Reliability of BCR-ABL measurement with a small number of cells. RNA extracted from K562 cells was diluted 1:100 into RNA from HL60 cells. Ten-fold serial dilutions were performed to obtain 200 ng, 20 ng, 2 ng, and 0.2 ng, equivalent to 20 000, 2000, 200, and 20 cells, respectively, which were then used for Q-PCR analysis of BCR-ABL and BCR. (A) BCR-ABL and BCR measurements following Q-PCR of different dilutions of RNA are shown. (B) The ratio of BCR-ABL to BCR at the different dilutions is shown.