Stem/progenitor cells derived from Tr/Tr tumors are sensitive to treatment with SCF. (A) Cell lines derived from H/H (H1, H9) and Tr/Tr (T5, T6) tumors were grown in 10% FBS and in the presence of Epo, SCF, or Epo + SCF. After 3 days of incubation, cells were collected, and the number of viable cells was determined on the indicated days using the trypan blue exclusion assay. (B) RT-PCR analysis of lineage-specific genes using H/H and Tr/Tr cell lines. (C) Fli-1 protein expression in cells derived from H/H and Tr/Tr tumors.