Table 2.

Constitutive expression and increase of CD26 at the surface of human colorectal carcinoma cells by anticancer drugs

Cell line	Basal CD26 expression (cpm/105 cells)	Drug treatment
		5-FU	Cis	Vin	MTX
		Maximal increase (% over control)
HT-29	1,300 ± 140	30 ± 5.8**	72 ± 26***	41 ± 10**	26 ± 6.4**
T84	780 ± 69	84 ± 14*	61 ± 42	78 ± 6.6	73 ± 42
HRT-18	370 ± 64	17 ± 9.1*	19 ± 9.1	23 ± 12	18 ± 9.4**
SW480	55 ± 15	96 ± 58*	90 ± 66	100 ± 59**	170 ± 150
SW620	26 ± 12	36 ± 31	28 ± 30	45 ± 43	53 ± 49

The relative basal cell-surface protein expression for each cell line was summarized from 12–5 independent experiments. Cells were treated with drugs (5-FU, 5-fluorouracil [0.1 – 1,000 μg/mL]; Cis, cisplatin [0.001 – 10 μg/mL]; Vin, vinblastine [0.001 – 10 μg/mL]; MTX, methotrexate [0.1 – 1,000 μg/mL]) and cell surface expression of CD26 was determined by radioimmunobinding assay 48 h later. Maximal up-regulation of CD26 was recorded from 3–7 independent dose–response experiments for each drug and cell line. Data are shown as mean % increases ± SE for the moderate/high CD26-expressing cell lines, and mean numerical increases (cpm/10⁵ cells) ± SE for the low expressers. *, significant increase due to drug, P < 0.05; **, P < 0.01; ***, P < 0.001, using paired t-test