Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 7, 2014; 20(29): 10050-10061
Published online Aug 7, 2014. doi: 10.3748/wjg.v20.i29.10050
IGF2 differentially methylated region hypomethylation in relation to pathological and molecular features of serrated lesions
Takafumi Naito, Katsuhiko Nosho, Miki Ito, Hisayoshi Igarashi, Kei Mitsuhashi, Shinji Yoshii, Hironori Aoki, Masafumi Nomura, Yasutaka Sukawa, Eiichiro Yamamoto, Yasushi Adachi, Hiroaki Takahashi, Masao Hosokawa, Masahiro Fujita, Toshinao Takenouchi, Reo Maruyama, Hiromu Suzuki, Yoshifumi Baba, Kohzoh Imai, Hiroyuki Yamamoto, Shuji Ogino, Yasuhisa Shinomura
Takafumi Naito, Katsuhiko Nosho, Miki Ito, Hisayoshi Igarashi, Kei Mitsuhashi, Eiichiro Yamamoto, Yasushi Adachi, Yasuhisa Shinomura, Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University School of Medicine, Sapporo 060-8543, Japan
Shinji Yoshii, Hiroaki Takahashi, Department of Gastroenterology, Keiyukai Sapporo Hospital, Sapporo 003-0027, Japan
Hironori Aoki, Masafumi Nomura, Center for Gastroenterology, Teine-Keijinkai Hospital, Sapporo 006-0811, Japan
Yasutaka Sukawa, Shuji Ogino, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, United States
Masao Hosokawa, Department of Surgery, Keiyukai Sapporo Hospital, Sapporo 003-0027, Japan
Masahiro Fujita, Toshinao Takenouchi, Department of Pathology, Keiyukai Sapporo Hospital, Sapporo 003-0027, Japan
Reo Maruyama, Hiromu Suzuki, Department of Molecular Biology, Sapporo Medical University School of Medicine, Sapporo 060-8543, Japan
Yoshifumi Baba, Department of Gastroenterological Surgery, Graduate School of Medical Science, Kumamoto University, Kumamoto 860-0862, Japan
Kohzoh Imai, Division of Cancer Research, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
Hiroyuki Yamamoto, Division of Gastroenterology and Hepatology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan
Author contributions: Naito T and Nosho K designed the research, analyzed the data and wrote the manuscript; Sukawa Y, Adachi Y, Yamamoto E, Maruyama R and Suzuki H analyzed the data; Naito T, Ito M, Igarashi H and Mitsuhashi K performed experiments; Yoshii S, Aoki H, Nomura M, Takahashi H, Hosokawa M, Fujita M and Takenouchi T provided the collection of the human material and analyzed the data; Baba Y, Imai K, Yamamoto H, Ogino S and Shinomura Y edited the manuscript; Nosho K and Ogino S helped interpretation and drafting of this manuscript.
Supported by The Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research, grant No. 23790800 (to Nosho K) and 23390200 (to Shinomura Y); A-STEP (Adaptable and Seamless Technology Transfer Program through Target-driven R and D) (to Nosho K); Daiwa Securities Health Foundation (to Nosho K); Kobayashi Foundation for Cancer Research (to Nosho K); Sagawa Foundation for Promotion of Cancer Research (to Nosho K); Suzuken Memorial Foundation (to Nosho K), and Takeda Science Foundation (to Nosho K); and USA National Institute of Health, grant number R01 CA151993 (to Ogino S)
Correspondence to: Katsuhiko Nosho, MD, PhD, Department of Gastroenterology, Rheumatology and Clinical Immunology, Sapporo Medical University School of Medicine, S-1, W-16, Chou-ku, Sapporo 060-8543, Japan. nosho@sapmed.ac.jp
Telephone: +81-11-6112111 Fax: +81-11-6112282
Received: January 11, 2014
Revised: March 1, 2014
Accepted: April 21, 2014
Published online: August 7, 2014
Abstract

AIM: To investigate insulin-like growth factor 2 (IGF2) differentially methylated region (DMR)0 hypomethylation in relation to clinicopathological and molecular features in colorectal serrated lesions.

METHODS: To accurately analyze the association between the histological types and molecular features of each type of serrated lesion, we consecutively collected 1386 formalin-fixed paraffin-embedded tissue specimens that comprised all histological types [hyperplastic polyps (HPs, n = 121), sessile serrated adenomas (SSAs, n = 132), traditional serrated adenomas (TSAs, n = 111), non-serrated adenomas (n = 195), and colorectal cancers (CRCs, n = 827)]. We evaluated the methylation levels of IGF2 DMR0 and long interspersed nucleotide element-1 (LINE-1) in HPs (n = 115), SSAs (n = 120), SSAs with cytological dysplasia (n = 10), TSAs (n = 91), TSAs with high-grade dysplasia (HGD) (n = 15), non-serrated adenomas (n = 80), non-serrated adenomas with HGD (n = 105), and CRCs (n = 794). For the accurate quantification of the relative methylation levels (scale 0%-100%) of IGF2 DMR0 and LINE-1, we used bisulfite pyrosequencing method. Tumor specimens were analyzed for microsatellite instability, KRAS (codons 12 and 13), BRAF (V600E), and PIK3CA (exons 9 and 20) mutations; MLH1 and MGMT methylation; and IGF2 expression by immunohistochemistry.

RESULTS: The distribution of the IGF2 DMR0 methylation level in 351 serrated lesions and 185 non-serrated adenomas (with or without HGD) was as follows: mean 61.7, median 62.5, SD 18.0, range 5.0-99.0, interquartile range 49.5-74.4. The IGF2 DMR0 methylation level was divided into quartiles (Q1 ≥ 74.5, Q2 62.6-74.4, Q3 49.6-62.5, Q4 ≤ 49.5) for further analysis. With regard to the histological type, the IGF2 DMR0 methylation levels of SSAs (mean ± SD, 73.1 ± 12.3) were significantly higher than those of HPs (61.9 ± 20.5), TSAs (61.6 ± 19.6), and non-serrated adenomas (59.0 ± 15.8) (P < 0.0001). The IGF2 DMR0 methylation level was inversely correlated with the IGF2 expression level (r = -0.21, P = 0.0051). IGF2 DMR0 hypomethylation was less frequently detected in SSAs compared with HPs, TSAs, and non-serrated adenomas (P < 0.0001). Multivariate logistic regression analysis also showed that IGF2 DMR0 hypomethylation was inversely associated with SSAs (P < 0.0001). The methylation levels of IGF2 DMR0 and LINE-1 in TSAs with HGD (50.2 ± 18.7 and 55.7 ± 5.4, respectively) were significantly lower than those in TSAs (61.6 ± 19.6 and 58.8 ± 4.7, respectively) (IGF2 DMR0, P = 0.038; LINE-1, P = 0.024).

CONCLUSION: IGF2 DMR0 hypomethylation may be an infrequent epigenetic alteration in the SSA pathway. Hypomethylation of IGF2 DMR0 and LINE-1 may play a role in TSA pathway progression.

Keywords: BRAF, Colon polyp, Colorectal neoplasia, Colorectum, Genome, Insulin-like growth factor, Long interspersed nucleotide element-1, Microsatellite instability, Serrated pathway

Core tip: The serrated pathway attracts considerable attention as an alternative colorectal cancer (CRC) pathway. We previously reported the association of insulin-like growth factor 2 (IGF2) differentially methylated region (DMR)0 hypomethylation with prognosis and its link to LINE-1 hypomethylation in CRC; however, there have been no studies describing its role in the serrated pathway. Therefore, we evaluated the methylation levels of IGF2 DMR0 and long interspersed nucleotide element-1 (LINE-1) in 351 serrated lesions and 185 non-serrated adenomas. Our results suggest that the IGF2 DMR0 may be an infrequent epigenetic alteration in the sessile serrated adenoma pathway. Moreover, we found that the hypomethylation of IGF2 DMR0 and LINE-1 may play an important role in the progression of traditional serrated adenoma.