Molecular Analysis and Characterization of Two Myeloid Leukemia Inducing Murine Retroviruses

Murine retroviruses (MuLVs) induce a large variety of hematopoietic tumors through complex mechanisms involving insertional activation of cellular proto-oncogenes in the tumor cell (for review see [1,2]). The type of tumor induced generally depends on sequences located in the viral enhancer [3–5] but also on coding sequences from other regions of the viral genome [6–8]. The Cas-Br-E MuLV is an ecotropic retrovirus that induces hindlimb paralysis in susceptible strains of mice [9]. It also induces mainly non-T, non-B-cell leukemia in infected NIH/Swiss mice [10–12]. The tumor cells show a very undifferentiated blast cell morphology which suggest that they are immature precursors.