Expert review: an update in current and developing intravesical therapies for non-muscle-invasive bladder cancer

Prognostic Value of BUB1 for Predicting Non-Muscle-Invasive Bladder Cancer Progression

Non-muscle-invasive bladder cancer (NMIBC) is a common disease with a high recurrence rate requiring lifetime surveillance. Although NMIBC is not life-threatening, it can progress to muscle-invasive bladder cancer (MIBC), a lethal form of the disease. The management of the two diseases differs, and patients with MIBC require aggressive treatments such as chemotherapy and radical cystectomy. NMIBC patients at a high risk of progression benefit from early immediate cystectomy. Thus, identifying concordant markers for accurate risk stratification is critical to predict the prognosis of NMIBC. Candidate genetic biomarkers associated with NMIBC prognosis were screened by RNA-sequencing of 24 tissue samples, including 16 NMIBC and eight normal controls, and by microarray analysis (GSE13507). Lastly, we selected and investigated a mitotic checkpoint serine/threonine kinase, BUB1, that regulates chromosome segregation during the cell cycle. BUB1 gene expression was tested in 86 NMIBC samples and 15 controls by real-time qPCR. The performance of BUB1 as a prognostic biomarker for NMIBC was validated in the internal Chungbuk cohort (GSE13507) and the external UROMOL cohort (E-MTAB-4321). BUB1 expression was higher in NMIBC patients than in normal controls (p < 0.05), and the overexpression of BUB1 was correlated with NMIBC progression (log-rank test, p = 0.007). In in vitro analyses, BUB1 promoted the proliferation of bladder cancer cells by accelerating the G2/M transition of the cell cycle. Conclusively, BUB1 modulates the G2/M transition to promote the proliferation of bladder cancer cells, suggesting that it could serve as a prognostic marker in NMIBC.

Apaziquone for Nonmuscle Invasive Bladder Cancer: Where Are We Now?

Apaziquone is an interesting drug for intravesical use in patients with nonmuscle invasive bladder cancer; however, more research is needed to prove its actual benefit. Although the apaziquone trials demonstrate the potential of this new drug, the singular phase 3 trials did not reach their primary endpoint. To date, no new trials are recruiting, so the development of apaziquone seems to have stopped.

Cytotoxic and toxicogenomic effects of silibinin in bladder cancer cells with different TP53 status

Silibinin is a natural phenol found in the seeds of the milk thistle plant. Recent data have shown its effectiveness for preventing/treating bladder tumours. Therefore, in this study we investigated the cytotoxic and toxicogenetic activity of silibinin in bladder cancer cells with different TP53 statuses. Two bladder urothelial carcinoma cell lines were used: RT4 (wild-type TP53 gene) and T24 (mutated TP53 gene). Cell proliferation, clonogenic survival, apoptosis rates, genotoxicity and relative expression profile of FRAP/mTOR, FGFR3, AKT2 and DNMT1 genes and of miR100 and miR203 were evaluated. Silibinin promoted decreased proliferation and increased late apoptosis in TP53 mutated cells. Increased early apoptosis rates, primary DNA damage, and decrease of cell colonies in the clonogenic survival assay were detected in both RT4 and T24 cell lines. Down-regulation of FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 expression occurred in RT4 cells. Modulation of miR203 was observed in both cell lines. In conclusion, despite the reduction of clone formation in both cell lines, the toxicogenomic effect of silibinin on FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 was dependent on the TP53 status. Taken together, the data confirmed the role of silibinin as an antiproliferative compound, whose mechanism of action was related to the TP53 status.

Metabolic coupling in urothelial bladder cancer compartments and its correlation to tumor aggressiveness

Monocarboxylate transporters (MCTs) are vital for intracellular pH homeostasis by extruding lactate from highly glycolytic cells. These molecules are key players of the metabolic reprogramming of cancer cells, and evidence indicates a potential contribution in urothelial bladder cancer (UBC) aggressiveness and chemoresistance. However, the specific role of MCTs in the metabolic compartmentalization within bladder tumors, namely their preponderance on the tumor stroma, remains to be elucidated. Thus, we evaluated the immunoexpression of MCTs in the different compartments of UBC tissue samples (n = 111), assessing the correlations among them and with the clinical and prognostic parameters. A significant decrease in positivity for MCT1 and MCT4 occurred from normoxic toward hypoxic regions. Significant associations were found between the expression of MCT4 in hypoxic tumor cells and in the tumor stroma. MCT1 staining in normoxic tumor areas, and MCT4 staining in hypoxic regions, in the tumor stroma and in the blood vessels were significantly associated with UBC aggressiveness. MCT4 concomitant positivity in hypoxic tumor cells and in the tumor stroma, as well as positivity in each of these regions concomitant with MCT1 positivity in normoxic tumor cells, was significantly associated with an unfavourable clinicopathological profile, and predicted lower overall survival rates among patients receiving platinum-based chemotherapy. Our results point to the existence of a multi-compartment metabolic model in UBC, providing evidence of a metabolic coupling between catabolic stromal and cancer cells' compartments, and the anabolic cancer cells. It is urgent to further explore the involvement of this metabolic coupling in UBC progression and chemoresistance.