Detection of circulating tumor cells by p75NTR expression in patients with esophageal cancer

BACKGROUND: The p75 neurotrophin receptor (p75NTR) is a cancer stem cell (CSC) marker in esophageal squamous cell carcinoma (ESCC). This study aimed to assess the use of p75NTR in detecting circulating tumor cells (CTCs) in ESCC. METHODS: Peripheral blood mononuclear cell expression of epithelial cell adhesion molecule (EpCAM) and p75NTR was detected in 23 ESCC patients (13 received chemo- or chemoradiotherapy and 10 received curative surgery) and 10 healthy controls by flow cytometry. RESULTS: EpCAM + p75NTR+ cell counts (average ± SD) were significantly higher in patients (n = 23, 16.0 ± 18.3) compared to controls (n = 10, 0.4 ± 0.9, p = 0.013). The sensitivity and specificity to differentiate ESCC patients from controls were 78.3 and 100 % (cut-off value 4.0), respectively. EpCAM + p75NTR+, but not EpCAM + p75NTR− cell counts, correlated with clinically diagnosed distant metastasis (n = 13, p = 0.006) and pathological venous invasion in resected primary tumors (n = 10, p = 0.016). Malignant cytology was microscopically confirmed in isolated EpCAM + p75NTR+ cells with immunocytochemical double staining. CONCLUSIONS: p75NTR is suggested to be a useful marker for clinically significant CTCs, which exhibit highly metastatic features in ESCC.