Molecular markers of prognosis and novel therapeutic strategies for urothelial cell carcinomas

RGS6 is an essential tumor suppressor that prevents bladder carcinogenesis by promoting p53 activation and DNMT1 downregulation

Urinary bladder cancer (UBC) is largely caused by exposure to toxic chemicals including those in cigarette smoke (i.e. BBN). An activating SNP in RGS6 is associated with a pronounced reduction in UBC risk, especially among smokers. However, the mechanism underlying this reduction remains unknown. Here we demonstrate that RGS6 is robustly expressed in human urothelium, where urothelial cell carcinoma originates, and is downregulated in human UBC. Utilizing RGS6-/- mice we interrogated a possible role for RGS6 as a tumor suppressor using the BBN-induced bladder carcinogenesis model that closely recapitulates human disease. As in humans, RGS6 is robustly expressed in mouse urothelium. RGS6 loss dramatically accelerates BBN-induced bladder carcinogenesis, with RGS6-/- mice consistently displaying more advanced pathological lesions than RGS6+/+ mice. Furthermore, BBN treatment promotes urothelial RGS6 mRNA and protein downregulation. RGS6 loss impairs p53 activation and promotes aberrant accumulation of oncogenic protein DNMT1 in urothelium. Tumor suppressor RASSF1A, a DNMT1-regulated gene, is also silenced, likely via methylation of its promoter during BBN exposure. We hypothesize that this BBN-induced RGS6 loss represents a critical hit in UBC as it irrevocably impairs the anti-proliferative actions of the ATM/p53 and RASSF1A pathways. Consistent with these findings, RGS6-/- mice treated with CP-31398, a p53-stablizing agent, and/or 5-Aza, a DNMT1 inhibitor, are protected from BBN-induced tumorigenesis. Together, our data identify RGS6 as a master tumor suppressor modulating two critical signaling pathways that are often dysregulated in UBC; therefore, RGS6 represents a potential novel biomarker for UBC diagnosis/prognosis and an appealing new target in its treatment.

New and promising strategies in the management of bladder cancer

Bladder cancer is a complex and aggressive disease for which treatment strategies have had limited success. Improvements in detection, treatment, and outcomes in bladder cancer will require the integration of multiple new approaches, including genomic profiling, immunotherapeutics, and large randomized clinical trials. New and promising strategies are being tested in all disease states, including nonmuscle-invasive bladder cancer (NMIBC), muscle-invasive bladder cancer (MIBC), and metastatic urothelial carcinoma (UC). Efforts are underway to develop better noninvasive urine biomarkers for use in primary or secondary detection of NMIBC, exploiting our genomic knowledge of mutations in genes such as RAS, FGFR3, PIK3CA, and TP53 and methylation pathways alone or in combination. Recent data from a large, randomized phase III trial of adjuvant cisplatin-based chemotherapy add to our knowledge of the value of perioperative chemotherapy in patients with MIBC. Finally, bladder cancer is one of a growing list of tumor types that respond to immune checkpoint inhibition, opening the potential for new therapeutic strategies for treatment of this complex and aggressive disease.

Alterations of dendritic cell subsets and TH1/TH2 cytokines in the peripheral circulation of patients with superficial transitional cell carcinoma of the bladder

BACKGROUND

Dendritic cells (DCs) and cytokines play an important role in the tumor growth and recurrence.

METHODS

Sixty-six patients with superficial transitional cell carcinoma of the bladder (STCCB) and 38 healthy controls were studied to investigate the percentages of DC subsets, monocyte-derived DC (MoDC) function, and alterations of Th1 and Th2 cytokines. MoDCs were generated and three-color flow cytometry was used for determining the phenotype of MoDCs and DC subsets. The ability to stimulate autologous T cells was tested in mixed leukocyte reaction (MLR). The levels of various cytokines were measured using commercially available sandwich enzyme linked immunosorbent assay (ELISA) kit.

RESULTS

The myeloid DC (mDC) counts, MoDC surface molecular expression, and stimulatory capacity to T cells were impaired in STCCB patients than in controls. The percentage of mDC and the expression of CD80, CD83, and CD86 were lower in patients showing recurrence. The serum levels of IL-2 and IFN-γ were found to be significantly lower while IL-4, IL-6, and IL-10 were significantly higher in STCCB patients than in controls. IL-6 was found to be significantly higher in recurrent patients.

CONCLUSION

The impairment of mDC counts and MoDC function with imbalance of Th1/Th2 cytokines was closely associated with proliferation and recurrence of STCCB.

Molecular markers in transitional cell carcinoma of the bladder: New insights into mechanisms and prognosis

Urothelial carcinoma is potentially life-threatening and expensive to treat since for many patients, the diagnosis entails a lifetime of surveillance to detect recurrent disease. Advancements in technology have provided an understanding of the molecular mechanisms of carcinogenesis and defined distinct pathways in tumorigenesis and progression. At the molecular level, urothelial carcinoma is being seen as a disease with distinct pathways of carcinogenesis and progression and thus markers of these processes should be used as both diagnostics and predictors of progression and patient outcome. Herein we present a selective overview of the molecular underpinning of urothelial carcinogenesis and progression and discuss the potential for proteins involved in these processes to serve as biomarkers. The discovery of biomarkers has enabled the elucidation of targets for novel therapeutic agents to disrupt the deregulation underlying the development and progression of urothelial carcinogenesis.

Immunoscreening of urinary bladder cancer cDNA library and identification of potential tumor antigen

OBJECTIVE

To identify potential tumor antigen by immunoscreening the urinary bladder cancer cDNA library with monoclonal antibodies.

METHODS

Monoclonal antibodies were prepared. A cDNA expression library was constructed from bladder cancer cell line BLZ211. Immunogenic proteins were identified by immunoscreening the cDNA library with ten monoclonal antibodies.

RESULTS

The cDNA library of BLZ211 cells was established using lambdaZAP as vector. The titer of unamplified cDNA library was 1.39x10(6) pfu/ml with a recombinant rate of 97.72%, and titer of amplified one was 8.4x10(9) pfu/ml. After immunoscreening, ten positive clones representing ten different antigens were identified, which include two proteins with unknown function; coactosin-like 1, eukaryotic translation elongation factor, HNRPA1, histidine triad nucleotide binding protein, KRT7, LCN2, TSTA3, zinc finger protein, C11orf48 and HSPC148.

CONCLUSION

The cDNA library was of high quality and can be used in further study. By immunoscreening the bladder cancer cDNA library with ten monoclonal antibodies, we identified ten immunogenic proteins that otherwise would not have been identified as potential diagnostic marker and vaccinogens of bladder cancer using the gene discovery effort.