferrin and recombinant murine interleukin-3 to mice. Leukemia. 1987;1:762-4 pubmed
    ..recombinant murine interleukin-3 (IL-3) were assessed in vivo for their effects on replication of spleen focus forming viruses (SFFV) in spleens of DBA/2 mice injected with the polycythemia-inducing strain of the Friend virus ..
  14. Bobkova M, Stitz J, Engelstädter M, Cichutek K, Buchholz C. Identification of R-peptides in envelope proteins of C-type retroviruses. J Gen Virol. 2002;83:2241-6 pubmed
    ..Our data suggest that activation of membrane fusion by R-peptide cleavage is a common mode in C-type retroviruses. ..
  15. Sinkovics J, Gonzalez F, Gyorkey F. Viral expressions in Reed-Sternberg cells. Leukemia. 1992;6 Suppl 3:49S-53S pubmed
    ..Derivation of RS cells from IR cells and B and/or T lymphocytes as natural hybridomas offers plausible explanation for all the features of RS cells. ..
  16. Shen R, Lu L, Kaiser H, Broxmeyer H. Curative effect of split low dosage total-body irradiation on murine AIDS induced by Friend virus: the results and the possible mechanism. In Vivo. 1996;10:191-9 pubmed
    ..It would be of interest to see if this type of treatment, which was well tolerated by mice, would be beneficial in other types of virally induced disease, including AIDS...
  17. Yamamura Y, Senda H, Noda M, Ikawa Y. Activation of the JAK1-STAT5 pathway by binding of the Friend virus gp55 glycoprotein to the erythropoietin receptor. Leukemia. 1997;11 Suppl 3:432-4 pubmed
    ..These results indicate that JAK1 is involved in the gp55/EPOR signaling but STAT5 is not playing an essential role in the growth of those erythroid cells. ..
  18. Yin P, Hu W. Insertion of sequences into the 3' untranslated region of a replication-competent spleen necrosis virus vector disrupts env gene expression. Arch Virol. 1999;144:73-87 pubmed
    ..These results suggest that the function of a cis-acting element distinct from the constitutive transport element is disrupted by the inserted sequences into the 3' untranslated region of SNV. ..
  19. Kilpatrick D, Srinivas R, Compans R. The spleen focus-forming virus envelope glycoprotein is defective in oligomerization. J Biol Chem. 1989;264:10732-7 pubmed
    ..Only those molecules that do form oligomeric structures are transported to the Golgi complex and undergo further oligosaccharide processing, and transport to the cell surface. ..
  20. Yugawa T, Amanuma H. Impaired activation and binding of the erythropoietin receptor by a mutant gp55 of Friend spleen focus-forming virus, which has a cytoplasmic domain. Virology. 1998;246:232-40 pubmed
  21. Priel E, Aflalo E, Chechelnitsky G, Benharroch D, Aboud M, Segal S. Inhibition of retrovirus-induced disease in mice by camptothecin. J Virol. 1993;67:3624-9 pubmed
    ..This ability of CPT to inhibit retrovirus-induced disease in vivo without causing any apparent toxic side effects suggests its application as a legitimate remedy for the treatment of retroviral diseases. ..
  22. Amanuma H, Watanabe N, Nishi M, Ikawa Y. Requirement of the single base insertion at the 3' end of the env-related gene of Friend spleen focus-forming virus for pathogenic activity and its effect on localization of the glycoprotein product (gp55). J Virol. 1989;63:4824-33 pubmed
  23. Jiang A, Fisher H, Pomerantz R, Dornburg R. A genetically engineered spleen necrosis virus-derived retroviral vector that displays the HIV type 1 glycoprotein 120 envelope peptide. Hum Gene Ther. 1999;10:2627-36 pubmed
  24. Hino M, Tojo A, Misawa Y, Morii H, Takaku F, Shibuya M. Unregulated expression of the erythropoietin receptor gene caused by insertion of spleen focus-forming virus long terminal repeat in a murine erythroleukemia cell line. Mol Cell Biol. 1991;11:5527-33 pubmed
    ..It is possible that overexpression of EPOR by viral promoter insertion will confer growth advantage to an F-SFFVP-infected erythroid progenitor cell, leading to positive clonal selection through further leukemogenic steps. ..
  25. Ruscetti S. Deregulation of erythropoiesis by the Friend spleen focus-forming virus. Int J Biochem Cell Biol. 1999;31:1089-109 pubmed
    ..By understanding how SFFV can deregulate erythropoiesis, we may gain insights into the causes and treatment of related diseases in man. ..
  26. Umehara D, Watanabe S, Ochi H, Anai Y, Ahmed N, Kannagi M, et al. Role of phosphatidylinositol 3-kinase in friend spleen focus-forming virus-induced erythroid disease. J Virol. 2010;84:7675-82 pubmed publisher
    ..These results indicate that p85alpha may regulate sf-Stk-dependent erythroid proliferation induced by SFFV as well as stress-induced erythroid hyperplasia. ..
  27. Ruscetti S, Ruscetti F. Apparent Epo-independence of erythroid cells infected with the polycythemia-inducing strain of Friend spleen focus-forming virus is not due to Epo production or change in number or affinity of Epo receptors. Leukemia. 1989;3:703-7 pubmed
  28. Wei Y, Mikawa T. Fate diversity of primitive streak cells during heart field formation in ovo. Dev Dyn. 2000;219:505-13 pubmed
  29. Srinivas R, Kilpatrick D, Tucker S, Rui Z, Compans R. The hydrophobic membrane-spanning sequences of the gp52 glycoprotein are required for the pathogenicity of Friend spleen focus-forming virus. J Virol. 1991;65:5272-80 pubmed
    ..The results also indicate that the transport defect of SFFV gp52 is due to structural features of the ectodomain of the molecule. ..
  30. Showers M, Moreau J, Linnekin D, Druker B, D Andrea A. Activation of the erythropoietin receptor by the Friend spleen focus-forming virus gp55 glycoprotein induces constitutive protein tyrosine phosphorylation. Blood. 1992;80:3070-8 pubmed
    ..In conclusion, a 97-Kd protein found in two murine cell lines is tyrosine-phosphorylated in response to multiple growth factors and viral oncoproteins, and appears to be a central phosphoprotein in signal transduction. ..
  31. Wang Y, Kayman S, Li J, Pinter A. Erythropoietin receptor (EpoR)-dependent mitogenicity of spleen focus-forming virus correlates with viral pathogenicity and processing of env protein but not with formation of gp52-EpoR complexes in the endoplasmic reticulum. J Virol. 1993;67:1322-7 pubmed
  32. Watanabe N, Nishi M, Ikawa Y, Amanuma H. Conversion of Friend mink cell focus-forming virus to Friend spleen focus-forming virus by modification of the 3' half of the env gene. J Virol. 1991;65:132-7 pubmed
    ..The results indicated that the dualtropic env-specific sequence was essential to pathogenic activity. ..
  33. Longmore G, Pharr P, Lodish H. A constitutively activated erythropoietin receptor stimulates proliferation and contributes to transformation of multipotent, committed nonerythroid and erythroid progenitor cells. Mol Cell Biol. 1994;14:2266-77 pubmed
    ..The sites of proviral integration in clonal cell lines are distinct from those in SFFV-derived lines. ..
  34. Hoatlin M, Kozak S, Spiro C, Kabat D. Amplified and tissue-directed expression of retroviral vectors using ping-pong techniques. J Mol Med (Berl). 1995;73:113-20 pubmed
    ..Factors that limit tissue-specific expression are reviewed. ..
  35. Bestwick R, Kozak S, Kabat D. Overcoming interference to retroviral superinfection results in amplified expression and transmission of cloned genes. Proc Natl Acad Sci U S A. 1988;85:5404-8 pubmed
    ..The amplified growth hormone was properly processed as indicated by immunoblot analyses. A vector is described (pSFF) that is exceptionally active in coculture amplification. ..
  36. Itoh K, Friel J, Kluge N, Kina T, Kondo Takaori A, Kawamata S, et al. A novel hematopoietic multilineage clone, Myl-D-7, is stromal cell-dependent and supported by an alternative mechanism(s) independent of stem cell factor/c-kit interaction. Blood. 1996;87:3218-28 pubmed
    ..Myl-D-7 can thus be used as an indicator cell for unknown factors that may provide stromal cell support...
  37. Kishi A, Chiba T, Sugiyama M, Machide M, Nagata Y, Amanuma H, et al. Erythropoietin receptor binds to Friend virus gp55 through other membrane components. Biochem Biophys Res Commun. 1993;192:1131-8 pubmed
  38. Yang Y, Tojo A, Watanabe N, Amanuma H. Oligomerization of Friend spleen focus-forming virus (SFFV) env glycoproteins. Virology. 1990;177:312-6 pubmed
    ..These oligomers could be detected in various FV-infected erythroleukemia cell lines, as well as in the spleen cells of FV-induced erythroleukemic mice, suggesting that oligomerization is an intrinsic feature of SFFV env glycoproteins. ..
  39. Hoatlin M, Kabat D. Host-range control of a retroviral disease: Friend erythroleukemia. Trends Microbiol. 1995;3:51-7 pubmed
    ..Some of these genes limit helper-virus replication, target-cell (erythroblast) pools or immune responses. At least one host gene appears to block the viral oncoprotein...
  40. Zhang L, Lemarchandel V, Romeo P, Ben David Y, Greer P, Bernstein A. The Fli-1 proto-oncogene, involved in erythroleukemia and Ewing's sarcoma, encodes a transcriptional activator with DNA-binding specificities distinct from other Ets family members. Oncogene. 1993;8:1621-30 pubmed
    ..Furthermore, we have identified an octanucleotide core sequence that is required in vitro for optimal binding of Fli-1 to the Drosophila E74 target and the promoter sequence of the human GPIIB gene...
  41. Afrikanova I, Yeh E, Bartos D, Watowich S, Longmore G. Oncogene cooperativity in Friend erythroleukemia: erythropoietin receptor activation by the env gene of SFFV leads to transcriptional upregulation of PU.1, independent of SFFV proviral insertion. Oncogene. 2002;21:1272-84 pubmed
  42. Ohashi T, Masuda M, Ruscetti S. Constitutive activation of Stat-related DNA-binding proteins in erythroid cells by the Friend spleen focus-forming virus. Leukemia. 1997;11 Suppl 3:251-4 pubmed
    ..Although it has been shown that Epo activates Stat proteins through Jak2 kinase, our results suggest that the SFFV-induced Stat protein activation is Jak2-independent...
  43. Sima P, Smahel M, Jelinek F, Vonka V. DNA vaccine against Friend erythroleukaemia virus. Folia Biol (Praha). 2002;48:43-50 pubmed
    ..The FV type A or P was used as a challenge. The immunization with gag- and env-derived vaccines resulted in protective immunity in a high proportion of mice...
  44. Moreau Gachelin F. Multi-stage Friend murine erythroleukemia: molecular insights into oncogenic cooperation. Retrovirology. 2008;5:99 pubmed publisher
    ..Coupling of insights from studies on the Friend erythroleukemia with knowledge on AML might allow a better understanding of the molecular mechanisms involved in the evolution of leukemia in mice and men...
  45. Hoatlin M, Kozak S, Lilly F, Chakraborti A, Kozak C, Kabat D. Activation of erythropoietin receptors by Friend viral gp55 and by erythropoietin and down-modulation by the murine Fv-2r resistance gene. Proc Natl Acad Sci U S A. 1990;87:9985-9 pubmed
    ..These results have important implications for understanding signal transduction by EpoR and the role of host genetic variation in controlling susceptibility to an oncogenic protein...
  46. Muenchau D, Ruscetti S, Anderson W. Sequences present in a small region of the AKV virus envelope gene determine the efficiency with which pseudotyped spleen focus-forming virus infects erythroid target cells. Virology. 1992;186:161-6 pubmed
  47. Scher W, Jing Y, Lu M, Bishop D, Scher B. Sequences of polycythemia-type Friend spleen focus-forming virus in clone-745-derived mouse erythroleukemia cells. Arch Virol. 2009;154:895-8 pubmed publisher
    ..Sequence analysis demonstrates that they contain the polycythemia-type virus and not the anemia-type virus...
  48. Ulmer J, Palade G. Effects of brefeldin A on the processing of viral envelope glycoproteins in murine erythroleukemia cells. J Biol Chem. 1991;266:9173-9 pubmed
  49. Tschernutter M, Schlichtenbrede F, Howe S, Balaggan K, Munro P, Bainbridge J, et al. Long-term preservation of retinal function in the RCS rat model of retinitis pigmentosa following lentivirus-mediated gene therapy. Gene Ther. 2005;12:694-701 pubmed
    ..This study demonstrates the potential of gene therapy approaches for the treatment of retinal degenerations caused by defects specific to the RPE and supports the use of lentiviral vectors for the treatment of such disorders...
  50. Marusich E, Parveen Z, Strayer D, Mukhtar M, Dornburg R, Pomerantz R. Spleen necrosis virus-based vector delivery of anti-HIV-1 genes potently protects human hematopoietic cells from HIV-1 infection. Virology. 2005;332:258-71 pubmed
  51. Ruscetti S. Erythroleukaemia induction by the Friend spleen focus-forming virus. Baillieres Clin Haematol. 1995;8:225-47 pubmed
  52. Ikawa Y. Pathogenesis of Friend leukemia virus. Leukemia. 1997;11 Suppl 3:152-4 pubmed
    ..JAK1 and STAT5 were constitutively tyrosine-phosphorylated but the DNA binding activity of STAT5 was not induced...
  53. Tumas D, Spangrude G, Brooks D, Williams C, Chesebro B. High-frequency cell surface expression of a foreign protein in murine hematopoietic stem cells using a new retroviral vector. Blood. 1996;87:509-17 pubmed
    ..The multilineage, high-frequency expression observed suggests that pSFF may be useful in gene therapy directed at hematopoietic stem cells and their differentiated progeny...
  54. Rau S, Geyer R, Friedrich R. The role of gp55 N-glycosylation in pathogenesis of Friend spleen focus-forming virus. J Gen Virol. 1993;74 ( Pt 4):699-705 pubmed
    ..Furthermore, when site 3 was changed, a new product appeared which seemed to have acquired a carbohydrate chain at a position normally not glycosylated, presumably at position Asn378...
  55. Nishigaki K, Hanson C, Jelacic T, Thompson D, Ruscetti S. Friend spleen focus-forming virus transforms rodent fibroblasts in cooperation with a short form of the receptor tyrosine kinase Stk. Proc Natl Acad Sci U S A. 2005;102:15488-93 pubmed
  56. Volker J, Geyer H, Geyer R. Glycosylation of glycoprotein 55 encoded by the anaemia-inducing strain of Friend spleen focus-forming virus. Glycoconj J. 1994;11:133-9 pubmed
    ..1988) J Biol Chem 263:3762-71]. Hence, our results demonstrate that the different intracellular processing and transport of the primary F-SFFVA env product cannot be attributed to aberrant trimming of its oligomannose type glycans...
  57. Pargmann D, Yücel R, Kosan C, Saba I, Klein Hitpass L, Schimmer S, et al. Differential impact of the transcriptional repressor Gfi1 on mature CD4+ and CD8+ T lymphocyte function. Eur J Immunol. 2007;37:3551-63 pubmed
  58. Barber D, DeMartino J, Showers M, D Andrea A. A dominant negative erythropoietin (EPO) receptor inhibits EPO-dependent growth and blocks F-gp55-dependent transformation. Mol Cell Biol. 1994;14:2257-65 pubmed
    ..In conclusion, the EPO-R(T) polypeptide is a dominant negative polypeptide which specifically interferes with the early stages of EPO-R-mediated signal transduction and which prevents Friend virus transformation of erythroblasts...
  59. Watanabe N, Nishi M, Ikawa Y, Amanuma H. A deletion in the Friend spleen focus-forming virus env gene is necessary for its product (gp55) to be leukemogenic. J Virol. 1990;64:2678-86 pubmed
    ..These results indicate that for the pathogenic activity of gp55, a certain env deletion is necessary which causes production of a gp70-p15E fusion protein with an absence of at least the N-terminal one-third of the p15E-coding region...
  60. Hoatlin M, Gomez Lucia E, Lilly F, Beckstead J, Kabat D. Origin and rapid evolution of a novel murine erythroleukemia virus of the spleen focus-forming virus family. J Virol. 1998;72:3602-9 pubmed
    ..Our results suggest that SFFV-related viruses can form in mice by recombination of retroviruses with genomic and helper virus sequences and that these novel viruses then evolve to become increasingly pathogenic...
  61. Lu L, Shen R, Zhou S, Wu B, Kim Y, Lin Z, et al. Efficacy of recombinant human macrophage colony-stimulating factor in combination with whole-body hyperthermia in the treatment of mice infected with the polycythemia-inducing strain of the Friend virus complex. Exp Hematol. 1991;19:804-9 pubmed
    ..These results suggest the possibility that M-CSF may have a therapeutic effect in combination with WBH in the in vivo treatment of certain hematologic malignancies and/or retroviral infections...
  62. Blair D, Athanasiou M. Ets and retroviruses - transduction and activation of members of the Ets oncogene family in viral oncogenesis. Oncogene. 2000;19:6472-81 pubmed
    ..This review provides an overview of the role of ETS genes in retrovirally induced neoplasia, their possible mechanisms of action, and how these viral studies relate to current knowledge of the functions of these genes in hematopoiesis...
  63. Ahlers N, Hunt N, Just U, Laker C, Ostertag W, Nowock J. Selectable retrovirus vectors encoding Friend virus gp55 or erythropoietin induce polycythemia with different phenotypic expression and disease progression. J Virol. 1994;68:7235-43 pubmed
    ..These data suggest that Epo and gp55 differentially affect proliferation and differentiation. Gp55 appears to promote proliferation over differentiation, whereas Epo preferentially drives differentiation...
  64. Ben David Y, Lavigueur A, Cheong G, Bernstein A. Insertional inactivation of the p53 gene during friend leukemia: a new strategy for identifying tumor suppressor genes. New Biol. 1990;2:1015-23 pubmed
    ..Thus, it may be possible to identify additional genes of this class by characterizing chromosomal sequences that are adjacent to common sites of retroviral integration in tumors...
  65. Ferro F, Kozak S, Hoatlin M, Kabat D. Cell surface site for mitogenic interaction of erythropoietin receptors with the membrane glycoprotein encoded by Friend erythroleukemia virus. J Biol Chem. 1993;268:5741-7 pubmed
    ..Our results support the hypothesis that activation of EpoR by the SFFV env glycoprotein occurs exclusively on cell surfaces...
  66. Yugawa T, Amanuma H. Pathogenicity of a mutant friend spleen focus-forming virus encoding an Env-like membrane glycoprotein (gp55) with substitution by a xenotropic murine leukemia virus Env gp70 sequence. Microbiol Immunol. 1998;42:335-9 pubmed
    ..XE gp55 displayed almost the same biological activities as the wild-type gp55, excluding the above possibility...
  67. Srinivas R, Tucker S, Kilpatrick D, Compans R. A 585-bp deletion found in the spleen focus-forming virus (SFFV) env gene is responsible for the defective intracellular transport of SFFV gp52. Virology. 1992;188:181-92 pubmed
    ..The results indicate that the 585-bp deletion, although essential, is not the sole determinant of SFFV-induced disease in adult mice...
  68. Baum C, Hunt N, Hildinger M, Eckert H, Zaehres H, Richters A, et al. cis-Active elements of Friend spleen focus-forming virus: from disease induction to disease prevention. Acta Haematol. 1998;99:156-64 pubmed
    ..Moreover they might have therapeutic potential...
  69. Nishigaki K, Hanson C, Thompson D, Yugawa T, Ruscetti S. Activation of the Jun N-terminal kinase pathway by friend spleen focus-forming virus and its role in the growth and survival of friend virus-induced erythroleukemia cells. J Virol. 2005;79:12752-62 pubmed
    ..These data suggest that JNK plays an important role in cell proliferation and/or the survival of erythroleukemia cells...
  70. Xu X, Yamamura Y, Tsukada T, Yoshida M, Senda H, Nagayoshi M, et al. A mouse erythroleukemia cell line possessing friend spleen focus-forming virus gp55 transgene and temperature-sensitive mutant p53 gene. Jpn J Cancer Res. 1995;86:284-91 pubmed
    ..This non-virus-producing, mouse erythroleukemia cell line will be useful for the study of mutated p53 function during the induction of erythrodifferentiation or apoptotic change...
  71. Van der Gaag H, Axelrad A. Friend virus replication in normal and immunosuppressed C57BL/6 mice. Virology. 1990;177:837-9 pubmed
    ..2 monoclonal antibody iv before FV infection permitted continued replication of SFFV in these animals. This finding strongly supports the hypothesis that SFFV replication in C57BL/6 mice is restricted by a T cell-mediated immune response...
  72. Strube K, Lottspeich F, Geyer R. Glycosylation of glycoproteins 52 and 65 encoded by the polycythemia-inducing strain of Friend spleen focus-forming virus. Isolation of glycopeptides containing individual glycosylation sites. Eur J Biochem. 1989;184:119-24 pubmed
    ..In gp65, however, asparagine residue 11 is almost exclusively substituted by complete, fucosylated N-acetyllactosaminic oligosaccharides, whereas asparagine residue 26 carries oligomannosidic or truncated N-acetyllactosaminic glycans...
  73. Gomez Lucia E, Zhi Y, Nabavi M, Zhang W, Kabat D, Hoatlin M. An array of novel murine spleen focus-forming viruses that activate the erythropoietin receptor. J Virol. 1998;72:3742-50 pubmed
  74. Johnson P, Benchimol S. Friend virus induced murine erythroleukaemia: the p53 locus. Cancer Surv. 1992;12:137-51 pubmed
    ..Further studies of the mechanisms by which wild type and mutant p53 affect the growth of p53 negative FCLs may reveal important biochemical properties of p53 in relation to cell cycle control and differentiation of erythroid cells...
  75. Lu L, Shen R, Zhou S, Srivastava C, Harrington M, Miyazawa K, et al. Synergistic effect of human lactoferrin and recombinant murine interferon-gamma on disease progression in mice infected with the polycythemia-inducing strain of the Friend virus complex. Int J Hematol. 1991;54:117-24 pubmed
    ..This information might be of significance as a potential therapy for patients with leukemia and those infected with retroviruses...
  76. Ketteler R, Glaser S, Sandra O, Martens U, Klingmuller U. Enhanced transgene expression in primitive hematopoietic progenitor cells and embryonic stem cells efficiently transduced by optimized retroviral hybrid vectors. Gene Ther. 2002;9:477-87 pubmed
  77. Ohnishi N, Itoh K, Itoh Y, Baum C, Higashitsuji H, Yamaguchi K, et al. High expression of transgenes mediated by hybrid retroviral vectors in hepatocytes: comparison of promoters from murine retroviruses in vitro and in vivo. Gene Ther. 2002;9:303-6 pubmed
    ..Thus, FMEV-type vectors may represent a novel type of vectors for human gene therapy with hepatocytes...
  78. Friedrich R, Friedrich U, Maennle G. Construction and properties of an "artificial" spleen focus-forming virus. Virology. 1991;183:343-50 pubmed
    ..We therefore conclude that the modified membrane anchor of gp55 and the change caused by the large deletion are the essential determinants of the high pathogenicity of SFFV...
  79. Li Z, Blair M, Thorner L. PG-4 cell plaque assay for xenotropic murine leukemia virus. J Virol Methods. 1999;81:47-53 pubmed
    ..A linear response to dilution was observed for wells containing 5-70 plaques. The limit of quantitation was 10 PFU/ml. Using six wells per dilution, the 95% confidence limit of the grand mean titer was within +/-0.5 log10...
  80. Zelinskyy G, Dietze K, Hüsecken Y, Schimmer S, Nair S, Werner T, et al. The regulatory T-cell response during acute retroviral infection is locally defined and controls the magnitude and duration of the virus-specific cytotoxic T-cell response. Blood. 2009;114:3199-207 pubmed publisher