分化型甲状腺癌碘-131治疗抵抗发生机制及其逆转的研究

The objectives of this project are to investigate the molecular mechanism of radioiodine therapy resistance and the reverse for differentiated thyroid carcinoma (DTC).It will be demonstrated that 131I therapy and TSH inhibition may be the causes to lead to radioiodine therapy resistance of DTC.The relationship between 131I treatment,TSH inhibition,BRAF or RAS mutation,and expression of the key moleculars of iodine metabolism with DTC radioiodine therapy resistance will be studied.The molecular mechanism of DTC radioiodine therapy resistance will be clarified to give the evidences for the treatment protocols optional of DTC. The TTF-1 gene is an upregulator of NIS and the Pax-8 gene is an upregulator of Tg and TPO.So,co- transfection of TTF-1, Pax-8 and NIS genes to radioiodine therapy resistance DTC can get synergistic effect.The DTC tumor-targeting adenovirus carriers will be developed which carry the NIS,TTF-1,and Pax-8 genes under control of the survivin promoter for reconstruction of iodine metabolism and the reverse of DTC radioiodine therapy resistance. The BRAF and RAS mutations, which mainly lead to DNA methylation and histone deacetylation, are main gene events to decrease expression of the key moleculars of iodine metabolism of DTC. Trichostatin A (TSA) is a demethylation agent , 5-azacytidine is a deacetylase inhibitor and bexarotene retorates RARB and RXRG receptors. The ability of DTC iodine uptake may be increased markedly because of the combination inducing of TSA, 5-azacytidine, bexarotene,and RA as well as Dex for redifferentiation of DTC.

探讨131I治疗和TSH抑制治疗、BRAF和RAS突变、碘代谢关键分子表达与DTC131I治疗抵抗之间的关系及其机制，试图证明反复131I治疗和长期TSH抑制是导致DTC131I治疗抵抗暨DTC失分化原因的假设，为临床合理制定131I和TSH抑制治疗提供实验和临床依据。TTF-1上调NIS表达，Pax-8上调Tg和TPO表达，以survivin启动子调控功能基因（ＮＩＳ）与调控基因（ＴＴＦ－１和Pax-8）联合转染，实现转染基因在DTC细胞的靶向性特异表达，提高摄取131I并延长有效T1/2；将抑制DNA甲基化的5－氮胞苷、抑制组蛋白脱乙酰化的TSA、上调RA核受体RARB和RXRG的蓓萨罗丁与RA，Dex进行多重组合优选，探讨联合诱导分化逆转DTC131I治疗抵抗；鉴于DTC131I抵抗的多种机制共存，所以联合基因转染和药物诱导多种手段，希在逆转DTC131I抵抗获突破进展

成功构建Ad-Sur-NIS。证明了survivin 启动子介导的NIS基因转染对恶性肿瘤细胞及荷瘤动物肿瘤病灶（实验范围内）具有靶向性和NIS表达的特异性，通过静脉注射实现了肿瘤病灶的靶向转染及NIS的特异性表达，NIS基因转染的肿瘤细胞及荷瘤动物肿瘤病灶摄取放射性碘的能力明显增高，131I对NIS基因转染的肿瘤细胞及荷瘤动物肿瘤病灶的杀伤能力明显增强。.联合抑制BRAF基因突变药物达拉菲尼和组蛋白去乙酰化药物西达苯胺增强BRAF基因突变DTC细胞BCPAP和K1细胞的摄取131I能力及延长半衰期。同时抑制BRAFV600E突变和组蛋白去乙酰化使携带BRAFV600E突变的甲状腺乳头状癌细胞碘代谢相关基因和蛋白的表达水平增高，尤其是NIS表达水平增高明显，联合应用TSH后，NIS蛋白表达更强，并且更多的NIS定位于细胞膜上； 达拉菲尼和西达苯胺联合作用在体外使携带BRAFV600E突变的甲状腺乳头状癌细胞摄碘能力增强，在TSH协同作用下，摄取能力进一步增强;药物诱导再分化联合131I治疗，可以起到很好的特异性杀伤作用；达拉菲尼和西达苯胺联合作用于体内肿瘤时，肿瘤细胞NIS蛋白表达水平明显增高，且更多定位于细胞膜上，碘摄取能力增加了约2倍，药物诱导联合131I治疗明显抑制肿瘤生长。