Method for in vitro diagnosis of thyroid carcinoma

The present invention concerns a method for in vitro diagnosis of thyroid carcinoma by detecting the localization of FBXO34 protein. Benign and malignant thyroid neoplasms appear through pathological features of thyroid nodules (TN). Nodular lesions are quite common in the general population. To date cyto-pathological examination of thyroid fine needle aspiration biopsy (FNAB) specimens represents the best available way to distinguish benign from malignant thyroid lesions in pre-operatory stage. The major limit of thyroid FNAB is represented by the category of Thy3, the so-called “indeterminate” samples, usually encountered in 15-30% of nodules aspirated. In the absence of valid indications, very often these indeterminate cases undergo unnecessary surgery. In the light of the above it is therefore apparent the need to provide for new methods for diagnosis of thyroid carcinoma able to overcome the disadvantages of known diagnostic methods. FBXO34 is a 78,711 Da molecular mass protein, including 711 amino acids and belonging to F-box protein family, which include a total of 39 members. The common genetic trait of this family is the F-box protein motif, consisting in approximately 40 amino acids. F-box proteins are best known for their role as the substrate-recognition components of the SKP1/CUL1/F-box protein (SCF) class of E3 ubiquitin ligases. FBXO34 shows a double localization in malignant follicular and parafollicular thyroid cells, i.e. it appears both in nucleus and cytoplasm, whereas it shows a unique nuclear localization in normal and benign follicular thyroid cells. The results are based on three different lines of evidences, namely western blot analysis, immunoflorescent experiments and immunohistochemistry. The experiments were performed “in vitro” on human thyroid cancer cell lines and “ex vivo” in surgically excised human thyroid tissue samples. The delocalization of FBOX34 protein in the cytoplasm, which has been observed in thyroid cancer, allows setting up a new analytic diagnostic method to distinguish directly benign from malignant lesions by analyzing cytological samples obtained by FNA. The subcellular immunohistochemical expressions of FBOX34 represent, therefore, a new diagnostic marker able to further ameliorate the recognition of thyroid cancer especially in those lesions that remain “indeterminate” after conventional cytological analysis.