Intravesical suramin: a novel agent for the treatment of superficial transitional-cell carcinoma of the bladder

Suramin Targets the Conserved Ligand-Binding Pocket of Human Raf1 Kinase Inhibitory Protein

Suramin was initially used to treat African sleeping sickness and has been clinically tested to treat human cancers and HIV infection in the recent years. However, the therapeutic index is low with numerous clinical side-effects, attributed to its diverse interactions with multiple biological macromolecules. Here, we report a novel binding target of suramin, human Raf1 kinase inhibitory protein (hRKIP), which is an important regulatory protein involved in the Ras/Raf1/MEK/ERK (MAPK) signal pathway. Biolayer interference technology showed that suramin had an intermediate affinity for binding hRKIP with a dissociation constant of 23.8 µM. Both nuclear magnetic resonance technology and molecular docking analysis revealed that suramin bound to the conserved ligand-binding pocket of hRKIP, and that residues K113, W173, and Y181 play crucial roles in hRKIP binding suramin. Furthermore, suramin treatment at 160 µM could profoundly increase the ERK phosphorylation level by around 3 times. Our results indicate that suramin binds to hRKIP and prevents hRKIP from binding with hRaf1, thus promoting the MAPK pathway. This work is beneficial to both mechanistically understanding the side-effects of suramin and efficiently improving the clinical applications of suramin.

[Innovative treatments of non muscle invasive bladder cancer]

Bladder cancer represents the second most common neoplasm of the urinary tract and the fourth in general among all the neoplastic pathologies for the male gender; in females, it is the eighth most frequent among all cancers. At the initial diagnosis, 70% of bladder tumors are non-muscle invasive. Treatment of this stage is multimodal, both surgical and pharmacological; the aim is not only to remove the tumor completely but also to prevent tumor recurrence and to inhibit its progression. The treatment for non-muscle invasive bladder cancer is a current topic in the scientific community and it is represented by the endoscopic resection of the tumor, which is generally followed by the adjuvant intravesical treatment with chemotherapy or immunotherapy agents, according to the different risk groups. Benefits and limits of intravesical therapies have been known for long; the aim of this study is to present new drugs or new treatment patterns which could emerge as a valid therapeutic alternative to conventional treatments, given the fact that, regardless of the type of treatment, 2/3 of the patients with a diagnosis of non-muscle invasive bladder cancer have a disease recurrence, and the 10-20% of these show a progression to a muscle-invasive tumor. Furthermore, the failure of intravesical therapy implies another therapeutic option, such as radical cystectomy for non-muscle invasive bladder cancer. According to this fact, new strategies include the activation of host immune system and the optimization of cytotoxic effects of chemotherapeutic drugs. Although most of these studies are still in a pre-clinical phase, the experimental outcomes and the initial results in humans are encouraging.

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.

The FGF family: biology, pathophysiology and therapy

The family of fibroblast growth factors (FGFs) regulates a plethora of developmental processes, including brain patterning, branching morphogenesis and limb development. Several mitogenic, cytoprotective and angiogenic therapeutic applications of FGFs are already being explored, and the recent discovery of the crucial roles of the endocrine-acting FGF19 subfamily in bile acid, glucose and phosphate homeostasis has sparked renewed interest in the pharmacological potential of this family. This Review discusses traditional applications of recombinant FGFs and small-molecule FGF receptor kinase inhibitors in the treatment of cancer and cardiovascular disease and their emerging potential in the treatment of metabolic syndrome and hypophosphataemic diseases.

Endocavitary Prophylaxis of Superficial Urothelial Bladder Tumours: New Compounds

Bladder urothelial carcinoma is the fourth most frequent cancer among European men, accounting for about 7% of the total cancers. Transurethral resection (TUR) is usually indicated as the standard treatment for non-muscle invasive bladder cancer (NMIBC). However, TUR is unable to guarantee a complete eradication of Ta, T1 tumors with a recurrence rate ranging from 50 to 70%, and a progression rate to muscle invasive disease ranging from 10 to 15%.

Methods

The European Association of Urology guidelines recommend adjuvant intravesical chemotherapy after definitive diagnosis of intermediate/high risk NMIBC to reduce both recurrence and progression of the disease. To provide a comprehensive review of intravesical treatment options for NMIBC, we performed a search of the PubMed database for articles between 1980 and 2009 that reported on intravesical agents for treating this disease.

Results

A critical analysis of the findings resulting from large multicenter trials, phase I, II, III studies for pertinent novel agents and from review articles was carried out. We focused on the following issues: 1) the role of the treatment with Bacillus Calmette-Guérin (BCG) and the need of maintaining the drug schedule (with or without interferon-alpha); 2) the correct timing of adjuvant immuno- and chemotherapy; 3) the use of the novel chemotherapeutic agents; 4) the use of the novel technique of chemotherapeutic agents administration, with a particular interest on electromotive administration of mitomycin.

Intravesical therapy of superficial bladder cancer

The aim of treatment of superficial bladder cancer with intravesical therapy is threefold: (1) Eradicate existing disease. (2) Prevention of recurrence. (3) Prevention of tumor progression. The prognostic factors allow differentiation in different risk groups and this is useful in planning treatment. Studies on pharmacokinetics have proved the efficacy of optimized drug delivery. Comparing resection with and without intravesical chemotherapy a short term approximately 15% decrease in tumor recurrence with chemotherapy can be obtained but no effect on progression was proven. No agent has proved more effective than the other. Single, early instillation of chemotherapy has proven effective but the role of maintenance therapy has been controversial. Immunotherapy in the form of Bacillus Calmette-Guerin generally have proven more efficacious than chemotherapy. The results in comparison to mitomycin C have not been as conclusive. Several new approaches are explored to improve the efficacy of this therapy.

Suramin's development: what did we learn?

Suramin, a polysulphonated napthylurea, has been extensively evaluated over the past 10 years as an anticancer agent, with the most interest in the treatment of prostate cancer. Early clinical results were promising with response rates of up to 70% being reported. However, a recent double-blind study showed only modest palliative effect in patients with androgen independent prostate cancer. In retrospect, it appears those initial reports failed to control for confounding variables such as antiandrogen withdrawal and hydrocortisone. Suramin causes numerous reversible toxicities (lethargy, rash, fatigue, anemia, hyperglycemia, hypocalcemia, coagulopathies, neutropenia, renal and hepatic complications). Neurotoxicity has been the most significant complication and appears to be related to the intensity of the dosing regimen. An optimal therapeutic dose has not been determined, but it is clear that adaptive controls add little benefit. Aside from moderate toxicities and the low therapeutic index in patients with prostate cancer, suramin's development has taught us some valuable lessons (i.e., anti-androgen withdrawal was noted during suramin's development, the use of PSA as an indicator of tumor burden was initiated during the evaluation of suramin). These lessons can be applied to all clinical trials in hormone refractory prostate cancer. Suramin has significantly enhanced the evolution of our knowledge in several areas of prostate cancer biology and treatment.

Human bladder cancer invasion model using rat bladder in vitro and its use to test mechanisms and therapeutic inhibitors of invasion

As well as being a passive support, the extracellular matrix also regulates key biological processes such as invasion, differentiation and angiogenesis. We have therefore developed an in vitro model of bladder cancer invasion using de-epithelialized rat bladder to allow for tumour cell-extracellular matrix interactions. Onto this we have seeded a panel of human bladder cancer cell lines (RT4, RT112, 253J and EJ28 (T24)) representing progression from well to poorly differentiated phenotypes and used as models of superficial to invasive bladder cancer. The better differentiated cell lines RT4 and RT112 reproducibly grew as stratified epithelium, whereas poorly differentiated EJ28 cells invaded across a broad front. Invasion was not simply related to proliferation rate, measured either as doubling time on plastic (non-invasive 253J and invasive EJ28 having the same doubling time) or by Ki-67 proliferation index within the model. We used the model to test the ability of 4 compounds that interfere with tumour cell-extracellular matrix interactions (suramin, N-acetylcysteine and the urokinase plasminogen activator pathway antagonists A5 compound and monoclonal antibody Mab 3936) to inhibit invasion. At non-toxic concentrations, all significantly inhibited invasion (P< 0.05), although to varying degrees, suramin and A5 almost completely and N-acetylcysteine the least. In conclusion, this model shows the urokinase system is important for bladder invasion and can be used to investigate other mechanisms of bladder cancer invasion and also for the testing of intravesical drugs.

Vascular endothelial growth factor and its correlation with superficial bladder cancer recurrence rates and stage progression

Because of the heterogeneous behavior of superficial bladder cancer, the development of additional simple diagnostic and prognostic tests will be invaluable. The authors have demonstrated significantly elevated levels of urinary VEGF in patients with active bladder cancer. The sensitivity and specificity of urinary VEGF for diagnosing primary or recurrent bladder cancer were superior when compared with the results of cytology, which remains the most widely used noninvasive diagnostic investigation. These results and the authors' previous findings at the mRNA and protein level strongly implicate VEGF in the pathogenesis of bladder cancer recurrence and progression. The potential exists for anti-VEGF strategies in the treatment of, or prophylaxis against, recurrent superficial bladder cancer.

Activity of standard and investigational cytotoxic drugs in primary cultures of tumor cells from patients with kidney and urinary bladder carcinomas

PURPOSE

In vitro tumor models could support the process of development of new cytotoxic drugs and selection of suitable drugs for the individual patient. We investigated whether the testing of tumor cells from patients with kidney or urinary bladder carcinoma by fluorometric microculture cytotoxicity assay (FMCA) could provide clinically relevant data for these tumor types.

MATERIALS AND METHODS

A total of 45 tumor samples from patients with kidney or urinary bladder carcinoma were compared with 247 samples of other tumor types with respect to sensitivity to 8 standard and 6 investigational cytotoxic drugs in the FMCA, a 72 hour assay based on the concept of total cell kill. In bladder carcinomas, sensitivity to standard drugs was correlated to various tumor characteristics.

RESULTS

The technical success rate for kidney and bladder carcinomas was high; approximately 90% of the samples could be analyzed successfully. Kidney carcinomas were highly resistant to standard drugs and bladder carcinomas essentially as sensitive as carcinomas of the breast and ovary but with a steeper dose-response relationship. In bladder carcinoma there was no clear relationship between tumor stage, grade, ploidy, mitoses or p53 expression and drug sensitivity. Except for suramin, kidney carcinomas were poorly sensitive to the investigational drugs CdA, gemcitabine, paclitaxel, vinorelbine and topotecan. In bladder carcinomas paclitaxel, gemcitabine and suramin showed promising activity.

CONCLUSIONS

The FMCA seems suitable for cytotoxic drug sensitivity testing of urinary tract carcinomas. This technique may have a role in new drug development in these tumor types.