Section of Endocrinology and Metabolism, Department of Internal Medicine, Endocrinology, and Metabolism and Biochemistry, Policlinico Santa Maria alle Scotte, Viale Bracci 1, University of Siena, 53100 Siena, Italy.
J Clin Endocrinol Metab. 2012 Nov;97(11):4253-9. doi: 10.1210/jc.2012-2360. Epub 2012 Sep 4.
In thyroid cells, binding of TSH to its receptor increases cAMP levels, sustaining thyrocytes growth and hormone production. The main cAMP effector enzyme is protein kinase A (PKA). Praja2 is a widely expressed RING (Really Interesting New Gene) ligase, which degrades the regulatory subunits of PKA, thus controlling the strength and duration of PKA signaling in response to cAMP. Differentiated thyroid cancer expresses a functional TSH receptor, and its growth and progression are positively regulated by TSH and cAMP signaling.
We aimed to analyze the expression of praja2 in a group of 36 papillary thyroid cancer (PTC), 14 benign nodules, and six anaplastic thyroid cancers (ATC).
We measured praja2 mRNA levels by quantitative RT-PCR and praja2 expression by Western blot and immunohistochemistry. Possible association between praja2 mRNA and the presence of known mutations was evaluated.
We found a statistical significant increase of mRNA levels in PTC tissue samples, compared with benign nodules and ATC. In particular, mRNA levels were maximal in differentiated thyroid cancer (PTC), progressively decreasing in more aggressive tumors, ATC having the lowest amount of praja2 mRNA. Accordingly, higher levels of praja2 protein were detected in lysates from PTC, compared with ATC. By immunohistochemistry, in PTC sections we observed a marked increase of cytoplasmic praja2 signal, which significantly decreased in less differentiated thyroid tumors, completely disappearing in ATC. Studies in cultured cells stably expressing RET/PTC1 oncogene or mutant BRAF revealed a direct correlation between praja2 mRNA levels and malignant phenotype of transformed cells. Similar results were obtained using thyroid cancer tissues carrying the same mutations.
praja2 is markedly overexpressed in differentiated thyroid cancer, and its levels inversely correlate with the malignant phenotype of the tumor. Thus, praja2 is a novel cancer-related gene whose expression is linked to the histotype and mutational status of the thyroid tumor.
在甲状腺细胞中，促甲状腺激素（TSH）与其受体结合会增加环腺苷酸（cAMP）水平，从而维持甲状腺细胞的生长和激素产生。cAMP 的主要效应酶是蛋白激酶 A（PKA）。Praja2 是一种广泛表达的 RING（真的很有趣的新基因）连接酶，它可以降解 PKA 的调节亚基，从而控制 PKA 信号的强度和持续时间，以响应 cAMP。分化型甲状腺癌表达功能性 TSH 受体，其生长和进展受 TSH 和 cAMP 信号的正向调节。
我们旨在分析 36 例甲状腺乳头状癌（PTC）、14 例良性结节和 6 例间变性甲状腺癌（ATC）组织中 praja2 的表达。
通过实时定量 RT-PCR 测定 praja2 mRNA 水平，通过 Western blot 和免疫组织化学测定 praja2 表达。评估 praja2 mRNA 与已知突变存在之间的可能关联。
与良性结节和 ATC 相比，我们发现 PTC 组织样本中的 mRNA 水平有统计学显著增加。特别是，在分化型甲状腺癌（PTC）中，mRNA 水平最高，在侵袭性更强的肿瘤中逐渐降低，ATC 中的 praja2 mRNA 含量最低。相应地，与 ATC 相比，PTC 细胞裂解物中检测到更高水平的 praja2 蛋白。通过免疫组织化学，我们在 PTC 切片中观察到细胞质 praja2 信号明显增加，在分化程度较低的甲状腺肿瘤中显著降低，在 ATC 中完全消失。在稳定表达 RET/PTC1 癌基因或突变 BRAF 的培养细胞中进行的研究表明，praja2 mRNA 水平与转化细胞的恶性表型之间存在直接相关性。使用携带相同突变的甲状腺癌组织进行的类似研究也得到了相似的结果。
praja2 在分化型甲状腺癌中明显过表达，其水平与肿瘤的恶性表型呈负相关。因此，praja2 是一种新的癌相关基因，其表达与甲状腺肿瘤的组织类型和突变状态相关。
