TABLE 2.

Cell pool analysis of BCR-ABL mutant cells with pre-expansion

Expected number of wells receiving mutant cells was calculated by assuming stable “pre-existing” mutant cells were randomly distributed according to Poisson distribution.

Starting KCL-22 cell number	1 × 105
Number of wells that cells were seeded	24
Calculated mutant cell number/well	1
Expected number of wells receiving mutant cells (total number of wells)	15 (24)a
Average cell number/well after 10-day expansion	1.8 × 106
Actual number of resistant colonies under 5 μm imatinib detected for cells from each well (number of wells)	1 (1)
	2 (1)
	51 (1)
	0 (21)
Actual number of wells having mutant cells (total number of wells)	3 (24)a
p value for expected versus actual number of wells having mutant cells	0.0008

^a The assumed mutant frequency under 5 μm imatinib was 2.5 × 10⁻⁴ as described in the text or 25 cells in 1 × 10⁵ KCL-22 cells. p value was calculated with two-tailed Fisher exact test.