Involvement of alkylating agents in schistosome-associated bladder cancer: the possible basic mechanisms of induction

The Activity of Class I-IV Alcohol Dehydrogenase Isoenzymes and Aldehyde Dehydrogenase in Bladder Cancer Cells

OBJECTIVES

The aim of this study was to determine the differences in the activity of Alcohol Dehydrogenase (ADH) isoenzymes and Aldehyde Dehydrogenase (ALDH) in normal and cancerous bladder cells.

METHODS

Class III, IV of ADH and total ADH activity were measured by the photometric method and class I, II ADH and ALDH activity by the fluorometric method.

RESULTS

Significantly higher total activity of ADH was found in both, low-grade and high-grade bladder cancer, in comparison to healthy tissues.

CONCLUSION

The increased activity of total ADH in bladder cancer cells may be the cause of metabolic disorders in cancer cells, which may intensify carcinogenesis.

Bacteriuria and urinary schistosomiasis in primary school children in rural communities in Enugu State, Nigeria, 2012

INTRODUCTION

According to a study conducted in1989, Enugu State has an estimated urinary schistosomiasis prevalence of 79%. Recently, studies have implicated bacteriuria co-infection in bladder cancer. These bacteria accelerate the multi-stage process of bladder carcinogenesis. Knowledge about the prevalence of this co-infection is not available in Enugu and the information provided by the 1989 study is too old to be used for current decision making.

METHODS

We carried out a cross-sectional survey of primary school children aged 5-15 years, who were randomly selected through a multi stage sampling method using guidelines recommended by WHO for schistosomiasis surveys. An interviewer administered questionnaire was used to collect data on demography, socioeconomic variables and clinical presentations. Urine samples were collected between 10.00am and 2.00pm. Each sample was divided into two: (A) for prevalence and intensity using syringe filtration technique and (B) for culture. Intensity was categorized as heavy (>50ova/10mls urine) and light (<50ova/10mls urine). Significant bacteriuria was bacteria count ≥ 105 colony forming units/ml of urine.

RESULTS

Of the 842 pupils, 50.6% were females. The prevalence of urinary schistosomiasis was 34.1%. Infection rate was higher(52.8%) among 13-15 years(Prevalence Ratio = 2.45, 95% Confidence Interval 1.63-3.69). Heavy infections wad 62.7% and egg count/10mls urine ranged from 21-1138. Significant bacteriuria among pupils with urinary schistosomiasis was 53.7% compared to 3.6% in the uninfected(PR = 30.8,95% CI 18.91- 52.09). The commonest implicated organism was Escherchia coli.

CONCLUSION

We found high prevalence of bacteriuria co-infection among children with urinary schistosomiasis in Enugu State. This underscores the need for concurrent antibiotics administration and follow-up to avert later complications.

Methylguanine DNA methyl transferase activities, glutathione s transferase and nitric oxide in bladder cancer patients

Tumor formation is a multistep process that can be divided in to the stages of tumor initiation, promotion, and progression. DNA repair protein; MGMT is a key suicide enzyme that repairs the mispairing base methylguanine, which is induced in DNA as a minor lesion. The glutathione S transferases (GSTs) are a family of enzymes that are important to protect against alkylating agents. Nitric oxide, contributes to the regulation of tumor angiogenesis. A substantial body of experimental evidence supports the hypothesis that tumor angiogenesis is fundamental for the growth and metastasis of solid tumors. We measured the activities of GST, MGMT, and levels of NO3-/NO2- in the leukocytes from patients with bladder carcinoma and healthy controls and activities of MGMT in the tissue from patients with bladder carcinoma and adjacent normal tissue in bladder. Both GST and tissue MGMT activites were significantly increased in the patient group. There was no significant difference between controls and patients for MGMT activity in peripheral blood leukocytes (PBL). Nitrate/nitrite levels in PBL, there was no significant difference between controls and patients. Nitrate/nitrite levels were increased in G2-G3 tumors. In conclusion, we determined high concentrations of nitrite in leukocytes are suspected alkylation damage by induction nitrosamine. Increased DNA alkylation damage may lead the stimulation of MGMT and GST.

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.

Exon 3 polymorphisms and haplotypes of O6-methylguanine-DNA methyltransferase and risk of bladder cancer in southern China: A case–control analysis

Methylating agents are involved in bladder carcinogenesis. O6-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that removes methyl group from O6-methylguanine and thus plays an important role in the etiology of cancer. We hypothesized that two MGMT polymorphisms in exon 3, C16195T (or MGMT L53L) and C16286T (or MGMT L84F) are associated with risk of bladder cancer. In a hospital-based case-control study of 167 patients with bladder cancer and 204 cancer-free controls frequency-matched by age, sex, smoking status, and alcohol use, we genotyped these two MGMT polymorphisms. We found that these two polymorphisms alone had a non-significant main effect on risk of bladder cancer. However, when these two polymorphisms were evaluated together, individuals with the combined genotypes or haplotypes with one or more variant alleles (i.e. the 16195T and 16286T alleles) had statistically significantly increased risk of bladder cancer (adjusted odd ratio [OR]=1.67, 95% confidence interval [CI], 1.01-2.77) compared with those with no variant allele. In the stratification analysis, the risk of bladder cancer was increased in a dose-response manner as the age increased (P(trend)=0.010), and the increased risk was more pronounced among old subjects (>65 years) (adjusted OR=2.51, 95% CI, 1.05-6.04), men (1.76, 1.00-3.10), and non-drinkers (1.91, 1.08-3.36). In conclusion, these two MGMT polymorphisms may jointly play a role, in the etiology of bladder cancer in southern Chinese population. Larger studies are warranted to validate our findings.

Relationship between schistosomiasis and bladder cancer

Carcinoma of the urinary bladder is the most common malignancy in the Middle East and parts of Africa where schistosomiasis is a widespread problem. Much evidence supports the association between schistosomiasis and bladder cancer: this includes the geographical correlation between the two conditions, the distinctive patterns of gender and age at diagnosis, the clinicopathological identity of schistosome-associated bladder cancer, and extensive evidence in experimentally infected animals. Multiple factors have been suggested as causative agents in schistosome-associated bladder carcinogenesis. Of these, N-nitroso compounds appear to be of particular importance since they were found at high levels in the urine of patients with schistosomiasis-associated bladder cancer. Various strains of bacteria that can mediate nitrosation reactions leading to the formation of N-nitrosamines have been identified in the urine of subjects with schistosomiasis at higher intensities of infection than in normal subjects. In experimental schistosomiasis, the activities of carcinogen-metabolizing enzymes are increased soon after infection but are reduced again during the later chronic stages of the disease. Not only could this prolong the period of exposure to activated N-nitrosamines, but also inflammatory cells, stimulated as a result of the infection, may induce the endogenous synthesis of N-nitrosamines as well as generating oxygen radicals. Higher than normal levels of host cell DNA damage are therefore anticipated, and they have indeed been observed in the case of alkylation damage, together with an inefficiency in the capacity of relevant enzymes to repair this damaged DNA. In experimental schistosomiasis, it was also found that endogenous levels of host cell DNA damage were related to the intensity of infection. All of these factors could contribute to an increased risk of bladder cancer in patients with schistosomiasis, and in particular, the gene changes observed may have potential for use as biomarkers in the early detection of bladder cancer that may assist in alleviating the problem.

O6-methylguanine and O6-methylguanine-DNA [corrected] methyltransferase activity in tissues of BDF-1 mice treated with antiparasitic drugs

Levels of the DNA promutagenic methylation damage, O6-methylguanine (O6-MeG) and the activity of the O6-methylguanine-DNA methyltransferase (MGMT), the enzyme responsible for repairing O6-MeG, were measured at various time intervals in tissues of BDF-I mice administered a single therapeutic dose of the antischistosomal agents hycanthone, oxaminiquine and metrifonate. Hycanthone increased O6-MeG in the liver-DNA after 6 h, then decreased by 3-fold after 48 h. Lower levels of the adduct and a slower rate of formation were found in the intestine and bladder. MGMT activities were significantly lower in the liver (74%) and bladder (25%) compared to control animals after 6 h, then restored by 48 h. Oxaminiquine increased O6-MeG in all tissues, but spleen, after 6 h and persisted only in the bladder after 48 h. Liver and bladder tissues of these animals exhibited a pattern of alteration in the MGMT activity similar to that observed for hycanthone. Metrifonate induced a profile of O6-MeG comparable to that of oxaminiquine but the levels of the adduct were about 2-fold lower. Hepatic MGMT in these animals was significantly lower (approximately 38%) than the control values after 6 h, then restored by 48 h. A significant negative correlation was obtained between O6-MeG and MGMT activity in the liver (r=- 0.85), intestine (r=- 0.62) and bladder (r=- 0.59). These results demonstrate that treatment with antischistosomal agents may lead to the formation of promutagenic alkylation damage in the tissue DNA and alterations in the DNA repair capacity.

Influence of smoking in the glutathione-S-transferase M1 deficiency--associated risk for squamous cell carcinoma of the bladder in schistosomiasis patients in Egypt

In this study we show an effect of the glutathione-S-transferase M1 (GSTM1) null phenotype on the risk for squamous cell carcinoma (SCC) of the bladder among male smokers in Egypt, with an adjusted odds ratio of 4.8 (95% confidence interval: 1.06-21.77). However, no overall effect of the GSTM1 null phenotype on the risk for bladder SCC was observed.

Molecular and genetic events in schistosomiasis-associated human bladder cancer: role of oncogenes and tumor suppressor genes

Carcinoma of the urinary bladder is the most common malignancy in many tropical and subtropical countries and is mainly due to endemic schistosomal infection. Schistosomiasis-associated bladder cancer defines a characteristic pathology and cellular and molecular biology that differs from urothelial carcinoma of non-schistosomal origin. N-Nitroso compounds are suspected etiologic agents in the process of bladder cancer induction during schistosomiasis. Elevated levels of DNA alkylation damage have been detected in schistosome-infected bladders and are accompanied by an inefficient capacity of DNA repair mechanisms. Consequently, high frequency of G --> A transition mutations were observed in the H-ras gene and at the CpG sequences of the p53 tumor suppressor gene. Genetic changes have also been detected in the c-erbB-1 and c-erbB-2 oncogenes and in the cdkn2 and Rb tumor suppressor genes. The potential application of these mutational patterns in providing a biological marker suitable for the biomonitoring and early detection of this neoplasm could indicate new avenues of approach that might alleviate the problem in the future. It can also assist in elucidating the mechanisms by which schistosomiasis augments human bladder cancers.

Complications of urinary tract infections associated with devices used for long-term bladder management

The long-term indwelling urethral catheter continues to be a major cause of morbidity in patients in hospitals, nursing homes and home care. Many authorities have recommended that wherever possible, alternative techniques should be considered for the management of patients with urinary retention or incontinence. This article considers the complications that develop from the urinary tract infections associated with long-term indwelling catheterization and reviews the evidence that the other options for bladder management pose less serious threats to health.

Involvement of inflammatory reactions and elevated cell proliferation in the development of bladder cancer in schistosomiasis patients

Schistosoma haematobium infection is strongly associated with urinary bladder cancer. Although numerous explanations have been proposed for this association, the nature of this relationship remains unresolved. This paper explores the hypothesis that inflammation and elevated cell proliferation play a major role in the development of bladder cancer in infected patients, possibly by increasing the level of genetic instability in the urothelium. The paper details in vivo and in vitro studies being done in our laboratories to test this hypothesis. These studies include population studies in which chromosomal breakage in the bladder of infected individuals is assayed using the micronucleus (MN) test on exfoliated urothelial cells. The approach also includes parallel studies in Vancouver with patients with long-term catheter drainage, a population with many similarities to schistosomiasis patients. In the in vitro studies we are co-incubating bladder cells with activated neutrophils or experimental conditions simulating inflammation. These studies show that inflammatory cells when activated can induce micronuclei in bladder cells and that this response is associated with loci on chromosome 11, a chromosome commonly altered during bladder carcinogenesis. A final approach being used is to assay chromosomal change (MN frequencies and numerical chromosome alterations) and level of proliferation (expression of proliferating cell nuclear antigen) in archival biopsies from schistosomiasis patients. Preliminary results show that a dysregulation of cell proliferation is occurring during cystitis in these patients. The extent to which this alteration affects the level of chromosomal breakage is yet to be determined.

O6-alkylguanine-DNA alkyltransferase activity in schistosomiasis-associated human bladder cancer

O6-Alkylguanine-DNA-alkyltransferase (ATase) activity was measured in extracts of 55 bladder tissue samples (46 tumour and nine uninvolved mucosal tissue) from Egyptian patients with schistosome-associated bladder carcinoma. Activity varied from 2.0 to 16.2 fmole ATase/microgram DNA (mean +/- S.D.; 5.6 +/- 4.0) or from 28 to 351 fmole ATase/mg (117 +/- 71). ATase levels in schistosome-associated bladder cancer tissues (5.6 +/- 4.0 fmole ATase/microgram DNA) tended to be lower than those observed in normal human bladder mucosal tissue (8.5 +/- 4.4 fmole ATase/microgram DNA). In a previous study (Badawi et al., Carcinogenesis, 1992, 13, 877-881) DNA-alkylation damage (O6-methyldeoxyguanosine) was found in 44/46 of these schistosome-associated bladder cancer samples at levels ranging from 0.012 to 0.485 mumole O6-MedG/mole deoxyguanosine. We now report an inverse correlation between the levels of methylation damage and ATase activity (r = -0.67; P < 0.001). These observations encourage further investigations of the possible role of environmental alkylating agents in the aetiology of early bladder cancer associated with schistosomiasis.

Formation of promutagenic methylation damage in tissue-DNA of mice treated with antischistosomal agents

The existence of the promutagenic methylation damage O6-MedG has been measured at various time intervals in different tissue DNAs of mice received a single therapeutic dose of various antischistosomal agents (hycanthone, oxaminiquine and metrifonate). Liver-DNA exhibited the highest levels of O6-MedG in all treated animals while, spleen DNA contained the lowest. The three antischistosomal agents tested seemed to exert the peak concentrations of their alkylating metabolites over a period of several hours following the administration. In mice which had received hycanthone, liver-DNA contained readily detectable amounts of O6-MedG by 6 h post-treatment (0.089 mol O6-MedG/mol dG) and by the end of 48 h, this was decreased by about 3-fold to reach a level of 0.026 mumol/mol dG. In intestinal-DNA, however, O6-MedG was formed more slowly and contained about half the level of that found in the liver-DNA. In the tissue-DNA of animals which had received oxaminiquine, the highest level of O6-MedG was observed at 6 h after administration and at a 24-h time point, the adduct dramatically decreased in the liver and intestine-DNA to undetectable values. In neither tissues was there any evidence for O6-MedG accumulation in the DNA at the end of a 48-h post-treatment. A pattern of O6-MedG, almost similar to that of oxaminiquine, was also observed in tissue-DNA of mice pretreated with metrifonate. These results demonstrate that treatment with antischistosomal agents leads to the formation of highly promutagenic alkylated lesions in the tissue-DNA. The implication of such existence for antischistosomal-induced toxicity and carcinogenicity are discussed.

Possible mechanisms of alteration in the capacities of carcinogen metabolizing enzymes during schistosomiasis and their role in bladder cancer induction

Carcinoma of the urinary bladder is the most common malignancy in many tropical and subtropical countries. There is a well documented association with chronic urinary schistosomal infection, and bladder cancer associated with schistosomiasis is a major cause of morbidity and mortality in the endemic areas. Many factors have been suggested as possible causative agents in schistosome-associated bladder carcinogenesis but theories concerning the possible role of schistosomal infection in altering host metabolism of chemical carcinogens have received most attention. In experimental schistosomiasis there is a common pattern of changes in the activities of several hepatic Phase I and Phase II enzymes. Phase I enzymes show increased activities in the early stages of infection but these activities are reduced to below their preinfection levels in the intermediate and late chronic stages of the disease. The activities of Phase II enzymes are altered in favour of the deconjugation pathways in the later stages of the disease. The possible basic mechanisms that might be involved in such changes during parasitism and their potential role in the induction of bladder neoplasia are discussed.