Mice expressing a truncated form of the EpoR exhibit a delay in the progression of F-MuLV–induced erythroleukemia. (A) Kinetics of erythroleukemia development in H/H and Tr/Tr mice. Age-matched H/H (n = 16) and Tr/Tr (n = 24) neonates were infected with F-MuLV. The survival rates of F-MuLV–infected H/H and Tr/Tr mice were calculated according to the Kaplan-Meier method using a Mann-Whitney U test with 2-sided P values and a significant difference reflecting P < .005. (B) Hematocrit levels of H/H and Tr/Tr mice during F-MuLV–induced erythroleukemia development. Hematocrit levels (%) were measured on a weekly basis in H/H-infected (n = 16) and Tr/Tr-infected (n = 24) mice. *Significant difference on week 11 (P < .005). Error bars represent ± SD. (C) Southern blot analysis of Fli-1 rearrangement in spleen cells isolated from F-MuLV–infected H/H and Tr/Tr mice. (D) Western blot analysis of Fli-1 protein expression in primary cells from H/H and Tr/Tr tumors compared with the F-MuLV–induced erythroleukemia cell line, CB3. (E) Fli-1 protein expression in normal spleens isolated from H/H and Tr/Tr mice, compared with CB3 cells.