Surface microstructures are associated with mutational intratumoral heterogeneity in colorectal tumors
Recent studies revealed that colorectal tumors are composed of genetically diverse subclones. We aimed to clarify whether the surface microstructures of colorectal tumors are associated with genetic intratumoral heterogeneity (ITH).
The surface microstructures (pit patterns) of colorectal tumors were observed using magnifying endoscopy, and biopsy specimens were obtained from respective areas when tumors exhibited multiple pit patterns. A total of 711 specimens from 477 colorectal tumors were analyzed for BRAF, KRAS and TP53 mutations using pyrosequencing and direct sequencing. A panel of cancer-related genes was analyzed through targeted sequencing in 7 tumors.
Colorectal tumors with multiple pit patterns exhibited more advanced pit patterns and higher frequencies of KRAS and/or TP53 mutations than tumors with a single pit pattern. In tumors with multiple pit patterns, mutations were observed as public (common to all areas) or private (specific to certain areas), and private KRAS and/or TP53 mutations were often variable and unrelated to the pit pattern grade. Notably, invasive CRCs frequently exhibited public TP53 mutations, even in adenomatous areas, which is indicative of their early malignant potential. Targeted sequencing revealed additional public and private mutations in tumors with multiple pit patterns, indicating their single clonal origin.
Our results suggest intratumoral pit pattern variation does not simply reflect the process of colorectal tumor evolution, but instead represents genetically diverse subclones, and this diversity may be associated with malignant potential.
KeywordsColorectal tumor Magnifying endoscopy Pit pattern Mutation Intratumoral heterogeneity
The authors thank Dr. William F. Goldman for editing the manuscript and Ms. Mutsumi Toyota, Ms. Tomo Hatahira and Ms. Tokiko Ito for technical assistance.
This study was supported in part by Grant-in-Aid for Scientific Research (C) from the Japan Society for Promotion of Science (JSPS KAKENHI 15K08973, E. Yamamoto), Grant-in-Aid for Scientific Research (B) from the Japan Society for Promotion of Science (JSPS KAKENHI 15H04299, H. Suzuki), Grants-in-Aid for Young Investigators (B) from Japan Society for Promotion of Science (JSPS KAKENHI 15K18431, T. Harada; JSPS KAKENHI 15K19339, H. Aoki), JFE (The Japanese Foundation for Research and Promotion of Endoscopy) Grant (E. Yamamoto), The Takeda Science Foundation (E. Yamamoto) and Suhara Memorial Foundation (E. Yamamoto).
Compliance with ethical standards
Conflict of interest
All authors have no conflict of interest to declare.
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