The ratio of serum Angiopoietin-1 to Angiopoietin-2 in patients with cervical cancer is a valuable diagnostic and prognostic biomarker

Abstract

Objectives: Angiopoietins have been found to play essential roles in tumor angiogenesis. The present study was aimed at investigating the diagnostic and prognostic values of serum angiopoietin 1 and 2 (sAng-1 and sAng-2) in cervical cancer.

Methods: The sAng-1 and sAng-2 concentrations were analyzed in 77 women with cervical cancer, 44 women with cervical intraepithelial neoplasia (CIN) and 43 women without cervical lesions by enzyme-linked immunosorbent assay. The diagnostic values of sAng-1, sAng-2 and sAng-1/sAng-2 were evaluated by receiver operating characteristic (ROC) curves. The Ang-1 and Ang-2 expression in cervical cancer tissues as well as microvessel density (MVD), were assessed by immunohistochemistry.

Results: The concentration of sAng-2 gradually increased and the sAng-1/Ang-2 ratio was gradually decreased from normal control to CIN, then to squamous cell cancer, and the sAng-1/sAng-2 ratio was also significantly decreased in adenocarcinoma. The area under ROC curves of sAng-2 and sAng-1/sAng-2 ratio for discriminating cervical cancer from normal were 0.744 and 0.705, respectively. Decreased sAng-1/sAng-2 was significantly associated with advanced tumor stage, poor differentiation, lymph-vascular space invasion and high MVD. sAng-2 was positively correlated with the Ang-2 expression in cervix epithelia. A high sAng-1/sAng-2 ratio was associated with a longer progression-free survival and a longer overall survival in cervical cancer patients.

Conclusions: These findings suggest that sAng-2 and the sAng-1/sAng-2 ratio may be valuable diagnostic and prognostic biomarkers for cervical cancer.

Keywords: Angiogenesis; Cervical cancer; Diagnostic biomarker; Serum angiopoietin; Survival.

Figure 1. sAng-2 concentration and sAng-1/sAng-2 ratio are altered in patients with cervical neoplasia.

sAng-1 and sAng-2 concentrations in 43 patients of normal control, 44 CIN patients, and 77 cervical cancer patients (62 CSCC patients and 15 CADC patients) were determined by ELISA. The differences in Ang-1 (A), sAng-2 (B), and the sAng-1/sAng-2 ratio (C) between groups are shown.

Figure 2. sAng-2 concentration and the sAng-1/sAng-2 ratio are valuable diagnostic biomarkers for cervical lesions.

The ROC curves of sAng-2 for discriminating CSCC from normal (A), CSCC from CIN (B), CSCC from normal and CIN (C), CIN and CSCC from normal (D), and invasive cervical cancer from normal (E). The cutoff values of sAng-2 and corresponding sensitivity and specificity to distinguish CSCC from normal are shown (F). The ROC curves of sAng-1/sAng-2 for discriminating CIN from normal (G), CSCC from normal (H), CIN and CSCC from normal (I) and invasive cervical cancer from normal (J). The cutoff values of sAng-1/ sAng-2 and corresponding sensitivity and specificity to distinguish CSCC from normal are listed (K).

Figure 3. sAng-2 concentration positively relates with Ang-2 expression on the epithelia and MVD in cervical tissues.

Representative immunohistochemical staining of Ang-1 (A), Ang-2 (B) and CD34 (C) in 25 cervical cancer tissue specimens and 10 normal controls. Black arrows denote positively stained epithelial cells, whereas red arrows denote positively staining endothelial cells, all appearing brown. Scale bar, 20 µm. (D) sAng-2 is significantly higher in the patients with positive Ang-2 expression on cervix epithelia than those with negative Ang-2 expression. The scatter diagrams show the correlations of sAng-1 (E), sAng-2 (F) and sAng-1/ sAng-2 ratio (G) to MVD in the 35 cervical tissue specimens.

Figure 4. High sAng-1/sAng-2 ratio predicts poorer survival in cervical cancer patients.

Kaplan–Meier survival analysis of the progression-free survival and the overall survival among 66 cervical cancer patients stratified by sAng-1 (A, B), sAng-2 (C, D) and sAng-1/sAng-2 ratio (E, F).