The prevalence of the GSTM1 null genotypes was 29/87 (33.3%) and 21/40 (52.5%) in controls and oral cancer cases, respectively but the differences were not significant (OR=2.2; 95%CI=0.96-5.1; p=0.06).
A significant risk increase for oral cancer was observed among subjects with the homozygous CYP1A1 (m2/m2) genotype (OR=3.8, 95% CI=1.9-7.7), but not the GSTM1 null genotype (OR=0.7, 95% CI=0.4-1.3).
The null variant of GSTM1 was associated with a marginally significant decrease in oral cancer risk [odds ratio (OR) = 0.6, 95% confidence interval (CI) = 0.3-1.0, and P for trend = 0.09].
GSTT1 null and rs1695 were inversely associated with oral leukoplakia while GSTM1 null, GSTT1 null, rs2031920, rs3813867 (CYP2E1), and rs13181 were associated with OC.
The aim of this study was to estimate the relationship of glutathione S-transferases (GST)P1, GSTA1, GSTM1, and GSTT1 gene polymorphisms to oral cancer risk.
Among the null GSTM1 individuals, those who smoke, consume alcohol, and/or chew betel quid have a significantly increased risk for oral cancer with an odd ratio (OR) = 4.0 (95% CI = 1.2-13.7), OR = 7.2 (95% CI = 1.5-33.8), and OR = 4.4 (95% CI = 1.1-17.8), respectively.
In conclusion, the GSTM1 null genotype may be associated with a higher risk of oral cancer in Asians but not in Caucasians, and this effect may be modified by smoking status.
Among these 14 variants, 9 variants were reported to be significantly associated with the risk of oral cancer (CYP1A1-MspI, CYP2E1-RsaI/PstI, MTHFR-C677T, p73-G4C14-to-A4T14, XRCC1-Arg194Trp, CYP1A1-Ile462Val, GSTM1-±, and NAT2 slow vs rapid).
For GSTM1 gene, null genotype appeared to be a risk factor for oral cancer (null vs present: OR 1.23, 95% CI 1.12-1.34), which was also proved in the subgroup analysis.The results demonstrated that CYP1A1 rs4646903 and null genotype of GSTM1 polymorphisms might serve as risk factors for oral cancer.
GSTM1 null alone or associated with CYP1A1 increased the risk of head and neck cancer; the CYP2E1PstI mutated allele increased the risk for only oral cancer.
Differences in the GSTM1 and GSTT1 null genotype frequencies were observed between individuals of European origin and African origin, but these genotypes do not seem to influence the risk of oral cancer.
Here we determined the hot spot mutations in the D-loop region and revealing correlation if any, with clinical parameters, along with analysing the genetic polymorphism of GSTT1 and GSTM1 and its susceptibility towards oral cancer.
The results also suggested significant association between tobacco habits, especially chewing, variant genotypes of CYP1A1, GSTM1 and GSTT1 and oral cancer risk.
An association of oral squamous cell carcinoma (SCC) susceptibility with an MspI restriction site polymorphism of the CYP1A1 gene and GSTM1 polymorphism were reported in our previous study (Sato M, Sato T, Izumo T, Amagasa T. Genetic polymorphism of drug-metabolizing enzymes and susceptiblility to oral cancer.Carcinogenesis 1999;20:1927-31).