Evaluation of Uracil, Sodium Ascorbate, and Rosiglitazone as Promoters of Urinary Bladder Transitional Cell Carcinomas in Male Sprague-Dawley Rats

Preclinical models of bladder cancer: BBN and beyond

Preclinical modelling is a crucial component of advancing the understanding of cancer biology and therapeutic development. Several models exist for understanding the pathobiology of bladder cancer and evaluating therapeutics. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN)-induced bladder cancer is a commonly used model that recapitulates many of the features of human disease. Particularly in mice, BBN is a preferred laboratory model owing to a high level of reproducibility, high genetic fidelity to the human condition, and its relative ease of use. However, important aspects of the model are often overlooked in laboratory studies. Moreover, the advent of new models has yielded a variety of methodologies that complement the use of BBN. Toxicokinetics, histopathology, molecular genetics and sex can differ between available models and are important factors to consider in bladder cancer modelling.

Pioglitazone, Bladder Cancer and the Presumption of Innocence

BACKGROUND

Thiazolidinediones are potent exogenous agonists of PPAR-γ, which augment the effects of insulin to its cellular targets and mainly at the level of adipose tissue. Pioglitazone, the main thiazolidinedione in clinical practice, has shown cardiovascular and renal benefits in patients with type 2 diabetes, durable reduction of glycated hemoglobulin levels, important improvements of several components of the metabolic syndrome and beneficial effects of non-alcoholic fatty liver disease.

OBJECTIVE

Despite all of its established advantages, the controversy for an increased risk of developing bladder cancer, combined with the advent of newer drug classes that achieved major cardiorenal effects have significantly limited its use spreading a persistent shadow of doubt for its future role.

METHODS

Pubmed, Google and Scope databases have been thoroughly searched and relevant studies were selected.

RESULTS

This paper explores thoroughly both in vitro and in vivo (animal models and humans) studies that investigated the possible association of pioglitazone with bladder cancer.

CONCLUSION

Currently the association of pioglitazone with bladder cancer cannot be based on solid evidence. This evidence cannot justify its low clinical administration, especially in the present era of individualised treatment strategies. Definite clarification of this issue is imperative and urgently anticipated from future high quality and rigorous pharmacoepidemiologic research, keeping in mind its unique mechanism of action and its significant pleiotropic effects.

A study in a rat initiation-promotion bladder tumour model demonstrated no promoter/progressor potential of dapagliflozin

Dapagliflozin, a sodium-glucose co-transporter 2 (SGLT2) inhibitor, is indicated to improve glycaemic control in adults of type 2 diabetes. In nonclinical studies, dapagliflozin was neither genotoxic nor carcinogenic. However, in some clinical studies, an increased incidence of bladder cancer was observed in the dapagliflozin group vs. the placebo. Therefore, this study was undertaken to determine if dapagliflozin can act as a promoter in a 2-stage bladder cancer model in rats induced with N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN). Rats given BBN (100 or 400 mg/kg, po) twice weekly for 6 weeks in Phase 1 were assigned in Phase 2 to receive daily dose of vehicle, dapagliflozin (0.5 mg/kg, po) or uracil (positive control, 3% in diet) from weeks 8-34. All bladders were evaluated by histopathology. Verifying the validity of the model, uracil increased the incidence of bladder cancer, while dapagliflozin had no effect on the incidence or invasiveness of transitional cell carcinoma. The exposure of dapagliflozin at 0.5 mg/kg/day in rats was 7 times the clinical exposure at maximal therapeutic dose (10 mg). In conclusion, dapagliflozin does not act as promoter or progressor of bladder cancer in a validated bladder cancer model in rats.