Functional analysis and clinical significance of the isocitrate dehydrogenase 2 gene in papillary thyroid carcinoma.

Objective: Mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) is a major producer of mitochondrial NADPH. IDH2-related research has focused on its mutation mechanism and its clinical significance, but the role of wild-type IDH2 in carcinoma remains controversial. Altered IDH2 levels have been identified in several types of carcinomas. However, the significance and expression of IDH2 in thyroid cancer remains unknown. Methods: We examined the expression of IDH2 in thyroid cancer and adjacent normal tissues using quantitative real-time PCR (qRT-PCR), immunohistochemical (IHC) staining analyses, and western blot analysis with frozen tissues. The relationship between IDH2 and the clinicopathological features of thyroid cancer was analyzed by IHC. Subsequently, we investigated the function of wild-type IDH2 in thyroid cancer cells in vitro. Results: We found that the mRNA expression and protein levels of IDH2 were higher in tumor than in adjacent tissues, when evaluated by qRT-PCR, western blot, and IHC analyses. Tumor size, T stage, lymph node metastasis, and TNM stage showed significant differences between the IDH2 high expression and low expression groups. Multiple logistic regression analyses indicated that tumor size and IDH2 expression were significantly correlated with the occurrence of neck LNM. Furthermore, CCK8 levels, colony formation, and invasive cell number were decreased in the sh-IDH2 groups. The upregulation of IDH2 in thyroid cancer cells showed opposite effects. Conclusion: Our results indicated that IDH2 may play an important role in the development of thyroid cancer. IDH2 can be used as a potential biomarker for diagnosis and prognosis and may be a potential therapeutic target for thyroid cancer.