Vector copy number after engraftment and in leukemias. (A) Transgene copy number in the peripheral blood 9 weeks after transplantation measured by quantitative PCR. Lines indicate the median of each group (Student t test, unpaired, 2-sided). (B) Southern blot analysis of genomic DNA from spleens of leukemic mice. Blots were probed for MDR1 and dsRED2 (marker: Lambda DNA/HindIII marker 2). (C) LM-PCR gel electrophoresis (mice 31.2, 29, 40, 44, and 46). The number of amplified PCR fragments corresponds to the number of insertions detected by Southern blot (marker: GeneRuler DNA ladder mix). The internal band represents the PCR product amplified from the viral 3′ LTR.