Analysis of F-MuLV integration within the host genome. Genomic DNA from LDSACs (1), leukemic suspension cells (2), HDSACs (3), normal suspension cells (4), NIH-3T3 cells as negative control (5), HB60 leukemic cells as positive control (6), and 1 kbp ladder (7) was extracted. Friend virus env primers were used to amplify the integration site of the virus's env as described in “Materials and methods.”