Amyloid precursor protein as a potential marker of malignancy and prognosis in papillary thyroid carcinoma.

Papillary thyroid carcinoma (PTC) is the most common carcinoma of the thyroid gland and has a relatively favorable prognosis. However, it is important to identify PTC characteristics that indicate a high risk for recurrence and metastasis. Recent data indicate that the amyloid precursor protein (APP) is involved in cell adhesion, motility and proliferation. At present, the expression levels of APP and their prognostic significance in PTC have not been studied. In the present study, the APP gene expression in 10 PTCs and their adjacent thyroid tissue samples was analyzed using quantitative real time-PCR. Tissue array blocks were obtained from 90 PTC cases. Tumor regions and their adjacent non-tumor regions were analyzed in tissue array blocks and immunohistochemistry was conducted using sectioned slides. Semi-quantitative scores were correlated with the clinicopathological factors of 90 PTC patients. APP-specific mRNA was increased 50-fold in PTC samples compared with their adjacent thyroid tissue. The immunohistochemistry results showed APP expression levels to be significantly increased in PTC samples compared with their adjacent non-tumor thyroid tissue (p<0.001). High APP scores were significantly correlated with large tumor size, extracapsular invasion and lymph node metastasis. The amyloid precursor protein was overexpressed in PTC and a high APP expression was associated with high malignant potential. Therefore, APP may serve as a prognostic marker and potential novel therapeutic target in PTC.