Objective: Nitric oxide (NO) and endothelin-1 (ET-1) are involved in carcinogenesis. Overexpression of the ET-1 axis has been demonstrated in papillary thyroid carcinoma (PTC). This study investigated the expression of NO synthases (NOS) and their relationship with expression of ET-1 and angiogenic markers in PTC.
Design and patients: Expression of NOS, angiogenic markers [vascular endothelial growth factor (VEGF), angiopoietin-1 and angiopoietin-2] and their receptors was studied in surgical thyroid samples obtained from 22 patients aged 15-68 years. Three groups were constituted: normal thyroid (n = 5), Hashimoto's thyroiditis (n = 9) and PTC (n = 8).
Results: Immunohistochemistry disclosed NOS2 and NOS3 immunoreactivity in PTC cells, the percentage of positive cells being greater than normal (P < 0.02). Real-time quantitative polymerase chain reaction (RTQ-PCR) showed that NOS2 and NOS3 mRNA levels were, respectively, increased (P < 0.02) by 2.6 +/- 0.6 and 4.2 +/- 1.1 times in PTC. RTQ-PCR demonstrated that VEGF, its receptors VEGFR-1 and VEGFR-2, and angiopoietin-2 and its receptor (Tie2) were also overexpressed (P < 0.05) in PTC. Correlations were found between ET-1 expression and that of NOS2, angiopoietin-1 and -2 (P < 0.05). NOS2 mRNA levels also correlated with those of NOS3 and angiopoietin-2 (P < 0.05). In thyroiditis, NOS2 immunoreactivity was observed in inflammatory cells whereas NOS2 mRNA levels were 12.1 +/- 1.6 times higher than normal (P < 0.005).
Conclusions: This study revealed an activation of the NO pathway in thyroid carcinoma, which is interrelated to the ET-1 axis, both systems being overexpressed in concert with angiogenic factors. This global system might play a role in carcinogenesis and constitutes a potential target for anticancer therapy.