Association of IL-17 polymorphisms with gastric cancer risk in Asian populations

Table 1 Characteristics of the included studies focusing on IL-17 genetic polymorphisms

Ref.	Year	Country	Sample size		Gender (M/F)		Age (yr)		Genotyping methods	Gene	SNP	STROBE
			Case	Control	Case	Control	Case	Control
Wu et al[30]	2014	China	945	768	-	-	-	-	PCR-RFLP	IL-17A	rs2275913 G>A	29
Zhang et al[23]	2014	China	260	512	162/98	280/232	60.6 ± 10.7	51.3 ± 11.2	Sequenom MassArray	IL-17A	rs2275913 G>A	30
											rs763780 T>C
Zhu et al[2]	2014	China	293	550	189/104	312/238	57.5 ± 11.3	56.7 ± 12.7	Sequenom MassArray	IL-17A	rs2275913 G>A	31
										IL-17F	rs763780 T>C
Rafiei et al[7]	2013	Iran	161	171	89/72	84/87	62.6 ± 12.4	60.8 ± 12.8	PCR-RFLP	IL-17A	rs2275913 G>A	27
Arisawa et al[29]	2012	China	337	587	234/103	314/273	65.3 ± 11.4	61.4 ± 13.7	PCR-SSCP	IL-17A	rs2275913 G>A	33
Zeng et al[31]	2010	China	927	777	-	-	-	-	PCR-RFLP	IL-17F	rs763780 T>C	29
Shibata et al[20]	2009	Japan	287	524	203/84	307/217	65.0 ± 11.8	55.7 ± 18.3	PCR-SSCP	IL-17A	rs2275913 G>A	32
										IL-17F	rs763780 T>C

M: Male; F: Female; PCR-RFLP: Polymerase chain reaction-restriction fragment length polymorphism; PCR-SSCP: Polymerase chain reaction-single-strand conformation polymorphism; STROBE: Strengthening the Reporting of Observational Studies in Epidemiology.

Table 2 Meta-analysis of the association between IL-17 genetic polymorphisms and gastric cancer

Subgroup analysis	W allele vs M(Allele model)			WW + WM vs MM(Dominant model)			WW vs WM + MM(Recessive model)			WW vs MM(Homozygous model)			WW vs WM(Heterozygous model)
	OR	95%CI	P value	OR	95%CI	P value	OR	95%CI	P value	OR	95%CI	P value	OR	95%CI	P value
rs2275913 G>A	1.33	1.12-1.57	0.001	1.34	1.11-1.62	0.003	1.50	1.15-1.94	0.002	1.65	1.23-2.20	0.001	1.42	1.10-1.84	0.008
Country
China	1.47	1.05-2.05	0.024	1.59	1.19-2.11	0.001	1.60	0.95-2.70	0.078	1.98	1.12-3.50	0.019	1.43	0.86-2.38	0.167
Iran	1.22	0.90-1.65	0.207	1.07	0.66-1.73	0.788	1.49	0.93-2.39	0.095	1.39	0.79-2.44	0.258	1.57	0.94-2.63	0.087
Japan	1.19	1.04-1.37	0.013	1.12	0.89-1.40	0.322	1.37	1.11-1.70	0.004	1.36	1.04-1.77	0.022	1.38	1.10-1.74	0.006
Genotyping method
PCR-RFLP	1.11	0.98-1.26	0.088	1.24	1.02-1.52	0.034	1.15	0.79-1.69	0.468	1.23	0.97-1.57	0.088	1.13	0.67-1.93	0.644
MassArray	1.72	1.48-2.00	< 0.001	1.85	1.43-2.41	< 0.001	2.06	1.66-2.56	< 0.001	2.61	1.95-3.49	< 0.001	1.83	1.45-2.32	< 0.001
PCR-SSCP	1.19	1.04-1.37	0.013	1.12	0.89-1.40	0.322	1.37	1.11-1.70	0.004	1.36	1.04-1.77	0.022	1.38	1.10-1.74	0.006
rs763780 T>C	1.95	1.47-2.59	< 0.001	1.21	0.85-1.72	0.299	2.47	1.63-3.74	< 0.001	1.54	1.15-2.05	0.004	2.83	1.63-4.91	< 0.001
Country
China	1.85	1.32-2.59	< 0.001	1.13	0.84-1.54	0.421	2.42	1.40-4.18	0.002	1.45	1.07-1.95	0.016	2.93	1.34-6.39	0.007
Japan	2.31	1.71-3.12	< 0.001	2.60	0.88-7.72	0.085	2.68	1.91-3.75	< 0.001	3.44	1.15-10.26	0.027	2.62	1.86-3.70	< 0.001
Genotyping method
PCR-RFLP	1.40	1.19-1.66	< 0.001	1.40	0.91-2.14	0.122	1.51	1.24-1.84	< 0.001	1.60	1.04-2.46	0.033	1.50	1.21-1.85	< 0.001
MassArray	2.17	1.78-2.66	< 0.001	0.94	0.62-1.41	0.759	3.14	2.45-4.01	< 0.001	1.32	0.87-1.99	0.194	4.20	3.14-5.62	< 0.001
PCR-SSCP	2.31	1.71-3.12	< 0.001	2.60	0.88-7.72	0.085	2.68	1.91-3.75	< 0.001	3.44	1.15-10.26	0.027	2.62	1.86-3.70	< 0.001

W: Wild-type allele; M: Mutant allele; WW: Wild-type homozygote; WM: Heterozygote; MM: Mutant homozygote; SNP: Single nucleotide polymorphism.

Table 3 Univariate and multivariate meta-regression analyses of the potential source of heterogeneity

Heterogeneity factors	rs2275913 G>A						rs763780 T>C
	Coefficient	SE	Z	P value	95%CI		Coefficient	SE	Z	P value	95%CI
					LL	UL					LL	UL
Publication year
Univariate	0.042	0.048	0.87	0.386	-0.053	0.137	0.034	0.065	0.52	0.601	-0.093	0.161
Multivariate	0.040	0.030	1.32	0.185	-0.019	0.098	-0.093	0.056	-1.67	0.094	-0.202	0.016
Country
Univariate	-0.119	0.123	-0.97	0.332	-0.360	0.121	0.225	0.335	0.67	0.502	-0.432	0.882
Multivariate	0.035	0.087	0.41	0.684	-0.135	0.206	0.279	0.167	1.67	0.094	-0.048	0.606
Genotyping method
Univariate	-0.209	0.049	-4.27	0.000	-0.305	-0.113	-0.216	0.091	-2.36	0.018	-0.395	-0.037
Multivariate	-0.218	0.051	-4.31	0.000	-0.317	0.119	-0.219	0.067	-3.27	0.001	-0.350	-0.087

UL: Upper limit; LL: Lower limit.