Toward critical evaluation of the role(s) of molecular biomarkers in the management of bladder cancer

Biomarkers for non-muscle invasive bladder cancer: Current tests and future promise

The search continues for optimal markers that can be utilized to improve bladder cancer detection and to predict disease recurrence. Although no single marker has yet replaced the need to perform cystoscopy and urine cytology, many tests have been evaluated and are being developed. In the future, these promising markers may be incorporated into standard practice to address the challenge of screening in addition to long-term surveillance of patients who have or are at risk for developing bladder cancer.

Current state of screening for bladder cancer

Bladder cancer is the fourth most commonly diagnosed cancer in men and the eighth most common cancer in women in the USA. Efforts to reduce mortality from bladder cancer must focus on three areas: prevention, development of effective therapies for muscle-invasive and metastatic disease, and early detection of potentially invasive lesions while they are still superficial and amenable to less morbid, but still effective, treatments. As more effective therapies for metastatic transitional cell carcinoma are not on the immediate horizon and preventive measures (except for smoking cessation) have been disappointing, if we are to reduce this disease's morbidity and mortality rates significantly, early detection strategies need to be improved and implemented. The goal of screening for any type of cancer is to detect the disease in its early stages in order to increase the chances for cure or prolongation of life (before micro or gross metastases occur). Since all patients who die of bladder cancer do so from metastases and since almost all patients with metastases have muscle-invading cancers appearing as the first bladder cancer event, diagnosing cancers destined to become muscle invading before they actually are should reduce bladder cancer mortality. This special report reviews the current state of bladder cancer screening in the USA.

Urine proteomics in kidney and urogenital diseases: Moving towards clinical applications

To date, multiple biomarker discovery studies in urine have been conducted. Nevertheless, the rate of progression of these biomarkers to qualification and even more clinical application is extremely low. The scope of this article is to provide an overview of main clinically relevant proteomic findings from urine focusing on kidney diseases, bladder and prostate cancers. In addition, approaches for promoting the use of urine in clinical proteomics including potential means to facilitate the validation of existing promising findings (biomarker candidates identified from previous studies) and to increase the chances for success for the identification of new biomarkers are discussed.

Urinary proteomics: ready for prime time in urological cancer diagnostics?

The impact of clinical proteomics on the diagnosis and treatment of urological malignancies is modest in comparison with the high expectations of the past. However, most available studies suffer from flawed clinical designs rather than from technical limitations. This article will briefly introduce the main technological approaches taken, their advantages and disadvantages and will highlight the different challenges associated with urinary proteome analysis. Furthermore, several examples of the successful application of urinary clinical proteomics in the field of prostate and bladder cancer will be introduced. These examples suggest careful validation of novel biomarkers, appropriate study designs using blinded cohorts enrolled from appropriate target populations and the standardization of techniques as key elements required for successful urinary proteomics studies. These prerequisites are essential for turning the old promise of a personalized medicine approach into a new reality to optimize patients’ preventive and therapeutic care.

Prediction of muscle-invasive bladder cancer using urinary proteomics

PURPOSE

Minimally invasive methods of predicting the risk of muscle-invasive urothelial bladder carcinoma may expedite appropriate therapy and reduce morbidity and cost.

EXPERIMENTAL DESIGN

Here, capillary electrophoresis coupled mass spectrometry was used to identify urinary polypeptide bladder cancer biomarkers in 127 patients. These markers were used to construct a panel discriminating muscle-invasive from noninvasive disease, which was refined in 297 additional samples from healthy volunteers, patients with malignant and nonmalignant genitourinary conditions. Sequencing of panel polypeptides was then done. Finally, the ability of the panel to predict muscle-invasive disease was evaluated prospectively in 130 bladder carcinoma patients. Four sequenced polypeptides formed a panel predictive of muscle-invasive disease.

RESULTS

Prospective evaluation of this panel revealed a sensitivity of 81% [95% confidence interval (CI), 69-90] and specificity of 57% (95% CI, 45-69) for muscle-invasive disease. Multivariate analysis revealed the panel (P < 0.0001) and tumor grade (P = 0.0001), but not urine cytology, predict muscle invasion. A model including grade and panel polypeptide levels improved sensitivity [92% (95% CI, 82-97)] and specificity [68% (95% CI, 55-79)] for muscle-invasive disease. A model score of >0.88 provided a negative predictive value of 77% and positive predictive value of 90% for muscle invasion.

CONCLUSIONS

Use of urinary peptides seems promising in estimating the probability a patient harbors muscle-invasive urothelial bladder cancer. These peptides may also shed novel insights into the biology of bladder tumor progression not obtainable by other methods. Clinical trials seem warranted to evaluate the effect of this approach on practice.

Rat Urinary Bladder Carcinogenesis by Dual-Acting PPARalpha + gamma Agonists

Despite clinical promise, dual-acting activators of PPARalpha and gamma (here termed PPARalpha+gamma agonists) have experienced high attrition rates in preclinical and early clinical development, due to toxicity. In some cases, discontinuation was due to carcinogenic effect in the rat urothelium, the epithelial layer lining the urinary bladder, ureters, and kidney pelvis. Chronic pharmacological activation of PPARalpha is invariably associated with cancer in rats and mice. Chronic pharmacological activation of PPARgamma can in some cases also cause cancer in rats and mice. Urothelial cells coexpress PPARalpha as well as PPARgamma, making it plausible that the urothelial carcinogenicity of PPARalpha+gamma agonists may be caused by receptor-mediated effects (exaggerated pharmacology). Based on previously published mode of action data for the PPARalpha+gamma agonist ragaglitazar, and the available literature about the role of PPARalpha and gamma in rodent carcinogenesis, we propose a mode of action hypothesis for the carcinogenic effect of PPARalpha+gamma agonists in the rat urothelium, which combines receptor-mediated and off-target cytotoxic effects. The proposed mode of action hypothesis is being explored in our laboratories, towards understanding the human relevance of the rat cancer findings, and developing rapid in vitro or short-term in vivo screening approaches to faciliate development of new dual-acting PPAR agonist compounds.

Challenges of using mass spectrometry as a bladder cancer biomarker discovery platform

INTRODUCTION

Bladder cancer (BCa) is one of the most prevalent malignancies worldwide, mostly due to its high recurrence rates. In consequence, the necessity of repeated screening for reappearance demonstrates the urgent need for novel biomarkers as alternatives to invasive standard procedures.

METHODS

Proteomic technologies have emerged as powerful platforms for unbiased biomarker discovery and revolutionized the classical "target-driven" analysis of single marker candidates. Although proteome profiling is still far from demonstrating its full potential in clinical diagnosis, first studies clearly denote its significant potential.

CONCLUSIONS

This review provides a discussion of the challenges related to clinical proteomics using mass spectrometry, emphasizing bladder cancer biomarker discovery. An outline of the technological prerequisites for reliable proteome profiling, data mining and interpretation, as well as, reflections on future trends in the field are provided.

Bladder cancer biomarkers: current developments and future implementation

PURPOSE OF REVIEW

Bladder cancer biomarker development has advanced significantly over the last decade, but has not yet been able to make a significant impact in the diagnosis and management of the disease. Many available markers are suitable, but do not meet the expectations of physicians and patients. Patients do not want to compromise accuracy in diagnosing bladder cancer for less-invasive tests. The review highlights the latest developments in bladder cancer biomarkers, including markers developed over the last year, and comments on the high standards placed on these markers which have delayed their widespread implementation into the urologic field.

RECENT FINDINGS

New markers described in the last year include soluble Fas, urothelial carcinoma-associated 1 and human chorionic gonadotropin beta type II genes. The latter two markers represent the contribution of genomic technology to this field. Also described are updates to known markers, including long-term follow-up of hematuria screening, recent studies in DNA methylation for bladder cancer diagnosis and patient perspectives on bladder tumor markers.

SUMMARY

Biomarkers for bladder cancer have been intensively scrutinized over the last decade, but despite new findings and good performance characteristics, they are currently not accepted in clinical practice.