TABLE 2

Comparison of IC₅₀ values among the cell lines resistant to antitumor nucleosides

Cell Line	Selection Nucleoside^a	EUrd			ECyd
Cell Line	Selection Nucleoside^a			μM	Fold^b	μM	Fold^b
HT-1080		0.02	1	0.01	1
HT-1080/EUrd	EUrd	>100	>5000	24.2	2420
HT-1080/ECyd	ECyd	>100	>5000	8.30	830
NUGC-3		1.30	1	0.35	1
NUGC-3/EUrd	EUrd	>100	>76.9	>100	>286
NUGC-3/ECyd	ECyd	>100	>76.9	>100	>286

↵ a Resistant cell lines were established by continuous exposure to EUrd or ECyd.
↵ b Relative resistant ratios were calculated by the following formula: ratio (fold) = (IC₅₀ value in resistant cell)/(IC₅₀ value in parent cell).