The role of tissue factor pathway inhibitor-2 in malignant transformation of sinonasal inverted papilloma

The aim was to evaluate the potential role of tissue factor pathway inhibitor-2 (TFPI-2) in the process of malignant transformation of sinonasal inverted papilloma (SIP). We evaluated the expression of TFPI-2 in 23 SIP and 8 SIP with squamous cell carcinoma (IPcSCC), compared to 9 normal sinonasal mucosa by means of Western blot and immunohistochemistry staining. In addition, angiogenesis, vascular endothelial growth factor (VEGF) expression and microvessel density marked by CD105 staining were assessed. Correlation of TFPI-2 expression and angiogenesis in the process of malignant transformation of SIP was investigated. Western blot results demonstrated that the protein level of TFPI-2 in IPcSCC was significantly lower than that in the control group (P < 0.01). In addition, significant difference in TFPI-2 protein expression between SIP and IPcSCC was detected (P < 0.01). Higher number of microvessel per unit area (MVNA) was observed in IPcSCC compared to SIP (P < 0.01). Correlational analysis indicated positive correlation of VEGF and MVNA (r = 0.735), inverse correlation of TFPI-2 and MVNA (r = -0.318). However, no significant correlation between TFPI-2 and VEGF was detected. We conclude that TFPI-2 might be a regulatory molecule in the malignant potential of SIP. Down regulation of TFPI-2 is associated with increased MVNA in IPcSCC, which may be involved in the process of malignant transformation of SIP.