The Ras effector RASSF2 is a novel tumor-suppressor gene in human colorectal cancer
The Ras effector RASSF2 is a novel tumor-suppressor gene in human colorectal cancer
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DOI：
10.1053/j.gastro.2005.03.051
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发表时间：
2005-07-01
期刊：
影响因子：
29.4
通讯作者：
Tokino, T
中科院分区：
文献类型：
--
作者：
Akino, K;Toyota, M;Tokino, T
背景与目的：Ras信号的激活是结直肠癌（CRC）的标志，但Ras负调节因子的作用尚不完全清楚。我们的目的是通过研究结直肠癌细胞中Ras-Ras效应基因的遗传和表观遗传改变来解决这个问题。方法：采用RT-PCR和亚硫酸根聚合酶链反应（亚硫酸根聚合酶链反应）检测6个RASSF家族基因在结直肠癌细胞系、原发性结直肠癌和结直肠癌腺瘤中的表达和甲基化状态。采用集落形成法和流式细胞术评估RASSF1和RASSF2的抑瘤活性。免疫荧光显微镜检测RASSF2表达改变对细胞形态的影响。通过单链构象分析和直接测序鉴定K-ras、BRAF和p53突变。结果：RASSF2的异常甲基化和组蛋白去乙酰化与该基因在结直肠癌中的沉默有关。与RASSF1不同，RASSF2的活性包括诱导细胞形态变化和凋亡；此外，其阻止细胞转化的能力表明RASSF2在结直肠癌中起肿瘤抑制作用。显示K-ras/BRAF突变的原发性crc也经常显示RASSF2甲基化，RASSF2的失活增强了K-ras诱导的致癌转化。在结直肠腺瘤中也经常发现RASSF2甲基化。结论：RASSF2是一种新的肿瘤抑制基因，可调控Ras信号，在结直肠肿瘤发生的早期阶段发挥关键作用。
Background & Aims: Activation of Ras signaling is a hallmark of colorectal cancer (CRC), but the roles of negative regulators of Ras are not fully understood. Our aim was to address that question by surveying genetic and epigenetic alterations of Ras-Ras effector genes in CRC cells. Methods: The expression and methylation status of 6 RASSF family genes were examined using RT-PCR and bisulfite PCR in CRC cell lines and in primary CRCs and colorectal adenomas. Colony formation assays and flow cytometry were used to assess the tumor suppressor activities of RASSF1 and RASSF2. Immunofluorescence microscopy was used to determine the effect of altered RASSF2 expression on cell morphology. Mutations of K-ras, BRAF, and p53 were identified using single-strand conformation analysis and direct sequencing. Result : Aberrant methylation and histone deacetylation of RASSF2 was associated with the gene's silencing in CRC. The activities of RASSF2, which were distinct from those of RASSF1, included induction of morphologic changes and apoptosis; moreover, its ability to prevent cell transformation suggests that RASSF2 acts as a tumor suppressor in CRC. Primary CRCs that showed K-ras/BRAF mutations also frequently showed RASSF2 methylation, and inactivation of RASSF2 enhanced K-ras-induced oncogenic transformation. RASSF2 methylation was also frequently identified in colorectal adenomas. Conclusions: RASSF2 is a novel tumor suppressor gene that regulates Ras signaling and plays a pivotal role in the early stages of colorectal tumorigenesis.