Department of Medicine, Division of Oncology, School of Medicine, Center for Clinical Sciences Research, Stanford University, Stanford, California 94305-5151, USA.
Mol Ther. 2010 Jan;18(1):161-70. doi: 10.1038/mt.2009.222. Epub 2009 Oct 20.
Short hairpin RNAs (shRNAs) have emerged as a novel therapeutic modality, but there is increasing concern over nonspecific effects in vivo. Here, we used viral vectors to express shRNAs against endogenous p53 in livers of conditional MYC-transgenic mice. As expected, the shRNAs silenced hepatic p53 and accelerated liver tumorigenesis when MYC was concurrently expressed. Surprisingly, various irrelevant control shRNAs similarly induced a rapid onset of tumorigenesis, comparable to carbon tetrachloride (CCl4), a potent carcinogen. We found that even marginal shRNA doses can already trigger histologically detectable hepatoxicity and increased hepatocyte apoptosis. Moreover, we noted that shRNA expression globally dysregulated hepatic microRNA (miRNA) expression, and that shRNA levels and activity further increased in the presence of MYC. In MYC-expressing transgenic mice, the marginal shRNA-induced liver injury sufficed to further stimulate hepatocellular division that was in turn associated with markedly increased expression of the mitotic cyclin B1. Hence, even at low doses, shRNAs can cause low-level hepatoxicity that can facilitate the ability of the MYC oncogene to induce liver tumorigenesis. Our data warrant caution regarding the possible carcinogenic potential of shRNAs when used as clinical agent, particularly in circumstances where tissues are genetically predisposed to cellular transformation and proliferation.
短发夹 RNA（shRNAs）已成为一种新的治疗模式，但人们越来越担心其在体内的非特异性作用。在这里，我们使用病毒载体在条件性 MYC 转基因小鼠的肝脏中表达针对内源性 p53 的 shRNAs。正如预期的那样，当同时表达 MYC 时，shRNAs 沉默了肝 p53 并加速了肝肿瘤的发生。令人惊讶的是，各种不相关的对照 shRNAs 也同样诱导了肿瘤发生的快速发作，与强效致癌剂四氯化碳（CCl4）相当。我们发现，即使是微小的 shRNA 剂量也可以引发组织学上可检测的肝毒性和增加的肝细胞凋亡。此外，我们注意到 shRNA 表达全局失调了肝 microRNA（miRNA）的表达，并且在存在 MYC 的情况下，shRNA 水平和活性进一步增加。在表达 MYC 的转基因小鼠中，微小的 shRNA 诱导的肝损伤足以进一步刺激肝细胞分裂，这反过来又与有丝分裂周期蛋白 B1 的表达显著增加有关。因此，即使在低剂量下，shRNAs 也可能导致低水平的肝毒性，从而增强 MYC 癌基因诱导肝肿瘤发生的能力。我们的数据提醒人们注意 shRNAs 作为临床制剂时可能存在的致癌潜力，特别是在组织容易发生细胞转化和增殖的情况下。
