Evaluating the Expression of Survivin and Its Splice Variants 2B and ΔEx3 as New Diagnostic Molecular Markers in Thyroid Cancer Vandghanooni S1, Hosseinpour Feizi MA1, Babaei E1,2, Montazeri V3, Halimi M3 1 Dept of Biology, School of Nature Sciences, Tabriz University, Tabriz, Iran 2 Dept of Genetics, Faculty of Basic Sciences, Tarbiat Modarres University, Tehran, Iran 3 Imam Khomeini Hospital, School of Medicin, Tabriz University of Medical Sciences, Tabriz, Iran Corresponding Author's Address: Dept of Biology, School of Nature Science, Tabriz University, Tabriz, Iran E-mail: pourfeizi@eastp.ir Received: 12 July, 2008 Accepted: 13 Dec, 2008 Background and Objective: Thyroid cancer is the most common endocrine malignancy. Because of the highly heterogeneous nature of tumoral and non-tumoral thyroid nodules and lack of suitable clinico-pathological criteria and absence of appropriate molecular markers, scientists have been trying to find a molecular tumor marker for specific diagnosis of thyroid tumors. Recent attention has been paid to Survivin, a novel member of the Inhibitor of Apoptosis Protein Family (IAP), as a new molecular marker in cancer. Studies have demonstrated that Survivin and its splice variants have different expression in cancerous tissues compared to normal tissues. Materials and Methods: In this study the expression of Survivin and its splice variants 2B and ΔEx3 were evaluated as new diagnostic molecular markers in thyroid cancer. Tissue samples were collected from 61 thyroid specimens including 14 tumor margins, 11 non-tumoral and 36 tumoral samples. Expression levels of Surviving and its variants were measured by semi quntitative RT-PCR. Results: Expression level of Survivin in tumor samples was significantly higher compared with surgical margins and non tumural tissues. There was also a significant increase in expression level of Survivin-∆Ex3 in tumoral tissues compared with surgical margins. The expression of Survivin 2B in tumors was lower than the non-tumoral tissues. Conclusion: Our data indicated the important role of Survivin in production of thyroid tumors and also revealed that high expression of ∆Ex3 variant is correlated with nature of thyroid tumors. Therefore, evaluating Survivin gene expression and its recently introduced splice variants may be used in diagnosis and classification of thyroid tumors from non-tumoral lesions.