DISTRIBUTION OF DT-DIAPHORASE AND REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE: CYTOCHROME P450 OXIDOREDUCTASE IN BLADDER TISSUES AND TUMORS

New therapies for non-muscle-invasive bladder cancer

The treatment of non-muscle-invasive bladder cancer (NMIBC) remains a challenge owing to its increased tendency to recur and the possibility of progression to potentially dangerous muscle-invasive disease. Treatment outcomes by current therapeutic modalities are still not optimal. In recent years, there have been a number of substantive advances in the therapeutic options for the management of NMIBC. New chemotherapeutic drugs have been introduced, along with efforts made to improve the efficacy of existing agents and enhance delivery of agents to the bladder. There is also a growing trend toward combination of agents and multimodal therapy. Also of considerable interest are the investigation of newer approaches such as gene therapy, chemoenhancement and newer forms of immunotherapy. Here, we review the recent pre-clinical and clinical developments in the treatment of NMIBC, described in the broad categories of immunotherapy, chemotherapeutic agents, improved or device-assisted agent delivery and gene therapy.

Intravesical Pharmacotherapy for Non–Muscle-Invasive Bladder Cancer: A Critical Analysis of Currently Available Drugs, Treatment Schedules, and Long-Term Results

OBJECTIVES

Review adjuvant intravesical pharmacotherapy for non-muscle-invasive bladder cancer (NMIBC), emphasising treatment schedules and long-term results.

METHODS

Search of published literature on conventional treatment of NMIBC, emerging drugs, and device-assisted therapies.

RESULTS

In low-risk NMIBC patients an immediate instillation with chemotherapy is sufficient. For patients with intermediate- or high-risk tumours, additional adjuvant instillations are needed. For intermediate-risk patients chemotherapeutic instillations, usually with mitomycin C or epirubicin, are safe and effective in reducing the risk of recurrence in the short term, but efficacy is only marginal in the long term. Newer drugs have promising results, but long term follow-up is limited or lacking. In these patients bacillus Calmette-Guérin (BCG) does not seem to be more effective, only more toxic. In high-risk NMIBC, or patients in whom chemotherapy fails, BCG is the best choice with lower rates of recurrence and progression. For BCG failures cystectomy is therapy of choice, although the combination of BCG and interferon-alpha can be considered, just as device-assisted therapies such as thermochemotherapy and electromotive drug administration.

CONCLUSIONS

Risk-adapted first-line adjuvant therapy for NMIBC after TURBT is well established but has its limitations because recurrences are still numerous. Some new drugs and second-line therapies are promising, but efficacy should be confirmed.

Current strategies for first and second line intravesical therapy for nonmuscle invasive bladder cancer

PURPOSE OF REVIEW

Nonmuscle invasive bladder cancer is a common malignancy, usually treated by transurethral resection and adjuvant intravesical instillations of chemotherapy or immunotherapy. Appropriate adjuvant treatment can be selected based on several prognostic factors that determine risk for recurrence or progression. We discuss options for first-line and second-line adjuvant therapy for nonmuscle invasive bladder cancer.

RECENT FINDINGS

Mitomycin-C and epirubicin are the mostly used adjuvant chemotherapeutic drugs for tumours of low and intermediate risk. Bacillus Calmette-Guérin remains first-choice therapy in high-risk nonmuscle invasive bladder cancer. Gemcitabine and apaziquone are especially promising for treatment of intermediate risk nonmuscle invasive bladder cancer but require further study. Device-assisted therapies, such as thermochemotherapy and electromotive drug administration, have yielded good results in high-risk nonmuscle invasive bladder cancer and could be considered second-line therapy in this setting.

SUMMARY

Primary problems in nonmuscle invasive bladder cancer are its tendency to recur and its elusiveness (especially high-risk nonmuscle invasive bladder cancer) of progression to muscle invasive disease. First-line adjuvant therapies are well established but suboptimal. Some second-line therapies are promising but should be used cautiously, because in some patients the best option is not always the conservative one.

Bioreductive drugs: from concept to clinic

One of the key issues for radiobiologists is the importance of hypoxia to the radiotherapy response. This review addresses the reasons for this and primarily focuses on one aspect, the development of bioreductive drugs that are specifically designed to target hypoxic tumour cells. Four classes of compound have been developed since this concept was first proposed: quinones, nitroaromatics, aliphatic and heteroaromatic N-oxides. All share two characteristics: (1) they require hypoxia for activation and (2) this activation is dependent on the presence of specific reductases. The most effective compounds have shown the ability to enhance the anti-tumour efficacy of agents that kill better-oxygenated cells, i.e. radiation and standard cytotoxic chemotherapy agents such as cisplatin and cyclophosphamide. Tirapazamine (TPZ) is the most widely studied of the lead compounds. After successful pre-clinical in vivo combination studies it entered clinical trial; over 20 trials have now been reported. Although TPZ has enhanced some standard regimens, the results are variable and in some combinations toxicity was enhanced. Banoxantrone (AQ4N) is another agent that is showing promise in early phase I/II clinical trials; the drug is well tolerated, is known to locate in the tumour and can be given in high doses without major toxicities. Mitomycin C (MMC), which shows some bioreductive activation in vitro, has been tested in combination trials. However, it is difficult to assign the enhancement of its effects to targeting of the hypoxic cells because of the significant level of its hypoxia-independent toxicity. More specific analogues of MMC, e.g. porfiromycin and apaziquone (EO9), have had variable success in the clinic. Other new drugs that have good pre-clinical profiles are PR 104 and NLCQ-1; data on their clinical safety/efficacy are not yet available. This paper reviews the pre-clinical data and discusses the clinical studies that have been reported.

NAD(P)H:Quinone Oxidoreductase 1 and NRH:Quinone Oxidoreductase 2 Activity and Expression in Bladder and Ovarian Cancer and Lower NRH:Quinone Oxidoreductase 2 Activity Associated with an NQO2 Exon 3 Single-Nucleotide Polymorphism

PURPOSE

NRH:quinone oxidoreductase 2 (NQO2) is a homologue of NAD(P)H:quinone oxidoreductase 1 (NQO1). Despite 54% homology with human NQO1, NQO2 has little endogenous enzymatic activity. However, NQO2 has potential as a therapeutic target because the addition of the nonbiogenic electron donor dihydronicotinamide riboside (NRH) selectively potentiates the bioactivation of the alkylating agent tretazicar (CB 1954). The NQO activity of ovarian and bladder tumors was determined and the effect of NQO polymorphisms on NQO activity was investigated.

EXPERIMENTAL DESIGN

Intraperitoneal ovarian metastases and bladder tumor clinical samples were analyzed for NQO1 and NQO2 activity, mRNA expression by semiquantitative reverse transcription-PCR, and genotype by RFLP analysis.

RESULTS

NQO1 activity was higher in the bladder cohort than in the ovarian cohort (0-283 and 0-30 nmol/min/mg, respectively; P < 0.0001). In contrast, NQO2 activity was higher in the ovarian tissue than in the bladder samples (0.15-2.27 and 0-1.14 nmol/min/mg, respectively; P = 0.0004). In both cohorts, the NQO1 C609T single-nucleotide polymorphism (SNP) was associated with approximately 7-fold lower NQO1 activity. The NQO2 exon 3 T14055C SNP was associated with lower NQO2 activity relative to wild-type [median values of 0.18 and 0.37 nmol/min/mg in the bladder samples (P = 0.007) and 0.82 and 1.16 nmol/min/mg in the ovarian cohort (P = 0.034)].

CONCLUSION

This is the first observation reporting an apparent association between an NQO2 exon 3 SNP and lower enzymatic activity. The high NQO2 activity of intraperitoneal ovarian metastases relative to other tissues indicates a potential for tretazicar therapy in the treatment of this disease. In contrast, the low level of NQO1 activity and expression relative to other tissues suggests that NQO1-directed therapies would not be appropriate.

Phase II Marker Lesion Study With Intravesical Instillation of Apaziquone for Superficial Bladder Cancer: Toxicity and Marker Response

PURPOSE

We studied the ablative activity of intravesical apaziquone (EOquin) on a papillary marker tumor and determined the incidence of side effects.

MATERIALS AND METHODS

A total of 46 patients with multiple pTa or pT1 bladder tumors underwent visible lesion resection except for 1 marker tumor. Patients were then treated with 6 instillations of apaziquone at weekly intervals. The response was determined 2 to 4 weeks after the last instillation.

RESULTS

One patient withdrew informed consent and refused the last treatment due to side effects. A histologically proven complete response was seen in 30 patients. Progression to invasive stage was not observed. Local side effects in this study were comparable to those due to other chemotherapy instillations, such as mitomycin C and epirubicin, but less severe and less frequent compared to those of bacillus Calmette-Guerin instillations.

CONCLUSIONS

The histological complete response rate after 6 consecutive instillations of apaziquone in patients with superficial bladder cancer was 67% (95% CI 51 to 80). Local side effects were comparable to side effects due to other chemotherapy instillations.

Combinatorial antigenotoxic and anticarcinogenic effects of tomato and garlic through modulation of xenobiotic-metabolizing enzymes during hamster buccal pouch carcinogenesis

OBJECTIVE

Combination chemoprevention by dietary agents is a promising approach toward cancer control. Many dietary agents are known to prevent experimental mutagenesis and carcinogenesis by modulating xenobiotic-metabolizing enzymes. The present study evaluated the combinatorial chemopreventive effects of tomato and garlic on hamster buccal pouch carcinogenesis induced by 7,12-dimethylbenz[a]anthracene (DMBA).

METHODS

Hamsters were assigned to one of four groups. The right buccal pouches of animals in group 1 were painted with 0.5% DMBA three times a week. The right buccal pouches of animals in group 2 were painted with DMBA and received intragastric administration of a combined dose of tomato and garlic on days alternate to DMBA application. Animals in group 3 were given chemopreventive agents alone. Animals in group 4 served as controls. Levels of phase I and II enzymes and the frequency of bone marrow micronuclei were used as biomarkers of chemoprevention.

RESULTS

All the hamsters painted with DMBA alone developed buccal pouch carcinomas that exhibited increased activities of xenobiotic-metabolizing enzymes associated with increased frequencies of bone marrow micronuclei. In the liver, an increase in phase I enzymes was accompanied by compromised phase II detoxification activities. Combined administration of tomato and garlic effectively suppressed the incidence and mean tumor burden of hamster buccal pouch carcinomas. In addition, tomato and garlic combination significantly decreased phase I enzymes and increased phase II enzyme activities in the pouch and liver with a decreased incidence of bone marrow micronuclei.

CONCLUSION

From these results, we suggest that modulation of xenobiotic-metabolizing enzymes exerted by tomato and garlic combination plays a key role in mitigating the mutagenic and carcinogenic effects of DMBA.

Immunohistochemical analysis of NAD(P)H:quinone oxidoreductase and NADPH cytochrome P450 reductase in human superficial bladder tumours: Relationship between tumour enzymology and clinical outcome following intravesical mitomycin C therapy

A central theme within the concept of enzyme-directed bioreductive drug development is the potential to predict tumour response based on the profiling of enzymes involved in the bioreductive activation process. Mitomycin C (MMC) is the prototypical bioreductive drug that is reduced to active intermediates by several reductases including NAD(P)H:quinone oxidoreductase (NQO1) and NADPH cytochrome P450 reductase (P450R). The purpose of our study was to determine whether NQO1 and P450R protein expression in a panel of low-grade, human superficial bladder tumours correlates with clinical response to MMC. A retrospective clinical study was conducted in which the response to MMC of 92 bladder cancer patients was compared to the immunohistochemical expression of NQO1 and P450R protein in archived paraffin-embedded bladder tumour specimens. A broad spectrum of NQO1 protein levels exists in bladder tumours between individual patients, ranging from intense to no immunohistochemical staining. In contrast, levels of P450R were similar with most tumours having moderate to high levels. All patients were chemotherapy naïve prior to receiving MMC and clinical response was defined as the time to first recurrence. A poor correlation exists between clinical response and NQO1, P450R or the expression patterns of various combinations of the 2 proteins. The results of our study demonstrate that the clinical response of superficial bladder cancers to MMC cannot be predicted on the basis of NQO1 and/or P450R protein expression and suggest that other factors (other reductases or post DNA damage events) have a significant bearing on tumour response.

Role of the AP-1 element and redox factor-1 (Ref-1) in mediating transcriptional induction of DT-diaphorase gene expression by oltipraz: a target for chemoprevention

The dithiolethione oltipraz is a potent chemopreventive agent in preclinical models, and induces the expression of protective enzymes in the colon mucosa and peripheral mononuclear cells of treated human subjects. We investigated the effects of oltipraz on DT-diaphorase expression in HT29 colon adenocarcinoma cells. Following a 24-hr exposure to 100 microM oltipraz, elevated steady-state levels of mRNA for Jun and Fos family members were observed. A nuclear run-on assay showed induction of c-fos and c-jun transcripts at the end of the exposure, peaking at 12 hr after resuspension of cells in drug-free medium. Gel mobility shift analysis revealed a similar time-course of induced nuclear factor binding to an AP-1 probe. Supershift analysis verified the participation of Jun and Fos in the complexes. The redox coactivator Ref-1, a function of which is to enhance AP-1 binding, was induced 5-fold by oltipraz. Immunodepletion of Ref-1 partially inhibited factor binding to the AP-1 probe. Deletion analysis of the DT-diaphorase promoter in a CAT reporter construct revealed that loss of the AP-1 site accounted for approximately 65% of the induction by oltipraz. Mutation of the AP-1 element in a full-length promoter construct yielded similar results. These data suggest the importance of transcriptional activation mediated by AP-1 in the chemopreventive activity of oltipraz, and indicate that novel chemoprevention structures may be selected based upon agonist activity at this locus.

NADPH-cytochrome P-450 reductase in the plasma membrane modulates the activation of hypoxia-inducible factor 1

Hypoxia induces a group of physiologically important genes that include erythropoietin (EPO) and vascular endothelial growth factor (VEGF). Hypoxia-inducible factor 1 (HIF-1) was identified as a hypoxia-activated transcription factor; however, the molecular mechanisms that underlie hypoxia signal transduction in mammalian cells remain undefined. In this study, we found that a flavoprotein, NADPH-P450 reductase (NPR), could regulate the induction of EPO mRNA under hypoxic conditions. Hypoxic EPO mRNA induction in Hep3B cells was inhibited by diphenyleneiodonium chloride, which is an inhibitor of NADPH-dependent enzymes. NPR antisense cDNA was transfected into Hep3B cells, and NPR-deficient hepatocyte cells (NPR(-) cells) were established. NPR(-) cells lacked EPO induction under hypoxia, and HIF-1alpha in NPR(-) cells did not respond to either transcriptional activation or translocation to the nucleus based on electrophoretic mobility shift assays and reporter gene assay including hypoxia response element. In contrast, NPR overexpression in Hep3B cells enhanced the DNA binding activity of HIF-1alpha by luciferase reporter gene assay. A study with HeLa S3 cells produced the same results. Furthermore, anti-NPR IgG inhibited EPO induction. EPO induction inhibited by diphenyleneiodonium chloride was recovered by bovine serum albumin-NADPH (a covalent binding complex of bovine serum albumin and NADPH) as well as NADPH. These results suggested that NPR located at the plasma membrane regulates EPO expression in hypoxia, including HIF-1 activation and translocation. We further studied the expression of NPR and VEGF mRNAs in human tumor tissues and found that the NPR mRNA levels were correlated with the VEGF mRNA levels, suggesting that NPR might be an important factor in the hypoxic induction of genes such as VEGF in vivo.