Association Between CKAP4 Expression and Poor Prognosis in Patients with Bladder Cancer Treated with Radical Cystectomy.

Background/Objectives: While cytoskeleton-associated protein 4 (CKAP4) has been associated with prognosis in various malignancies, its prognostic value for bladder cancer (BCa) remains unclear. The aim of this study was to evaluate CKAP4 expression in tumor cells and cancer-associated fibroblasts (CAFs) following radical cystectomy (RC) in patients with BCa. Methods: In this study, CKAP4 in tumor cells was defined as CKAP4-1, while CKAP4 expressed in CAFs was defined as CKAP4-2. CKAP4-2 expression was evaluated to explore its potential association with tumor aggressiveness and patient outcomes. CKAP4 expression in 86 RC specimens was assessed using immunohistochemistry. CKAP4-1 positivity was considered when ≥5% cytoplasmic staining of cancer cells, with at least moderate staining intensity, was observed. CKAP4-2 positivity was evaluated using a point scale (0-3), with scores based on the number of CKAP4 positive CAFs in the tumor stroma. Scores of 2 (moderate number of CAFs) and 3 (significant number of CAFs) were considered to indicate positivity. Results: CKAP4-1 and CKAP4-2 were expressed in 53 (61.6%) and 34 (39.5%) patients, respectively. Kaplan-Meier analysis showed that patients with CKAP4-1 had significantly shorter cancer-specific survival and recurrence-free survival (RFS; p = 0.046 and p = 0.0173, respectively). Multivariate analysis showed that CKAP4-1 positivity was an independent predictor of RFS (p = 0.041, hazard ratio: 2.09, 95% confidence interval: 1.03-4.25). Conclusions: This study showed that CKAP4 expression in tumor cells may serve as a useful prognostic biomarker for patients with BCa who undergo RC.