• Taiki Hashimoto, Satoshi Yamashita, Hiroshi Yoshida, Hirokazu Taniguchi, Toshikazu Ushijima, Tesshi Yamada, Yutaka Saito, Atsushi Ochiai, Shigeki Sekine, and Nobuyoshi Hiraoka.
• *Division of Pathology and Clinical Laboratories ∥Endoscopy Division, National Cancer Center Hospital †Course of Advanced Clinical Research of Cancer, Juntendo University Graduate School of Medicine ‡Division of Epigenomics §Division of Chemotherapy and Clinical Research #Division of Molecular Pathology, National Cancer Center Research Institute, Tokyo ¶Division of Pathology, Research Center for Innovative Oncology, National Cancer Center, Chiba, Japan.
• Am. J. Surg. Pathol. 2017 Sep 1; 41 (9): 1188-1197.

AbstractSessile serrated adenoma/polyps (SSA/Ps) are believed to be the major precursor of serrated pathway-derived colorectal carcinomas. To better characterize the process of progression from SSA/Ps to carcinomas, we analyzed 46 SSA/Ps with dysplasia and 45 SSA/Ps without dysplasia using targeted next-generation sequencing and immunohistochemistry. Among the WNT pathway genes analyzed, protein-truncating mutations of RNF43, APC, and ZNRF3 were identified in 23 (50%), 4 (9%), and 3 (7%) SSA/Ps with dysplasia, respectively. In contrast, SSA/Ps without dysplasia rarely had WNT pathway gene mutations, except for 3 lesions with RNF43 mutations (7%). None of the SSA/Ps had CTNNB1 mutations or RSPO fusions. Thus, WNT pathway gene mutations were more common in SSA/Ps with dysplasia than in SSA/Ps without dysplasia (P=3.0×10). Consistently, nuclear β-catenin accumulation and MYC overexpression, indicative of active WNT signaling, were present in most of the SSA/Ps with dysplasia, but were rare in those without dysplasia. BRAF (86%) or KRAS mutations (7%) were identified in the majority of SSA/Ps, regardless of the presence or absence of dysplasia. MLH1 expression was lost in 14 SSA/Ps with dysplasia (30%). The majority of MLH1-deficient SSA/Ps with dysplasia had RNF43 mutations (86%), most of which were frameshift mutations involving mononucleotide repeats. In contrast, MLH1-retained lesions had less frequent RNF43 mutations with no hot spots (34%), and 4 had APC mutations (13%). These results suggest that WNT pathway gene mutations are involved in the development of dysplasia in SSA/Ps and that MLH1-deficient and MLH1-retained SSA/Ps with dysplasia exhibit distinct mutation profiles of WNT pathway genes.

18 keywords...

hide…