The Development of novel therapeutic strategy for anaplastic thyroid carcinoma by manipulating the ubiquitin-proteasome activity

甲状腺未分化癌是一种发生于老年人的低分化癌。未分化癌患者预后差。因此，研究有效的治疗策略，抑制未分化癌的生长，延长患者的预后，已成为当务之急。我们专注于泛素-蛋白酶体系统。蛋白酶体是一种主要的细胞内蛋白酶，它是由至少14个不同但同源的亚基组成的大蛋白复合物，分子量为21-32 kD，它们组装成约700 kDa的圆柱形结构。它参与破坏负责生物过程如细胞周期进程的调节蛋白。我们分析了蛋白酶体亚单位在甲状腺未分化癌中的表达，发现蛋白酶体亚单位C2和蛋白酶体激活剂g（PA 28 g）在其快速生长的癌细胞中高表达。这一结果被western blotting和imm反复证实 ...更多信息 当其他类型的甲状腺癌也估计。有趣的是，PA 28 g定位于癌细胞的细胞核中，这表明PA 28 g可能是操纵癌细胞生长的良好候选物之一。然后，我们使用大鼠功能性甲状腺细胞系FRTL 5细胞分析了PA 28 g的详细周转。促生长剂TSH和胰岛素可诱导FRTL 5细胞表达PA 28-γ。有趣的是，两种处理不仅上调PA 28-γ的表达，而且还将PA 28-γ从胞浆募集到细胞核。TSH和胰岛素的组合显示出最高的PA 28-γ的诱导以及FRTL 5的双DNA合成。蛋白酶体抑制剂如lactacystin可显著阻断TSH和胰岛素诱导的DNA合成，表明内源性20 S蛋白酶体参与甲状腺细胞生长。因此，我们的研究结果表明，PA 28-γ在甲状腺细胞中受促甲状腺肿因子TSH和胰岛素的诱导，并可能通过增强20 S蛋白酶体活性而促进甲状腺细胞的生长，因此，过表达的蛋白酶体组分如C2或PA 28-γ将是操纵蛋白酶体活性从而干扰间变性癌细胞生长的良好候选者。少

Anaplastic thyroid carcinoma is a poorly differentiated carcinoma found in elderly people. The patients with anaplastic carcinoma always suffer from poor prognosis. It is an urgent business to develop the effective strategy to suppress the growth of anaplastic carcinoma and prolong the prognosis of patients. We focused on the ubiqitin-proteasome system. Proteasome is a major intracellular proteinase found as a large protein complex composed of at least 14 distinct but homologous subunits with molecular masses of 21-32 kD and they are assembled into an approximately 700 kDa cylindcal structure. It is involved in the destruction of regulatory proteins responsible for biological processes such as cell cycle progression. We analyzed the expression of proteasome subunits in anaplastic thyroid carcinoma and found that proteasome subunit C2 and proteasome activator g (PA28g) are highly expressed in its rapid-growing cancer cells. This result is repeatedly confirmed by western blotting and imm … More unocytochemistry, when other types of thyroid carcinoma were also estimated. Interestingly, PA 28g is localized in nuclei of cancer cells, suggesting PA28g could be one of the good candidate for manipulating the growth of cancer cells. We then analyzed the detailed turn-over of PA28g using rat functional thyroid cell line, FRTL5 cells. The growth-stimuli, TSH and insulin, induced PA28-γ expression in FRTL5 cell. Intere stingly, both treatment not only upregulate PA28-γ expression but also recruite PA28-γ from cytosol to nucleus. The combination of TSH and insulin showed highest inducibility of PA28-γ as well as dual DNA synthesis of FRTL5. Proteasome inhibitors such as lactacystin significantly blocked the DNA synthesis induced by TSH and insulin, indicating the intrinsic 20S proteasome is involved in thyroid cell growth. Thus, our results indicate PA28-γ is induced by goitrogenic factors, TSH and insulin, in thyroid cell and potentially contribute to thyroid cell growth by potentiating 20S proteasome activity.Taken together, overexpressed proteasome component such as C2 or PA28-γ will be good candidates for manipulating proteasome activity, thereby interfering with anaplastic cancer cell growth. Less