Sensitivity of detection of DNA junctional fragment. (a) All six samples contained 1 × 106 cells each, but with a ten-fold serial dilution of K562 cells mixed with an appropriate number of HCT116 cells. The numbers of K562 were 106 (no dilution), 105 (1:10), 104 (1:100), 103 (1:1,000), 102 (1:10,000) and 0. Total genomic DNA (100 ng) was used as a template for RT-PCR using PCR primer set K562DF3 and R3. The quantitative PCR signal was normalized to PCR product from the PCNA locus. Simultaneously, we isolated total RNA with TRIzol. cDNA reverse transcribed by SuperScript III from 100 ng of total RNA was used as a template for RT-PCR. (b) Genomic DNA and RNA were extracted from 106 formalin fixed KU812 cells. RT-PCR (primer sets KU812DF3, R3 and BCRe13F1, ABL1a2R1) was performed using DNA or cDNA from 104 cells and normalized to DNA or cDNA from 103 freshly prepared cells. (c) DNA and RNA were prepared from KU812 cell culture medium. DNA or cDNA from 100 μl medium was used for the assay and normalized as above.