Friend leukemia

About: Friend leukemia is a research topic. Over the lifetime, 319 publications have been published within this topic receiving 7463 citations.

Novel host range and cytopathic variant of ecotropic Friend murine leukemia virus.

Abstract: A variant ecotropic Friend murine leukemia virus, F-S MLV, is capable of inducing the formation of large multinucleated syncytia in Mus dunni cells. This cytopathicity resembles that of Spl574 MLV, a novel variant recently isolated from the spleen of a Mus spicilegus mouse neonatally inoculated with Moloney MLV. F-S MLV is an N-tropic Friend MLV that also has the unusual ability to infect hamster cells, which are normally resistant to mouse ecotropic MLVs. Syncytium induction by both F-S MLV and Spl574 is accompanied by the accumulation of large amounts of unintegrated viral DNA, a hallmark of pathogenic retroviruses, but not previously reported for mouse ecotropic gammaretroviruses. Sequencing and site-specific mutagenesis determined that the syncytium-inducing phenotype of F-S MLV can be attributed to a single amino acid substitution (S84A) in the VRA region of the viral env gene. This site corresponds to that of the single substitution previously shown to be responsible for the cytopathicity of Spl574, S82F. The S84A substitution in F-S MLV also contributes to the ability of this virus to infect hamster cells, but Spl574 MLV is unable to infect hamster cells. Because this serine residue is one of the critical amino acids that form the CAT-1 receptor binding site, and because M. dunni and hamster cells have variant CAT-1 receptors, these results suggest that syncytium formation as well as altered host range may be a consequence of altered interaction between virus and receptor.

Study of the cellular proliferation kinetics of friend leukemia.

Abstract: We have studied the kinetic parameters of the polycythemic variety of Friend leukemia using DBA2 mice inoculated with the virus. Proliferation was mainly observed in the erythroblasts of the spleen. The mean duration of the mitotic cycle is 7.6 h and the majority of erythroblasts are in active stages of the cell cycle. The proliferation rate is unaffected even during the hours preceding death. The multiplication of erythroblasts in the spleen results in three different phenomena: 1/3 of the erythroblasts produce short-lived erythrocytes; a very small fraction (1/20) of the proliferation accounts for the slow growth of the spleen and the progressive invasion of the liver and the blood; 2/3 disappear, and this loss is apparently due to massive splenic cellular death.

Enhancement of Viral Gene Expression in Friend Erythroleukemic Cells by 12-O-Tetradecanoylphorbol-13-acetate

Abstract: Tumor-promoting agents are known to inhibit the specific differentiation processes of several animal cell systems in vitro , including the Friend leukemia cell system. We have examined the effect of 12- O -tetradecanoylphorbol-13-acetate (TPA) on the latter system and have investigated its action on Friend virus expression. At a concentration of 16.7 nm, TPA inhibits the dimethyl sulfoxide-induced Friend cell terminal differentiation and, at the same time, enhances the expression of the Friend virus genome, as demonstrated by a 2-fold increase in the amount of reverse transcriptase-containing particles released into the culture fluid and in the levels of virus-specific intracytoplasmic RNA. The greatest effect of TPA is evident after 24 hr of treatment. At this time, TPA exerts also its strongest effect upon the induction of the plasminogen activator. Our results indicate that two specific effects of TPA, i.e. , block of differentiation and induction of plasminogen activator, correlate well in the Friend cell system with an extracellular and intracellular increase in virus expression.