This Month in Investigative Urology

Article Outline

• Gene Polymorphisms in Androgen Pathways as Risk Factors for Prostate Cancer
• Functional Cannabinoid Receptor Expression in Human Bladder Detrusor and Urothelium
• Biochemical Alterations in Partial Bladder Outlet Obstruction in Mice
• Intraperitoneal Chemotherapy for Transitional Cell Carcinomatosis in a Rat Model
• BCL2 −938C/A Polymorphism and Biochemical Recurrence After Radical Prostatectomy
• Copyright

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Gene Polymorphisms in Androgen Pathways as Risk Factors for Prostate Cancer 

Prostate cancer, the most common malignancy in men in industrialized Western countries, has proved to be a heterogeneous disease with multiple risk factors. In recent years the role of genetic factors has become increasingly clear. The involvement of androgens is well-known and, therefore, endogenous androgens have long been considered risk factors for prostate cancer. Mononen and Schleutker (page 1541) from Tampere, Finland reviewed the association of androgen pathway genes and their polymorphic sites, and the risk of prostate cancer in individuals of different ethnic backgrounds. They performed a PubMed® search using the key words “prostate cancer” and 20 select gene names combined with “variant” and “polymorphism.” Relevant articles and references during 1998 to 2008 were reviewed for data on the association between polymorphisms and prostate cancer risk. Even if androgen pathway genes have a role in prostate cancer susceptibility, the effects of polymorphisms seem to vary in different patients, populations and ethnic backgrounds. The most studied genetic variants are those of AR, SRD5A2, CYP17A1 and CYP3A loci, and the most recent intriguing data come from SHBG and SULT2A genes, of which relatively few studies have been performed. The authors conclude that the association between androgen pathway gene polymorphisms and prostate cancer risk is complex and characterized by contradictory results. However, recent developments that reach beyond single gene studies, such as genome scale single nucleotide polymorphism studies and multinational collaborations, are a great prospect for future study and understanding of more complex interactions.

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Functional Cannabinoid Receptor Expression in Human Bladder Detrusor and Urothelium 

Information on the localization and function of cannabinoid (CB) receptors in the bladder is scarce, and definitive expression of these receptors in the human bladder has not been reported. Tyagi et al (page 1932) from Pittsburgh, Pennsylvania investigated the expression of functional CB1 and CB2 receptors in human bladder detrusor and urothelium using real-time quantitative polymerase chain reaction, and protein expression using immunohistochemistry and Western blot. Functional responses were tested by studying the effect of selective CB1 and CB2 receptor agonists on nerve evoked smooth muscle contraction. Expression of CB1 and CB2 receptors was demonstrated in the detrusor and urothelium, with the expression for both receptors approximately 2-fold higher in the urothelium than in the detrusor (p >0.05). mRNA expression of the CB1 receptor was significantly higher than that of the CB2 receptor in both tissue types (p ≤0.05). Expression was confirmed at the protein level by immunoreactivity and Western blot analysis. Activation of CB1 and CB2 receptors attenuated the electrically evoked contraction of detrusor strips. These findings suggest a physiological role for CB1 and CB2 receptors in the human bladder, and that these receptors are functional. The authors speculate that CB1 and CB2 receptors can serve as a target for drugs acting on symptoms of interstitial cystitis/painful bladder syndrome.

In a similar study Gratzke et al (page 1939) from Winston-Salem, North Carolina investigated the distribution of CB1 and CB2 receptors in rat, monkey and human detrusor, and the effects of CB1/CB2 receptor agonists on bladder function. Expression of CB1 and CB2 receptors was studied with Western blot and immunohistochemistry. Co-staining was performed for markers of sensory nerves using calcitonin gene-related peptide and transient receptor potential vanilloid receptor 1, and for markers of cholinergic nerves using VAChT. Actions of anandamide, an endogenous CB1/CB2 receptor agonist, and CP55, 940, a CB1/CB2 receptor agonist, on isolated detrusor and during cystometry in conscious rats were recorded.

Gratzke et al found higher expression in the mucosa than in the detrusor of CB2 receptor, but not of CB1 receptor. In comparison to the detrusor, larger amounts of CB2 receptor containing nerves that also expressed transient receptor potential vanilloid receptor 1 or calcitonin gene-related peptide were observed in the suburothelium. Nerve fibers containing CB2 receptor and VAChT were located in the detrusor. Nerve mediated contractions were enhanced by anandamide and decreased by CP55, 940 (p <0.05). In vivo CP55, 940 increased the micturition interval and threshold pressure (p <0.05). The distribution of CB2 receptor on sensory nerves and in the urothelium, together with effects by CP55, 940 on the micturition interval and threshold pressure suggest a role for CB2 receptor in bladder afferent signals. In addition, the co-expression of VAChT and CB2 receptor, and effects by CP55, 940 on nerve mediated contractions suggest a CB2 receptor mediated modulatory effect on cholinergic nerve activity.

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Biochemical Alterations in Partial Bladder Outlet Obstruction in Mice 

Bladder outlet obstruction leading to bladder hypertrophy is a prevalent clinical problem that may result from multiple etiologies. Many rodent models have been developed for partial bladder outlet obstruction including rat, guinea pig, rabbit and cat. The mouse model offers a distinct advantage in the ability to create transgenic and gene knockout mice, which allows more precise characterization of the molecular events involved in the bladder response to outlet obstruction. Using a mouse model Myers et al (page 1926) from Denver, Colorado evaluated the effect of partial bladder outlet obstruction on bladder weight, protein synthesis, mitotic markers and the mitogen activated protein kinase (MAPK) pathway.

Mice were divided into 3 groups of control, sham and partially obstructed. Bladders were harvested from the mice in the partially obstructed group 12, 24, 48, 72 and 168 hours after surgical partial outlet obstruction. Partially obstructed bladders were compared to bladders in the control and sham treated groups by weight, protein content, and expression of proliferating cellular nuclear antigen, cyclin D3, heat shock protein 70, c-jun and phosphorylated c-jun. Bladders were examined histologically for changes occurring with partial obstruction. No statistical difference was found in body weight among the groups. There was a significant increase in bladder weight and protein content in the partially obstructed mice compared to controls and sham operated mice. There was up-regulation of proliferating cellular nuclear antigen, cyclin D3, heat shock protein 70, c-jun and phosphorylated c-jun with partial obstruction. Fibrosis was prominent at 168 hours compared to that in controls. This seems to be the first demonstration of MAPK up-regulation in an in vivo mouse model of partial bladder outlet obstruction. The MAPK pathway may regulate a diverse number of responses to the insult of partial outlet obstruction, including cellular hyperplasia, bladder hypertrophy and fibroblast differentiation. Studies of this nature may lead to innovative therapy strategies that could prevent or reverse myogenic bladder failure and the development of end stage neurogenic bladder.

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Intraperitoneal Chemotherapy for Transitional Cell Carcinomatosis in a Rat Model 

Approximately 70% to 80% of bladder cancers are superficial at initial presentation and can be treated with transurethral resection as primary therapy. However, intraperitoneal and extraperitoneal bladder perforation during resection is a potential complication. Tumor spillage from bladder perforation during transurethral resection of a bladder tumor or cystectomy risks seeding the peritoneum with transitional cell carcinoma. The effectiveness of local administration of mitomycin C (MMC) in preventing intraperitoneal tumor implantation in a rat model has previously been demonstrated. Using this model Abaza et al (page 1901) from Columbus, Ohio sought the lowest effective MMC dose to prevent tumor implantation and evaluated the potential efficacy of delayed therapy. They also investigated the effect of tumor debulking combined with intraperitoneal MMC.

To find the lowest effective dose MMC was instilled at decreasing concentrations, and to evaluate the effectiveness of delayed therapy MMC was administered on day 3 or 7 after tumor implantation. Surgical debulking of established tumors with or without MMC was also performed. All control animals had disseminated carcinomatosis. The lowest effective intraperitoneal MMC dose to prevent implantation was 0.3125 mg/m². Administration of MMC on day 3 after instillation resulted in tumor-free status in 50% of animals. However, no animals were tumor-free when treated on day 7. Tumor debulking only for established disease cured 40% of animals whereas debulking combined with MCC had a 100% cure rate. The authors concluded that intraperitoneal MMC prevents tumor growth after transitional cell carcinoma implantation. Delayed therapy is not as effective as immediate treatment but cure is still possible, particularly when combined with surgical debulking, in a rat model.

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BCL2 −938C/A Polymorphism and Biochemical Recurrence After Radical Prostatectomy 

After any of the current treatment options for clinically localized prostate cancer approximately 10% to 26% of patients experience biochemical failure. Finding new biomarkers for predicting biochemical recurrence is needed in patients at high risk and new markers may be beneficial for selecting adjuvant therapy. The importance of the cell cycle and apoptosis pathways in prostate cancer has been reported in various studies. However, there is currently no information on the role of apoptosis and cell cycle related gene polymorphisms in prostate cancer. Hirata et al (page 1907) from San Francisco, California investigated several polymorphisms related to the cell cycle and apoptosis as well as their role in biochemical failure after radical prostatectomy.

They genotyped 6 single nucleotide polymorphisms in 6 genes, including p53 (rs1042522), p21 (rs1801270), MDM2 (rs2279744), PTEN (rs701848), GNAS1 (rs7121) and bcl2 (rs2279115), using polymerase chain reaction-restriction fragment length polymorphism and direct DNA sequencing in 140 patients with prostate cancer and 167 age matched controls. The association of polymorphic variants with prostate specific antigen failure in patients with prostate cancer was analyzed by Kaplan-Meier curves. There was a significant increase in the frequency of the C/C genotype of GNAS1 rs7121 in patients vs controls. A significant difference in biochemical recurrence-free time between the bcl2 C/C genotype and C/A+A/A genotypes was also found. On multivariate analysis the Bcl2 C/C genotype was an independent risk factor for biochemical recurrence after radical prostatectomy. There was no statistical difference in the genotype distributions of the other genes between patients and controls. This is the first report documenting that bcl2 promoter region –938 C/C genotype carriers more frequently show biochemical recurrence than –938C/A+A/A carriers.