Objective: Securin, the product of PTTG (pituitary tumor transforming gene), is overexpressed in several tumors, and plays important roles in cancer progression and invasion. In our previous report, securin expression was observed in transitional cell carcinoma (TCC; the most common pathological pattern of bladder cancer) cell lines, including BFTC905, T24, and TSGH8301. However, the existence of securin in human bladder cancer specimens has not been established. Materials and Methods: Commercial bladder cancer tissue arrays (BL208 & BLC661) were used. Slides of paraffin-fixed human bladder tissues included all grades of TCC (18, 22 and 29 tissue samples for grades I, II, and III, respectively), 21 superficial and 41 invasive TCC specimens, and 11 normal urothelial tissue samples. The intensities of securin immunostaining were graded as background, mild, and strong (scored as 0, 1, and 2, respectively), and scores from the nucleus and cytosol were analyzed separately. Results: We have demonstrated, for the first time, the expression of securin in bladder tissues. Securin was overexpressed in the cytosol and nucleus of all TCC samples compared to normal urothelium, but only cytosolic localization revealed statistical significance. There were no differences in securin immunoreactivity among the different grades of TCC. Significant over-expression of cytosolic but not nuclear securin was found in both superficial and invasive TCC samples compared to normal urothelium. No difference in immunoreactive staining for nuclear and cytosolic securin between superficial and invasive TCC was noted. Conclusion: Significant enhanced expression of cytosolic securin protein was found in human bladder cancer specimens, suggesting that the level of tissue securin may be a potential biomarker for the diagnosis of bladder cancer. Studies that investigate the relationship between securin expression and the outcomes of bladder cancer patients could be conducted in the future.
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