Department of Discovery Oncology, Department of Bioinformatics, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
Biochem J. 2013 Jun 1;452(2):313-20. doi: 10.1042/BJ20121578.
The mutant forms of KRas, NRas and HRas drive the initiation and progression of a number of human cancers, but less is known about the role of WT (wild-type) Ras alleles and isoforms in cancer. We used zinc-finger nucleases targeting HRas and NRas to modify both alleles of these genes in the mutant KRas-driven Hec1A endometrial cancer cell line, which normally expresses WT copies of these genes. The disruption of either WT isoform of Ras compromised growth-factor-dependent signalling through the ERK (extracellular-signal-regulated kinase) pathway. In addition, the disruption of HRas hindered the activation of Akt and subsequent downstream signalling. This was associated with decreased proliferation, increased apoptosis and decreased anchorage-independent growth in the HRas-disrupted cells. However, xenograft tumour growth was not significantly affected by the disruption of either NRas or HRas. As expected, deleting the mutant allele of KRas abolished tumour growth, whereas deletion of the remaining WT copy of KRas increased the tumorigenic properties of these cells; deleting a single copy of either HRas or NRas did not mimic this effect. The present study demonstrates that the WT copies of HRas, NRas and KRas play unique roles in the context of mutant KRas-driven tumours.
KRas、NRAS 和 HRas 的突变形式驱动着许多人类癌症的发生和发展，但关于 WT（野生型）Ras 等位基因和异构体在癌症中的作用知之甚少。我们使用锌指核酸酶靶向 HRas 和 NRas，在突变 KRas 驱动的 Hec1A 子宫内膜癌细胞系中修饰这些基因的两个等位基因，该细胞系通常表达这些基因的 WT 拷贝。Ras 的 WT 异构体的破坏削弱了通过 ERK（细胞外信号调节激酶）途径的生长因子依赖性信号转导。此外，HRas 的破坏阻碍了 Akt 的激活及其下游信号转导。这与 HRas 破坏细胞中的增殖减少、凋亡增加和锚定独立生长减少有关。然而，敲除 NRas 或 HRas 并不显著影响异种移植肿瘤的生长。正如预期的那样，敲除 KRas 的突变等位基因可消除肿瘤生长，而敲除剩余的 KRas WT 拷贝可增加这些细胞的致瘤特性；敲除 HRas 或 NRas 的单个拷贝并不能模拟这种效应。本研究表明，在突变 KRas 驱动的肿瘤背景下，HRas、NRAS 和 KRas 的 WT 拷贝发挥着独特的作用。
