Prolonged exposure of colon cancer cells to the epidermal growth factor receptor inhibitor gefitinib (Iressa™) and to the antiangiogenic agent ZD6474: Cytotoxic and biomolecular effects

Table 1 AUC and retention time of gefitinib or ZD6474 following incubation for 7 d at 37°C, by HPLC analysis

Drug	Medium	Concentration (µmol/L)	Retentiontime (min)	AUC
Gefitinib	DMSO	100	2.47 ± 0.03	1.30 ± 0.20
	Complete medium	100	2.52 ± 0.05	1.27 ± 0.16
ZD6474	DMSO	100	1.75 ± 0.02	0.88 ± 0.08
	Complete medium	100	1.71 ± 0.04	0.86 ± 0.10

Table 2 IC₅₀ of gefitinib and ZD6474 in HT-29 and LoVo cells at various times of incubation

Exposuretime	Gefitinib (µmol/L)		ZD6474 (µmol/L)
	LoVo cells	HT-29 cells	LoVo cells	HT-29 cells
18 h	48.5 ± 2.5	> 100	16 ± 5.1	80 ± 4.8
1 d	29 ± 3.1	> 100	13 ± 2.6	59 ± 3.6
2 d	16.5 ± 1.5	> 100	8.2 ± 3.8	19 ± 1.8
3 d	7.3 ± 0.9	23.6 ± 4.1	3.5 ± 0.9	10 ± 0.4

Each experiment was conducted in triplicate.

Table 3 Cell cycle and apoptosis modulation after prolonged exposure to gefitinib or ZD6474 in HT-29 and LoVo cells

		LoVo cells		HT-29 cells
	Drug exposure	Apoptosis(%)	G0/G1(%)	Apoptosis(%)	G0/G1(%)
Control		0	74.3 ± 1.3	0	69.5 ± 1.4
Gefitinib	1 wk continuous	10.1 ± 0.5	80.4 ± 1.5	7 ± 0.4	70. 7 ± 1.7
	2 wk continuous	23.2 ± 0.9	87.9 ± 1.3	20 ± 1.2	77.2 ± 2.0
	1 wk intermittent	13.8 ± 0.6	75.4 ± 1.4	6.5 ± 0.3	67.1 ± 1.4
	2 wk intermittent	29.7 ± 0.8	78.0 ± 2.1	18.3 ± 1.8	69.7 ± 1.9
Control		0	74.3 ± 2.1	0	69.5 ± 1.8
ZD6474	1 wk continuous	15.4 ± 0.6	77.6 ± 1.9	7 ± 0.9	71.7 ± 2.1
	2 wk continuous	30.3 ± 0.9	81.8 ± 2.3	15 ± 0.8	75.2 ± 2.4
	1 wk intermittent	18.3 ± 1.3	74.6 ± 2.1	7.3 ± 1.1	70.2 ± 1.8
	2 wk intermittent	29.6 ± 1.5	76.5 ± 1.5	16.4 ± 2.2	72.0 ± 1.7

Each experiment was conducted in triplicate.