A Study of Epigenetic Alteration of the Bone Morphogenetic Protein-2 Gene in Human Colorectal Cancer

PURPOSE: Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta family and play an important role in cellular growth. Recent reports suggest that exogenous bone morphogenetic protein-2 (BMP-2) acts as an antiproliferative agent in a variety of cell lines. We will study whether BMP-2 is altered in human colorectal cancer. METHODS: We analyzed 40 colorectal cancer cases and 6 colorectal cancer cell lines by using reverse transcription-polymerase chain reaction (RT-PCR) to determine the expression of BMP-2. RESULTS: Thirteen of 40 colorectal cancers (33%) and 3 of 6 colorectal cancer cell lines (50%) revealed decreased expression of BMP-2. The rates of decreased expression were 0% (0/7), 42.1% (8/19), 28.6% (2/7), 33.3% (2/6), and 100% (1/1) in stages I, II, III, and IV, respectively. Histologically, the rates were 33.3% (2/6), 32.2% (10/21), 50% (1/2), and 0% (0/1) in well-differentiated, moderately-differentiated, poorly-differentiated and mucinous cancers, respectively. As for location, the rates for colon and rectal cancers were 27.8% (5/18) and 36.4% (8/22), respectively. We identified methylation in the CpG island of the BMP-2 gene in 60% of colorectal cancer cells and in 50% of colorectal cancer cell lines. The 13 cases without BMP-2 gene expression showed no significant correlation with clinicopathological factors. Epigenetic silencing through DNA methylation is one of the key steps during carcinogenesis. CONCLUSION: We found, through an analysis using the methylation-specific polymerase chain reaction technique, CpG island methylation of the BMP-2 promoter region in colorectal cancer. Thus, aberrant BMP-2 methylation and the resultant loss of BMP-2 expression may be related to colorectal carcinogenesis.

Topographic expression of p21WAF1/SDI1/CIP1, bcl2, and p53 is altered at the early stage of colorectal carcinogenesis

We analyzed the expression of p21, bcl2, and p53 in normal and different pathologic mucosa of the human colorectum using immunohistochemistry and cold polymerase chain reaction-single strand conformation polymorphism. The topography of normal mucosa showed; bcl2 and p53 expression restricted to basal epithelial cells and p21 expressed only in superficial epithelial cells. This topographic expression was altered in hyperplastic polyps and adenomas. Hyperplastic polyps revealed absence of or weak bcl2 expression and strong p21 expression without topography. In adenomas, whereas bcl2 expression increased and extended to parabasal and superficial dysplastic epithelium, the increase of p21 expression was limited to surface dysplastic epithelium. p53 was weakly expressed throughout the full thickness of dysplastic epithelium. Bcl2 expression in adenomas was stronger than in carcinomas; p53 expression was converse and p21 expression was variable. In carcinomas, this topographic expression was largely abrogated but p53 mutation (36%) was more frequent than in adenomas (2%). In carcinomas, p21 and p53 expression correlated inversely, but there was no relationship with bcl2. These results suggest that there is precisely ordered topographic pattern of p21, bcl2, and wild p53 expression in normal colorectal cells, but this becomes disordered during the early stage of colorectal carcinogenesis.