The effect of E.coli infection in association with dibutylamine and sodium nitrate in induction of bladder inflammation and /or bladder carcinogenesis were investigated in 150 male albino rats, divided into five groups, as follows: The first group(G1) infected by E. coli , The second group (G2), given nitrosamine precursors in the diet , The third group(G3) infected by E. coli and given nitrosamine precursors in the diet ,The fourth group(G4) infected by E. coli , given nitrosamine precursors in the diet and received standard diet containing 1% Curcumin powder mixed in the diet and the fifth group (G5) , served as control group . Results: The worst histopathological changes are in G3 . A highly significant decrease in the mean cell lysate level of p21was found in different studied groups(G1,G2&G3) especially in(G3) where P values in these groups when compared to control group were (P < 0.0001) . In curcumin treated group(G4), there were downregulation in the mean cell lysate level of p21 gene when compared to control group but higher than other studied groups (G1,G2&G3) . A highly significant increase in the mean serum level of Bcl-2 was found in different studied groups(G1,G2&G3) especially in(G3) where P values in these groups (G1,G2,G3) when compared to control group were (P < 0.0001). (G4) showed higher Bcl-2 serum level when compared to control group, this difference was insignificant but this level is lower than other studied groups (G1,G2&G3) . Conclusion: The results in the present study indicate that both P21 and Bcl-2 can be used as biological markers in the diagnosis of bladder cancer . Curcumin have the ability to overcome the decrease in p21WAF1/CIP1 protein and the increase of Bcl-2 protein and reduce the induction of carcinogenic effect .