Members of the Aurora kinase family are involved in the regulation of mitosis, and alterations in their expression have been associated with malignant transformation. Despite that, few information are available regarding the expression of these proteins in normal or transformed human thyrocytes. Thus, we evaluated, by means of western blot (WB), real-time PCR (RT-PCR) and immunofluorescence (IF), the expression and cellular localization of all members of the Aurora family (A, B and C) in human cell lines derived from normal thyrocytes (HTU5), follicular adenoma (HTU42), follicular (FTC-133), papillary (B-CPAP) and anaplastic (8305C) carcinomas. The different cell types, cultured in the appropriate culture media, were used to prepare total RNA or protein cell extracts or fixed for IF experiments. The WB and RT-PCR analysis demonstrated a low level of expression of all kinases in normal thyrocytes. Similarly, a low expression was present in the HTU42 cells. On the contrary, WB experiments showed a remarkable increase (P<0.01) of the three kinases in all the thyroid carcinoma cell lines. This feature was confirmed by the RT-PCR analysis, showing an increased expression (P<0.01) of Aurora A and B mRNAs, ranging from 3 to 7 fold with respect to the HTU5 cells, in the thyroid carcinoma cell lines. Interestingly, for Aurora C no significant changes in the mRNA levels were observed, suggesting the presence of post-transcriptional mechanism(s) controlling its expression. The IF experiments showed that Aurora A localizes at the centrosome of mitotic cells while Aurora B is located in the centromere of metaphase chromosomes, in the spindle midzone during anaphase and in the midbody during cytokinesis. In conclusions, we demonstrated the expression of all members of the Aurora family in normal human thyrocytes, and proved that their overexpression characterize malignant, but not benign, thyroid tumor derived cell lines
