Prognostic Impact of Canonical TGF-β Signaling in Urothelial Bladder Cancer

Abstract

Background and objectives: Dysregulation of TGF-β signaling plays multiple roles in cancer development and progression. In the canonical TGF-β pathway, TGF-β regulates the expression of hundreds of target genes via interaction with Smads, signal transducers and transcriptional modulators. We evaluated the association of TGF-β1, Smad2, and Smad4, the key components of canonical TGFβ pathway, with clinicopathologic characteristics of urothelial bladder cancer, and assessed their prognostic value in prediction of patients' outcome. Materials and Methods: Immunohistochemical analysis of TGF-β1, Smad2, and Smad4 expression was performed on 404 urothelial bladder cancer samples, incorporated in tissue microarrays. Expression status was correlated with clinicopathological and follow-up data. The median follow-up was 61 months. Results: High expression of TGF-β1, Smad2, and Smad4 was detected in 68.1%, 31.7% and 45.2% of the tumors, respectively. TGF-β1 overexpression was significantly associated with high tumor grade, and advanced pathologic stage (p < 0.001, respectively). Conversely, high Smad2 and Smad4 expression was linked to low tumor grade (p = 0,003, p = 0.048, respectively), and low tumor stage (p < 0.001, p = 0.003, respectively). Smad2 showed an inverse correlation with variant morphology and divergent differentiation of urothelial tumors (p = 0.014). High TGF-β1 correlated directly, while Smad2 and Smad4 correlated inversely to cancer-specific death (p = 0.043, p = 0.003, and p = 0.022, respectively). There was a strong relationship between Smad2 and Smad4 expression (p < 0.001). Survival analyses showed that high Smad2 and Smad4 expression was associated with longer overall survival (p = 0.003, p = 0.034, respectively), while in multivariate regression analysis TGF-β1 manifested as an independent predictor of poor outcome. Conclusions: Unraveling the complex roles and significance of TGF-β signaling in urothelial bladder cancer might have important implications for therapy of this disease. Assessment of TGF-β pathway status in patients with urothelial bladder cancer may provide useful prognostic information, and identify patients that could have the most benefit from therapy targeting TGF-β signaling cascade.

Keywords: Smad2; Smad4; TGF-β; immunohistochemistry; prognosis; urothelial bladder cancer.

Figure 1

Representative photomicrographs of haematoxylin–eosin stain and immunohistochemical staining to TGF-β1, Smad2, and Smad4 in urothelial bladder cancer; first row—papillary non-invasive low grade tumor (pTa); second row—superficially invasive low grade tumor (pT1); third row—superficially invasive high-grade tumor (pT1); fourth row—muscle-invasive urothelial bladder cancer (pT2). Original magnification ×400.

Figure 2

Kaplan–Meier survival curves showing overall survival in 404 patients with urothelial bladder cancer in relation to expression of TGF-β1, Smad2 and Smad4 in cancer cells. Log Rank (Mantel–Cox) test.