Overexpression levels of cripto-1 predict poor prognosis in patients with prostate cancer following radical prostatectomy

Abstract

Overexpression of cripto-1 (CR-1), an epidermal growth factor-cripto-1/FRL-1/Cryptic family protein, has been reported in multiple types of malignancy. However, the clinical functions of CR-1 in prostate cancer (PCa) remain largely unclear. The objective of the present study was to investigate the association between CR-1 expression and the clinicopathological features and prognosis of PCa. CR-1 expression was evaluated in 138 PCa tissues and 67 benign prostate hyperplasia (BPH) tissues using immunohistochemistry. The association between the clinicopathological features of patients with PCa and CR-1 expression was analyzed using a χ² test. Receiver operating characteristic (ROC) curve and Cox regression model were used to analyze the association between CR-1 expression and biochemical recurrence (BCR)-free survival. It was revealed that the protein expression of CR-1 was markedly higher in PCa tissues than in BPH tissues. The mRNA expression of CR-1 in PCa tissue and cells was also significantly higher than in BPH tissue and the normal RWPE-1 prostate cell line (P<0.05). In addition, high CR-1 expression was significantly associated with prostate-specific antigen level (P=0.008), Gleason score (P=0.011) and lymph node metastasis (P=0.025) in patients with PCa. ROC curve indicated that patients with elevated expression of CR-1 exhibited shorter BCR-free survival (P<0.001). Furthermore, multivariate statistical analysis demonstrated that overexpression of CR-1 may be a novel predictor for prognosis of patients with PCa. Accordingly, the present study considered CR-1 to be a valuable predictor of poor prognosis and progression in PCa, and a potential therapeutic target for patients with PCa.

Keywords: cripto-1; gene expression; prognosis; prostate cancer.

Figure 1.

Immunohistochemistry analysis of CR-1 expression. (A) Low expression (0–4) of CR-1 in adjacent non-tumor BPH tissues. (B) High expression (–12) of CR-1 in PCa tissues. Magnification, ×100. Insert magnification, ×400. CR-1, cripto-1; PCa, prostate cancer; BPH, benign prostate hyperplasia.

Figure 2.

Relative expression of CR-1 mRNA in PCa and BPH tissues and in prostate cells. (A) CR-1 levels in BPH tissues were regarded as 100%, and PCa tissues were compared with BPH tissues. CR-1 mRNA was significantly increased in PCa tissues compared with BPH tissues. **P<0.05 vs. BPH tissue. (B) Relative expression of CR-1 mRNA in prostate cells. CR-1 levels in RWPE-1 cells were regarded as 100% and RWPE-1 was compared with PC-3 and LNCap. CR-1 mRNA was significantly increased in PC-3 and LNCaP compared with RWPE-1. **P<0.05 vs. RWPE-1. CR-1, cripto-1; PCa, prostate cancer; BPH, benign prostate hyperplasia; RT-qPCR, reverse transcription-quantitative PCR.

Figure 3.

CR-1 gene expression in prostate tissues and PC-3 cells. (A) CR-1 levels in PCa and non-cancerous BPH tissues were detected using western blot analysis, with β-actin as the internal reference. T represents PCa tissues and N represents non-cancerous BPH tissues and the numbers represent tissues from 2 different patients. (B) Immunofluorescence staining for CR-1 protein in PC-3 cells and RWPE-1 cells. PC-3 and RWPE-1 cells were immunostained for CR-1 (green). Nuclei were visualized by DAPI staining (blue). CR-1 protein is mainly located in the cytoplasm of cells (magnification, ×400). CR-1, cripto-1; PCa, prostate cancer; BPH, benign prostate hyperplasia.

Figure 4.

The BCR-free survival of patients with PCa was estimated by Kaplan-Meier analysis. Patients with high CR-1 expression showed significantly shorter BCR-free survival compared with those with low CR-1 expression (P<0.001). CR-1, cripto-1; PCa, prostate cancer; BPH, benign prostate hyperplasia; BCR, biochemical recurrence.