Stathmin-1 is a promising prognostic factor and potential therapeutic target in urinary bladder cancer

• Aim: The oncoprotein 18/stathmin 1 (STMN1), involved in cell cycle progression and cell migration, has been reported to be expressed in several types of cancer, and is associated with clinical outcome in e.g. breast and liver cancer. The aims in this study were to investigate the clinical significance of STMN1 and to examine if STMN1 might be a possible therapeutic target in urinary bladder cancer.Experimental design: Immunohistochemical analyses of STMN1 protein expression were performed in a wide-range tissue microarray (115 Ta-, 115 T1-, 112 T2-4-tumors) and in a metastatic primary tumor/matched metastasis-material (90 patients). In the T24 cell line, the effect of STMN1 on cell proliferation was evaluated by inhibiting the cellular expression of STMN using STMN1-siRNA.Results: Patients with T1- or muscle-invasive disease exhibiting high expression of the STMN1 protein had a poorer overall survival (OS) and disease specific survival (DSS). In a multivariate analysis adjusting for stage, age and gender the results were for T2-T4 patients: OS (HR=1.77 95% CI 1.02-3.07; p=0.04) and DSS (HR=2.04 95% CI 1.13-3.68; p=0.02); for T1-4 patients: DSS (HR=1.83 95% CI 1.09-3.08; p=0.02). In the metastatic bladder cancer material, the majority of the patients with one metastasis (69%) and with several matched metastases (70%) were STMN1-positive in both the primary tumor and the matched metastases. Moreover, the ability of the urinary bladder cancer cell line to grow was significantly reduced after 72 hours (p<0.0001) when transfecting the cells with a siRNA targeting STMN1.Conclusion: Our results suggest that STMN1 protein-expression has a potential both as a prognostic marker and a novel treatment target in urinary bladder cancer.

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