Thoracic Oncology Laboratory, Department of Surgery, Comprehensive Cancer Center, University of California, San Francisco, CA 94115, USA.
J Cell Mol Med. 2011 Feb;15(2):350-8. doi: 10.1111/j.1582-4934.2009.00971.x.
Cullin 4A (Cul4A) is important in cell survival, development, growth and the cell cycle, but its role in mesothelioma has not been studied. For the first time, we identified amplification of the Cul4A gene in four of five mesothelioma cell lines. Consistent with increased Cul4A gene copy number, we found that Cul4A protein was overexpressed in mesothelioma cells as well. Cul4A protein was also overexpressed in 64% of primary malignant pleural mesothelioma (MPM) tumours. Furthermore, knockdown of Cul4A with shRNA in mesothelioma cells resulted in up-regulation of p21 and p27 tumour suppressor proteins in a p53-independent manner in H290, H28 and MS-1 mesothelioma cell lines. Knockdown of Cul4A also resulted in G0/G1 cell cycle arrest and decreased colony formation in H290, H28 and MS-1 mesothelioma cell lines. Moreover, G0/G1 cell cycle arrest was partially reversed by siRNA down-regulation of p21 and/or p27 in Cul4A knockdown H290 cell line. In the contrary, overexpression of Cul4A resulted in down-regulation of p21 and p27 proteins and increased colony formation in H28 mesothelioma cell line. Both p21 and p27 showed faster degradation rates in Cul4A overexpressed H28 cell line and slower degradation rates in Cul4A knockdown H28 cell line. Our study indicates that Cul4A amplification and overexpression play an oncogenic role in the pathogenesis of mesothelioma. Thus, Cul4A may be a potential therapeutic target for MPM.
Cullin 4A (Cul4A) 在细胞存活、发育、生长和细胞周期中都很重要，但它在间皮瘤中的作用尚未得到研究。我们首次发现，在五个间皮瘤细胞系中的四个中，Cul4A 基因发生了扩增。与 Cul4A 基因拷贝数增加一致，我们发现间皮瘤细胞中 Cul4A 蛋白也过表达。Cul4A 蛋白在 64%的原发性恶性胸膜间皮瘤 (MPM) 肿瘤中也过表达。此外，在 H290、H28 和 MS-1 间皮瘤细胞系中，用 shRNA 敲低 Cul4A 导致 p53 非依赖性上调 p21 和 p27 肿瘤抑制蛋白。Cul4A 的敲低还导致 H290、H28 和 MS-1 间皮瘤细胞系中的 G0/G1 细胞周期停滞和集落形成减少。此外，在 Cul4A 敲低的 H290 细胞系中，通过 siRNA 下调 p21 和/或 p27 部分逆转了 G0/G1 细胞周期停滞。相反，Cul4A 的过表达导致 p21 和 p27 蛋白下调和 H28 间皮瘤细胞系中集落形成增加。在 Cul4A 过表达的 H28 细胞系中，p21 和 p27 的降解速度更快，而在 Cul4A 敲低的 H28 细胞系中降解速度更慢。我们的研究表明，Cul4A 扩增和过表达在间皮瘤的发病机制中发挥致癌作用。因此，Cul4A 可能是 MPM 的潜在治疗靶点。
