Table 1. Cell viability of HT-29, BR100 and BR200 cell lines over a 40-day period.

	Parental		BR100				BR200
Days removed from BTZ	IC50 (µM)		IC50 (µM)		Fold Resistance		IC50 (µM)		Fold Resistance
	BTZ	CFZ	BTZ	CFZ	BTZ	CFZ	BTZ	CFZ	BTZ	CFZ
3	0.013	0.026	0.41	0.07	32×	2.8×	0.44	0.1	34×	3.8×
	(0.010–0.018)	(0.024–0.034)	(0.36–0.48)	(0.069–0.075)			(0.34–0.59)	(0.10–0.20)
14	0.011	0.031	0.34	0.09	26×	2.9×	0.36	0.11	28×	3.5×
	(0.011–0.016)	(0.023–0.033)	(0.30–0.37)	(0.077–0.093)			(0.30–0.44)	(0.099–0.12)
20	0.015	0.035	0.42	0.09	28×	2.6×	0.68	0.15	45×	4.3×
	(0.012–0.018)	(0.026–0.037)	(0.32–0.54)	(0.069–0.11)			(0.61–0.74)	(0.13–0.17)
40	0.013	0.037	0.62	0.17	48×	4.6×	0.82	0.15	63×	4.1×
	(0.011–0.015)	(0.025–0.042)	(0.52–0.72)	(0.16–0.21)			(0.74–0.90)	(0.14–0.17)

The mean IC₅₀ values are presented with 95% confidence intervals from 2 independent experiments in parenthesis.