The Clinical Manifestations and Specific Gene Expressions in Conventional Papillary Thyroid Carcinoma with BRAFV600E Mutation and BRAF Pseudogene

• Main Authors: Shuai-Shuai Fu, 傅帥帥
• Other Authors: Hwai-Shi Wang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/36854887744386801786

碩士 === 國立陽明大學 === 解剖學及細胞生物學研究所 === 100 === BRAFV600E is the most common point mutation found in papillary thyroid carcinomas (PTC). It may play an important role in the thyroid tumorgenesis by activating MAPK signal pathway and proposed to be a poor prognostic marker. However, the results in different studies are controversial. BRAF Pseudogene is a gene with DNA sequence similar to BRAF but having many stop codons which may not translate to a functional protein. BRAF Pseudogene was shown to activate MAPK signal pathway, but its role in thyroid cancer is still unclear. In this study, we investigated the effects of BRAFV600E mutation in the clinical manifestations, gene and protein expressions in patients with conventional PTC. The results showed that the frequency of the BRAFV600E mutation in Taiwan is high (73.1%). There is no significant difference in age, gender, tumor size, extrathyroidal invasion, nodal metastasis, distant metastasis and staging between patients with or without BRAFV600E mutation. High expression of BRAF and ERK proteins were observed in PTCs compared with normal tissues in immunohistochemistry (IHC) studies. Neither the expression of BRAF, ERK, NIS and glucotransporter 1 (GLUT1) in IHC, nor the detection of BRAF, p-ERK, and t-ERK in Western blotting correlates with BRAFV600E mutation. In the Q-PCR studies of thyroid differentiated genes, tumor invasion genes and GLUT1 expressions in PTCs, paired-normal thyroid tissues and nodular goiter tissues we found that the expression of NIS, TPO and TSHR in PTC were less than normal tissues (p<0.001, p=0.001, p<0.001, respectively). Besides, PTC expressed more MMP9 and GLUT1 than normal tissues (p<0.001, p<0.001, respectively). There is no significant difference between BRAF wild type (BRAFWT) and BRAFV600E in TPO, TSHR, MMP2, MMP9, GLUT1 and DcR3 gene expressions. However, PTCs with BRAFV600E expressed lower NIS mRNA level than BRAFWT (p=0.012). BRAF Pseudogene expression is high in conventional PTC (91.7%) and the frequency is similar in both BRAFV600E and BRAFWT. Furthermore, we overexpressed the pBRAFWT, pBRAFV600E and pBRAFpseudogene in WRO (differentiated thyroid follicular carcinoma cell line) and no significant difference in NIS, TPO, MMP9 and GLUT1 mRNA expressions were found among these three insertions. Our results showed that no significant difference in clinical- pathological features, gene and protein expressions between patients with conventional PTC harboring BRAFV600E mutation and BRAFWT in Taiwan. The only finding is the lower NIS gene expression in PTC harboring the BRAFV600E mutation suggesting the dedifferentiation of the tumor which may affect the I131 uptake in the subsequent radiotherapy. However, our present finding is not strong enough to indicate that BRAFV600E mutation is a poor prognostic marker affecting recurrent and mortality rates. Further studies are necessary to investigate the role of BRAFV600E mutation in PTC tumorigenesis.