Interleukin-18 promoter polymorphism is associated with lung cancer: A case-control study

Figures & data

Table I.  IL-18 promoter genotypes in Iranian lung cancer patients and controls.

	Lung cancer patients
	Total	SC*	SCLC**	Controls	Odds ratio
Genotypes	n = 73 (%)	n = 53 (%)	n = 20 (%)	n = 97 (%)	(95% confidence interval)
Position –656
GG	25 (34.2)	18 (34.0)	7 (35.0)	31 (32.0)	Reference^¶
GT	31 (42.5)	22 (41.5)	9 (45.0)	39 (40.2)	0.98 (0.48-1.99)†, 0.97 (0.44-2.12)‡, 1.02 (0.34-3.05)^§
TT	17 (23.3)	13 (24.5)	4 (20.0)	27 (27.8)	0.78 (0.35-1.74)†, 0.82 (0.34-2.00)‡, 0.65 (0.17-2.48)^§
Position –607
CC	15 (20.5)	10 (18.9)	5 (25.0)	40 (41.2)	Reference^¶
CA	45 (61.7)	35 (66.0)	10 (50.0)	46 (47.5)	2.60 (1.26-5.36) †, 3.04 (1.34-6.91)‡, 1.73 (0.54-5.51)^§
AA	13 (17.8)	8 (15.1)	5 (25.0)	11 (11.3)	3.15 (1.16-8.55) †, 2.90 (0.92-9.13)‡, 3.63 (0.89-14.86)^§
Position –137
GG	33 (45.2)	25 (47.2)	8 (40.0)	53 (54.6)	Reference^¶
GC	33 (45.2)	24 (45.3)	9 (45.0)	35 (36.1)	1.54 (0.79-2.88) †, 1.45 (0.71-2.94)‡, 1.70 (0.60-4.83)^§
CC	7 (9.6)	4 (7.5)	3 (15.0)	9 (9.3)	1.24 (0.42-3.67) †, 0.94 (0.26-3.35)‡, 2.20 (0.49-9.93) ^§

*Squamous carcinoma. **Small cell lung carcinoma.

^¶Homozygotes for the common allele were used as a reference.

†Odds ratio and 95% confidence interval for all lung cancer patients (Total). ‡ Odds ratio and 95% confidence interval for SC. ^§Odds ratio and 95% confidence interval for SCLC.

Table II.  Allele frequencies of the IL-18 promoter gene in lung cancer patients and controls.

	Lung cancer patients
	Total	Squamous carcinoma	Small cell lung carcinoma	Controls
Alleles	2n = 146 (%)	2n = 106 (%)	2n = 40 (%)	2n =194
Position -656
G	81 (55.5)	58 (54.7)	23 (57.5)	101 (52.1)
T	65 (44.5)	48 (45.3)	17 (42.5)	93 (47.9)
OR (95% CI)†	0.87 (0.54-1.34)	0.89 (0.55-1.44)	0.80 (0.40-1.59)
Position -607
C	75 (51.4)	55 (51.9)	20 (50.0)	126 (65.0)
A	71 (48.6)	51 (48.1)	20 (50.0)	68 (35.0)
OR (95% CI)	1.75 (1.13-2.72)	1.71 (1.06-2.78)	1.85 (0.93-3.68)
Position -137
G	99 (67.8)	74 (69.8)	25 (62.5)	141 (72.6)
C	47 (32.2)	32 (30.2)	15 (37.5)	53 (27.4)
OR (95% CI)	1.26 (0.79-2.01)	1.15 (0.68-1.93)	1.59 (0.78-3.25)

†Odds ratios with 95% confidence intervals were calculated with the Mantel-Haenszel method.

Table III.  Haplotype frequencies of the IL-18 promoter in lung cancer patients and controls.

Haplotypes	-656	-607	-137	Patients (2n = 146)	Controls (2n = 194)	p-value	pc*
1	G	C	G	50 (34.2%)	75 (38.7%)	0.40	NS^†
2	T	C	G	22 (15.1%)	44 (22.6%)	0.07	NS^†
3	T	A	G	23 (15.7%)	15 (7.7%)	0.02	NS†
4	T	A	C	20 (13.7%)	30 (15.5%)	0.64	NS†
5	G	A	C	22 (15.1%)	16 (8.2%)	0.04	NS†
6	G	A	G	6 (4.2%)	7 (3.6%)	0.81	NS†
7	G	C	C	3 (2.0%)	3 (1.6%)	0.71	NS†
8	T	C	C	0 (0%)	4 (2.1%)	‡	‡

*Corrected p value. †Nonsignificant. ‡The number of subjects was too small to permit statistical analysis.

p-values represent differences in the frequency of a given haplotype between patient and control groups, calculated with the χ² test.