Table 2. Growth inhibition by SP-G (IC₅₀) and neuropeptide receptor expression in a panel of tumour cell lines.

		Relative NP receptor expression
Cell line	IC50 (μM)	GRPR*	VA1R	BK2R	Gastrin R
H69 (SCLC, Moody et al, 1985)	10.5	0.91±0.15	0.8±0.18	0.65±0.31	0.56±0.49
HT29 (colorectal, Brattain et al, 1981)	18	0.55±0.12	0.02±0.01	0.35±0.04	—
H510 (SCLC, Moody et al, 1985)	29	0.3±0.11	1.10±0.21	0.51±0.17	1.51±40.61
PEO4 (ovarian, Lieber et al, 1975)	31	1.31±0.25	1.10±0.02	0.24±0.10	0.2±0.05
NX002 (NSCLC, Stark et al, 2001)	33.5	1.01±0.21	—	0.65±0.23	0.56±0.28
HRT18 (colorectal, Fogh et al, 1977)	37	0.18±0.04	—	0.80±0.21	0.03±0.01
W X330 (SCLC, Hay et al, 1991)	42	0.09±0.01	3.71±0.91	0.22±0.12	0.27±0.18
PANC1 (pancreatic, O'Hara et al, 1986)	58	0.09±0.01	0.10±0.02	0.38±0.11	—
HCT116 (colorectal, Langdon et al, 1988)	129	—	—	0.65±0.25	—

RT–PCR products were analysed by densitometry and the relative expression level of four neuropeptide receptors are summarised. These values have been expressed as a ratio of the level of γ-actin expression for each cDNA batch and PCR run. Numbers represent the mean of four to six experiments. Spearman's rank correlation between IC₅₀ value and receptor expression level was performed. A significant correlation between sensitivity to SP-G and GRPR expression was confirmed (Spearman's R value=−0.75, P=0.026^*).