Login to Access Video or Poster Abstract: MP98-11
Sources of Funding: none

Introduction

Reactive oxygen species (ROS) have been identified as important chemical mediators in cell growth and differentiation. The glutathione redox system is the main mechanism protecting against damage caused by ROS in the human body. In this study, we investigated the role and therapeutic potential of the glutathione redox system in bladder cancer.

Methods

The expression levels of glutathione peroxidase 2 (GPX2) and Ki-67 proteins were analyzed in human transurethral resection (TUR) specimens by immunohistochemistry; correlations between the GPX2 expression and prognosis were also analyzed. In addition, male F344 rats were given 0.05% BBN in drinking water and 0.1% Phenyl isothiocyanate in their diet for 36 weeks. Bladder tissue samples were collected from each animal for analyses. Furthermore, the rat cell line, BC31, and human cell lines, T24, RT4, TCC-SUP, and 5637, were transfected with GPX2 siRNA and negative control siRNA (NC).Subsequently, cell proliferation rates and ROS levels were investigated by cell counting, DCFH assay, western blotting, and flow cytometry. siRNA- or NC- transfected BC31 cells were subcutaneously implanted into nude mice.

Results

GPX2 was strongly expressed in low grade and low MIB-1 index cancers. PFS and CSS rates were significantly better in patients with higher GPX2 than in those with lower GPX2. Furthermore, GPX2 expression was significantly lower in the normal epithelium of the control group of animals with bladder cancer when compared with those in the treated group, and GPX2 expression was significantly higher in urothelial cancer than in the normal epithelium. BC31 and RT4 cells strongly expressed GPX2 when compared with the other cell lines. Silencing of GPX2 caused significant growth inhibition, and the DCFH assay revealed significant reductions in ROS levels in the siRNA- treated cells. Caspase-dependent apoptosis was fund to be the cause for the decrease in proliferation rates in the siRNA group. Interestingly, tumor growth was significantly inhibited in the BC31-implanted nude mice using the siRNA strategy for Gpx2.

Conclusions

Our findings demonstrated that GPX2 plays several important roles in carcinogenesis through the regulation of apoptosis against intracellular ROS, and may be considered as a novel marker or therapeutic target in bladder cancer.

Funding

none