The demographic characteristics variables between cases and healthy controls are summarized in Table 1. Only few patients (16.43%) were presented with family history of lung cancer or other cancer. Histopathological studies revealed 80 NSCLC cases with Squamous cell carcinoma and 60 NSCLC cases with adenocarcinoma, more than 60% of patients were diagnosed in advanced stages with 27% cases positive for distant metastasis as shown in Table 2
Genotype and allele distribution with risk of lung cancer in individual SNPs
The distribution and association results of P21 (rs:1801270) and MDM2 (rs:2279744) genotypic frequencies were evaluated by Hardy-Weinberg equilibrium (HWE) in NSCLC patients and control subjects, observations of genotype frequencies for two SNPs did not deviated significantly from those expected by HWE in both patients and controls (P>0.05).
An association between the genotypes and risk of lung cancer was estimated by using unconditional logistic regression analysis, the allele distribution frequencies of P21 C98A and MDM2 T309G genotypes were compared between patients and control groups. The genotype frequencies of P21 were 42 in wild, 60 in heterozygous, and 38 in homozygous genotypes for patients compared with 90 in wild, 48 in heterozygous , and 12 in homozygous genotypes for control group respectively as shown in figure (1). furthermore, the heterozygous genotype increased the risk of lung cancer by approximately three times (OR= 2.7, 95%C.I= 1.5-4.5, P=0.0003) and homozygous genotype by five times (OR= 5.0, 95%C.I= 3.2-14.4, P=0.0001) when compared with wild genotype. While the genotype frequencies of MDM2 was 33 in wild, 61 in heterozygous, and 46 in homozygous for patients compared with 88 in wild, 52 in heterozygous , and 10 in homozygous for control group respectively as shown in figure (2). furthermore, the heterozygous genotype increased the risk of lung cancer by approximately four times (OR=3.5, 95%C.I=1.8-5.4, P=0.0001) and homozygous genotype by seven times (OR=6.7, 95%C.I= 4-12.4, P=0.0001) as shown in Table 3.
The association and stratification of P21 (rs:1801270) gene polymorphism with risk of lung cancer in NSCLC patients.
The frequencies of P21 C98A in wild, heterozygous and homozygous genotypes were statistically significant in respect to Age, smoking status, family history, TNM stage and metastasis status among patients with increased risk of disease in elderly (>45 years) and smoking patients (OR=1.9, 95%C.I= 0.85-3.3, P=0.04 and (OR=3.6, 95%C.I= 1.7-6.5, P=0.03), also in those have positive family history by 4 times more than those with negative family history (OR=4.2, 95%C.I= 2.1-8.6, P=0.03), TNM stage with increased risk in patients of advanced stages by 5 times (OR=5.0, 95%C.I= 2.9-7.0, P=0.02) and increased risk by approximately 4 times in poor differentiated squamous cell carcinoma and 2 times in adenocarcinoma (OR=3.5, 95% 95%C.I= 2.8-5.9, P=0.04 and OR=2.1, 95%C.I= 1.5-3.8, P=0.03 respectively). Whereas there were no significant differences in sex as shown in Table 4.
The association and stratification of MDM2 (rs: 2279744) gene polymorphism with risk of lung cancer in NSCLC patients.
The frequencies of MDM2 T98G in wild, heterozygous and homozygous genotypes were statistically significant in respect to Age, smoking status, family history, TNM stage and metastasis status among patients with increased risk of disease in individuals who were smoking by approximately 2 times more than not smoking patients (OR=1.8, 95%C.I= 1.5-4.8, P=0.048), also increased risk of disease in subjects who have positive family history by 3 times more than whose with negative family history (OR=3.3, 95%C.I= 2.2-6.8, P=0.04), TNM stage with increased risk in patients of advanced stages by about 3 times (OR=2.8, 95%C.I= 1.5-4.8, P=0.01) and increased risk by two times in poor differentiated squamous cell carcinoma and 3 times in adenocarcinoma (OR=2.15, 95%C.I= 1.7-6.8, P=0.019 and OR=3.0, 95%C.I= 1.7-5.8, P=0.04 respectively). While there were no significant differences with respect to age and sex as shown in Table 5.
Gene-Gene interaction between P21 and MDM2 polymorphisms
In the next step we were examined whether there were a statistical interactions between p21 and MDM2 polymorphisms as appeared in Table 6. We were found that the patients who carried GG genotype of MDM2 were more likely carried P21 Arg/ Arg genotype than control individuals (7.2% and 0.7%) respectively.
The presence of TG genotype in MDM2 and Arg/Arg genotype in P21
was associated with an increased the risk of lung cancer compared to the
lack of such genotype ( OR=2.2, 95% C.I= 1.2- 3.8, and OR=1.3, 95% C.I= 1.0–2.9, respectively). Though, the presence of both MDM2 GG and P21 gen Arg/Arg genotypes was associated with an increased the risk of lung cancer by 5 folds ( OR= 5.2, 95% C.I= 3.0-7.6, P< 0.05) for homogeneity genotypes compared to those who lacked from both genotypes. These results obviously indicate a multiplicative interaction between MDM2 GG genotype and P21 Arg/Arg genotype in the risk of developing lung cancer.