Growth-inhibitory effects of the chemopreventive agent indole-3-carbinol are increased in combination with the polyamine putrescine in the SW480 colon tumour cell line

Table 1 Effect of I3C alone and in combination with putrescine on intracellular polyamine levels at 24, 96 and 168 hours.

Treatment	Cell no. as % Control (SD)	Putrescine (SD)	Spermidine (SD)	Spermine (SD)
24 hour
Control	100.0 (0.0)	0.48 (0.31)	1.62 (0.55)	2.10 (0.98)
I3C 100	89.1 (19.8)	0.31 (0.09)	1.79 (0.51)	2.25 (1.21)
I3C 175	87.9 (29.2)	0.23 (0.06)*	1.32 (0.36)	1.54 (0.19)
I3C 250	77.4 (32.7)	0.19 (0.04)*	2.17 (0.98)	2.73 (1.86)
I3C 500	54.2 (26.6)	0.14 (0.07)*	1.57 (0.60)	2.74 (1.82)
C + P20	96.9 (23.5)	0.64 (0.26)	2.17 (1.06)	2.41 (1.53)
C + P50	90.0 (42.1)	0.72 (0.27)*	2.34 (1.48)	2.59 (1.93)
I + P20	76.2 (26.3)	0.69 (0.29)	2.93 (1.57)*	3.06 (1.99)
I + P50	76.1 (35.0)	0.54 (0.16)	1.86 (0.49)	1.94 (0.65)
96 hour
Control	100.0 (0.0)	0.08 (0.04)	0.79 (0.30)	1.25 (0.38)
I3C 100	98.7 (8.5)	0.13 (0.09)	1.11 (0.40)	1.87 (0.47)
I3C 175	58.9 (3.8)	0.13 (0.10)	0.98 (0.29)	2.18 (0.79)*
I3C 250	24.9 (6.1)	0.15 (0.11)	0.77 (0.36)	2.03 (1.17)*
I3C 500	13.9 (6.0)	nd	0.62 (0.32)	1.34 (0.45)
C + P20	96.6 (12.4)	0.13 (0.03)	0.84 (0.15)	1.15 (0.12)
C + P50	79.2 (14.3)	0.32 (0.18)*	1.47 (0.15)*	1.98 (0.34)
I + P20	28.1 (22.6)	0.17 (0.09)	1.25 (0.23)*	2.42 (0.21)*
I + P50	17.9 (2.9)	0.11 (0.02)	0.80 (0.21)	1.54 (0.48)
168 hour
Control	100.0 (0.0)	0.04 (0.02)	0.46 (0.07)	0.76 (0.17)
I3C 100	104.0 (9.9)	0.03 (0.01)	0.57 (0.25)	1.22 (0.32)
I3C 175	57.1 (9.5)	0.05 (0.03)	0.62 (0.28)	1.99 (0.96)*
I3C 250	31.1 (20.2)	0.07 (0.01)	0.87 (0.54)	2.93 (0.72)*
I3C 500	4.5 (5.2)	nd	nd	nd
C + P20	107.2 (4.8)	0.03 (0.01)	0.48 (0.04)	0.83 (0.15)
C + P50	104.5 (10.1)	0.06 (0.04)	0.67 (0.10)	1.08 (0.19)
I + P20	6.0 (5.5)	nd	0.91 (0.55)	3.11 (1.59)*
I + P50	3.0 (0.7)	nd	0.90 (0.56)	2.26 (1.42)*

Cells were treated with I3C alone or in combination with putrescine, and intracellular polyamines determined as described in the Methods Section. Data shown for cell numbers are expressed as a % Control, and polyamine levels are nmol/10⁶ cells. All values are means with SD in brackets. nd = values not determined. * indicates a value that is significantly different to the control value at that time point.