schmutzler C, Brtko J, Winzer R, Jakobs T C, Meissner-Weigl J, Simon D, Goretzki P E, Köhrle J
Klinische Forschergruppe, Medizinische Poliklinik, Universität Würzburg, Germany.
Int J Cancer. 1998 May 4;76(3):368-76. doi: 10.1002/(sici)1097-0215(19980504)76:3<368::aid-ijc14>3.0.co;2-7.
Thyroid carcinomas no longer accessible to radio-iodide or TSH-suppressive T4 therapy, due to loss of thyroid-specific functions, might be sufficiently re-differentiated by retinoic acid (RA) to be treated by conventional methods again. To help evaluate the feasibility of RA re-differentiation therapy in thyroid carcinomas, we examined the functionality of RA receptors (RARs/RXRs), central RA signal mediators, in human thyroid-carcinoma cell lines as model systems. [3H]-RA binding assays with nuclear extracts from follicular thyroid-carcinoma cell lines FTC-133 and -238 revealed high-affinity binding sites for RA. Electrophoretic mobility shift and super-shift assays using a DR2 ("direct repeat" 2) RA response element demonstrated DNA-binding of RARalpha, RARgamma, RXRalpha and RXRbeta in nuclear extracts of FTC-133 and anaplastic HTh74 cells. Use of a DR5 RA response element revealed no difference in DNA binding. In supershift assays with a DR4 T3 response element, we found DNA-binding by TRalpha1, TRalpha2, and TRbeta. Northern-blot analysis showed low expression of RXRbeta mRNA in FTC-133 and of TRalpha1 mRNA in FTC-133 and FTC-238 cells. Using RT-PCR, we detected mRNA for RARalpha, RARbeta, RARgamma, RXRalpha, and RXRbeta in the 4 cell lines and in human thyroid-carcinoma samples. RARbeta mRNA was reduced in FTC-238 cells and RXRbeta mRNA was decreased in anaplastic C643 cells and 9 of 12 tumor samples. Differential RA regulation of RA-receptor-mRNA expression was observed in the various cell lines. Thus, RA and T3 nuclear receptors are present in thyroid-carcinoma cell lines or tissues, albeit with cell-line and tumor-dependent variations; in the cell lines, they were shown to be functional with respect to DNA and/or ligand binding.
由于甲状腺特异性功能丧失而不再适用于放射性碘或促甲状腺激素抑制性T4治疗的甲状腺癌，可能会通过视黄酸（RA）充分重新分化，从而再次采用传统方法进行治疗。为了评估RA再分化疗法在甲状腺癌中的可行性，我们以人甲状腺癌细胞系作为模型系统，检测了RA信号传导的核心介质——RA受体（RARs/RXRs）的功能。对滤泡状甲状腺癌细胞系FTC-133和-238的核提取物进行的[3H]-RA结合试验显示，存在RA的高亲和力结合位点。使用DR2（“直接重复”2）RA反应元件进行的电泳迁移率变动和超迁移试验表明，FTC-133和间变性HTh74细胞核提取物中的RARα、RARγ、RXRα和RXRβ与DNA结合。使用DR5 RA反应元件未发现DNA结合有差异。在使用DR4 T3反应元件的超迁移试验中，我们发现TRα1、TRα2和TRβ与DNA结合。Northern印迹分析显示，FTC-133中RXRβ mRNA表达较低，FTC-133和FTC-238细胞中TRα1 mRNA表达较低。使用RT-PCR，我们在4种细胞系和人甲状腺癌样本中检测到了RARα、RARβ、RARγ、RXRα和RXRβ的mRNA。FTC-238细胞中RARβ mRNA减少，间变性C643细胞和12个肿瘤样本中的9个样本中RXRβ mRNA减少。在各种细胞系中观察到RA对RA受体mRNA表达的差异调节。因此，RA和T3核受体存在于甲状腺癌细胞系或组织中，尽管存在细胞系和肿瘤依赖性差异；在细胞系中，它们在DNA和/或配体结合方面具有功能。
