EMT Markers in Locally-Advanced Prostate Cancer: Predicting Recurrence?

Abstract

Background: Prostate cancer (PCa) is the second most frequent cause of cancer-related death in men worldwide. It is a heterogeneous disease at molecular and clinical levels which makes its prognosis and treatment outcome hard to predict. The epithelial-to-mesenchymal transition (EMT) marks a key step in the invasion and malignant progression of PCa. We sought to assess the co-expression of epithelial cytokeratin 8 (CK8) and mesenchymal vimentin (Vim) in locally-advanced PCa as indicators of EMT and consequently predictors of the progression status of the disease. Methods: Co-expression of CK8 and Vim was evaluated by immunofluorescence (IF) on paraffin-embedded tissue sections of 122 patients with PCa who underwent radical prostatectomies between 1998 and 2016 at the American University of Beirut Medical Center (AUBMC). EMT score was calculated accordingly and then correlated with the patients' clinicopathological parameters and PSA failure. Results: The co-expression of CK8/Vim (EMT score), was associated with increasing Gleason group. A highly significant linear association was detected wherein higher Gleason group was associated with higher mean EMT score. In addition, the median estimated biochemical recurrence-free survival for patients with < 25% EMT score was almost double that of patients with more than 25%. The validity of this score for prediction of prognosis was further demonstrated using cox regression model. Our data also confirmed that the EMT score can predict PSA failure irrespective of Gleason group, pathological stage, or surgical margins. Conclusion: This study suggests that assessment of molecular markers of EMT, particularly CK8 and Vim, in radical prostatectomy specimens, in addition to conventional clinicopathological prognostic parameters, can aid in the development of a novel system for predicting the prognosis of locally-advanced PCa.

Keywords: Gleason group; clinicopathological parameters; cytokeratin 8; epithelial-to-mesenchymal transition; prostate cancer; vimentin.

Figure 1

Representative H and E staining of PCa tissue sections that represent each of the three Gleason groups. Cross-sections of PCa tissues representing each of the three Gleason groups are stained with H and E. Left panel represents group A that includes Gleason scores 6 and 7(3+4). Middle panel represents Group B that includes Gleason score 7(4+3). Right panel represents group C that includes Gleason scores 8 and 9. Scale bars = 50 μm.

Figure 2

Representative immunofluorescent images of the co-expression of CK8/Vim molecular markers in PCa tissue specimens stained with CK8 (red), Vimentin (green), and DAPI (blue). (A) Tile scan image (5 x 5) of PCa tissue showing low EMT score <25% (scale bar = 50μm). (B) Tile scan image (5 x 5) of PCa tissue showing high EMT score ≥25% (scale bar = 50 μm). (C) Z-stack with maximal and orthogonal projection of PCa tissue showing low EMT score <25% (scale bar = 10 μm). (D) Z-stack with maximal and orthogonal projection of PCa tissue showing high EMT score ≥25% (scale bar = 10μm).

Figure 3

Biochemical recurrence-free survival curve estimating PSA failure based on the patients' EMT score. Cox regression model was built where time to PSA failure was considered time to event, and EMT score, Gleason group, pathological stage and surgical margins were added as covariates to the model. Biochemical recurrence was found to be higher in patients with EMT score ≥25% (p = 0.045).