Ogino Shuji, Kawasaki Takako, Ogawa Akiyo, Kirkner Gregory J, Loda Massimo, Fuchs Charles S
Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA.
Hum Pathol. 2007 Apr;38(4):614-20. doi: 10.1016/j.humpath.2006.10.005. Epub 2007 Jan 31.
The transforming growth factor-beta receptor type 2 gene (TGFBR2) is mutated in most microsatellite instability-high (MSI-H) colorectal cancers. Promoter methylation of RUNX3 (runt-related transcription factor 3; encoding a transcription factor downstream of the TGF-beta pathway) is observed in colorectal cancer with CpG island methylator phenotype (CIMP), which is characterized by extensive promoter methylation and is associated with MSI-H and BRAF mutations. However, no study to date has examined interrelationship between TGFBR2 mutation, RUNX3 methylation, and CIMP in colorectal cancer. Using 144 MSI-H colorectal cancers derived from 2 large prospective cohort studies, we analyzed a mononucleotide repeat of TGFBR2 and quantified DNA methylation (by MethyLight technology) in 8 CIMP-specific promoters (RUNX3, CACNA1G [calcium channel, voltage-dependent, T type alpha-1G subunit], CDKN2A [p16], CRABP1 [cellular retinoic acid binding protein 1], IGF2 [insulin-like growth factor 2], MLH1, NEUROG1 [neurogenin 1], and SOCS1 [suppressor of cytokine signaling 1]). Among the 144 MSI-H tumors, the presence of TGFBR2 mutation (overall 72% frequency) was correlated positively with CIMP-high (with >/=6/8 methylated promoters; P < .0001), RUNX3 methylation (P = .0004), BRAF mutation (P = .0006), and right colon (P = .05); inversely with KRAS mutation (P = .006); but not significantly with sex, tumor differentiation, and p53 status (assessed by immunohistochemistry). After stratification by sex, location, tumor differentiation, RUNX3 status, KRAS/BRAF status, or p53 status, CIMP-high was persistently correlated with TGFBR2 mutation. In contrast, RUNX3, KRAS, or BRAF status was no longer correlated with TGFBR2 mutation after stratification by CIMP status. In conclusion, TGFBR2 mutation is associated with CIMP-high and indirectly with RUNX3 methylation. Our findings emphasize the importance of analyzing global epigenomic status (for which CIMP status is a surrogate marker) when correlating a single epigenetic event (eg, RUNX3 methylation) with any other molecular or clinicopathologic variables.
在大多数微卫星高度不稳定（MSI-H）的结直肠癌中，转化生长因子β受体2型基因（TGFBR2）发生突变。在具有CpG岛甲基化表型（CIMP）的结直肠癌中观察到RUNX3（ runt相关转录因子3；编码TGF-β信号通路下游的一种转录因子）的启动子甲基化，CIMP的特征是广泛的启动子甲基化，且与MSI-H和BRAF突变相关。然而，迄今为止尚无研究探讨结直肠癌中TGFBR2突变、RUNX3甲基化和CIMP之间的相互关系。利用来自2项大型前瞻性队列研究的144例MSI-H结直肠癌，我们分析了TGFBR2的单核苷酸重复序列，并通过MethyLight技术对8个CIMP特异性启动子（RUNX3、CACNA1G [钙通道，电压依赖性，T型α-1G亚基]、CDKN2A [p16]、CRABP1 [细胞视黄酸结合蛋白1]、IGF2 [胰岛素样生长因子2]、MLH1、NEUROG1 [神经生成素1]和SOCS1 [细胞因子信号转导抑制因子1]）中的DNA甲基化进行了定量分析。在这144例MSI-H肿瘤中，TGFBR2突变的存在（总体频率为72%）与CIMP高（≥6/8个甲基化启动子；P <.0001）、RUNX3甲基化（P =.0004）、BRAF突变（P =.0006）和右半结肠（P =.05）呈正相关；与KRAS突变呈负相关（P =.006）；但与性别、肿瘤分化程度和p53状态（通过免疫组织化学评估）无显著相关性。按性别、部位、肿瘤分化程度、RUNX3状态、KRAS/BRAF状态或p53状态分层后，CIMP高仍与TGFBR2突变相关。相反，按CIMP状态分层后，RUNX3、KRAS或BRAF状态与TGFBR2突变不再相关。总之，TGFBR2突变与CIMP高相关，且与RUNX3甲基化间接相关。我们的研究结果强调了在将单个表观遗传事件（如RUNX3甲基化）与任何其他分子或临床病理变量相关联时，分析整体表观基因组状态（CIMP状态是其替代标志物）的重要性。
