Elucidation of the genesis mechanism of early lesions of colon cancer-Toward the elucidation of early lesions of de novo colorectal ceancer in humans

ACF-D（I）是典型ACF的一种异型增生性病变。ACF-D（II）由与正常隐窝相同或小于正常隐窝的隐窝、检测到的粘蛋白损失、高度发育异常病变组成，并且难以通过经典染色方法检测，但可以通过差异染色方法检测（Ochiai等人，Cancer Lett，220：67-74，2005）。本研究拟利用啮齿类动物结肠癌模型，阐明ACF-D（II）的发生机制，探讨ACF-D（II）是否可能是原发性结肠癌的早期病变及其特征。这在以下几点中使用由氧化偶氮甲烷诱导的大鼠结肠损伤进行分析。ACF-D（II）发生机制的基因特异性免疫组化分析在所有5例伴有粘蛋白丢失的ACF-D（II）中，结肠粘液的主要成分Muc 2蛋白丢失，但胃粘液的主要成分Muc 5AC蛋白异位表达未检测到。在ACF-D（II）中，Cdx 2蛋白的表达与正常腺泡和ACF-D（I）基本相同，Cdx 2通过Muc 2启动子激活Muc 2基因的表达。Runx 3是TGF-β超家族的靶基因，推测是一种抑癌基因。在5个ACF-D（I）中未检测到Runx 3蛋白的缺失，但在所有4个ACF-D（II）中检测到。提示Runx 3蛋白的丢失在ACF-D（II）中频繁发生，而在ACF-D（I）中不发生。此外，将验证Runx 3蛋白的缺失是否在ACF-D（II）中是特异性的。应用微阵列CGH技术对ACF-D（II）基因组发生机制的综合分析在3例结肠癌中均未检测到多探针连续缺失的拷贝数畸变（CNA）。因此，估计在结肠癌前病变ACF-D（II）中可能检测不到CNA。

ACF-D(I) is a dysplastic lesion which belongs to classical ACF. ACF-D(II) is composed of crypts the as same as or smaller than normal crypts, detected mucin loss, high grade dysplastic lesions, and is hard to detect by classical staining methods but can be detected by a differential staining method (Ochiai et al., Cancer Lett, 220:67-74, 2005). Using a colon cancer model in rodents, I propose that the genesis mechanism of ACF-D(II) be made clear, and study whether ACF-D(II) may be an early lesion of de novo colorectal cancer and the character of that be elucidated. This was analyzed in the points below using colonic lesions of rats induced by azoxymethane.1. Gene-specific analysis of the genesis mechanism of ACF-D(II) using immunohistochemical analysis.In all five ACF-D(II) with mucin loss, Muc2 protein, which is major component of mucus in colon, was lost but dystopic expression of Muc5AC protein, which is a major component of mucus in the stomach, was not detected. In ACF-D(II), the expression of Cdx2 protein, which activated gene expression of Muc2 through Muc2 promoter, was almost the same as those in normal crypts and ACF-D(I).Runx3 is the target of the TGF-β superfamily and a putative tumor suppressor gene. Loss of Runx3 protein was not detected in five ACF-D(I), but detected in all four ACF-D(II). It was suggested that loss of Runx3 protein frequently occurred in ACF-D(II) but not ACF-D(I). Furthermore, it will be verified whether loss of Runx3 protein is specific in ACF-D(II) or not.2. Comprehensive analysis in genome of the genesis mechanism of ACF-D(II) using array-CGHIn three colon cancers, copy number aberration (CNA) with continuous loss of plural probes was not detected. So it was estimated that CNA may not be detected in ACF-D(II), pre-cancerous lesions in colon.