Abstract 1061: Clinico-pathological significance of LINE-1 and ESR1 methylation levels in sporadic colorectal cancer
Authors: Noguchi Tomofumi , Toiyama Yuji , Mori Koichiro , Ide Shozo , Imaoka Hiroki , Fujikawa Hiroyuki , Hiro Junichiro , Saigusa Susumu , Kobayashi Minako , Ohi Masaki , Tanaka Koji , Inoue Yasuhiro , Mohri Yasuhiko , ishii kenichiro , Kusunoki Masato 
Published: August 2015

Abstract
Background: Epigenetic changes including the global DNA methylation and the site-specific CpG island promoter methylation have been proposed to play an important role in colorectal carcinogenesis. The long interspersed nucleotide element-1 (LINE-1) methylation is good indicator of global DNA methylation levels, which is known to be hypo methylation in sporadic colorectal cancer (CRC). The promoter region of estrogen receptor 1 (ESR1) has been shown to be highly methylated in CRC compared to normal colorectal mucosa, and to be methylated in normal colorectal mucosa in an age-dependent manner. However, clinico-pathological significance of LINE-1 and ESR1 methylation levels in CRC has not sufficiently been investigated.
Aim: The aim of this study was to investigate the association between LINE-1 and ESR1 methylation levels and clinico-pathological findings including with microsatellite instability (MSI), KRAS and BRAF mutations, and tumor-infiltrating lymphocytes (TILs) in CRC.
Materials and Methods: We quantified the LINE-1 and ESR1 methylation levels in CRC (n = 182), adjacent normal mucosa (AN) (n = 18), normal colon mucosa (N) (n = 18) using a bisulfite pyrosequencing analysis. MSI status was determined using five mononucleotide-repeat microsatellite markers. KRAS (exons 2 and 3) and BRAF (V600E) mutations were also analyzed by a bisulfite pyrosequencing. TILs were evaluated by counting numbers of intra-tumor Foxp3- and CD8-positive T cell by immunohistochemistry.
Results: LINE-1 methylation levels in CRC were significantly lower than in AN or N, respectively. Lower LINE-1 methylation levels were significantly correlated with differentiated cell types, microsatellite stable (MSS) and low TILs in CRC. However, no significant association between LINE-1 methylation levels and tumor progression including with prognostic outcome was recognized. On the other hand, ESR1 methylation levels in CRC were significantly higher than in AN or N, respectively. Higher methylation levels of ESR1 were significantly associated with MSS and KRAS mutation in CRC. Although ESR1 methylation levels were not associated with tumor progression in CRC, survival curves showed that CRC patients with low ESR1 methylation levels had significantly poorer overall survival and disease free survival than those with high methylation levels. Furthermore, ESR1 methylation levels were independent indicators for poor prognosis and early recurrence of CRC patients.
Conclusion: We demonstrated novel evidence of ESR1 methylation levels as promising biomarkers for prognosis and predictive recurrence in patients with CRC.
Citation Format: Tomofumi Noguchi, Yuji Toiyama, Koichiro Mori, Shozo Ide, Hiroki Imaoka, Hiroyuki Fujikawa, Junichiro Hiro, Susumu Saigusa, Minako Kobayashi, Masaki Ohi, Koji Tanaka, Yasuhiro Inoue, Yasuhiko Mohri, kenichiro ishii, Masato Kusunoki. Clinico-pathological significance of LINE-1 and ESR1 methylation levels in sporadic colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1061. doi:10.1158/1538-7445.AM2015-1061