[608] Molecular Features of Colorectal Hyperplastic Polyps from Korea

KM Kim, RD Odze. Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Brigham and Womens Hospital, Harvard Medical School, Boston

Background: Previous studies have shown specific lifestyle and dietary factors associated with an increased risk of development of hyperplastic polyps (HP). HP has also been shown to be related to the development of adenomas and colorectal carcinomas in some studies. Although studies of the molecular features of HP's have been performed in western countries, the molecular features of HP's in patients from the far east, such as Korea, which have a different lifestyle and diet, have never been performed.
Design: 112 HPs were retrieved from the surgical pathology files of Samsung Medical Center between 2004 and 2006 and classified as either microvesicular (MV) (n=89), goblet cell (GC) (n=13), mucin depleted (MD) (n=2), or indeterminate (Ind) (n=8) by 2 GI pathologists. In addition, 6 HP's associated with a serrated adenoma (SA) and 5 cases associated with intramucosal adenocarcinoma, were included. DNA from each case was evaluated for mutations of BRAF, and KRAS, and for methylation of hMLH1, MGMT, and APC.
Results: BRAF mutations were significantly more common in MV HP (63%) compared to the other subgroups (GC: 0%, others: 20%, p<0.001 for each comparison). In contrast, KRAS mutations were significantly more common in GC HP (77%) compared to all of the other polyp subgroups (p<0.001). The prevalence rate of hMLH1, MGMT, and APC methylation in HP's was 51.8%, 16.1%, and 38.4%, and there were no differences between the different HP subgroups. BRAF and KRAS mutations occurred in 83% and 17%, and hMLH1, MGMT, APC methylation occurred in 33%, 67% and 33% of SA's arising in HP. However, adenocarcinoma associated with HP showed no evidence of BRAF or KRAS mutations and hMLH1, MGMT, APC methylation occurred in 60%, 80% and 0% of cases.
Conclusions: In contrast to Western countries, both BRAF mutations and hMLH1 methylation are less frequent in HP from Korea. BRAF mutations are more common in GC HP, and MGMT methylation is more prevalent in MV HP. These results indicate that lifestyle and/or dietary factors may have a genetic and/or epigenetic influence on the development of HP's in different regions of the world.
Category: Gastrointestinal

Wednesday, March 11, 2009 9:30 AM

Poster Session V # 75, Wednesday Morning