Abstract 4438: MiRNA expression analysis in the tumor stroma predicts Tenascin C to promote colorectal cancer liver metastasis

Abstract

Abstract Background: Liver is the most common site for colorectal cancer (CRC) metastasis, and mechanisms underlying colorectal liver metastasis need to be explored. The tumor microenvironment consists of many stromal cells which are known to interact with cancer cells and to promote metastasis. Recently many microRNAs (miRNAs) specifically expressed in the stroma is receiving attention. In this study, we analyzed the differences in miRNA expression profiles between peritumoral stroma of CRCs with and without liver metastasis, and sought to identify liver metastasis-promoting molecules that can be regulated by the altered expression of miRNAs in the peritumoral stroma. Materials and methods: The formalin-fixed paraffin-embedded (FFPE) specimens of primary CRCs from 8 patients without metastasis, 4 patients with synchronous liver metastasis and 4 patients with metachronous liver metastasis were used for miRNA array analysis. None of the patients had received any treatment prior to surgery. Tumor stroma was isolated from FFPE samples using laser capture microdissection without contamination of cancer cells, and total RNAs were extracted. The quality of total RNA was assessed, and miRNA expression was analyzed using TaqMan miRNA arrays. Protein expression of Tenascin C (TNC) was immunohistochemically analyzed in 139 primary CRCs. Results: Unsupervised hierarchical clustering classified 16 samples analyzed into two groups according to their miRNA expressions. CRCs with synchronous liver metastasis showed differential miRNA expression profiles from those without liver metastasis or with metachronous liver metastasis. Top10 miRNAs up-regulated in CRCs with synchronous liver metastasis vs. CRCs without liver metastasis or with metachronous liver metastasis were hsa-miR-518b, 618, 186, 520f, 29c, 520e, 155, 30c, 518e and 106b, and those down-regulated in CRCs with synchronous liver metastasis were hsa-miR-302a, 551b, 627, 628-5p, 19a, 372, 302b, 384, 198 and 636. The predictive targets of the top 10 down-regulated miRNAs were analyzed in silico using on-line data base such as .miRDB. TNC was identified as a candidate for metastasis-promoting molecule which can be upregulated in the peritumoral stroma followed by the downregulation of miRNAs. Immunohistochemical analysis revealed that protein expression of TNC was higher in the stroma of primary CRCs with synchronous liver metastasis compared with those without liver metastasis or with metachronous liver metastasis. Furthermore, high expression of TNC protein in the primary CRC stroma was correlated with shorter overall survival and liver metastasis-free survival. Conclusions: Alterations of miRNAs in the CRC stroma appear to create a metastasis permissive environment in which TNC plays an important role. Expression of TNC in primary CRC stroma has the potential to be a novel biomarker to predict the risk of postoperative liver metastasis in CRC patients. Citation Format: Tomohiro Murakami, Hisahito Ishimatsu, Hirotoshi Kikuchi, Amane Hirotsu, Tomohiro Matsumoto, Yusuke Ozaki, Toshiki Kawabata, Yoshihiro Hiramatsu, Kinji Kamiya, Megumi Baba, Takanori Sakaguchi, Hiroyuki Konno. MiRNA expression analysis in the tumor stroma predicts Tenascin C to promote colorectal cancer liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4438. doi:10.1158/1538-7445.AM2017-4438