Methylation patterns of Rb1 and Casp-8 promoters and their impact on their expression in bladder cancer

Aberrant methylation of the promoter CpG island of human genes is an alternative gene inactivation mechanisms that contributes to the carcinogenesis of human tumors. We tried to determine the methylation status and its impact on the expression of two tumor related genes Casp-8 and Rb1 in 103 bladder tumor tissues and 48 control paraffin-embedded tissues by using MSP-PCR and SQRT-PCR. Of the patients, 19.4% for Casp-8 and 28.2% for Rb1 showed methylation in bladder cancer. There were significant differences between patients and healthy controls in methylation of Rb1 (p = 0.001) and Casp-8 (p = 0.008) and especially when both genes methylated (p = 0.004). Methylation of Casp-8 has mostly been taken places in patients with age >60 years (p = 0.013) whereas methylation of Rb1 has taken place in age >60 (p = 0.018) as well as in patients age <60 (p = 0.027). Patients with methylated of both genes with stage T2 showed an increasing risk of 4.75 fold (95% CI = 2.87-7.85, p = 0.00) and for stage T3, 23.50 fold (95% CI = 6.05-91.21, p = 0.00) of bladder cancer. Smoking showed a high significant effect on methylation (p = 0.00 in compare to non-smoker patients), especially in those with pack-years more than 44.7 (OR = 3.53, 95% CI = 1.69-7.35, p = 0.001). The risk of bladder cancer was marginally associated in drinker patients (OR = 1.78, 95% CI = 1.42-2.24, p = 0.010) featuring both genes methylated, especially in those patients consumed alcohol units>30 per week (OR = 4.57, 95% CI = 2.38-8.80, p = 0.000). Significant reduction in expression has been detected in patients with methylated Rb1 (p = 0.00) and Casp-8 (p = 0.03). These results suggest that age, smoking and drinking will increase the probability of methylation of these genes and consequently increased risk of developing of bladder cancer to higher stages of disease. Interestingly, it has been deduced that methylation by itself maybe significantly have a role on reducing the expression ofRb1, but it seems that methylation along with risk factors lead to decrease the expression of Casp-8. Methylation of Rb1 can be considered as one of prognosis indicator for progression and development bladder cancer.