Figure 3.

Oncogenic cooperation in murine erythroleukemia. During Friend acute erythroleukemia, the early expansion of erythroid progenitors is due to the activation of EpoR and sf-STK by the viral gp55. The blastic crisis is associated with the overexpression of the transcription factor Spi-1/PU.1, occurring by insertional mutagenesis due to SFFV. During erythroleukemia progression in spi-1 transgenic mice, the initial oncogenic event is the overexpression of Spi-1/PU.1 by germinal mutation that induces a differentiation arrest of the proerythroblast. The blastic crisis is associated with activating mutations in the Kit gene that promote the Epo-independent proliferation and survival of the malignant proerythroblast.