Endoglin expression as a measure of microvessel density in cervical cancer

Objective: To evaluate endoglin, a membrane protein and member of the transforming growth factor β-1 receptor complex, as an endothelial marker of angiogenesis in cervical cancer tissues. Methods: Tumor tissue was collected from 31 surgically treated stage IB nonbulky (under 5 cm) cervical cancer subjects, and samples were fixed in formalin and embedded in paraffin. Endoglin was stained on 5-μm slide sections by the DAKO Catalyzed Signal Amplification method (DAKO Corporation, Carpinteria, CA). Factor VIII was stained by standard immunohistochemistry. Positively stained microvessels were counted in “hot spots” at 200× magnification. Clinical data were correlated with vessel counts by Spearman correlation. Mean differences in counts were tested using paired t tests. Results: This staining method for endoglin identified significantly more vessels than the factor VIII method (mean 92 ± 45 versus 33 ± 16, P < .001). Endoglin and factor VIII counts correlated significantly with deep stromal invasion (Spearman rho 0.466 and 0.522, respectively, P < .05); however, only endoglin counts correlated significantly with lymph node metastases (rho = .495, P < .01). Conclusion: Endoglin is stimulated in tumor angiogenesis and might be relatively more specific than commonly used endothelial markers. The endoglin system was more sensitive for staining capillaries in neoplastic cervical tissue, better predicted lymph node metastases, and should be widely applicable for the study of other tumors.