BMC Cancer 2007, 7:187 http://www.biomedcentral.com/1471-2407/7/187 significant difference was demonstrated in susceptibility to OSCC in individuals less or more than 45 years old (p = 0.002, OR = 2.26, 95%CI = 1.35–3.79) (Table 4). No association was observed with the 1G allele (1G/1G and 1G/2G; p = 0.294, OR = 1.29, 95%CI = 0.84–2.00, whereas a significantly elevated risk of OSCC was exhib- ited with the 2G allele (2G/2G and 1G/2G; p = 0.016, OR = 2.39, 95%CI = 1.21–4.72. The environmental factors, alcohol intake and smoking status were stratified with MMP-1 genotype distributions in OSCC cases, but no sig- nificant association was demonstrated of either factor with the MMP-1 genotype distribution (Table 3). Multivariate analyses of MMP-1 allele frequencies and clinical parameters Logistic regression analysis of OSCC in relation to age, gender, and presence of the 1G and 2G alleles revealed that subjects of 45 years old and older had a 2.47-fold sig- nificantly increased risk of OSCC (p = 0.0006, 95%CI = 1.47–4.14) and that those carrying the MMP-1 2G allele had a 2.30-fold significantly elevated risk (p = 0.018, 95%CI = 1.15–4.58). Thus it was demonstrated that age and the presence of the 2G allele were independently associated with OSCC onset (Table 5). Discussion In this study, we examined SNPs in the promoter regions of MMP-1 and MMP-3 genes in relation to OSCC risk with case-control analyses. Significant differences, i.e., high fre- quency of 2G/2G genotype and decreased frequency of 1G/1G genotype, were observed in the MMP-1 genotype distribution in OSCC cases (p = 0.034, Table 1). Similarly, in comparisons of allele frequency a significant correla- tion was detected between onset of OSCC and genotypes that carry the MMP-1 promoter 2G allele in homo- or het- ero-form (p = 0.016, OR = 2.39, 95%CI = 1.21–4.72). MMP-1 with the 2G type promoter caused a higher expres- sion level of MMP-1 in tissues [11]. The biological mech- Table 3: Relation of MMP-1 genotypes to clinical parameters and environmental factors among the OSCC cases Total Gender Male Female Age (years ± SD) T category T1-2 T3-4 N category N0 N1-3 Tumor location Tongue Lower gingiva Oral floor Buccal mucosa Upper gingiva Palate Alcohol intake Drinker Non-drinker Smoking status Smoker Non-smoker 2G/2G n (%) 77 (45.3) 46 (45.9) 31 (47.2) 54.8 ± 15.1 55 (45.1) 22 (45.8) 50 (43.9) 27 (48.2) 45 (54.9) 14 (35) 6 (35.3) 3 (21.4) 7 (53.8) 2 (50) 45 (45.9) 32 (44.4) 39 (44.3) 38 (46.3) 1G/2G n (%) 79 (46.5) 53 (47.5) 26 (41.3) 57.5 ± 13.2 58 (47.5) 21 (43.8) 53 (46.5) 26 (46.4) 31 (37.8) 24 (60) 9 (52.9) 9 (64.3) 5 (38.5) 1 (25) 45 (45.9) 34 (47.2) 43 (48.8) 36 (43.9) 1G/1G n (%) 14 (8.2) 8 (7.4) 6 (7.5) 60.1 ± 10.9 9 (7.4) 5 (10.4) 11 (9.6) 3 (5.4) 6 (7.3) 2 (5) 2 (11.8) 2 (14.3) 1 (7.7) 1 (25) 8 (8.2) 6 (8.3) 6 (6.8) 8 (9.8) p 0.57 0.277* 0.78 0.607 0.260# 0.982 0.702 T and N categories were according to the UICC TNM classification of malignant tumors for lip and oral cavity. The data were analyzed by the χ2. * One-way ANOVA test. # Fisher's exact tests. Page 4 of 9 (page number not for citation purposes)