Expression of O-Alkylguanine-DNA Alkyltransferase in Normal and Malignant Bladder Tissue of Egyptian Patients.

Bladder tumour tissues and corresponding uninvolved mucosa (normal tissue) of Egyptian bladder cancer patients were assessed for O(6)-alkylguanine-DNA-alkyltransferase (MGMT) activity by functional assay of tissue extracts (36 paired samples), and distribution by immunofluorescence (IF) microscopy of fixed material (24 paired samples). MGMT varied widely from 42-253 fmoles/mg protein and from 3.2-40 fmoles/µg DNA in normal and 58-468 fmoles/mg protein and 2.5-49.5 fmoles/mg protein, in the tumour tissues; only one tumour had undetectable activity. Pairwise comparison of MGMT activity in tumour and adjacent normal tissue showed no significant difference based on DNA content but was 1.75-fold higher in tumour (P < .01) based on protein. There was no effect of gender or bilharzia infection status. IF showed that in tumours, both the mean percentage of positive nuclei (57.3 ± 20.3%) and mean integrated IF (5.47 ± 3.66) were significantly higher than those in uninvolved tissues (42.8 ± 13.5% P = .04) and (1.89 ± 1.42; P < .01), respectively. These observations suggest that, overall, MGMT levels are increased during human bladder carcinogenesis and that MGMT downregulation is not a common feature of bladder cancers. Based on this, bladder cancers would be expected to be relatively resistant to chemotherapy which involved O(6)-guanine alkylating antitumour agents.

Cisplatin induced damage in kidney genomic DNA and nephrotoxicity in male rats: the protective effect of grape seed proanthocyanidin extract.

The clinical use of cisplatin is highly limited, because of its renal toxicity. In this study, the protective effect of grape seed proanthocyanidin extract (GSPE) against cisplatin-induced nephrotoxicity is investigated in rats. Results showed that DNA qualitative analysis indicated an increase in the instability of the DNA purified from the cisplatin exposed kidney cells. Agarose gel electrophoresis revealed DNA damage in the form of smearing as well as ladder like fragmentation of the kidney genomic DNA. Cisplatin produced different RAPD patterns compared to control. Deletion of bands for the amplified DNA extracted from cisplatin treated rats was the most common outcome. Treatment with cisplatin decreased albumin, and increased urea and creatinine. Cisplatin significantly increased the level of kidney free radicals, and decreased the glutathione content and the activities of the antioxidant enzymes. The presence of GSPE with cisplatin significantly alleviated its nephrotoxicity. In conclusion, the present study showed that cisplatin induced damage in the kidney genomic DNA, lipid peroxidation, inhibition of antioxidant enzymes and alterations of biochemical parameters in plasma and kidney of rats. While, GSPE treatment protected against the toxic effects induced by cisplatin. Thus, GSPE may be used to prevent toxicity during chemotherapeutic treatment with cisplatin.

Bladder tumor contains higher N7-methylguanine levels in DNA than adjacent normal bladder epithelium.

Schistosoma haematobium-infected patients are more likely to develop bladder cancer and be more exposed to carcinogenic N-nitroso compounds than uninfected patients. As N7-methylguanine is a marker of exposure to methylating agents of this type, we have measured N7-methyldeoxyguanosine 3'-monophosphate (N7-MedGp) by (32)P postlabeling. DNA was isolated from 42 paired normal and tumor tissue of Egyptians with bladder cancer. N7-MedGp was detected in DNA from 93% of the tumors and 74% of the normal bladder tissue samples. Adduct levels were highly variable and ranged from 0.04 to 6.4 and from 0.02 to 0.72 micromol/mol deoxyguanosine 3'-monophosphate (dGp) in tumor and normal DNA, respectively. N7-MedGp levels in normal and tumor DNA were highly correlated with one another (P = 0.007). The mean difference (95% confidence interval) in adduct levels between tumor and normal DNA was 0.21 (0.13-0.32) micromol/mol dGp and this was statistically significant (P < 0.001). The adduct ratio (tumor DNA/normal DNA) varied between 0.2 and 136 (median, 4.6). N7-MedGp levels were not associated with gender, age, or the presence of schistosomiasis. However, lower N7-MedGp levels were found in normal DNA from individuals lacking the GSTM1 gene (P = 0.03) but not the GSTT1 gene or in subjects with the Ile105Val GSTP1 polymorphism. These results show that exposure to methylating agents is widespread and suggest that such exposure may play a role both in tumor initiation and progression.